Photoswitching of Dihydroazulene Derivatives in Liquid‐Crystalline Host Systems

Abstract

Photoswitches and dyes in the liquid crystalline nematic phase have the potential for use within a wide range of applications. A high order parameter is desirable in order to maximize the change in properties induced by an external stimulus. A set of photochromic and non-photochromic dyes were investigated for these applications. It was found that a bent-shaped 7-substituted dihydroazulene (DHA) photoswitch exhibited liquid crystalline properties. Further investigation demonstrated that this material actually underwent two distinctive reaction pathways upon heating to a deactivated form via a 1,5-sigmatropic shift and to a linear 6-substituted DHA. In addition, elimination of hydrogen cyanide from these photoactive DHAs gave both bent and linear azulene dyes. In a nematic host, which has no absorbance around 350 nm, it was found that only the linearly shaped DHA derivative possessed nematic properties; however, both 6-and 7-substituted DHAs were found to have high order parameters. In the nematic host, ring opening of either DHA to the corresponding vinylheptafulvene (VHF) resulted in a decrease in dichroic order parameter and an unusually fast back reaction to a mixture of both DHAs. Likewise, only the linearly shaped azulene derivative showed mesomorphic properties. In the same nematic host, high order parameters were also observed for these dyes.

N-Methylpyrrolidinium hydrogen tartrate (NMPHT): an above-room-temperature order–disorder molecular switchable dielectric material

“…[1][2][3][4][5][6][7][8][9][10] The architecture and design of such stimuli-responsive structural phase-transition materials (SPTMs) are not only imperative for nding multifunctional materials with novel properties but also very valuable for studying the structure-property relationships. [11][12][13][14][15] Such materials are capable of switching between two or more states, which can thus be employed for multiple purposes 16 including rewritable data storage, [17][18][19][20] memory devices, [21][22][23] switchable dielectric, magnetic and optical functionalities.…”

Second order nonlinear optical properties of poled films containing azobenzenes tailored with azulen-1-yl-pyridine

“…At the same time, employing azulene derivatives as precursors in designing electronic and optical materials, has attracted an increased attention owing to their unique fluorescent and redox properties [ 17 , 18 ]. So far, this blue-colored hydrocarbon proved to be an attractive building block for developing molecular switches [ 19 , 20 ], liquid crystals [ 21 , 22 ], supramolecular assemblies [ 23 , 24 ], organic transistors [ 25 ], redox-active covalent organic framework [ 26 ], and high conductance materials [ 27 ]. A relevant characteristic of azulene in the construction of push-pull compounds is its dipole moment of about 1.08 D [ 28 ], arising from the electron drift from the seven-membered ring to its five-membered ring, leading to an intrinsic dipolar structure [ 29 ].…”