Solvatochromic investigation of highly fluorescent 2-aminobithiophene derivatives

被引:43
作者
Bolduc, Andreanne [1 ]
Dong, Yanmei [1 ]
Guerin, Amelie [1 ]
Skene, W. G. [1 ]
机构
[1] Univ Montreal, Dept Chem, Lab Caracterisat Photophys Mat Conjugues, Montreal, PQ H3C 3J7, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
TRIPLET ABSORPTION-SPECTRA; ALPHA-OLIGOTHIOPHENES; ORGANIC-MOLECULES; AZOMETHINES; BEHAVIOR;
D O I
10.1039/c2cp40293a
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The solvatochromic and electrochemical properties of electronic push-pull 2-aminobithiophenes consisting of an aldehyde and nitro withdrawing groups were examined. With the use of an integrating sphere, the absolute quantum yields of the bithiophenes were measured. They were found to be highly fluorescent (Phi(fl) > 70%), provided the nitro group was not located in the 4'-position. High fluorescence yields were observed regardless of solvent, except for alcohols, notably methanol and ethanol. Cryofluorescence was used to probe the bithiophene temperature dependent excited state deactivation modes. The singlet excited state deactivation mode other than fluorescence was found to be internal conversion involving rotation around the thiophene-thiophene bond. Deactivation by intersystem crossing to the triplet state occurred in ca. 40% only for the unsubstituted 2-aminobithiophene. In contrast, the fluorescence was quenched by photoinduced intramolecular electron transfer when the nitro group was located in the 4'-position of the bithiophene. Both the absorbance and fluorescence of the bithiophenes were found to be solvatochromic with more pronounced solvent dependent shifts being observed with the fluorescence. In fact, both the fluorescence and Stokes shifts were linearly dependent on the E-T(30) solvent parameter. Deviations from the linear trend of the Stokes shift with E-T(30) were observed in ethanol and methanol as a result of intermolecular hydrogen abstraction from the solvent and by the excited nitro group. The oxidation potential of the bithiophenes was also highly dependent on the type and number of the electron withdrawing substituents, with values ranging between 0.8 and 1.2 V vs. SCE.
引用
收藏
页码:6946 / 6956
页数:11
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