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Catechols have been largely investigated as antiaggregating agents toward β-amyloid peptide. Herein, as a follow up of a previous series of hydroxycinnamic derivatives, we synthesized a small set of dihydroxy isomers for exploring the role of the reciprocal position of the two hydroxyl functions at a molecular level.

A family of dinuclear tricarbonyl rhenium (I) complexes containing bridging 1,2-diazine ligand and halide anions as ancillary ligands and able to catalyze CO2 reduction is presented. Electrochemical studies show that the highest catalytic efficiency is obtained for the complex containing the 4,5-bipenthyl-pyridazine and iodide as ancillary halogen ligands. This complex gives rise to TOF=15 s−1 that clearly outperforms the values reported for the benchmark mononuclear Re(CO)3Cl(bpy) (11.1 s−1). The role of the substituents on the pyridazine ligand and the nature of the bridging halide ligands on the catalytic activity have been deeply investigated through a systematic study on the structure-properties relationship to understand the improved catalytic efficiencies of this class of complexes.

The inhibition of the Epidermal Growth Factor (EGFR) represents one of the most promising strategies in non-small cell lung cancer (NSCLC) therapy. The recently identified C797S mutation causes resistance of EGFRsupL858R/T790M/supagainst osimertinib, the latest approved third generation EGFR inhibitor. The identification of small molecules capable of selectively inhibiting the T790M mutations also in the late-onset C797S mutation is a desirable strategy and novel chemical structures might provide new insight in the overcoming resistance mechanisms. Here we report the identification of a novel mutant-selective privileged molecular core; guided by a structure-based drug design, a flavone skeleton has been rationally modified, and a virtual library generated. Reversible EGFR inhibitors targeting both L858R/T790M and L858R/T790M/C797S mutations with a higher affinity with respect to the wild type one are discovered via a three-track virtual screening. Selected hits were synthesized and tested in an activity-based enzyme assay against wild-type EGFR, L858R/T790M, as well as L858R/T790M/C797S. The results showed that a nitroflavone-based compound inhibits the phosphorylation of EGFR mutants at low-micromolar concentration showing selectivity over the wild type ones. Structurally similar flavone analogues have been synthesized and the following inhibition assays underlied the importance of both the presence and position of the nitrophenoxy moiety.

Carbon nanotubes (CNTs) are currently under active investigation for their use in several biomedical applications, especially in neurological diseases and nervous system injury due to their electrochemical properties. Nowadays, no CNT-based therapeutic products for internal use appear to be close to the market, due to the still limited knowledge on their fate after delivery to living organisms and, in particular, on their toxicological profile. The purpose of the present work was to address the distribution in the brain parenchyma of two intranasally delivered MWCNTs (MWCNTs 1 and a-MWCNTs 2), different from each other, the first being non electroconductive while the second results in being electroconductive. After intranasal delivery, the presence of CNTs was investigated in several brain areas, discriminating the specific cell types involved in the CNT uptake. We also aimed to verify the neuroprotective potential of the two types of CNTs, delivering them in rats affected by early diabetic encephalopathy and analysing the modulation of nerve growth factor metabolism and the effects of CNTs on the neuronal and glial phenotypes. Our findings showed that both CNT types, when intranasally delivered, reached numerous brain areas and, in particular, the limbic area that plays a crucial role in the development and progression of major neurodegenerative diseases. Furthermore, we demonstrated that electroconductive MWCNTs were able to exert neuroprotective effects through the modulation of a key neurotrophic factor and probably the improvement of neurodegeneration-related gliosis.

The synthesis of π‐extended porphyrins containing anthracenyl moieties still represents an important challenge. Here, we report on the synthesis of a series of unsubstituted naphthyl‐, pyrenyl‐ and anthracenyl‐fused zinc porphyrin derivatives. To this aim, meso‐substitued porphyrins are synthesized and the fusion of the PAHs (Polycyclic Aromatic Hydrocarbon) on the β‐positions are performed through thermally induced dehydro‐aromatization. The fused zinc‐porphyrin derivatives are fully characterized and their optical absorption and photoluminescence properties are reported. We also demonstrate that zinc can be removed from the porphyrin core, giving rise to pure C, H, N materials. This work constitutes the first step towards the synthesis of the fully‐fused tetra‐anthracenylporphyrin., A series of π‐extented porphyrins are synthesized by thermal cyclodehydrogenation of porphyrins functionalized with unsubstituted PAHs. The fused porphyrin derivatives can be demetalated to give rise to the unsubstituted and metal‐free porphyrin dyes.

Planar and curved polycyclic aromatic hydrocarbons (PAHs) represent an interesting class of compounds with physical chemical properties particularly appealing, as good organic semiconductors and molecular model of larger carbon nano- structures. Investigation of the heterogeneous electron transfer in these systems lets to probe their electronic properties and the reactivity of the corresponding generated carbanions and carbocations that can form new bonds, thus leading to different carbon systems. A particular focus is on the intrinsically high reactivity of carbocations which induces a series of reactions building up new carbon–carbon bonds, thus allowing to enlarge the initial molecular unit into a nanostructure. This represents a new and convenient way to exploit the electro- chemically triggered reactivity into the synthesis of carbon nanostructured materials.

