Long-Range Supramolecular Assembly of a Pyrene-Derivatized Polythiophene/MWCNT Hybrid for Resilient Flexible Electrochromic Displays.

Organic electrochromic polymers hold great potential for integration into low-power flexible electrochromic displays (F-ECDs) due to their wide range of colors and simple processing. However, challenges such as inefficient charge transfer and degradation upon device integration hinder their practical applications. Herein, we report an innovative, general approach that utilizes template-induced supramolecular nanostructuring to engineer established electrochromic polymers, enhancing their performance and durability.

Correspondence on "Visible-Light-Switchable Chalcone-Flavylium Photochromic Systems in Aqueous Media".

In a recent Communication in this journal, Bandyopadhyay and co-workers proposed a rational design of chalcone photoswitches that are claimed to convert into the respective flavylium cations upon irradiation with blue, green, and red light in aqueous media. Here we argue that the reported improvements on the optical/photochemical properties of the new chalcone photoswitches are not substantiated and that the proposed design and data interpretation rely on assumptions that have yet to be validated. We also identify a series of control experiments that can be performed to verify the hypotheses and better support the conclusions presented by the authors.

Synthesis and Photovoltaic Performance of β-Amino-Substituted Porphyrin Derivatives.

New β-amino-substituted porphyrin derivatives bearing carboxy groups were synthesized and their performance as sensitizers in dye-sensitized solar cells (DSSC) was evaluated. The new compounds were obtained in good yields (63-74%) through nucleophilic aromatic substitution reactions with 3-sulfanyl- and 4-sulfanylbenzoic acids. Although the electrochemical studies indicated suitable HOMO and LUMO energy levels for use in DSSC, the devices fabricated with these compounds revealed a low power conversion efficiency (PCE) that is primarily due to the low open-circuit voltage (V) and short-circuit current density (J) values.

Comparing the Chemistry of Malvidin-3--glucoside and Malvidin-3,5--diglucoside Networks: A Holistic Approach to the Acidic and Basic Paradigms with Implications in Biological Studies.

The kinetics, thermodynamics, and degradation of malvidin mono- and diglucosides were studied following a holistic approach by extending to the basic medium. In acidic conditions, the reversible kinetics of the flavylium cation toward the equilibrium is controlled by the hydration and - isomerization steps, while in the basic medium, the OH nucleophilic addition to the anionic quinoidal bases is the slowest step. There is a pH range (transition pHs), between the acidic and basic paradigms, that includes physiological pH (7.

Phototransduction in a supramolecular cascade: a mimic for essential features of the vision process.

The tailored design of a light-triggered supramolecular cascade results in an artificial machinery that assimilates the transduction of photons into chemical communication and the final release of a neurotransmitter. This is reminiscent of key steps in the natural vision process.

Intermolecular Copigmentation of Malvidin-3--glucoside with Caffeine in Water: The Effect of the Copigment on the pH-Dependent Reversible and Irreversible Processes.

Intermolecular copigmentation of malvidin-3--glucoside with caffeine was studied using a holistic procedure that includes the extension to basic pH values. In moderately basic solutions (7.5 < pH < 9.

Modulating the thermodynamics, kinetics and photochemistry of 7-diethylamino-4'-dimethylaminoflavylium in water/ethanol, SDS and CTAB micelles.

The thermodynamics and kinetics of compound 7-diethylamino-4'-dimethylaminoflavylium were studied in water : ethanol (1 : 1) and water in the presence of SDS and CTAB micelles. The blue flavylium cation is in equilibrium with the pink protonated flavylium cation defined by p and the yellow -chalcone, defined by p. The difference between these two ps gives the pH domain of the flavylium cation, Δp = 1.

Achieving Complexity at the Bottom: Molecular Metamorphosis Generated by Anthocyanins and Related Compounds.

The concept of molecular metamorphosis is described. A molecule (flavylium cation) generates a sequence of other different molecules by means of external stimuli. The reversibility of the system allows for the flavylium cation to be recovered by other external stimuli, completing one cycle.

