Four divalent transition metal carboxyarylphosphonate compounds: Hydrothermal synthesis, structural chemistry and generalized 2D FTIR correlation spectroscopy studies

Four divalent transition metal carboxyarylphosphonates, [Ni(4,4′-bipy)H2L1(HL1)2(H2O)2]·2H2O 1, [Ni2(4,4′-bipy)(L2)(OH)(H2O)2]·3H2O 2, Mn(phen)2(H2L1)23 and Mn(phen)(HL2) 4 (H3L1=p-H2O3PCH2–C6H4–COOH, H3L2=m-H2O3PCH2–C6H4–COOH, 4,4′-bipy=4,4′-bipyridine, phen=1,10-phenanthroline) were synthesized under hydrothermal conditions. 1 features 1D linear chains built from Ni(II) ions bridging 4,4′-bipy. In 2, neighboring Ni4 cluster units are connected by pairs of H3L2 ligands to form 1D double-crankshaft chains, which are interconnected by pairs of 4,4′-bipy into 2D sheets. 3 exhibits 2D supramolecular layers via the R22(8) ringed hydrogen bonding units. 4 has 1D ladderlike chains, in which the 4-membered rings are cross-linked by the organic moieties of the H3L2 ligands. Additionally, 2D FTIR correlation analysis is applied with thermal and magnetic perturbation to clarify the structural changes of functional groups from H3L1 and H3L2 ligands in the compounds more efficiently.