Spin state in (porphinato)iron(III) complex. A spin-crossover complex withtwo magnetically distinct sites

The results of low temperature X-ray determination, Mossbauer and magnetic measurement of spin-crossover (isothiocyanato) (porphinato) iron(III) hemip yridine are reported. The features in 77 K Mossbauer spectrum include two d oublers, one with a quadrupole splitting (Delta E-Q) of 1.961 mm s(-1) (low -spin site) and the other with Delta E-Q = 0.792 mm s(-1) (high-spin site). As the temperature of the sample is increased to 300 K, the signal intensi ty of the high-spin site grows to 92% at the expense of the low-spin signal . The variable-temperature magnetic susceptibility data also support that t he tetraphenyl complex is a spin-crossover complex.