Five copper(ii) metal–organic coordination complexes with micro-channels based on flexible bis(imidazole) and carboxybenzaldehyde ligands; structural influence of experimental conditions on their frameworks

Abstract

Five new copper(II) metal–organic coordination complexes, [Cu₂(1,2-bix)₂(L)₄] (1), [Cu(1,3-bix)(L)₂]_n·nCH₃OH·3H₂O (2), [Cu(1,3-bix)(L)₂]_n·nH₂O (3), [Cu₅(1,3-bix)₂(L)₆(NO₃)₂(H₂O)₂(OH)₂]·2H₂O (4) and [Cu(1,4-bix)(L)₂]_n (5), have been synthesized using 4-carboxybenzaldehyde (HL) and 1,n-bis(imidazol-l-ylmethyl)benzene (1,n-bix; n = 2, 3, 4) as ligands. These complexes were structurally characterized by single-crystal X-ray crystallography and further characterized by FT-IR spectroscopy and thermogravimetric analysis (TGA). Complex 1 is a symmetrical binuclear structure, and in compound 2 the 1D ladders are entangled through π–π stacking interactions to generate a 3D network with one-dimensional micro channel. A 3D coordination framework 2 converted to network 3 by just increasing the reaction temperature. Metal–organic polymer 3 is comprised of 1D corrugated double chains structure. Complex 4 has a pentanuclear (Cu₅) cluster structure and compound 5 shows a 1D zigzag chain. The magnetic properties of the complexes 1 and 3 are reported briefly.