Magnetic effective density functional studies on electronic states of Cr2(pyphos)4 and Pt2Cr2(pyphos)4(CH3)4

The effective exchange integral (Jab) values between chromium ions in the aligned metal complexes; Cr2(pyphos)4 and Pt2Cr2(pyphos)4(CH3)4 were investigated theoretically. Full model calculations presuming chromium(II) that were usually found in the Cr2(O2CR)4L2 complexes could not reproduce the small experimental Jab values, suggesting another oxidation state of Cr. Several electronic states presuming Cr(III) were examined to explain the experimental Jab values using naked model. The Cr(III) dimer model which had π4δ2 triple bond showed small Jab value that could explain experimental Jab value of Cr2(pyphos)4. The calculated Jab value presuming π4δ2 triple bond of Cr(III) core also indicated appropriate Jab values which could explain the very small experimental Jab of Pt2Cr2(pyphos)4(CH3)4. Natural orbital and instability analysis were performed to investigate such small Jab value in Pt2Cr2(pyphos)4(CH3)4. The conjugation of Pt&z.sbnd;Cr&z.sbnd;Cr&z.sbnd;Pt core seemed to be effective in the decrease of Jab between the Cr ions. [Copyright &y& Elsevier]