Handbook of Polymer Synthesis Second Edition Episode 11 pptx

11
Metal-Containing Macromolecules
Dieter Wo
¨
hrle
University of Bremen, Bremen, Germany
I. FUNDAMENTALS ABOUT METAL-CONTAINING MACROMOLECULES
A. Classification
In metal-containing macromolecules or macromolecular metal complexes (MMC) (article
in the previous edition of the Handbook see [1]) suit able compounds are combined
to materials with new unusual properties: organic or inorganic macromolecules with
metal ions, complexes, chelates or also metal clusters. Thes e combinations result in new
materials with high activities and specific selectivities in different functions. This article
concentrates on synthetic aspects of artificial metal-containing macromolecules. Properties
are shortly mentioned, and one has to look for more details in the cited lite ratures. In order
to understand what kind of properties are realized in metal-containing macromolecules,
in a first view functions of comparable natural systems (a short overview is given below)
has to be considered:
 metallo-enzymes for catalysis,
 hemoglobin, myoglobin for gas transport,
 cofactors for electron-interaction,
 apparatus of photosynthesis for energy conversion,
 metallo-proteins and related systems for various functions.
For meta l-containing polymers it is important to understand also their molecular
arrangements: primary structure (composition of a MMC); secondary structure (steric
orientation of a MMC unit); tertiary structure (orientation of the whole MMC);
quarternary structure (interaction of different MMCs). The more detailed knowledge
about biological macromolecular metal complexes led in the recent years to an intensified
research. The activities in this field are parts of IUPAC conferences on Macromolecule-
Metal Complexes (MMC I–VII [2]), and are summarized in some monographs and several
reviews [3–45].

Various combinations of macromolecules and metal components such as metal ions,
metal complexes and metal chelates exist. The side of the macromolecule considers mainly
organic polymers, for example, based on polystyrene, polyethyleneimine, polymethacrylic
acid, polyvinylpyridines, polyvinylimidazoles and others. The main chain of these
polymers can be linear or crosslinked. In several cases a metal is part of the polymer
chain leading to new structural units. Inorganic macromolecules like silica, different kinds
Copyright 2005 by Marcel Dekker. All Rights Reserved.
of sol-gel materials or molecular sieves can be included also if these macromolecules
are modified in such a way to carry as active part one metal component in a specific kind
of interaction with the carrier. A classification of metal-containing macrom olecules is as
follows.
Type I: A metal ion, a metal complex or metal chelate is connected with a linear
or crosslinked macromolecule by covalent, coordinative, chelate, ionic or p -type bonds
(Figure 1). This type I is realized by binding of the metal part at a linear, crosslinked
polymer or at the outer or interior surface of an inorganic support. Another possibility
uses the polymerization or copolymerization of metal containing monomers.
Type II: The ligand of a metal complex or metal chelate is part of a linear or
crosslinked macromolecule (Figure 2). Either a multifunctional ligand/metal complex or a
multifunctional ligand metal complex precursor are converted in polyreactions to type II
macromolecular metal complexes.
Type III: The metal is part of a polymer chain or network. This type considers
homochain or heterochain polymers with covalent bonds to the metal, coordinative bonds
between metal ions and a polyfunctional ligand (coordination polymers), p-complexes in
the main chain with a metal, cofacially stacked polymer metal complexes and different
types (polycatenanes, polyrotaxanes, dendrimers with metals) (Figure 3).
Type IV: This type is concerned with the physical incorporation of different kinds
of metal complexes or metal chelates in linear or crosslinked organic or inorganic
macromolecules. The formation and stabilization of metal and semicon ductor cluster will
be not considered in this review (Figure 4).
Because in most cases no clear IUPAC nomenclature exists for metal-containing

macromolecules or macromolecular metal complexes, it is not possible to obtain by a
Chemical Abstract literature search a detailed information on them. One ha s to look
for each individual metal, metal ion, metal complex, metal chelate, ligand or also polymer.
For type I usuall y rational nomenclature is used (for example: cobalt(II) complex with/
of poly(4-vinylpyridine) or 2,9,16,23-tetrakis(4-hydroxyphenyl)phthalocyanine zinc(II)
Figure 1 Type I: Metal ions, complexes, chelates at macromolecules.
Figure 2 Type II: Ligand of metal complexes, chelates as part of linear or crosslinked
macromolecules.
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complex covalently bound at poly(methacrylic acid). In the case of type II often the metal
complex in combination with the term poly is used, e.g., poly(metal phthalocyanines)
from 1,2,4,5-tetracyanbenzene. IUPAC nomenclature of type III are described as ‘regular
single-strand’ and ‘quasi single stra nd’ inorganic and coordination polymers in [46]. The
detailed name of the metal complex in polymers or inorganic macromolecules are a
common description for type IV.
B. Kinetical, Thermodynamical, and Analytical Aspects
of Macromolecular Metal Complex Formation
As in low molecular weight metal complexes, the process of complex formation of metal
ion binding in macromolecular metal complexes is accompanied by numerous complicated
factors like ion exchange equilibrium, ligand conformational changes, influence in the
change of the electrostatic potential, etc. Kind and strength of the formed bonds between
metal and ligand depend on the ionisation potential of the metal ion , its electron affinity
and the donor properties of the ligand groups. For macro molecular metal complexes
either in solution or in the solid state various secondary binding forces are of importance
and determine, besides the covalent and ionic bonds, secondary, tertiary and quaternary
structures. In addition, specific polymer parameters like degree of crosslinking,
distribution of ligands, and, in the case of insoluble polymers, the topography of a
macroligand or protecting high molecular weight surrounding must be considered. Many
unsolved problems exist in the field of physical chemistry of complex formation, secondary
binding forces, composition and reactivity of metal-containing polymers due to their

manifold structures. The present situation is best described in [3].
Different models were used to describe the interaction of metal ions with
macroligands of type I and some type II complexes. In one considered model for linea r
Figure 4 Type IV: Physical incorporation of metal complexes, chelates.
Figure 3 Type III: Metals as part of a linear chain or network.
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macroligands the polymer ligand L is the central particle, and the metal ion/complex is
added in a stepwise manner. In this case the equilibrium constant will not depend on the
molecular weight of the macroligand. A second model based on the metal ion M as central
particle is described by the Flory concept of infinitely large chains with the reactivity
of binding centers independent on their position in the polymer [3]. Another approach
calculated the sequence equilibrium which means equilibrium constans for the metal ion
binding at different positions at the macroligand ([47,48] and literature cited therein).
The equilibrium is usually described by the equilibrium constant
"
KK of a macroligand
L-containing metal ion (M
þ
) as complexed repeating units [equations (1) and (2)] [3,47–51]
(Cp and Cs: initial concentrations of polymer (expressed in repeating units) and metal salt;
a: fraction of metal ion/complex not complexed by the polymer).
ð1Þ
ð2Þ
The right side of equation (3) is not totally correct because the equilibrium
concentration of the macroligand [–L
n
–] 6¼ (Cp/n-Cs(1  a)) [47]. The reason is that a
sequence of n þ 1 vacant repeating units can consist of different but overlapping neighbor
sequences of polymer units. Different length between not complexed sequences exists
which influence each other and results in different equilibrium constants k

