DFT Studies For The Effect Of Ligand’s Type And Redox Reaction On Second-order Nonlinear Optical Properties Of Ruthenium And Iridium Complexes

Nonlinear optical（NLO）materials have been attracted many researchers in view of their large panel of applications,for example,as molecular building blocks for optical communications,and electrooptical devices.The organometallic complex represent an emerging and growing class of NLO materials.Compared with organic and inorganic molecules,they have a richer structure and higher environmental stability,and their second-order NLO response exhibits switchable,adjustable,and multidimensional performance.In this paper,we calculate a series of Ru（II）and Ir（III）complexes.And we have introduced the study of geometry and electronic structure,UV-visible absorption spectrum as well as second-order NLO respons.The ratio of the second-order NLO properties can be used redox reaction based on the NLO switching material.Our outcome as:1.The NLO respons of cationic Ru complexes have been studied by density functional theory（DFT）.The research results:（1）The introduction of quinone-based ligands are able to enhance the first hyperpolarizability(β_tot)values of the eigen-state complexes,but there is no significant change in β_totvalues when the position of the quinone group on the nitrogen phenyl group is changed.（2）The β_totvalues of the Ru^Ⅱ/Ⅲ-quinone complexes decreases after being oxidized,but the β_totvalues of the bipyridine Ru^Ⅱ complexes without the quinone group increases significantly.Consistent with the results from the Hyper-Rayleigh Scattering（HRS）method.（3）The electron density difference maps（EDDM）studies show that the eigenstate is contributed by the metal-ligand charge transfer（MLCT）,but the complex after oxidation is the ligand-metal charge transfer（LMCT）contribution,resulting in changes to（D）/ acceptor（A）.2.The DFT method was used to calculate the substituent effect and polymorphic switchable response of a series of new Ir（III）complexes.The results show that the introduction of a strong electron withdrawing group NO₂ to the secondary ligand can significantly increase the β_totvalues;in addition,the β_totvalues from the neutral to the corresponding redox complexes also increases significantly.It is worth noting that the primary ligand is pyridine and the secondary ligand is CF₃ of complex 1,the β_totvalues of the oxidation state complex is 5.4 times that of the neutral complex,and the reduced state is 12.7 times that of the neutral complex.The large β_totvalues of the complex is mainly due to the lower transition energy and the red shift of the maximum absorption wavelength.The β density distribution further illustrates this conclusion.We believe that these ring metal Ir（III）complexes can be considered as a new multifunctional second-order NLO switching material.