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Synthesis and photochromic properties of azobenzene-derived glycomacrolactones Chaoqi Lin,[a] Stéphane Maisonneuve,[a] Cyril Theulier,[a] and Juan Xie*[a]
摘要： Reversible photocontrol of glycosides and glycoconjugates structures is a very attractive approach to modulate, in a spatiotemporal way, the various properties and biological activities of carbohydrates. We have synthesized three new azobenzene-derived glycomacrolactones from thioglycopyranosides. The synthesized cyclic glycoazobenzenes can be reversibly photoisomerized between E and Z isomers with high fatigue resistance. 1H NMR study shows that E→Z isomerization of glycomacrocycles induces large conformational change of the macrocyclic structures, without changing sugar 4C1 chair conformation. The Z-glycoazobenzenes can be thermally converted back to the E-isomers. Interestingly, these 16 to 17-membered Z-glycomacrolactones display higher thermal stability than the reported macrocyclic azobenzenes, with the half-life varied from 37 to 72 days. The excellent photoswitching property and bi-stability of the synthesized glycoazobenenes open a new opportunity for the convergent synthesis of diastereomers of glycomacrocycles. Furthermore, chiroptical properties have been observed for both E and Z glycomacrolactones. The geometry of different isomers of macrocycles has been optimized with DFT calculations. Theoretical CD spectra obtained by TD-DFT suggest that the E and Z glycomacrocycles adopt preferentially (P) helical structure for the azobenzene moiety.
关键词： photochromism,azo compounds,carbohydrates,macrolactones,chirality
更新于2025-09-23 15:22:29
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Electrical and photoresponse characteristics of 8-(1H-indol-3-ylazo)-naphthalene-2-sulfonic acid/n-Si photodiode
摘要： In this paper, of primary interest is to synthesis 8-(1H-indol-3-ylazo)-naphthalene-2-sulfonic acid (INSA) and to evaluate the main parameters of Au/INSA/n-Si/Al diode in dark and under illumination. Different techniques are used for interpreting the proposed INSA chemical structure. The dark current-voltage measurements were achieved in the temperature range of 293?413 K. It is noticed that INSA films modify the interfacial barrier height of classical Au/n-Si junction. At low applied voltages, the I–V relation shows exponential behavior. The values ideality factor, n, and the barrier height, ?, are improved by heating. The abnormal trend of n and ? is discussed, and a homogenous barrier height of 1.45 eV is evaluated. The series resistance is also calculated using Norde’s function and it changes inversely with temperature. The space charge limited current ruled with exponential trap distribution dominates at relatively high potentials, trap concentration and carriers mobility are extracted. The reverse current of the diode has illumination intensity dependence with a good photosensitivity indicating that the device is promising for photodiode applications.
关键词： Diode parameters,Photodiodes,Conduction mechanism,Azo compounds
更新于2025-09-12 10:27:22