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Hydrophobic effects on photophysical and photochemical processes: 4. The conformation of polymethylene bis‐β‐naphthoates in poor solvents and their intramolecular excimer
Author(s) -
ChengBai Xu,
YongYong Liu,
HanSen Shou,
ChenHo Tung
Publication year - 1988
Publication title -
acta chimica sinica english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 0256-7660
DOI - 10.1002/cjoc.19880060208
Subject(s) - chemistry , intramolecular force , excimer , photochemistry , chromophore , fluorescence , ethylene glycol , methylene , ground state , enthalpy , sulfoxide , dimethyl sulfoxide , stereochemistry , organic chemistry , physics , quantum mechanics
The fluorescence properties of polymethylene bis‐β‐naphthoates with various chain lengths (B n ) in poor solvents such as dimethyl sulfoxide‐water (DMSO–H 2 O) and ethylene glycol‐water(EG–H 2 O) were measured under stationary and nonstationary conditions at various temperatures. Hydrophobic interactions bring the two chromophores of B 3 , B 4 and B 10 into sandwich arrangement in ground state, thus promote intramolecular excimer formation upon excitation. The perfect overlapping structure of B 2 can not be formed in ground state because of the eclipsed conformation of two methylene groups in such a sandwich arrangement. The favorable conformation of B 2 is the structure in which the two naphthyl rings are in proximity. The activation energy, enthalpy and entropy changes of excimer formation of B 2 were calculated from the fluorescence decay parameters.