Au25(SR)18 (R = −CH2–CH2–Ph) is a molecule-like nanocluster displaying distinct electrochemical and optical features. Although it often taken as an example of particularly well-understood cluster, very recent literature has provided quite unclear or even controversial description its properties. We prepared monodisperse Au25(SR)180 studied by cyclic voltammetry, under controlled conditions, the kinetics reduction oxidation to series charge states, −2, −1, +1, +2, +3. For each electrode...

Au25(SR)18 has provided fundamental insights into the properties of clusters protected by monolayers thiolated ligands (SR). Because its ultrasmall core, 1 nm, displays molecular behavior. We prepared a Au25 cluster capped n-butanethiolates (SBu), obtained structure single-crystal X-ray crystallography, and studied both experimentally theoretically. Whereas in solution Au25(SBu)18(0) is paramagnetic molecule, crystal it becomes linear polymer connected via single Au-Au bonds stabilized...

X-ray crystallography has been fundamental in discovering fine structural features of ultrasmall gold clusters capped by thiolated ligands. For still unknown structures, however, new tools capable providing relevant information are sought. We prepared a 25-gold atom nanocluster protected the smallest ligand ever used, ethanethiol. This cluster displays electrochemistry, mass spectrometry, and UV-vis absorption spectroscopy similar Au25 18 The anionic neutral form Au25(SEt)18 were fully...

ConspectusAtomically precise gold nanoclusters display properties that are unseen in larger nanoparticles. When the number of atoms is sufficiently small, clusters exhibit molecular properties. Their study requires extensive use classic physical chemistry and, thus, methods such as vibrational spectroscopies, electrochemistry, density functional theory and dynamics calculations, course nuclear magnetic resonance (NMR) electron paramagnetic (EPR) spectroscopies. NMR EPR studies have been...

Several research groups have observed magnetism in monolayer-protected gold cluster samples, but the results were often contradictory, and thus, a clear understanding of this phenomenon is still missing. We used Au25(SCH2CH2Ph)180, which paramagnetic that can be prepared with atomic precision whose structure known precisely. Previous magnetometry studies only detected paramagnetism. samples representing range crystallographic orders studied their magnetic behaviors using electron resonance...

Photoprocesses associated with the complexation of a pyridine-functionalized C60 fullerene derivative to ruthenium- and zinc-tetraphenylporphyrins (tpp) have been studied by time-resolved optical transient EPR spectroscopies. It has found that upon irradiation in toluene, highly efficient triplet-triplet energy transfer governs deactivation photoexcited [Ru(tpp)], while electron (ET) from porphyrin prevails polar solvents. Complexation [Zn(tpp)] is reversible and, following excitation...

The interconversion of the two allotropes hydrogen molecule (para-H2 and ortho-H2) incarcerated inside fullerene C60 is reported (oH2@C60 pH2@C60, respectively). For conversion, oH2@C60 was adsorbed at external surface zeolite NaY immersed into liquid oxygen 77 K. Equilibrium reached in less than 0.5 h. Rapid removal provides a sample enriched pH2@C60 that stable for many days absence paramagnetic catalysts (half-life approximately 15 days). Enriched nonvolatile soluble organic solvents. At...

Singlet oxygen,

T. Da Ros, M. Prato, D. Guldi, E. Alessio, Ruzzi and L. Pasimeni, Chem. Commun., 1999, 635 DOI: 10.1039/A900645A

The modulation induced by different solvents and pH on the nitrogen isotropic hyperfine coupling constants (AN) of 2,2,5,5-tetramethyl-3-carboxypyrrolidine (3-carboxy-PROXYL,CP) 2,2,6,6-tetramethyl-4-carboxypiperidine (4-carboxy-TEMPO,CT) nitroxides is studied through ab initio quantum mechanical computations EPR spectroscopy. geometry neutral deprotonated forms corresponding dissociation are computed using hybrid PBE0 functional. With these structures, accurate AN values obtained an...

