Molecular dynamics simulations and quantum chemistry calculations have been combined to describe the dark adaptation in bacteriorhodopsin (bR). The process involves the reversible thermally activated transformation of retinal from an all-trans to a 13-cis,15-syn configuration. The potential surface governing the thermal isomerization of retinal around two (13-14, 15-N) double bonds has been det...

The photo-isomerization of o-acetylbenzaldehyde (oABA) in acetonitrile was studied by femto- and nanosecond transient absorption spectroscopy. Spectroscopic signatures are assigned with the aid of TD-DFT, TD-CAM-DFT and DFT-MRCI computations. The isomerization yields a lactone, 3-methylphthalide (3MP), with a quantum yield of 0.3 (30%). As evidenced by femtosecond stimulated Raman spectroscopy ...

The isomerization properties of an azocarbazole macrocycle in solution were investigated utilizing NMR spectroscopy with in situ irradiation in combination with DFT calculations. It was demonstrated that the position of azo units in a rigid macrocyclic system influences the photoisomerization pathway even if the initial all-E isomer is highly symmetric. Furthermore, the effect of ring strain on...

Generally, rotational isomerization about the carbon-carbon single bond in simple ethane derivatives in room-temperature solution under thermal equilibrium conditions has been too fast to measure. We achieved this goal using two-dimensional infrared vibrational echo spectroscopy to observe isomerization between the gauche and trans conformations of an ethane derivative, 1-fluoro-2-isocyanato-et...

We report the characterization and photochemistry of a simple ruthenium coordination complex containing only picolinate (pic) and dmso, which exhibits a large isomerization quantum yield (Phi(SS-->OO) = 0.50) in various solvents. The picolinate ligands of [Ru(pic)(2)(dmso)(2)] are in a cis arrangement so that the carboxylate oxygen of one pic ligand (O1) is trans to the pyridine of the second p...

Allyl glycidyl ether, polymerized from potassium alkoxide/naphthalenide initiators under both neat and solution conditions was shown to be a highly-controlled process. In both cases, molar masses (10-100 kg/mol) were determined by the reaction stoichiometry, and low polydispersity indices (1.05-1.33) could be obtained with a full understanding of the dominant side reaction, isomerization of the...

Transformation of 3-propargylmercapto-6 methyl-1, 2,4-triazin- 5 (2H)- one (1; R=CH3) to 3,6- dimethyl-7H- thiazolo [3,2-b] [1, 2, 4] triazin -7- one (2) is performed under basic condition. The formation of (2) may be mainly due to the high reactivity of acetylenes towards nucleophiles and isomerization of the intermediate. 

Phase-change azobenzene derivatives can store and release heat upon isomerization. The amount rate of output are affected by the crystallization isomerization, which in turn governed molecular structure interactions. Thus, optimizing is a promising method to control at different temperatures. Herein, we prepared three asymmetric alkoxy-substituted molecules (s-Azo) with similar weights but subs...

We recently described a remarkable acid-catalyzed isomerization of bicyclic alkenes Ia and Ib to the betweenanenes IIa and IIb. ’ This finding suggested that certain larger ring betweenanenes might possess unusual stability relative to double bond isomers and might thus be derivable from readily available bicyclic compounds via equilibrating processes. In this report we describe several attempt...

Rotation about the C-N bond in amides can be catalyzed by Bronsted and Lewis acids, as well as nucleophiles and bases. Catalysis of amide isomerization occurs in biological systems via "rotamase" enzymes; however, the mechanisms by which these proteins operate are not completely understood. We outline investigations that provide experimental support for mechanisms believed to be feasible for th...