Synthesis, structural and spectroscopic study of polymeric copper(I) thiocyanato complexes [Cu(NCS)L] n (L=methyl nicotinate and ethyl nicotinate) and [HL][Cu(NCS) 2] (HL=H-ethyl isonicotinate)

Abstract

Three new copper(I) thiocyanato complexes [Cu(NCS)L] n (L=methyl nicotinate 1, ethyl nicotinate 2), and [HL][Cu(NCS) 2] (HL=H-ethyl isonicotinate 3), have been prepared and characterized by spectroscopic and crystallographic methods. All three complexes display MLCT transitions in the visible region, as well as visible solid state emission spectra at room temperature. Their IR spectra are measured and discussed. In the structure of 1 each copper atom links two S atoms from two μ-S,S,N thiocyanato ligands and two nitrogen atoms from a pyridine nucleus and from a third μ-S,S,N thiocyanate group; the two S atoms bind another copper atom forming a Cu 2S 2 cyclic unit. The ladder propagates along the a axis of the unit cell. The structure of 2 features CuS 2N 2 coordination with approximate tetrahedral environment, μ-S,S,N bridging thiocyanate groups giving rise to corrugated layers at y=1/4. Complex 3 consists of an N-protonated ethyl isonicotinate cation and a polymeric [Cu(NCS) 2] − anion. Each trigonal planar copper atom in the anion is coordinated by two S atoms from a μ-S,N thiocyanate bridge and a terminal S-thiocyanate group, and the third site is occupied by the end nitrogen of a μ-S,N thiocyanate bridge. The terminal NCS group forms a hydrogen bond of the type N–H⋯N with an N–H group of the [HL] + cation. The planar ribbon which runs in the a direction is further stabilized by N–H⋯O hydrogen bonds.