Magnetic and spectral properties of two five-coordinate Lewis-base adductsof cobalt(II) Schiff-base complexes with a N3O2 ligand environment

Two new five-coordinate Lewis-base adducts of cobalt(II) N2O2 Schiff-base c omplexes, [Co(Salpad)(2)(t-MeStpy)] and [Co(H-2(fsa)(2)phn)(t-MeStpy)]. 0.5 H(2)O (where H(Salpad)= 2-[N-(4-phenylaminophenyl)formimidoyl]phenol, H-4(f sa)(2)phn = N,N'-o-phenylenebis(3-carboxysalicylaldimine), and t-MeStpy = t rans-1-(4-methylphenyl)-2-(4-pyridyl)ethene), have been synthesized in orde r to investigate the influence of the in-plane donor atom topology on the s pin-state of the cobalt(II) ion. The compounds have been characterized by a nalytical and spectroscopic methods. The spin-state behavior of cobalt(II) was investigated by variable-temperature magnetic susceptibility measuremen ts over the temperature range 10-380 K. For [Co(Salpad)(2)(t-MeStpy)] the m agnetic data indicate a spin-quartet ground state which can be described us ing an axial spin Hamiltonian (D = 16.57 cm(-1) g = 2.39 for CoN2O2N') with additional temperature-independent paramagnetism (N alpha = 360 x 10(-6) c m(3) mol(-1)). The compound [Co(H-2(fsa)(2)phn)(t-MeStpy)]. 0.5H(2)O underg oes a thermally-induced S = 1/2-->S = 3/2 spin equilibrium at high temperat ures. The magnetic properties of the four-coordinate [Co(Salpad)(2)] precur sor are also reported here. (C) 2000 Elsevier Science Ltd. All rights reser ved.