Steric effects in di- and tri-arylmethane dyes. Part 13. Electronic absorption spectra of derivatives of Crystal Violet, Malachite Green, and Michler's Hydrol Blue exhibiting simultaneous central and terminal steric distortion

Abstract

Spectral changes caused by the simultaneous crowding effects of o,m-dimethyl groups in Crystal Violet, Malachite Green, and Michler's Hydrol Blue are described and discussed in terms of molecular orbital theory. 2.3-Dimethyl derivatives of these dyes generally absorb at shorter wavelengths than their 2.5-dimethyl isomers owing to the increased spatial demands of the buttressed pair of substituents. Electronic symmetry is retained in derivatives of Crystal Violet but structurally unsymmetrical derivatives of Michler's Hydrol Blue and Malachite Green show red and blue deviations respectively. Diminished conjugation of terminal dimethylamino-groups with the central carbon atom leads to ready protonation of the crowded groups and, in certain cases, to incomplete conversion of dye base into dye in acid solution.

4-Ferrocenylphenyl-Substituted Tritylium Dyes with Open and Interlinked C+Ar2Entities: Redox Behavior, Electrochromism, and a Quantitative Study of the Dimerization of Their Neutral Radicals

“…This band, marked in green in Figure 4, constitutes the most intense transition in complexes 1 + and 3 and Scheme 4). 24,50,62,63 The y band may be further split into two (1 + , 6 + ) or even three (2 + ) separate transitions from lower-lying, occupied 4-ferrocenylphenyl-based donor orbitals, which differ with respect to the contributions of the ferrocenyl entity and the phenylene spacer to the corresponding excitation.…”

“…Electron paramagnetic resonance (EPR) studies were performed on a MiniScope MS5000 X-band spectrometer by Magnettech GmbH using the program ESR Studio 1. 63.0. The thermostat worked with the temperature controller HO3 using liquid nitrogen as a cooling agent.…”

Electrochemical, Spectroelectrochemical, Mößbauer, and EPR Spectroscopic Studies on Ferrocenyl‐Substituted Tritylium Dyes

“…[35] Moreover,the energy difference betweent he x and y bands diminishes strongly as the donor capacities of the attached aryl substituents resemble each other more closely,t hat is, from 144 nm (5100 cm À1 )i nFcNMe 2 + + to 45 nm (2000 cm À1 )i n FcMeOMe + + and 29 nm (1440 cm À1 )i nFcOMe + + .O ut-of-plane rotationo ft he aryl rings upon introductiono fortho methyl substituents normally causes ar edshift of the absorption bands through preferential lowering of the LUMO energy, whereas electron-donating substituents have an opposite effect. [4,36] The bathochromic shifts of the Vis bands in FcMeOMe + + compared with those in FcOMe + + are in line with previousobservations that, for ortho methyl substituents, steric effects override electronic ones. [a] Half-wave potentiale stimated from Silver'se mpiricalc orrelationb etween oxidation potentials and DE Q parameters of ferrocenes.…”

Electron-Beam-Induced Color Imaging of Acid-Chromic Polymer Films

“…Bis(aminoaryl)methanol dyes such as BH undergo acid-catalyzed dehydration, resulting in conjugated ammonium cation structures, – and therefore can be used as an acid-chromic dye for color formation. PMMA film consisting of 3 wt % BH and equimolar AG3 was prepared; it is referred to in this work as BH/AG3(3/3) .…”

“…Arylsulfonic acid esters and triphenylsulfonium salts were used as the acid generator; the acid (H + ) allows the reaction to be triggered. The acid-chromic dyes employed here, rhodamine B base ( RB ) and 4,4′-bis(dimethylamino)benzhydrol ( BH ), react with the acid and thus are colored without post-treatment such as additional color-forming chemical reactions and thermal transformations. – The color imaging of these films was performed by EBDW to form 100−1000 nm line and space patterns and evaluated by optical and confocal laser microscopy.…”