A. Dylong, M. Sowa, W. Goldeman
Jun 17, 2014
Citations
0
Influential Citations
6
Citations
Journal
Polyhedron
Abstract
Imidazo[1,2-a]pyridin-2-ylacetic acid (HL, 1) and four ML2(H2O)2� 2H2O (M = Ni (2), Co (3), Mn (4), Cd (5)) complexes formed by its anion were synthesized, structurally characterized by single-crystal X-ray diffraction and investigated in terms of their thermal stability. In addition, magnetic properties of 2–4 are reported and the NIR–Vis–UV spectra of 2 and 3 are discussed in details. The crystal of 1 comprises 2D hydrogen bonded networks held in the crystal lattice by weak C–H ��� O and p–p contacts. The ML2(H2O)2� 2H2O complexes crystallize as isomorphous pairs (2, 3 and 4, 5) with slightly distorted hexa-coordinated environment around M(II) ion formed by two N,O-chelated imidazo[1,2-a]pyridin-2-ylacetate anions and two water molecules. In all 2–5, coordinated and lattice water molecules join discrete octahedral complexes into 2D hydrogen-bonded networks, held in the crystal lattice by weak C–H ��� O and p–p contacts. The Co(II) and Ni(II) complexes (2 and 3) are thermally less stable than Mn(II) and Cd(II) complexes (4 and 5). These differences are discussed in view of Hirshfeld surface analysis of reported compounds. The magnetic properties of 2 and 3 are largely determined by a tetragonal distortion of coordinated polyhedron, which stays in good agreement with observed and calculated transitions energies and their assignments in the electronic spectra of both compounds. Compound 4 displays almost ideal Curie–Weiss paramagnetism over the whole temperature range. Additionally, in all 2–4, weak magnetic exchange interactions mediated by H-bonds play a role with absolute values of J coupling parameter increasing in the order: Mn < Co < Ni.