Dithienylethene Unit Research Articles

Position and Orientation Control of a Photo- and Electrochromic Dithienylethene Using a Tripodal Anchor on Gold Surfaces

A tripodal system for anchoring photochromic dithienylethenes on gold surfaces is reported. The self-assembled monolayers of a tripod-functionalized dithienylethene were characterized by cyclic voltammetry, surface-enhanced Raman spectroscopy (SERS), and X-ray photoelectron spectroscopy (XPS). These data are compared with solution studies, solid state Raman spectroscopy, and density functional theory (DFT) calculations. We show that the tripod-functionalized dithienylethene forms stable monolayers on gold in which all three legs of the tripod are adsorbed via the thiol units, thus providing a fixed position and orientation of the dithienylethene moiety with respect to the surface. Importantly, immobilization in this way allows for retention of both the photochemical and electrochemical functionality of the dithienylethene unit and reduces photochemical fatigue observed in solution.

Water-Soluble Polymeric Photoswitching Dyads Impart Super-Resolution Lysosome Highlighters

In this report, we integrated a photoswitchable quencher, a highly emissive yet pH sensitive fluorophore, and a water-soluble polymer with controlled hydrophilicity into a functional nanosystem. The photoswitching quencher is based on dithienylethene (DTE) unit, while the pH-sensitive emitter is naphthalimide (NI) unit and the water-soluble polymer is obtained from polymerization of N-isopropylacrylamide (NIPAM). Together, these three units create a novel super-resolution lysosome highlighter, although individually none can function as a lysotracker. Because the emitter is sensitive to pH, the resulting polymer becomes highly fluorescent in acidic lysosomes. In addition, photoswitching regulates the fluorescence on and off and thus enables super-resolution localization of fluorescent polymers with sub-40 nm spatial resolution in imaging subcellular organelles. Thus, the concept presented here, including the photoswitchable DTE-pH-sensitive NI dyad, is promising to guide the development of future-generation super-resolution imaging agents.

Synthesis and characteristics of dithienylethenes with purine and pyrimidine substituents

Five new dithienylethenes decorated with purine and pyrimidine derivatives have been conveniently synthesized via a facile one-pot process. All new compounds were characterized by 1H NMR, 13C NMR, ultraviolet–visible spectroscopy and high-resolution mass spectrometry. Their photophysical properties and photochromic behavior were investigated in detail. These compounds exhibit reversible photochromism with good photocyclization/photocycloreversion quantum yields and considerable molar extinction coefficients. The result shows that the introduction of purine and pyrimidine derivatives into the dithienylethene unit has a remarkable effect on their performance, such as photoinduced fatigue resistance, photocyclization/photocycloreversion quantum yields and molar extinction coefficient.

Photochromic and Electrochromic Properties of Ruthenium Alkynyl Complexes Based on Dithienylethene Unit

A novel binuclear ruthenium alkynyl complexes with dithienylethene unit [{(MePh-tpy)(PPh3)2RuCl}2(C≡C-DTE-C≡C)](ClO4)2 (II) has been synthesized and characterized by elemental analysis and NMR spectra. Its photochromic behaviors and redox properties have also been investigated. The results indicated that the open-ring isomers of the metal complex could be triggered, either by light or electricity, to convert to their closed forms.

Diarylethene-containing carbon-rich ruthenium organometallics: tuning of electrochromism.

The association of a dithienylethene (DTE) system with ruthenium carbon-rich systems allows reaching sophisticated and efficient light- and electro-triggered multifunctional switches R-[Ru]-C≡C-DTE-C≡C-[Ru]-R, featuring multicolor electrochromism and electrochemical cyclization at remarkably low voltage. The spin density on the DTE ligand and the energetic stabilization of the system upon oxidation could be manipulated to influence the closing event, owing to the noninnocent behavior of carbon-rich ligands in the redox processes. A combination of spectroscopic (UV-vis-NIR-IR and EPR) and electrochemical studies, with the help of quantum chemical calculations, demonstrates that one can control and get a deeper understanding of the electrochemical ring closure with a slight modification of ligands remote from the DTE unit. This electrochemical cyclization was established to occur in the second oxidized state (EEC mechanism), and the kinetic rate constant in solution was measured. Importantly, these complexes provide an unprecedented experimental means to directly probe the remarkable efficiency of electronic (spin) delocalization between two trans carbon-rich ligands through a metal atom, in full agreement with the theoretical predictions. In addition, when no cyclization occurs upon oxidation, we could achieve a redox-triggered magnetic switch.

