Low‐dimensional compounds containing cyanido groups. Part XXXV. Structure, spectral, thermal and magnetic properties of a binuclear CuII–biquinoline complex with bridging and terminal dicyanamide ligands

From the system CuCl2–biq–NaN(CN)2 (biq is 2,2′‐biquinoline), the binuclear molecular complex bis(μ‐dicyanamido‐κ2N1:N5)bis[(2,2′‐biquinoline‐κ2N,N′)(dicyanamido‐κN1)copper(II)], [Cu2(C2N3)4(C18H12N2)2] or [Cu2(biq)2(dca)2(μ1,5‐dca)2] (1) [dca is dicyanamide, N(CN)2−] was isolated and characterized by crystal structure analysis, and spectral, thermal and magnetic measurements. IR spectroscopy confirmed the presence of the biq and dca ligands in 1. Its solid‐state structure consists of discrete centrosymmetric binuclear copper(II) units with double end‐to‐end dca bridges. Each CuII atom is in a distorted square‐pyramidal environment with the equatorial plane formed by two nitrile N atoms from bridging dca groups, one of the two N atoms of the chelate biq molecule and one nitrile N atom from a terminal dca ligand, whereas the second biq N atom occupies the axial position. Thermal decomposition of 1 in an air atmosphere proceeds gradually, with copper(I) cyanide being the final decomposition product. Magnetic measurements revealed the formation of alternating spin chains and a relatively strong exchange interaction within the binuclear units was also confirmed by Broken Symmetry DFT (density functional theory) calculations. The binuclear molecular complex [Cu2(biq)2(dca)2(μ1,5‐dca)2] (biq is 2,2′‐biquinoline and dca is dicyanamide) was isolated and characterized by structural analysis, and by spectroscopic, thermal and magnetic measurements.