Combining different molecular switching functions in a single molecule is a simple strategy to develop commutable molecules featuring more than two commutation states. The present study reports on ...two molecular systems consisting of two indolino-oxazolidine (Box) moieties connected to an aromatic bridge (phenyl or bithiophene) by ethylenic junctions. Such systems, referenced as BiBox, are expected to show up multiaddressable and multiresponsive behaviors. On one hand, the oxazolidine ring opening/closure of Box moieties can be addressed by chemical stimuli, and on the other hand, the trans-to-cis isomerization of the ethylenic junctions is induced by visible light irradiation (with a thermal back conversion). NMR and UV–visible spectroscopies allowed to characterize up to nine out of the ten theoretically expected commutation states as well as to measure the kinetics of the interconversions. Also, steady state fluorescence spectroscopy measurements highlighted the strong influence of the open/closed states of the Box moieties on their emission properties.
A Simple Molecule-Based Octastate Switch Szalóki, György; Sevez, Guillaume; Berthet, Jerôme ...
Journal of the American Chemical Society,
10/2014, Letnik:
136, Številka:
39
Journal Article
Recenzirano
Dithienylethene oxazolidine hybrid system connected through an isomerizable double bond exists under eight molecular states on demand. Combinations of electrocyclization of dithienylethene, Z/E ...isomerization and acid–base oxazolidine change cause selective addressabilities. Two intricate gated photochromic performances allow the execution of an 8-step molecular switch, which renders this molecular system the most complex known up to date.
In this paper, we present a novel concept for “smarter” photolabile organic compounds combining not one but two caged functions. As proof of principle, this diarylethene-based compound possesses two ...inhibited chemical groups (OMe and OAc) and its efficient release in different solvents is reported. In low- to medium-polarity media, both MeOH and AcOH are released, with a slight preferential uncaging of AcOH except in 1,4-dioxane, where MeOH is preferentially released. In contrast, DMSO or DMF render AcOH release strongly dominating. DFT calculations of the corresponding photoreactive conformations not only afford strong support to the observed release of MeOH and AcOH but also qualitatively explain the preferential release of acid in terms of dispersive noncovalent interactions. Finally, mechanistic aspects are discussed on the bases of the spectroscopic observations and of the TD-DFT calculations.
Three addressable indolino-oxazolidine units connected through an isomerizable double bond to a substituted thiophene represent a smart example of a multiaddressable system whose reversible responses ...could be selectively activated on demand. Experimental and theoretical approaches to push forward the understanding of the system mechanism and set pathways to design optimized compounds for suitable application are here presented. NMR and UV–visible spectroscopies are used for structural and kinetic studies, while density functional theory (DFT) calculations pave the way to highlight energetic and electronic processes that are involved. Substitution and solvent effects toward the reactivity of the compounds are experimentally studied and combined with theoretical calculations. The most efficient and selective stimuli to travel between the four possible states resulting from the ring-opening of indolino2,1-boxazolidine (generally referenced as BOX) derivatives and the trans–cis isomerization of the ethylenic junction are elucidated.
An efficient synthesis of photochromic fused-naphthopyrans was developed. UV–vis or sunlight irradiation of these uncolored compounds in solution led to the formation of a single colored photoisomer ...along with an unusual and uncolored bicyclic compound formed through an intramolecular photochemical Diels–Alder reaction. Both species faded thermally in the dark to the initial form. A mechanism for this transformation is proposed based on NMR studies of irradiated solutions. The new fused-naphthopyrans have been incorporated into hybrid organic–inorganic matrices affording light-yellow materials that develop intense red colorations under UV light and return to the initial uncolored state in just a few seconds, in the dark, at room temperature. These results are useful for the development of fast switching materials used in the production of photochromic lenses.
The present study quantitatively analyses the gated photochromism and the acidity photomodulation properties of a diacid dithienylethene compound. Photoisomerisation between the open and closed ...isomers was investigated by UV/visible and 1H NMR spectroscopy. It was found that the photocyclisation quantum yield of the diacid form was remarkably high (around 90 %). Partial neutralisation of the open isomer revealed a gated photochromism as the photocyclisation quantum yield of the mono‐ and dianion were 50 and 67 %, respectively. A considerable photomodulation of the acidity was observed: the closed isomer is more acid than the open one by more than one pKa unit. This effect has been shown to be exploitable for a reversible photo‐acid generation. This is the first time that a complete quantitative investigation that allows for the determination of the main photochromic, spectral and thermodynamic parameters of a base‐sensitive photochromic diarylethene has been carried out.
Minisize, multipurpose: A pH‐sensitive photochromic diarylethene was studied according to chemical‐dynamic methodology. Quantitative data about its photochromic reactivity and acid–base properties were successfully extracted from its photocoloration and titration in acetonitrile. Although structurally extremely simple, the compound already shows a rich variety of behaviors (see scheme).
The elaboration of multichromophoric system which can undergo a reversible transformation over more than two different states can be easily performed by the covalent assembly of several identical ...switching subunits around a central node. However, the selective addressability of each of them still represents a challenging task. This study reports on the elaboration of multichromophoric systems incorporating three identical indolino-oxazolidine (BOX) moieties as multimodal addressable units. Depending of the open/closed oxazolidine ring status of each of them, these systems can be interconverted between four different states in stepwise manner by using indifferently acid addition or electrochemical stimulation. More important, we have demonstrated by using a dissymmetric triarylamine node that the classical statistical BOX opening is broken then reaching a regioselective addressability. The switching of the three identical BOX units differentiated by their π conjugated junction to the central core follows a preferential order leading to the preponderant and successive formation of only four forms over the eight theoretically and equally expected. To provide limitations and outlooks for such strategy, their switching capacities have been rationalized by DFT calculations.
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•The synthesis of new multichomophoric system exclusively based on BOX unit is proposed.•These multi-addressable systems can switch between four discrete levels exhibiting distinct optical properties.•The BOX opening of such multichromophoric system occur under stimulation in a preferential order
The behavior of 1,2-bis(R)-2-(1-methoxymethoxyethyl)-3-benzobthienyl hexafluorocyclopentene before and upon UV irradiation and during thermal evolution of the photoirradiated solution has been ...thoroughly investigated by multinuclear NMR spectroscopy. A dynamic NMR study of the initial state was performed, providing a detailed description of the perceived conformational processes in the system. Before irradiation, three open conformations are in equilibrium, whereas UV irradiation generated the two expected cyclized diastereomers. The minor diastereomer was thermally less stable than the major one, thus leading to an unexpected increase in the diastereoselectivity when raising the photoirradiation temperature. In addition, a long thermal evolution induced slow rearrangement of the stable diastereomer into byproducts that were identified.
The coexistence of 18 isomers, identified by NMR spectroscopy and gathered into six states with very different absorption properties, is observed upon irradiation with selective wavelengths of a ...triphotochromic system joining two naphthopyran entities through a dithienylethene bridge. The sequential electronic coupling of photochromic groups resulted in an absorption behavior reaching far into NIR.
A new photochromic fused benzopyran presenting a bridge between the pyran double bond and the benzenic ring was prepared. While the UV irradiation of usual benzopyrans leads to the formation of two ...colored photoisomers with very different thermal stabilities, studies by laser flash photolysis showed that the presence of this particular bridge prevents the formation of the undesirable long-lived colored TT isomer and therefore after laser irradiation the colored solution fades following a fast monoexponential decay.
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