Photoactive Nanomaterials Inspired by Nature: LTL Zeolite Doped with Laser Dyes as Artificial Light Harvesting Systems

The herein reported work describes the development of hierarchically-organized fluorescent nanomaterials inspired by plant antenna systems. These hybrid materials are based on nanostructured zeolitic materials (LTL zeolite) doped with laser dyes, which implies a synergism between organic and inorganic moieties. The non-interconnected channeled structure and pore dimensions (7.1 angstrom) of the inorganic host are ideal to order and align the allocated fluorophores inside, inferring also high thermal and chemical stability. These artificial antennae harvest a broad range of chromatic radiation and convert it into predominant red-edge or alternatively white-light emission, just choosing the right dye combination and concentration ratio to modulate the efficiency of the ongoing energy transfer hops. A further degree of organization can be achieved by functionalizing the channel entrances of LTL zeolite with specific tailor-made (stopcock) molecules via a covalent linkage. These molecules plug the channels to avoid the leakage of the guest molecules absorbed inside, as well as connect the inner space of the zeolite with the outside thanks to energy transfer processes, making the coupling of the material with external devices easier.This work was supported by the Basque Government (IT912-16) and Spanish MICINN (MAT2014-51937-C3-3-P) projects. Leire Gartzia also thanks the Basque Goberment for a Post-doctoral grant. Yi Xiao from Dalian University (China) is kindly acknowledged for the supply and synthesis of the stopcock molecule

Liquid-crystalline, liquid-ordered, rippled and gel lipid bilayer phases as observed with nile red fluorescence

The basic matrix of cellular membranes consists of a double layer (bilayer) of phospholipids. Semisynthetic lipid bilayers are commonly used in biophysical studies of membranes. According to tem-perature and composition, lipid bilayers can exist in liquid-crystalline (or liquid-disordered), liquid -ordered, rippled, and gel phases. In the present study, the hydrophobic, solvatochromic molecule Nile red has been used as a fluorescent probe to examine the physical state of bilayers of different composi-tions in the 15-60 degrees C range. Phospholipids with saturated or unsaturated acyl chains, in the presence or absence of cholesterol have been studied. Nile red shows absorption maxima at 520-550 nm and emis-sion maxima at 580-640 nm, single photon excitation not being damaging to the system. A red/orange intensity ratio (ROIR) index has been used to normalize the results. ROIR varies clearly and reproducibly with the lipid phase, increasing in the order: liquid-ordered < gel < rippled < liquid-crystalline. It increases with temperature and decreases with cholesterol contents in the bilayers. Nile red allows an unusually clear observation of the rippled-to-liquid crystalline phase transition in saturated phospho-lipids. FLIM studies with Nile red also show differences between lamellar phases. Rotational relaxation times have been determined for Nile red in liquid-disordered (0.72 +/- 0.010 ns), gel (1.16 +/- 0.070 ns), and liquid-ordered (1.79 +/- 0.14 ns) phases, the large value of the liquid-ordered phase being an indication of the sterol hindering probe tumbling in the hydrophobic matrix.This work was supported in part by the Spanish Ministerio de Ciencia e Innovación (MCI), Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (grants No. PGC2018-099857-B-I00, PID2020-114755GB-C33 ), by the Basque Government (grants No. IT1625-22, IT1639-22,and IT1270-19), by Fundación Ramón Areces (CIVP20A6619), by Fundación Biofísica Bizkaia, and by the Basque Excellence Research Centre (BERC) program of the Basque Government

Formylation as a Chemical Tool to Modulate the Performance of Photosensitizers Based on Boron Dipyrromethene Dimers

