1-苯基-3-(4-硝基苯基)-5-(9-蒽基)-2-吡唑啉分子内高位共轭

Homoconjugation in 5-(9-Anthryl)-3- (4-Nitrophenyl)-1-Phenyl-2-Pyrazoline

通过对1 苯基 3 (4 硝基苯基) 5 (9 蒽基) 2 吡唑啉及其相关化合物的吸收光谱进行比较研究,发现该分子的吸收不同于分子内"Ar—N—N=C—Ar"发色团与蒽发色团的叠加.其中"Ar—N—N=C—Ar"发色团的吸收系数增强了12倍,存在极大的增色效应,蒽的精细吸收峰也均红移了20nm左右.说明两者存在基态下的相互作用.优势构象理论分析表明这是由于基态π电子轨道重叠的高位共轭效应引起的.该发现将有助于解释该类分子激发态下发色团间的非共轭电荷转移以及能量转移,并为寻找更大吸收系数的该类化合物提供了较好的方法.

The UV-Vis spectra of 5-(9-anthryl)-3-(4-nitrophenyl)-1-phenyl-2-pyrazoline(ANPP) and its derivatives were compared.It was found that strong hypsochromical effect exists in 'Ar-N-N=C-Ar' chromophore and bathochromic effect in anthryl group in ANPP.Computational studies demonstrated twisting between the two chromphores.It implies these effects are resulted by intramolecular homoconjugation.This finding will help explaining the unconjugated charge transfer between the two groups in the excited state and provide a new method to increase absorption coefficient of 1,3,5-triarylpyrazoline compounds.