Preparation, crystal structures and conformations of six complexes based on 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene

Abstract

Reaction of ligands (L or L_A) with metal salts affords six new metal complexes {[Mn(L)₃](ClO₄)₂}_n (1), [Cu(L)(SO₄)(H₂O)]·1.5H₂O (2), [Co(L)(L_A)(CH₃OH)₂]·2CH₃OH (3), [Co(L)(DMF)(NO₃)₂]_n (4), [Cd(L)(DMF)(NO₃)₂]_n (5) and [Cu(L)(DMF)(NO₃)₂]_n (6) (L = 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, L_A = fumarate). These complexes are structurally characterized by X-ray diffraction analyses. Analyses of crystal structures of complexes 1 and 2 show that 2D layers with metallomacrocycles are formed via ligand L and metal atoms (Mn(II) for 1 and Cu(II) for 2). The 2D layer with metallomacrocycles in complex 3 is formed via ligand L, fumarate groups and Co(II) atoms. 1D polymeric chains in complexes 4–6 are formed via ligand L and metal atoms (Co(II) for 4, Cd(II) for 5 and Cu(II) for 6). In the crystal packing of complexes 1–6, 3D supramolecular frameworks are formed via intermolecular weak interactions, including π–π interactions and C–H⋯π contacts. π–π interactions between benzimidazole rings are compared. The conformations of metal complexes based on dibenzimidazolyl bidentate ligands with flexible or semi-rigid linkers are described and compared. Additionally, the fluorescence emission spectra of ligand L and metal complexes and the magnetic properties of complexes 2–4 are reported.