The Design And Synthesis Of Fluorescent-EPR Bifunctional Probe And Application In The Mechanism Of Alcohol Oxidation

Spectroscopy is an important method to study the molecular structure and explore the reaction mechanism.It has always been a hot spot for scientists to find effective spectral techniques to study the reaction mechanism,to visualize the reaction process and to prove the key steps or important intermediates in the reaction process.Based on the spectral properties of the luminescent properties of the terpyridine platinum(II)complex chromophore with the 2,2,6,6-tetramethyl piperidine oxide(TEMPO)free radical properties,we designed bi-functional probes of the two types of terpyridine platinum(II)complexes with TEMPO group,and made a complete synthesis and detail characterization.Then,the interesting spectral properties were also investigated.Moreover,the quenching mechanism of TEMPO in terpyridine platinum(II)complex system was explained by experiments and theoretical calculations.Meanwhile,we applied the complex in studying the catalytic oxidation mechanism of benzyl alcohol in combination of operando electron paramagnetic resonance(EPR)and fluorescence spectroscopy.This thesis consists five chapters.1.It has been outlined the basic principles and applications of fluorescence spectroscopy and EPR spectroscopy,as well as the progress of spectral combination.Moreover,the spectroscopic properties of terpyridine platinum(II)complexes and the TEMPO-mediated catalytic oxidation were also reviewed.2.The first terpyridine platinum(II)chromophore-based complex with TEMPO group,[Pt(terpy-TEMPO)Cl]Cl·CH2OH·H2O,was designed,synthesized and characterized.The crystal structure of[Pt(terpy-TEMPO)Cl]Cl·CH2OH H2O was determined by X-ray crystal analysis.As TEMPO group in the complex can efficiently quench the luminescence of the terpyridine platinum(II)chromophore in solid state,while the TEMPO group was converted to TEMPOH,the luminescence was restored.Therefore,through systematic experiments and theoretical calculations,we have interpreted the quenching mechanism in a reasonable way.3.The[Pt(terpy-TEMPO)Cl]Cl·CH2OH·H2O complex has been successfully applied in the catalytic oxidation of benzyl alcohol with assistant of cocatalyst CuCl.It is found that the catalytic activity of[Pt(terpy-TEMPO)Cl]·Cl ·CH2OH·H2O complex is similar to TEMPO.However,more CuCl had to add in the[Pt(terpy-TEMPO)·Cl]·Cl·CH2OH·H2O complex mediated oxidation reaction because of the coordination of CuCl.4.In view of the luminescence properties of[Pt(terpy-TEMPO)Cl].·Cl · CH2OH H2O only in solid state,we have modified this complex on the ancillary ligand and counterion,and successfully synthesized another kind of complex,[Pt(terpy-TEMPO)(C=CPh)](PF6).Then,the structure of the new complex has been characterized in detail,and the spectral properties of the complex are also discussed comprehensively.The modified phenyl acetylene terpyridine platinum(II)chromophore was luminous in solution,room temperature.While after the combination of the TEMPO group,the luminescence of the chromophore was quenched.We explained the quenching mechanism in[Pt(terpy-TEMPO)(C?CPh)](PF6)system with the help of experiments and theoretical calculation.5.We applied[Pt(terpy-TEMPO)(C=CPh)](PF6)complex and the secondary oxidant of bis(acetoxy)iodobenzene(BAIB)in the oxidation of benzyl alcohol.In order to understand more about the quantitative concentration changes of TEMPO/TEMPOH species during the in situ reaction,a strategy of coupled EPR/fluorescence techniques was proposed.Hence,more mechanistic information of reaction rate in each step of the reaction cycle reinforced the previous proposals,and those details of the in situ information allow not only quantificationally detecting the composition of working catalyst,but also modulating the catalytic components for increasing activity.This method highlighted the advantage of the new combining spectroscopic methods,and can be potentially applied in other catalytic reaction in which TEMPO is used as catalyst.6.We summarize the research results and prospect the application of in situ double spectrummethod.In general,the research background of the thesis is the traditional methods of studying oxidation reaction mechanism.Several kinds of homogeneous bifunctional probe catalysts with different spectral properties have been synthesized and developed for the oxidation of benzyl alcohol.A new method of in situ fluorescence-EPR coupled spectroscopy applied in oxidation reaction is established.These results offered a theoretical basis and reliable experimental basis for further related reaction mechanism.The innovation of the thesis is that using the mutually-exclusive fluorescence and EPR spectra in the same molecular system.The bifunctional molecular probes have the dominant properties of EPR signal and the potential properties of fluorescence signal.Dring the reaction process,the fluorescence signal and EPR signal are transformed into each other due to the change of molecular structure.Then,by analyzing the changes of different spectra,we get more new information of oxidation reaction.In addition,owing to the uniqueness of our designed molecules,fluorescence and EPR spectroscopy can complement in one reaction.We believe that the combined method can not only speculate and verify the oxidation reaction mechanism of the related systems,but also provide a new idea for the combination of other in situ spectroscopic methods.