STepwise Magnetic Behavior of the Liquid Crystal Iron(Iii) Complex

Abstract

EPR and Mossbauer spectroscopy is used to study a new liquid crystal complex of iron(III) with a Schiff base: 4,4'S-dodecyloxybenzoyloxybenzoyl-4- oxysalicylidene-2-aminopyridine with a PF6'{ counterion. It is shown that Fe(III) ions exist only in the high-spin (HS, S = 5/2) state. It is found that under the influence of temperature the system demonstrates the stepwise behavior of the product of the integrated intensity of EPR lines (I ) and temperature (proportional to "where" is the magnetic susceptibility) with an inflection point at "80 K. Above 80 K a new EPR spectrum is detected due to the excited S = 2 state and the formation of dimeric molecules (through oxygen bridges) with a strong intramolecular antiferromagnetic exchange interaction J1 = 162.1 cm-V1. Below 80 K iron(III) complexes are organized in 1D chains where the exchange value J2 = 2.1 cm-V1. At 80 K there is a structural phase transition in the system: the transition from a 1D chain organization of HS Fe(III) centers to dimeric molecules. Based on quantum chemical calculations a model of the binuclear iron(III) complex is proposed. Copyright © 2013 by N. E. Domracheva, V. E. Vorob'eva, A. V. Pyataev, R. A. Manapov, E. M. Zueva, M. S. Gruzdev, U. V. Chervonova.