Temperature and solvent effects on rotamer-specific photobehaviour of the cis and trans isomers of 2-styrylanthracene
作者:Anna Spalletti、Giampiero Bartocci
DOI:10.1039/a906176b
日期:——
The photochemical and photophysical behaviour of the two stereoisomers of 2-styrylanthracene (2-StAn) has been investigated as a function of temperature and solvent polarity. The photobehaviour of both the trans and cis isomers markedly depends on the 1Lb or 1(La–Bu) nature of the two lowest singlet excited states and on their energy gap. Furthermore, the deactivation channels of the excited states are markedly dependent on conformer geometry, which produces rotamer-specific photoreactive pathways. The excited state properties were investigated by stationary and pulsed fluorimetric techniques and by laser flash photolysis. This paper reports the photophysical and photochemical parameters of the different conformational geometries (rotamers) of trans-2-StAn and cis-2-StAn. The role played by an upper excited singlet state (S2) of the long-lived B rotamer of trans-2-StAn on the relaxation properties (radiative and reactive) of its S1 state is also discussed. The new and relevant experimental and calculation results, reported in this paper, allow a complete and revised picture of the conformational equilibria and the radiative and radiationless relaxation rate parameters of the two geometrical isomers of 2-StAn to be obtained.
研究了 2-苯乙烯基蒽 (2-StAn) 两种立体异构体的光化学和光物理行为随温度和溶剂极性的变化。反式和顺式异构体的光行为明显取决于两个最低单线激发态的 1Lb 或 1(La-Bu) 性质及其能隙。此外,激发态的失活通道明显依赖于构象异构体几何形状,从而产生旋转异构体特异性的光反应途径。通过固定和脉冲荧光技术以及激光闪光光解研究激发态特性。本文报道了反式-2-StAn 和顺式-2-StAn 不同构象几何形状(旋转异构体)的光物理和光化学参数。还讨论了反式-2-StAn 的长寿命 B 旋转异构体的上部激发单线态 (S2) 对其 S1 态的弛豫特性(辐射和反应)所起的作用。本文报道的新的相关实验和计算结果可以获得 2-StAn 两种几何异构体的构象平衡以及辐射和无辐射弛豫率参数的完整和修订图。