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Primary hyperoxalurias (PHs) are a group of inherited alterations of the hepatic glyoxylate metabolism that result in an excess of oxalate production by the oxidation of glyoxylate by the human lactate dehydrogenase A enzyme (hLDHA). The selective liver inhibition of this enzyme is one of the therapeutic strategies followed in the treatment of this disease. Even though several efforts have been recently performed using gene silencing by the RNA interference approach, small-molecule inhibitors that selectively reach hepatocytes are preferred since they present the advantages of a lower production cost and better pharmacological properties. In that sense, the design, synthesis, and physicochemical characterization by NMR, FTIR, DLS and TEM of two nanocarriers based on chitosan conjugates (1, non-redox-sensitive; 2, redox-sensitive) have been performed to (i) achieve the selective transport of hLDHA inhibitors into hepatocytes and (ii) their disruption once they reach the hepatocytes cytosol. Polymer 2 self-assembled into micelles in water and showed high drug loadings (19.8–24.5 %) and encapsulation efficiencies (31.9–40.8%) for the hLDHA inhibitors (I-III) tested. The non-redox-sensitive micelle 1 remained stable under different glutathione (GSH) concentrations (10 μM and 10 mM), and just a residual release of the inhibitor encapsulated was observed (less than 10 %). On the other hand, micelle 2 was sufficiently stable under in vitro physiological conditions (10 μM, GSH) but it quickly disassembled under the simulated reducing conditions present inside hepatocytes (10 mM GSH), achieving a 60 % release of the hLDHA inhibitor encapsulated after 24 h, confirming the responsiveness of the developed carrier to the high levels of intracellular GSH., This research has also partially been supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (grant RTI2018-098560-B-C22) and by the Andalusian Consejería de Economía y Conocimiento (FEDER program 2014-2020: grant number 1380682). This work was partially supported by the Associate Laboratory for Green Chemistry-LAQV, which is financed by national funds from FCT/MCTES (UIDB/50006/2020).

Anthocyanins are the basis of the color of angiosperms, 3‐deoxyanthocyanins and sphagnorubin play the same role in mosses and ferns, and auronidins are responsible for the color in liverworts. In this study, the color system of cyanidin‐3‐O‐glucoside (kuromanin) as a representative compound of simpler anthocyanins was fully characterized by stopped flow. This type of anthocyanin cannot confer significant color to plants without intra‐ or intermolecular interactions, complexation with metals or supramolecular structures as in Commelina communis. The anthocyanin’s color system was compared with those of 3‐deoxyanthocyanins and riccionidin A, the aglycone of auronidins. The three systems follow the same sequence of chemical reactions, but the respective thermodynamics and kinetics are dramatically different. publishersversion published

The development of semiconductor polymers for electronic applications requires tailored synthetic strategies to obtain materials with tunable electronic properties and morphology to enhance their properties. Towards this goal, here is reported the expedient synthesis of a novel class of thiophene-based electrochromic polymers, processable in organic solvents and as nanoparticles (NPs) in water. Their characterization and application in flexible solid-state electrochromic devices (ECDs) are described. All polymers have a repeat unit made of the same linear thienyl–phenyl–thienyl–thienyl fragment. The tuning of the electro-optical properties is achieved by introducing alkyl or alkoxy substituents in thiophene and/or by the presence of either -CH-CH- or -CH2-CH2- linkers connecting the repeat units and acting as conjugation modulators. The ECDs display a bright yellow or red/magenta color in the neutral state and dark blue in the oxidized state. Redox potentials, color contrast, switching time, and stability of the devices are reported, and it is demonstrated that the use of NPs films spray-coated from water instead of cast films from chloroform significantly improves their performance. Density functional theory calculations allow to elucidate the relationship between polymer structure and electrochromic properties and shed light on electronic structure changes upon oxidation, in agreement with spectroelectrochemistry.

A new sterically encumbered symmetrically substituted 4,5-bis(diphenylphosphino)acenaphthene ligand (L) has been prepared. The ligand readily forms distorted square-planar complexes with group 10 metal ions [Ni(II), Pd(II), Pt(II)] and a dimeric tetrahedral complex with Cu(I). The X-ray structures of the ligand and of the complexes show a notably short distance between the two phosphorus atoms, well below than twice the van der Waals radius of P, due to the steric requirements of the rigid acenaphthene backbone. Moreover, in the complexes a stabilizing π–π interaction between two phenyl rings belonging to the two P atoms is present. The [LCuCl]2 complex is weakly fluorescent both in solution and in the solid state with higher quantum yield as a solid where it exhibits thermally-activated delayed fluorescence and phosphorescence. [LPdCl2] and [LCuCl]2 behave as chloride transporters across a liposomal phospholipid membrane with the Pd(II) complex displaying a very high activity.