Heavy-atom-free photosensitizers are envisioned as the next generation of photoactive molecules for photo-theragnosis. In this approach, and after suitable irradiation, a single molecular scaffold is able to visualize and kill tumour cells by fluorescence signalling and photodynamic therapy (PDT), respectively, with minimal side effects. In this regard, BODIPY-based orthogonal dimers have irrupted as suitable candidates for this aim. Herein, we analyse the photophysical properties of a set of formyl-functionalized BODIPY dimers to ascertain their suitability as fluorescent photosensitizers. The conducted computationally aided spectroscopic study determined that the fluorescence/singlet oxygen generation dual performance of these valuable BODIPY dimers not only depends on the BODIPY-BODIPY linkage and the steric hindrance around it, but also can be modulated by proper formyl functionalization at specific chromophoric positions. Thus, we propose regioselective formylation as an effective tool to modulate such a delicate photonic balance in BODIPY-based dimeric photosensitizers. The taming of the excited-state dynamics, in particular intramolecular charge transfer as the key underlying process mediating fluorescence deactivation vs. intersystem crossing increasing, could serve to increase fluorescence for brighter bioimaging, enhance the generation of singlet oxygen for killing activity, or balance both for photo-theragnosis.This research received financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN)/Agencia Estatal de Investigación (AEI) Grants: PID2020-114755GB-C32 and -C33 funded by MCIN/AEI/10.13039/501100011033. Gobierno Vasco (IT1639-22) is also grateful for the financial support

A Computational-Experimental Approach to Unravel the Excited State Landscape in Heavy-Atom Free BODIPY-Related Dyes

We performed a time-gated laser-spectroscopy study in a set of heavy-atom free single BODIPY fluorophores, supported by accurate, excited-state computational simulations of the key low-lying excited states in these chromophores. Despite the strong fluorescence of these emitters, we observed a significant fraction of time-delayed (microseconds scale) emission associated with processes that involved passage through the triplet manifold. The accuracy of the predictions of the energy arrangement and electronic nature of the low-lying singlet and triplet excited states meant that an unambiguous assignment of the main deactivation pathways, including thermally activated delayed fluorescence and/or room temperature phosphorescence, was possible. The observation of triplet state formation indicates a breakthrough in the “classic” interpretation of the photophysical properties of the renowned BODIPY and its derivatives.This research was funded by Spanish Ministerio de Economia y Competitividad (project PID2020-114755GB-C31, C32 and C33) and Gobierno Vasco (IT1639-22)

A Concise Synthesis of a BODIPY-Labeled Tetrasaccharide Related to the Antitumor PI-88

A convergent synthetic route to a tetrasaccharide related to PI-88, which allows the incorporation of a fluorescent BODIPY-label at the reducing-end, has been developed. The strategy, which features the use of 1,2-methyl orthoesters (MeOEs) as glycosyl donors, illustrates the usefulness of suitably-designed BODIPY dyes as glycosyl labels in synthetic strategies towards fluorescently-tagged oligosaccharides.This research was funded by Spanish MINISTERIO DE ECONOMIA Y COMPETITIVIDAD, GOBIERNO DE ESPAÑA (projects MAT2017–83856-C3-1-P and 3-P, PiD2020-1147555GB-C33), the MINISTERIO DE CIENCIA INNOVACION Y UNIVERSIDADES (project RTI2018-094862-B-I00), and the GOBIERNO VASCO (project IT912-16)

Adsorption and migration of Cs and Na ions in geopolymers and zeolites

Geopolymers may provide a more sustainable alternative to Portland Cement for various possible applications. Geopolymers have attracted particular interest for the immobilization of pollutants, owing to their high adsorption capacity, high thermal and chemical resistance, and low leachability. However, practical implementation is currently hindered by a limited understanding of how adsorption processes occur in geopolymers, and how they can be engineered to optimize the incorporation of pollutants and avoid their release. In this work, Molecular Dynamics simulations provide insights into these processes at the atomic scale, studying the role of host material composition and structure in the immobilization of Na and Cs ions. The simulations reveal that the most stable configurations for these ions are near the center of 6- and 8-membered aluminosilicate rings, where the coordination with the geopolymer is maximum. Higher contents of Al and degrees of crystallinity are found to yield more stable configurations for Cs ions, with more favorable adsorption enthalpies and lower diffusion coefficients. The comparison of different crystalline zeolite structures reveals that the framework of sodalite, used as the baseline to develop model geopolymer structures, is the most suitable for the immobilization of Cs since there are no channels and it is formed by small 4- and 6-member, all preventing Cs ions from escaping the cavities

Tuning the Photonic Behavior of Symmetrical bis-BODIPY Architectures: The Key Role of the Spacer Moiety

