The ESIPT Of Spiropyrans And Their Positive And Negative Photochromism

Due to its unique photochromic properties,spiropyrans have the potential of being widely used and have made a huge progress.However,the existed spiropyrans still have some defects,which limit their applications in the field of Molecular Fluorescent Switches.Most ring-opening spiropyranes are unstable,which is not conducive to the retention of information for a long time.The fluorescence intensity of ring-opening bodies is low due to the non-radiative transition of fluorescence,which limits the application of fluorescent molecular switches.And the fatigue resistance is poor,which is not conducive to the re-use.To solve these problems,we tried to introduce hydroxyflavone structure into spiropyran molecule which will expand conjugated system of MC and we observed their excited state intramolecular proton transfer（ESIPT）characteristics.We studied the positive and negative photochromism of carboxyl-formyl-spiropyran and incorporated spiropyran into calcium nanomaterial as a rigid matrixes to make spiropyran out of solution system,which will improve the performance of spiropyran and broaden its application range.The first part of the dessertation gives a detailed overview of the photochromic materials,spriropyrans,flavonoids and nanocomposites,and puts forward the basis and purpose of this topic.The second part,a series of new spiropyran compounds were designed and synthesized.Hydroxyflavone was synthesized from 3-（Dimethoxymethyl）-2-hyd roxy-5-methylbenzaldehyde and hydroxyacetophenone by AFO synthesis method,and then a series of flavone-spiropyran compounds,3-hydroxy-2-（1’,3’,3’,6-tetra methylspiro[chromene-2,2’-indolin]-8-yl）-4H-chromen-4-one（SPHF）,8-（3-hydroxy-4-oxo-4H-chromen-2-yl）-1’,3’,3’,6-tetramethylspiro[chromene-2,2’-indoline]-5’-carbo xylic acid（1SPHF）and 8-（3-hydroxy-4-oxo-4H-chromen-2-yl）-1’,3’,3’,6-tetramethy lspiro[chromene-2,2’-indoline]-4’,6’-dicarboxylic acid（2SPHF）were synthesized b y Hydroxyflavone and different indolines.In addition,a series of aldehyde spir opyrans,1’,3’,3’,6-tetramethylspiro[chromene-2,2’-indoline]-8-carbaldehyde（FSP）,8-formyl-1’,3’,3’,6-tetramethylspiro[chromene-2,2’-indoline]-5’-carboxylic acid（SC-FSP）and 8-formyl-1’,3’,3’,6-tetramethylspiro[chromene-2,2’-indoline]-4’,6’-dicarbox ylic acid（DC-FSP）were synthesized from 3-（Dimethoxymethyl）-2-hydroxy-5-met hylbenzaldehyde and different indolines.All the compounds were fully character ized by ¹H NMR spectroscopy,¹³C NMR spectroscopy,IR spectroscopy,and hi gh resolution mass spectrometry.The third part is about the fluorescence emission spectrum of flavone-spiropyran compounds.MC fluoresces was found that can be detected only in solid state,the carboxyl group on indoline weakened its fluorescence intensity,and this spiropyrans in solution mainly displayed SP fluorescence.If the ring was opened in solution,the fluorescence was weakened or quenched.The ESIPT was very easy to occur in SP,the double fluorescence peaks of SPHF and 1SPHF were not obvious,and 2SPHF showed double fluorescence peaks because of the dicarboxyl group.The solvent and light affected the fluorescence intensity by affecting the open and closed state of spiropyrans.The fluorescence was quenched by the acid,and the fluorescence or double fluorescence was enhanced in the alkaline solution.When the aforementioned photochromic spiropyran ligands were used to coordinate with transition metal,the change in fluorescence depended on the metal valence electron layer and the rigidity of the complexes.The fluorescence was weakened or quenched after the coordination with the metal ions which contain the unfilled outer d orbital(such as Fe³⁺and Cu²⁺),and was enhanced by the increase of molecular stiffness of the complexes of Zn²⁺and Mg²⁺.La³⁺,Gd³⁺and Lu³⁺showed fluorescence in different wavelength in lanthanide metals because of the special distribution of electrons in 4f orbital.The flavone-spiropyran counld be used as a probe to distinguish La³⁺（no f electron）,Gd³⁺（semi-full f）and Lu³⁺（f is full）in lanthanide metals.The fourth part of the thesis studies some factors of photochromism in DC-FSP,such as solvent,water and p H.It was showing that the direction of photochromism was turned by changing the energy level of the two bistable states.The addition of water,acid and base in organic solvent can reduce the energy of MC and increase the proportion of MC in the solution.When the energy of MC is lower than SP,the reverse photochromic phenomenon was showed instead of the photochromic phenomenon,such as the acidic Et OH solution of FSP and the Et OH（50%）solution of FSP and DC-FSP.The carboxyl group on indoline decreased the stability of MC in solution.The DC-FSP calcium phosphate nanocomposites exhibited good positive photochromism and have the advantages of strong plasticity,simple operation and low cost.