Theoretical Design Of One Kind Of Eximious Pt(Ⅱ) Complex Photoelectric Material Based On The Ligand Modification

Luminescence materials play an irreplaceable role in the fields of energy, lightingdisplay, electronic information and biological medicine, etc. With the updating anddevelopment of the science and technology, people’s production and life wereconstantly changed by luminescence materials. Transition metal complexes showedhigher chemical stability and luminous efficiency as the phosphorescent material ofthe organic light-emitting diodes (OLED). Therefore, theoretical studies on the impactto the luminescence properties of changing the ligand, makes an important guidingsignificance to the design and exploration of new type of transition metalluminescence materials.This report mainly involves the theoretical study on the photophysical properties oftwo types of the same category of phosphorescent Pt (II) complexes. One type of theN-heterocyclic Pt(II) complexes based on the auxiliary ligand withacetylacetonate(acac), the host ligand with dibenzothiophene(Sph2) connected with2-methyl-imidazoyl,3,5-dimethyl-pyrazoyl, pyridyl, methyl-triazole, named1,2,3,4,respectively. Another type of the N-heterocyclic Pt(II) complexes based on theauxiliary ligand with (acac), the host ligand with triarylboron(Bph3) connected withpyridyl(N), methyl-imidazole(C*), and methy-limidazole with added a π electronicphenyl, phenanthryl group, named5,6,7,8, respectively. The geometries, electronicstructures, emission properties, and radiative decay rate constant of the two types ofcomplexes were investigated theoretically by us.As to the calculation method, we selected five familiar functionals to choose thebest functional. The optimized geometries parameter and UV-vis absorption of1,5 and6, compared with the X-ray crystal diffraction data and absorption data, andfound that B3P86was the most suitable function. Therefore, the ground stategeometries were optimized at the B3P86method of theory, LanL2DZ and6-31G*basis set were used for the metal and non-metal atoms, respectively. Moreover,frequency calculations were performed at the same time. While the calculations oflowest-lying absorptions and the optimization of excited state geometries were at theTD-B3P86method of theory. The emissions were evaluated at the TD-M062x methodof theory. To simulate the experimental environment, absorption and phosphorescentemission calculations of5-8were within dichloromethane solvent provided by PCM.All the non-hydrogen atoms of1,3,4complexes were in the same plane, while thecoplanarity was destroyed by complex2with3,5-dimethyl-pyrazoyl perssad.Complexes5-7showed that coordination atoms and metal centre were in the sameplane, while the coplanar property is destroyed by the π-skeleton conjugated electrongroup phenanthryl of8. Based the optimized geometry at the S0state, we got theenergy gap between the frontier molecular orbital HOMO and LUMO, the energydifferences between the two highest lying occupied d-orbital (Δddocc) at S0state andthe Δdd*at the excited state. Both results suggested that2and8would show muchbetter electronic structure and orbital properties at their respective types of complexes.Through the calculation of phosphorescence of complexes, the emission wavelengthsof the two types of complexes were all blue luminescence materials. The lowest-lyingabsorption and phosphorescence properties of four complexes are all respectivelyoriginating from MLCT/ILCT and3MLCT/3ILCT transition. Finally, we used theexperienced equation to calculate the radiative decay rate constants kr, and krofcomplex8with a bigger π electronic conjugate group phenanthryl showed the largest.Thus, we sincerely hope these studies can provide theoretical guidance and support indesigning high efficiency blue phosphorescent materials.