o-Phthalate anion is a well-known versatile ligand which has been extensively used
in the design of coordination compounds due to a variety of its bonding abilities. As
a result of the two ortho-carboxylic groups, the ligand has the capacity to chelate as
well as to bridge up to seven metal centers at once forming mono- and polynuclear
complexes. Based on analysis of the crystal structures of phthalates extracted from the
Cambridge Structural Database (CSD) we have shown [1] that the phthalate ligand
can adopt 26 coordination modes with metal atoms in the complexes. Moreover, both
monodeprotonated HPht- anions and neutral H2Pht molecules are able to co-exist
with fully deprotonated Pht2– residues of acid in crystals, leading to some unexpected
architectures. However, the 1,6-bridging mode remains the most commonly seen in the
complexes. In this case, the phthalate anion is a bidentate ligand and coordinates to metal
ions by one oxygen atom from each of the carboxylate group. This structural motif of the
ligand promotes the formation of polymeric structures. It is noteworthy that when the
1,6-bridging mode is realized the other oxygen atoms from the same carboxylate groups
are also able to coordinate additional metal ions resulting in supracage assemblies or
complicated polymeric structures. Furthermore, additional interesting features of this
ligand was found. For example, in an extremely unusual dimer [(bpy)2Zn(Pht)H(Pht)Zn
(bpy)2)](HPht)(H2Pht)⋅2H2O ( where bpy = 2,2’-bipyridine), [Zn(bpy)2] metal cores are
connected through O•••H•••O hydrogen-bonded bridges between carboxylate groups of
two different coordinated phthalate ligands (Fig. 1a) [2]. To the best of our knowledge,
this complex represents the first example of binuclear association of metal-phthalate
units by hydrogen-bonding, and this represents a significant new synthon for use in
crystal engineering. All these structural and functional versatilities make phthalate
ligand an attractive building unit in the construction of metallopolymers and clusters.
In this report, we present the main approaches to design of 3d coordination
compounds based on the phthalate ligand, structural diversity displayed by the
synthesized complexes and discuss their properties.
Figure 1. Schematic representation of open and cyclic dimeric phthalates. M = Zn(II),
Co(II).
The synthetic strategy involved the selection of the metal ions and inert aromatic
ligand. Pyridine, pyrazine, imidazole and their derivatives (2,2′- and 4,4′-bipyridine, 1,10-
phenantroline) were used. Varying the nature of the reactants and synthetic conditions
a series of nickel(II), copper(II), manganese(II) and zinc(II) phthalate compounds have

been prepared [1-6]. The X-ray investigations show that the obtained complexes have
different architectures represented by monomeric, dimeric (Fig. 1) and polymeric (Fig.
2) compounds with diverse structural roles of two chemically equivalent carboxylic
groups.
These studies also revealed that the use of the different N-donor ligands leads to
formation of linear, zigzag or helical chains (Figs. 2, 3) in the polymers. These chains are
held together by strong or weak hydrogen bonds and/or aromatic-aromatic interactions,
to generate 2D or 3D networks.
Helical chains
Figure 3. A space-filling representation of the (a) right-handed chain and (c) left-handed
chain in [M(Pht)(4-MeIm)2(H2O)]n (M = Co(II), Cu(II); 4-MeIm = 4-methylimidazole).
1. S.G. Baca, I.G. Filippova, et all, Inorg. Chim. Acta, 357 (2004) 3419.
2. S.G. Baca, Yu.A. Simonov, et all, Inorg. Chem. Commun., 6 (2003) 685.
3. S.G. Baca, I.G. Filippova, et all, Inorg. Chim. Acta, 358 (2005) 1762.
4. S.G. Baca, S.T. Malinovskii, et all, J. Solid State Chem., 117 (2004) 2841.
5. S.G. Baca, I.G. Filippova, et all, Inorg. Chim. Acta. 344 (2003) 109.
6. S.G. Baca, Yu.A. Simonov, et all, Polyhedron. 20 (2001) 831.
Acknowledgement. This work was supported by SCOPES (7MDPJ065712.01/1) and
INTAS (No.03-51-4532)