Theoretical Study On The Factors Which Effect On The Optical Properties Of 3(5)-(9-anthryl) Pyrazole

Theoretical investigation on the optical properties of organic molecules is very helpful for reasonable design and synthesis of organic optical materials. Apprehending the packing peculiarity of organic luminescence substance and factors which effect on their optical properties on a molecular lever afford us with the basis and orientation of finds of new luminescence materials.In this paper, the ground state S0 structures of 3(5)-(9-anthryl) pyrazole and their derivatives are obtained using the density functional theory B3LYP/6-31G(d) method. The first singlet excited state S1 structures are optimized using the configuration interaction CIS/6-31G(d) method. The absorption and emission spectra are then evaluated using the time-dependent density functional theory TD-B3LYP with 6-311++G(d,p) basis sets. Our calculation results reveal that, for all the derivatives, whatever the substituent is an electron-withdrawing group or an electron-donating group, the calculated absorption and fluorescence emission wavelength values all show a red shift as compared with the parent molecule 3(5)-(9-anthryl) pyrazole. We also find that, compared with the parent molecule, the derivatives with R= -BH₂, -CCl₃, -CHO and -NH₂ are good candidates for materials possessing longer absorption and fluorescence wavelength; The solvent effect is discussed with the PCM model, the absorption and emission wavelength values of the 3(5)-(9-anthryl) pyrazole and the derivatives all become longer in the CHCl3 solvent and the oscillator strengths become stronger, comparing with in the air phase; The absorption and fluorescence emission wavelength values of the dimmers, trimers and tetramer into which are assembled by 3(5)-(9-anthryl) pyrazole molecule only in the form of N-H…N hydrogen bonding have no difference from the parent molecule; The wavelength values of the trimers show red shifts if there are both N-H…N hydrogen bonding andπ…πstacking interactions among the 3(5)-(9-anthryl) pyrazole molecule of the trimers, furthermore, wavelength of the trimers become longer along with shortening of distances between the two parallel anthracene rings.