Thieno[3,2-c]Pyridine Complex of Ni(II) with Unusual Magnetic Properties

Abstract

Thieno[3,2-c]pyridine (thpy) has been prepared in a free form and embodied into the [Ni(thpy) 2 (H 2 O) 2 (ac) 2 ] complex as a ligand. The X-ray structure shows a molecular structure of the complex with Ni−O(ac) = 2.059, Ni−OH 2 = 2.078, and Ni−N(thpy) = 2.124 Ǻ. Electronically the complex behaves like a compressed tetragonal bipyramid. The molecular units are linked into a complex system of hydrogen bonds. Two units show a π−π stacking of the aromatic rings (3.8 Ǻ). There are planes of tetragons formed of the nickel atom with the in-plane Ni...Ni separation of 7.74 Ǻ and the inter-plane Ni...Ni contacts at a = 9.65 Ǻ. The effective magnetic moment shows a gradual decrease on cooling from the room temperature and an abrupt drop below 20 K typical for the zero-field splitting of S = 1 systems. Above the room temperature the effective magnetic moment shows anomalies -a decrease and then an increase.