Studies Of The Synthesis And Fluorescence Properties Of Novel N,O Chelated BF₂ Complexes

In recent decades,as a kind of novel organic fluorescent dye BODIPYs has a wide range of applications in laser dyes,biological cell imaging,photodynamic therapy,fluorescent probes,the organic light emitting diode（OLED）and many other fields,due to their excellent photophysical properties.So it is of great significance to develop new organic fluorescent compounds with better performance.In this dissertation,20 novel N,O-chelate BF₂ complexes were synthesized and their fluorescence properties were carefully studied.Six BF₂ complexes 2a-2f were synthesized by 2-amino benzothiazole and benzoyl chloride,and the yields were 70%-81%.Then their fluorescence properties were investigated.These complexes exhibited good fluorescence in solution and in the solid state,in which the stokes shifts were 80-100 nm.When using nonpolar solvent or introducing electron-donating groups onto the phenyl ring（R₂）,the fluorescence intensity increased.In particular,the aggregation-induced emission effect（AIEE）of 2a-2f was founded.Four BF₂ complexes 7a-7d were synthesized starting from substituted benzoic acid and thiosemicarbazide,and the yields were 41%-74%.Then their fluorescence properties were investigated.These complexes exhibited good fluorescence in solution and in the solid state,in which the stokes shifts were 58-87 nm.When using nonpolar solvent or introducing electron-donating groups onto the phenyl ring（R₁,R₂）,the fluorescence intensity increased.In particular,the aggregation-induced emission effect（AIEE）of 7a-7d was founded.In addition,the complexes showed good stability in acidity,but quenched when pH（29）10.Six BF₂ complexes 12a-c,13a-c were synthesized by 4-hydroxycoumarin,and the yields were 60%-89%.Then the fluorescence properties of complexes 12a-c,13a-c and coumarin-pyrazoline derivatives 10a-c,11a-c were investigated.These compounds exhibited good fluorescence in solution and in the solid state,but BF₂complexes perform better.The hydrogen on the pyrazoline ring was replaced by phenyl,which can make the fluorescence from green to yellow.In addition,the fluorescence of complexes 12a increased at basic pH.Two BF₂ complexes 15a-b were synthesized by coumarin-pyrazoline derivatives11a-b,and the complexes 18a-b were synthesized starting from 4-hydroxycoumarin.Their yields were 86%-87%,89%-91%,respectively.Then the fluorescence properties of complexes and coumarin-pyrazole derivatives were investigated.These compounds exhibited bule fluorescence in solution and in the solid state,but BF₂complexes perform better.Complexes 15a-b,18b and coumarin-pyrazole derivatives14a-b,17b displayed better quantum yield in toluene and chloroform,while 18a,17a displayed in DMF.In addition,these compounds exhibited good fluorescence at acid pH,but didn’t show selectivity and specificity to cation.