Synthesis, crystal structure and spectroscopic investigations of heteronuclear Co(III)/Cu(II), Co(III)/Cd(II) and Fe(III)/Cd(II) 3D coordination polymers with 4-(2-aminoethyl)pyridine

Abstract

The cyanide complexes of transition metals with 4-(2-aminoethyl)pyridine (4aepy) of {[Cu(H2O)(µ-4aepy)Cu(µ-4aepy)2Cu(µ-4aepy)Co2(µ-CN)6(CN)6]·3H2O}n (1), (NH4)[Cd(µ-4aepy)2Co(µ-CN)2(CN)4]n (2) and (NH4)[Cd(µ-4aepy)2Fe(µ-CN)2(CN)4]n (3) were synthesized and investigated by vibrational (FT-IR and Raman), powder X-ray diffraction (PXRD), elemental and thermal analysis techniques. The crystal structures of the complexes have been determined by the single crystal X-ray diffraction (SC-XRD) patterns. The crystallographic analysis reveals that complex 1 crystallizes in the monoclinic system, space group P21, whereas; complexes 2 and 3 crystallize in the tetragonal system, space group P42/ncm. The asymmetric unit of heterometallic complex 1 consists of three Cu(II) ions, two Co(III) ions, four 4aepy ligands, twelve cyanide ligands, one aqua ligand and three non-coordinated water molecules. The asymmetric unit of heterometallic complexes 2–3 consists of one Cd(II) ion, one M ion [M = Co(III) in 2 and Fe(III) in 3], two cyanide ligands, half 4aepy ligand and one ammonium ion. Each Cd(II) ion is located at a center of symmetry and is coordinated by two nitrogen atoms by the cyanide ligands and by four nitrogen atoms by the 4aepy ligands. As a result, they show distorted octahedral coordination geometries. In complex 1, the intermolecular O–H⋯N, N–H⋯N, N–H⋯O and C–H⋯N hydrogen bonds and CN⋯π and π⋯π interactions play a crucial role in the architecture of 3D network. The intermolecular CN···π interaction between cyanide ligand and pyridine ring of the 4aepy ligand is the most striking feature of complex 1. Heterometallic complexes 2–3 have 3D coordination polymers.