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ScHEME 2: An extended inductive effect afforded a semi-donor-acceptor molecular system.

Figure 4 An extended inductive effect afforded a semi-donor-acceptor molecular system.

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2.5. Color Strength Measurement. The color strength (K/S) of the dyed polyester samples was assessed by applying the high reflectance technique using the Kobelka~Munk equation [K/ S=(1—R)?/2R-(1-R,)*/2R,], where S is the scattering coefficient, K is the absorption coefficient, and (R, R,) are decimal fractions of the reflectance of both dyed and undyed polyester samples, respectively [7]. & (ppm): 177.68, 172.62, 140.26, 134.04, 130.44, 124.75, 115.39, 113.85, 113.19, 111.67, 98.83, 38.21, 29.68, 29.88, 29.73, 26.71, 25.04, 21.55, and 14.67. IR (neat, v/cm7!): 3386 (NH), 2916 (CH aliphatic), 2846 (CH aromatic), 2217 (CN), and 1577 (C=N). MS m/z (%): 428 [M-H]*. Elemental analysis calculated for C.,H3,N50 (429.25): C 72.70, H 7.27, and N, 16.30; found: C 72.83, H 7.19, and N 16.47.
2.5. Color Strength Measurement. The color strength (K/S) of the dyed polyester samples was assessed by applying the high reflectance technique using the Kobelka~Munk equation [K/ S=(1—R)?/2R-(1-R,)*/2R,], where S is the scattering coefficient, K is the absorption coefficient, and (R, R,) are decimal fractions of the reflectance of both dyed and undyed polyester samples, respectively [7]. & (ppm): 177.68, 172.62, 140.26, 134.04, 130.44, 124.75, 115.39, 113.85, 113.19, 111.67, 98.83, 38.21, 29.68, 29.88, 29.73, 26.71, 25.04, 21.55, and 14.67. IR (neat, v/cm7!): 3386 (NH), 2916 (CH aliphatic), 2846 (CH aromatic), 2217 (CN), and 1577 (C=N). MS m/z (%): 428 [M-H]*. Elemental analysis calculated for C.,H3,N50 (429.25): C 72.70, H 7.27, and N, 16.30; found: C 72.83, H 7.19, and N 16.47.
TaBLE 1: UV-visible absorption maxima of dyestuffs 1-3 in dif- ferent solvents. 3.3. Assessment of pH Sensing Effect. The electron- withdrawing functional group on arylhydrazone generates an acidic NH hydrazone proton able to create a conjugate base, or so called an arylhydrazone anion, with an electron- donating ability. This arylhydrazone anion acts as an electron-donating moiety in conjugation with the strong electron-deficient tricyanofuran moiety leading to an in- teresting spectral switch of a donor-acceptor molecular system under pH stimulus [24]. Figure 3 displays the UV- visible absorption spectra and color changes of dye 1 dis- solved in acetonitrile (ca. 2.3x10-° mol-L), under the deprotonation and protonation reversible process. Upon addition of 1.0 mol-L~’ of methanolic solution of tetrabu- tylammonium hydroxide (TBAH) to compound 1 dissolved in acetonitrile to raise the pH value, the maximum ab- sorption wavelength at 451 nm was bathochromically shifted to 538nm. On the contrary, the addition of 1.0 mol-L"! methanolic solution of trifluoroacetic acid (TFAA) resulted in the maximum absorption band at 451nm to reappear, while reducing the pH value.
TaBLE 1: UV-visible absorption maxima of dyestuffs 1-3 in dif- ferent solvents. 3.3. Assessment of pH Sensing Effect. The electron- withdrawing functional group on arylhydrazone generates an acidic NH hydrazone proton able to create a conjugate base, or so called an arylhydrazone anion, with an electron- donating ability. This arylhydrazone anion acts as an electron-donating moiety in conjugation with the strong electron-deficient tricyanofuran moiety leading to an in- teresting spectral switch of a donor-acceptor molecular system under pH stimulus [24]. Figure 3 displays the UV- visible absorption spectra and color changes of dye 1 dis- solved in acetonitrile (ca. 2.3x10-° mol-L), under the deprotonation and protonation reversible process. Upon addition of 1.0 mol-L~’ of methanolic solution of tetrabu- tylammonium hydroxide (TBAH) to compound 1 dissolved in acetonitrile to raise the pH value, the maximum ab- sorption wavelength at 451 nm was bathochromically shifted to 538nm. On the contrary, the addition of 1.0 mol-L"! methanolic solution of trifluoroacetic acid (TFAA) resulted in the maximum absorption band at 451nm to reappear, while reducing the pH value.
