Gated Reactivity

The photoreaction of 27 was completely prohibited in cyclohexane. The addition of a very small amount of ethanol to the cyclohexane solution resulted in photochromic reactivity. In the mixed solvents of cyclohexane and ethanol, the 

The hydrogen bonds can also be broken by heating. In decalin, photocyclization did not occur below 60°C, while it was clearly observed at temperatures higher than 100°C. The molecule has both chemical- and thermal-gated reactivity. 

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Substituents on the reactive position greatly influence the photoreactivity. 2-Thienyl derivatives have been reported to work very well (03JA3404). The control of the photoreactivity by external stimuli such as pH or electric potential is important for the practical application of diarylethenes, because a controlled photoreactivity, namely a gated reactivity, can provide a nondestructive readout capability. Pyridyl group is one of the external stimuli-responsive substituents that are quaternized by alkylating reagent or protic acid. Dithienylethene derivatives 250-253 have been reported. 

Girgis, M.J. and B.C. Gates, Reactivities, Reaction Network, and Kinetics in High-Pressure Catalytic Hydroprocessing, Ind. and Eng. Chem. Res., 30,2021,1991. 

The diarylethenes 15-17 with oligothiophene aryl groups showed a thermal-gated reactivity (Eq. (6)) [19],... 

The cycloreversion quantum yield of 17b (0 = 0.00013) was much lower than that of 15b (O = 0.075). The very low cycloreversion quantum yield was found to increase steeply as much as 34-fold when the temperature was raised from 25 to 150°C. The large temperature dependence provides 17 with thermal-gated reactivity. The recorded memory in this system can be read many times with a weak laser, which does not raise the temperature of the medium. The memory can be erased with a high-intensity laser, which can raise the temperature of the medium to as high as 100-150 °C. 

Upon addition of an acid, such as trichloroacetic acid, the absorption maximum showed the hypsochromic shift and the cycloreversion quantum yield increased as much as 10 -fold. Protonation to the dimethylamino group decreased the electron-donating ability of the substituent and resulted in the change in reactivity. This acid-gated reactivity is potentially applicable to nondestructive readout in a polymer memory medium. 

Guzman, J. and Gates, B.C. (2003) Structure and reactivity of a mononuclear gold-complex catalyst supported on magnesium oxide. Angewandte Chemie International Edition, 42, 690-693. 

Grigis, M.J. and Gates, B.C. (1991) Reactivities, reaction networks, and kinetics in high-pressure catalytic hydroprocessing. Ind. Eng. Chem. Res., 30, 2021. 

Secondary antibody (affinity-purified fluorescent antiglobulin conjugate reactive with the species globulin of the first step, e.g., affinity-purified rhodamine-conju-gated goat antimouse IgG (H + L chains) (Jackson ImmunoResearch, West Grove, PA) diluted in NGG-sap-PBS (25 pg/mL). This can be stored in this form frozen, harvested back from the dish, and reused the same as the first antibody solution. Minimum volume = 1 mL for each dish to be incubated. 

In order to further investigate the possibility of cycloalkyne 4b formed as a transient intermediate in the reaction of 3 with n-BuLi, specifically labeled 3 — CBr2 was synthesized and subsequently was reacted with n-BuLi. The reactive intermediate (s) thereby generated were trapped in situ by cyclohexene. Careful integration of the gated-decoupled C NMR spectrum of 5 — C obtained indicated that no scrambling of the C label had occurred in the... 

The selective renal carcinogenicity of dichloroacetylene may be due to a bioactivation mechanism that involves glutathione S-conju-gate formation, translocation to the kidneys, and subsequent renal metabolism to yield reactive electrophiles presumably responsible for carcinogenicity. ... 

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