1
, k
2
, k
3
k
x
[equations (3)–(5)].
ð3Þ
ð4Þ
ð5Þ
A theoretical model allows to determine k
1
and k
2
on the basis of a numeral fit
a ¼ f(n, [L]
0
,[M
þ
]
0
, k
1
, k
2
)with[L]
0
,[M
þ

]
0
. The validity of the model was tested for the
interaction of Na
þ
(as Na
þ
B[C
6
H
5
]
4

) with poly(oxyethylene) in methanol. The best
fit between measured and calculated values are found for n ¼ 1withk
1
¼ 1.9 mol
1
L and
k
1
/k
2
¼ 3.5. Cooperative effects with changes in polymer chain conformati on under
complex formation must be considered in addition [3]. Bending of a polymer chain
by coordination of different ligand groups of one polymer chain leads to an increase of
macroligand reactivity (increase of formation constant in comparison to separated,
e.g., low molecular weight ligand enters). This was discussed for metal binding at
poly(oxyethylene) and poly(4-vinylpyridine) [52,53].

Copyright 2005 by Marcel Dekker. All Rights Reserved.
In the case of crosslinked macroligands electrostatic factors significantly influence
the co mposition, structure and stability of a metal complex. Metal ion/complex binding
can be described as mentioned before. In heterogeneous systems, when the ligand groups
are mainly arranged on a surface with zero concentration in solution, diffusion and
topological restrictions must be considered. At low binding center concentrations a
Langmuir equation is valid for binding of a metal ion/complex [equation (6)] [3,53]
( f: maximum binding of metal ion/complex by a macroligand).
½M
þ

½M
bound
¼
1
"
KK
þ
½M
f
max
ð6Þ
One example is the binding of Cu
2þ
by a crosslinked polymer containing bis
(carboxymethyl)amino ligand groups with
"
KK ¼ 3:5  10
3
L=mol and f

max
¼ 0.075 mmol/g
[54]. For a non-porous solid matrix containing ligands grafted on a surface the stability of
the complex is independent of the degree of surface coverage as shown for CuCl
2
or PtCl
2
on Aerosil from acetonitrile [55].
The formation of type II metal-c ontaining macromolecules obtained by the reaction
of bi/multifunctional low molecular weight metal complexes with another bi/multi-
functional ligand can be evaluated by usual rate constants, equilibrium and kinetics
as known for polycondensation or polyaddition reactions in macromolecular chemistry.
Increasing insolubility results easily in chain termination and formation oligomers.
The therm al polycondensation of dihydroxy(metallo)phthalocyanines to cofacially
stacked polymer in the solid state as example of a type III polymers [equation (7)] is
topotactic and under topochemical control, which means that well-defined intermolecular
distances and interactions in the lattice control the reaction [56]. Following a kinetic study
the fraction of unreacted –OH end groups X over time does not obey a first order kinetics
(X ¼ exp( k
2
t
2
), M ¼ Si, Ge, Sn; n ¼ 50–200).
nHOMðPcÞOH ! HOð MðPcÞOÞ
n
H þ n1H
2
O ð7Þ
Besides the kinetic also the thermodynamic during the formation of MMCs is
complicated. Changes of the conformation of macromolecules, for example, the chain

flexibility, the electrical charges and others influence the thermodynamic parameters such
as ÁS in the formation of different types of metal-containing macromolecules [3,57].
The general expression for the reaction is shown in equation (8).
ÁG ¼RT ln
"
KK ¼ ÁH  TÁS ð8Þ
For the formation of a low molecular weight chelate the so-called chelated effect in
dependence on kind of solvent interaction is in the order of  5to 20 kJ/mol mainly
determined by entropic terms). The polymer chelate effect for type I polymers is more
complicated and includes besides the above-mentioned parameters also local, molecular
and supramolecular organizations of macromolecules [6,58]. With a low degree of
chelation ÁH for macroligands and low molecular weight ligands in the interaction with
metal ions are comparable, but ÁS is different (polymer chelate effect) as it was shown for
the reaction of amines with Cu
2þ
[59]. For concentrated solutions as well as suspensions,
interactions such as intermolecular or supramolecular organizations must be considered
and are determined by entropic terms. A more detailed discussion are included in [3].
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By intermolecular interactions between the macroligand and the metal ion/complex
the temperatur e of ligand $ gel formation, T
tr
, is influenced by the ultimate polymer
concentration L
ul
[60]. Above L
ul
the T
tr
is independent on the concentration of the

polymer and its molecular weight. In the case of Fe
3þ
-polyhydroxamine acid, infinite
networks are formed when the probability of intermolecular metal binding is above
50% [6,61].
Type II and III metal-containing macromolecules often form insoluble, more or
less crystalline products. Therefore entropic terms going from solution to a crystalline
or amorphous precipitate must be considered. Entropic terms are also important for the
stabilization of metal clusters or metal complexes/chelates in a high molecular weight
surrounding (type IV compounds).
During formation of MMCs various thermodynamic side effects driven by a
thermodynamically favoured terms can occur. This includes conformational changes,
modification of functional groups and also macrochain breakage. Examples of
conformational changes are: chain transformation in poly(oxyethylene)-transition metal
complexes [61,62], double helix model of poly(oxyethylene)-alkali metal ion complexes
[63], conformational modifications of poly(2-vinylpyridine) or poly(amidoamines) during
complex formation [64,65], and others. Important to mention here is that chain
destruction can occur in type I polymers during their formation [3,66,67].
A detailed analysis is the fundamental prerequisite to correlate structure and
properties of the new materials. After preparation and isolation of a metal-containing
macromolecule at first one has to analyze on the composition of the new material (primary
structure). Well-known analytical methods can be used. For soluble compounds usual
methods of molecular weight determination can be applied. Microcalorimetric studies
allow to measure the enthalpy of formation of a metal-containing macromolecule. In some
cases by potentiometric or conductometric measurements complex formation constants
can be determined [3,6]. More complicated are the investigation of the secondary, tertiary
and quaternary structure of metal-containing macromolecules either in solution or in
the solid state. Each method (IR, UV/VIS/NIR, Raman, acoustic, dielectric loss, several
methods of x-ray and Mo
¨

