Proton Transfer Recognition And Response Mechanism Of Several Fluorescent Sensors

Fluorescent sensors(fluorescent probe molecules)can realize efficient and unique identification of the analytes due to their selectively combination with the analytes,which induces significant changes in their physical and chemical properties.Fluorescent sensors have many inherent advantages,such as:high sensitivity,real-time detection and remote detection,so they play extremely important roles in physical chemistry,biology,environmental chemistry,hydrometallurgy,high purity metals,high purity materials,etc.Recognition and response mechanisms of fluorescent sensors are very important in the rational design and synthesis of high-efficiency fluorescent sensors.However,the response processes to cations and anions of fluorescent sensors are complex,the study on the structure and dynamic response processes of the fluorescent probe molecules has attracted wide attention.This doctoral thesis theoretically simulates the structures and properties of several fluorescent probe functional molecular systems in their ground state and excited state.Combining with the correlated experimental spectral results,the effect of hydrogen bond interaction on the proton transfer process of these fluorescent probe molecular systems is studied.Further,the structural and dynamic factors affecting their recognition responses to different kinds of cations and anions are investigated.Our research results not only increase the deeply understanding of the effect of hydrogen bond interaction on the physical and chemical properties of fluorescent sensor molecule system,but also provide crucial hints for rationally designing more efficient novel fluorescent sensor functional materials and devices.Firstly,a novel pyridine fluoride ion fluorescence probe(fluoride ions fluorescent sensor 2)containing-OH group is studied.The configurations of the stable complexes of fluoride ions fluorescent sensor 2 with F-/other anions,and its protonated products are optimized.The correlation between electrostatic potential in the ground state with hydrogen bonding interactions,and the binding energies between fluoride ions fluorescent sensor 2 with the anions are calculated.The O-H…F-/O-H…anions hydrogen bonding interactions,taking the-OH group as reaction site,are studied.Then its interaction structural factors for selectively recognition of F-are reasonably explored.Furthermore,by constructing the potential energy curves of the complex of fluoride ions fluorescent sensor 2 with F-/other anions,the direct evidence is provided for the F-induced protonated process.The micro-response mechanism of fluoride ions fluorescent sensor 2 is indicated from the dynamic point of view.The red shift of ultraviolet-visible absorption spectra observed in the experiment is well explained though analyzing the charge distribution change between in ground state and excited state,following the photo excitation.Secondly,the 2-(2'-hydroxyphenyl)benzoxazole(HBO)derivatives are theoretically studied.In detail,the electron acceptor(-COOH and-NO2)and electron donor(-OH and-NH2)substituted groups are introduced into the molecular system,further the conjugated skeleton structures of the molecules are increased.The geometries of HBO derivatives are optimized in their ground state and excited state.The absorption and IR spectra are calculated.Then the influences of substitute effect and conjugation effect on excited state hydrogen bonding interaction are analyzed.The structural factors for altering the chromophore's fluorescent properties,caused by the relationship between molecular structure with hydrogen bonding interaction,are investigated.Furthermore,the potential energy curves of the HBO derivatives in their ground state/excited state are constructed,and the charge distribution changes following the photo excitation are simulated.Then,the mechanisms of the excited state proton transfer process of HBO derivatives,controlled by the substitute effect and charge transfer distance in the molecule system,are explored from the point of view of proton transfer reaction path and reaction energy barrier.Finally,the intramolecular hydrogen bonding structures and their dynamics of two kinds of fluorescent probes are studied.The configurations of thiazole fluorescent probe molecule(Bis-HPBT)and phenolic hydroxyl Schiff base aluminum ion fluorescent probe molecule are optimized in their ground state and excited state.Their corresponding properties are simulated.The IR spectra are calculated.The experimental red shift phenomena of UV-Vis absorption and fluorescence emission spectra are well explained,though analyzing the charge distribution change following the photo excitation and the simulated electronic spectrum.Furthermore,by constructing the single proton transfer and double proton transfer potential energy curves of these two kinds of fluorescent probe molecules in their ground state and excited state,the competition mechanisms between stepwise single proton transfer with synergetic double proton transfer processes are investigated,from the point of view of proton transfer reaction energy barrier.The reasonable proton transfer reaction path and mechanism of intramolecular excited state single proton transfer dynamic processes are explored.The important role of excited state hydrogen bond interaction in the photophysical and photochemical processes of complex fluorescent probe molecular systems is interpreted.