Coordination chemistry of bis(2-pyridylimine) ligands with Ag(I): formation of two structurally different coordination polymers and one metallocycle controlled by linker and the solvent system

Abstract

Reaction of equimolar amounts of AgClO4 and bis[4-(2-pyridylmethyleneamino)phenyl] methane (L1) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L2) in a 1:1 solvent mixture of CH3CN and CH2Cl2 leads to the formation of two infinite coordination polymers of the composition {[Ag(L1)]ClO4·CH3CN}n (1) and {[Ag(L2)]ClO4·CH2Cl2}n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N4 coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO4− anions and solvent molecules forming 2-D layers. Additional π–π and CH–π interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag2(L2)2](ClO4)2·CH3OH (3), has been formed by reaction of AgClO4 with L2 when CH2Cl2 in the solvent mixture was replaced by CH3OH. Again each Ag(I) has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face π–π interactions allow a 3-D packing arrangement.