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Organic–inorganic halide perovskite solar cells (PSCs) and organic solar cells(OSCs) attract great attention as alternative renewable photovoltaic technology.The state-of-the-art spiro-OMeTAD (2,20,7,70-tetrakis-(N,N-di-p-methoxyphe-nylamine)-9,90-spirobifluorene) is the most successful hole-transport material(HTM) employed in PSCs, whereas solution-processed inverted OSCs generallyuse poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS).Recently, various types of spirobifluorene-based organic small molecules arereported to overcome the known disadvantages of spiro-OMeTAD, such as thecomplex synthetic route, high synthetic cost, and requirement for hygroscopicdopants to improve the charge-carrier mobility and device performance.Examples of spirobifluorene-based molecules are also reported as alternativeHTMs in inverted OSCs to exceed the drawbacks of PEDOT:PSS, such as acidityand batch-to-batch reproducibility. These features significantly limit spiro-OMeTAD and PEDOT:PSS for large-scaleapplication in the future. Herein, anoverview of recent developments in spirobifluorene organic small molecules asHTM in PSCs and OSCs is provided by focusing on synthetic and electricalfeatures. Finally, the further research directions are discussed to develop novelspirobifluorene-based HTMs for the realization of reliable and long-term stablephotovoltaic devices.

A series of 2,2’-biindole-based inherently chiral electroactive monomers are comparatively investigated with their 3,3’ analogues as an excellent study case of two equivalent redox centres interacting through a torsional barrier. The twin peak potential splitting observed in voltammetry for the first oxidation of the biheteroaromatic core accounts for the energy barrier height: the lower the barrier, the larger the peak potential splitting, with modulation by solvent and temperature. The height of the energy barrier is determining for the electrochemical and spectroscopic features of the monomers as well as for their configurational stability and applicability for enantioselection purposes. The 3,3’ monomers, featuring large twin peak splittings in CV, are “trópos” systems with a low torsional barrier, so they cannot exist as stable enantiomers at room temperature. Instead their 2,2’ isomers, with much smaller twin peak splittings, are “átropos” systems and can be separated by enantioselective HPLC into stable enantiomers, providing powerful “inherently chiral” selectors with outstanding enantioselection properties in chiral electroanalysis and electrochemistry as well as in chiroptical spectroscopy, with fascinating reciprocal correlations.

The regioselective nitration of 9,9′-spirobifluorene under mild conditions is reported for the first time by operating under Menke’s and Crivello’s conditions. The optimized protocol allows obtaining 2-nitro and 2,2′-dinitro-9,9′-spirobifluorene in yields of 79 and 95% and, for the first time, 2,2′,7-trinitro-9,9′-spirobifluorene with 66% yield. Besides, the role of dinitrate salt in Crivello’s protocol has been now clarified, which opens novel scenarios in the preparation of functional materials.

The photon upconversion based on triplet–triplet annihilation (TTA) is a mechanism that converts the absorbed low-energy electromagnetic radiation into higher energy photons also at extremely low excitation intensities, but its use in actual technologies is still hindered by the limited availability of efficient annihilator moieties. We present here the results obtained by the synthesis and application of two new fluorinated chromophores based on phenazine and acridine structures, respectively. Both compounds show upconverted emission demonstrating their ability as TTA annihilator. More interesting, the acridine-based chromophore shows an excellent TTA yield that overcomes the one of some of best model systems. By correlating the experimental data and the quantum mechanical modeling of the investigated compound, we propose an alternative efficient pathway for the generation of the upconverted emissive states involving the peculiar high-energy triplet levels of the dye, thus suggesting a new development strategy for TTA annihilators based on the fine tuning of their high-energy excited states properties.

