The effects of cyclic terminal groups on the electronic absorption spectra of di- and tri-phenylmethane dyes

Abstract

The spectral shifts of the first absorption bands brought about by cyclic terminal groups in analogues of Michler's Hydrol Blue, Malachite Green, and Crystal Violet are determined mainly by inductive effects.Dye cations containing terminal pyrrolidino substituents are significantly more stable than those possessing piperidino groups as a result of differences in basicity brought about by a change in size of the saturated heterocyclic ring.

Hexaarylbutadiene: A Versatile Scaffold with Tunable Redox Properties towards Organic Near‐Infrared Electrochromic Material

“…Comparison of UV/Vis/NIR spectrum shows that the spectra of dications 3 a 2+ – 3 c 2+ are quite similar to each other irrespective to the difference in the amino groups on the aniline moiety, and thus only marginal shift of λ max was observed (Figure a and Table ). This is in accord with the previous observation that the absorption band is almost unchanged when the diethylamino, pyrrolidino, and morpholino groups are replaced for the dimethylamino groups in MHB + dye . Thus, upon electrochemical oxidation of dienes with pyrrolidino ( 3 b ) and morpholino ( 3 c ) groups, electrochromism with drastic change of NIR absorption was demonstrated in each case with an isosbestic point (Figures and S3).…”

“…This is in accord with the previous observation that the absorption band is almost unchanged when the diethylamino, pyrrolidino, and morpholino groups are replaced for the dimethylamino groups in MHB + dye. [21] Thus, upon electrochemical oxidation of dienes with pyrrolidino (3 b) and morpholino (3 c) groups, electrochromism with drastic change of NIR absorption was demonstrated in each case with an isosbestic point ( Figures 3 and S3). Due to the similarity of the absorption in 3 b 2 + and 3 c 2 + , chromic behavior is nearly identical although there is a big difference between their redox potential (ΔE = 0.25 V), as in the electrochromism of tetraarylanthraquinodimethanes.…”

“…Based on these results, we envisaged that the 1,1,2,3,4,4‐hexaarylbutadiene skeleton can be a versatile scaffold in constructing less well‐explored class of EM exhibiting NIR spectral changes. Based on the density functional theory (DFT) calculations and previous studies, we have designed here a new series of compounds ( 3 a – 3 c / 3 a 2+ – 3 c 2+ ) with two 4‐bromo‐2,6‐difluorophenyl groups at 2,3‐positions on the butadiene (Scheme c), with the expectation that redox potentials of these butadienes could be controlled by a change in electron‐donating aniline units while absorptions of the corresponding dications would be nearly the same. Three kinds of aniline units with different donating ability have been examined, which are attached at 1,1,4,4‐positions on the butadiene.…”

The effects of cyclic terminal groups in di- and tri-arylmethane dyes. Part 2.1 Steric and electronic effects in derivatives of Victoria Blue

“…This finding confirms the unequal participation of the three dimethylamino groups in the resonance system since CV itself is not protonated under the same conditions. 1 In addition, the spectrum of the dication of 2a is very similar to that of the symmetrical 1-naphthyl derivative of Malachite Green 1 (R 1 = H, R 2 = NMe 2 ). It follows that the dication derived from 2a arises from protonation of the aminonaphthyl group and that it is the 4-dimethylamino-1-naphthyl ring which is the less-conjugated moiety.…”

Solid-state Structures of N-Substituted Michler’s Ketones and Their Relation to Solvatochromism

“…The resulting solid was filtered, washed thoroughly with 50 mL of water, dried under vacuum, and recrystallized from ethyl acetate to afford 22.62 g (65%) of MK(pip) 2 ( 2b ) as a pale yellow solid crystals with m.p. 152 °C (ref 8. 140−142 °C from acetone).…”