The Influence Of Excited State Dynamics Of Hydrogen Bond For Photophysics Properties Of Several Molecular Systems

In this paper,the special photophysics properties,excitation and deactivation mechanisms,related reaction processes and their application adsorption of materials are studied by analyzing the dynamics of ground state and excited state of several complex molecular systems.In the process of research,the time-dependent density functional theory,molecular dynamics and wave function analysis method are used.The changes of spectral,reaction and material properties caused by photoexcitation and the influencing factors were analyzed comprehensively,comprehensively and dynamically.First,we studied the effects of solvent polarity and hydrogen bond on coumarin 500.coumarin 500,as one of the classical 7-aminocoumarins,is extensively used in the study of solvatochromic properties because of its high fluorescence quantum yield and large solvatochromism.According to the different spectral properties of the coumarin 500 in different polar solvents,the time-dependent density functional theory method and the wave function analysis are used to obtain a detailed explanation of the mechanism of intermolecular hydrogen bonding changes spectral properties of coumarin 500 in different polar solvents.The optimization configuration in the ground state and the calculated absorption spectra indicate that the strength of intermolecular hydrogen bonds was enhanced with the enhancement of the solvent polarity and the type B hydrogen bond played a leading role.In the first excited state,the hydrogen bonds between coumarin 500 and polar solvent increased obviously and the fluorescence intensity decreased obviously.Interestingly,both the absorption maximum and the hydrogen bond strength of coumarin 500 hydrogen bonded complex are confirmed to have a linear relationship with the solvent polarity function?f.This work provides a reasonable explanation for the change of spectral properties of coumarin dyes in polar solvents.Secondly,the mechanism of mesoporous pulp waste?MPW?and polyaniline?PANI?adsorptive removal methyl orange?MO?dye from their aqueous solutions are investigated.Methyl orange is regarded as our research object because of its wide application in industry and the harm to the environment.The configuration optimization and wave function analysis indicate that hydrogen bond and Van Der Waals interactions play a significant role in MO adsorption by MPW and PANI.For MO adsorption by MPW,hydrogen bond and Van Der Waals interactions are both weakened in the S₁ state.In contrast,hydrogen bond and Van Der Waals interactions between PANI and MO are both enhanced in the S₁ state.The thermodynamic parameters reveal that the MO adsorption by MPW and PANI are spontaneous.The adsorption of MO on MPW is reversible and the adsorption energy is higher than that of activated carbon,which makes the MPW a more economical,efficient and reusable adsorbent.This work presents a reasonable mechanism of PANI and MPW adsorption decontamination,which provides guidance for the design of new adsorbent and better application of existing adsorbent.Finally,the effects of environmental factors on the photophysical behavior of NIAD-4 are investigated.As a promising fluorescent marker,NIAD-4 can rapidly and effectively detect the amyloid fibrils,which is of great significance for the prevention and treatment of a variety of diseases caused by amyloid fibers.The electrostatic potential and absorption spectrum analysis indicate that NIAD-4 is in the NIAD-4-3H₂O compound form in the ground state in water.In the excited state,the intermolecular hydrogen bonding are significantly enhanced and the torsion process of NIAD-4 does not occur.The three dihedral angles oscillate approximately 2.5,3 and 3.5 degrees and vary by 1.0 degree,showing that NIAD-4 is likely to be a plane structure in the S₁ state.In addition,intermolecular hydrogen bonds have a significant influence on the fluorescence behaviour of NIAD-4.When the hydrogen bonds are stronger,there are larger redshifts of the maximum fluorescence wavelengths.The fluorescence intensity also increases in more polar solvents.Therefore,the influence of intermolecular hydrogen bonds should be carefully taken into consideration when NIAD-4 is used to probe amyloid fibrils in hydrogen-bonding surroundings,especially in complex bioenvironments.