Efficient Negative Photochromism by the Photoinduced Migration of Photochromic Merocyanine/Spiropyran in the Solid State

Abstract

Efficient negative photochromism was achieved by the photoinduced migration of merocyanine in mesoporous silica to an organophilic clay as spiropyran. Depending on the nature of the organophilic clays (dioctadecyldimethylammonium and dioleyldimethylammonium clays), important differences in the negative photochromisms and the thermal coloration were observed; the dioleyldimethylammonium clay gave a higher yield (98%) and faster reaction (half-life t 1/2 = 2.8 h) than the dioctadecyldimethylammonium clay (94% and t 1/2 = 3.2 h) of the negative photochromism, indicating the important role of the surfactant assembly to control the molecular diffusion.

Adsorption of a Spiropyran on a Layered Clay Mineral

“…The fittings with double exponential equation suggested that the adsorption of the MC contained two first-order reactions, which were thought to be the adsorption of the MC and the protonated MC, respectively. Because the protonated MC was thermodynamically stable compared to the MC in a bentonite [14], it was expected that the high amounts of proton in H + -SWF/MC led to the formation of the protonated MC and stability of the protonated MC suppressed the diffusion of the MC (or the protonated MC) into of the nanospace, taking longer time to reach the photostationary state in H + -SWF (24 min) than in Na + -SWF (12 min). The relatively weak interaction between the MC and Na + accelerated the adsorption.…”

“…The protonated MC was expected to be occurred by the reaction with hydroxyl groups at the edges of the clay. [4,[12][13][14] The rate constants at 515 nm for Na + -SWF/MC were fitted with double-exponential equation, suggesting that the thermal coloration was composed of two reactions. Those two components were expected to be the formation rate of the MC.…”

Отрицательный Фотохромизм: Последние Достижения

“…Показано, что скорость темновой релаксации фотоиндуцированной циклической формы спиропирана в окрашенную мероциааниновую форму возрастает с увеличением размера пор наночастиц диоксида кремния [16]. С использованием спиропирана СП 21 были получены органофильные глины, проявляющие отрицательный фотохромизм [17]. Ряд исследований был направлены на синтез спиропиранов, структура которых обеспечивает проявление отрицательного фотохромизма.…”

A Two-Step Baromechanical Cycle for Repeated Activation and Deactivation of Mechanophores

“…In this computational study, we focus on a derivate of the well-known spiropyran (SP) mechanophore, which can be transformed to merocyanine (MC) by application of mechanical stretching forces , (Figure ). While the reverse reaction of MC to SP has been initiated by using light, , heat, guest molecules, and redox reactions, we suggest that our method of restoring a mechanophore to its deactivated form by applying hydrostatic pressure is generally applicable to mechanophores that experience an increase in volume upon activation. Beneficially, the interconversion of SP and MC can be tracked by changes in the visible part of the UV/vis absorption spectrum.…”