TIME-DEPENDENCE OF THE MAGNETISM OF [FE(PAP)(2)]CLO4 AND ITS SOLVENT ADDUCTS - UNEXPECTED SOLID-STATE EFFECT IN HIGH-SPIN DOUBLE-LEFT-RIGHT-ARROW LOW-SPIN STATE TRANSITION

The complexes [Fe(pap)(2)]ClO4 (Hpap: bis[2-hydroxyphenyl-(2-pyridyl)- methaneimine) and the solvent adducts were synthesized, and their magn etic susceptibilities and Mossbauer spectra studied over the temperatu re range 80-300 K. The spin state transition of [Fe(pap)(2)] ClO4 meas ured immediately after preparation occurred gradually at about 250 K, the temperature moved lower at aging time, and finally shifted to 150 K one week after preparation. Furthermore the unique feature of this s ystem is the fact that part of the aged sample is 'frozen-in' S = 5/2 state by rapid quenching to 80 K. The spin-crossover transitions of [F e(pap)(2)]ClO4 . acetone and [Fe(pap)(2)]ClO4 . d(6)-acetone occur wit hin a narrow temperature range of 2 degrees near 209 K with a differen ce in the transition temperatures between both samples of about 1.1 de grees.