ssbauer, ESCA, XAFS, various magnetochemical, ESR
techniques, solution/solid NMR, etc.) provides some information on type I–IV
compounds.
In nearly every case some special analytical investigations must be carried out.
This is demonstrated for polyphthalocyanines of type II structure. These polymers are
obtained by two-dimensional layer growth from various tetracarbonitriles as bifunctional
monomers. A polymeric phthalocyanine has in an ideal case a regular planar structure
which can be treated in a two-dimensional Cartesian coordinate system allowing positive
integers (propagation directions of the polymers are denoted by the letters x and y) [68]. A
model describing the structural features such as degree of polymerization, size and shape
of polymeric phthalocyanines has been discussed. Equation (9) correlates now the number
of macrocycles n (degree of polymerization) with the number of bridged monomers b and
the number of end monomers e.
n ¼ b=2 þ e=4 ð9Þ
Evaluation of some data (determination of number of nitrile end groups and groups
of bridged monomers by qua ntitative IR spectra) leads, in dependence on the kind of
tetracarbonitrile and reaction conditions, to values of x ¼ 4–1 and y ¼ 1– 1. In addition
Copyright 2005 by Marcel Dekker. All Rights Reserved.
it was shown that the unique structure of polymeric phthalocyanines exhibits fractal
properties. They have a regular structure and four fractal dimensions for every size/shape/
dilation combination [68]. This important mathematical model can serve as polymer
model for discussing basic fractals. Cofacial stacked polymeric phthalocyanines contain-
ing four substituents and their possible isomers in such a stacking were also treated
mathematically [69].
II. METAL-CONTAINING MACROMOLECULES IN BIOLOGICAL SYSTEMS
A. Metal Complexes in Living Systems
The range of metals used by biological systems is very large, reaching from the alkaline to
the transition metals [14–19]. They play an essential role in living systems, both in growth
and metabolism. Some metals such as Na, K, Ca, Mg, Fe, Zn are necessary in g quantities.
Other trace elements such as Cu, Mn, Mo, Co, V, W, Ni are essential beneficial nutrients

at low levels but metabolic poisons at high levels. Some meta l ions such as Pb, Cd are
called ‘detrimental metal ions’ because they are toxic and impair the regular course at life
functions at all concentrations.
Metal ions such as Ca, Mg, Na, K, Mn exhibit more ionic or coordinative
interactions whereas Pt, Hg, Cd, Pb are going more for the covalent bonds, and Ni, Cu, Zn
have to be considered as inter mediates. In biological systems metal ions can coordinate to
a variety of biomolecules such as (Table 1):
 proteins at the (C¼O)- or (N–H)-bonds and especially, at N, O, S-donor atoms
of side chains;
Table 1 Important bioligand groups and their coordination to metals in natural systems (after
Reedijk in [3])
Ligand group Metal Substance in which detect or proven
¼O Fe P-450 enzymes
–OH Fe, Zn Carbonic anhydrase
H
2
O Fe, Zn, Ca Many proteins; additional ligands
O
2
/O
2
2
Fe, Cu Hemoglobin, hemocyanin, hemerythrin
O
2

Cu, Fe Superoxide dismutase
–OOH

Fe Haemerythrin

Tyrosine Fe Oxidases
Glutamase (and Asp) Fe Hemerythrin, ribonucleotide reductase
OPO
2
R Ca, Mg Nucleic acids; ATP
NO
3

,SO
3
2
Mo Several reductases
–Cl

Mn Mn cluster in photosynthesis
–S
2
Fe, Mo Ferredoxin; nitrogenase
–SR

(cysteine) Fe, Cu Ferrodoxin, plastocyanin, P-450, azurins
Me–S–R (methionine) Cu, Fe Plastocyanin, cytochromes, azurins
Imidazole Cu, Zn, Fe, Mn Plastocyanin, insulin
Benzimidazole Co Vitamin B-12
(N<)

(peptide) Cu Albumin
Tetrapyrroles Fe, Co, Ni, Mg Prosthetic groups, hemoglobin
CO Fe Toxic for myoglobin; cytochrome oxidase
(CH

2
–R)

Co Vitamin B-12
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 nucleic acids at basic N-donor atoms or at phosphate groups;
 carbohydrates and lipids at (C–O)- and (P–O)-groups;
 in solid bones, teeth, kidney stones.
Metal or metal compound clusters are found, for example, in the respiratory chain
(Fe–S clusters) or in the photosynthesis apparatus (Mn clusters).
B. Metal Complexes at Natural Polymer
A bridge betw een natural and artificial macromolecular metal complexes is the interaction
of metal ions/complexes with peptides/proteins [70], nucleic acids/DNA [71,72], enzymes
[73], steroids [74], carbohydrates [75]. Biometal-organic chemistry concentrates on
such complexes [15]. The reason for the increasing interest in this field lays in medical
applications of metal complexes [16,76] (cancer, photodynamic therapy of cancer –
immuno-assays, fluorescence markers, enantioselective catalysis, template orientated
synthesis of peptides) as exemplarily shown below.
Stable metal complexes can be employed as markers for biochemical and biological
systems in immuno-assays, radiographic and electron microscopic investigations of active
centers and use as radio pharmaceuticals. Essential is a covalent stable linkage. One simple
possibility is the functionaliz ation of peptides and proteins by acylation of, e.g., lysine side
chains using succinimyl e sters [70]. Modification of this reactive unit with transition metal
complexes such as cyclopentadienyl complexes, sandwich complexes or alkinyl clusters
leads to the activated carboxylic acid derivatives which can be isolated and reacted with
the free amino group of lysine units in peptides and proteins. Fourier-transform-infrared
spectroscopy (FT-IR) at 1900–2100 cm
1
allows the detection of the bonded carbonyl
complexes down to a dection limit of the picomol region. The carbonyl-metallo-

immunoassay (CMIA) has the advantage that no radioactive compounds are nec essary
and by use of different metal organic markers several immuno assays can be carried out
simultaneously. Other possibilities are reviewed in [70].
The chemotherapy of cancer with cytotoxic drugs is one of the major approaches.
Most cytotoxic anticancer drugs are only antiproliferative which means that the process
of cell division is interrupted. cis-Diaminedichloroplatinum(II) (nicknamed cisplatin)
is used today routinely against testicular and ovarian cancer. In order to develop new
more selective and active anticancer drugs based on platinum, the interaction of the active
model compound cisplatin with DNA is important. Structural data have shown that the
binding of cisplatin to DNA occurs preferentially at the N7 position of adjacent guanines
[72,75,77]. This binding leads to local denaturation of DNA, inhibits the replication
process and kills the tumor cells. Because cisplatin possesses two reactive Cl-groups,
intrastrand and interstrand crosslinking can occur.
Several ruthenium complexes wer e investigated in the interaction with proteins,
cytochromes and nucleic acids [78]. The reason is to use these Ru-complexes as
luminescence sensors (e.g. optical O
2
sensor), to trigger electron transfer and photo-
induced electron transfer in proteins and DNA. For example, elect rogenerated
chemoluminescence (ECL) of Ru(phen)
3
2þ
(phen: 1 ,10-phenanthroline) can be used to
detect the presence of double-stranded DNA (details see [78, p. 642]). Ru(phen)
3
2þ
binds
strongly to double-stranded DNA, and minimal binding is observed in the presence
of single-stranded DNA. If a given single-stranded DNA sequence is immobilized on
an electrode, treatment with a suitable target DNA may generate double-stranded