Sulfur vulcanization is the most used method for curing of natural and synthetic rubbers. The crosslinking degree achieved is usually controlled by adding proper quantities of accelerants, activators, co-activators, retardants, and inhibitors, and influences the hardness, elasticity, hysteresis of elastomers and, consequently, the properties and behavior of the materials that incorporate them. Despite the fine tuning pursued over the years, sulfur crosslinking is still difficult to control both in terms of degree and homogeneity of cross-link. Addition of thermally activable bifunctional reagents able to crosslink the polymer matrix through covalent bonds could be a strategy to modulate and control finely the reticulation grade of elastomers. Tetrazoles can form highly reactive nitrilimines by thermal treatment at appropriate temperature, which can react with the vinyl double bonds present in the rubber. In this work a set of bis-tetrazoles were synthesized and those with the right activation temperatures were used for the curing of styrene-butadiene rubber, acting both as single crosslinkers and together with classic sulfur-based ones. The addition of bistetrazoles simplified and made more efficient the compounding process, allowing to prolong the mixing until optimum dispersion and homogeneity were obtained. Moreover, they led to an improvement in the hysteretic properties of the compound and to the reduction of the non-linearity of the dynamic behavior (Payne effect).

An easy and cost-effective method is presented to functionalize graphene through thermally activated dimerization of 2,5-diaryltetrazoles. Consistently with the experimental spectroscopic results, theoretical calculations demonstrate that during the thermal treatment a dimerization process to tetrazine is energetically more favorable than covalent grafting. Since both the functionalization method by thermal activation and the use of tetrazoles have never been considered before to prepare graphene-based chemiresistors, this represents a promising approach to develop graphene-related sensing platforms. Five different 2,5-diaryltetrazoles have been tested here for the effective functionalization of low-defect graphene layers on silicon nitride. Based on these layers, an array of sensors has been prepared for testing upon ammonia exposure. The tests on the sensing performances clearly show sensitivity to ammonia, extending the current range of ammonia detection with a graphene-based chemiresistor down to the sub-ppm range, as results from a benchmarking with data available in the literature. Furthermore, all sensors perform better than bare graphene. Density functional theory (DFT) calculations, carried out on a model of the best performing layer of the array, provided the theoretical framework to rationalize the sensing mechanism and disclose a dual role played by the tetrazine molecules, (i) acting as ammonia concentrators and (ii) mediating the electron transfer between ammonia and graphene.

An easy and cost-effective method is presented to functionalize graphene through thermally activated dimerization of 2,5-diaryltetrazoles. Consistently with the experimental spectroscopic results, theoretical calculations demonstrate that during the thermal treatment a dimerization process to tetrazine is energetically more favorable than covalent grafting. Since both the functionalization method by thermal activation and the use of tetrazoles have never been considered before to prepare graphene-based chemiresistors, this represents a promising approach to develop graphene-related sensing platforms. Five different 2,5-diaryltetrazoles have been tested here for the effective functionalization of low-defect graphene layers on silicon nitride. Based on these layers, an array of sensors has been prepared for testing upon ammonia exposure. The tests on the sensing performances clearly show sensitivity to ammonia, extending the current range of ammonia detection with a graphene-based chemiresistor down to the sub-ppm range, as results from a benchmarking with data available in the literature. Furthermore, all sensors perform better than bare graphene. Density functional theory (DFT) calculations, carried out on a model of the best performing layer of the array, provided the theoretical framework to rationalize the sensing mechanism and disclose a dual role played by the tetrazine molecules, (i) acting as ammonia concentrators and (ii) mediating the electron transfer between ammonia and graphene.

In this paper we performed the deposition and self-assembly of a Pd-cyclometallated compound on Ag(1 1 0) surface for the first time. The system is investigated from the morphological and chemical point of view by scanning tunneling microscopy and x-ray photoemission spectroscopy, respectively, and the results are validated by ab-initio calculations. Our combined experimental and theoretical study aims at elucidating the atomistic details of the chemical steps following Pd cyclometallate deposition on the metallic substrate. To do that, we analyze the electronic and chemical properties of the species present on the surface at the end of the preparation process at room temperature and at 150 °C. We observe an unexpected complex chemistry: on one side, the organometallic molecules are found to dissociate into fragments, forming a well-ordered metal–carbon network; on the other side, Pd atoms become buried in the bulk of the metal substrate following metal exchange with surface Ag atoms. The details of this mechanistic study reveal the active role played by the metal substrate in promoting the chemistry of the deposited Pd cyclometallates and could open new perspectives for the application of this class of materials in heterogeneous catalysis.