Synthetic nitrone spin-traps are being explored as therapeutic agents for the treatment of a wide range of oxidative stress-related pathologies, including but not limited to stroke, cancer, cardiovascular, and neurodegenerative diseases. In this context, increasing efforts are currently being made to the design and synthesis of new nitrone-based compounds with enhanced efficacy. The most researched nitrones are surely the ones related to α-phenyl-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) derivatives, which have shown to possess potent biological activity in many experimental animal models. However, more recently, nitrones with a benzoxazinic structure (3-aryl-2H-benzo[1,4]oxazin-N-oxides) have been demonstrated to have superior antioxidant activity compared to PBN. In this study, two new benzoxazinic nitrones bearing an electron-withdrawing methoxycarbonyl group on the benzo moiety (in para and meta positions respect to the nitronyl function) were synthesized. Their in vitro antioxidant activity was evaluated by two cellular-based assays (inhibition of AAPH-induced human erythrocyte hemolysis and cell death in human retinal pigmented epithelium (ARPE-19) cells) and a chemical approach by means of the α,α-diphenyl-β-picrylhydrazyl (DPPH) scavenging assay, using both electron paramagnetic resonance (EPR) spectroscopy and UV spectrophotometry. A computational approach was also used to investigate their potential primary mechanism of antioxidant action, as well as to rationalize the effect of functionalization on the nitrones reactivity toward DPPH, chosen as model radical in this study. Further insights were also gathered by exploring the nitrone electrochemical properties via cyclic voltammetry and by studying their kinetic behavior by means of EPR spectroscopy. Results showed that the introduction of an electron-withdrawing group in the phenyl moiety in the para position significantly increased the antioxidant capacity of benzoxazinic nitrones both in cell and cell-free systems. From the mechanistic point of view, the calculated results closely matched the experimental findings, strongly suggesting that the H-atom transfer (HAT) is likely to be the primary mechanism in the DPPH quenching.

Chiral electroanalysis could be regarded as the highest recognition degree in electrochemical sensing, implying the ability to discriminate between specular images of an electroactive molecule, particularly in terms of significant peak potential difference. A groundbreaking strategy was recently proposed, based on the use of "inherently chiral" molecular selectors, with chirality and key functional properties originating from the same structural element. Large differences in peak potentials have been observed for the enantiomers of different chiral molecules, also of applicative interest, using different selectors, all of them based on atropisomeric biheteroaromatic scaffolds of axial stereogenicity. However, helicene systems also provide inherently chiral building blocks with attractive features. In this paper the enantiodiscrimination performances of enantiopure inherently chiral films obtained by electrooxidation of a thiahelicene monomer with helicoidal stereogenicity are presented for the first time. The outstanding potentialities of this novel approach are evaluated towards chiral probes with different chemical nature and bulkiness, in comparison with a representative case of the so far exploited class of inherently chiral selectors with axial stereogenicity. It is also verified that the high enantiodiscrimination ability holds as well for electron spins, as for atropisomeric selectors.

A donor/acceptor dyad was obtained by linking Nile Red and fullerene to a calix[4]arene scaffold. The dyad was spectroscopically characterized, both with steady-state and ultrafast transient absorption experiments, as well as with electrochemical and spectroelectrochemical techniques. We demonstrate extremely fast and efficient formation of a long-lived excited triplet localized on the fullerene moiety in this system, occurring in about 80 ps in toluene and 220 ps in chloroform. The mechanism of this process is investigated and discussed. The spectroscopic and electrochemical characterization suggests the occurrence of electron transfer from Nile Red to fullerene, leading to the formation of a charge-separated state. This state lives very briefly and, because of the small interaction between the electron donor and acceptor, promotes a singlet/triplet state mixing, inducing charge recombination and efficient triplet formation.

Electrochemiluminescence (ECL) is a powerful transduction technique that has rapidly gained importance as a powerful analytical technique. Since ECL is a surface-confined process, a comprehensive understanding of the generation of ECL signal at a nanometric distance from the electrode could lead to several highly promising applications. In this work, we explored the mechanism underlying ECL signal generation on the nanoscale using luminophore-reporter-modified DNA-based nanoswitches (i.e., molecular beacon) with different stem stabilities. ECL is generated according to the "oxidative-reduction" strategy using tri-n-propylamine (TPrA) as a coreactant and Ru(bpy)32+ as a luminophore. Our findings suggest that by tuning the stem stability of DNA nanoswitches we can activate different ECL mechanisms (direct and remote) and, under specific conditions, a "digital-like" association curve, i.e., with an extremely steep transition after the addition of increasing concentrations of DNA target, a large signal variation, and low preliminary analytical performance (LOD 22 nM for 1GC DNA-nanoswtich and 16 nM for 5GC DNA-nanoswitch). In particular, we were able to achieve higher signal gain (i.e., 10 times) with respect to the standard "signal-off" electrochemical readout. We demonstrated the copresence of two different ECL generation mechanisms on the nanoscale that open the way for the design of customized DNA devices for highly efficient dual-signal-output ratiometric-like ECL systems.