In this chapter, the current state of knowledge regarding anthocyanin chemistry and the corresponding reversible multistate system of the chemical species is presented. Mathematical equations to account for the kinetics and thermodynamics of the multistate system of anthocyanins are presented in a simple form to allow their use by non-specialists. The calculation of all rate and equilibrium constants of malvidin-3-glucoside in diluted solutions has been carried out to illustrate the use of these expressions. The irreversible reactivity of anthocyanins in foodstuffs, particularly in wine, leading to pyranoanthocyanins of the first and second generation is discussed. The use of the relative energy level diagrams of the multistate species together with their pH-dependent mole fraction distribution is reported and their usefulness emphasized. Using the morning glory flower as an example, the expression of its blue colour is rationalized by considering the thermodynamics and kinetics of the multistate system.

The introduction of two amine substituents in 4' and 7 positions, leads to the formation of a blue flavylium cation, 7-(N,N'-diethylamino)-2-(9-julolidine)-1-benzopyrilium, which is extremely stable across a wide acidic pH range. The kinetic and thermodynamic constants of the multistate system have been calculated by studying the relaxation kinetics after equilibrium perturbation by addition of base (direct pH jumps) or acid (reverse pH jumps). Except for the cis-chalcone, which is an elusive species, the relative energy levels of the other species could be calculated and a global energy level diagram constructed. The diagram explains that the stability of the diamino compound is due to the high energy level of the hemiketal species, which is difficult to access in acidic medium.

This work was supported by the Associate Laboratory for Green Chemistry-LAQV which is financed by national funds from FCT/MCTES (UID/QUI/50006/2013; 30951/02/SAICT/2017-SAICT) and co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007265). The National NMR Facility is supported by Fundacao para a Ciencia e Tecnologia (RECI/BBB-BQB/0230/2012). We acknowledge the Laboratorio de Analises REQUIMTE for the technical support for the mass spectrometry analyses. 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. publishersversion published

A fluorescent bistable pseudorotaxane was devised and shown to display pH-gated photoresponsive ring shuttling. At pH > 7.5 shuttling does not take place after light stimulation while at pH ≈ 5 the macrocycle is quantitatively translocated.

Photochromism is the photoinduced reversible transformation between two isomers having different absorption spectra. This instant change of optical properties has attracted much attention, especially for its technological applications in optoelectronic devices, such as rewritable optical memories and switches [1]. Among various photochromic materials, diarylethenes with heterocyclic rings, as for instance (oligo)thiophenes, have proven to be thermally stable and fatigue-resistant [2]. In general, molecules confined in molecular containers behave differently from those in solution. For instance, they can display accelerated reaction kinetics, stabilized "reactive" intermediates, or enhanced catalytic properties [3]. Cucurbit[n]urils (CBn) are water-soluble macrocyclic receptors with high affinity and selectivity for guest molecules with appropriate size, shape, polarity and charge [4]. In particular, the structural and electronic properties of CBn make them excellent receptors for positively charged organic molecules, due to favorable interactions established between the carbonyl portals and cationic residues [5]. In this communication, we present a study on the influence of the supramolecular complexation of differently sized cucurbit[n]urils on the photoinduced ring-closure reaction of two symmetric dithienylethene derivatives bearing pyridinium moieties. The reaction dynamics has been followed by steady-state and time-resolved absorption and emission spectroscopy. The results have been rationalised by means of DFT and TD-DFT calculations. This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie grant agreement No 734834 INFUSION. References: [1] Photochromic Materials: Preparation, Properties and Applications (Eds.: H. Tian, J. Zhang), Wiley-VCH, Germany, 2016. [2] M. Irie, T. Fukaminato, K. Matsuda, S. Kobatake, Chem. Rev., 2014, 114, 12174. [3] P. Ballester, M. Fujita, J. Rebek Jr., Chem. Soc. Rev., 2015, 44, 392. [4] S.J. Barrow, S. Kasera, M.J. Rowland, J. Barrio, O.A. Scherman, Chem. Rev., 2015, 115, 12320. [5] N. Basilio, J. Mendoza, S. Gago, A. J. Parola, Chem. Commun., 2017, 53, 6472.

