A new and simple optical sensor for the detection of formic acid unleashed by wooden storage or display materials used in museums and responsible for accelerating glass deterioration

Organic pollutants such as formic acid , acetic acid and formaldehyde released by some materials (mainly wood) used for storage and display can play an important role on the alteration of the glass structure due to the alkali leaching process. It as been determined that formic acid when present inside storage or display cabinets is the one that affects most glass integrity , accelerating and deepening the alkali leaching from the silica matrix. As this situation can affect many museums on their glass collections , monitoring this compound would be of great importance for indoor preservation purposes. An optical sensor based on the layer-­‐by-­‐layer (LbL) electrostatic self-­‐assembly process is under development to identify indoor formic acid based on the immobilization of chemo-­‐responsive dyes in polymeric structures. The sensors are based on an optical response resulting from the reaction between immobilized dyes and the referred organic pollutant .publishersversionpublishe

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

UIDB/50006/2020 MEX/Ref. 288188The 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). The five chemical species have mutatis mutandis similar structures in the three multistates. The most dramatic difference is the extremely slow interconversion rate between flavylium cation and trans-chalcone in riccionidin A and related compounds multistates (tens of days) when compared with deoxyanthocyanins (a few days) and anthocyanins (several hours), at room temperature. The mole fraction distribution of the five species that constitute the multistate as a function of pH is also different in the three families of compounds. Some considerations regarding the chemical evolution of the three systems are given.authorsversionpublishe

The Effect of the Copigment on the pH-Dependent Reversible and Irreversible Processes

no 219201Intermolecular copigmentation of malvidin-3-O-glucoside with caffeine was studied using a holistic procedure that includes the extension to basic pH values. In moderately basic solutions (7.5 < pH < 9.5) and independently of the copigment presence, there is a pH region where degradation of the quinoidal base and anionic quinoidal bases is faster than hydration and OH-nucleophilic addition, preventing the system from reaching the equilibrium. Intermolecular copigmentation with caffeine reduces significantly the degradation rate of quinoidal bases. In a more basic medium, the equilibrium is reached and degradation occurs from the anionic chalcones. In this case, the addition of caffeine also reduces the degradation rate in the interval 10 < pH < 11.5.publishersversionpublishe

A transcriptomic approach to the metabolism of tetrapyrrolic photosensitizers in a marine annelid

Funding Information: Funding: The authors also acknowledge DPGM (the Portuguese General Directorate for Marine Policy) for funding the MARVEN project (ref. FA_05_2017_007). The Portuguese Foundation for Science and Technology (FCT) funded project WormALL (PTDC/BTA-BTA/28650/2017), which includes the contract attributed to M.D. and the fellowship attributed to A.P.R. UCIBIO and LAQV are financed by national funds from FCT, UID/Multi/04378/2020 and UID/QUI/50006/2020, respectively. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.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. Eulalia is a marine Polychaeta characterized by its bright green coloration resulting from a remarkably wide range of greenish and yellowish tetrapyrroles, some of which have promising photodynamic properties. The present study combined metabolomics based on HPLC-DAD with RNA-seq transcriptomics to investigate the molecular pathways of porphyrinoid metabolism by comparing the worm’s proboscis and epidermis, which display distinct pigmentation patterns. The results showed that pigments are endogenous and seemingly heme-derived. The worm possesses homologs in both organs for genes encoding enzymes involved in heme metabolism such as ALAD, FECH, UROS, and PPOX. However, the findings also indicate that variants of the canonical enzymes of the heme biosynthesis pathway can be species-and organ-specific. These differences between molecular networks contribute to explain not only the differential pigmentation patterns between organs, but also the worm’s variety of novel endogenous tetrapyrrolic compounds.publishersversionpublishe

