Keggin-type phenylimido-polyoxometalates α-[PM12O39NPh]3- (M = W and Mo) have been systematically investigated on the electronic structures, redox as well as nonlinear optical (NLO) properties by density functional theory (DFT). The strong M≡N bond confirmed by natural bond orbital (NBO) analysis comprises one σ bond and two π bonds, the same as Mo≡N in [Mo6O18NPh]2-. Furthermore, phenylimido segment effectively modifies the electronic properties of α-[PM12O39NPh]3-. On one hand, when enlarging the inorganic cluster from {Mo6O18} to {PMo12O39}, the energy gap between HOMO and LUMO in α-[PMo12O39NPh]3- decreased, resulting in enormously anodic shift for the reduction potential, while the excitation energy is less and the total second-order polarizability β0 is up to 438.3×10?30 esu, which is nearly 10 times larger than that of [Mo6O18NPh]2-. On the other hand, when metal W in α-[PM12O39NPh]3- is substituted by Mo, the interaction between Mo and N is enhanced and the redox ability becomes stronger. The β0 value for α-[PMo12O39NPh]3- is more than 5 times higher than that of α-[PW12O39NPh]3?. It indicates that changing appropriate metal or enlarging the inorganic cluster will improve the redox properties and second-order nonlinear response. Moreover, the electron transition for three compounds mentioned above occurred mainly from organoimido segment (as the electron donor) to polyanion cluster (as the acceptor). As a result, α-[PMo12O39NPh]3- may be a promising candidate for oxidant and nonlinear optical material.
SONG PingYAN LiKaiGUAN WeiFENG JingDongLIU ChunGuangSU ZhongMin
