Heterometallic carboxylate complexes are of paramount interest in pure and applied coordination chemistry. Despite that plurality of such type compounds have been published to date, synthetic aspects of their chemistry often remain in the shadow of intriguing physical properties manifesting by these species. Present review summarizes reliable data on direct synthesis of low nuclearity molecular compounds as well as coordination polymers on their base with carboxylate-bridged {M₂Mg} (M = Co²⁺, Ni²⁺, Cd²⁺), {M₂Li₂} (M = Co²⁺, Ni²⁺, Zn²⁺, VO²⁺), {M₂Ln₂} and {M₂Ln} (M = Cu²⁺, Zn²⁺, Co²⁺) metal cores. Structural features and stabilization factors are considered and principal outcomes are confirmed by quantum-chemical calculations. Particular attention is paid to consideration of ligand-exchange reactions that allow controllable modification of heterometallic metal core under mild conditions giving diverse molecular complexes with modified ligand environment or Metal-Organic Frameworks with permanent porosity.

Varying the temperature of the reaction of [{Cd(pfb)(H₂O)₄}⁺_n·n(pfb)⁻], [Ln₂(pfb)₆(H₂O)₈]·H₂O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)₅(phen)]_n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb₂Cd₂(pfb)₁₀(phen)₂] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln₂Cd₂ fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln₂Zn₂ [Ln₂Zn₂(pfb)₁₀(phen)₂]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd₂Zn₂(pfb)₁₀(H₂O)₂(phen)₂]·4MeCN (VII). A new molecular EuCd complex [Eu₂Cd₂(pfb)₁₀(phen)₄]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

A series of the cadmium and zinc carboxylate complexes with anions of pentafluorobenzoic (HРfbz) and 2,3,4,5-tetrafluorobenzoic (HТfbz) acids and N-donor ligands (1,10-phenanthroline (Phen) and quinoline (Quin)), [Cd(Pfbz)₂(Phen)]_n (I), [Cd(Рfbz)₂(Рhen)₂]·2MeCN (II), [Zn(H₂O)-(Рfbz)₂(Рhen)] (III), [Zn₂Cd(Рfbz)₆(Рhen)₂]⋅2C₆H₆ (IV), [Cd₂(H₂O)₂(Tfbz)₄(Рhen)₂] (V), [Cd₂-(H₂O)₂(Tfbz)₄(Quin)₂] (VI), and [Cd(Tfbz)₂(Phen)₂]⋅HTfbz (VII), is synthesized. The structures of new complexes I–VII are determined by X-ray diffraction analysis (CIF files CCDC nos. 1871300, 2005461, 2005462, 2005464, 2005466, 2005465, and 2005459, respectively). The majority of the synthesized compounds is typical of intramolecular stacking interactions between the coordinated molecules of the aromatic N-donor ligands and fluorinated substituents of the carboxylate anions. These interactions lead to the formation of unusual compounds, which are different in the cases of pentafluorobenzoates and tetrafluorobenzoates, in particular, coordination polymer I and binuclear complexes V and VI with coordinated water molecules. The synthesized zinc and cadmium compounds differ in structure and composition.

New trinuclear Cd–Ln molecular complexes [EuCd₂(O₂CC₆F₅)₆(NO₃)(Bipy)₂] (I, Bipy is 2,2'-bipyridine) and [LnCd₂(Bzo)₆(NO₃)(Phen)₂] · 4MeCN (Ln = Tb (II), Eu (III), Bzo is anion of 3,5-di-tert-butylbenzoic acid, Phen is 1,10-phenanthroline) are studied. Their structures are determined by X-ray structure analysis (СIF files CCDC nos. 1938125 (I), 1938124 (II)) or by X-ray diffraction analysis (III), and the photoluminescence properties are studied. The reactions of complexes I and II with terephthalic acid (H₂Bdc) are accompanied by the destruction of the heterometallic molecules to form 2D coordination polymers [Cd₃(Bbdc)₃(Bipy)₂]_3n · 4nMeCN · nH₂O (IV) and [Cd₂(Bdc)₂(Phen)₂]_n · 2nDMF (V) (СIF files CCDC nos. 1938126 and 1937492, respectively).

The influence of arene/perfluoroarene ratio on the structure and crystal packing of carboxylate and nitrate-carboxylate complexes of Cd, Cd-Tb and Cu was studied, using the following compounds: pentafluorobenzoate (pfb) and 4-allyl-2,3,5,6-tetrabenzoate (Afb) anions and 1,10-phenanthroline (phen) composition [Cd(pfb)₂(phen)]_n (1), [Cd(NO₃)(pfb)(phen)]_n (2), [Tb₂Cd₂(pfb)₁₀(phen)₂]. 3MeCN]_n (3), [Tb₂Cd₂(NO₃)₂(pfb)₈(phen)₂^.1.5MeCN]_n (4), [Cu₂(Afb)₄(phen)₂] (5), [Cu₂(NO₃)₂(Afb)₂(phen)₂] (6). It is shown that the main contribution to the stabilization of the crystal packing of coordination polymers 1–4 and molecular binuclear complexes 5 and 6 can be attributed to non-covalent π···π, C-H···F, and C-F···π interactions. It was found that the partial exchange of pfb or Afb anions on compact NO₃⁻ anions leads to a decrease in steric hindrance, a more efficient overlap of aromatic fragments, and a significant change in the geometry of complexes. Synthesized compounds were characterized by X-ray diffraction analysis, IR spectroscopy, and CHN analysis. The thermal stability of complexes 1 and 2 was studied. Non-covalent interactions were analyzed using the Hirshfeld surface method.

The antiproliferative and antibacterial effects of copper(ii) complexes with the same ligand environment have been studied depending on the anion.