STEPWISE MAGNETIC BEHAVIOR OF THE LIQUID CRYSTAL IRON(III) COMPLEX

EPR and Mossbauer spectroscopy is used to study a new liquid crystal complex of iron(III) with a Schiff base: 4,4'-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 chi T, where chi is the magnetic susceptibility) with an inflection point at similar to 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 J(1) = 162.1 cm(-1). Below 80 K iron(III) complexes are organized in 1D chains where the exchange value J(2) = 2.1 cm(-1). 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.