The Suzuki–Miyaura cross-coupling reaction plays a fundamental role in modern synthetic organic chemistry, both in academia and industry. For this reason, scientists continue to search for new, more effective, cheaper and environmentally friendly procedures. Recently, micellar synthetic chemistry has been demonstrated to be an excellent strategy for achieving chemical transformations in a more efficient way, thanks to the creation of nanoreactors in aqueous environments using selected surfactants. In particular, the cheap and commercially available surfactant Kolliphor EL (a polyethoxylated castor oil derivative) has been used with success to achieve metal-catalyzed transformations in water with high yields and short reaction times, with the advantage of using air-sensitive catalysts without the need for inert atmosphere. In this work, the Kolliphor EL methodology was applied to the Suzuki cross-coupling reaction between thiophene and aniline, using the highly effective catalyst Pd(dtbpf)Cl2. The cross-coupling products were achieved at up to 98% yield, with reaction times of up to only 15 min, working at room temperature and without the need for inert atmosphere.

Gelatin is a costless polypeptide material of natural origin, able to form hydrogels that are potentially useful in biomaterial scaffold design for drug delivery, cell cultures, and tissue engineering. However, gelatin hydrogels are unstable at physiological conditions, losing their features only after a few minutes at 37 °C. Accordingly, treatments to address this issue are of great interest. In the present work, we propose for the first time the use of bi- and trifunctional tetrazoles, most of them unknown to date, for photoinduced gelatin cross-linking towards the production of physiologically stable hydrogels. Indeed, after UV-B irradiation, aryl tetrazoles generate a nitrilimine intermediate that is reactive towards different functionalities, some of them constitutively present in the amino acid side chains of gelatin. The efficacy of the treatment strictly depends on the structure of the cross-linking agent used, and substantial improved stability was observed by switching from bifunctional to trifunctional cross-linker

PHANE-TetraPHOS, a new D2 symmetric tetraphosphane based on the [2.2]paracyclophane scaffold, has been synthesized and characterized. The peculiarity of this system is the presence of four homotopic diphenylphosphane groups, exchangeable through C2 symmetry operations and consequently indistinguishable. Their spatial arrangement allows the simultaneous complexation of two metal atoms. Enantiomeric purity wasattained at tetra-phosphane oxide level by fractional crystallization of the diastereomeric adducts obtained from the racemate with enantiopure dibenzoyltartaric acids. Alkaline treatment ofdiastereomerically pure adducts followed by exhaustive PO groups reduction with HSiCl3 gave both PHANE-TetraPHOS antipodes in an enantiopure state. They were tested as rhodium ligands in the homogeneous enantioselective hydrogenation ofsome benchmark unsaturated compounds. Catalytic activity and enantiodiscrimination ability were found comparable tothose exhibited by the complexes of the parent bidentate ligand PHANEPHOS, but only half a mole of precious chiral ligand was employed.

Graphene nanoribbons (GNRs) are at the frontier of research on graphene materials since the 1D quantum confinement of electrons allows for the opening of an energy gap. GNRs of uniform and well-defined size and shape can be grown using the bottom-up approach, i.e. by surface assisted polymerization of aromatic hydrocarbons. Since the electronic properties of the nanostructures depend on their width and on their edge states, by careful choice of the precursor molecule it is possible to design GNRs with tailored properties. A key issue for their application in nanoelectronics is their stability under operative conditions. Here, we characterize pristine and oxygen-exposed 1.0 nm wide GNRs with a well-defined mixed edge-site sequence (two zig-zag and one armchair) synthesized on Ag(110) from 1,6-dibromo-pyrene precursors. The energy gap and the presence of quantum confined states are investigated by scanning tunneling spectroscopy. The effect of oxygen exposure under ultra-high vacuum conditions is inferred from scanning tunneling microscopy images and photoemission spectra. Our results demonstrate that oxygen exposure deeply affects the overall system by interacting both with the nanoribbons and with the substrate; this factor must be considered for supported GNRs under operative conditions.

