Coligand-directed synthesis of five Co(ii)/Ni(ii) coordination polymers with a neutral tetradentate ligand: syntheses, crystal structures, and properties

Abstract

The solvothermal reactions of 1,1′-oxybis[3,5-di-4-pyridine]-benzene (L) and transition metal cations (Co and Ni) afford five novel coordination polymers in the presence of flexible bridging ligands (4,4′-H₂nba = 4,4′-dicarboxydiphenylamine, H₂cam = D-camphoric acid, 4,4′-H₂sdb = 4,4′-sulfonyldibenzoic acid, H₂chdc = 1,4-trans-cyclohexanedicarboxylic acid), namely {[Co₂L₂(OH)₂(nba)]·2DMF}_n (1), {[CoL(cam)(H₂O)]}_n (2), {[Co₃(L)(4,4′-sdb)₃(H₂O)]·1.5CH₃CN·4H₂O}_n (3), {[Ni₃(L)(4,4′-sdb)₃(H₂O)]·1.5CH₃CN·4H₂O}_n (4), and {[Ni₂L₂(chdc)₂(H₂O)₂]·(H₂O)₃}_n (5) (DMF = N,N-dimethylformamide). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, and powder X-ray diffraction. Complex 1 reveals a 2-fold interpenetrating three-dimensional (3D) framework with the Schläfli symbol {4·8·10⁴}{4·8·10} topology. Compound 2 crystallizes in the achiral space group with the D-camphorate ligand racemized. Compounds 3 and 4 reveal similar structure with the {3·4⁴·6}{3²·4⁸·5⁹·6⁹} topology based on a linear trinuclear building block M₃(OOCR)₆ (M = Co(II) or Ni(II)). Compound 5 is a wavy sheet, where both carboxylate and L ligands act as bidentate ligands. Moreover, UV-Visible absorption spectra of complexes 1–3, 5 and the magnetic properties of 3 have been investigated.