Light- and pH-regulated Water-soluble Pseudorotaxanes Comprising a Cucurbit[7]uril and a Flavylium-based Axle.

A linear double pyridinium-terminated thread comprising a central chalcone moiety is shown to provide two independent binding sites with similar affinity for cucurbit[7]uril (CB7) macrocycles in water as judged from NMR, UV-Visible and fluorescence spectroscopies. Association results in [2] and [3]pseudorotaxanes, which are both pH and photosensitive. Switching from the neutral chalcone to the cationic flavylium form upon irradiation at 365 nm under acidic conditions provided an enhanced CB7 association (K increases from 1.

A Transcriptomic Approach to the Metabolism of Tetrapyrrolic Photosensitizers in a Marine Annelid.

The past decade has seen growing interest in marine natural pigments for biotechnological applications. One of the most abundant classes of biological pigments is the tetrapyrroles, which are prized targets due their photodynamic properties; porphyrins are the best known examples of this group. Many animal porphyrinoids and other tetrapyrroles are produced through heme metabolic pathways, the best known of which are the bile pigments biliverdin and bilirubin.

Photoresponsive Binding Dynamics in High-Affinity Cucurbit[8]uril-Dithienylethene Host-Guest Complexes.

The use of external stimuli to control the binding kinetics in supramolecular systems is of critical importance for the development of advanced molecular machines and devices. In this work, a study focused on the kinetics of a water-soluble host-guest system based on cucurbit[8]uril and two dithienylethene (DTE) photoswitches is reported. It is shown that for the DTE guest comprising two anionic sulfonate side arms appended to pyridinium moieties, the formation/dissociation of the pseudorotaxane structures is slowed down by more than 100000-fold with respect to its bipyridinium analogue.

Light-Mediated Toxicity of Porphyrin-Like Pigments from a Marine Polychaeta.

Porphyrins and derivatives form one of the most abundant classes of biochromes. They result from the breakdown of heme and have crucial physiological functions. Bilins are well-known representatives of this group that, besides significant antioxidant and anti-mutagenic properties, are also photosensitizers for photodynamic therapies.

Chemical evolution of the colour systems generated by riccionidin A, 3-deoxyanthocyanidins and anthocyanins.

The kinetics and thermodynamics (in acidic solutions) of the five chemical species reversibly interconnected by external stimuli (a multistate), such as pH and light, generated by the liverworts colorant riccionidin A were investigated. The degradation products of the multistate formed after 10 days at neutral pH were identified. The behaviour of riccionidin A multistate was compared with previous results reported for the equivalent systems based on 3-deoxyanthocyanidins (found in mosses and ferns) and anthocyanins (ubiquitous in angiosperms).

A Photoelectrochemical Study of Bioinspired 2-Styryl-1-Benzopyrylium Cations on TiO Nanoparticle Layer for Application in Dye-Sensitized Solar Cells.

In the present work, five 2-styryl-1-benzopyrylium salts and their relative self-assembly processes towards TiO nanocrystalline layers were evaluated as photosensitizers in dye-sensitized solar cells (DSSCs). Integration of these 2-styryl-1-benzopyrylium salts with the semiconductor allow for the performance of highly specific functions suitable for smart applications in material science. Spectroscopic and photoelectrochemical measurements conducted on these five bio-inspired dyes, in solution and upon adsorption onto titanium dioxide films, allowed detailed discussion of the anchoring ability of the different donor groups decorating the 2-styryl-1-benzopyrylium core and have demonstrated their ability as photosensitizers.

Ground and excited state properties of furanoflavylium derivatives.

The comparison of the ground-state reactivity of anthocyanins and aurone model compounds (i.e. with and without the furano bridge) has shown that the kinetic paradigm does not depend on the bridge but only on the hydroxyl substituent pattern, independently of the presence of the bridge: (i) bell shaped kinetics for those with two hydroxyl substituents in position 4' and 7, and (ii) four distinct kinetic steps for the mono substituted compounds with a hydroxyl in position 4'.

pH-Dependent Multistate System Generated by a Synthetic Furanoflavylium Compound: An Ancestor of the Anthocyanin Multistate of Chemical Species.

