Unusual ferromagnetic coupling interaction in carboxylato-bridged Mn(II) complexes: Ab initio MRCI(SD) and DFT theoretical studies

For the title complexes the ab initio calculations of the ground and low-lying exited states have been carried out at level of MRCI(SD)+Q method. Through mapping to the spin model space the magnetic coupling constant (2.33 cm−1) between the Mn(II) ions was obtained, comparing with experimental value of 0.49 cm−1, and it is found that the Lande rule of the magnetic behavior is valid for the magnetic system. The DFT-BS calculations were used to examine the magneto-structural correlation. It is shown that as increase of the bridge-bonding angle the transition from ferromagnetic to antiferromagnetic coupling may occur, consistent with experimentally observations.