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

PTDC/MAR BIO/01132014 PTDC/BTA-BTA/28650/2017 UID/Multi/04378/2020 UID/QUI/50006/2020 ref. FA_05_2017_007Porphyrins 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. Recently, we demonstrated that the Polychaeta Eulalia viridis, common in the Portuguese rocky intertidal, holds a high variety of novel greenish and yellowish porphyrinoid pigments, stored as granules in the chromocytes of several organs. On the follow-up of this study, we chemically characterized pigment extracts from the worm's skin and proboscis using HPLC and evaluated their light and dark toxicity in vivo and ex vivo using Daphnia and mussel gill tissue as models, respectively. The findings showed that the skin and proboscis have distinct patterns of hydrophilic or even amphiphilic porphyrinoids, with some substances in common. The combination of the two bioassays demonstrated that the extracts from the skin exert higher dark toxicity, whereas those from the proboscis rapidly exert light toxicity, then becoming exhausted. One particular yellow pigment that is highly abundant in the proboscis shows highly promising properties as a natural photosensitizer, revealing that porphyrinoids from marine invertebrates are important sources of these high-prized bioproducts.publishersversionpublishe

Dye-sensitized solar cells using fluorone-based ionic liquids with improved cell efficiency

POCI-01-0145-FEDER-016387. POCI-01-0145-FEDER-007265. UID/QUI/50006/2019. LISBOA-01-0145-FEDER-402-022125. SFRH/BD/135087/2017.Six trihexyltetradecylphosphonium chloride (P6,6,6,14Cl) based ionic liquids (IL) with dianionic fluorone derivatives were synthesized with total exchange of chloride from the dianionic dye: Fluorescein (a), Rose Bengal (b), Phloxine B (c), Eosin B (d), Eosin Y (e) and Erythrosin B (f). Spectroscopic characterization of these viscous salts indicated the presence of the expected 1 or 2 strong absorption bands. A total of 12 compounds, as sodium (from a to f) or as trihexyltetradecylphosphonium dianion salts (from a′ to f′), were used for sensitization of nanocrystalline TiO2. Here, we report the sensitization activity of these metal free dyes in terms of current-potential curve, open-circuit potential, fill factor, and overall solar energy conversion efficiency which have been evaluated under 100 mW cm-2 light intensity. We developed a strategy to improve the light harvesting of these conventional dyes by simple cationic exchange which was accompanied by a minimum of 30% increase in the cell photovoltaic conversion efficiency. Also, for Eosin B the binding to TiO2 apparently allows reduction of the-NO2 electron-withdrawing group to-NO22-. This provides a new interaction between the reduced nitro group and the TiO2 surface, reflecting an improvement in the overall DSSC performance reaching its maximum of 0.65% efficiency after light DSSC soaking. Factors that improve DSSC performance like aggregate inhibition, increment of the electrode's quasi-Fermi level and slight red shift in the absorption spectra of the tested anionic dyes were achieved by simple cationic exchange.authorsversionpublishe

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

Funding Information: This work was supported by the Associated Laboratory for Sustainable Chemistry, Clean Processes and Technologies LAQV through the national funds from UIDB/50006/2020 and UIDP/50006/2020 as well as the European Regional Development Fund within the Operational Programme “Science and Education for Smart Growth 2014–2020” under the Project CoE “National Center of Mechatronics and Clean Technologies” (BG05M2OP001-1.001-0008). N.B. is grateful to FCT for the contract CEECIND/00466/2017, D.S. for the doctoral grant (SFRH/BD/143369/2019), and L.C. for the research contract DL 57/2016/CP1334/CT0008. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.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. Differently from supramolecular chemistry, molecular metamorphosis is not a bottom-up approach. All events occur at the bottom. The procedures to characterize the kinetics and thermodynamics of the cycles are summarized. They are based on direct pH jumps (addition of a base to the flavylium cation) and reverse pH jumps (addition of an acid to equilibrated solutions at higher pH values). Stopped flow is an indispensable tool to characterize these systems. The following metamorphic cycles will be described to illustrate the concept: (i) introducing the flavanone in the metamorphic system and illustrating the concept of a timer at the molecular level; (ii) response of the flavylium-based metamorphosis to light inputs and the write-lock-read-unlock-erase molecular system; (iii) a one-way cycle of direct-reverse pH jumps; (iv) interconversion of the flavylium cation with 2,2′-spirobis[chromene] derivatives; (v) 6,8 A-ring substituent rearrangements.publishersversionpublishe

