We report an efficient procedure to carry out palladium-catalyzed Miyaura borylation reactions of (hetero)aromatic halides and triflates in choline chloride (ChCl)-based deep eutectic solvents (DESs). The procedure employs bis(pinacolato)diboron as a boron source and a catalyst prepared in situ from readily available Pd(dba) and the phosphine ligand XPhos. Reactions proceed well in different ChCl-based DESs, among which the best results were provided by environmentally friendly and biodegradable mixtures with glycerol and glucose.
View Article and Find Full Text PDFAmong the emerging photovoltaic (PV) technologies, Dye-Sensitized Solar Cells (DSSCs) appear especially interesting in view of their potential for unconventional PV applications. In particular, DSSCs have been proven to provide excellent performances under indoor illumination, opening the way to their use in the field of low-power devices, such as wearable electronics and wireless sensor networks, including those relevant for application to the rapidly growing Internet of Things technology. Considering the low intensity of indoor light sources, efficient light capture constitutes a pivotal factor in optimizing cell efficiency.
View Article and Find Full Text PDFLuminescent solar concentrators (LSCs) are a class of optical devices able to harvest, downshift, and concentrate sunlight, thanks to the presence of emitting materials embedded in a polymer matrix. Use of LSCs in combination with silicon-based photovoltaic (PV) devices has been proposed as a viable strategy to enhance their ability to harvest diffuse light and facilitate their integration in the built environment. LSC performances can be improved by employing organic fluorophores with strong light absorption in the center of the solar spectrum and intense, red-shifted emission.
View Article and Find Full Text PDFRecently, great research efforts have been devoted to perovskite solar cells (PSCs) leading to sunlight-to-power conversion efficiencies above 25%. However, several barriers still hinder the full deployment of these devices. Critical issues are related to PCE stability and device lifetimes, which could be improved by targeted engineering of the hole transport material (HTM).
View Article and Find Full Text PDFOrganic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor-acceptor-donor (DAD) organic-emitting materials based on a thienopyrazine core.
View Article and Find Full Text PDFInvited for the cover of this issue are the groups of S. Seki (Kyoto), G. Reginato (Sesto Fiorentino), J.
View Article and Find Full Text PDFMulti-branched molecules have recently demonstrated interesting behaviour as charge-transporting materials within the fields of perovskite solar cells (PSCs). For this reason, extended triarylamine dendrons have been grafted onto a pillar[5]arene core to generate dendrimer-like compounds, which have been used as hole-transporting materials (HTMs) for PSCs. The performances of the solar cells containing these novel compounds have been extensively investigated.
View Article and Find Full Text PDFA new series of symmetrical organic dyes containing an indigo central core decorated with different electron donor groups have been prepared, starting from Tyrian Purple and using the Pd-catalyzed Stille-Migita coupling process. The effect of substituents on the spectroscopic properties of the dyes has been investigated theoretically and experimentally. In general, all dyes presented intense light absorption bands, both in the blue and red regions of the visible spectrum, conferring them a bright green color in solution.
View Article and Find Full Text PDFNew generation photovoltaic devices have attracted much attention in the last decades since they can be efficiently manufactured employing abundant raw materials and with less-energy intensive processes. In this context, the use of powerful environmental assessment is pivotal to support the fine-tuning of solar cells fabrication and hit the target of manufacturing effective sustainable technological devices. In this work, a mass-based green metrics and life cycle assessment combined approach is applied to analyze the environmental performances of an innovative synthetic protocol for the preparation of organic dye , which has been successfully proposed as sensitizer for manufacturing dye sensitized solar cells.
View Article and Find Full Text PDFThe design, synthesis, and characterization of a new class of blue-colored thiophene-substituted Pechmann dyes are reported. Due to a distinguishing blue coloration and the capability to absorb light in one of the most photon-dense regions of the solar spectrum, such compounds are of great interest for application as photoactive materials in organic optoelectronics, in particular, in dye-sensitized solar cells. To achieve fine tuning of the optical and electrochemical properties, the electron-poor thiophene-bis-lactone moiety has been decorated with donor (D) and acceptor groups (A), targeting fully conjugated D-A-π-A structures.
View Article and Find Full Text PDFThe cross-coupling reaction of organic electrophiles with organostannanes, traditionally known as the Stille reaction, has found renewed interest in the preparation of new organic materials such as conjugated polymers, organic semiconductors and photoactive molecules for use in organic photovoltaics. Moreover, a very recent field in which the Stille reaction has found successful application is that of the design and synthesis of new photosensitizers for dye-sensitized solar cells (DSSCs). DSSCs are considered a promising alternative for energy production from renewable sources.
View Article and Find Full Text PDFThe ethynylglycine synthon {(R)-2,2-dimethyl-3-(tert-butoxycarbonyl)-4-ethynyl-oxazolidine} is a chiral compound with valuable synthetic interest. An update (covering literature from 2005 to 2017) on the different synthetic utilities is reviewed and discussed.
View Article and Find Full Text PDFDonor-acceptor dyes are a well-established class of photosensitizers, used to enhance visible-light harvesting in solar cells and in direct photocatalytic reactions, such as H production by photoreforming of sacrificial electron donors (SEDs). Amines-typically triethanolamine (TEOA)-are commonly employed as SEDs in such reactions. Dye-sensitized photoreforming of more sustainable, biomass-derived alcohols, on the other hand, was only recently reported by using methanol as the electron donor.