Medical-grade poly(methyl methacrylate) (PMMA) is widely employed in the fabrication of intraocular lenses (IOLs), but suffers from opacification, a postoperative complication that leads to the failure of the implanted intraocular lenses. The opacification occurs when inorganic-based deposits accumulate on the surface of the IOL and are prevalent in hydrophilic materials. Here, the surface of medical-gradePMMAhas been fluorinated by sulphur hexafluoride (SF6) plasma treatment to increase surface hydrophobicity thus improving the material lifetime in optical applications. Hydrophobic properties of the treated PMMA were investigated by means of contact angle measurements, while chemical modification was assessed by X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR/FTIR) spectroscopy. Surface morphological changes due to possible etching effects were investigated by Atomic Force Microscopy (AFM). The transparency of the treated PMMA was assessed by UV/VIS spectroscopy. Finally, the influence of the plasma treatment on the inorganic salts deposition was investigated by immersion in Simulated Aqueous Humour (SAH), followed by XPS analysis. The modified samples showed less deposition on the surface than the unmodified sample, moreover, a decrease of the transmittance in the UV-violet range (300-430 nm) was detected, open the possibility of interesting applications of this treatment for the creation of a UV filter in ophthalmic optical devices.

A high ortho regioselectivity in nucleophilic aromatic substitution in low polar solvents is reported in the reaction of polyfluorinated azobenzenes with anilines. o-Anilino substituted derivatives could be easily transformed into non-symmetric phenazines by acid catalyzed electrocyclization. Phenazines are interesting compounds for their important properties as bioactive molecules. In addition, these fluorinated phenazines manifest interesting spectroscopic and electronic properties that make them candidates for n-type organic semiconductor. Furthermore, the prepared phenazines show reversible reduction with the LUMO and HOMO energy level controlled by the electronic nature of the substituent on the non-fluorinated ring of the system.

Chiral oligothiophene monomers with C2 symmetry, based on 3,3′-bithiophene atropisomeric cores with high racemization barriers, have recently been shown to provide excellent chiral starting materials with high electroactivity for the easy preparation of enantiopure electroactive films endowed with powerful chirality manifestations. We now introduce an inherently chiral monomer based on a 2,2′-biindole core, as the prototype of a new inherently chiral monomer family, whose properties could be modulable through functionalization of the pyrrolic N atoms. By fast, regular electrooligomerization the new monomer yields inherently chiral films with high, reversible electroactivity and, above all, impressive enantioselectivity towards very different chiral probes, some of pharmaceutical interest, as general-scope electrode surfaces. Such results, while opening the way to a new, attractive inherently chiral selector class, nicely confirm the general validity of the inherent chirality strategy for chiral electrochemistry. Furthermore, the enantioselectivity of the new selectors not only holds with electroactive chiral probes, but also with circularly polarized light components as well as electron spins, resulting in good chiroptical and spin filter performances, which suggests fascinating correlations between the three contexts.

