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Guarnaccio A.,CNR Institute of Structure of Matter | D'Auria M.,UniversitaI della Basilicata | Racioppi R.,UniversitaI della Basilicata | Mattioli G.,CNR Institute of Structure of Matter | And 7 more authors.
Journal of Physical Chemistry C | Year: 2016

A comparative study of DTBT (1,3-di(thiophen-2-yl)benzo[c]thiophene), Br-DTBT-Br (1,3-bis(4,5-dibromothiophen-2-yl)benzo[c]thiophene), and a model 3T (2,2′:5′,2-terthiophene) oligothiophenes has been performed by investigating the interactions occurring between these compounds and both polycrystalline and single-crystal Ag surfaces. As a main result we report that the interaction of 3T with the Ag surfaces is followed by a fast, low-temperature polymerization. On the contrary, DTBT-like compounds, less reactive at low temperature, undergo thermally activated dissociation processes which hinder the possibility of a surface-induced polymerization of such compounds as a suitable synthetic strategy. Our results are supported by Raman and surface-enhanced Raman spectroscopy (SERS) measurements of the molecules in contact with a polycrystalline Ag substrate, showing the fingerprint of polythiophene chains in the case of 3T and a characteristic S-S stretching signal compatible with ring-opening processes in the case of DTBT-like compounds, not detected for 3T. Moreover, high-resolution X-ray photoelectron spectroscopy (XPS) measurements, probing carbon 1s and sulfur 2p core levels of the same molecules deposited onto a Ag(110) single crystal, confirm the suggestion of a ring-opening process by a C-S bond cleavage induced by both the interaction with silver and thermal treatments. Near-edge X-ray absorption fine structure (NEXAFS) carbon K-edge measurements complete the information, showing a common tendency of the molecules to lay flat on the Ag surface. Finally, density functional theory (DFT) calculations have been carried out to investigate the interaction and molecular conformation/orientation at the 3T and DTBT/Ag(110) interfaces. Theoretical findings support the results of measurements and suggest that a fine interplay between structural and electronic modifications of the benzo-fused rings of DTBT-like compounds in contact with the Ag surface is responsible for the peculiar reactivity of such molecules. © 2015 American Chemical Society.

Santoro S.,Universitai Of Perugia | Santoro S.,University of Stockholm | Superchi S.,UniversitaI della Basilicata | Messina F.,Universitai Of Perugia | And 4 more authors.
Journal of Natural Products | Year: 2013

Agarsenone (1), a new cadinane sesquiterpenoid, was isolated from the resin of Commiphora erythraea. The structures of 1 and its decomposition products agarsenolides (2a and 2b) and myrrhone (3) were established by extensive NMR spectroscopic analysis. The absolute configuration of 3 and the relative and absolute configurations of 1 were assigned by comparison of experimental and calculated optical rotatory dispersion and electronic circular dichroism spectra. © 2013 The American Chemical Society and American Society of Pharmacognosy.

Manet I.,National Research Council Italy | Manoli F.,National Research Council Italy | Donzello M.P.,University of Rome La Sapienza | Viola E.,University of Rome La Sapienza | And 7 more authors.
Inorganic Chemistry | Year: 2013

We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (ZnII/PtII) porphyrazine hexacation, [(PtCl2)(CH3)6LZn]6+, and its octacationic analogue [(CH3)8LZn]8+, lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5′-d[GGG(TTAGGG)3]-3′/3′-d[CCC(AATCCC) 3]-5′, as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the ZnII/PtII hexacation [(PtCl2)(CH3)6LZn]6+ in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. TDDFT calculations of the lowest excited states of [(PtCl2)(CH3)6LZn]6+ in water provided an accurate description of the Q-band spectral region. In particular, the calculated optical spectra were in agreement with the experimental ones, obtained in the presence of micelles favoring complete disruption of the aggregates. The model for dsDNA binding that emerges from the analysis of UV-vis absorption and time-resolved fluorescence data shows the presence of complexes of 1 dsDNA molecule with 1, 2, and 4 macrocycles. Comparing the results for the hexacation [(PtCl2)(CH 3)6LZn]6+ with those for the [(CH 3)8LZn]8+octacation, we observed a higher degree of monomerization for the [(PtCl2)(CH3) 6LZn]6+ derivative. © 2012 American Chemical Society.

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