Exploring the impact of structural rigidification of amino-substituted bio-inspired flavylium dyes in DSSCs

Publisher Copyright: © 2023 The AuthorsSharing with anthocyanins the 2-phenyl-1-benzopyrylium structural motif, flavylium derivatives are strongly colored bio-inspired dyes that have been explored in dye-sensitized solar cells (DSSCs). Following on the fact that the most efficient flavylium-based dyes for DSSCs require amine electron-donating groups, a diethylamino group and the corresponding rigidified julolidine group were introduced in the benzopyrylium core. This structural variation was combined with another structural parameter – increased planarization of the flavylium ring system – to yield four flavylium derivatives all with a catechol anchoring group. The several pKa values of the new dyes and the UV–vis absorption data at different pH values and upon adsorption to TiO2 (corroborated by TD-DFT calculations) demonstrate a stronger delocalization of the nitrogen lone pair in the julolidine systems when compared to the diethylamino ones, reflecting the stronger electron-donating ability of the former. However, the julolidine-based dyes resulted in a decrease in all DSSC parameters, with efficiencies of 0.6% vs. 2.3% for the diethylamino devices. Discarding eventual increased self-aggregation processes of the more planar julolidine derivatives through studies with a de-aggregating agent (CDCA), and determining comparable dye loadings for all dyes, the presence of increased back-electron transfer processes for the julolidine-based compounds is advanced to explain their lower efficiencies. Rigidification of the flavylium dyes by bridging the benzopyrylium and the phenyl rings is demonstrated by higher fluorescence quantum yields and by electrochemical data and leads to a slight increase in the efficiency of the respective DSSCs. The results contribute to consolidate the potential of flavylium dyes as sensitizers for DSSCs.publishersversionpublishe

Photomodulation of ultrastable host–guest complexes in water and their application in light-controlled steroid release

The cucurbit[8]uril (CB8) synthetic receptor is shown to form high-affinity host-guest complexes with dicationic dithienylethene (DTE) photoswitches in water. ITC experiments combined with computational studies suggest that the formation of the inclusion complexes is mainly driven by a combination of hydrophobic effects, ion-dipole, hydrogen- and chalcogen-bonding interactions. The binding affinities were observed to be much higher for the DTE closed isomers, reaching values in the picomolar range (up to 1011 M−1) while the open isomers display up to 10 000-fold lower affinities, setting ideal conditions for the development of robust photoswitchable host-guest complexes. The light-responsive affinity of these photoswitches toward CB8 was explored to control the encapsulation and release of nanomolar affinity steroids via competitive guest replacement.publishersversionpublishe

A model compound for pyridinechalcone-based multistate systems. Ring opening-closure as the slowest kinetic step of the multistate

UID/QUI/50006/2019. PTDC/QEQ-QFI/1971/2014. PTDC/QUI-COL/32351/2017. PTDC/QUI-QFI/30951/2017. grant no. 219201.Anthocyanins and related flavylium derivatives exist in aqueous solution as a pH-dependent mole fraction distribution of species (a multistate system) with known biological activity. Introduction of nitrogen heterocycles in the flavylium core can lead to multistates with different constitution and increased activity. Compound 1, a diethylamino derivative of 4-pyridinechalcone, was synthesized and characterized by X-ray crystallography, showing a pH-dependent reaction network similar to anthocyanins and related compounds. The several species present at the equilibrium multistate were fully characterized by 1H NMR and 13C NMR. The thermodynamics and kinetics of the multistate were studied through pH jumps followed by 1H NMR and UV-vis absorption including stopped-flow for the faster kinetic steps. In the parent 4-pyridinechalcone compound, protonation of the pyridine nitrogen for pH 4 prevents formation of the flavylium cation. In compound 1, the first protonation takes place in the diethylamino substituent and in acidic medium, two new flavylium derivatives, a single (2 pH 4) and a double (pH 1) positively charged species, in equilibrium with protonated hemiketal, cis and trans chalcones, have been characterized. Differently from anthocyanins and related compounds, experimental evidence for an unexpected very slow (0.0003 s-1) ring opening-closure between the hemiketal and the cis-chalcone (tautomerization) was achieved.publishe