Construction of Cd(II)–ferrocenesuccinate coordination complexes via changing adjuvant ligands and anions

Seven Cd(II)–ferrocenesuccinate coordination complexes with the formulas [Cd(η2-FcCOC2H4COO)2(pbbbm)]2 (1), [Cd(η2-FcCOC2H4COO)(pbbbm)Cl]2 (2), [Cd(η2-FcCOC2H4COO)(pbbbm)I]2 (3), {[Cd(η2-FcCOC2H4COO)2(btx)2]2(CH3OH)0.5} (4), [Cd(η2-FcCOC2H4COO)2(bix)]2(H2O) (5), {[Cd(η2-FcCOC2H4COO)(bbbm)1.5Cl] · (CH3OH)0.5}n (6), and {[Cd(η2-FcCOC2H4COO)(mbbbm)Cl] · (H2O)2.75}n (7) [pbbbm = 1,4-Bis(benzimidazole-1-ylmethyl)benzene), btx = 1,4-bis(triazol-1-ylmethyl)benzene), mbbbm = 1,3-bis(benzimidazole-1-ylmethyl)benzene), bix = 1,4-bis(imidazol-1-ylmethyl)benzene, bbbm = 1,1-(1,4-Butanediyl)bis-1H-benzimidazole)] have been synthesized and characterized. Single-crystal X-ray analysis reveals that complexes 1–5 are all dimers and bridged by pbbbm, btx and bix, respectively. But the five complexes present some differences in their dimeric conformations, which can be ascribed to the impacts of adjuvant ligands and counter anions. In contrast to complexes 1–5, both 6 and 7 are of 1-D structures (with the same counter anions), and the former is double ladder-like structure only bridged by bbbm, while the latter is chain-like structure bridged by chlorine anions and adjuvant ligand mbbbm. Notably, various π–π interactions are found in complexes 1–7, and they have significant contributions to molecular self-assembly processes. The electrochemical studies of complexes 1–7 in DMF solution display irreversible redox waves and indicate that the half-wave potentials of the ferrocenyl moieties in these complexes are all shifted to positive potential compared with that of ferrocenesuccinate.