New mixed-ligand copper(II) complex as a model for the metal-binding role of 2-aminomethylbenzimidazole, a chelating anchor group used in ion-exchanger polymers. Synthesis, molecular and crystal structure and properties of (2-aminomethylbenzimidazole)(iminodiacetato)copper(II), [Cu(IDA)(2AMB zImH)

Abstract

(2-Aminomethylbenzimidazole)(iminodiacetato)copper(II), [Cu(IDA)(2AMBzImH)] = I, has been prepared and studied by spectral, magnetic, thermal and X-ray diffraction methods. In the crystal, all N-H ligand groups in I are involved in hydrogen bonding formation with O II)A atoms of three neighbouring molecules. This new mixed-ligand copper(II) complex crystallizes in the monoclinic system, space group P2 1 n (a = 7.900(1), b = 18.679(6), c = 9.229(1), β = 110.82(1)°, Z = 4, R = 0.047, R w = 0.137) . One carboxylate O and the N atoms of IDA and both N atoms of 2AMBzImH define a distorted square. The flattened-square base pyramidal coordination (type 4+1) of the Cu(II) atom is accomplished by a longest apical Cu - (IDA) bond. The Cu(II) chelation by 2AMBzIrnH in I implies the coordination of the N-heterocyclic donor in trans to the CuN(II)A) bond. That imposes a fac-chelatiog role to IDA beforehand reported for mixed-ligand Cu(II) complexes having a 1: 1: 2 Cu: IDA : N-heterocyclic donor ratio, in clear contrast with the typical mer-chelatiog IDA role of complexes with a 1 :1 : 1 Cu: IDA : N-heterocyclic donor ratio. The structure of [Cu(IDA)(2AMBzImH)] agree well with the results and proposals of a recent study [9] on synthetic ion exchangers having ω-aminoalkylbenzimidazole anchor groups, in which is proved that the exchanger with 2AMBzImH N-anchored groups display fast-uptake and regeneration kinetics and good selectivity for Cu 2+ ions.