Dinuclear silver(I) complexes of bibracchial tetraimine Schiff base macrocycles derived from pyrrole-2,5-dicarbaldehyde

Abstract

The cyclocondensation of pyrrole-2,5-dicarbaldehyde and the amines N,N-bis(2-aminoethyl)- and N,N-bis(3-aminopropyl)-2-(aminomethyl)pyridine in the presence of silver(I) nitrate yielded homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes [Ag₂(L³)] 1 and [Ag₂(H₂L⁴)(ClO₄)₂]·CH₃CN 2. In 1 the Ag· · ·Ag separation is 2.748 Å. In 2 the silver atoms Ag(1) and Ag(2) are disordered over two sites with refined occupancies of 94.12 and 97.22% respectively. They are three-co-ordinate in the molecule having higher silver site occupancy and four-co-ordinate in that molecule having lower occupancy; the Ag· · ·Ag separations are 5.881 and 7.224 Å respectively. There are protonated imine nitrogen atoms present in both molecules and the structure contains a disordered acetonitrile of crystallisation.