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Physical Properties of Individual Groundwater Chemicals
Published in John H. Montgomery, Thomas Roy Crompton, Environmental Chemicals Desk Reference, 2017
John H. Montgomery, Thomas Roy Crompton
Uses: A mixture of cis and trans isomers is used as a solvent for fats, phenols, camphor; ingredient in perfumes; low-temperature solvent for sensitive substances such as caffeine; refrigerant; organic synthesis.
Effects of photoswitching in complex partially ordered systems
Published in Liquid Crystals Reviews, 2020
Photoswitchable soft organic materials are of great interest for both fundamental research and their numerous applications in soft nanorobotics, photoelectronic devices, molecular photonic switchers, holographic data storage, and sensors [1–4]. Incorporating chromophores into the chemical structure of the liquid crystals – anisotropic soft materials with orientational order – results in photocontrollable mesophase properties. Such photochromic LCs are often azobenzene derivatives (diazenes), well known as dyes [5,6]. Since their discovery in 1858 by Peter Grieß [7,8], diazonium salts have been studied extensively. As a result of their extended conjugated π-system the azo chromophore interconverts between the thermally stable trans isomer and the metastable cis isomer upon absorption of a photon. The photoinduced and the thermally driven isomerisations are well-separated in time. The trans-cis isomerisation results in a change of the molecular shape and affects the intermolecular interactions and packing. Furthermore, azobenzenes exhibit remarkable photostability even under prolonged irradiation. Moreover, chemical modification of the molecular structure allows the design of chromophores with an extensive chromatic range [9].
Molecular design of supramolecular polymers with chelated units and their application as functional materials
Published in Journal of Coordination Chemistry, 2018
Igor E. Uflyand, Gulzhian I. Dzhardimalieva
In particular, thermo-responsive MSPs that use a thermally induced interconversion between cis- and trans-isomers on the cyclam block are of interest [269]. In the cis-isomer, the substituents are on the same side of the cyclam plane, whereas in the trans-isomeric subunits are located above and below the cyclam plane. In the MSPs formed by the bis-tpy-cyclam-ligand and Ni(II) ions, the temperature-initiated cis-trans transitions on the cyclam block lead to a macroscopic phase sol–gel transition. Initially, the kinetically preferred cis-isomers, which form coil-like aggregates, are present in the solution. During heating, the cis-form passes into the trans-form, and the coils expand to the rod-coils, which leads to aggregates consisting of rigid and flexible segments and to gelling (Figure 54).