| Physics is a discipline that explores the nature of the universe,including the properties,characteristics,movement phenomena and laws of material.The appearance of atomic and molecular physics has opened the door for the study of the internal structure and properties of atoms and molecules and has become a link between the macro and micro world.This is just as Chinese people’s understanding of history,like:long period of division,together for a long time to divide.The development of atomic and molecular physics affects all fields of physics and intersects with other disciplines,such as chemistry,biology,astronomy and materials science.Molecular spectroscopy is a window to gain insights into the structure and movement of molecules.With the continuous improvement of molecular spectroscopy theory and the rapid advancement of experimental techniques,the research of molecular spectroscopy has progressed toward higher precision.With the continuous deepening of the spectral research,the wave of excited state properties and dynamic behavior has been set off.The main work of this article is as follows:First of all,considering the problems of transient molecular lifetime,energy level degeneracy and instrument resolution,there are certain difficulties in the experimental measurement of molecular high-resolution vibrational spectra,which requires the theoretical study of the vibrational spectrum.By density functional theory（DFT）and second-order M?ller-Plesset（MP2）methods combined with second-order vibration perturbation theory（VPT2）,we have theoretically investigated the equilibrium geometries,spectroscopic constants and anharmonic force fields of transition metal-sulfur compounds（MSH,M=Ag,Cu）and yttrium dicarbide（YC2）in the electronic ground state.By bringing the spectral data obtained into the corresponding energy level formula,the rotational energy level of the molecule can be calculated which can guide the experimental work.Then,the influence of hydrogen bond excited state dynamics on photochemistry and photophysical processes is studied theoretically.1-（Acylamino）anthraquinones（AYAAQs）derivatives,with an infrequent intramolecular hydrogen bond N-H···O,are extensively concerned by researchers.The main purpose of this work is to study the behavior of the excited state hydrogen bond dynamic of these systems,through the DFT method and the time-dependent density functional theory（TD-DFT）method suitable for the calculation of excited states,providing the reasonable explanation for fluorescence quenching phenomenon.Six compound systems with different substituted grouparechosen,including1-（heptanoylamino）anthraquinone（HPAQ）,1-（acetylamino）anthraquinone（AAAQ）,1-（chloroacetylamino）anthraquinone（CAAQ）,1-（dichloroacetylamino）anthraquinone（DCAQ）,1-（trifluoroacetylamino）anthraquin-one（TFAQ）and their parent molecule 1-aminoanthraquinone（AAQ）.The results indicate that in addition to the excited state intramolecular proton transfer（ESIPT）reaction,there is also a barrierless acylamino twist intramolecular charge transfer（TICT）relaxation path and following the intersystem crossing（ISC）process,which can explain fluorescence quenching.Through the experiment that AAQ dye molecule has phosphorescence and the similar theoretical results,we predict that AYAAQs derivatives also have phosphorescence.Finally,the 2-methyl-3-hydroxy-4（1H）-quinolone（MQ）dye,which is a proton transfer probe,is selected as the research subject.The effect of benzo-annelation on intermolecular hydrogen bond and proton transfer of MQ is also investigated by DFT and TD-DFT methods.By analyzing the geometry,infrared vibrational spectra,elecctron spectra,frontier orbitals,noncovalent interactions and transition state of MQ and its benzo-analogue 2-methyl-3-hydroxy-4（1H）-benzo-quinolone（MBQ）in the ground and excited states,the effect of benzo-annelation on MQ makes red-shift in electron spectra,intermolecular hydrogen bond weakened,and the barrier of proton transfer heightened.We hope to provide help for the design of fluorescent probes. |
