Effects of Structure and Environment on the Spectroscopic Properties of (3-Amino-Substituted-Thieno[2,3-b] Pyridine-2-yl)Pyridine/Quinolin-2-yl)(Phenyl)Methanones: Experimental and Theoretical Study

详细信息    查看全文

• 作者：Ibrahim Ahmed Z. Al-Ansari
• 刊名：Journal of Fluorescence
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：26
• 期：3
• 页码：821-834
• 全文大小：1,113 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Biomedicine
  Biomedicine
  Biophysics and Biomedical Physics
  Biotechnology
  Biochemistry
  Analytical Chemistry
  
• 出版者：Springer Netherlands
• ISSN：1573-4994
• 卷排序：26

文摘

The electronic absorption, excitation and fluorescence properties of two 3-amino-substituted-thieno[2,3-b]pyridine/quinolin-2-yl)(phenyl)methanones; (referred to as compounds 1–2: where 3-amino-4,5,6-trimethyl-thieno[2,3-b]pyridin-2-yl)(phenyl)methanone (1); and 3-amino-5,6,7,8-tetrahydro-thieno[2,3-b]quinolin-2-yl)(phenyl)methanone (2)) have been investigated in solvents of various polarity and hydrogen-bonding abilities. Results based on the electronic absorption, excitation and emission study of these compounds; indicated that singlets (S₁ and S₂) excited-states are populated in non-polar and polar protic/aprotic solvents giving dual fluorescence with weak charge transfer separation. The experimental results were interpreted with the aid of quantum chemistry calculations carried out with the DFT and TD-DFT/B3lyp/6–31 + G(d,p) methods. Based on these calculations, compounds 1–2 exist in two rotamers: anti and syn, separated by ca. 5–6 kcal mol−1 energy barriers in favor of the anti-conformer. The anti-structure, was shown to be stabilized through existence of intramolecular NH…O hydrogen bond (H-b), which plays a dominant role in affecting the energy of the HOMO-1 molecular orbital. Further, methyl/alkyl substitution in the pyridyl-thiophene ring was shown to involve in σ-π hyper-conjugation and destabilization of the HOMO-1 MO’s.KeywordsAbsorptionFluorescenceIntramolecular charge-transferHydrogen bondingDensity functional theoryTime-dependent density functional theoryAnd solvatochromism