Theoretical Investigation On Properties Of Several Fluorescent Probes For Cyanide

In the 21st century,quantum chemistry calculation has been widely applied in many fields,such as chemistry,biology and materials.Quantum chemistry methods are used to simulate and explore the structure and properties of molecule,which provide theoretical guidance for experiments.In this paper,density functional theory（DFT）method was applied to study the properties of several fluorescent compounds.Time-dependent density functional theory（TDDFT）method has been employed to investigate the dynamical behavior of hydrogen bonds in excited state from the intramolecular hydrogen bonding of terasubstituted imidazole core（TIC）.Dual-luminescence mechanism of TIC molecule was theoretically elucidated through calculating the frontier orbits,electronic configurations,infrared spectra and potential energy curves of the TIC molecule.In the excited（S₁/S₂）states,the intramolecular hydrogen bond of TIC molecule is shortened,which is beneficial to the intramolecular charge and proton transfer,promoting the TIC molecule’s a twisted intramolecular charge transfer（TICT）process in the S₁ state and the intramolecular proton transfer（ESIPT）process in the S₂ state.Thus,the dual-luminescence mechanism of TIC can be theoretical explained in the following way:（1）In the less hydration environment,intermolecular hydrogen bond can be formed between the solvent and TIC which accelerates the electronic transition to the S₁ state.So the strong single emission can be attributed to the E*form of TIC in the S₁ state due to the TICT process.（2）In the nopolar and/or semi polar solvents,the weak dual emission which are E*form and K*form of TIC are due to the enhancement of ESIPT reaction according to the strengthening of intramolecular hydrogen bond O–H···N in the S₂ state.The formation of the tautomer generates the other emission via the IC and ICT processes.The reactive activity of three 7-diethylaminoumarin fluorescent probes on specificβcarbon was studied,and the experimental phenomenon of rapid and high sensitivity detection of CN^-was explained by 3-（2-formylacrylonitrile）-7-diethylaminoumarin.By comparing the orbital energy difference of three coumarin probes,the electrostatic potential and the charge of H on the specificβcarbon,the activity of 3-（2-formylacrylonitrile）-7-diethylaminoumarin on the specificβcarbon was the greatest in three coumarin probes,and it was the most favorable for the reaction with the rich electron CN^-.Therefore,it can provide theoretical guidance for the design and synthesis of new cyanide fluorescent probes experimentally.The two configurations of 3-（2-formylacrylonitrile）-7-diethylaminoumarin were found to have similar values in terms of UV-Vis absorption,nuclear magnetic shift,orbital energy difference,atomic charge and so on.Which is suggested that there may be two configurations in the same system.Through the transition state search,IRC and single point energy calculations were performed,theoretically predicting the possibility of the existence of the two configurations of 3-（2-formylacrylonitrile）-7-diethylaminoumarin.And which prediction results requires further experimental demonstration...