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure., A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene.

Electrochemiluminescence (ECL) is a powerful transduction technique with a leading role in the biosensing field due to its high sensitivity and low background signal. Although the intrinsic analytical strength of ECL depends critically on the overall efficiency of the mechanisms of its generation, studies aimed at enhancing the ECL signal have mostly focused on the investigation of materials, either luminophores or coreactants, while fundamental mechanistic studies are relatively scarce. Here, we discover an unexpected but highly efficient mechanistic path for ECL generation close to the electrode surface (signal enhancement, 128%) using an innovative combination of ECL imaging techniques and electrochemical mapping of radical generation. Our findings, which are also supported by quantum chemical calculations and spin trapping methods, led to the identification of a family of alternative branched amine coreactants, which raises the analytical strength of ECL well beyond that of present state-of-the-art immunoassays, thus creating potential ECL applications in ultrasensitive bioanalysis., Electrochemiluminescence (ECL) is a leading technique in biosensing. Here the authors identify an ECL generation mechanism near the electrode surface, which they exploit in combination with the use of branched amine coreactants to improve the ECL signal beyond the state-of-the-art immunoassays.

Electrochemiluminescence (ECL) is a leading technique in bioanalysis.[1] It is a luminescent phenomenon where the excited species are produced with an electrochemical stimulus rather than with a light excitation source. For this reason, ECL displays improved signal-to-noise ratio compared to photoluminescence, with minimized effects due to light scattering and luminescence background.[2] Chasing ever-increasing sensitivities, ECL can ideally be coupled to nanotechnology to develop new strategies for clinical applications and analyte determination also in real and complex matrices.[3] In particular, dye-doped silica nanoparticles (DDSNs) present many advantages: they can be easily synthesized, are hydrophilic and are prone to bioconjugation thanks to silica chemistry. With this approach we were able to achieve extremely bright systems and DDSNs allow the 8.5 fold increase of ECL intensity.[4] In DDSNs, light emission is influenced by the combination of several factors that make DDSNs complex multichromophoric structures. However, when ECL comes into play, the scenario is even more complicated due to the coreactant−NP interactions effect. Such complex scenario was approached at the theoretical level by developing suitable mechanistic models for ECL generation[5] while, at the same time, the influence of doping level on ECL efficiency was evaluated. Our results showed that the ECL intensity of a nanosized system cannot be merely incremented acting on doping, since other parameters come into play. These studies support the application in ECL microscopy providing valuable indications for the design of more efficient ECL nano- and micro-sized labels towards more sensitive ECL-based immunoassay for bioanalysis applications. [6] References [1] W. Miao, “Electrogenerated Chemiluminescence and Its Biorelated Applications”, Chem. Rev., 2008, vol. 108, pp. 2506–2553. [2] Z. Liu, W. Qi, G. Xu, “Recent advances in electrochemiluminescence”, Chem. Soc. Rev., 2015, vol. 44, pp. 3117–3142. [3] C. Ma, Y. Cao, X. Gou, J. J. Zhu, “Recent progress in electrochemiluminescence sensing and imaging”, Anal. Chem., 2015, vol. 92, pp. 431-454. [4] G. Valenti, E. Rampazzo, S. Bonacchi, L. Petrizza, M. Marcaccio, M. Montalti, L. Prodi, F. Paolucci, “Variable Doping Induces Mechanism Swapping in Electrogenerated Chemiluminescence of Ru(bpy) 3 2+ Core–Shell Silica Nanoparticles”, J. Am. Chem. Soc., 2016, vol. 138, pp. 15935–15942. [5] E. Daviddi, A. Oleinick, I. Svir, G. Valenti, F. Paolucci, C. Amatore, “Theory and Simulation for Optimising Electrogenerated Chemiluminescence from Tris(2,2′-bipyridine)-ruthenium(II)-Doped Silica Nanoparticles and Tripropylamine”, ChemElectroChem, 2017, vol. 4, pp. 1719–1730. [6] A. Zanut, F. Palomba, M. Rossi Scota, S. Rebeccani, M. Marcaccio, D. Genovese, E. Rampazzo, G. Valenti, F. Paolucci, L. Prodi, "Dye‐Doped Silica Nanoparticles for Enhanced ECL‐Based Immunoassay Analytical Performance", Angew. Chemie Int. Ed., 2020, vol. 132, pp. 22042-22047 Figure 1

