Magnetic Properties of Iron(III) exhibiting Spin-Equilibrium Behavior and Imidazolate-bridged Binuclear Complexes.

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1. Synthesis and Magnetic Properties of Iron(III) Complexes Exhibiting a Spin-Equilibrium Behavior.(1). Five binuclear iron(III) complexes bridged by hyrazine, 1,1'-tetraethylenebis(imidazol), or bis-(pyridine) compounds have been prepared, and their spin-equilibrium behavior between high spin (s=5/2) and low-spin(s=1/2) states has been investigates by means of the temperature dependences of the magnetic susceptibilities and the electronic spectra. The pyridine complex is low-spin, while the bis(imidazole) and the bis(pyridine) complexes showed a spin-equilibrium between high-spin and low-spin states, accompanied by a striking thermochromism in both the solids and solutions.(2). An Iron(III) complex [bis[3-(3-methoxysalicylideneamine)propyl]amino-O,N,N',N",O'](pyridine)-iron(III) Tetraphenylborate with a spinequilibrium has been investigated by means of the temperature dependences of the magnetic susceptibilities, the electronic spectra, and cyclic voltammetry. The pure electronic spec … More tra for high-spin and low-spin species were evaluated from the observed electronic spectra and the equilibrium constants obtained from the magnetic data. The electrontransfer entropy of the Fe<@D13+@>D1 + e Fe<@D2+@>D1 process (deltaS<@D2et@>D2) was obtained as 205 JK<@D1-1@>D1mol<@D1-1@>D1 from the temperature dependence of the cyclic voltammogram.2. synthesis and magnetic properties of imidazolate-bridged binulear complexes.(1). Imidazolate-bridged Cu(II)-Mn(II)- Cu(II) complexes have been prepared and characterized. The magnetic susceptibility data were represented by a spin-only interaction model(1/2-5/2-1/2) with J_<Mn-Cu> value of -13 cm^<-1> for (tfa) complex and -8 cm^<-1> for (hfa) complex.(2). Two imidazolate-bridged binuclear copper(II) complexes[Cu(L)Cu(tfacac)_2]and [Cu(L)Cu(tebima)]-[PF_6][C10_4] ・Me_2CO have been prepared and characterized by elemental analyses, melting points, molar electrical conductivities, i.r., electronic, and e.s.r.spectra, magnetic susceptibilities. The magnetic susceptobolity data gave the antiferromagnetic interaction parameters 2J = 112 cm^<-1> for the former complex and ー140 cm^<-1> for the latter. The e.s.r.spectra of complexes measured in frozen solutions (77K) at X-band frequency showed broad deltaM=1 and weak deltaM=2 absorptions. Less