Photoswitchable

Spiropyrans and fulgides bound with biomolecules as photoswitchable biomaterials (a route to optoelectronic systems) 97ACR347. 

As just mentioned, phosphorus porphyrins have unique photochemical properties. Their photophysics is also interesting. Emitter-quencher assemblies based on porphyrin building blocks have attracted attention due to their potential to serve as models in photosynthetic research (see [90] for an example) or for the development of photoswitches that could be used for the fabrication of molecular electronic/optical devices. In this context, Maiya and coworkers constructed a P(VI) porphyrin system 59b with two switchable azobenzene groups positioned in the apical positions of the pseudo-octahedral phosphorus atom [92]. Photoswitch ability (luminescence on/off) was demonstrated as... 

Scheme 23 Photoswitch ability (luminescence on/off) of 59b as a result of the EtoZ isomerization-induced modulation...

Nonadiabatic transitions definitely play crucial roles for molecules to manifest various functions. The theory of nonadiabatic transition is very helpful not only to comprehend the mechanisms, but also to design new molecular functions and enhance their efficiencies. The photochromism that is expected to be applicable to molecular switches and memories is a good example [130]. Photoisomerization of retinal is well known to be a basic mechanism of vision. In these processes, the NT type of nonadiabatic transitions play essential roles. There must be many other similar examples. Utilization of the complete reflection phenomenon can also be another candidate, as discussed in Section V.C. In this section, the following two examples are cosidered (1) photochromism due to photoisomerization between cyclohexadiene (CHD) and hexatriene (HT) as an example of photoswitching molecular functions, and (2) hydrogen transmission through a five-membered carbon ring. 

Liquid Membrane Ion-Selective Electrodes Response Mechanisms Studied by Optical Second Harmonic Generation and Photoswitchable lonophores as a Molecular Probe... 

IV. MOLECULAR PROBE FOR ISE MEMBRANE POTENTIALS BASED ON PHOTOSWITCHABLE AZOBIS(BENZO-15-CROWN-5) lONOPHORES [17]... 

If the photoequilibrium concentrations of the cis and trans isomers of the photoswitchable ionophore in the membrane bulk and their complexation stability constants for primary cations are known, the photoinduced change in the concentration of the complex cation in the membrane bulk can be estimated. If the same amount of change is assumed to occur for the concentration of the complex cation at the very surface of the membrane, the photoinduced change in the phase boundary potential may be correlated quantitatively to the amount of the primary cation permeated to or released from the membrane side of the interface under otherwise identical conditions. In such a manner, this type of photoswitchable ionophore may serve as a molecular probe to quantitatively correlate between the photoinduced changes in the phase boundary potential and the number of the primary cations permselectively extracted into the membrane side of the interface. Highly lipophilic derivatives of azobis(benzo-15-crown-5), 1 and 2, as well as reference compound 3 were used for this purpose (see Fig. 9 for the structures) [43]. Compared to azobenzene-modified crown ethers reported earlier [39 2], more distinct structural difference between the cis... 

Fig. 19. A pyridine-functionalized porphyrin that can be photoswitched between a trivial open polymer and a cooperative closed dimer.

Kume S, Nishihara H (2007) Metal-Based Photoswitches Derived from Photoisomerization. 123 79-112... 

Vogtle et al. reported the first example of a photoswitching dendrimer [94] with six azobenzene moieties attached to a derivative of 1,3,5-trisubstituted benzene as the central core. Irradiation of the all (F)-isomer at 313 nm led to a photostationary equilibrium where most of the azobenzene units were switched to the (Z)-configuration. Conversely, irradiation of this species again at a lower energy frequency (436 nm) led to a second photostationary equilibrium where the (F)-form was dominant however, it was not proven as to how many azobenzene units isomerized after irradiation. 

Giordano L, Jovin TM, Irie M, Jares-Erijman EA (2002) Diheteroarylethenes as thermally stable photoswitchable acceptors in photochromic fluorescence resonance energy transfer (pcFRET). J Am Chem Soc 124 7481-7489... 

Hayes RT, Wasielewski MR, Gosztola D (2000) Ultrafast photoswitched charge transmission through the bridge molecule in a donor-bridge-acceptor system. J Am Chem Soc 122 5563-5567... 

Olsen S, Lamothe K, MartiAAnez TJ (2010) Protonic gating of excited-state twisting and charge localization in GFP chromophores a mechanistic hypothesis for reversible photoswitching. J Am Chem Soc 132 1192-1193... 

Chudakov DM, Verkhusha W, Staroverov DB, Souslova EA, Lukyanov S, Lukyanov KA (2004) Photoswitchable cyan fluorescent protein for protein tracking. Nat Biotechnol... 

Andresen M, Wahl MC, Stiel AC, Grater F, Schafer LV, Trowitzsch S, Weber G, Eggeling C, Gmbmuller H, Hell SW, Jakobs S (2005) Structure and mechanism of the reversible photoswitch of a fluorescent protein. Proc Natl Acad Sci USA 102 13070-13074... 

Wilmann PG, Turcic K, Battad JM, Wilce MC, Devenish RJ, Prescott M, Rossjohn J (2006) The 1.7 A crystal structure of Dronpa a photoswitchable green fluorescent protein. J Mol Biol 364 213-224... 

Bizzarri R, Serresi M, Cardarelli F, Abbruzzetti S, Campanini B, Viappiani C, Beltram F (2009) Single amino acid replacement makes Aequorea victoria fluorescent proteins reversibly photoswitchable. J Am Chem Soc 132 85-95... 

Hofmann M, Eggeling C, Jakobs S, Hell SW (2005) Breaking the diffraction barrier in fluorescence microscopy at low light intensities by using reversibly photoswitchable proteins. Proc Natl Acad Sci USA 102 17565-17569... 

Habuchi, S., Ando, R., Dedecker, P., Verheijen, W., Mizuno, H., Miyawaki, A. and Hofkens, J. (2005). Reversible single-molecule photoswitching in the GFP-like fluorescent protein Dronpa. Proc. Natl. Acad. Sci. USA 102, 9511-6. 

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