Theoretical Study On The Chemical Bonding Properties Of Square-planar Aluminum Complexes And The Second-order Nonlinear Optical Properties Of DTE-containing Bimetallic Ruthenium Acetylide Complexes

Taking unique structures and bonding characteristics into consideration Al complexes are extensively used in the realm of materials science.Without the d orbitals involved,the interactions of Al complexes are not typical true two-electron three-center interactions.Thus,we have extensively investigated the interaction between Al and L(PhI2P2-).In additional,(DTE)–containing bimetallic ruthenium acetylide complexes have attracted much attention and have a promising application in the realm of materials.In order to enhance the nonlinear optical(NLO)properties of these complexes,the substituent effect and the reversible optical isomerization of the DTE group was carried out.Thus,our theoretical work would provide a new perspective for the further experimental studies on NLO switching compounds with a promising future.In this work,the interaction between Al and L(PhI2P2-)and optical properties of Square-planar Al complexes as well as the second-order nonlinear optical properties of DTE bimetallic ruthenium ethynyl complexes were investigated by quantum chemistry method.The results are as follows:(1)Complex 1 [(PhI2P2-)Al Cl] was widely applied in advanced materials due to its interesting structure.Two Square-planar(SP)complexes 2 [(PhI2P2-)GaCl] and 3 [(PhI2P2-)NiCl] together with SP complex 1 have been investigated by density functional theory.The results indicate that the interaction between M(M = Al,Ga,Ni)and L(PhI2P2-)are not typical true two-electron three-center interactions but a mixture of electronic and covalent.The presence of covalent bond character between M and L is supported by the localized orbital locator,electron localization function and energy decomposition analysis.Further,we also predicted the absorption spectrum of complexes 1-3 by time-dependant density functional theory.The results of absorption spectrum show a red-shift trend from complexes 1,2 to 3.Investigation of the bond interaction at the molecular level can benefit the design and preparation of such SP complexes in chemistry and materials science.(2)The optical properties of photochromic diarylethene(DTE)–containing bimetallic ruthenium acetylide complexes were studied at the density functional theory level.With the intension to tune the first hyperpolarities for these complexes,the substitution effect and reversible photocyclization processes were carried out.Calculated results show that the first hyperpolarizability value increase gradually with the extended ?–conjugation ligand and the stronger electron-donating group.And the DTE unit plays a unique and dominant role in photo-switchable processes due to its significant geometrical changes by light stimulation.The photocyclization switch ability suggests that these complexes can be viewed as nonlinear optical(NLO)properties switching.Thus,our present work would be beneficial for further theoretical and experimental studies on NLO switching compounds with a promising future.