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)

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',Nl )(aqua)copper(II)], [Cu(abpt)(2)(H2O)](HSO4)(2), crystallizes in the triclinic space group C2/c, with a=15.0685(9), b=9.6108(5), c=19.691(1) Angstrom, beta=93.611(5)degrees, V=2846.0(3) Angstrom(3) and Z=4. The least-squares refinement based on 2028 significant reflections, with I>2.5 sigma(1), converged to R=0.037 and R-w=0.043. The molecular structure consists of a mononuclear five-coordinated copper(LI) cation. Two abpt ligands act as didentate chelating ligands with Cu-N(I)=1.958(3), Cu-N(SI)=2.066(3) Angstrom and an N(1)-Cu-N(51) angle of 80.1(1)degrees. A water molecule is coordinated (Cu-O(1)=2.124(4) Angstrom). The Cu and O(1) are in special positions. The anions are the unusual hydrogensulfate (HSO;) 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) Angstrom, O(1)-H(1)... O(13) (1-x, y, 0.50-z)=167(4)degrees). Absorptions of the (low symmetry) hydrogen bonded hydrogensulfate anion can easily be found in the LR spectrum. The X-band powder electron paramagnetic resonance spectra show the usual rhombic spectrum for a copper(II) ion in a five-coordination. 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(3) mol(-1) K. (C) 1998 Elsevier Science S.A.