Introduction: Whether as defence against predators and parasites or as a weapon for hunting, time and natural selection provided animals with a myriad of toxins, antibiotics and other specialised chemical warfare [1]. Time and evolution thus generated a broad range of biomolecules able to interfere with almost every biological pathway, rendering redundant the costly, laborious and high-risk process of designing synthetic compounds. Not surprisingly, given the oceans’ immense biodiversity, bioprospecting the seas for new bio-reactive drugs became a corner stone of the EU ‘Biotechnology for Blue Growth’ strategy. Motivated by the first drugs derived from marine animals, such as Prialt [2], and Portugal’s vast coastline, we have been screening marine invertebrates for novel compounds of biotechnological interest, while aiming at developing the tools that enable efficient marine bioprospecting at all levels of biological organisation: from marine ecology to molecular biology. Materials and methods: Phyllodocid annelids, the muricid gastropod Nucella and their regular prey (e.g. mussels) were collected from rocky beaches at W and SW Portugal. A battery of techniques, including behaviour-directed assays, cytology, histology, plus biochemichal and molecular tools (like oligonucleotide sequencing and PCR to screen for bacteriome-specific rRNAs) have been applied to identify novel substances, locate their production and assess their properties. Results: We were able to localise special cells and glands of annelids and gastropods (Figure 1) where many novel substances are produced, stored and secreted. This includes potential toxins [3] and their accompanying enzymes. Also, we isolated novel porphyrin-like pigments (which may be important biocidals and antioxidants) and even proteinaceous fluorochromes from our phyllodocid case-study, Eulalia. Among other results, the findings suggest that the microbiome associated to this species may include novel species of symbiotic bacteria. Discussion and conclusions: Toxins have unique biotechnological value because they interfere with specific biological pathways. Findings support the choice of Eulalia and Nucella from the Portuguese coast as prime targets for bioprospecting. Still, toxins are just a few among many valuable bioproducts so far disclosed. Altogether, the results show that we are just scraping the tip of the iceberg of novel substances with pharmacological potential from marine invertebrates.

Why do certain ancient natural dyes, such as indigo, preserve their colour so well while others, like brazilein, seem to degrade much faster? And how did mauveine change the world of colour? Will modern binding media, as vinyl paints, perform as well as a medieval tempera? Will it be possible to predict their durability? Photochemistry can answer many important questions about materials’ stability, providing new tools for the conservation of treasured artworks.

The photoreaction of indigo and two other derivatives in its reduced (leuco) form was investigated by absorption and fluorescence (steady-state and time-resolved) techniques. The fluorescence quantum yield (φ(F)) dependence with the UV irradiation time was found to increase up to a value of φ(F) ≈ 0.2-0.3 (after 16 min) for indigo and φ(F) = 0.2 (at ~150 min) for its derivative 4,4'-dibutoxy-7,7'-dimethoxy-5,5'-dinitroindigo (DBMNI). With a model compound, where rotation around the central C-C bond is blocked, the φ(F) value was found constant with the UV irradiation time. Time-resolved fluorescence revealed that initially the decays are fitted with a biexponential law (with 0.12 and 2.17 ns), ending with an almost monoexponential decay (~2.17 ns). Quantum yields for the isomerization photoreaction (φ(R)) were also obtained for indigo and DBMNI with values of 0.9 and 0.007, respectively. The results are rationalized in terms of a photoisomerization (conversion) reaction occurring in the first excited singlet state of trans to cis forms of leuco indigo.

We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4'-trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear flow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a thermal relaxation process, at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelastic rheological states by their effective relaxation time τ(c) and corresponding response modulus G(c), we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylate (NaSal), and tested at different temperatures.

