EFFECTS OF STRUCTURAL MODIFICATION ON THE GROUND STATE OF METALLABENZENES: SINGLET VERSUS TRIPLET STATE

Extensive density functional calculations were used to explore the geometries and relative stabilities of metallabenzenes with various spin multiplicities. The structural modification effects on the energy splittings between the singlet and triplet states, including the replacement of metal, the change of ligand environment, and the substitution of hydrogen and carbon atoms in the aromatic ring, were investigated. Calculations show that the stability of the singlet and triplet metallabenzenes strongly depends on the metal center, and the first-row transition metal metallabenzenes most probably have the triplet ground state. The stability of the triplet state can be enhanced by the strong π- and weak-field ligands as well as the electron-withdrawing substituent for hydrogen at the aromatic carbon such as - PPh3+ . Present results can help us understand the magnetic properties of metallabenzenes and construct the function-orientated metallacyclic compounds.