Abstract
Azobenzene guest molecules in the metal–organic framework structure HKUST-1 show reversible photochemical switching and, in addition, alignment phenomena. Since the host system is isotropic, the orientation of the guest molecules is induced via photo processes by polarized light. The optical properties of the thin films, analyzed by interferometry and UV/vis spectroscopy, reveal the potential of this alignment phenomenon for stable information storage.
Highlights
Azobenzene guest molecules in the metal−organic framework structure HKUST-1 show reversible photochemical switching and, in addition, alignment phenomena
One of the most successful applications of the photochromic molecule azobenzene (AB) and its derivatives is its use as a command layer for liquid crystal displays (LCDs).[1−3] Here, the molecules are located in a polymer environment and linearly polarized light is used to generate an alignment of the molecule’s long axis
One way to circumvent this limitation is by replacing the host with surface mounted metal−organic frameworks (SURMOFs)
Summary
Azobenzene guest molecules in the metal−organic framework structure HKUST-1 show reversible photochemical switching and, in addition, alignment phenomena. The photoalignment is rooted in the repeated isomerization of the molecules between the trans (t-AB) and cis (c-AB) states under irradiation which brings the molecular ensemble in a photodynamical equilibrium state.[4,5] All molecules are continuously switched back and forth until they are, by chance, oriented with their long axis perpendicular to the polarization direction of the light (Figure 1).[6]
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