Perceptive Approach in Assessing Rigidity versus Flexibility in the Construction of Diverse Metal–Organic Coordination Networks: Synthesis, Structure, and Magnetism

Abstract

By associating rigidity and flexibility within the organic building blocks, we have synthesized four new metal–organic coordination polymers, formulated as {Co(ADA)(bpbix)}n·nH2O (1), {Co(ADC)(bpbix)}n (2), {Co(ADA)(bpim)}n·nH2O (3), and {Co2(ADC)2(bpim)}n (4), by using the adamantane based flexible dicarboxylate ligand H2ADA and rigid dicarboxylate ligand H2ADC along with flexible bis-imidazole linker, bpbix and rigid bis-imidazole linker, bpim as coligands (where H2ADA = 1,3-adamantanediacetic acid; H2ADC = 1,3-adamantanedicarboxylic acid; bpbix = 4,4′-bis((1H-imidazol-1-yl)methyl)biphenyl; bpim = 4,4′-di(1H-imidazol-1-yl)biphenyl). Compounds 1–4 have been characterized by routine elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis and unambiguously by single crystal X-ray diffraction analysis. In the crystal structures of these compounds 1–4, diverse architectures, have been observed, formation of which is facilitated by the conformation rigidity and flexibility of the ligands. The role of the interchanging between flexibility and rigidity of both the adamantine- and bis-imidazole-based ligands in assessing the diversity in the resulting architectures has been discussed. In addition, temperature-dependent magnetic studies for the compounds 1, 3, and 4 have been described.