Gelatin is a biopolymer with interesting properties that can be useful for biomaterial design for different applications such as drug delivery systems, or 3D scaffolds for tissue engineering. However, gelatin suffers from poor mechanical stability at physiological temperature, hence methods for improving its properties are highly desirable. In the present work, a new chemical cross-linking strategy based on triazolinedione ene-type chemistry towards stable hydrogel is proposed. Two different homobifunctional 1,2,4-triazoline-3,5(4H)-diones, namely 4,40-hexane-1,6-diylbis(3H-1,2,4-triazoline-3,5(4H)-dione) 1 and 4,40-[methylenebis(4,1-phenylene)]bis(3H-1,2,4-triazoline-3,5(4H)-dione) 2 were used as cross-linkers in different ratio to tyrosine residues in gelatin. The reaction was proved effective in all experimented conditions and hydrogels featured with different thermal stability were obtained. In general, the higher the cross-linker/tyrosine ratio, the more thermostable the hydrogel. The swelling properties are strictly dependent upon the chemical nature of the cross-linker.

A solventless mechanochemical methodology for the oxidation of electron-poor fluorinated anilines to the corresponding symmetrical azo compounds has been developed. In this process phenyliodine(III)diacetate and inexpensive calcium hypochlorite demonstrate to be good oxidants, providing the desired fluorinated azobenzenes in satisfactory yields, within short reaction times and avoiding the use of environmental unfriendly metal reagents.

Fluorinated unsymmetrical acridines are efficiently prepared by means of a tandem micellar Buchwald-Hartwig amination followed by an acid-promoted cyclization. The overall process is advantageous with respect to previously described protocols both in terms of efficiency and sustainability. The role of the cosolvent in the amination step is highlighted, demonstrating that rather than resorting to highly expensive catalysts, Buchwald-Hartwig aminations can be straightforwardly carried out by tuning the reaction site polarity.

A novel centrosymmetric porphyrazine (Pz) 1 decorated with pyrazino-dibenzo[b,f]azepine units have been prepared via Linstead macrocyclization reaction of a dinitrile precursor. Accordingly, the peripheral azepine nitrogen offers a chemical handle for subsequent functionalizations. Characterization of the metal complexes (MPzs = Metal Porphyrazines) of 1 was accomplished and good catalytic performances were achieved in the Cu(II)- and Co(II)- catalyzed cyclopropanation with ethyl diazoacetate as a test reaction.

Intraocular lenses can be manufactured from a wide variety of polymers, but due to the lost cost associated with the use of Poly(methyl methacrylate) (PMMA), it is still the preferred material used in the developing countries. However, a major drawback to its use is the build-up of calcium containing deposits that are formed on the intraocular lens over a period of time. In an attempt to hinder this deposition, surface modification of medical grade PMMA has been carried out using perfluoroalkyl chain (1,2,4-trifluoro-3- (C10F21CH2O)-7-(N,N)-dimethylaminoacridine) segregation. The segregation was explored using a 1% 1,2,4-trifluoro-3-(C10F21CH2O)-7-(N,N)-dimethylaminoacridine in two methods: film casting and spin-coating, a thin film onto preformed PMMA discs. Both methods were compared against control PMMA to determine which method provided the best hindrance against calcium containing deposits when immersed in a simulated aqueous humour solution. Characterisation of the surface using scanning electron microscopy coupled with energy; dispersive x-ray analysis indicated that the surface segregation of perfluoroalkyl chains had hindered calcification in both methods. This pleminary research shows promising results of employing perfluoroalkyl chains in the surface segregation of biomaterials that can be employed in intraocular lenses.

On-surface synthesis of thin organic and organometallic films in a bottom-up fashion has become a promising approach for the development of new nanotechnologies. In this work we studied 5,11-dibromotetracene (C18H10Br2) as a prototypical case of rodlike polyaromatic molecules functionalized with two bromine atoms on the sides. The adsorption and temperature-stimulated transformations of dibromotetracene assemblies on Ag(110) have been investigated by a combination of synchrotron radiation X-ray photoemission spectroscopy (XPS), near-edge X-ray absorption spectroscopy (NEXAFS), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Upon the contact with the Ag substrate, the Br-C bonds are promptly cleaved at room temperature, and Ag-coordinated protopolymers are formed along the [001] substrate direction. The organometallic dimers and trimers remain on the surface up to 523 K. The stabilization of the protopolymers is driven by the substrate anisotropy and weak interactions with nearby Br atoms. The short oligomers formed at elevated temperatures are weakly bounded to the substrate and desorb before covalent structures can be formed.

