Intermediate (S=1) spin state in five-coordinate cobalt(III): Magnetic properties of N-o-hydroxy-benzamido-meso-tetraphenylporphyrin cobalt(III), Co(N-NCO(o-O)C6H4-tpp)

The crystal structures of paramagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4),N-1,N-2,N-3,N-5,kappa O-2) cobalt(III) [Co(N-NCO(o-O)C6H4-tpp); 2] (S = 1) and diamagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4), N-1, N-2, N-3, N-5, kappa O-2) gallium( III) chloroform center dot methanol solvate [Ga(N-NCO(o-O)C6H4-tpp)center dot 0.5CHCl(3)center dot MeOH; 3 center dot 0.5CHCl(3) center dot MeOH] (S = 0) were determined. The coordination sphere around Co(III) in 2 [or Ga(III) in 3 center dot 0.5CHCl(3)center dot MeOH] is described as five-coordinate distorted trigonal bipyramid (DTBP) with O(1), N(1)and N(3) [or O(2), N(1), N(3)] lying in the equatorial plane for 2 [or 3 center dot 0.5CHCl(3)center dot MeOH]. The magnitude of axial (D) zero-field splitting (ZFS) for the Co(III) (S = 1) in 2 was determined as approximately 107 cm(-1) by paramagnetic susceptibility measurements. The compound (2) reacts in donor solvent such as pyridine to form six-coordinate diamagnetic species of the type Co(N-NCO(o-O) C6H4-tpp)(py) (4), whose H-1 NMR spectra can be interpreted as for Co(III) in an octahedral environment.