Ultrafast Luminescence Decay and Intersystem Crossings in rhenium (I) complexes: DFT Method

The interpretation of ultrafast intersystem crossing (ISC) processes in transition of metalcomplexes through the destruction of femtosecond luminescence, which is a challenging issue inquantum chemistry, is presented. To understand this photophysical phenomenon, explicitconsideration of the spin orbitcoupling (SOC) is necessary. So far little studies have been done,and especially on heavy metal compounds with heavy elements such as Rhenium [1].Fac-[Re(Br(CO)3(N^N)] complexes, a new series of chromophoric ligands based upon thefused imidazo[4,5-f]-1,10-phenanthroline core that are functionalised with different substitutedaryl groups [2] were used. These type complexes are often ascribed to metal-to-ligand chargetransfer (MLCT) excited states. Such complexes have found application in the design ofchemosensors and cell imaging agents [3].The optimization of S1, S2, S3, T1, T2, T3, T4 excited states, as well as the absorptionwavelength and oscillator strength was done using the TD-DFT method, with the triple-ξ base setin the Gaussian 09 Linux. The results show that the agreement with experiment is quite good.Finally, the luminescence spectrum was plotted and the results were analyzed. The wavelengthof maximum excited state energy at 584.03 nm and oscillator strength £=0.0005 is attributed tothe S1 state in complex and in the experimental data excited state energy shown at 580 nm.

Keywords:

TD-DFT Method , Singlet and Triplet Excited States , Intersystem Crossing , Rhenium Complexes