Study Of Solvent-dependent Ground State Geometry And Excited State Proton Transfer Dynamics Of 1,2,4-triazole Derivatives

In this paper,the geometries of the clusters of 3-Amino-1,2,4-Triazole?3AT?,3-Mercapto-1,2,4-Triazole?3MT?and 3-Mercapto-4-Methyl-1,2,4-Triazole?MMT?with defined number of solvent molecules have been characterized by resonance Raman spectra Combining with density functional theoretical?DFT?calculations.Their excited state decay dynamics process have been further investigated in the Frank-Condon region in different enviroments.The new ideas are included that not only the solute-solvent interaction control the ground state conformations,but also the nonadiabatic excited state decay dynamics process and the photo-induced hydrogen-atom detachment-attachment mechanism are greatly changed due to the interaction between solute and solvent molecular.The result indicated that the intra-/intermolecular hydrogen interaction played an important role in the excited state decay process.The main conclusions are summarized as follow:?1?Stable solid 3AT dimer conformations are assigned by FT-Raman,488 nm Raman and FT-IR spectra spectra combining with the DFT calculation 488 nm Raman spectra in solvents indicate that the stable conformation is 2H-3AT-solvent cluster in solvents.DFT calculation showed 3AT?solvent?n?n=2⁶?clusters can be greatly stabilized via NH?N H-bonding in CH₃CN,or via cyclic NH?O and N?OH bonding in CH₃OH and H₂O,in agreement with the experimental shifts.The maximum ultraviolet absorption band in polar solvent is mainly assigned to?_H??_L^*transition.The resonance Raman spectra are assigned in water,methanol and acetonitrile upon five different excited wavelengths.The results indicates that the-N-CH?NH₂?-N-group vibration should mainly contributed on excited state structural dynamics in the Frank-Condon region.?2?The 3MT is comfirmed as thione isomer of in crystal state and in solvents by FT-Raman,FT-IR and 488nm-Raman spectra.The A-band in the UV spectra is mainly assigned to???*transition in acetonitrile,methanol and water combining with the TD-DFT calculations.The most maximum absorptions are blue shifted with the polarity of solvent increasing from acetonitrile to water via methanol.The 223.1,228.7,239.5,245.9,252.7,266.0 and 273.9 nm resonance Raman in acetonitrile,methanol and water showed the obvious band shifts and intensity change on different excited wavelengths,especially for?₉?S₇=C₃ stretching+C₃N₂N₁/H₈N₄C₅/H₉C₅N₁ planar twisting?and?₁₅?C₃N₂N₁C₅/S₇N₂N₄C₃ twisting?.The vibrational modes of?₉ mode observsly discermed in methanol and water.However,it disappears upon 273nm in acetonitrile and become very strong upon 223 and 228 nm,The vibrational modes of?₁₅?C₃N₂N₁C₅/S₇N₂N₄C₃ torison?vibration is strong upon 223 and 228 nm wavelength in solvents,while it is very weak in FT-Raman spectra.This concluded that chemical reaction may produce on the higher excited states.So the short-term excited state dynamics mainly is contributed by-NH-C=S-NH-bending and torsion in the Frank-Condon region,may be this is the pathway of proton transfer.DFT and TD-DFT calculation predicted two nonadiabatic decay channels:?1?S_3,FC?S₃/S₂?S₂/S₁?S_1,min?S₁/T₂?T_2min?T_1min?S₀/T₁?S_0,min,or?2?S_2,FC?S₂/S₁?S_1,min?n?*??S₁/T₂?T₂/T₁?T_1,min?T₁-TS?T^'_1,min.?3?The ultraviolet absorption spectra of MMT are mainly assigned to???*transition in acentrile,methanol and water solvent.The most maximum absorptions are blue shifted with the increasing solvent polarity.The 223.1,228.7,239.5,245.9,252.7,266.0 and 273.9 nm resonance Raman in acetonitrile,methanol and water showed the obvious solvent dependant on?₁₅?N₁C₅stretch+H₆N₂N₁/H₉C₅N₁ in plane bending?vibration is strong in ground state spectra,the resonance Raman becoming weaker in acetonitrile solvent,while in water and methanol solvent was disappeared.What's more,?₁₁?N₁C₅/N₄C₅/N₄C₈ stretch?and?₁₂?N₄C₅ stretch+N₄C₅N₁/H₆N₂N₁/N₂N₁C₅ in plane bending?relative vibration intensity was changed in acetonitrile,methanol and water.This concluded that solvents lay large impact on geometries of excited states in the Frank-Condon region.Based on the experimental result,GRRM combining DFT and TD-DFT calculation predicted two nonadiabatic decay channels:?1?S_2,FC?S₂/S₁?S_1,min?S₁/T₁?T_1min?S₀/T₁?S_0,min,or?2?S_2,FC?S₂/S₁?S_1,min???*??S₁/T₂?T₂/T₁?T_1,min?T₁-TS?T^'_1,min.