Kinetics of the substitution reaction of thiocyanate with tetrakis (3-N-methylphyridyl)porphinecobalt(III).

The equilibrium constant for the first thiocyanate addition to Co(III)-tetra(3-N-methylpyridyl)porphine is a factor of two smaller than for the less basic 4-N-methylporphine isomer. This effect is primarily due to a larger Co-SCN dissociation rate constant for the 3-isomer.