AB-INITIO MO CALCULATIONS OF SUPEREXCHANGE INTEGRALS FOR TRANSITION-METAL FLUORIDES - MFM(3- ACTIVE CONTROL OF THE MAGNETIC STATES() (M=CU(II), NI(II), AND MN(II)) )

Ab initio UMP calculations were carried out for binuclear transition-m etal fluorides in order to elucidate variations of the superexchange i ntegrals with intermetallic distances. It was shown that the antiferro magnetic superexchange integrals calculated for tricentric systems MFM (+3) (M=divalent ions) by the approximately spin-projected UMPn (n= 1 - 4) method with the triple zeta basis set are about -134, -22 and -1 cm(-1) in the cases of Cu(II), Ni(II) and Mn(II), respectively. These are consistent with the experimental results available. The hole-or el ectron doping into antiferromagnetic systems is also discussed in rela tion to previous proposals to obtain the switching type molecular magn ets controlled by thermal, photochemical, electrochemical and other te chniques.