Dicopper complexes derived from 4-amino-2,1,3-benzothiadiazole with versatile co-ordination number and geometry

摘要

Three dicopper complexes of 4-amino-2,1,3-benzothiadiazole (abt) have been isolated and structurally characterized. The reaction of [Cu(CH3CN)(4)][PF6] with abt in THF produced [Cu-2(abt)(2)(CH3CN)(4)][PF6](2) . C6H12 1 . C6H12, while in acetone, Cu-I template Schiff-base condensation of the amino group of abt with solvent was found to give [Cu-2(ibt)(2)(CH3CN)(4)][PF6](2) 2 (ibt = 4-isopropylideneamino-2,1,3-benzothiadiazole). In complex 1 there are two crystallographically independent monomeric units in each of which Cu-I is co-ordinated by one N atom on the ring of abt and two acetonitrile molecules; two units are linked to each other by weak binding of the amino group of abt with Cu-I to give a cyclic dinuclear complex. In complex 2 tetrahedral Cu-I centers are bridged by two ibt molecules in a head-to-tail fashion as in 1. Both 1 and 2 have the same metallocyclophane skeletons showing an intramolecular stacking interaction between two parallel aromatic rings and a considerably long Cu ... Cu separation [7.220(5) Angstrom for 1, 6.542(4) Angstrom for 2]. Following the same synthetic strategy as used for the synthesis of 2 another dicopper complex [Cu-2(ibt)(2)][ClO4](2) 3 was obtained, which presents a structural contrast with 2: two Cu-I centers are linearly co-ordinated by two ibt molecules in a head-to-head arrangement which leads to a twisted conformation with a shorter Cu ... Cu distance of 2.699(2) Angstrom. In addition, H-1 NMR measurements reveal that 2 can also be formed directly from 1 in acetone solution. [References: 38]