Optically induced spin transition effect on structure of Fe(II) polymeric complexes by XAFS spectroscopy

Changes in the electronic and spatial structure of polymeric Fe(II) complex es with 1,2,4-triazoles and various anions upon spin transition was studied using XAFS spectroscopy. The compounds exhibit an abrupt thermally driven spin transition (S = 0-2) at temperatures varying from 175 to 400 K dependi ng on the composition. Spin transition and structural changes were induced by variations of the anion, dilution with Zn, under the heating or the acti on of light. XAFS measurements were performed at the Budker Institute of Nu clear Physics in Novosibirsk. In all complexes, the spin transition is acco mpanied by drastic changes in the local environment of Fe atoms. High spin metastable long life states was detected and studied in the polymeric compl ex Fe(atrz)(3)(ClO4)(2). It was established that the changes in structure o f polymeric complexes upon the transition to a metastable high spin state u nder the action of light differ from those in the thermally induced spin tr ansition. Such difference is determined by mutual influence of Fe atoms in high spin and low spin states in polymeric chains. (C) 2001 Elsevier Scienc e B.V. All rights reserved.