Design, synthesis, photochromism and electrochemistry of a novel material with pendant photochromic units

In the present work, the synthesis, photochromism and electrochemistry of a novel material 1, 1-(4-[3,4-bis(2,5-dimethyl-3-thienyl)cyclopent-3-en-1-yl]phenyl)-2,5-di-2-thienyl-1H-pyrrole, with pendant dithienylethene (DTE) photochromic units are described. It should be noted that the system 1 can be reversibly and efficiently switched between open (1o) and closed (1c) states by light in both solution and in the solid poly(methyl methacrylate) matrix. It is also noteworthy that the two isomers (1o and 1c) of this novel system 1 can be smoothly polymerized on ITO by electrochemical means. Surprisingly, the DTE unit in 1 does not retain its photochemical switching properties after immobilization onto ITO. The morphology of the polymer film was investigated by AFM analysis. Furthermore, it was found that the polymer exhibited remarkable electrochromic features that can be switched from green in the neutral state to violet state under applied external potentials without disturbing the photochromic units.

Core-modified rubyrins containing dithienylethene moieties.

Two stable core-modified rubyrins bearing one and two dithienylethene (DTE) units (1 and 2) have been synthesized. With one "closed-form" DTE unit, 1 shows aromaticity associated with its conjugated circuit of 26 π-electrons. In contrast, rubyrin 2 containing one "open-form" DTE unit has nonaromatic properties.

Strategies for Designing Diarylethenes as Efficient Nonlinear Optical Switches

In this theoretical first principles study, we systematically investigate the second-order nonlinear optical (NLO) properties of a large panel of dithienylethene (DTE) derivatives in order to identify design strategies toward (i) large absolute first hyperpolarizibilities (βtot) and (ii) large contrasts between the NLO responses of the open and closed forms (βratio). Our results show that applying the traditional push–pull organic chromophore design strategy to individual diarylethenes yielded substantial βtot values (100–180 × 10–30 esu); counterintuitively, however, larger βtot responses did not necessarily correlate with larger contrasts between the closed and open forms (βratio ∼ 4). For the class of inverse-DTE, we observed both smaller NLO responses and a reversal of the usual βtotclosed > βtotopen trend. On the other hand, multiswitchable systems comprising several DTE units were shown to be capable of exhibiting both large βtot (100–500 × 10–30) esu and large βratio > 10 due to the supraadditive c...

A Dithienylethene‐Based Rewritable Hydrogelator

Dithienylethene photochromic switching units have been incorporated into a hydrogelating system based on a tripeptide motif. The resulting hybrid system provided both a photochromic response and the ability to gelate water under acidic and neutral conditions. Fluorescence spectroscopy shows that the dithienylethene units are in sufficient proximity to each other to stack in gel fibers, with the tripeptide unit determining solubility. TEM measurements provided insight into the microscopic structure of the fibers formed.

ChemInform Abstract: Photochromic Bipyridyl Metal Complexes: Photoregulation of the Nonlinear Optical and/or Luminescent Properties

AbstractReview: 67 refs.

Light‐Controlled Formation of Vesicles and Supramolecular Organogels by a Cholesterol‐Bearing Amphiphilic Molecular Switch

A new responsive material composed of an amphiphilic light-switchable dithienylethene unit functionalized with a hydrophobic cholesterol unit and a hydrophilic poly(ethylene glycol)-modified pyridinium group has been designed. This unique single-molecule system shows responsive light-switchable self-assembly in both water and organic solvents. Light-triggered reversible vesicle formation in aqueous solutions is reported. The molecule shows a different behavior in apolar aromatic solvents, in which light-controlled formation of organogel fibers is observed. The light-triggered aggregation behavior of this molecule demonstrates that control of a supramolecular structure with light can be achieved in both aqueous and organic media and that this ability can be present in a single molecule. This opens the way toward the effective development of new strategies in soft nanotechnology for applications in controlled chemical release systems.

