Absorption-emission energies and electronic structure calculation of dyes in solvent with different polarity using quantum chemical and molecular dynamic methods (static QM/PCM, QM/MM and dynamic c QM/MM md

The absorption-emission solvatochromic and Stoke's shifts have been used investigate for methyl substituent of indole (I) embedded acetonitrile (ACN), dichloromethane (DCM) and cyclohexane (CHX) solvents by using the CAM-B3LYP Linear Response (L.R.) and State Specific (S.S.) model. The absorption and emission spectra recorded above-cited solvent and bathochromic (red) shifts are observed for emission spectra in accordance with calculated PCM/S.S(non-eq) model in polar solvent medium. Experimental solvatochromic shifts have been compared by S.S. and L.R. models for emission and absorption energies compared to weakest polarity solvent CHX. As the polarity of the solvent increases, the State-Specific model has given better results for fluorescence emission shifts when compared by L.R. theory. However, the associated experimental shifts in absorption were between 0.17 nm and 5 nm relative to CHX. When the computed absorption shift under 2 nm, the L.R. theory get better results with experimental while the S.S. accurate shifts have been computed as this value rises towards 5nm. The TD-DFT/CAM-B3LYP-PCM/LR and SS model are in very good agreement with experimental shifts. The results show that LR and SS calculations have been consistent as the location of methyl in the molecule has changed and provided more reliable estimate of solvent shifts. Due to the experimental absorption band shapes were found to be in disagreement concerning theoretical, it encouraged us to model overlapping vibronic band shapes based on non-polar and polar solvent effects. This Franck-Condon analysis allowed to rationalize absorption shapes visually similar to UV. XVI Computational dynamic emission spectroscopy in rigid medium solvents is a very hard technique. But in recent years, technological improvement makes realistic models capable of experimental observables is possible. In this study, we have improved a successful simulation strategy in excitation and emission energies using hybrid models. The selected high layer target molecules and low and mobile layer water molecules are optimized with together. The hybrid QM/MM level is a powerful tool to efficiently is described the interactions of a molecule with its solvent medium. In this context, we simulate static and dynamic excited and emission spectra using COBRAMM interface protocol at the B3LYP/AMBER using Gaussian 16 AVX2 for rigid solvent models, TIP3P models are used within the mobile MM layer up to 50 nanometers radius away, for methyl derivatives of indole to a room-temperature. The QM/MM optimization calculations give us reliable structures both ground and excited states. Energy fluctuation of systems involves four states starting on the S0-S3, computations have been carried out by the same level for 150-200 femtoseconds. These calculated processes in ultrafast time scale have been explained how the evolution of excited and emission spectra when solvent molecules are movable. S0 and S1 geometry optimization of molecule in water droplet consisting of 500 TIP3P water are computed B3LYP/6-311++G(d,p) basis set and all low and mobile layer data was obtained Amber GAFF force field. S1 state geometry is converged approximately within 120 optimization cycles while the S0 optimization cycle taken a long time because of some water libration movement. Due to this libration motion caused chaos at the RMS/D value, the number of mobile molecules has been reduced from the optimization steps. The energy saved in each trajectory result has been converted to UV and emission spectra using statistical Kernel distributions.