Salophens and Salens are Schiff bases generated through the condensation of two equivalents of salicylaldehyde with either 1,2-phenylenediamines or aliphatic diamines, respectively. Both ligands have been extensively exploited as key building blocks in coordination chemistry and catalysis. In particular, their metal complexes have been widely used for various catalytical transformations with high yield and selectivity. Through the modification of the phenol unit it is possible to tune the steric hindrance and electronic properties of Salophen and Salen. The introduction of long aliphatic chains in salicylaldehydes can be used to promote their self-assembly into ordered supramolecular structures on solid surfaces. Herein, we report a novel method towards the facile synthesis of robust and air-stable [Al(Salophen)] derivatives capable of undergoing spontaneous self-assembly at the graphite/solution interface forming highly-ordered nanopatterns. The new synthetic approach relies on the use of [MeAlIII (Salophen)] as a building unit to introduce, via a simple acid/base reaction with functionalized acidic phenol derivatives, selected frameworks integrating multiple functions for efficient surface decoration. STM imaging at the solid/liquid interface made it possible to monitor the formation of ordered supramolecular structures. In addition, the redox properties of the Salophen derivatives functionalized with ferrocene units in solution and on surface were unraveled by cyclic voltammetry. The use of a five-coordinate aluminum alkyl Salophen precursor enables the tailoring of new Salophen molecules capable of undergoing controlled self-assembly on HOPG, and thereby it can be exploited to introduce multiple functionalities with subnanometer precision at surfaces, ultimately forming ordered functional patterns.

Targeted delivery of vitamins to a desirable area is an active branch in a modern pharmacology. The most important and difficult delivery of vitamin B

A donor acceptor dyad composed of a BF2-chelated dipyrromethene (BODIPY) and a C-60 fullerene has been newly synthesized and characterized. The two moieties are linked by direct addition of an azido substituted BODIPY on the C-60, producing an imino fullerene BODIPY adduct. The photoinduced charge transfer process in this system was studied by ultrafast transient absorption spectroscopy. Electron transfer toward the fullerene was found to occur selectively exciting both the BODIPY chromophore at 475 nm and the C-60 unit at 266 nm on a time scale of a few picoseconds, but the dynamics of charge separation was different in the two cases. Eletrochemical studies provided information on the redox potentials of the involved species and spectroelectrochemical measurements allowed to unambiguously assign the absorption band of the oxidized BODIPY moiety, which helped in the interpretation of the transient absorption spectra. The experimental studies were complemented by a theoretical analysis based on DFT computations of the excited state energies of the two components and their electronic couplings, which allowed identification of the charge transfer mechanism and rationalization of the different kinetic behavior observed by changing the excitation conditions.

Tuning the intermolecular interactions among suitably designed molecules forming highly ordered self-assembled monolayers is a viable approach to control their organization at the supramolecular level. Such a tuning is particularly important when applied to sophisticated molecules combining functional units which possess specific electronic properties, such as electron/energy transfer, in order to develop multifunctional systems. Here we have synthesized two tetraferrocene-porphyrin derivatives that by design can selectively self-assemble at the graphite/liquid interface into either face-on or edge-on monolayer-thick architectures. The former supramolecular arrangement consists of two-dimensional planar networks based on hydrogen bonding among adjacent molecules whereas the latter relies on columnar assembly generated through intermolecular van der Waals interactions. Scanning Tunneling Microscopy (STM) at the solid-liquid interface has been corroborated by cyclic voltammetry measurements and assessed by theoretical calculations to gain multiscale insight into the arrangement of the molecule with respect to the basal plane of the surface. The STM analysis allowed the visualization of these assemblies with a sub-nanometer resolution, and cyclic voltammetry measurements provided direct evidence of the interactions of porphyrin and ferrocene with the graphite surface and offered also insight into the dynamics within the face-on and edge-on assemblies. The experimental findings were supported by theoretical calculations to shed light on the electronic and other physical properties of both assemblies. The capability to engineer the functional nanopatterns through self-assembly of porphyrins containing ferrocene units is a key step toward the bottom-up construction of multifunctional molecular nanostructures and nanodevices.

The coupling of nanomaterials, and nanoparticles in particular, with one of the most powerful transduction techniques, electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical reactions at electrodes, has recently provided sensing tools with unprecedented sensitivity limits. This review aims to give an overview of the state of the art in the field over the last 5 years, i.e., a time span covering over 80% of the scientific production in this context. The results herein discussed would demonstrate that the use of nanoparticles in the ECL technique represents one of the most interesting research lines for the development of ultrasensitive analytical tools, offering an insight to recognize and select the best nanomaterials for ECL signal amplification, with particular emphasis in biosensing. (C) 2018 Elsevier B.V. All rights reserved.

