A new ferrimagnetically ordered charge-transfer complex based on high-spin iron(III) chelate tetracyanoethenide with a Tc of 10K

Abstract The reaction of the high-spin iron(II) quadridentate chelate complex [Fe(L)], (L=diethyl( E , E )-2,2′-[1,2-phenylenebis-(iminomethylidyne)]-bis-[3-oxobutanoate]), with the electron acceptor tetracyanoethylene (TCNE) leads to the formation of the 1:1 charge-transfer (CT) complex [Fe(L)] + [TCNE] − . The magnetic characterisation of the CT salt indicates a chain structure with alternating S= 5 2 high-spin iron(III) and S= 1 2 TCNE − radicals in which the spin centres are antiferromagnetic correlated. The antiferromagnetic intrachain interaction parameter is very weak ( J intra ≈−8 cm −1 ) based on the spin Hamiltonian H=−J intra S i S j . At T =2 K and H =5.5 kG the magnetisation for the CT complex is about 83% of the saturation magnetisation value expected for a S total =( 5 2 − 1 2 )=2 system. A magnetic hysteresis loop was observed at T =2 K with a coercive field of 200 G. Below 10 K, the complex shows a weak spontaneous magnetisation characteristic for a canted ferrimagnet.