DNA which allows the binding of the Ru-complex and by electrode reactions the detection
of ECL.
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III. TYPE I: BINDING OF METALS TO MACROMOLECULAR CARRIERS
Several possibilities, as shown in Figure 1, exist for the binding of metal ions/complexes/
chelates to a variety of macromolecules. Methods for the preparation can be subdivi ded
into two main routes:
 Reaction of a macromolecule bearing suitable ligands or reactive sub stituents for
metal ion/complex/chelate binding [equation (10)]
 Homo- or copolymerisation of a vinyl monomer (or other polymerizable groups)
bearing a metal complex/chelate or a ligand as a metal complex/chelate precursor
[equation (11)].
Along both routes linear or crosslinked materials can be used or obtained. Type I
compounds with a linear backbone are soluble and can be coated to thin film devices.
Crosslinked materials possess in dependence on the amount of crosslinking and procedure
of copolymerization pores of different type and size with more or less uniform cross-linked
density [79]. One example is amorphous polystyrene crosslinked with divinylbenzene.
Non-porous examples are partially crystalline polymers like polyethylene and some
inorganic carriers like silica gel. Ligand/metal ion/complex/chelate groups can be
distributed on the whole polymer volume or localized only on the carrier surfa ce and
connection to the carrier is possible via a direct bond or spacer. All possibilities result in
different relativities (properties) of the materials [80,81].
ð10Þ
ð11Þ
A. Anchoring of Metal Complexes or their Ligands
at an Organic Macromolecule
1. General Considerations
A macromolecular ligand principally can interact with a metal compound MX
n
by

covalent, coordinative, ionic, charge-transfer or chelate bindings. The interactions with an
organic polymer ligand may occur either through monodentate binding (a) (when MX
n
possesses only one coordination vacancy or group for interaction with the polymer ligand)
and polydentate binding either intra-(b) or intermolecular (c) [equation (12)]. In the case
of linear or branched organic polymers the macromolecular complexes (a) as a rule, are
soluble in organic solvents and their structure is identified rather easy. The solubility of
the bridged macrocomplexes (b) decreases; they are more stable and have a less-defined
structure. The complexes (c) with the intermolecular bridge bonds are insoluble and
difficult to characterize. Exemplarily, it was shown for hydroxyamic acid copolymers that
Copyright 2005 by Marcel Dekker. All Rights Reserved.
infinite networks are formed when the probability of intermolecular binding of metal ions
exceeds 50% [82].
ð12Þ
The complex formation on the surface of inorganic carriers preferably occurs by the
intramolecular types (a) and (b).
The interaction of a polymer ligand with metal ions in aqueous solutions is explained
in more detail. Figure 5 shows the dependence of the changes of the hydrogel swelling
coefficient of poly(ethylenimine) (PEI) and polyallylamine (PAAHC l) hydrochloride
hydrogel and reduced viscosity of its linear polymer on the concentra tion of copper sulfate
(C(CuSO
4
)) in aqueous solution (curves a and b) and the ratio of polymer functional
groups (C
p
) to metal ions concentration (curves c and d) [83]. Characteristic of both
investigated systems is the strong compression of hydrogel volume with increasing amount
of the metal ion. Attention must be paid to the fact of the influence of the degree of
macroligand ionization on the character of the conformational change of the linear
segments of the gel. It is seen that under high pH the swelling coefficient of the PEI gel

passes through a maximum in the gel-metal ion systems at a concentration of CuSO
4
equal
to 8  10
3
mol/L for Cu
2þ
(molar ratio of Cu
2þ
: PEI ¼ 0.25). The increase of hydrogels
swelling degree under complexation with metal ions at high pH can be explained in terms
of additional charges in the slightly-charged gel by bivalent metal ions coordinated with
the amino groups of PEI. The latter increases the electrostatic energy of the system
resulting in an increased swelling coefficient. For the PAA-HCl hydrogel a decrease of the
swelling coefficient caused by intramolecular chelation between metal ions and polyligands
is observed. This results in additional cross-linking in the network due to the donor–
acceptor bonds and compactization of linear parts of polymers between covalently cross-
linked points. At low values of pH the complexation proceeds by substitut ion
mechanism of protons of the protonized nitrogen atoms of the gel by metal ions avoiding
the stage when the polymer chain acquires charge as it was observed at high pH values
Copyright 2005 by Marcel Dekker. All Rights Reserved.
(see Figure 5(a), gel PEI-Cu
2þ
, curves a and b also). An appropriate correlation between
changing of K
sw
and reduced viscosity of the gel and linear polymer is observed (Figure 5,
curves c and d).
In most cases the structure of the local chelated unit in macromolecular metal
complexes is the same as in the low molecular weight analogues. But the polymer chain

may provide a significant influence. For salicylaldimine ligand the structure of the complex
units are different in low molecular weight an d macromolecular ones: planar as low
molecular weight complex and distored tetrahedral as macromolecular complex [84]. The
influence of ring size on the mechanism of the binding of metal ions by polyme rs can be
illustrated in relation to the formation of complexes between TiCl
4
and the copolymers
of styrene and the diallyl esters of dicarboxylic acids [85]. For n ¼ 1 or 2, a mixture of
complexes with the cis-disposition of 1 and trans-disposition of 2 of the carbonyl groups
is formed. Increase in the size of the separating bridge (n > 3) precludes the formation of
type 1 complexes.
The complex formation can be influenced also by the nature of the connecting bridge
between the complexing unit and the polymer chain. For example, the transfer of Cu
2þ
from the aqueous to the organic phase (chloroform, toluene) for the formation of a
complex with a hydrophobic low molecular weight ligand (compound 3a) occurs readily.
In contrast, complexation by the polyme ric analogue 3b is ineffective. Only the
Figure 5 Dependence of the swelling degree and reduced viscosity for PEI gels (a, b), PAA  HCl
gel (c) and its linear polymer (d) on the CuSO
4
concentration at pH 8.3 (a, c, d) and 6.5 (b).
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replacement of the short and hydropho bic methylene bridge in compound 3b by the long
hydrophilic ethylenediamine (compound 3c) or methylami ne (compound 3d) unit leads to
appreciable hydrophilicity and spatial mobility of the complexing unit. This results in the
diffusion of ions in the polymeric medium and allows the ligands bound to the polymer to
be more mobile [86]. By steric hindrance of the macromolecular chain the formation of a
multidentate complex often cannot occur. In polystyrene being substituted by bipyridyl
groups the formation of a monodentate complex 4 and not of the expected trisbipyridyl
complex is observed [87].