Molecular and electronic structure, reduction electron transfer and coordination abilities of a polycyclic aromatic hydrocarbon (PAH) having a planar naphtho-group fused to the corannulene bowl have been investigated for the first time using a combination of theoretical and experimental tools. A direct comparison of naphtho[2,3-a]corannulene (C28 H14 , 1) with parent corannulene (C20 H10 , 2) revealed the effect of framework topology change on electronic properties and aromaticity of 1. The presence of two reduction steps for 1 was predicted theoretically and confirmed experimentally. Two reversible one-electron reduction processes with the formal reduction potentials at -2.30 and -2.77 V versus Fc+/0 were detected by cyclic voltammetry (CV) measurements, demonstrating accessibility of the corresponding mono- and dianionic states of 1. The products of the singly and doubly reduced napththocorannulene were prepared using chemical reduction with Group 1 metals and isolated as sodium and rubidium salts. Their X-ray diffraction study revealed the formation of "naked" mono- and dianions crystallized as solvent-separated ion products with one or two sodium cations as [Na+ (18-crown-6)(THF)2 ][C28 H14- ] and [Na+ (18-crown-6)(THF)2 ]2 [C28 H142- ] (3⋅THF and 4⋅THF, respectively). The dianion of 1 was also isolated as a contact-ion complex with two rubidium countercations, [{Rb+ (18-crown-6)}2 (C28 H142- )] (5⋅THF). The structural consequences of adding one and two electrons to the carbon framework of 1 are compared for 3, 4 and 5. Changes in aromaticity and charge distribution stemming from the stepwise electron acquisition are discussed based on DFT computational study.

The electrogenerated chemiluminescence (ECL) properties of two neutral cyclometalated Ir(III) complexes, Ir(iqbt)2dpm (1) and its parent complex fac-Ir(iqbt)3 (2) [iqbt=1-(benzo[b]thiophen-2-yl)-isoquinolinate], have been investigated in acetonitrile solution. Complexes 1 and 2 display near-infrared (near-IR) ECL emission in acetonitrile with maxima at 712 and 706 nm, respectively. Species 1 and 2 showed a strong increase in ECL intensity upon employing benzoyl peroxide (BPO) as a co-reactant with respect to the annihilation. The remarkable continuous ECL emission in near-IR region makes these complexes promising candidates for development of near-IR-emitting Ir-based labels in diagnostics. Furthermore, encapsulation of complex 1 within silica-PEG nanoparticles was successfully obtained: the resulting 1@NPs are easily solubilized in aqueous media where remarkable ECL emission was observed even in aerated conditions.

In the last few years, hydrogen peroxide [...]

Correction for ‘Liponitroxides: EPR study and their efficacy as antioxidants in lipid membranes’ by Giovanna Mobbili et al., RSC Adv., 2015, 5, 98955–98966.

Considering the depletion of fossil-fuel reserves and their negative environmental impact, new energy schemes must point towards alternative ecological processes. Efficient hydrogen evolution from water is one promising route towards a renewable energy economy and sustainable development. Here we show a tridimensional electrocatalytic interface, featuring a hierarchical, co-axial arrangement of a palladium/titanium dioxide layer on functionalized multi-walled carbon nanotubes. The resulting morphology leads to a merging of the conductive nanocarbon core with the active inorganic phase. A mechanistic synergy is envisioned by a cascade of catalytic events promoting water dissociation, hydride formation and hydrogen evolution. The nanohybrid exhibits a performance exceeding that of state-of-the-art electrocatalysts (turnover frequency of 15000 H2 per hour at 50 mV overpotential). The Tafel slope of ∼130 mV per decade points to a rate-determining step comprised of water dissociation and formation of hydride. Comparative activities of the isolated components or their physical mixtures demonstrate that the good performance evolves from the synergistic hierarchical structure., Hydrogen evolution by water electrolysis is a promising route to 'green energy', but efficiency is still an issue. Here, the authors make mixed organic/inorganic hierarchical nanostructures with high hydrogen evolution activity, identifying synergic effects in the material contributing to enhanced efficiency.

The impact of nanotechnology on analytical science is hardly overlooked. In the search for ever-increasing sensitivity in biomedical sensors, nanoparticles have been playing a unique role as, for instance, ultrabright labels, and unravelling the intimate mechanisms which govern their functioning is mandatory for the design of ultrasentitive devices. Herein, we investigated the mechanism of electrogenerated chemiluminescence (ECL) in a family of core-shell silica-PEG nanoparticles (DDSNs), variously doped with a Ru(bpy)32+ triethoxysilane derivative, and displaying homogeneous morphological, hydrodynamic, and photophysical properties. ECL experiments, performed in the presence of 2-(dibutylamino)ethanol (DBAE) as coreactant, showed two parallel mechanisms of ECL generation: one mechanism (I) which involves exclusively the radicals deriving from the coreactant oxidation and a second one (II) involving also the direct anodic oxidation of the Ru(II) moieties. The latter mechanism includes electron (hole) hopping between neighboring redox centers as evidenced in our previous studies and supported by a theoretical model we have recently proposed. Quite unexpectedly, however, we found that the efficiency of the two mechanisms varies in opposite directions within the DDSNs series, with mechanism I or mechanism II prevailing at low and high doping levels, respectively. Since mechanism II has an intrinsically lower efficiency, the ECL emission intensity was also found to grow linearly with doping only at relatively low doping levels while it deviates negatively at higher ones. As the ?-potential of DDSNs increases with the doping level from negative to slightly positive values, as a likely consequence of the accumulating cationic charge within the silica core, we attributed the observed change in the ECL generation mechanism along the DDSN series to a modulation of the electrostatic and hydrophobic/hydrophilic interactions between the DDSNs and the radical cationic species involved in the ECL generation. The results we report therefore show that the ECL intensity of a nanosized system cannot be merely incremented acting on doping, since other parameters come into play. We think that these results could serve as valuable indications to design more efficient ECL nano- and microsized labels for ultrasensitive bioanalysis.

