Chiang Mai Journal of Science

The ligand of 2-(pyridin-2-yl)benzoxazole (pbo) has been prepared, and the corresponding complexes of iron(II), the tetrafluoroborate, perchlorate, and tetraphenylborate, have been synthesized and characterized in details in magnetism, Mössbauer, and electronic spectral properties. It was found that the tetrafluoroborate and perchlorate were observed to be normal paramagnet, with the magnetic moment of 5.29 BM (θ = -6K) for the perchlorate and 5.06 BM (θ = -9K) for the tetrafluoroborate complexes at room temperature. For the tetraphenylborate complex, the magnetic moment was found to be 5.20-5.50 BM (at room temperature), which was slightly and gradually decreased to 4.25-4.57 BM at low temperature (90K), however. This is associated with the spin-state transition in iron(II) for this salts as indicated by its Mössbauer spectral properties. The electronic spectrum of the corresponding nickel complex showed that the ligand field strength lied in the range for which the iron(II) complex might undergo the spin-state transition.