The closed packing in a polymer chain may lead to uncoordinated ligand groups.
Poly(4-vinylpyridine) dissolved in an ethanol/water mixture results with Co-acetylaceto-
nate in a degree of complexation of  0.7. The rate of formation of the Co(II)-complex in
with R partly quarternized poly(4-vinylpyridine) decreases due to steric reasons as follows:
R ¼ –CH
3
> –CH
2
–C
6
H
5
[88].
Another important point of stereochemical recognition with metal ions called
‘template’ or ‘memory’ effect is mentioned. A template effect is observed during the
formation of the complexes of corresponding ions with some copolymers followed by
cross-linking of the chains [89–92]. The structure of the macrocomplex formed during
interaction of the metal ion with the ligand is strictly determined by their nature. If then
the metal ion is removed and simultaneously the formed stereostructure of the polymer is
preserved, the remained polymer ligand has ‘pocket’ fitted to the same metal ion
(templates) which were removed from the polymeric matrix [equation (13)]. Selectivity and
the value of the template effect depend on the spatial organization, on the nature of the
complexing ligands and the stabilities of the formed complexes. Examples are complexes
of poly(4-vinylpyridine) crosslinked with 1,4-dibromobutane or complexes of poly-
ethyleneimine crosslinked with N,N
0
-methylenediacrylamide [92].
Copyright 2005 by Marcel Dekker. All Rights Reserved.
For the crosslinked polyethyleneimine the distribution coefficients of the
non-prearranged polymer between Cu

2þ
and Ni
2þ
is  7.8, whereas for the Cu(II)-
prearranged polymer the value is  6.25, and the Ni(II)-prearranged polymer the value is
 0.9 which shows different selectivity in metal ion uptake. Catalytic activities for
oxidation reactions were investigated.
ð13Þ
Another possibility for realizing a template effect used the copolymerization of metal
complex vinyl monomers. Copolymerization of Ni(II), Co(II) or Cr(III) complexes of
bis[di-4-vinylphenyl)]dithiophosphinates with styrene and ethyleneglycoldim ethacrylate
yields crosslinked polymers which exhibit after removing of the metal ion in some degree
the selectivity of the ‘own’ metal ion [92,93]. Copolymerization of the Zn(II)-complex of
1,4,7-triazacyclononane with divinylbenzene (molar ratio  1 : 3) results in a macroporous
copolymer containing sandwich complexes 5 of the Zn(II) complex [94]. After removal of
Zn(II) the prearranged copolymers show now a selectivity of Cu
2þ
:Zn
2þ
up to 157 : 1.
This means that the thermodynamic stability of the new complex formation dominates in
this case over the template effect. But the template effect of Zn
2þ
for Cu
2þ
results in a high
selectivity of Cu
2þ
against other transition metal ions such as Fe
3þ

. Altogether the
prearrangement effects are difficult to predict and further research is necessary.
B. Binding of Metal Ions or Complexes at Organic Polymers
Different polymer analogous reactions are applied for the functionalization of polymers
by ligands or metal ion/complexes/chelates. The most employed method uses the
immobilization of a ligand capable of metal ion complex binding in a second step
[3,6,41]. Immobilized lignad groups contain, for example, oxygen, nitrogen, sulfur,
phosphorus and arsenic donors. Beside open chain ethers and amines also cyclic ethers
and amines are used. Other examples of chelating groups are pyridine-2-aldehyde,
iminodiacetic acid, 8-hydroxyquinolin e, hydroxylamine, bipyridyl, Schiff bases, Mannich
Copyright 2005 by Marcel Dekker. All Rights Reserved.
bases, porphyrin-type macrocycles. Often intensively chloromethylated polystyrenes –
either linear or with different degrees of crosslinking – are employed as starting material.
Water soluble polymers with chelate properties are formed by derivatization of linear
polymers such as polyethyleneimine, polyvinylamine, methacrylic acid, polyarylic acid,
N-vinylpyrrolidone [3,6,92,95–97]. Other typical ligands are derived from phosphorus
compounds like phosphines or phosphates at modified polystyrene for transition metal ion
binding [3,6,96]. One example is binding of PdP(C
6
H
5
)
3
Cl
2
or Rh(H)P(C
6
H
5
)

3
(CO) at
diphenylphosphinated polyethylene Bu–(CH
2
–CH
2
–)
n
–P(C
6
H
5
)
2
obtained by polymeriza-
tion of ethylen e with BuLi and quenching with (C
6
H
5
)
2
PCl [97]. Crosslinked polymers
bearing phosphorylic, carboxylic, pyridine, amine and imine functions were used for
the bind ing of Cu
2þ
,Ni
2þ
,Co
2þ
and other transition metal ions. For the well-known

metal ion binding at polycarboxylic acids, polyalcohols, polyamines, polyvinylpyridines
see [3,6]. In the following only some examples are given.
1. Ethers
Poly(oxyethylene)–metal salt complexes are of interest as solid polymer electrolytes after
complex formation with Li
þ
,Na
þ
,K
þ
,Mg
2þ
,Ba
2þ
(see [3,6,41,98] and literature cited
therein). The synthesis is carried out by direct interaction of the ligand and metal ions in
solution or, if crosslinked poly(oxyethylene) is employed, by immersing the polymer ligand
into a solution of the meta l salt. As polymer ligands also poly(oxypropylene), crosslinked
phosphate esters and ethers were used [99,100]. Polymer cathode materials based on
organosulfur compounds are developed for lithium rechargeable batteries with high
energy density. A 2,5-dimercapto-1,3,4-thiadiazol-polyaniline composed with Li-counter
ions on a copper cathode current collector show high discharge capacity [101].
Crown ether moieties at crosslinked polystyrene are prepared by the reaction of
crosslinked chloromethylated polystyrene with hydroxy-substituted crown ethers (in THF
in the presence of NaH) [102]. Binding of alkali ions were investigated. Crown ether
moieties containing cinnamoyl grou ps 6 which can be crosslinked by UV-irradiation,
are prepared by polymerization of the corresponding vinyl monomer with cinnamoyl and
crown ether groups [103].
Copyright 2005 by Marcel Dekker. All Rights Reserved.
2. Ketones, Carboxylic Acids and Nitriles

Metal acetylacetonates are covalently bound by the reaction of crosslinked chloromethyl-
ated polystyrene (DMF, 100