The photophysical and electrochemical properties of a novel metallopolymer containing [Re(bpy)(CO)3]+ moieties coordinated to a poly(4-vinylpyridine) polymer chain are reported. Significantly, the release of the metal complexes can be triggered by oxidation or reduction of the rhenium complex. Solvent rapidly binds to the vacant coordination site to give a luminescent product. The redox and photophysical properties of the parent metallopolymer and the released solvated complex are compared. Along with photoemission, the metallopolymer generates significant electrogenerated chemiluminescence upon reduction in the presence of benzoyl peroxide as coreactant.

6 pages; International audience; We present a resonance Raman study of electrochemical charge transfer doping on polyelectrolyte single-walled carbon nanotubes (SWNTs) in solution. Changes in the intensity of the radial breathing modes of well-identified SWNTs are measured as a function of the electrochemical potential. The intensity is maximum when the nanotubes are neutral. Unexpectedly, the Raman signal decreases as soon as charges are transferred to the nanotubes, leading to intensity profiles that are triangular for metallic and trapezoidal for semiconducting nanotubes. A key result is that the width in energy of the plateaus for the semiconducting nanotubes is roughly equal to the optical gap (rather than the free carrier gap). While these experiments can be used to estimate the energy levels of individual nanotubes, strong dynamical screening appears to dominate in individual SWNT polyelectrolytes so that only screened energy levels are being probed.

The dissociation process of neutral open-shell [4-F-(C(6)H(4))-I-C≡C-(CH(2))(4)-Cl] and [4-NO(2)-(C(6)H(4))-I-C≡C-(CH(2))(4)-Cl] asymmetric iodonium radicals was studied theoretically. Vertical electron affinities and DRC (dynamic reaction coordinate) results were obtained and compared with experimental evidence. In particular, the fluorine and nitro substituent groups were selected because of (i) their opposite electron-withdrawing/electron-donating effects and (ii) experimental evidence that the grafting ability, in terms of alkynyl/aryl grafting ratio, increases with decreasing electron-withdrawing nature of the para-position substituent on the phenyl ring. DRC results show that the dissociation dynamics of the iodine-alkynyl carbon bond, for the nitro-substituted iodonium, occurs on a longer time scale than that of the fluorine-substituted iodonium. This finding is in agreement with the overall experimental results.

The charge-transfer and spectral properties of two octithiophenes, namely 4',4''',3'(v),3(v)'-tetra(octylsulfanyl)-2,2':5',2'':5'',2''':5''',2'(v):5'(v),2(v):5(v),2(v)':5(v)',2(v)''-octithiophene and 4,3'',4(v),4(v)''-tetrabromo-4',4''',3'(v),3(v)'-tetra[(R)-2-methylbutylsulfanyl]-2,2':5',2'':5'',2''':5''',2'(v):5'(v),2(v):5(v),2(v)':5(v)',2(v)''-octithiophene, OT1 and OT2, respectively, are characterized by cyclic voltammetry and spectroelectrochemistry under ultradry conditions. The analysis of the voltammetric results shows the formation of up to the dication for both OT1 and OT2 and up to the tetraanion (OT1) and trianion (OT2) anions. The optical properties of the OT1 (2+, 1+, neutral, 1-, 2-) species were probed by in situ UV-vis-NIR spectroelectrochemistry. The calculated standard potentials at the B3LYP/cc-pVTZ level of the theory allowed the rationalization of the experimental electrochemical results. The UV-vis-NIR spectra were successfully compared with the theoretical electronic transitions and oscillator strength data obtained by time-dependent B3LYP/6-31G* calculations. Theoretical redox potentials and optical transitions properties are calculated including "the solvent effect" within the CPCM model. The consistency obtained between experimental and theoretical results indicates the existence of the hypothesized high-spin/high-charge p- and n-doped electronic states for the OT1 and OT2 octithiophenes here studied.