We recently reported on the use of caged nucleotides to attain full control of enzymatic polymerization of RNA solely by light. In the absence of light no RNA formation was possible due to the efficient caging by the coumarin moiety; after irradiation, caged ATP was released with quantitative precision and RNA polymerization was resumed. As photolabile protecting group [7-(diethylamino)coumarin-4-yl]methyl] (DEACM) was used due to its high absorbance in the visible region of the spectrum, fast deprotection kinetics and absence of radical intermediates. However, the 7-diethylamino-4-hydroxymethylcoumarin photo-product (DEACM-OH) was shown to inhibit the transcription reaction for concentrations higher than 30 μM [5]. This inhibition has been associated with poor water solubility, which is commonly dealt with via cumbersome chemical modifications of the protecting moiety. To overcome inhibition, we evaluated the use of molecular scavengers to sequester DEACM-OH formed after irradiation. Determination of association constants of coumarin with β-cyclodextrins allowed the assessment of its capability to remove free coumarin molecules from solution. The influence of β-cyclodextrin in transcription reaction was also assessed. Results show that β-cyclodextrin can be successfully used as scavenger as it increases the DEACM-OH threshold concentration for inhibition, amplifying the efficiency of light controlled in vitro transcription.

Selective interaction between Crystal Violet Lactone and Fe 3+ /Fe 2+ in methanol leads to a reversible ionochromic colour change. This interaction can be controlled electrochemically, in order to achieve reversible colour changes with high contrast between colourless and dark blue solutions. The presented system is proposed as an alternative electrochromic solution.

Electrochromic materials are characterized by their colour changes upon applied voltage. Colour can mean many things: a certain kind of light, its effect on the human eye, or the result of this effect in the mind of the viewer. Since the electrochromic materials are developed towards real life applications it is relevant to characterize them with the usual commercial colour standards. A colorimetric study of electrogenerated Prussian blue and electrogenerated polymers based on salen -type complexes of Cu(II), Ni(II) and Pd(II) deposited over transparent flexible electrodes of polyethylene terephthalate coated with indium tin oxide (PET/ITO electrodes) was carried out using the CIELAB coordinates. A cuvette with a designed adapter to allow potentiostatic control was placed on an integrating sphere installed in the sample compartment of a spectrophotometer to run the colorimetric measurements. The colour evolution in situ was measured through the transmittance of the films by potentiostatic control. Chronocoulometry/chronoabsorptometry was used to evaluate maximum coloration efficiencies for the coloration step: 184 (Pd), 161 (Cu) and 83 cm 2 /C (Ni) and for bleaching: 199 (Pd), 212 (Cu) and 173 cm 2 /C (Ni) of the Pd, Cu and Ni polymer films, respectively. The Prussian Blue/Prussian White states over the PET/ITO films were relatively reversible while the reversibility and stability of the polymers based on the metals salen -type complexes depends on the metal, Pd being the most stable.

In this paper we report the encapsulation of the compound 4′,7-dihydroxyflavylium in a water-permeable crosslinked poly(2-hydroxyethyl methacrylate) matrix. The water permeability of the polymer and its transparency allow the use of pH and light stimuli to attain different states on the network defined by the various chemical reactions (multistate/multifunctional system). Unlike in water, in the polymer the compound 4′,7-dihydroxyflavylium encapsulated exhibits a thermal barrier between the cis- and trans-chalcones, a necessary requirement to define a write–read–erase cycle.

A new family of compounds able to promote host–guest interactions with specific molecules (e.g., cyanuric and parabanic acids) and to coordinate metal ions, namely Zn(II) and Cu(II), has been synthesized and fully characterized. The new probes derive from the attachment of two methylaminopyrene units to the carbonyl precursor 2,6-bis(2-formylphenoxymethyl)pyridine. Its signalling properties result from the fluorescence emission properties, which reveal the existence of intramolecular excimer formation. The compounds have showed to be highly sensitive to the solvent and hydrogen ion concentration of the medium. Depending on these, different monomer-to-excimer fluorescence ratio is displayed by the two probes. The compound with a single pyrene unit revealed absence of excimer formation and was used as model compound. The overall results are discussed on the basis of the studied probes as potentially revealing molecular movements, off–on–off fluorescent photoinduced electron transfer (PET), host–guest interactions with specific compounds and of sensing metal ions.

