Copper colloidal nanoparticles are obtained by laser ablation in aqueous solutions of ligands by nanosecond laser pulses at 532 and 1064 nm and examined by localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) spectroscopy, along with transmission electron microscopy (TEM) and zeta potential measurements. This fabrication method, besides providing SERSactive substrates without spectral interferences of reagents, as it generally occurs for the chemical reduction of metal ions, allows obtaining colloidal suspensions which are stable in time because the copper particles are capped by ligand molecules as long as they are formed by laser ablation. This prevents aggregation among metal nanoparticles and probably reduces overall oxidation of the copper surface.

Surface-enhanced Raman scattering (SERS) of adenine-containing microRNA chains has been obtained by adsorption on roughened silver substrates. The spectral features of all of these samples appear dominated by the bands of adenine. By comparison with the SERS spectra of adenine and adenosine obtained on the same substrates, along with DFT calculations on the interaction sites of adenine and adenosine with silver, inferences are discussed about the structural arrangement of the microRNA chains with respect to the metal surface. This approach gives suitable guidelines in order to investigate the adsorption of complex biomolecules on metal substrates.

Protonated forms of the tetrazine ligand L2 (3,6-bis(morpholin-4-ylethyl)-1,2,4,5-tetrazine) interact with iodide in aqueous solution forming relatively stable complexes (ΔG° = -11.6(4) kJ mol for HL2 + I = (HL2)I and ΔG° = -13.4(2) kJ mol for HL2 + I = [(HL2)I]). When solutions of [(HL2)I] are left in contact with air, crystals of the oxidation product (HL2)(I)I·4HO are formed. Unfortunately, the low solubility of I complexes prevents the determination of their stability constants. The crystal structures of HL2I·HO (1), HL2(I)·2HO (2) and (HL2)(I)I·4HO (3) were determined by means of X-ray diffraction analyses. In all crystal structures, it was found that the interaction between I and I with HL2 is dominated by anion interactions with the π electron density of the receptor. Only in the case of 1, the iodide anions involved in close anion-π interactions with the ligand tetrazine ring form an additional H-bond with the protonated morpholine nitrogen of an adjacent ligand molecule. Conversely, in crystals of 2 and 3 there are alternate segregated planes which contain only protonated ligands hydrogen-bonded to cocrystallized water molecules or I and I forming infinite two-dimensional networks established through short interhalogen contacts, making these crystalline products good candidates to behave as solid conductors. In the solid complexes, the triiodide anion displays both end-on and side-on interaction modes with the tetrazine ring, in agreement with density functional theory calculations indicating a preference for the alignment of the I molecular axis with the molecular axis of the ligand. Further information about geometries and structures of triiodide anions in 2 and 3 was acquired by the analysis of their Raman spectra.

The conformational distribution of glycerol is still an open question both in gas and in liquid phase. Density functional calculations on different conformers of glycerol are reported and compared to the experimental infrared spectra of the gas and of the liquid. The experimental infrared spectra of gas and liquid glycerol are fitted by a linear combination of the single conformer ab initio spectra, obtaining the relative conformer concentrations. For the gas the results are in agreement with electron diffraction experiments and with molecular dynamics simulation data. The conformational distribution of glycerol in liquid phase is less accurate but always indicative. Some results about the role of the intramolecular hydrogen bonding in stabilization and in structural features of the conformers are discussed.

Fluorescence, S1 → S0, and fluorescence excitation, S0 → S1, spectra of 1,6-methano[10]annulene have been measured in glassy matrixes at low temperature under moderate site selection conditions. The polarization ratios of both spectra have been also measured at 77 K. MO ab initio calculations including correlation effects indicate that the molecule has one energy minimum in the ground state and one in the lowest excited singlet state. They correspond to bond-equalized structures of aromatic character. The spectra are accordingly discussed in terms of transitions involving the aromatic form of 1,6-methano[10]annulene. A good correlation is found between observed and calculated Franck−Condon intensities.