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

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.