香豆素衍生物的TICT态和荧光介质效应

TICT State and Medium Effects on Fluorescence of Coumarin Derivatives

研究了八种７－氨基香豆素衍生物在纯溶剂和二元溶剂体系中的荧光特性．这些衍生物因氨基上Ｈ的取代程度的不同，在溶液中可以形成两种不同的氢键．一种是由溶剂分子提供Ｈ，在香豆素环的２位氧原子上形成的氢键；另一种是由溶质分子提供Ｈ，在香豆素衍生物的７－氨基上形成的氢键．由于前者能使香豆素衍生物在极性溶剂中形成的ＴＩＣＴ态更稳定，后者则不利于ＴＩＣＴ态的形成，从而对其荧光波长和强度产生了不同的影响．

Fluorescence properties of 8 kinds of 7 aminocoumarin derivatives in pure or binary mixed solvents were studied. In protonic solvents, two different hydrogen bonds can be formed between solvent and solute dependent on substitution of hydrogen of amino group of the derivatives. When the derivatives are excited, a solvent solute hydrogen bond at the carbonyl group in 2 position is formed for all of the derivatives, where the H belongs to the solvent. Besides derivatives that carry one or two H atoms at amino group in 7 position, another solute solvent hydrogen bond, where H belongs to the amino group of the derivatives, can be also formed. The former makes the nonradiative twisted intramolecular charge transfer(TICT) state of the derivatives more stable, leading to a rapid decrease in intensity of emission, but the latter hinders formation of the TICT state. In those two cases, the formation of the hydrogen bonds make the molecular excited state more stable and its energy diminishes leading to the red shift in the maximum fluorescence wavelength.