Effect of molecular structure and hydrogen bonding on the fluorescence of hydroxy-substituted naphthalimides
作者:László Biczók、Pierre Valat、Ve´ronique Wintgens
DOI:10.1039/a904520a
日期:——
Fluorescence properties of hydroxy-naphthalimides were studied in methylene chloride in the absence and the presence of hydrogen-bonding additives. The position of the HO-substituent only slightly affects the radiative rate, however, the triplet yield and the rate of the radiationless processes are considerably higher for the 3-hydroxy derivative. Addition of nitrogen-heterocyclic compounds leads not only to hydrogen-bonding in the ground state but also fluorescence quenching. The parallel change throughout the series of the hydrogen-bond acceptors between the proton affinity and the rate constants of dynamic quenching indicates that proton displacement plays a crucial role in the excited hydrogen-bonded complexes. Interaction of hydroxy-naphthalimides with pyridine and benzoxazole results in rapid radiationless deactivation from the singlet excited state, whereas intense emission as well as long fluorescence lifetime characterize imidazole and pyrazole complexes. The dual emission of the imidazole complexes observed in solvents of medium polarity is assigned to two conformers which differ in the extent of the proton shift along the hydrogen-bond.
在二氯甲烷中,研究了羟基萘二甲酰亚胺在氢键添加剂存在和不存在情况下的荧光性质。HO-取代基的位置仅对辐射速率产生轻微影响,然而,3-羟基衍生物的三重态产率和无辐射过程的速率要高得多。氮杂环化合物的添加不仅会导致基态中的氢键,还会导致荧光淬灭。氢键受体在质子亲和力和动态淬灭速率常数之间的平行变化表明,质子位移在激发氢键复合物中起着至关重要的作用。羟基萘二甲酰亚胺与吡啶和苯并恶唑的相互作用会导致从单线态激发态快速无辐射失活,而咪唑和吡唑复合物则具有强烈的发射和较长的荧光寿命。在中等极性的溶剂中观察到的咪唑复合物的双重发射被归因于两种构象,它们在氢键沿线的质子位移程度方面有所不同。