C) under formation of 7 [104]. Rare earth Eu(III)-complexes
of 1-carboxy-8-naphthoyl bound covalently at polystyrene 8 are obtained by Friedel–
Crafts acylation of the corresponding naphthalenetetracar boxylic acid anhydride with the
polymer followed by reaction with Eu
3þ
[105]. The luminescence properties of lanthanide
ions with polycarboxylates were investiga ted in detail [106]. The effects of the
conformation of polymer chains on electron transfer and luminescence behaviour of
Co(II)-, Co(III)-ethylenediamine complexes at polycarbox ylates were studied [107].
When water-soluble polymers having pendant carboxylic acid residues and
powdered metal oxides containing leachable Ca
2þ
,Al
3þ
, etc., ions in the presence of
controlled amounts of water, metal cation carboxylate anion salt-bridges are generated
which bring about curing or hardening of the formulation [108]. These so-called glass-
ionomers are applied as dental biomaterials. An example is a terpolymer based on acrylic
acid, itaconic acid and methacrolylglutamic acid 9 hardened with Ca
2þ
or Al
3þ
.
Water soluble macromolecular Pd
2þ
complexes with phase transfer ability employ ed
for the Wacker oxidation of higher alkenes were prepared from ligands such as monobutyl

ether of poly(ethylene glycol) functionalized with b,b
0
-iminodipropionitrile and aceto-
nitrile [109]. One example is the polymer ligand 10 complexed with PdCl
2
. Also other
Copyright 2005 by Marcel Dekker. All Rights Reserved.
examples are described in [109].
3. Amines, Amido-Oximes and Hydroxamic Acids
Open chain and cyclic amines can coordinate with various metal ions. Poly(ethyleneimine)
from 2-methyloxazoline by ring opening polymerization was investigated for Na
þ
binding
[110]. Various open chain amines and amides, cyclic amines 11 and amides were
synthesized starting from crosslinked chloromethyl ated polystyrene [111]. The modified
polymers contain up to 2.7 mmol/g amine or amide groups. They were investigated for the
reversible binding of CO
2þ
,Ni
2þ
,Cu
2þ
. Solutions of undoped polyaniline in 1-methyl-2-
pyrrolidinone were treated with Cu, Fe and Pd salts [112]. A bathochromic shift of the
absorption of polyaniline at l  640 nm is attributable to charge transfer from the benzoid
to the chinoid form of the polymer. The complexes 12 are effective in dehydrogenative
oxidation reactions of, e.g., cinnamoyl alcohol.
Water soluble cetylpyridinium chloride modified poly(ethyleneimine) 13 were
investigated for the removal of several cations (Cu
2þ

,Zn
2þ
,Cd
2þ
,Pb
2þ
, etc.) and
anions (PO
4
3
CrO
4
2
) from water [113]. The polymer can form interaction products
with negative ions due to electrostatic bonds and also with metal ions due to complex
formation. Other basic polymers such as poly(vinylamine), neutral polymers such as
polyalcohols and acidic polymers such as poly(acrylic acid) were investigated using the
method of ‘Liquid-Phase Polymer-Based Retention’ for the separation of metal ions
from aqueous solution [114].
Copyright 2005 by Marcel Dekker. All Rights Reserved.
A N-isopropylacrylamide-bound hydroxamic acid copolymer 14 was prepared by
the reaction of poly(N-isopropyl acrylamide)-co-(2-acryloxysuccinimide) with 6-amino-
hexanhydroxamic acid [equation (14)] [115]. This water soluble copolymer after Fe
3þ
uptake quantitatively separates from aqueous solution by heating. By Fe
3þ
uptake of the
copolymer the amount of Fe
3þ
in an aqueous solution is reduced from 15.5 ppm to 116 ppb.

ð14Þ
A crosslinked polystyrene with 2-amido-oxime groups 15 was prepared from
crosslinked chloromethylated polystyrene by cyanoethylation and react ion with hydroxyl-
amine. This polymer ligand shows a good selectivity for the separation of UO
2
2þ
from sea
water [116]. Amideoxime polymers (and their interaction with Cu
2þ
) were also prepared
from macroporous acryl onitrile-divinylbenzene co-polymers by reaction with NH
2
OH
(around 2 mmol/g amideoxime groups in the polymer) [117].
4. Schiff Bases
The reaction of crosslinked polystyrene with 5-chloromethyl-2-hydroxybenzaldehyde
followed by interaction with the Co(II) chelate of the Schiff base from 2-hydroxybenzal-
dehyde with diaminomaleonitrile yields the polymer chelate 16 (content 0.2 mmol/g
chelate centers) [118]. This polymer complex was investigated as catalysts for the
conversion of quadricyclane to norbornadiene. Crosslinked chloromethylated polystyrene
was reacted with N
2
O
3
-Schiff base ligands. The resulting macroligands were investigated
for the binding of Co
2þ
,Mn
2þ
,Fe

2þ
(formula 17) [119]. Also cyclic Schiff base chelates
were synthesized [120]. Gel-type and macroporous versions of a chiral Mn(III)-salen
complex 18 were prepared by the react ion of poly[4-(4-vinylbenzyloxy)salicylaldehyd ] at
first with a chiral 1,2-diaminocyclohexane to 18a and then with salicylaldehyde derivatives
and a Mn salt to 18b as shown in equ ation (15) [121]. These polymers are very active
catalysts in the asymmetric epoxidation of alkenes.
Copyright 2005 by Marcel Dekker. All Rights Reserved.
Copyright 2005 by Marcel Dekker. All Rights Reserved.
5. Pyridyl, Bipyridyl and Other Heterocycles
The excellent complexing ability of the pyridine group led to several investigations on the
coordination of polymers bearing pyridyl or bipyridyl groups with metal ions like Ru
2þ
,
Re
2þ
,Co
2þ
and others [3,6,41,122–124]. Polymers and copolymers of vinylpyridine or
N-vinylimidazole can easily interact by coordinative bonds in solution with a variety of
transition metal salts, metal complexes and macrocyclic metal chelates such as Schiff
base chelates of Co(salen) type, Co(dimethylglyoxim) or porph yrins like 5,10,15,20-tetra-
phenylporphyrin [3,5,125–129]. After film casting, binding of oxygen and its separation in
membranes were investigated. For the coordinative interaction in analogy to coordinative
binding in low molecular weight complexes, the polyme r must have groups with s-donor
or p-acceptor properties. In contrast to monoaxial coordination of low molecular weight
donors with Co-complexes, polymer donors can interact biaxially with the result of
crosslinking, change of polymer conformation and therefore different properties.
Polymer metal complex formation of different polyvinylpyridines in solution, in
hydrogels and at interfaces were investigated [83]. In aqueous solution linear or

crosslinked polyvinylpyridines in the interaction with H
2
PtCl
6
results in reduced viscosities
and reduces swelling coefficients, respectively. Com plexation leads to molecular bridges
and folding of the polymer. Film formation was observed at the interface of poly(2-
vinylpyridine) dissolved in benzene and metal salts dissolved in water.
Ru(II), Cu(II), Cr(III) complexes at 2,2
0
-bipyridyl and poly(4-vinylpyri dine) (PVP)
are reviewed in [3,6,41]. cis-Ru(II)(2,2
0
-bipyridyl)
2
2þ
(Ru(bpy)
2
2þ
) reacts in methanol
with PVP to (Ru(bpy)
2
(PVP)
2
]
2þ
and with PVP in the presence of pyridine (py) to
[Ru(bpy)
2
(PVP)(py)]

