Study On The Properties And Responsive Mechanisms For Two Kinds Of Novel Two-photon Fluorescent Molecular Probes

Nonlinear optics is developing very quickly since emergence of the laser was in the 1960 s. Novel organic nonlinear molecular materials have been in-depth studied, specially, organic two-photon absorption(TPA) molecular materials, with their own unique advantages in the field of life, information science, and many other areas, present a great prospect in application. Recently, two-photon fluorescence probes have attracted lots of attention because their advantages of high sensitivity, high selectivity, and long absorption wavelength. At present, lots of anionic, cationic, small molecule probes were designed and synthesized. The theoretical research on properties of two-photon fluorescence molecular probes, especially their response mechanism, is not enough in comparison with the extensive experimental research.In the thesis, due to the situation that research for gases especially for cell endogenous gases was rare, we select the two-photon fluorescence molecular probes for hydrogen sulfide(H2S) and oxide(NO). Meanwhile, we make a theoretical analysis for the intramolecular charge transfer(ICT) and photon-induced electron transfer(PET) mechanisms. The research contains two sections. The first part is for two kinds of the two-photon fluorescence molecular H2 S probes based on ICT mechanism, and their optical properties and response mechanism are analyzed. The second part is for two kinds of the two-photon fluorescence molecular NO probes, and both of them are with benzene hydrazine as NO receptors. The PET mechanism is analyzed at the molecular level. The main contents and results are as follows.1. Two-photon fluorescence probes of H2 S based on the mechanism of ICTResponse theory is used to investigate one-photon absorption(OPA) and TPA as well as emission properties of AcHS-1,2 with polarizable continuum model(PCM). Obvious changes on optical properties including greatly redshift of OPA and TPA as well as emission peak position are demonstrated when the probes react with H2 S. Compared with AcHS-1 with n-butyl group, AcHS-2 with hydroxyethyl group shows preferable nonlinear optical properties. Most importantly, on basis of Mulliken population analysis for the free molecules Ac HS-1,2 and their products with H2 S, responsive mechanism of AcHS-1,2 for H2 S is attributed to ICT.2. Newly synthesized PET-based two-photon fluorescent NO probesDensity functional theory in combination with PCM is used to investigate OPA,TPA as well as emission properties of newly synthesized PET-based two-photon fluorescent probes QNO and LNO in the absence and presence of NO. Both fluorescent intensity and TPA are enhanced when QNO(LNO) reacts with NO, which theoretically proves that the compounds QNO and LNO are promising two-photon fluorescent probes for NO. Moreover, QNO is demonstrated to be preferable because of its superior fluorophore. Analysis of molecular orbitals is presented to explore responsive mechanism of QNO(LNO) for NO.There are six chapters in this thesis. The first chapter gives a brief introduction to the nonlinear optical phenomenon and the development process of nonliear optics and two-photon molecular materials. The second chapter is about the fluorescent molecular probes including the structure and the response mechanism of ICT and PET. The theory of quantum chemistry of many electronic system, time-dependent perturbation theory and the methods to calculate the TPA cross sections are introduced in the third chapter. Chapter four studies the structure, optical properties and responsive mechanism of the two-photon fluorescence H2 S molecular probes with the fluorophore of Naphthalene imide. The fifth chapter discusses two cases of two-photon fluorescence NO probes and contains the effect of fluorophore on sensing NO. The summary and prospect are presented in the last chapter.