The 1H nuclear spin-lattice relaxation time (T1) of H2 and H2@C60 in organic solvents varies with solvent, it proportionally for H2@C60. Since intermolecular magnetic interactions are ruled out, the solvent must influence modulating processes mechanisms both cage inside C60. temperature dependence T1 also is very similar H2@C60, going through a maximum by varying which allow wide range temperatures to be explored. This behavior attributed presence dipolar spin-rotation have an opposite on...

Dispersion-corrected density functional theory (DFT-D) calculations, Electron Spin Resonance spectroscopy (EPR), and variable temperature magnetic moment measurements were used to investigate the structure electronic/magnetic properties of bispyrazolato-copper(II) coordination polymer its hydration product. The Cu(II) ions are antiferromagnetically coupled through sigma system pyrazolate rings in both compounds. Theoretical electron maps reveal that water molecules interact simultaneously a...

We studied by means of electron spin resonance (EPR) techniques the photoinduced processes in a poly[(9,9-bis(octyl)fluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl) (F8BT) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61 (PCBM) blend. Using light-induced EPR (LEPR), we observed generation charge-separated states blend upon visible light excitation, detected formation PCBM excited triplet state using time-resolved (TREPR) with microsecond time resolution. From spectral simulation...

We prepared four structurally related paramagnetic Au₂₅(SR)018 clusters.¹H ENDOR and NMR signals could be successfully to the types of ligand distance protons from central gold core. It is shown that unpaired electron can used as a very precise probe structure interface between metal core capping ligands.

X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T 293-323 K. was produced by quenching photogenerated sensitizers naphthalene C8H10, perdeuterated naphthalene, perfluoronaphthalene phase. The spectrum also microwave discharge. Integrated intensities line widths individual components used as internal standards for estimating concentration O2 species cavity. Time-resolved (TR)...

We synthesized two series of compounds in which a nitroxide radical and fullerene C(60) moiety were kept separated by 3(10)-helical peptide bridge containing intramolecular C═O···H-N hydrogen bonds. The direction the resulting molecular dipole moment could be reversed switching position with respect to nitrogen carbon termini. fullerene-peptide-radical systems compared behaviors otherwise identical peptides but lacking either or free moiety. Electrochemical analysis chemical reduction...

We have measured the bimolecular contribution (relaxivity) R1 (M(-1) s(-1)) to spin-lattice relaxation rate for protons of H2 and H2@C60 dissolved in organic solvents presence paramagnet nitroxide radicals. It is found that effect paramagnets enhanced 5-fold compared under same conditions. 13C relaxivity C60 induced by has also been measured. The resulting value substantially smaller relative 1H than expected solely on basis magnetic moment 13C. observed values analyzed quantitatively using...

The self-aggregation process of five alkyltrimethylammonium bromide surfactants [CH3(CH2)n−1N(CH3)3Br (n = 6,8,10,12,16), CnTAB] in aqueous solution at pH 7 has been studied by electron paramagnetic resonance (EPR) spectroscopy employing 3-carboxy-PROXYL its deprotonated form [2,2,5,5-tetramethyl-3-carboxypyrrolidinyloxy sodium salt, CP−] as a spin probe. In all the considered systems, nitrogen isotropic hyperfine coupling constant CP−, 〈AN〉, decreases and correlation time, τC, increases...

A power conversion efficiency of 0.37%, under white light 80 mW cm-2 intensity, was obtained when a fullerene-azothiophene dyad used as the active layer photovoltaic cell.

The quenching rate constants of singlet oxygen by C60, H2@C60, D2@C6o, H2, and D2 in solution were measured. presence a hydrogen (H2@C60) or deuterium (D2@C60) molecule inside the fullerene did not produce any observable effect based on triplet lifetime EPR measurements. However, remarkable was found for 1O2 D2. Singlet generated photosensitization thermal decomposition naphthalene endoperoxide derivatives. Comparison H2@C60 D2@C60 demonstrates significant vibrational interaction between H2...

Interpenetrating networks of polythiophenes and fullerene derivatives give rise to charge transfer after irradiation with visible light. The resulting radical ion pairs have been studied by time-resolved EPR spectroscopy. At low temperatures (20 K), the are spin correlated locked at a distance 27.1 Å, whereas an increase temperature causes electron hole move further away from each other.