Guest–host systems containing anthraquinone dyes with multiple visible transitions giving positive and negative dichroic order parameters: an assessment of principal molecular axes and computational methods

Abstract

(2017) Guest-host systems containing anthraquinone dyes with multiple visible transitions giving positive and negative dichroic order parameters: an assessment of principal molecular axes and computational methods. Liquid Crystals, Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.)Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tlct20 Three 1,4-disubstituted anthraquinone dyes with bis(4-n-butylphenyl) substituents connected via amine or amide linking groups have been studied as guest molecules dissolved in the nematic host E7. UV-visible absorption spectroscopy has shown each of the dyes to exhibit multiple absorption bands in the visible region, and dichroic order parameters obtained from polarised spectra of aligned guest-host samples were shown to differ significantly between the bands for each dye, and between the dyes. Time-dependent density functional theory calculations indicated that each dye exhibits several transitions, giving transition dipole moment vectors with a range of orientations, and fully atomistic molecular dynamics simulations of the guest-host mixtures showed differences in the calculated molecular alignments of the dyes. Combining the results from these two sets of calculations enabled a comparison of molecular alignment models based on the moments of inertia and the surface tensors of the dyes. The match between calculated and experimental values was improved significantly when using the surface tensor rather than the moment of inertia model, indicating that the shapes of the molecular surfaces of these dyes are crucial to their alignment. A novel method of calculating polarised UV-visible absorption spectra of dyes in liquid crystal hosts is also presented.

Novel Series of Diaminoanthraquinone-Based π-Extendable Building Blocks with Tunable Optoelectronic Properties

“…The Sonogashira coupling was achieved with 2 , iodobenzene, and Pd(PPh 3 ) 2 Cl 2 in triethylamine/THF (1/1) as a solvent under mild temperature conditions. Thus, the undisturbed −NH 2 groups in n -TIPS-DAAQ , 2 , and 2-Ph-DAAQ leave open further options to extend the core through either base or Cu(II) catalyzed C–N bond formation 13 under mild conditions. We anticipate that Scheme 2 will be suitable for all n -TIPS-DAAQ s. Therefore, this current design of π-extendable 1-5-DAAQ- based building blocks could be flexible from both −C≡C– and −NH 2 sites for making longer π-conjugated systems, which was never achieved so far, until this report.…”

“…So, the lingering question of regioselectivity for such bromination in the presence of two functional groups, i.e., >C�O and −NH 2 in 1,5-DAAQ, was unanswered. However, we could isolate the n-TIPS-DAAQs on a silica column using hexane/dichloromethane as an eluent and characterize them by 1 H, 13 C NMR, and HRMS. Previously, we reported 2-TIPS-DAAQ with unambiguous structural characterization.…”

“…The solubility of 2 was comparatively better than the perbrominated mixture 1a−1c. Despite that, 13 amine/THF (1/1) as a solvent under mild temperature conditions. Thus, the undisturbed −NH 2 groups in n-TIPS-DAAQ, 2, and 2-Ph-DAAQ leave open further options to extend the core through either base or Cu(II) catalyzed C−N bond formation 13 under mild conditions.…”

Comparison of semi‐empirical and density functional approaches for the colour and constitution of anthraquinone dyes using X‐ray structure

“…Various numbers of AQ chromophore have been investigated to achieve satisfactory characteristics in terms of functional applications and specialised uses. 19,20 Common AQ dyes, such as those used in the textile industry, are not suitable for displays. A quite surprising and more recent development is the discovery that suitably modified AQs can be used as a dichroic dye in liquid crystal displays, even although they can hardly be described as thin rod-like molecules.…”

“…AQ dyes showing brilliant colours with higher fastness properties are in great demand because of their suitability for various end uses. Various numbers of AQ chromophore have been investigated to achieve satisfactory characteristics in terms of functional applications and specialised uses 19,20 . Common AQ dyes, such as those used in the textile industry, are not suitable for displays.…”