Orthogonally modulated molecular transport junctions for resettable electronic logic gates.

Individual molecules have been demonstrated to exhibit promising applications as functional components in the fabrication of computing nanocircuits. Based on their advantage in chemical tailorability, many molecular devices with advanced electronic functions have been developed, which can be further modulated by the introduction of external stimuli. Here, orthogonally modulated molecular transport junctions are achieved via chemically fabricated nanogaps functionalized with dithienylethene units bearing organometallic ruthenium fragments. The addressable and stepwise control of molecular isomerization can be repeatedly and reversibly completed with a judicious use of the orthogonal optical and electrochemical stimuli to reach the controllable switching of conductivity between two distinct states. These photo-/electro-cooperative nanodevices can be applied as resettable electronic logic gates for Boolean computing, such as a two-input OR and a three-input AND-OR. The proof-of-concept of such logic gates demonstrates the possibility to develop multifunctional molecular devices by rational chemical design.

Incorporating Cobalt Carbonyl Moieties onto Ethynylthiophene-Based Dithienylcyclopentene Switches. 1. Photochemistry

The synthesis and characterization of a series of dithienyl perhydro- and perfluorocyclopentene photochromic molecular switches appended with cobalt carbonyl binding 3-ethynylthiophene and phenyl-3-ethynylthiophene substituents are reported. Their photochromic properties, fatigue resistance, and thermal stability were examined to establish the effect of substituents on their performance as molecular photoswitches. The photochemical properties of the dithienylethene core were retained to the greatest extent by the inclusion of phenyl units and a hexafluorocyclopentene ring. The alkyne units of the switches were used to coordinate cobalt carbonyl moieties: i.e., Co2(CO)6 and Co2(CO)4(dppm). The cobalt carbonyl moieties were found to reduce the efficiency of cyclization and cycloreversion of the dithienylethene unit. Density functional theory was used to identify the excited states responsible for cyclization.

Photoswitchable organocatalysis in acylation of alcohol using dithienylethene-linked azoles

Three novel dithienylethenes bearing azole derivatives were synthesized and found to undergo reversible photocyclization of the dithienylethene units upon alternate irradiation with UV and visible light. Among them, the dithienylethene-linked imidazole and N-phenylimidazole exhibited a relatively high organocatalytic activity for the acylation of 2-decanol with acetic anhydride, and the catalytic activity of the dithienylethene-linked imidazole could be switched by reversible photoinduced cyclization/cycloreversion of the dithienylethene unit.

Synthesis and Characterization of Binuclear Ruthenium Vinyl Complexes with Dithienylethene Unit

A novel binuclear ruthenium vinyl complexes with dithienylethene unit II [RuCl (CO)(PMe3)3]2(μ-CH=CH-DTE-CH=CH) has been synthesized and characterized by elemental analysis and NMR spectra. Meanwhile, the crystal of II was obtained and determined by X-ray single-crystal diffraction.

Synthesis, characterization, and properties of some bisacetylide and binuclear acetylide gold(I) compounds based on the photochromic dithienylethene unit

We report the synthesis and characterization of two new bisacetylide compounds, 1,2-bis(2-ethynyl-5-methyl-3-thienyl)perfluorocyclopentene and 1-[2-methyl-5-phenyl-3-thienyl]-2-[4-methyl-2,5-bis(ethynyl)-3-thienyl]hexafluorocyclopentene together with three dinuclear acetylide gold(I) complexes LAu-CC-dithienylethene-CC-AuL in which L = PPh3 or PCy3, containing the photochromic dithienylethene unit. The photophysical properties of these new complexes are compared and contrasted with those of some previously reported dithienylethene complexes. It has been revealed that these compounds with dithienyletehene units show photochromic behavior, but their absorption spectra, cyclization/cycloreversion quantum yields, and efficiencies of the photochromic process and conversions from the open- to the closed-ring isomers in the photostationary state, are all highly dependent on the substitution sites of the bisalkynyl moiety and whether or not there is bisalkyne metalation. The photochromic process was also found to show complete reversibility by alternating irradiation with UV and visible light.

