Study On Fluorescence Properties Of Coumarin Imidazole And BODIPY Derivatives

Fluorescent compounds have attracted much attention since they were discovered.Among various fluorescent compounds,coumarin attracts the attention of researchers due to their high fluorescence quantum efficiency,excellent photo-physics and photochemistry.Another fluorescent dye members,BODIPY,are also favored by researchers because of its highly emission quantum yield,insensitivity to the environment（polarity and p H）,and optical stability.Therefore,a series of compounds based on coumarin and BODIPY,were configured and detailed emission properties were investigated.In the second chapter,a series of new coumarin based fluorescent compounds were synthesized by simply condensation of 7-diamino-coumarin-3-formaldehyde and benzoyl,in which two benzene rings were attached to coumarin with imidazole being as the bridge unit.Both the benzene rings and imidazole ring are connected to coumarin by carbon-carbon single bonds,allowing freely rotation around the single bond.The twisted molecular conformations can be applied to avoid a regular molecule packing,thus leading to strong emission in aggregation states.Additionally,selective carbon substitutes,such as alkyl or aromatic carbon rings,can be anchored to it by electrophilic attack.The additional substituted attaching enhanced the dissertation of molecular,which can be used to regulate the fluorescence emission both in solution and aggregation states.For this end,a series of coumarin derivatives with imidazole and different attachment on the imidazole ring were synthesized and characterized fully.Detailed absorption/emission behaviors were investigated,including emission efficiency,lifetime and related physical parameters.In the third chapter,diarylethene units were introduced to the coumarin-imidazole framework by condensation between 7-diethylamino-coumarin-3-formaldehyde and 1,2-bis（2,5-dimethylthiophen-3-yl）ethane-1,2-dione.Based on the above "one-pot" condensation,bisthienylethene units were attached to coumarin by imidazole ring.The relationship between photochromism and emission behavior were investigated.It demonstrates that the UV induced photo-cyclization could induced a gradually emission quench.Also,the photochromic activity was not suppressed by the strong emission of coumarin.Furtherly,different bulky substitutes were introduced to the imidazole ring,which can be used to regulate the distribution of favored photochromic conformations of bisthienylethene,anti-paralleled hexatriene structure.A newly strategy was established for the molecular configuration and advanced light-responsive materials.In the fourth chapter,aldehyde group was introduced to the β-position by Vilsmeier-Haack reaction and yielded a key intermediated for the following synthesis.2,3-Diaminomaleonitrile was condensed with the introduced aldehyde group and configured a Cu²⁺ sensitive unit to the BODIPY framework.In addition,phenylacetylene derivatives were bonded to another β-position of BODIY to expand the conjugate system for the regulation of emission redshift.Once electron-donating type phenylacetylene derivatives were attached to the BODIPY by Sonogashira coupling,a D-π-A system was established.Due to the rapid isomerization of C=N bonds,the emission of BODIPY was significant quenched,together with the strong electron transfer from amino to BODIPY in the excited states.However,the emission of BODIPY can recovered by addition of Cu²⁺ based on the rapid cyclization induced by Cu²⁺,yielding a stable imidazole ring.Our investigation demonstrates that the emission responsive is highly sensitive toward Cu²⁺ in acetonitrile,even if there exists of various competing metal ions.The Cu²⁺ induced emission signal enhance was estimated to 7 fold.The detection limit was 2.0×10-7 M.In addition,this Cu²⁺ recognition was also can be realized in He La cells.In the fifth chapter,photochromic bisthienylethen unit was introduced to HABIs,a typical radical photochromism system,in which an ultrafast photochromism can be induced by radical.Two different photochromic units were incorporated to one molecule for the more complex logic control.However,the final target molecule was not finished due to the time limitation.Only the important intermediates were synthesized and characterized,together with the presentation of simple photochromic behavior.