Synthesis, crystal structure and properties of copper(II) complexes with different axial ligands and substituted pyrazoles

Abstract

This paper presents the synthesis, crystal structure and properties of three copper(II) complexes with different axial ligands and substituted pyrazoles, [Cu(pzR)4(X)2] (X=Cl− and R=H for (1), X=Cl− and R=n-But for (2), X=ClO4− and R=n-But for (3); pzR=3-substituted pyrazole). The structures of all the complexes were determined by X-ray diffraction. The complex [Cu(pz)4Cl2] (1) crystallizes in the monoclinic system, space group C2/c, a=13.658(5)Å,b=9.179(3)Å,c=14.724(6)Å,β=116.843(6)°, and Z=4. The complex [Cu(pz3-But)4Cl2] (2) crystallizes in the triclinic system, space group p1̄ (No. 2), a=10.733(2)Å,b=11.290(2)Å,c=14.726(3)Å,α=86.93(3)°, β=89.58(3)°, γ=89.44(3)°, and Z=2. The complex [Cu(pz3-But)4(ClO4)2] (3) crystallizes in the monoclinic system, space group P21/c (No. 14), a=11.934(2)Å,b=23.422(5)Å,c=14.027(3)Å,β=94.72(3)°, and Z=4. The Cu(II) ion in each complex is coordinated to four pyrazole nitrogen atoms and two Cl− or two oxygen atoms of ClO4−, to form an elongated octahedron. The two Cl− or two oxygen atoms of ClO4− are located at axial positions and the four nitrogen atoms of pyrazole are located at equatorial positions. The average Cu(II)–N bond lengths are observed to be 2.010, 2.015 and 1.997Å for 1, 2 and 3, respectively. The average Cu(II)–X bond lengths are observed to be 2.839 , 2.849 and 2.490Å for 1, 2 and 3, respectively. In these complexes, each Cl− or O has been connected by weak intramolecular hydrogen bond with the hydrogen atom of two pyrazoles. The UV–Vis and ESR spectroscopic results are consistent with the crystallographic results and perfectly related to each other.