Simonetta Orlandi

FIRST EXAMPLE OF A SILICA GEL-SUPPORTED OPTICALLY ACTIVE MN(III)-SALEN COMPLEX AS A HETEROGENEOUS ASYMMETRIC CATALYST IN THE EPOXIDATION OF OLEFINS

Abstract An optically active Mn(III)–salen complex was supported on silica gel materials: the insoluble systems obtained were employed as catalysts in the asymmetric epoxidation of some aromatic olefins. Enantiomeric excess values up to 58% were obtained.

A reusable, insoluble polymer-bound bis(oxazoline) (IPB-box) for highly enantioselective heterogeneous cyclopropanation reactionsElectronic supplementary information (ESI) available: experimental. See http://www.rsc.org/suppdata/cc/b3/b306483b/

A reusable, insoluble polystyrene-supported bis(oxazoline) was developed, affording e.e.s > 90% in the heterogeneous enantioselective cyclopropanation of styrene and 1,1-disubstituted alkenes with ethyl diazoacetate.

Synthesis and Photovoltaic Applications of a 4,4′-Spirobi[cyclopenta[2,1-b;3,4-b′]dithiophene]-Bridged Donor/Acceptor Dye

A new donor/acceptor (D-A) spiro dye (SCPDT1) featuring two bithiophene units, connected through an sp(3)-hybridized carbon atom, was prepared by a multistep synthetic sequence involving the convenient assembly of the spiro system under mild catalytic conditions. The photocurrent spectrum of dye-sensitized solar cells incorporating SCPDT1 covers the spectral region ranging from 350 to 700 nm and reaches a wide maximum of ~80% in the 420-560 nm range. Power conversion efficiencies of up to 6.02% were obtained.

A templating guest sorts out a molecular triangle from a dimer–trimer constitutional dynamic library

Cu(II) and a bis-β-diketone ligand generate a small constitutional dynamic library (CDL). The designed introduction of a well suited guest drives the self-sorting of the system toward a supramolecular triangle. Alternatively, the triangle self-assembly is templated by the same guest in a one-pot synthesis.

A first example of macromolecular Ti(IV) Lewis acid in the catalytic enantioselective Mukaiyama reaction

Abstract The preparation and characterization of a soluble copolymer P1 between styrene, divinylbenzene (DVB) and the enantiomerically pure salicylaldimine ligand 3c is described. The Lewis acid prepared from this macromolecular chiral ligand and Ti(OiPr)4 has been used in the catalytic Mukaiyama reaction to afford benzyl (R)-3-hydroxy-3-phenylpropanoate 7.

Polar fluorenes and spirobifluorenes: fluorescence and fluorescence anisotropy spectra.

An extensive spectroscopic study is presented of two asymmetrically substituted fluorene dyes and of the related spiro dimers in both liquid and glassy solvents. Essential-state models are developed to accurately reproduce linear absorption and fluorescence spectra and their complex dependence on solvent polarity. The same models are exploited to quantitatively calculate fluorescence excitation and anisotropy spectra in rigid matrixes. Impressive red-edge effects observed for spiro dimers in glassy polar solvents are accurately reproduced and understood. Interchromophore interactions in the spiro dimers are very small, leading to marginal effects in absorption and fluorescence spectra, but they effectively promote energy transfer between the two chromophores, as best evidenced comparing anisotropy spectra of the substituted fluorenes and of corresponding spiro dimers dissolved in glassy solvent matrixes.

Synthesis and catalytic activity of fluorous chiral primary amine-thioureas

Three enantiopure fluorous thioureas featuring a free –NH2 group were synthesized by direct addition of aromatic isothiocyanates bearing a single n-C8F17 substituent in the ortho, meta and para position, respectively, to enantiopure (1R,2R)-1,2-diaminocyclohexane. The catalytic behavior of these bifunctional molecules was assessed in representative Michael-type reactions. The three fluorous thioureas performed similarly in all the reactions tested, thus showing that the position of the fluorous ponytail does not have a major influence on the catalytic behavior of this class of compounds. In particular, excellent enantioselectivities (up to 99% ee) and yields (up to 98%) were obtained for the addition of aliphatic aldehydes to maleimides to give α-substituted succinimides. Recyclability of these primary amine-based thioureas was found to be limited by the concurrent formation of imine-derivatives during the catalytic process, leading to a structural modification of the organic catalyst.

Femtosecond Charge-Injection Dynamics at Hybrid Perovskite Interfaces

With a power conversion efficiency (PCE) exceeding 22 %, perovskite solar cells (PSCs) have thrilled photovoltaic research. However, the interface behavior is still not understood and is a hot topic of research: different processes occur over a hierarchy of timescales, from femtoseconds to seconds, which makes perovskite interface physics intriguing. Herein, through femtosecond transient absorption spectroscopy with spectral coverage extending into the crucial IR region, the ultrafast interface-specific processes at standard and newly molecularly engineered perovskite interfaces in state-of-the-art PSCs are interrogated. Ultrafast interfacial charge injection occurs with a time constant of 100 fs, resulting in hot transfer from energetic charges and setting the timescale for the first step involved in the complex charge-transfer process. This is also true for 20 % efficient devices measured under real operation, for which the femtosecond injection is followed by a slower picosecond component. These findings provide compelling evidence for the femtosecond interfacial charge-injection step and demonstrate a robust method for the straightforward identification of interfacial non-equilibrium processes on the ultrafast timescale.

Water-Repellent Low-Dimensional Fluorous Perovskite as Interfacial Coating for 20% Efficient Solar Cells

Hybrid perovskite solar cells have been capturing an enormous research interest in the energy sector due to their extraordinary performances and ease of fabrication. However, low device lifetime, mainly due to material and device degradation upon water exposure, challenges their near-future commercialization. Here, we synthesized a new fluorous organic cation used as organic spacer to form a low-dimensional perovskite (LDP) with an enhanced water-resistant character. The LDP is integrated with three-dimensional (3D) perovskite absorbers in the form of MA0.9FA0.1PbI3 (FA = NH2CH = NH2+, MA = CH3NH3+) and Cs0.1FA0.74MA0.13PbI2.48Br0.39. In both cases, a LDP layer self-assembles as a thin capping layer on the top of the 3D bulk, making the perovskite surface hydrophobic. Our easy and robust approach, validated for different perovskite compositions, limits the interface deterioration in perovskite solar cells yielding to >20% power conversion efficient solar cells with improved stability, especially pronounced in the first hours of functioning under environmental conditions. As a consequence, single and multijunction perovskite devices, such as tandem solar cells, can benefit from the use of the waterproof stabilization here demonstrated, a concept which can be further expanded in the perovskite optoelectronic industry beyond photovoltaics.

Dye-sensitized solar cells based on a push-pull zinc phthalocyanine bearing diphenylamine donor groups : computational predictions face experimental reality

Computational studies have suggested that the integration of secondary amine as donor groups in the structure of unsymmetrical zinc phthalocyanine (ZnPc) should have positive effects on photovoltaic performance, once the molecule is integrated as light harvester in dye sensitized solar cells (DSSCs). Aiming at obtaining experimental confirmation, we synthesized a peripherally substituted push-pull ZnPc bearing three electron donating diphenylamine substituents and a carboxylic acid anchoring group and integrated it as sensitizer in TiO2-based DSSCs. Detailed functional characterization of solar energy converting devices resulted in ruling out the original hypothesis. The causes of this discrepancy have been highlighted, leading to a better understanding of the conditions for an effective design of push-pull diarylamino substituted ZnPcs for DSSCs.