Synthesis and structural studies on three-dimensionally hydrogen-bonded metal perchlorate complexes with 1,3-dimethyllumazine and 1,3,6,7-tetramethyllumazine. Crystal structure of diaqua-bis(1,3,6,7-tetramethyl-pteridine2,4(1 H,3 H)-dione-O 4,N 5) copper(II) perchlorate dihydrate

Abstract

In aqueous solution, M II(ClO 4) 2 (Mn  Mn, Co, Ni, Cu, Zn, Cd and Hg) reacted with 1.3-dimethyllumazine 9DLM) and 1,3,6,7-tetramethyllumazine (DLMD) (lumazine = (1 H,3 H)-pteridin-2,4-dione) to give complexes with general formula Mp II(ClO 4) 2(LM) 2 · nH 2O. These compounds have been characterized by means of the analytical techniques (elemental analysis and thermogravimetry), spectral methods (IR, 13C and 1H NMR, UV-VIS-NIR, electron paramagnetic resonance) and magnetic measurements (77–290 K). Single-crystal X-ray diffraction studies have been made on the complex [Cu(DLMD) 2(H 2O) 2](ClO 4) 2·2H 2O. This compound crystallizes in the monoclinic system. P2 1/ c space group, Z = 2, with a = 8.764(1), b = 13.7932(8), c = 14.792(1) A ̊ , β = 116.02(1)°, V = 1602.9(3) A ̊ 3 , and R = 0.0728 for 4648 independent reflections and 224 parameters. The metal ion occupies an center and exhibits a distorted octahedral coordination. The coordination octahedron is flattened, the equatorial plane consisting of two N(5) and two O(4) atoms of pteridine ligands: the two axial sites are occupied by two oxygen atoms from the coordinated water molecules. The monomeric units together with non-coordinated water molecules and perchlorate anions are involved in a complex three-dimensional H-bonds network, the pteridine moieties being packed following planes roughly parallel to b axis, and perpendicular to the [5 4 21] direction. These planes are separated by a mean distance of 7.3 Å.