Restudies of the spin state in (isothiocyanato)(pyridine)(porphinato)iron(III) hemipyridine complex. A spin-crossover complex with two magnetically distinct sites

The results of low-temperature X-ray determination, Mössbauer and magnetic measurement of spin-crossover (isothiocyanato)(pyridine)(porphinato)iron(III) hemipyridine are reported. The features in the 77 K Mössbauer spectrum include two doublets, one with a quadrupole splitting (ΔEQ) of 1.96 mm s−1 (low-spin site) and the other with ΔEQ=0.792 mm s−1 (high-spin site). As the temperature of the sample is increased to 300 K, the signal intensity of the high-spin site grows to ∼92% at the expense of the low-spin signal. The variable-temperature magnetic susceptibility data also support the fact that the tetraphenyl complex is a spin-crossover complex.