Synthesis, X-ray structure, spectroscopic and magnetic properties of [bis(4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole- N′, N1)-(aqua)copper(II)]bis(hydrogensulfate)

Abstract

The synthesis, crystal structure, spectroscopic and magnetic properties of a five-coordinated mononuclear copper(II) compound with the ligand 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abbreviated as abpt) is reported. The compound |bis(4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole- N′, N1)(aqua)copper(II)|, |Cu(abpt) 2(H 2O)|(HSO 4) 2, crystallizes in the triclinic space group C2/ c, with a = 15.0685(9), b = 9.6108(5), c = 19.691(a) A ̊ , β = 93.611(5)°, V = 2846.03(3) A ̊ 3 and Z = 4 . The least-squares refinement based on 2028 significant reflections, with 1>2.5 σ 1, converged to R = 0.037 and R w = 0.043. The molecular structure consists of a mononuclear five-coordinated copper(II) cation. Two abpt ligands act as didentate chelating ligands with CuO(1) = 1.958(3), CuN(51) = 2.066(3) A ̊ and an N(1)-CuN(51) angle of 80.1(1)°. A water molecule is coordinated ( CuO(1) = 2.124(4) A ̊ ) . The Cu and O(1) are in special positions. The anions are the unusual hydrogensulfate (HSO 4) which have remarkably short acceptor hydrogen bonds to the same coordinating water molecule (O(1)–O(13) 1− x, y, 0.50− z) = 2.701(4), H(1)–O(13) (1−x, y, 0.50−z) = 1.74(4) A ̊ , O(1)–H(1)…O(13) (1− x, y, 0.50− z) = 167(4)°). Absorptions of the (low symmetry) hydrogen bonded hydrogensulfate anion can easily be found in the IR spectrum. The X-band powder electron paramagnetic resonance spectra show the usual rhombic spectrum for a copper(II) ion in a five-corrdination. Despite the strong hydrogen-bonding network no evidence for Cu…Cu exchange splittings are observed, in agreement with the magnetic susceptibility measurements over the temperature range 4.2–290 K, where the product of the magnetic susceptibility and the temperature remains constant at 0.325 cm 1 mol 1 K.