@article{he_freeman_nakpathom_boyle_2015, title={Synthesis and X-ray analysis of a perfluoroalkyl-substituted azobenzene dye}, volume={120}, ISSN={["1873-3743"]}, DOI={10.1016/j.dyepig.2015.04.014}, abstractNote={A search for colorants capable of reducing the surface energy of synthetic fibers as well as adding color led to the synthesis and characterization of the repellency behavior of dyes such as 4-N,N-diethylamino-4′-tridecafluorohexylazobenzene. Unexpectedly high surface energy values and a low fluorine content on fiber surfaces then led to an interest in determining the crystal structure of this new dye. Accordingly, a single crystal was grown from acetone solution, and its structure was established using X-ray diffraction analysis. Interestingly, it was found that the azobenzene skeleton is appreciably nonplanar, having an N2–N1–C1–C2 torsion angle of 30.6°, despite the absence of substituents ortho to the azo bond. Further, the structure is characterized by head-to-tail molecular stacking and the N-ethyl groups in the molecule are positioned above the aminobenzene plane on the same side. It is likely that this combination of factors contribute to the observed surface properties of the target dye.}, journal={DYES AND PIGMENTS}, author={He, Liang and Freeman, Harold S. and Nakpathom, Monthon and Boyle, Paul D.}, year={2015}, month={Sep}, pages={245–250} }
 @article{lu_he_zhang_freeman_2012, title={Novel yellow azo-anthraquinone dyes for polylactide fibres: effects of alkyl chain length}, volume={128}, ISSN={["1472-3581"]}, DOI={10.1111/j.1478-4408.2011.00354.x}, abstractNote={1‐(4′‐Alkylaminosulphurylphenyl)‐3‐methyl‐5‐pyrazolonyl azo–anthraquinone dyes were prepared in four steps from 1‐aminoanthraquinone, as an approach to enhancing the exhaustion levels of disperse dyes on polylactide fibres. Their structures were confirmed from combustion analysis and mass spectrometry, infrared and proton nuclear magnetic resonance spectroscopy. Results from artificial intelligence‐based molecular modelling studies showed that increasing alkyl chain length gave an increase in LogP, molecular volume and aplanar shape. Their application to polylactide fibres led to both good per cent exhaustion values and good light fastness ratings. It was also found that the nature of the alkyl chains attached to the phenyl ring had little influence on dye colour, but clearly influenced per cent exhaustion and wash fastness.}, number={2}, journal={COLORATION TECHNOLOGY}, author={Lu, Lihua and He, Liang and Zhang, Shufen and Freeman, Harold S.}, year={2012}, month={Apr}, pages={121–126} }
 @article{he_el-shafei_freeman_boyle_2009, title={X-ray and molecular modelling studies of 4-[N-alkylamino]azobenzene dyes}, volume={82}, ISSN={["1873-3743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-64849101647&partnerID=MN8TOARS}, DOI={10.1016/j.dyepig.2009.01.013}, abstractNote={Abstract 4-[N,N-Bisalkyl]amino-2′-chloro-4′-nitroazobenzenes were recrystallized from acetone in either triclinic or monoclinic cells with the space group P-1 or P21/c. The asymmetric unit cell of dyes having at least one N-cyanoethyl group contained two molecules that were symmetrically unequivalent. The aromatic rings in the azobenzene skeleton were essentially planar with respect to the plane of the azo group, although the C6–C1–N1–N2 torsion angle was 13.2° when the N,N-dicyanoethyl group was employed. X-ray studies were used as a basis for assessing the utility of nonlocal DFT calculations in predicting the equilibrium molecular geometry and solvatochromic properties of the compounds using MM3/ZINDO-S and the COSMO Solvation Model. Although B3LYP and PBE energy functionals were comparable in predicting bond lengths, PBE was slightly better than B3LYP in predicting torsion angles. Furthermore, the dipolarity/polarizability index (π∗) was the preferred solvent parameter for predicting the effects of solvents on λmax.}, number={3}, journal={DYES AND PIGMENTS}, author={He, Liang and El-Shafei, Ahmed and Freeman, Harold S. and Boyle, Paul}, year={2009}, month={Sep}, pages={299–306} }