By a combination of scanning tunneling microscopy, X-ray spectroscopic techniques and density functional theory calculations, we prove the formation of extended patterns of parallel, graphene nanoribbons with alternate zig-zag and armchair edges and selected width by surface-assisted Ullmann coupling polymerization and dehydrogenation of 1,6-dibromopyrene (C16H8Br2). Besides the relevance of these nanostructures for their possible application in nanodevices, we demonstrate the peculiarity of halogenated pyrene derivatives for the formation of nanoribbons, in particular on Ag(110). These results open the possibility of tuning the shape and dimension of nanoribbons (and hence the correlated electronic properties) by choosing suitably tailored or on-purpose designed molecular precursors.

The surface-assisted synthesis of gold-organometallic hybrids on the Au(111) surface both by thermo- and light-initiated dehalogenation of bromo-substituted tetracene is reported. Combined X-ray photoemission (XPS) and scanning tunneling microscopy (STM) data reveal a significant increase of the surface order when mild reaction conditions are combined with 405 nm light irradiation.

An ultrasound-assisted three-component, one-pot domino reaction with ferrocenecarboxaldehyde is herein reported. The sequence of reactions entails the allylindation and dehydrative alkylation of stabilized C-nucleophiles (e.g. electron-rich - (hetero)aromatics and stabilized enols) and N-nucleophiles (e.g. azoles). Sonochemical reactions have been performed in three different high-intensity reactors: a bath (20.3 kHz, 60 W), as well as two cup horns working at 19.9 kHz (75 W) and 300.5 kHz (70 W) giving a library of 18 new ferrocenyl derivatives.

The title compound was easily prepared by a nitrosoarene-alkyne cycloaddition reaction carried out in toluene at 80 °C. The product is a highly functionalized compound that can be further derivatized through various functional group interconversion procedures. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

A library of new heterocyclic systems was synthesized starting from oxcarbazepine (OXC, Trileptal®, 10-oxo-10,11-dihydro-5H-dibenzo[b,f]azepine- 5-carboxamide). The key for these transformations is the a-enolizable ketone present on the [d]-side of our starting material OXC, thus, an in depth investigation of the literature to find heteroannulation reactions for substrates carrying an a-enolizable ketone gave us a boost to discover an excellent derivatization strategy and [3+2], [4+2] and [4+1] approaches were successfully developed. Almost always a pre-functionalization was needed, but also the direct one-pot heterocycle construction was also explored. © 2013 by the authors.

Unknown 1H-2,7-dihydro-1-phenylphosphepine, containing a 2,2,5,5-tetramethyl-3,3-bithiophene atropisomeric scaffold (Ph-tetraMe- Bithienine), and its oxide have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. The most evident structural feature is the very small dihedral angle. The electronic properties of the phosphane were quantitatively evaluated by cyclic voltammetry and compared with three other 2,7-dihydro-1-phenylphosphepines differing in the nature of the biaromatic scaffold (biphenyl, 1,1-binaphthyl and 2,2-dimethoxybiphenyl). The racemate of the phosphane oxide was resolved into antipodes, which were reduced to the enantiopure phosphanes and employed as ligands in Rh and Pt complexes in homogeneous stereoselective catalytic reactions. The enantioselective ability and catalytic activity of the new mediators were found to be quite modest in the hydrogenation reactions of olefinic double bonds, whereas good performances were achieved in specific C-C bond-forming reactions. The results are interpreted on the basis of the steric and electronic properties of the ligand. Ph-tetraMe-Bithienine, an unknown phosphepine containing a 3,3-bithiophene scaffold, and its oxide have been synthesized, resolved into antipodes, and structurally and electronically characterized. The enantioselective ability and catalytic activity of metal complexes of the ligand were investigated in C=C hydrogenation reactions and C-C bond-forming reactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.