Coordination polymersviaself-assembly of silver(i) and cis-bis-nitrile-oxa-bowl derivatives

Abstract

A series of silver(I)-based coordination polymers (AgCPs) have been synthesized using three new nonchelating cis-bis-nitrile derivatives of oxa-bowls, L1–L3, as ligand components. The ligands are designed to provide conformational restrictions as well as semi-rigid directionality to the coordination vectors extended from the nitrile functionalities. The steric bulks around the oxa-bowl spacer moieties are gradually escalated to study their influence on the topologies of the ensuing AgCPs. Two silver salts i.e. AgSbF₆ and AgPF₆ are used to check the influence of anions on the structural architectures. Ziz-zag-sheet type 2-D AgCPs are formed with the ligands L1 and L2 possessing less steric bulk. All the metal centres are found to be tetracoordinated by nitrile-nitrogens of the same sheet giving distorted-bisphenoidal geometries. Additional short interactions of the silver(I) centres of a given sheet with the oxygen of the oxa-bowls belonging to the neighbouring stacked sheets are observed. The bulky ligand L3 behaved differently where the metal centres are tetracoordinated although only two of the ligating units are derived from the nitrile nitrogens and the remaining two are from, depending upon the counter anion, the counter anion/oxygen of oxa-bowls or two water molecules. The overall arrangements in the AgCPs of L3 are of the 2-D carpet type (for SbF₆⁻ ion) composed of interconnected chains, and 1-D ladder type (for PF₆⁻ ion) constructed from two chains. Cation–π interactions are found between the aromatic part of L3 of a given chain and the silver(I) of the adjacent chain that are interdigitated.