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Water‐Assisted Emission Enhancement of 2‐Hydroxynaphthaldoxime and Related Compounds
Author(s) -
Tarai Arup,
Baruah Jubaraj B.
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201803030
Subject(s) - tetrabutylammonium hydroxide , fluorescence , chemistry , titration , naphthalene , hydroxide , intramolecular force , photochemistry , cocrystal , excited state , chloride , molecule , fluorescence spectroscopy , inorganic chemistry , hydrogen bond , organic chemistry , physics , quantum mechanics , nuclear physics
The combined contributions from the excited‐state intramolecular proton‐transfer and aggregation‐induced emission in the photoluminescence of compounds namely 2‐hydroxynaphthaldoxime, 2‐methoxynaphthaldoxime, 2‐hydroxynaphthaldehyde and 1‐[(methylimino)methyl]naphthalen‐2‐ol were established. For such a purpose the changes in the fluorescence emission of these compounds in different solvents upon addition of water and from the fluorescence emission life‐time decay profiles were studied. 1 H‐NMR titration of the 2‐hydroxynaphthaldoxime with D 2 O had provided clear evidence on the role of water molecules to disrupt the C−H⋅⋅⋅O interactions in assembly of 2‐hydroxynaphthaldoxime to orient the aromatic naphthalene rings differently to enhance the fluorescence emissions. Dynamic light scattering studies and scanning electron micrographs had showed that there were differences between the types of aggregation present in solid state and in solution. In solution the average size of the aggregates of 2‐hydroxynaphthaldoxime were increased upon addition of water. 2‐Hydroxynaphthaldoxime formed well defined cocrystal with tetrabutylammonium chloride but the tetrabutylammonium hydroxide formed salt of 2‐hydroxynaphthaldoxime by deprotonating hydroxy‐group. Accordingly the fluorescence emission changes of 2‐hydroxynaphthaldoxime caused by tetrabutylammonium hydroxide was different from the emission showed by the cocrystal with tetrabutylammonium chloride.