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Absorption spectra and tautomerism of aminonaphthazarins
Author(s) -
Shirai Kazuko,
Oshida Atsushi,
Matsuoka Masaru
Publication year - 1998
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1998.tb01947.x
Subject(s) - tautomer , bathochromic shift , chemistry , deprotonation , alkali metal , absorption spectroscopy , absorption (acoustics) , quinone , photochemistry , computational chemistry , medicinal chemistry , stereochemistry , organic chemistry , materials science , ion , physics , composite material , fluorescence , quantum mechanics
2‐n‐Butylaminonaphthazarin (2) absorbs at 499 and 532 nm in ethanol but at 539 and 577 nm in alkali solution, while 2, 6‐bis(n‐butylamino)naphthazarin (3) absorbs at 461, 500 and 540 nm in ethanol but at 511 and 545 nm in alkali solution, with only a small bathochromic shift of 5 nm. The absorption curve of 3 was changed by addition of alkali and the λD max at around 461 nm completely disappeared. In the case of 2‐bromo‐3, 6‐bis(n‐butylamino)naphthazarin (4), tautomerism between the 1, 4‐quinone and 1, 5‐quinone forms was observed and the isosbestic point was observed at 480 nm. Dye 2 easily deprotonated to give the 1, 4‐dianion, but dyes 3 and 4 existed as tautomeric mixtures in solution and shifted to 1, 5‐quinone forms in alkali solution.