Two new fluorescent macrocyclic structures bearing two naphthalene (Np) units at both ends of a cyclic polyaminic chain were investigated with potentiometric, fluorescence (steady-state and time-resolved) and laser flash photolysis techniques. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state of the polyamine chains implying the existence of a bending movement (occurring in both the ground and in the first singlet excited state), which allows the two naphthalene units to approach and interact. For comparison purposes, one bis-chromophoric compound containing a rigid chain (piperazine unit) was also investigated. Its emission spectra shows a unique band decaying single exponentially thus showing that no excimer is formed. With the two new ligands, excimer formation occurs in all situations even at very acidic pH values when the protonation of the polyamine bridges is extensive. Coexistence of ground-state dimers with dynamic excimers was established based on steady-state and time-resolved fluorescence data. The energetics of excimer formation and dissociation were determined in ethanol and water. Different methods of decay analysis (independent decay deconvolution, global analysis and excimer deconvolution with monomer) were used to extract the kinetic (rate constants for excimer formation, dissociation, and decay) and thermodynamic parameters. In ethanol and acidified ethanol:water mixtures, an additional short decay time was found to exist and assigned to a dimer, whose presence is assumed to be responsible by the decrease in activation energy for excimer formation in this solvent. The results are globally discussed in terms of the small architectural differences that can induce significant changes in the photophysical behavior of the three studied compounds.

The formation of a supercomplex between the Ru(bpy)(CN)(4)(2-) (bpy = 2,2'-bipyridine) complex and the [32]ane-N(8)H(8)(8+) macrocycle (1) has been studied in water and in acetonitrile. In acetonitrile, supercomplex formation is accompanied by (i) large hypsochromic shifts in the absorption spectrum (color changes from deep violet to yellow) and in the emission spectrum, (ii) large anodic shifts in standard oxidation (0.73 V) and reduction (0.37 V) potentials, (iii) typical shifts of (1)H-NMR signals for the macrocycle N-bound protons and the complex bipyridine protons, and (iv) a large increase in the MLCT excited-state lifetime of the complex. In water, the spectral shifts and the changes in standard potential are much less pronounced, but supercomplex formation is evidenced by (13)C-NMR (and (1)H-NMR) and by emission lifetime changes. In both solvents, supercomplex formation is complete in 1:1, 1.0 x 10(-4) M solutions, indicating very large stability constant values. A structure of the supercomplex with the macrocycle bound in a "boat" conformation to the four cyanide ligands of the complex, plausible in terms of molecular models, is consistent with all the experimental data. In water, the supercomplex further associates with added negative species containing carboxylate functions, as shown by partial reversal of the lifetime changes. When the added species is also a potential electron transfer quencher (such as, e.g., Rh(dcb)(3)(3-), dcb = 4,4'-dicarboxy-2,2'-bipyridine), however, association is not accompanied by quenching. This behavior is attributed to the structure of the supercomplex-quencher adduct, in which the macrocycle acts as an insulating spacer between the excited complex and the quencher.

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Two new components have been identified in an early sample prepared according to the original recipe of Perkin, and perhaps even by Perkin himself around 1860--a new isomer of Perkin's mauveine B (designated as mauveine B2) together with a new mauveine compound (mauveine C)--and these compounds were synthesized again using starting materials chosen to reproduce Perkin's original synthesis and isolated by HPLC-DAD, identified by (1)H NMR, MS and their spectroscopic (UV/Vis and emission) and photophysical behaviour investigated.

The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm−3 NMe4Cl H2O–MeCN (1 ∶ 1, v/v) solution at 298.1 ± 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular π-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (IExc/IM), the activation energy for the exciplex formation (Ea) and the binding energy of the exciplex (−ΔH) were determined. The crystal structure of the [ZnLBr](ClO4)·H2O compound was resolved, showing that in the solid state both intra- and inter-molecular π-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no π-stacking (full overlap of the π-electron cloud of the two chromophores – anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of π-stacking complexes or to exciplex emission in solution.

We have investigated the network of reactions observed for the photochromic 4'-hydroxy-6-nitroflavylium compound in aqueous solutions upon pH changes (including pH jump and stopped flow experiments) and light excitation. The changes observed in the NMR and UV/Vis spectra allowed identification of ten different forms in which this compound can be transformed depending on the experimental conditions. Equilibrium and kinetic constants have been determined. Compared with other members of the flavylium family, 4'-hydroxy-6-nitroflavylium is characterized by a large cis--trans isomerization barrier, and a very efficient hydration reaction. These peculiar features allow writing, reading, storing and erasing photonic information on 4'-hydroxy-6-nitroflavylium by a novel cyclic process that involves the following steps: write-lock/read/unlock/enable-erase/erase.