Structural diversity of manganese(II) complexes containing 2,2 '-dipyridylamine and benzenedicarboxylates. Conformational analysis of tere-, iso- and phthalate ions: An experimental and quantum chemical approach

Abstract

Four novel manganese(II) complexes with 2,2'-dipyridylamine (dipya) and various benzenedicarboxylate, BDC, ligands as anions of phthalic (pht), isophthalic (ipht) and terephthalic (tpht) acids were hydrothermally synthesized, namely, [Mn(dipya)(pht)(H2O)](2) (1), [Mn(dipya)(ipht)](n) (2), [Mn(dipya) 2(tpht)](n) (3), and [Mn(dipya)(H2O)(4)](tpht) (4). All complexes were characterized by single-crystal X-ray diffraction, TG/DSC analysis and IR spectroscopy. The obtained complexes display a plenty of different structural features, including geometry of central metal atoms, BDC coordination modes and crystal packing. The coordination numbers of Mn(II) are different: 5 (in 2), 6 (in 3 and 4) and 7 (in 1). 3D networks in 1-4 are determined by strong non-covalent interactions. A survey of the Cambridge Structural Database for BDC complexes was performed in order to analyze orientation of COO groups. The energies of various BDC conformers were calculated by the second order Moller-Plesset perturbation theory and three hybrid HF/DFT methods with 6-311G** basis set. To explain different behavior, BDC ions were also examined by Localized Molecular Orbital Energy Decomposition and Natural Bond Orbital analyses. Experimental and calculated geometries are in agreement, showing that tpht and ipht anions prefer the planar conformation, while in pht anions COO groups are inclined and make complementary angles relative to the aromatic rings.