Photochromic Switches Incorporated in Bridging Ligands: A New Tool to Modulate Energy‐Transfer Processes

Belser, Peter; Cola, Luisa De; Hartl, František; Adamo, Vincenzo; Bozic, Biljana; Chriqui, Y.; Iyer, Vijay Mahadevan; Jukes, Ron T. F.; Kühni, Joël; Querol, Manel; Roma, Silvia; Salluce, Nunzio

doi:10.1002/adfm.200500247

Cited by 122 publications

(92 citation statements)

References 80 publications

(42 reference statements)

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“…[42][43][46][47][48][49] This undesired situation may arise either through direct excitation of the isomerizable bridge or via energy transfer from the donor (or 85 the acceptor) to the bridge. 32,[42][43][46][47][48][49] Since IVCT bands usually occur in the NIR spectral range while shorter wavelengths are required for bridge photoisomerization, this problem is much less prone to occur in mixed valence compounds. While there is considerable room for improvement of the 90 mixed valence properties of photoswitchable systems, it seems clear that much future work will be geared at direct measurement of the conductance of photoisomerizable molecules.…”

Section: Discussionmentioning

confidence: 99%

Photoswitchable mixed valence

Wenger

2012

Chem. Soc. Rev.

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For a molecular electronics technology to be fully serviceable, switching functions will be indispensable. 5 Specifically, it will be desirable to control the conductivity of a given molecule using an external stimulus. Photoswitchable mixed valence systems are comprised of a reversibly photoisomerizable bridging unit connecting two redox-active moieties, and as such represent some of the most simple chemical systems in which switching of charge delocalization can be explored. As photoisomerizable units, dithienylethenes have received much attention in the context of photoswitchable mixed valence, but 10 there are also more exotic examples such as norbornadiene-and dimethyldihydropyrene-based switchable systems. As redox-active units responsible for the mixed valence phenomenon, both metal-containing as well as purely organic moieties have been employed. Typical investigations in this area involve the comparison of cyclic voltammograms and (near-infrared) optical absorption spectra of the two isomeric forms of a given system. The magnitude of the comproportionation constant and evaluation of 15 intervalence absorption bands using appropriate theoretical models yield information regarding the extent of charge delocalization in the two isomeric forms. In several of the compounds investigated so far, the light stimulus induces a substantial increase of charge delocalization, or in the terminology commonly used in mixed valence chemistry, a changeover from class I to class II or even class III behavior.

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Section: Discussionmentioning

confidence: 99%

Photoswitchable mixed valence

Wenger

2012

Chem. Soc. Rev.

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“…The diarylethene class of photochromic switches, in contrast to spiropyrans, exists in two thermally stable forms: the so-called open, colorless form and the closed, colored form ( Figure 5). Despite extensive studies on the photochemistry of the dithienylcyclopentene class of photoswitchable compounds (21), only relatively recently has the electrochromic and general electrochemical behavior of this important class of molecular switches received a similar level of attention (22)(23)(24)(25)(26)(27).…”

Section: Figurementioning

confidence: 99%

Light Switching of Molecules on Surfaces

Browne

Feringa

2009

Annu. Rev. Phys. Chem.

271

254

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Smart surfaces, surfaces that respond to an external stimulus in a defined manner, hold considerable potential as components in molecular-based devices, not least as discrete switching elements. Many stimuli can be used to switch surfaces between different states, including redox, light, pH, and ion triggers. The present review focuses on molecular switching through the electronic excitation of molecules on surfaces with light. In developing light-responsive surfaces, investigators face several challenges, not only in achieving high photostationary states and fully reversible switching, but also in dealing with fatigue resistance and the effect of immobilization itself on molecular properties. The immobilization of light-responsive molecules requires the design and synthesis of functional molecular components both to achieve light switching and to anchor the molecular entity onto a surface. This review discusses several demonstrative examples of photoswitchable molecular systems in which the photochemistry has been explored in the immobilized state under ambient conditions and especially on electroactive surfaces, including self-assembled monolayers, bilayers, and polymer films.

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“…Spiropyran, a promising photochromic compound, undergoes reversible structural transformations in response to external inputs, such as light. [4,6,7] This special property of the spiropyran molecules was used to construct complex, optically controlled integrated logic gates and molecular switches composed of dyad or triad molecules with spiropyran as one of their units. [8][9][10] In this dyad or triad method, the modulation of various photonic or optoelectronic processes was usually realized by fluorescence quenching through energy transfer.…”

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confidence: 99%

Photoreversible Fluorescence Modulation of a Rhodamine Dye by Supramolecular Complexation with Photosensitive Cyclodextrin

Wu¹,

Luo²,

Zeng³

et al. 2007

Angew Chem Int Ed

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Materials with properties that can be optically modulated are of high interest in many scientific areas, including biotechnology and optics.[1] Photosensitive-in particular photochromic-compounds can be used to achieve this purpose, as they can be converted reversibly by light between two states with different spectroscopic properties. [2][3][4][5] This attribute can then be used to modulate or switch various functions at the molecular or supramolecular level by using light as a trigger. Spiropyran, a promising photochromic compound, undergoes reversible structural transformations in response to external inputs, such as light. [4,6,7] This special property of the spiropyran molecules was used to construct complex, optically controlled integrated logic gates and molecular switches composed of dyad or triad molecules with spiropyran as one of their units. [8][9][10] In this dyad or triad method, the modulation of various photonic or optoelectronic processes was usually realized by fluorescence quenching through energy transfer. In this approach to a light-controlled molecular switch or logic gate, several issues still need to be addressed: Firstly, the specific fluorophore must be covalently linked to the spiropyran molecule (or linked to it through a spacer) to form the dyad or the triad; hence, in this approach, only one dyad or triad can be used for a specific application. Secondly, selfquenching is still observed as a result of the self-aggregation of the fluorophore moieties. Thirdly, the dyads or triads are usually hydrophobic, which limits their applications in hydrophilic environments; in addition, they lack the necessary biocompatibility for applications in the fields of biotechnology.It is well known that cyclodextrin (CD) can form supramolecular inclusion complexes with small-molecule chromophore compounds that fit into its 5-8 cavity; [11][12][13] in this way, the fluorescence intensity, biocompatibility, and photostability of the guest chromophore compounds can be enhanced. [14,15] Herein, we synthesized photosensitive cyclodextrin (CDSP) by covalently attaching spiropyran moieties onto b-CD. Rhodamine B [16][17][18] (RhB) was used as a model fluorophore to form a supramolecular complex with the CDSP, and photoreversible fluorescence modulation was thus realized. This strategy is easily achievable, and the guest rhodamine molecules can be readily replaced by other chromophore compounds. In addition, the self-quenching of RhB can be decreased by supramolecular complexation. The strategy could provide a facile method for reversible fluorescence modulation, controlled by light, for a wide range of chromophores, which is essential in applications such as reversible bioimaging. At the same time, the chromophore complexes will have the necessary biocompatibility and hydrophilicity for applications in the field of biotechnology because of the presence of the oligosaccharide cyclodextrin.Photosensitive b-cyclodextrin was synthesized and based on mass spectrometry (MS), high-performance liquid chromatography (H...

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Photochromic Switches Incorporated in Bridging Ligands: A New Tool to Modulate Energy‐Transfer Processes

Cited by 122 publications

References 80 publications

Photoswitchable mixed valence

Photoswitchable mixed valence

Light Switching of Molecules on Surfaces

Photoreversible Fluorescence Modulation of a Rhodamine Dye by Supramolecular Complexation with Photosensitive Cyclodextrin

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