SCHEME 1: Synthesis of hydrazone dyes 1-3.
SCHEME 1: Synthesis of hydrazone dyes 1-3.
Figure 2: UV-visible absorption spectra of dyestuffs 1 (a), 2 (b), and 3 (c) in solvents of different polarities.
Figure 2: UV-visible absorption spectra of dyestuffs 1 (a), 2 (b), and 3 (c) in solvents of different polarities.
Figure 3: UV-Vis absorption spectra (a) and the corresponding color variations (b) of the hydrazone dye 1 in acetonitrile (ca. 2.3107 mol-L"!) at a range of pH values (6.62-6.93).
Figure 3: UV-Vis absorption spectra (a) and the corresponding color variations (b) of the hydrazone dye 1 in acetonitrile (ca. 2.3107 mol-L"!) at a range of pH values (6.62-6.93).
Ficure 5: Uptake of the prepared dyestuffs 1-4 on polyester fabrics. Figure 4: Variations in the ratio of the absorbances at 451 and 538 nm of 1 in acetonitrile (ca. 2.3 x 10° mol-L~’) while shifting pH values back and forth between 6.62 and ~6.93.
Ficure 5: Uptake of the prepared dyestuffs 1-4 on polyester fabrics. Figure 4: Variations in the ratio of the absorbances at 451 and 538 nm of 1 in acetonitrile (ca. 2.3 x 10° mol-L~’) while shifting pH values back and forth between 6.62 and ~6.93.
* Alt. = alteration in color; St.= staining on cotton. TABLE 2: Colorfastness, shade, and tinctorial strength of dyed polyester substrates.
* Alt. = alteration in color; St.= staining on cotton. TABLE 2: Colorfastness, shade, and tinctorial strength of dyed polyester substrates.
TABLE 3: Antimicrobial properties of dyestuffs 1-3. Acknowledgments chloride. The molecular structures of dyes were verified by ‘H-NMR and °C-NMR spectra, elemental analysis, and FT-IR spectra. A positive solvatochromism was recorded by UV-visible absorption spectra in a variety of solvents with different polarities. The pH molecular switching ef- fect, accompanied by reversible color changes, was mon- itored by UV-visible spectra as a result of the variation of the pH value leading to the production of charge de- ocalization on the hydrazone dye resulting in extended conjugation through a quinoid form. This stimulated planarity of hydrazone dye resulted from the electron- withdrawing substituents on the arylhydrazone moiety producing higher conjugation extent of the hydrazone anion dye than that of the hydrazone dye. Thus, the pH sensory is displayed via modulating the intramolecular charge transfer changed by deprotonation/protonation processing. The prepared dyestuffs were applied on polyester substrates by the high-temperature and -pressure technique to give good depths of shades from yellow, orange, and orange-red. The studied dyestuffs displayed mostly satisfactory colorfastness properties. We also ex- plored the application of the hydrazone dyes as potential substances with antimicrobial efficiency against some pathogenic species. Dyes comprising electron-donating groups on the arylhydrazone moiety demonstrated mod- erate antimicrobial activities, while dyes with highly electron-withdrawing groups on the arylhydrazone dis- played weaker antimicrobial activities.
TABLE 3: Antimicrobial properties of dyestuffs 1-3. Acknowledgments chloride. The molecular structures of dyes were verified by ‘H-NMR and °C-NMR spectra, elemental analysis, and FT-IR spectra. A positive solvatochromism was recorded by UV-visible absorption spectra in a variety of solvents with different polarities. The pH molecular switching ef- fect, accompanied by reversible color changes, was mon- itored by UV-visible spectra as a result of the variation of the pH value leading to the production of charge de- ocalization on the hydrazone dye resulting in extended conjugation through a quinoid form. This stimulated planarity of hydrazone dye resulted from the electron- withdrawing substituents on the arylhydrazone moiety producing higher conjugation extent of the hydrazone anion dye than that of the hydrazone dye. Thus, the pH sensory is displayed via modulating the intramolecular charge transfer changed by deprotonation/protonation processing. The prepared dyestuffs were applied on polyester substrates by the high-temperature and -pressure technique to give good depths of shades from yellow, orange, and orange-red. The studied dyestuffs displayed mostly satisfactory colorfastness properties. We also ex- plored the application of the hydrazone dyes as potential substances with antimicrobial efficiency against some pathogenic species. Dyes comprising electron-donating groups on the arylhydrazone moiety demonstrated mod- erate antimicrobial activities, while dyes with highly electron-withdrawing groups on the arylhydrazone dis- played weaker antimicrobial activities.
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