Tuning the dipolar second-order nonlinear optical properties of 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes, related cyclometallated platinum(ii) complexes and methylated salts.

The synthesis and characterization of three 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes is reported along with that of their related cyclometallated platinum(ii) complexes and N,N-dimethylated iodide salts. The second-order nonlinear optical (NLO) properties of all the compounds have been determined by the Electric Field Induced Second Harmonic generation technique, showing how the µßEFISH absolute value of 1,3-di(2-pyridyl)benzenes can be tuned by the nature of the substituent on position 5 of the central benzene ring, and greatly increased by cyclometallation to Pt or by N-methylation.

A 2D semiconductor-self-assembled monolayer photoswitchable diode.

A switchable diode in a 2D semiconductor-molecular junction heterostructure is reported. MoS2 is exfoliated on top of a monolayer of azobenzene-substituted thiols on gold. Photoisomerization of the azobenzenes results in switching between a rectifier with rectifying ratios of 10(4) and a conductive state, as revealed by conducting atomic force microscopy.

Neutral N

An emerging field regarding N^C^N terdentate Pt(II) complexes is their application as luminescent labels for bio-imaging. In fact, phosphorescent Pt complexes possess many advantages such as a wide emission color tunability, a better stability towards photo- and chemical degradation, a very large Stokes shift, and long-lived luminescent excited states with lifetimes typically two to three orders of magnitude longer than those of classic organic fluorophores. Here, we describe the synthesis and photophysical characterization of three new neutral N^C^N terdentate cyclometallated Pt complexes as long-lived bio-imaging probes. The novel molecular probes bear hydrophilic (oligo-)ethyleneglycol chains of various lengths to increase their water solubility and bio-compatibility and to impart amphiphilic nature to the molecules. The complexes are characterized by a high cell permeability and a low cytotoxicity, with an internalization kinetics that depends on both the length of the ethyleneglycol chain and the ancillary ligand.

Unexpectedly high second-order nonlinear optical properties of simple Ru and Pt alkynyl complexes as an analytical springboard for NLO-active polymer films.

The unexpectedly high quadratic hyperpolarizability values of simple Ru and Pt alkynyl complexes have been measured by the EFISH technique, and this prompted us to investigate their potential as molecular building blocks for composite films with second harmonic generation properties.

An acido-triggered reversible luminescent and nonlinear optical switch based on a substituted styrylpyridine: EFISH measurements as an unusual method to reveal a protonation-deprotonation NLO contrast.

Diphenyl-(4-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-phenyl)-amine (DPVPA) constitutes a novel acido-triggered reversible luminescent and nonlinear optical switch. Remarkably, for the first time the Electric-Field Induced Second Harmonic generation (EFISH) technique is used to reveal a protonation-deprotonation NLO contrast.

Thiocyanate-free ruthenium(II) sensitizer with a pyrid-2-yltetrazolate ligand for dye-sensitized solar cells.

The synthesis of the new complex [Ru(Tetrazpy)(dcbpy)2]Cl is reported, along with its spectroscopical, electrochemical, and theoretical characterization. The first dye-sensitized solar cell device with this complex has been prepared, leading to a 3% of conversion efficiency, promising data considering the simplicity of the Tetrazpy ligand.

A facile synthesis of α-N-ribosyl-asparagine and α-N-ribosyl-glutamine building blocks.

Adenosine diphosphate ribosylation (ADP-ribosylation) is a widely occurring post-translational modification of proteins at nucleophilic side chain of amino acid residues. Elucidation of ADP-ribosylation events would benefit greatly from the availability of well-defined ADP-ribosylated peptides and analogues thereof. In this paper we present a novel approach to the chemical synthesis of ribosylated amino acid building blocks using traceless Staudinger ligation. We describe an efficient and stereoselective synthesis of α-N-ribosyl-asparagine (α-N-ribosyl-Asn) and α-N-ribosyl-glutamine (α-N-ribosyl-Gln) building blocks starting from 5-tert-butyldiphenylsilyl-ß-D-ribofuranosyl azide. The N-glycosyl aminoacids are produced in good yields as pure α-anomers, suitably protected for peptide synthesis.

Stereoselective synthesis of α- and ß-glycofuranosyl amides by traceless ligation of glycofuranosyl azides.

A highly stereoselective synthesis of α- or ß-glycofuranosyl amides based on the traceless Staudinger ligation of glycofuranosyl azides of the galacto, ribo, and arabino series with 2-diphenylphosphanyl-phenyl esters has been developed. Both α- and ß-isomers can be obtained with excellent selectivity from a common, easily available precursor. The process does not depend on the anomeric configuration of the starting azide but appears to be controlled by the C2 configuration and by the protection/deprotection state of the substrates. A mechanistic interpretation of the results, supported by (31)P NMR experiments, is offered and merged with our previous mechanistic analysis of pyranosyl azide ligation reactions.

Stereoselective synthesis of N-galactofuranosyl amides.

α- or ß-Galactofuranosyl (Galf) amides can be synthesized with high stereoselectivity by traceless Staudinger ligation starting from unprotected ß-galactofuranosyl azide or tetra-O-acetyl-ß-galactofuranosyl azide, respectively. The resulting Galf amides are hitherto unknown molecules, with interesting potential as inhibitors of mycobacterial growth.

Stereoselective synthesis of glycosyl amides by traceless Staudinger ligation of unprotected glycosyl azides.

The stereoconservative Staudinger ligation of unprotected alpha- and beta-glucosyl azides with diphenylphosphanyl-phenyl esters to afford alpha- and beta-glucosyl amides is described.