Synthesis and crystal structures of silver(i), palladium(ii), zinc(ii) and cobalt(ii) complexes of the ditoptic ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene

Abstract

Complexes of 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (bitmb) with silver(I), palladium(II), zinc(II) and cobalt(II) salts have been characterized in the solid state by single-crystal X-ray analysis. The topology of the structures in the solid state, namely finite versus infinite, is found to dependent on the coordination geometry of the metal atoms. For Ag(I) (linear N₂ geometry) and Pd(II) (square-planar N₄), crystallization with bitmb produces an M₂L₂ cyclic dimer of composition [Ag₂(bitmb)₂](PF₆)₂·2CH₃CN (1) or an M₂L₄ cage complex [Pd₂(bitmb)₄]Cl₄·8H₂O·1.5CH₃CN (2). For Zn(II) (tetrahedral N₂O₂) or Co(II) (octahedral N₆), crystallization with bitmb produces a 1D zigzag chain network of [Zn(bitmb)(CH₃CO₂)(C₂H₅OH)](OH) (3) or an infinite 1D poly-macrocycle chain network [Co(bitmb)₂(CH₃CN)₂](ClO₄)₂·2C₂H₅OH (4). It is also found that the conformations of the bitmb ligand are obviously controlled by the coordination number of the central metal ions. When coordinated with silver(I) (coordination number n = 2), palladium(II) (n = 4) or zinc(II) (n = 4), bitmb shows a cis,cis-conformation, but in the case of cobalt(II) (n = 6), bitmb shows a trans,trans-conformation. The results also show that the π⋯π interactions together with the hydrogen bonds co-affect inorganic supramolecular formation.