Coordination polymers and monomers based on new aminocarboxylate ligands: A cadmium(II) polymer containing dimeric aqua-bridged cadmium complex governed by polymeric chain

The synthesis and characterization of novel coordination polymers [Co(HCCB)(H2O)2]n (1), [Zn(HCCB)(H2O)2]n (2), {[Cd(HCCB)2]·0.5[Cd(μ-H2O)(H2O)4]2}n (3) and [Cu(HCCB)(H2O)2]n (4) based on 3-(carboxymethylamino)-4-chlorobenzoic acid (H3CCB) and mononuclear complexes [Cu(HBCCB)(H2O)]·H2O (5), [Co(HBCCB)(H2O)]·H2O (6), [Zn(HBCCB)(H2O)] (7) and [Cd(HBCCB)(H2O)] (8) containing 3-bis(carboxymethylamino)-4-chlorobenzoic acid (H3BCCB) have been described. The compounds under investigation have been characterized by elemental analyses, spectral studies and structures of 1–3 and 5 determined crystallographically. Structural data of 1 and 2 revealed that the deprotonated HCCB2− bridges metal centers leading to a double stranded 1D chain. On the other hand, the HCCB2− coordinated thorough carboxylate oxygen and amino nitrogen in 3 to afford a 1D chain whose charge neutrality is maintained by inclusion of aqua-bridged dimer [{Cd(μ-H2O)(H2O)4}2]4+. Strong Cu⋯Cl interaction (2.754 Å) in 5 imposes a coordination geometry that is half-way between the square planar and square pyramidal. The H3CCB, H3BCCB and 1–3 and 5 are fluorescent at rt. Thermal studies (TG and DSC) on 1–3 suggested higher stability of 2 relative to 1 and 3 [ΔHf (kcal/mol), ΔSf = 152.17, 0.60, 1; 195.56: 0.86, 2; 69.33:0.36, 3].