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Spectrochim Acta A Mol Biomol Spectrosc. 2017 Feb 15;173:556-561. doi: 10.1016/j.saa.2016.10.017. Epub 2016 Oct 17.

Thermohalochromism of phenolate dyes conjugated with nitro-substituted aryl groups.

Author information

1
Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
2
Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile. Electronic address: marcos.caroli@usach.cl.
3
Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.

Abstract

The cationic halochromism and thermohalochromism of four phenolate dyes conjugated with aryl moieties substituted with one or two nitro groups were investigated in the presence of organic (tetra-n-butylammonium bromide and benzyltriethylammonium chloride) and inorganic (sodium perchlorate) salts, in hydrogen-bond donating (water, 1-propanol, 1-butanol and 2-propanol) and hydrogen-bond accepting (acetonitrile and dimethylsulfoxide) solvents. Although a positive halochromic response was observed in water for tetraalkylammonium salts, their thermohalochromic behavior was negligible. A negative halochromic behavior was observed for the dyes in all solvents, when the added cation was Na+. Plots of Δλmaxvs. c (Na+) allowed the apparent association constants for the solvated phenolate-cation pair to be estimated. In most cases, a positive thermohalochromism was observed in the range of 25-50°C, exceptions being the more sterically hindered phenolate dyes in the less polar solvents 2-propanol and acetonitrile. The observed variations were rationalized by invoking the effect of temperature on the phenolate-cation, phenolate-solvent and cation-solvent interactions.

KEYWORDS:

Cationic halochromism; Conjugated polynitroaryl phenolate dyes; Thermohalochromism

PMID:
27780125
DOI:
10.1016/j.saa.2016.10.017

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