Photochromic bipyridyl metal complexes: Photoregulation of the nonlinear optical and/or luminescent properties

The combination of transition metals and ligands featuring photochromic units is receiving much attention and opens up new perspectives for the design of metal-based photoswitchable molecules. This account summarizes some of our recent works made in the area of photochromic organometallic and coordination compounds, which have been used for the photomodulation of the quadratic non-linear optical (NLO) properties, as well as of the photoregulation of the emission properties of the resulting systems. For this purpose, we have designed new chromophores combining dithienylethene (DTE)-based bipyridine ligands with different metallic fragments (ReI, FeII, RuII, IrIII, CuI, ZnII), giving rise to multi-photochromic metal complexes containing from two to six DTE units, and studied the photocontrol of both NLO and luminescence properties.

Novel Macrocycles Bearing Dithienylethene Units and Urea Functional Groups: Synthesis, Structure and Photochromic Property

AbstractTwo novel photochromic macrocycles 1 and 2 bearing dithienylethene units and urea building blocks have been synthesized, and their photochromic properties are described. Macrocycle 2 shows good photochromic properties, while the relatively smaller size of macrocycle 8b exhibits photochemically inactive properties due to the unfavourable ring conformational constraint. Moreover, the crystal structures of the urea‐protected precursor macrocyles 3a, 3b, and 8b are presented.

Multistate Photochromism in a Ruthenium Complex with Dithienylethene–Acetylide

The preparation, characterization, and photochromic properties of the ruthenium(II) vinylidene complex 1o and the ruthenium(II) acetylide complex 2o and its oxidized species 2o+ with one dithienylethene (DTE) unit are described. Complexes 1o and 2o can be mutually transformed upon the addition of base or acid due to the interconversion Ru═C═CH–DTE ⇆ Ru–C≡C–DTE. 2o and its oxidized species 2o+ can be interconverted through a reversible redox process. It is found that the ring-closing absorption band of DTE shows a progressive red shift in the order 628 nm (1c) → 641 nm (2c+) → 692 nm (2c). The photocyclization/cycloreversion quantum yields are in the order 1 (Φo→c = 0.0066, Φc→o = 0.001) < 2+ (Φo→c = 0.35, Φc→o = 0.012) < 2 (Φo→c = 0.58, Φc→o = 0.019), implying that the photochemical reactivity exhibits the order 1 < 2+ < 2, coinciding well with the progressively increased electronic density at the reactive carbon atoms. The interconversion among six states is clearly demonstrated by NMR, UV–vis–near-IR, and IR spectral, electrochemical, and computational studies.

Redox-Modulated Stepwise Photochromism in a Ruthenium Complex with Dual Dithienylethene-Acetylides

Achieving stepwise photochromism in a combined molecule to access all of the possible ring-open/closed isomers is a challenge due to facile energy transfer from ring-open dithienylethene (DTE) to an adjacent ring-closed moiety that prohibits further photocyclization. The preparation, characterization, and photochromic properties of a bis(σ-acetylide) bonded ruthenium(II) complex 2oo and its oxidized form 2oo(+) with two identical DTE-acetylides (L1o) are described. Stepwise and dual photochromic reactions are successfully achieved in both 2oo and 2oo(+), in which the ring-closing absorption band of 2oo(+) shows an obvious blue-shift relative to 2oo. It is demonstrated that stepwise photochromic reactions 2oo→2co→2cc are more facile than 2oo(+)→2co(+)→2cc(+). The lower electronic density at the reactive carbon atoms upon oxidation of Ru(II) to Ru(III) causes photocyclization to have more difficulty proceeding in oxidized species 2oo(+)/2co(+). Upon dual ring-closure, 2cc/2cc(+) exhibits significant electronic interaction between two identical ring-closed DTE units across trans-Ru(dppe)(2) spacer. The interconversion processes among six states are unambiguously demonstrated by NMR, UV-vis-NIR, and IR spectroscopic, and electrochemical and computational studies.