Herein we describe the synthesis, computationally assisted spectroscopy, and lasing properties of a new library of symmetric bridged bis-BODIPYs that differ in the nature of the spacer. Access to a series of BODIPY dimers is straightforward through synthetic modifications of the pending ortho-hydroxymethyl group of readily available C-8 (meso) ortho-hydroxymethyl phenyl BODIPYs. In this way, we have carried out the first systematic study of the photonic behavior of symmetric bridged bis-BODIPYs, which is effectively modulated by the length and/or stereoelectronic properties of the spacer unit. The designed bis-BODIPYs display bright fluorescence and laser emission in non-polar media. The fluorescence response is governed by the induction of a non-emissive intramolecular charge transfer (ICT) process, which is significantly enhanced in polar media. The effectiveness of the fluorescence quenching and also the prevailing charge transfer mechanism (from the spacer itself or between the BODIPY units) rely directly on the electron-releasing ability of the spacer. Moreover, the linker moiety can also promote intramolecular excitonic interactions, leading to excimer-like emission characterized by new spectral bands and the lengthening of lifetimes. The substantial influence of the bridging moiety on the emission behavior of these BODIPY dyads and their solvent-sensitivity highlight the intricate molecular dynamics upon excitation in multichromophoric systems. In this regard, the present work represents a breakthrough in the complex relationship between the molecular structure of the chromophores and their photophysical signatures, thus providing key guidelines for rationalizing the design of tailored bis-BODIPYs with potential advanced applications.We gratefully acknowledge the Spanish Ministerio de Economia y Competitividad (MINECO) (MAT2017-83856-C3-1-P and 3-P; CTQ2015-66702-R), Ministerio de Economia y Competitividad (MINECO), and Fondo Europeo de Desarrollo Regional (FEDER) (CTQ2015-66702-R, MINECO/FEDER, UE), Ministerio de Ciencia, Innovacion y Universidades (MCIU), Agencia Estatal de Investigacion (AEI), Fondo Europeo de Desarrollo Regional (FEDER) (RTI2018-094862-B-I00, MCIU/AEI/FEDER, UE), and Gobierno Vasco (project IT91216) for financial support. AO-S and RS-L thank UPV/EHU and Gobierno Vasco for a predoctoral fellowship and a postdoctoral contract, respectively

8-PropargylaminoBODIPY: unprecedented blue-emitting pyrromethene dye. Synthesis, photophysics and laser properties

Highly emitting 8-propargylaminoBODIPY (8-PAB) 2 was prepared in 94% yield. Unlike any other BODIPY structure hitherto described in the literature, 2 displays efficient emission in the blue region of the visible spectrum with a fluorescence quantum yield up to 0.94 and high laser efficiency (35%) at 483 nm.Grants GTO-2007-C02-69094 (CONCyTEG) (Mexico), MAT2007-65778-C02-01 and -02 of the Spanish MICINN are gratefully acknowledged. V. Martin thanks CSIC for her JAE-postdoctoral contract.Peer reviewe

Bichromatic laser emission from dipyrromethene dyes incorporated into solid polymeric media

9 pages, 9 figures.Bichromatic laser emission from dipyrromethene-based solid-state dye lasers is reported. The dependence of this dual emission on different factors and its origin and causes are discussed in the light of different models proposed in the literature. Our experimental results indicate that the long-wavelength emission can be explained in terms of reabsorption/reemission effects and inhomogeneous broadening of the S0-S1 transition. The short-wavelength emission corresponds to the usual S0-S1 transition and dominates at low dye concentration.This work was supported by Project Nos. MAT2004-04643-C03-01 and MAT2004-04643-C03-02 of the Spanish CICYT. One of the authors (M.Á.) thanks Ministerio de Ciencia y Tecnología (MCT) for a predoctoral grant. Another author (M.L.) thanks Comunidad Autónoma de Madrid for a postdoctoral grant and MCT for a Juan de la Cierva contract.Peer reviewe

An asymmetric BODIPY triad with panchromatic absorption for high-performance red-edge laser emission

© The Royal Society of Chemistry 2015. A rational design of an unprecedented asymmetric cassette triad based entirely on BODIPY chromophores allows efficient light harvesting over the UV-vis spectral region, leading to a bright and stable red-edge laser emission via efficient energy-transfer processes.Peer Reviewe