TY - JOUR
T1 - Additivity of substituent effects on the visible absorption spectra of some heteroarylazo compounds: the influence of solvent
AU - Hutchings, Michael G.
AU - Mills, Andrew
PY - 2000/10/4
Y1 - 2000/10/4
N2 - Pronounced solvatochromic shifts are observed in the visible spectra of two series of heteroarylazobenzene derivatives based on m-acetylamino- and m-methyl-N,N-diethylaniline, measured in various solvents. The heteroaryl azo component of these dyes can be viewed as a thiophene ring substituted by cyano, nitro, alkoxycarbonyl, or ring aza (to give thiazole and isothiazole derivatives). Free-Wilson analysis has shown that the influence of each of the substituents is constant across all molecules within the two series for a given solvent. However, the substituent increments vary between different solvents and correlate with the Kamlet-Taft dipolarity/polarisability parameter pi* of the solvents. There appears to be no intuitive explanation for the relative solvent variation of different substituents, but Onsager theory suggests sensitivity to the relative size and shape of the dyes. Visible absorption maxima are predicted for unknown heteroarylazo compounds related to those studied.
AB - Pronounced solvatochromic shifts are observed in the visible spectra of two series of heteroarylazobenzene derivatives based on m-acetylamino- and m-methyl-N,N-diethylaniline, measured in various solvents. The heteroaryl azo component of these dyes can be viewed as a thiophene ring substituted by cyano, nitro, alkoxycarbonyl, or ring aza (to give thiazole and isothiazole derivatives). Free-Wilson analysis has shown that the influence of each of the substituents is constant across all molecules within the two series for a given solvent. However, the substituent increments vary between different solvents and correlate with the Kamlet-Taft dipolarity/polarisability parameter pi* of the solvents. There appears to be no intuitive explanation for the relative solvent variation of different substituents, but Onsager theory suggests sensitivity to the relative size and shape of the dyes. Visible absorption maxima are predicted for unknown heteroarylazo compounds related to those studied.
KW - heteroarylazo
KW - solvatochromism
KW - substituent additivity
KW - Kamlet-Taft
KW - Onsager theory
UR - http://dx.doi.org/10.1016/S0143-7208(00)00060-7
U2 - 10.1016/S0143-7208(00)00060-7
DO - 10.1016/S0143-7208(00)00060-7
M3 - Article
SN - 0143-7208
VL - 47
SP - 23
EP - 31
JO - Dyes and Pigments
JF - Dyes and Pigments
IS - 1-2
ER -