Spectral behaviour and solvent effects of some aminoanthraquinone dyes

Abstract

The electronic absorption spectrum of each of nineteen AAQ dyes has been studied in nine different organic solvents. The acid dissociation constants of dyes containing OH, COOH, or SO3H groups have also been determined experimentally. The spectra in ethanol display five bands in the uv region and one in the visible region (450–560 nm). This band is assigned to CT transitions of the type l–aπ which result from the interaction of the lone pair of the nitrogen atom with the phenyl ring of the carbonyl group. The CT nature of the band was supported theoretically and by the effect of solvent on band position.

Nanoconstructions based on double-stranded nucleic acids

“…An addition of CuCl 2 solution to the DNA LCD treated by DAU and having an equilibrium value of the amplitude of the band at λ ∼ 500 nm results not only in a many-fold increase (amplification) of this band, but also a band located in the UVregion of the spectrum (curve 3) (the bands at λ ∼ 500 nm and λ ∼ 300 nm are characteristic of the CD spectrum of linear, isotropic DAU-Cu 2+ complexes; this reflects the existence of low-(λ ∼ 500 nm) and high-(λ ∼ 300 nm) energy electronic transitions in DAU moieties [21][22][23][24] of the complexes. These two bands are maintained at the formation of a complex between the linear DNA and DAU [25]).…”

pH- and temperature-responsive redox behavior of hydroxyanthracenediones

“…5) lacks the signal corresponding to a C = O centered n À s à transition, presumably due to the involvement of the C = O group in hydrogen bonding with OH groups at positions 1 and 4. The peaks appearing around 226, 250 and 281 nm are assigned to p À p à transitions of benzenoid and quinonoid systems [41,42]. The broad band at 435 nm, which is absent in the absorption spectrum of simple anthracenedione, appears in the spectra of the three ACDs studied here due to the charge transfer (CT) mechanism [41] of the electron- donating effect of the hydroxyl groups attached to the aromatic rings.…”

“…The peaks appearing around 226, 250 and 281 nm are assigned to p À p à transitions of benzenoid and quinonoid systems [41,42]. The broad band at 435 nm, which is absent in the absorption spectrum of simple anthracenedione, appears in the spectra of the three ACDs studied here due to the charge transfer (CT) mechanism [41] of the electron- donating effect of the hydroxyl groups attached to the aromatic rings. The difference in the absorption spectra of HAD and HOAD is due to the presence of a third OH group at position 4 having the ability to form another ring.…”

pH-dependent redox mechanism and evaluation of kinetic and thermodynamic parameters of a novel anthraquinone

“…The signals at 232 and 252 nm are assigned to p-p* transitions of the benzenoid system while that at 287 nm is assigned to p-p* transition of the quinonoid system. 50,51 The splitting of the benzenoid band may be due to the existence of structures or conjugation breakage. The broad band (at 425-550 nm) lacking in the absorption spectrum of simple anthraquinone 52 is present in the spectrum of HCAQ.…”

“…The broad band (at 425-550 nm) lacking in the absorption spectrum of simple anthraquinone 52 is present in the spectrum of HCAQ. As the hydroxyl group is electron donating and gives an absorption band in the visible region as a result of a charge transfer (CT) mechanism, 51,53 so the spectral band displacements are related to the increase in length of the chromophore by additional ring formation due to intermolecular hydrogen bonding. 53,54 The absorption spectra of HCAQ in media of different pH are shown in Fig.…”