A 2D network silver coordination polymer with the multimodal ligand 2-pyrazyl methyl ketazine

Abstract

A two-dimensional coordination polymer {Ag(PMK)(OTf)·MeCN} n (1) based on multi-modal bridging ligand, namely N,N′-bis[1-(pyrazin-2-yl)ethylidene]-hydrazine or 2-pyrazyl methyl ketazine (PMK), and AgOTf salt has been synthesized and characterized by ESI-MS, 1H-NMR, ATR-IR, and single crystal X-ray diffraction. The PMK shows distinct binding sites, both chelating and monodentate, and bridging modes in 1 where each silver(I) centre is five coordinate, and bound to one bidentate pyrazylketimine and a monodentate pyrazine through the peripheral N atom from another ligand, and also a bridging pyrazine through the peripheral N atom of the adjacent chelating unit from another ligand, and to triflate anion to feature one-dimensional infinite chain. The triflate anions have effectively increased the 1D coordination polymers to a 2D network via H-bonding interactions. These 2D planes are stacked together building up channels (1D tube) in which the acetonitrile solvent molecules reside and form very weak contacts with the triflates and the pyrazylketimine units via C–H···O and C–H···N, respectively. In addition, the fluorescent spectrum of 1 in the solid state exhibits two emission maxima at 496 and 522 nm. The ESI-MS, IR, and 1H-NMR confirm the structure. Self-assembly reaction of multimodal ligand (PMK = N,N′-bis[1-(pyrazin-2-yl)ethylidene]-hydrazine) and AgOTf gives unprecedented one-dimensional coordination polymer {Ag(PMK)(OTf)·MeCN} n (1) with distinct coordination modes of the ligand and the solid state fluorescence spectrum. The triflate anions which are weakly coordinated to silver(I) centres in 1, cross-link the chains by intermolecular hydrogen bonding interactions into a 2D network. These 2D planes are stacked together building up square channels (1D tubes) in which the acetonitrile solvent molecules reside.