In this work, the electrochemical and ECL properties of tris[1,10-phenanthrolinediyl-4,7-di(benzenesulfonate)]Ru(II) ([Ru(BPS)3]4-) have been addressed in both strictly aprotic conditions and aqueous buffers. A combined theoretical and experimental approach is presented to focus thermodynamics and kinetic effects of electro-generated species possessing highly negative charge. The complex, prepared as the sodium salt by using a newly developed procedure, was subsequently converted to the tetrabutylammonium salt by ion exchange, thus making it soluble in organic media and allowing, for the first time, its thorough electrochemical investigation in ultra-dry aprotic media. The electrochemically induced luminescence (ECL) of Na 4[Ru(BPS)3] in phosphate buffer, using the co-reactant method (tripropylamine), was investigated as a function of the electrode material and halide addition, and ECL intensities six times higher than that of [Ru(bpy)3]2+ were found. In addition, the ECL behavior of this promising dye for biomolecule recognition was investigated in aprotic media and, for the first time, the direct radical anion-radical cation annihilation ECL was obtained.

Although the desirability of developing synthetic molecular machine systems that can function on surfaces is widely recognized, to date the only well-characterized examples of electrochemically switchable rotaxane-based molecular shuttles which can do so are based on the tetracationic viologen macrocycle pioneered by Stoddart. Here, we report on a [2]rotaxane which features succinamide and naphthalene diimide hydrogen-bonding stations for a benzylic amide macrocycle that can shuttle and switch its net position both in solution and in a monolayer. Three oxidation states of the naphthalene diimide unit can be accessed electrochemically in solution, each one with a different binding affinity for the macrocycle and, hence, corresponding to a different distribution of the rings between the two stations in the molecular shuttle. Cyclic voltammetry experiments show the switching to be both reversible and cyclable and allow quantification of the translational isomer ratios (thermodynamics) and shuttling dynamics (kinetics) for their interconversion in each state. Overall, the binding affinity of the naphthalene diimide station can be changed by 6 orders of magnitude over the three states. Unlike previous electrochemically active amide-based molecular shuttles, the reduction potential of the naphthalene diimide unit is sufficiently positive (−0.68 V) for the process to be compatible with operation in self-assembled monolayers on gold. Incorporating pyridine units into the macrocycle allowed attachment of the shuttles to an acid-terminated self-assembled monolayer of alkane thiols on gold. The molecular shuttle monolayers were characterized by X-ray photoelectron spectroscopy and their electrochemical behavior probed by electrochemical impedance spectroscopy and double-potential step chronoamperometry, which demonstrated that the redox-switched shuttling was maintained in this environment, occurring on the millisecond time scale.

Monitoring Prostate Cancer (PCa) biomarkers is an efficient way to diagnosis this disease early, since it improves the therapeutic success rate and suppresses PCa patient mortality: for this reason a powerful analytical technique such as electrochemiluminescence (ECL) is already used for this application, but its widespread usability is still hampered by the high cost of commercial ECL equipment. We describe an innovative approach for the selective and sensitive detection of the PCa biomarker sarcosine, obtained by a synergistic ECL-supramolecular approach, in which the free base form of sarcosine acts as co-reagent in a Ru(bpy)32+-ECL process. We used magnetic micro-beads decorated with a supramolecular tetraphosphonate cavitand (Tiiii) for the selective capture of sarcosine hydrochloride in a complex matrix like urine. Sarcosine determination was then obtained with ECL measurements thanks to the complexation properties of Tiiii, with a protocol involving simple pH changes – to drive the capture–release process of sarcosine from the receptor – and magnetic micro-bead technology. With this approach we were able to measure sarcosine in the μM to mM window, a concentration range that encompasses the diagnostic urinary value of sarcosine in healthy subjects and PCa patients, respectively. These results indicate how this ECL-supramolecular approach is extremely promising for the detection of sarcosine and for PCa diagnosis and monitoring, and for the development of portable and more affordable devices.

A series of lipid-functionalized nitroxides having a pyrroline nitroxide moiety linked either to a glycerol or to a steroid unit has been synthesized, and their inclusion inside phospholipid bilayers has been investigated by Electron Paramagnetic Resonance (EPR) spectroscopy. The antioxidant behavior of these nitroxides has been studied in azo-initiator induced lipid peroxidation by means of the Thiobarbituric Acid Reactive Species (TBARS) assay; a correlation with their penetration depth within the bilayer has been found. The possible mechanisms involved in the antioxidant action have been considered, discussed and alternative pathways have been suggested for the synthesized liponitroxides due to their different localization. The steroid derivative is limited to scavenging radicals that are generated in the aqueous phase, while the glycerolipids can also act as chain breaking antioxidants.