View Article and Find Full Text PDFDye-sensitized solar cells (DSSCs) have attracted significant interest in the last few years as effective low-cost devices for solar energy conversion. We have analyzed the excited state dynamics of several organic dyes bearing both cyanoacrylic acid and siloxane anchoring groups. The spectroscopic properties of the dyes have been studied both in solution and when adsorbed on a TiO film using stationary and time-resolved techniques, probing the sub-picosecond to nanosecond time interval.
View Article and Find Full Text PDFThe preparation of 3-substituted tetrahydropyrazinoisoquinolines using the tributyltin hydride mediated intramolecular radical cyclization of suitably protected 2-substituted 3,4-dihydropyrazines is reported. The compounds are obtained as single enantiomers, as the relative configuration of the new generated stereogenic center is driven by the stereochemistry of the 2-substituted carbon in the starting materials, which is in turn derived from naturally occurring amino acids.
View Article and Find Full Text PDFThe ethynylglycine synthon {(R)-2,2-dimethyl-3-(tert-butoxycarbonyl)-4-ethynyloxazolidine} is a chiral compound with valuable synthetic interest. An update on the different routes for its synthesis is reviewed and discussed.
View Article and Find Full Text PDFThree new thiazolo[5,4-d]thiazole-based organic dyes have been designed and synthesized for employment as DSSC sensitizers. Alternation of the electron poor thiazolothiazole unit with two propylenedioxythiophene (ProDOT) groups ensured very intense light absorption in the visible region (ε up to 9.41 × 10(4) M(-1) cm(-1) in THF solution).
View Article and Find Full Text PDFMany pharmaceutical agents include piperazines or oxopiperazines as part of their core structures. The presence of substituents on these heterocycles has a significant influence on the biological activity, thus the search for efficient routes to control the substitution at different ring positions might have a crucial impact, especially to promote the use of such scaffolds in SAR studies. Many research groups have been engaged in the stereoselective synthesis of polysubstituted piperazines and oxopiperazines and in the majority of cases the stereochemistry of the final compounds is dependent on the starting material configuration.
View Article and Find Full Text PDFAsymmetric organocatalytic annulation of E/Z isomeric mixtures of bis(alkyl carboxylate)buta-1,3-dienes and aldehydes has been realized via enamine catalysis. In the presence of α,α-diphenyl-2-pyrrolidinemethanol trimethylsilyl ether, excellent stereo- and enantioselectivities were achieved for a broad spectrum of substrates.
View Article and Find Full Text PDFAn efficient synthesis of various protected syn-β-sulfenyl amides is described. These are prepared from the corresponding enantiopure amino allylsilanes which are in turn obtained from naturally occurring amino acids. The key step for introduction of the sulfur substituent is a diastereoselective electrophilic sulfodesilylation which is carried out with phthalimidesulfenyl chloride.
View Article and Find Full Text PDFA simple approach to a new family of enantiomerically enriched polyunsaturated t-Boc-protected-delta-amino esters is described, via microwave promoted Stille coupling of (Z)-methyl-2-bromobutenoate with stannylated allylamines. The reaction conditions are mild and selective and disclose a simple way to 1-substituted butenoates of defined geometry.
View Article and Find Full Text PDFThe reaction of [CpRuCl(PPh(3))(2)] (Cp = cyclopentadienyl) and [CpRuCl(dppe)] (dppe = Ph(2)PCH(2)CH(2)PPh(2)) with bis- and tris-phosphine ligands 1,4-(Ph(2)PC[triple bond]C)(2)C(6)H(4) (1) and 1,3,5-(Ph(2)PC[triple bond]C)(3)C(6)H(3) (2), prepared by Ni-catalysed cross-coupling reactions between terminal alkynes and diphenylchlorophosphine, has been investigated. Using metal-directed self-assembly methodologies, two linear bimetallic complexes, [{CpRuCl(PPh(3))}(2)(mu-dppab)] (3) and [{CpRu(dppe)}(2)(mu-dppab)](PF(6))(2) (4), and the mononuclear complex [CpRuCl(PPh(3))(eta(1)-dppab)] (6), which contains a "dangling arm" ligand, were prepared (dppab =1,4-bis[(diphenylphosphino)ethynyl]benzene). Moreover, by using the triphosphine 1,3,5-tris[(diphenylphosphino)ethynyl]benzene (tppab), the trimetallic [{CpRuCl(PPh(3))}(3)(mu(3)-tppab)] (5) species was synthesised, which is the first example of a chiral-at-ruthenium complex containing three different stereogenic centres.
View Article and Find Full Text PDFRing opening of amino epoxides derived from naturally occurring amino acids with lithium diphenylphosphido borane is reported as an efficient approach to a new family of enantiomerically enriched multifunctional phosphines.
View Article and Find Full Text PDFOne of the unresolved problems of solid-phase organic synthesis (SPOS) is the availability of general and rapid methods to monitor the transformation of functional groups present in molecules supported on insoluble supports. Color tests, far from providing the ultimate solution, may help in detection (and sometimes in quantification) of different functional groups. In this short review, we have collected most of the methods available and applied in SPOS with an Experimental Section that describes the procedure we have successfully applied to bead analyses in our laboratories.
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