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Hydrogen‐bonding‐based thermochromic phenol–amine complexes
Author(s) -
Mizutani Tadashi,
Takagi Hideki,
Ueno Yoshiyuki,
Horiguchi Takuya,
Yamamura Kimiaki,
Ogoshi Hisanobu
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(1998100)11:10<737::aid-poc36>3.0.co;2-p
Subject(s) - chemistry , thermochromism , hydrogen bond , amine gas treating , photochemistry , pyridine , phenol , triethylamine , butylamine , organic chemistry , polymer chemistry , molecule
Variable‐temperature UV–vis, 13 C NMR and IR studies showed that proton‐transferred complexes were formed between phenols and amines in apolar solvents at low temperature. Upon cooling a solution of p ‐nitrophenol and diisopropylamine in toluene, the colour of the solution changed from colourless to yellow. This thermochromism was ascribed to the proton transfer in the hydrogen‐bonding complex. Under UV–vis conditions, butylamine and imidazole also caused similar thermochromism upon complexation with p ‐nitrophenol, while triethylamine, quinuclidine and pyridine did not. The thermochromic behaviour was particularly dependent on the stoichiometry of the amine and the phenol: a solution of 3,3′‐dibromo‐5,5′‐dinitro‐2,2′‐biphenyldiol and diisopropylamine with a molar ratio of 1:1 showed no thermochromism, while solutions with 1:2 or higher ratios showed thermochromism, indicating that excess amine is required to obtain the proton‐transferred species. These results revealed that the proton‐transferred species forms in apolar solvents at low temperature if an appropriate hydrogen‐bonding network between the phenol and the amine can stabilize it. © 1998 John Wiley & Sons, Ltd.