The multistate of chemical species generated by 4'-hydroxy-3,2'-furanoflavylium is similar to that of anthocyanins and related compounds. This furanoflavylium multistate system was fully characterized by UV-visible and NMR spectroscopy, allowing determination of the respective equilibrium and rate constants. In contrast to the multistate generated by flavylium cations derived from anthocyanins and related compounds, the furanoflavylium multistate is characterized by much slower hydration and tautomerization (pyran ring opening-closing).

Achieving Complexity at the Bottom. 2,6-Bis(arylidene)cyclohexanones and Anthocyanins: The Same General Multistate of Species.

As in supramolecular chemistry, complexity could also be achieved through a bottom-up approach. Anthocyanins and related compounds such as the compound ()-6-(dimethylamino)-4-(4-(dimethylamino)-2-hydroxybenzylidene)-1,2,3,4-tetrahydroxanthylium chloride (), here reported, exhibit this type of complexity. The thermodynamics and kinetics of the complex multistate of species of compound were studied by conventional and stopped-flow UV-visible spectrophotometry as well as by NMR.

Photo-controlled growth of polymeric submicronsized particles.

A tripodal coumarin derivative shows complex photoreactivity, changing from intra- to intermolecular photodimerization with increasing concentration. At high concentration, the compound undergoes efficient photopolymerization, resulting in the formation of polymeric submicron-sized particles. The size of these particles can be precisely increased through photoirradiation, without affecting their polydispersity.

Incorporation of Coumarin-Based Fluorescent Monomers into Co-Oligomeric Molecules.

With the purpose of modifying organic fluorescent dyes based on the coumarin scaffold, and developing and evaluating a route to its incorporation into a polymeric backbone, a study was conducted on the co-polymerization of 3-vinylcoumarins with styrene and methyl acrylate using 2,2-azobis(isobutyronitrile) (AIBN) as the radical initiator. The structural and photophysical characterization proved the incorporation of the coumarin monomers into the polymeric chain and further showed a decrease in the fluorescence quantum yields in the co-oligomers.

Photo-controlled growth of polymeric submicron-sized particles.

A tripodal coumarin derivative shows complex photoreactivity, changing from intra- to intermolecular photodimerization with increasing concentration. At high concentration, the compound undergoes efficient photopolymerization, resulting in the formation of polymeric submicron-sized particles. The size of these particles can be precisely increased through photoirradiation, without affecting their polydispersity.

A Visible-Near-Infrared Light-Responsive Host-Guest Pair with Nanomolar Affinity in Water.

The discovery of stimuli-responsive high affinity host-guest pairs with potential applications under biologically relevant conditions is a challenging goal. This work reports a high-affinity 1:1 complex formed between cucurbit[8]uril and a water-soluble photochromic diarylethene derivative. It was found that, by confining the open isomer within the cavity of the receptor, a redshift in the absorption spectrum and an enhancement of the photocyclization quantum yield from Φ=0.

Thermodynamic Stability of Flavylium Salts as a Valuable Tool To Design the Synthesis of A-Type Proanthocyanidin Analogues.

A convenient method to synthesize A-type proanthocyanidin analogues from flavylium salts and π-nucleophiles has been developed. It was found that the thermodynamic stability of the starting flavylium salt, assessed by the measurement of the apparent acidity constant ( K'), was the key parameter to design effective one-pot reactions between flavylium salts and nucleophiles such as phloroglucinol and (+)-catechin. When flavylium salts have a p K' value of 1.

Electronic and charge transfer properties of bio-inspired flavylium ions for applications in TiO-based dye-sensitized solar cells.

We present here a complete study on four synthetic environmentally friendly flavylium salts employed as sensitizers for dye-sensitized solar cells (DSSCs). The effect of several donor groups on the molecular structure of flavylium ions was investigated by combining electrochemical, spectroscopic and computational means. The computational investigation indicated that these molecules can interact strongly with the TiO surface by a single OH group of the dihydroxybenzene moiety, and can efficiently inject electrons into the TiO following the excitation of their lowest singlet states exhibiting charge transfer (CT) character.