Bakalova Snezhana M, Kaneti Jose
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 9, 1113 Sofia, Bulgaria.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 Feb;72(1):36-40. doi: 10.1016/j.saa.2008.07.020. Epub 2008 Jul 26.
Vertical S(1)-S(0) electronic transitions of the highly solvent-sensitive fluorescence label 2-propionyl-6-dimethylamino naphthalene (PRODAN) are modeled by semiempirical CISD AM1 and TD DFT calculations in a large number of solvents of different polarity and hydrogen donating ability. Calculations correctly reproduce the observed solvent induced shifts of the emission maxima. The fluorescence Frank-Condon transition energies in solvent can be predicted quantitatively at the AM1 SM5.42 OPEN(2,2) C.I.=5 CISD level. For the planar PRODAN emitting state at the latter level we obtain a regression with practically unit slope and zero intercept for aprotic solvents. The respective relationship for the O-twisted S(1) state has a slope of 0.59 and intercept of 9100 cm(-1). These results support the concept that no geometry twist in the S(1) state of PRODAN is necessary to explain the observed solvent effects on fluorescence.
通过半经验的CISD AM1和TD DFT计算，在大量不同极性和给氢能力的溶剂中对高溶剂敏感性荧光标记物2-丙酰基-6-二甲基氨基萘（PRODAN）的垂直S(1)-S(0)电子跃迁进行了模拟。计算结果正确地再现了观察到的发射最大值的溶剂诱导位移。在AM1 SM5.42 OPEN(2,2) C.I.=5 CISD水平下，可以定量预测溶剂中的荧光弗兰克-康登跃迁能量。对于处于后一水平的平面PRODAN发射态，我们得到了非质子溶剂的回归关系，其斜率几乎为1，截距为零。对于O-扭曲的S(1)态，相应的关系斜率为0.59，截距为9100 cm(-1)。这些结果支持了这样一种观点，即PRODAN的S(1)态无需几何扭曲就能解释观察到的溶剂对荧光的影响。
