Regioselectivity Control in Spirobifluorene Nitration under Mild Conditions: Explaining the Crivello's Reagent Mechanism.

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.

Thermally Activable Bistetrazoles for Elastomers Crosslinking.

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).

Pushing Down the Limit of NH3 Detection of Graphene-Based Chemiresistive Sensors through Functionalization by Thermally Activated Tetrazoles Dimerization.

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.

Bypassing the statistical limit of singlet generation in sensitized upconversion using fluorinated conjugated systems.

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.

Modular Synthetic Routes to Fluorine-Containing Halogenated Phenazine and Acridine Agents That Induce Rapid Iron Starvation in Methicillin-Resistant Staphylococcus aureus Biofilms.

During infection, bacteria use an arsenal of resistance mechanisms to negate antibiotic therapies. In addition, pathogenic bacteria form surface-attached biofilms bearing enriched populations of metabolically dormant persister cells. Bacteria develop resistance in response to antibiotic insults; however, nonreplicating biofilms are innately tolerant to all classes of antibiotics. As such, molecules that can eradicate antibiotic-resistant and antibiotic-tolerant bacteria are of importance. Here, we report modular synthetic routes to fluorine-containing halogenated phenazine (HP) and halogenated acridine (HA) agents with potent antibacterial and biofilm-killing activities. Nine fluorinated phenazines were rapidly accessed through a synthetic strategy involving (1) oxidation of fluorinated anilines to azobenzene intermediates, (2) SNAr with 2-methoxyaniline, and (3) cyclization to phenazines upon treatment with trifluoroacetic acid. Five structurally related acridine heterocycles were synthesized using SNAr and Buchwald-Hartwig approaches. From this focused collection, phenazines 5g, 5h, 5i, and acridine 9c demonstrated potent antibacterial activities against Gram-positive pathogens (MIC = 0.04-0.78 µM). Additionally, 5g and 9c eradicated Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis biofilms with excellent potency (5g, MBEC = 4.69-6.25 µM; 9c, MBEC = 4.69-50 µM). Using real-time quantitative polymerase chain reaction (RT-qPCR), 5g, 5h, 5i, and 9c rapidly induce the transcription of iron uptake biomarkers isdB and sbnC in methicillin-resistant S. aureus (MRSA) biofilms, and we conclude that these agents operate through iron starvation. Overall, fluorinated phenazine and acridine agents could lead to ground-breaking advances in the treatment of challenging bacterial infections.

Photoinduced Porcine Gelatin Cross-Linking by Homobi- and Homotrifunctional Tetrazoles.

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-linkers.

Morphological characterization and electronic properties of pristine and oxygen-exposed graphene nanoribbons on Ag(110).

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.

Highly enantioselective "inherently chiral" electroactive materials based on a 2,2'-biindole atropisomeric scaffold.

Chiral oligothiophene monomers with C 2 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-Based Hydrogels through Homobifunctional Triazolinediones Targeting Tyrosine Residues.

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 4,4'-hexane-1,6-diylbis(3H-1,2,4-triazoline-3,5(4H)-dione) 1 and 4,4'-[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.

Synthesis of corrugated C-based nanostructures by Br-corannulene oligomerization.

The structure and electronic properties of carbon-based nanostructures obtained by metal surface assisted synthesis is highly dependent on the nature of the precursor molecule. Here, we report on a combined scanning tunneling microscopy, soft X-ray spectroscopy and density functional theory investigation on the surface assisted polymerization of Br-corannulene at Ag(110) and on the possibility of building a mesh of π-conjugated polymers starting from buckyball shaped molecules. Indeed, the corannulene units form one-molecule-wide ribbons in which the natural concavity of the precursor molecule is maintained. These C-based nanostructures are corrugated and merge into a covalent network on the surface.

Impact on Prehospital Delay of a Stroke Preparedness Campaign: A SW-RCT (Stepped-Wedge Cluster Randomized Controlled Trial).

BACKGROUND AND PURPOSE: Public campaigns to increase stroke preparedness have been tested in different contexts, showing contradictory results. We evaluated the effectiveness of a stroke campaign, designed specifically for the Italian population in reducing prehospital delay. METHODS: According to an SW-RCT (Stepped-Wedge Cluster Randomized Controlled Trial) design, the campaign was launched in 4 provinces in the northern part of the region Emilia Romagna at 3-month intervals in randomized sequence. The units of analysis were the patients admitted to hospital, with stroke and transient ischemic attack, over a time period of 15 months, beginning 3 months before the intervention was launched in the first province to allow for baseline data collection. The proportion of early arrivals (within 2 hours of symptom onset) was the primary outcome. Thrombolysis rate and some behavioral end points were the secondary outcomes. Data were analyzed using a fixed-effect model, adjusting for cluster and time trends. RESULTS: We enrolled 1622 patients, 912 exposed and 710 nonexposed to the campaign. The proportion of early access was nonsignificantly lower in exposed patients (354 [38.8%] versus 315 [44.4%]; adjusted odds ratio, 0.81; 95% confidence interval, 0.60-1.08; P=0.15). As for secondary end points, an increase was found for stroke recognition, which approximated but did not reach statistical significance (P=0.07). CONCLUSIONS: Our campaign was not effective in reducing prehospital delay. Even if some limitations of the intervention, mainly in terms of duration, are taken into account, our study demonstrates that new communication strategies should be tested before large-scale implementation. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01881152.

