Density Functional Theory Study On The First Hyperpolarizabilities Of Mono-and Bimetal Ir(Ⅰ)/Rh(Ⅰ)/Ru(Ⅱ) Complexes

Nonlinear optical（NLO）materials with good performance are widely used in laser technology,information storage,optical communications and other fields.Therefore,exploring NLO materials with excellent properties has become a hot spot for many scientists.Compared with pure organic NLO materials,organometallic complexes can effectively regulate the second-order NLO response by changing the type,number,oxidation state of the central metal and the change of the ligand.The phenanthroline,bipyridine,pyrrole and other nitrogen heterocyclic complexes have a larger second-order NLO response,due to its strongπelectronic delocalization.The second-order NLO response of the molecule can also be effectively regulated by photocyclization,redox.In this paper,the second-order NLO properties of mono-and bimetal Ir（I）/Rh（I）complexes and ruthenium ethynyl complexes were studied by quantum chemistry method.The main results are as follows:（1）The geometry structure,the second-order NLO properties and the electronic spectra of2,2?-bidipyrrins（L）and mono-and bimetal Ir（I）/Rh（I）-L complexes were investigated by density functional theory（DFT）method.The 2,2?-bidipyrrins（L）has a planar configuration,when coordinating with metal,the planar configuration is broken.Compared with the corresponding metal complex,L has obvious unidirectional charge transfer characteristics and hence shows a large first hyperpolarizability value,which is 2.2 to 5.5 times larger than that of others.The first hyperpolarizability of the bimetal Ir/Rh（I）-L complexes were smaller than the corresponding monometallic Ir/Rh（I）-L.This can be attributed to the complex has a multi-directional charge transfer when the complex is formed,and as the number of metals increases,the charge transfer in the opposite direction cancels each other more obviously.The?_vec values for both the mono-and bimetal Rh（I）-L complexes are all larger than the corresponding Ir（I）-L.（2）The second-order NLO properties for a series of half-sandwich ruthenium-based Cp*（dpe）Ru（[Ru*]）（Cp*=pentamethylcyclopentadienyl;（dpe）=bis（diphosphine）ethane）metal complexes were investigated by DFT.The calculated results showed that:the system 1,which the[Ru*]acetylide functionality para on the phenylene ring to the dihydroazulene/vinylheptafulvene（DHA/VHF）,have a largeβ_vec value compared with system2（[Ru*]acetylide meta on the phenylene ring to the DHA/VHF）.It was attributed to the fact that system 1 has the more obvious charge transfer（CT）and the lower transition energy compared with system 2.The system 3 with additional p-phenyl groups had the largestβ_vecec value in the studied complexes due to it has the most significant D-π-A intramolecular CT.In addition,theβ_vec values of the open-ring complexes were all larger than that of the corresponding closed-ring complexes.In summary,the work provides a theoretical reference for finding the second-order NLO material with excellent performance.