Syntheses, Spectral and Thermal Studies, and Crystal Structure of 1,10-Phenanthroline and Picolinamide Complexes of Cobalt(II) Squarate

Abstract

Preparations, crystal structures, thermal properties, IR and UV/vis spectroscopic studies and magnetic moments of tris(1,10-phenanthroline) cobalt(II) squarate octahydrate, [Co(phen)<inf>3</inf>]sq·8H<inf>2</inf>O (1) and diaquabis(picolinamide)cobalt(II) squarate, [Co(H<inf>2</inf>O) <inf>2</inf>(pia)<inf>2</inf>]sq (2) are described. 1 crystallizes in the monoclinic system, space group P2<inf>1</inf>/c, with a = 10.9832(5), b = 21.4569(12), c = 17.0649(7) Å, β = 98.159(3)° and Z = 8, while 2 crystallizes in the triclinic system, space group P1, with a = 6.9624(9), b = 7.9224(11), c = 8.0501(11) Å, α = 107.404°, β = 93.340(11)°, γ = 93.266° and Z = 1. Both 1 and 2 have slightly distorted octahedral coordination geometry, involving six N atoms from bidentately chelating phen ligands and trans-[CoN<inf>2</inf>O<inf>4</inf>] coordination geometry, in which the Co atom is located at a center of symmetry. There are significant hydrogen-bonding interactions in the structure of 1. The squarate dianions are linked to the eight solvent water molecules by means of hydrogen-bonding interactions. Moreover, there are links between the complex cation and the squarate dianion via C-H⋯O hydrogen bonds. These interactions hold the crystal structure of 1 in a three-dimensional network, while O-H⋯O, N-H⋯O, weak π⋯π and π⋯ring interactions lead to a three-dimensional crystal structure for 2. The thermal decomposition pathways of 1 and 2 have been investigated by the help of thermal analyses data (TG and DTA). © 2006 Verlag der Zeitschrift für Naturforschung.