Graphene-metal composites have potential as novel catalysts due to their unique electrical properties. Here, we report the synthesis of a composite material comprised of monodispersed platinum nanoparticles on high-quality graphene obtained by using two different exfoliation techniques. The material, prepared via an easy, low-cost and reproducible procedure, was evaluated as an electrocatalyst for the hydrogen evolution reaction. The turnover frequency at zero overpotential (TOF0 in 0.1 m phosphate buffer, pH 6.8) was determined to be approximately 4600 h-1. This remarkably high value is likely due to the optimal dispersion of the platinum nanoparticles on the graphene substrate, which enables the material to be loaded with only very small amounts of the noble metal (i.e., Pt) despite the very highly active surface. This study provides a new outlook on the design of novel materials for the development of robust and scalable water-splitting devices.

In this work, we report the results about the solution and solid-state phosphorescence emission properties of six Ru(II) complexes containing various 5-substituted tetrazolate ligands. The photo- and electrochemiluminescence spectra of all compounds revealed a red shifted emission with respect to the Ru(bpy)(3)(2+). Significant changes to the light emission energy and to the efficiency and sensitivity to oxygen were also determined by varying the nature of the substituent ring of the tetrazolate ligand. Light-emitting solid devices with active layers containing solid films of the same complexes were prepared, and preliminary studies of their electroinduced emission properties were performed. The electrochemiluminescence (ECL) emission intensity of two of the six complexes was of the same order of magnitude as the reference Ru(bpy)(3)(2+).

The preparation and characterization of a solvent-switchable rotaxane that shuttles in the opposite direction to that expected are reported. The reverse shuttling is confirmed by NMR spectroscopy and can be monitored by cyclic voltammetry. The electrochemically generated anions on the fullerene moiety are stabilized by the closer proximity of the macrocycle.

The bimetallic complexes [L 2 Ir{C 5 H 4 CH 2 (9,10-anthrylene)CH 2 C 5 H 4 }IrL 2 ] ( 3 ) (L = η 2 -C 2 H 4 ) and ( 4 ) (L = CO) were obtained by reacting the thallium(I) derivative of 9,10-bis(cyclopentadienylmethyl)-anthracene ( 1 ), i.e. [Tl{C 5 H 4 CH 2 (9,10-anthrylene)CH 2 C 5 H 4 }Tl] ( 2 ), with [IrCl(η 2 -C 2 H 4 ) 4 ] and [IrCl(C 5 H 5 N)(CO) 2 ], respectively, and characterized by elemental analysis, MS, 1 H NMR, UV–Vis (290–490 nm) spectroscopy, and FT-IR. When excited at wavelengths ranging from 333 to 383 nm, 1 results to be fluorescent, while 3 and 4 show the almost complete quenching of the anthrylene fluorescence. The electrochemical behaviour of 3 and 4 has been studied and compared with that of the monometallic complexes, i.e. (η 5 -9-anthrylmethylcyclopentadienyl)-bis(η 2 -ethylene)iridium(I) ( 5 ), whose preparation and X-ray structure are reported here, and the already described (η 5 -9-anthrylmethylcyclopentadienyl)dicarbonyliridium(I) ( 6 ). The study allows the interpretation of the electrode processes and gives information about the location of the redox sites along with the thermodynamic characterization of the redox processes. On this basis, the intramolecular charge-transfer process between the photo-excited anthrylenic moiety and one cyclopentadienylIrL 2 unit is suggested to be a possible route for the quenching of the anthrylene fluorescence. The oxidation of 3 and 4 by [bis(trifluoroacetoxy)iodo]benzene (PIFA) and thallium(III) trifluoroacetate (TTFA), respectively, produces the radical cations 3 + and 4 + , which, on the base of their EPR spectra, are described as average-valence [Ir +1.5 , Ir +1.5 ] species. DFT calculations of spin density distribution confirm the EPR results and allow a further insight into the structure of such radicals. Differences and analogies lying between the electronic and conformational structure of the bimetallic, 3 + and 4 + , and the monometallic, 5 + and 6 + , cation radicals are discussed by comparing the EPR spectra and the spin density distribution maps.

Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and digital simulation techniques were used to investigate quantitatively the mechanism of electron transfer (ET) through densely packed and well-ordered self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid on gold, either pristine or modified by physically adsorbed glucose oxidase (GOx). In the presence of ferrocenylmethanol (FcMeOH) as a redox mediator, ET kinetics involving either solution-phase hydrophilic redox probes such as [Fe(CN)(6)](3-/4-) or surface-immobilized GOx is greatly accelerated: [Fe(CN)(6)](3-/4-) undergoes diffusion-controlled ET, while the enzymatic electrochemical conversion of glucose to gluconolactone is efficiently sustained by FcMeOH. Analysis of the results, also including the digital simulation of CV and EIS data, showed the prevalence of an ET mechanism according to the so-called membrane model that comprises the permeation of the redox mediator within the SAM and the intermolecular ET to the redox probe located outside the monolayer. The analysis of the catalytic current generated at the GOx/SAM electrode in the presence of glucose and FcMeOH allowed the high surface protein coverage suggested by X-ray photoelectron spectroscopy (XPS) measurements to be confirmed.