Synthesis of graphene nanoribbons with a defined mixed edge-site sequence by surface assisted polymerization of (1,6)-dibromopyrene on Ag(110).

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.

One-pot sonochemical synthesis of ferrocenyl derivatives via a three-component reaction in aqueous media.

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.

On-surface photo-dissociation of C-Br bonds: towards room temperature Ullmann coupling.

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.

A structurally diverse heterocyclic library by decoration of oxcarbazepine scaffold.

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 α-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 α-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.

Intrathecal production of Chlamydia pneumoniae-specific high-affinity antibodies is significantly associated to a subset of multiple sclerosis patients with progressive forms.

The purpose of this study was to provide further insight into the effective relevance of the association between Chlamydia pneumoniae and MS. We evaluated by ELISA technique cerebrospinal fluid (CSF) and serum levels of anti-C. pneumoniae IgG in 46 relapsing-remitting (RR), 14 secondary progressive (SP) and 11 primary progressive (PP) MS patients grouped according to clinical and Magnetic Resonance Imaging (MRI) evidence of disease activity. Fifty-one patients with other inflammatory neurological disorders (OIND) and 52 with non-inflammatory neurological disorders (NIND) were used as controls. A C. pneumoniae-specific intrathecal IgG synthesis as detected by the relative specific index was present in a small proportion of MS (17%), OIND (22%) and NIND (2%) patients and was significantly more frequent in MS and in OIND than in NIND (p<0.001) and in SP and PP MS than in RR MS patients (p<0.02). Among the patients with C. pneumoniae-specific intratecally produced antibodies, CSF high-affinity anti-C. pneumoniae IgG were found in the majority of SP or PP MS, occasionally in OIND, but not in RR MS and NIND patients. These findings confirm that the presence of a humoral immune response to C. pneumoniae within the central nervous system (CNS) is not selectively restricted to MS, but is shared by several inflammatory neurological conditions. In addition, our results suggest that an intrathecal production of C. pneumoniae-specific high-affinity IgG can occur in a subset of patients with MS progressive forms in which a C. pneumoniae brain chronic persistent infection may play an important pathogenetic role.

Presence of detectable levels of soluble HLA-G molecules in CSF of relapsing-remitting multiple sclerosis: relationship with CSF soluble HLA-I and IL-10 concentrations and MRI findings.

We have investigated the presence of non-classical soluble HLA-G molecules (sHLA-G) in cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients and the possible relationships between CSF levels of sHLA-G, classical soluble HLA-I (sHLA-I) molecules, IL-10 amounts and Magnetic Resonance Imaging (MRI) findings were evaluated. We studied by ELISA technique the sHLA-I, sHLA-G and IL-10 levels in CSF of 50 relapsing-remitting (RR) MS patients stratified according to clinical and MRI evidence of disease activity. Thirty-six patients with other inflammatory neurological disorders (OIND) and 41 with non-inflammatory neurological disorders (NIND) were used as controls. CSF mean levels were significantly higher in MS and OIND than in NIND for sHLA-I (p<0.001) and in MS than in controls for sHLA-G (p<0.001), with no differences among the various groups for IL-10 mean concentrations. An increase in CSF sHLA-I was found in MS patients with Gd-enhancing lesions (p<0.01), while sHLA-G and IL-10 were more represented in MS patients without lesional activity on MRI scans (p<0.02). In MRI-inactive MS, CSF IL-10 mean concentrations were significantly greater in patients with CSF-detectable levels of sHLA-G than in those without any evidence of CSF sHLA-G expression (p<0.05). Our findings suggest that CSF classical sHLA-I and non-classical sHLA-G levels may modulate MS activity as assessed by MRI acting in opposite directions. The association observed between sHLA-G and IL-10 when Gd-enhancing lesion resolved indicates a potential immunoregulatory role for IL-10 in the control of MS disease activity by shifting the sHLA-I/sHLA-G balance towards sHLA-G response.

Clinical and MRI disease activity in multiple sclerosis are associated with reciprocal fluctuations in serum and cerebrospinal fluid levels of soluble HLA class I molecules.

The goal of our study was to clarify the contribution of soluble human leukocyte antigens class I (sHLA-I) in multiple sclerosis (MS) immune dysregulation. We retrospectively evaluated by ELISA cerebrospinal fluid (CSF) and serum sHLA-I levels in 79 relapsing-remitting (RR), 26 secondary progressive (SP) and 15 primary progressive (PP) MS patients stratified according to clinical and Magnetic Resonance Imaging (MRI) evidence of disease activity. One hundred and nine patients with other inflammatory neurological disorders (OIND), 88 with noninflammatory neurological disorders (NIND) and 82 healthy donors were used as controls. An intrathecal synthesis of sHLA-I detected by a specific index was significantly more consistent in MS than in controls, with more pronounced values in MS patients with relapses and MRI enhancing brain lesions. A decrease in serum sHLA-I concentrations was observed in MS patients with demyelinating attacks, while an increase in CSF levels of sHLA-I was found in MS patients with lesional activity on MRI scans. This association between intrathecal synthesis and reciprocal fluctuations of CSF and serum levels of sHLA-I in clinically and MRI active MS seems to suggest a potential role for CSF and serum levels of sHLA-I as a sensitive marker of immune activation taking place both intrathecally and systemically in MS.