2þ
[130].
A polymer complex containing Ru(bpy)
3
2þ
pendant groups was obtained by the
reaction of a lithium substituted polystyrene with 2,2
0
-bipyridyl followed by interaction
with cis-Ru(bpy)
2
2þ
[131]. Another example is binding of 4,4
0
-dicarboxy-2,2
0
-bipyridyl
at a copolymer of p-aminostyrene followed by reaction with cis-Ru(bpy)
2
2þ
(structure 19)
[132]. Other copolymers with pendant Ru(bpy)
3
2þ
bound via a spacer or containing
additional bound 4,4
0
-bipyridyl are also prepared. These materials are interesting as
sensitizers for visible light energy conversion.
Different polybenzimidazoles bearing cyanomethyl ligands were coordinated with

PdCl
2
partly with CuCl
2
as cocomponent, and investigated for their activity catalyst [133].
Copyright 2005 by Marcel Dekker. All Rights Reserved.
Several catalytically active Pd
0
-heteroarylene complexes were prepared by the interaction
of the polyheterocycles, with PdCl
2
followed by reduction with NaBH
4
to Pd
0
[134].
6. Porphyrins and Phthalocyanines
A general route that allows binding of different porphyrins at linear polymers was
described [135,136]. The substituted porphyrines 20 (R ¼ –O–C
6
H
4
–NH
2
), 21 (R ¼ –NH
2
)
and 22 (R¼ –NH
2
) contain nucleophilic amino groups of similar reactivities. Therefore,

an identical synthetic procedure can be applied to conduct the covalent binding to a
polymer with reactive sites. Beside the binding of one porphyrin, the addition of different
porphyrins to the reaction mixture allows the fixation of two or three porphyrins at one
polymer system in a one -step procedure. Mainly a method was selected where a diluted
solution of the polymer was added dropwise to a diluted solution to the porphyrins.
If the reaction of poly(4-chloromethylstyrene) is carried out in the presence of an excess
of triethylami ne, the covalent binding of the porphyrin and a quarternization reaction
occur simultaneously. Positively charged polymers 23 soluble in water were obtained. In
addition to a porphyrin also viologen as electron relay were covalently bonded at
positively charged polystyrene [137].
Negatively charged polymers 24 containing porphyrin moieties are easily synthesized
by the reaction of poly(methacr ylic acid) (activation of the carboxylic acid group by
carbodiimides or triphenylphosphine/CCl
4
) with the porphyrins [135,136]. Uncharged
water-soluble polymers 25 containing the porphyrin moieties are obtained by the reaction
of poly(N-vinylpyrrolidone-co-methacrylic acid) with the low-molecular-weight substi-
tuted porphyrins in the presence of the same activating agents for the carboxylic acid
groups. Residual carboxylic acid groups were converted to methyl esters. The employed
porphyrins 20–22 contain four reactive functional groups. Therefore inter- and intra-
molecular crosslinking may occur in the reaction with the polymers employed.
Intermolecular crosslinking could be avoided up to an amount of 2 mol% of applied
porphyrins corresponding to one unit of the polymers. Higher amounts of porphyrins
result in the formation of gels due to intermolecular crosslinking. Viscosity measurements
indicate intramolecular crosslinking (micro-gel formation) in some cases. The porphyrin
moieties in the polymers can act as antenna for reactions for electron and photoelectron
transfer reactions. By studying these reactions, information concerning the polymer
environment can be obtained [136,137].
Copyright 2005 by Marcel Dekker. All Rights Reserved.
Some other reports describe the binding of tetracarboxyphthalocyanines at linear

polystyrene [138] or macroporous polystyrene grafted with polyvinylamine [139,140], of
chlorosulfonated phthalocyanines at macroreticular polystyrene [141] and of tetra-
chlorocarboxyphthalocyanines at poly(g-benzyl-
L-glutamate) [142].
The donor properties of suitable nitrogen containing macromolecular ligands are
used in a Lewis base/Lewis acid interaction with cobalt or iron in the core of porphyrin-
type compounds to achieve a coordinative binding. Some years ago the coordinative
binding of cobalt phthalocyanines 20 with R ¼ –COOH or R ¼ –SO
3
H was examined
taking polymer ligands such a poly(ethyleneimine) [143–145], poly(vinylamine) [143–148],
amino group-modified poly(acrylamide) or modified silica gel [146]. For 20 (R ¼ –COOH,
M ¼ Co(II)) conclusive evidence of axial coordination was obtained by ESR showing
a 5-coordinative complex structure [146]. Increasing concentration of poly(vinylamine)
shifted the equilibrium between monomer and aggregated such as dimer form to the
monomeric phthalocyanine. A high concentration of polymer ligands separates the chelate
molecules in the polymer coil (shielding effect). The materials were investigated as catalysts
in oxidation reactions.
Recently, the electrochemical properties of cobalt phthalocyanines included by
coordinative binding in membranes of poly(4-vinylpyridine) [149] or poly(4-vinylpyridine-
co-styrene) were investigated [150]. The membranes were prepared by dissolving 20
(R ¼ –H, M ¼ Co(II)) in DMF in the presence of poly(4-vinylpyridine). The coordinative
interaction of the metal complex to the pyridyl group strongly enhances the solubility of
the phthalocyanine in DMF. The film formed on a carrier after casting and evaporation
of the solvent is homogenously blue. The pattern in the UV/Vis spectra of the films are
comparable to the Co-phthalocyanine dissolved in pyridine showing homogenous
monomeric distribution of the metal complex in the polymer. In contrast, the film of
the cobalt complex casted from pyridine solution shows a strong resonance broadening of
the long wave length band, indicating its crystallinity.
Copyright 2005 by Marcel Dekker. All Rights Reserved.

An electrostatic binding occurs easily by ionic interactions of oppositely charged
macromolecular carriers and phthalocyanines. Positively charged polymers such as ionenes
[–N
þ
(CH
3
)
2
–(CH
2
)
x
–N
þ
(CH
3
)
2
–(CH
3
)
2
–(CH
2
)
g
–]
n
form stoichiometric complexes in
the interaction with tetrasul fonated 20 (R ¼ –SO


3
,M¼ CO(II)) in the composition N
þ
/
CoPc(SO
3

)
4
of 4 : 1 [146,151,152]. The tendency of aggregation of phthalocyanines in water
strongly depends on the hyd rophilic character of the kind of latexes based on copolymers of
styrene, quarternized p-aminomethylstyrene and divinylbenzene [153]. Increasing content
of quarternized comonomers enhances the content of non-aggregated 20 (R ¼ –SO

3
,
M ¼ Zn(II) absorbing at l  685 nm compared to aggregated ones absorbing at l  640 nm
due to a shielding effect for the positively-charged phthalocyanine.
An ionic binding at charged crosslinked polymers can easily be realized by treating
with a solution of an oppositely charged metal complex. Shaking of a positively charged
ion exchanger, for example Amberlite, with the negatively charged 20 (R ¼ –SO

3
M ¼ Zn(II), Al(III)(OH), Si(IV)(OH)
2
), results in blue-colored polymeric complex es 26
containing monomeric distribution of the MPc [154]. These compounds are very effective
photosensitizers for the photooxidation of several substrates by irradiation with visible
artificial or solar light.

