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Abstract
We studied supramolecular chirality induced by circularly polarized light. Photoresponsive azopolymers form a helical intermolecular network. Furthermore, studies on photochemical materials using optical vortex light will also attract attention in the future. In contrast to circularly polarized light carrying spin angular momentum, an optical vortex with a spiral wave front and carrying orbital angular momentum may impart torque upon irradiated materials. In this review, we summarize a few examples, and then theoretically and computationally deduce the differences in spin angular momentum and orbital angular momentum depending on molecular orientation not on, but in, polymer films. UV-vis absorption and circular dichroism (CD) spectra are consequences of electric dipole transition and magnetic dipole transition, respectively. However, the basic effect of vortex light is postulated to originate from quadrupole transition. Therefore, we explored the simulated CD spectra of azo dyes with the aid of conventional density functional theory (DFT) calculations and preliminary theoretical discussions of the transition of CD. Either linearly or circularly polarized UV light causes the trans–cis photoisomerization of azo dyes, leading to anisotropic and/or helically organized methyl orange, respectively, which may be detectable by CD spectroscopy after some technical treatments. Our preliminary theoretical results may be useful for future experiments on the irradiation of UV light under vortex.
Highlights
Metal complexes undertake electric dipole transition when excited by light absorption [12], and azobenzene derivatives absorb the specific orientation of the light irradiated against molecular axes to carry out trans–cis photoisomerization [13]
Symmetry 2021, 13, 1103 molecular orientation due to the trans–cis isomerization of an azobenzene derivative moiety, namely, linearly or circularly polarized light-induced optical anisotropy or helical alignment, respectively, attributed to molecular reorientation caused by the Weigert effect,effect has been extensively studied
Metal complexes undertake electric dipole transition when excited by light absorption [12], and azobenzene derivatives absorb the specific orientation of the light irradiated against molecular axes to carry out trans–cis photoisomerization censee MDPI, Basel, Switzerland
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. As well as azobenzene moieties dispersed in a polymer matrix, increase optical anisotropy after the irradiation of linearly or circularly polarized ultraviolet (UV) light, a process that can be observed using various spectroscopic measurements. Symmetry 2021, 13, 1103 molecular orientation due to the trans–cis isomerization of an azobenzene derivative moiety, namely, linearly or circularly polarized light-induced optical anisotropy or helical alignment, respectively, attributed to molecular reorientation caused by the Weigert effect,effect has been extensively studied [1,2]photoisomerization (Figure 1). The referenced papers using cast films less than 0.05 mm thick at room temperature
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