C. Binding of Metal Complexes on the Surface of
Macromolecular Carriers
For different properties such as catalysis it is favourable to create reactive sites on the
surface of an organic polymer or an macromolecular inorganic carrier. Anchoring of
metal complexes exhibit the advantage of higher reaction rates for reactions at the metal
complex centers and the easiness of the separation from the reaction for reuse. Covalent
anchorage can be realized by polymerization of different monomers bearing ligand groups
L for metal complex formation (for example, by mechanical, chemical or irradiated-
chemical treatment of the carriers [equation (16)] [3,6]. Gas phase grafting is achieved by
polymerization initiated by irradiation (g-irradiation) accelerated electrons, low-pressure
gas discharge [3,6].
ð16Þ
Copyright 2005 by Marcel Dekker. All Rights Reserved.
Some papers describe the grafting on polymers containing bond metal complexes on
the surfac e of org anic polymers: polyethylene-graft-poly(methylvinylketone)/Schiff base
with 2-aminophenol 27 [6,37,155] or salicylaldehyde hydrazide [156], polyethylene-graft-
poly(vinyl-1,3-diketo ne) [157], polytetrafluorethylene-graft-poly(acrylate)-complexes with
2,2
0
-bipyridyl or 1,10-phenanthroline [157].
More intensively the immobilization of metal complexes on inorganic macromolecules was
investigated. The covalent binding was described and reviewed in [3,158]. Some examples
are the reactions of Cp
2
Zr(CH
3
)
2
(Cp ¼ cyclopentadienyl) or diorgano-ZrCl
2

with silica
gel and alumina (after treatment with AIMe
3
as catalysts for the olefin polymerization),
dichlorotitanium pirocathecolate with silica gel, binding of a nickel P/O chelate at silica gel
modified with tetrabenzyltitanium followed by binding of a nickel P/O chelate, and
preparation of alumina-supported bis(arene)-Ti and tetra(neopentyl)-Zr [159]. The interest
in this work is related to obt ain heterogeneous catalysts for the olefin polymerization.
Ligands for transition metal ion interaction at silica gel were obtained by covalent
connection of trialkoxysilanes containing a ligand group such as N,N-dimethylamino [160]
or ethylenediphenylphosphine [3,6,161,162] silica-grafted 3,3
0
,5,5
0
-tetra-tert-butylbiphe-
nyl-2,2
0
-diylphenylphosphite [96] and trimethylenephosphine covalently linked to silica
[163]. Different tridendate bis(2-pyridylalkylamines) have been couple to 3-(glycidyloxy-
propyl)trimethoxysilane and subsequently grafted onto silica [as an example see 28 in
equation (17)] [164]. The ligand concentration varie d between 0.29–0.63 mmol g
1
. Most
ligands selectively absorb Cu
2þ
from aqueous solution containing a mixture of different
metal ions. Silica was modified by 3-chloropropyltrimethoxysilane and afterwards reacted
with 2-(phenylazo)pyridine which is a good lignad for Ru
3þ
[165]. This macrom olecular

Ru-complex is a good catalyst for the epoxidation of trans-stilbene.
ð17Þ
The immobilization of phthalocyanines by covalent binding to inorganic macro-
molecular carriers such as silica is a prospective approach to achieve heterogenous
Copyright 2005 by Marcel Dekker. All Rights Reserved.
catalysts and photocatalysts in which the carrier is stable against severa l chemicals
including oxygen. With loadings of  10
5
–10
6
mol per g carrier monomolecular
dispersion of the phthalocyanine are achieved [166–168]. Different silica such as
macroporous Lichrosorb (surface area  300 m
2
g
1
), macroporous Lichrosphere
(surface area  40 m
2
g
1
), Fractosil (surface area  8m
2
g
1
) and monosphere silica
(surface areas between 24 and 1.7 m
2
g
1

) – all silica from Merck AG – are employed.
In the first step the silica surfaces were modified to obtain chemically active positions
for the attachment of substituted phthalocyanines. Functionalization was achieved
by reaction with 3-aminopropylsilyl groups for binding of 20 with R ¼ –COCl to
synthesize 29 or with 3-chloropropylsilyl groups for the binding of 20 with R ¼ –NH
2
to synthesize 30 [equations (18) and (19)]. The loadings are with substituted silyl
groups between 10
3
and 10
4
mol g
1
and with phthalocyanines between 10
5
and
10
6
mol g
1
. Comparable covalent binding can be carried out also on the surface of
titanium dioxide [169].
ð18Þ
ð19Þ
For the coordinative binding of phthalocyanines at inorganic carriers, the surface
has to be modified. In a one-step-procedure for the preparation of silica modified on the
surface with imidazoyl-groups, different silica materials as mentioned before were treated
with a mixture of 3-chloropropyltriethoxysilane and an excess of imidazole in m-xylene
[equation (20)]. Following treatment with different kind of substituted cobalt phthalo-
cyanines, naphthalocyanines and porphyrins 20–22 in DMF led to the modified silica as

exemplarily shown with 20 (R ¼ –H) for 31. The silica contains  0.8–12 mmol g
1
metal
Copyright 2005 by Marcel Dekker. All Rights Reserved.
complex moieties [167,170].
ð20Þ
D. Polymerization of Metal Containing Monomers
Vinyl and related unsaturated groups being substituted by different kind of metals
can be employed in polymerization or copolymerization reactions. If no side reactions
occur by metals, uniformly substituted chains are obtained. A classification of the
monomers is based on the type of bond between the metal and the organic part as
shown in Figure 6 [4,12]. Covalent-type compounds contain real organometallic ‘metal–
carbon’ or ‘metal–oxygen’ bonds. Monomers of the coordinative type are often formed
in the interaction of heteroatoms with unshared pairs of electrons and transition
metal compounds. Characteristic for p-bound compounds are transition metals of the
groups VI A, VII A and VIII of the periodic table. Non-transition metals are more
characteristic for the ionic type. True organometallic compounds with metal–carbon
bonds are only rarely described. Monomers of the complex/chelate type contain a vinyl
group at the complexing ligand for binding of various metal ions. Either the ligand
with subsequent metallation or the complex/chel ate can be employed in polyme rization
reactions.
Due to the reactivity of the metal for itself or of the kind of binding to the
unsaturated monomer part, several side reactions can occur during the radicalic,
anionic, cationic or Ziegler–Natta-type polymerizations. Some aspects of side reactions
are [171]:
 By elimination of metal or metal containing groups during the polymerization
formation of non-uniform units in the polymer chain.
 Formation of different oxidation states of metals in units in the polymer chain.
 Irregularity in the polymer chain by formation of new chemical bonds between
the monomer and the metal containing group.

Figure 6 Classification of metal containing monomers for polymerization.
Copyright 2005 by Marcel Dekker. All Rights Reserved.