The X-ray structure of (Tl[Au(C(6)Cl(5))(2)])(n), 1, consists of 1-D linear polymer chains parallel to the crystallographic z axis. The crystal structure of 1 has channels that run parallel to these chains with interatom distances in the range 3.231-4.076 A. There are holes in these channels with diameters as large as 10.471 A, which can accommodate a variety of solvents. Complex 1 displays reversible vapochromic emission and absorption spectral behavior when the solid is exposed to a variety of organic vapors such as acetone, acetonitrile, triethylamine, acetylacetone, tetrahydrothiophene, 2-fluoropyridine, tetrahydrofuran, and pyridine. Complex 1 is luminescent at room temperature and at 77 K in the solid state. UV excitation at 495 nm leads to an emission at 531 nm.

The optical properties of [Au 2 Ag 2 (C 6 F 5 ) 4 (OCMe 2 ) 2 ] n (1) have been studied in the solid state at room temperature and at 77 K and in acetone solution (5 × 10 -4 M). The crystal structure of 1, analyzed by X-ray diffraction, consists of polymeric chains formed by repetition of Au 2 Ag 2 moieties linked through short gold-gold interactions. The emission profile observed for 1 in dilute acetone solution (5 × 10 -4 M) is assignable to pentafluorophenyl localized ππ* excited states or from π-MMCT transitions, and in the solid-state arises from metal-centered (dσ*) 1 (pσ) 1 or (dδ*) 1 (pσ) 1 excited states. When the absorption and emission spectra of compound 1 in acetone are registered at different concentrations, they display a band that does not obey the Lambert-Beer law. This deviation is consistent with molecular aggregation in solution through gold-gold interactions, and a clear correlation between the emission wavelength and the structure of 1 in the solid state and in solution is shown. DFT calculations accord with the observed experimental behavior and show the nature of the orbitals involved in each transition.

A very promising area of research in which metallophilic attraction has become the dominating factor determining the structural patterns that give rise to luminescent materials is discussed. In addition to the intrinsic conditions that a gold complex requires to show luminescence, we show how the type and number of the ligands, the coordination environments around the metal centres, the temperature, the heterometal, the metal-metal distances, etc., increase the possibilities of electronic transitions and, hence, multiply the factors that affect the energy and number of emissions. We think that far from being a hindrance or a problem these findings actually give rise to a fascinating area of research with promising future applications, for instance, in imaging technology, vapour sensors, light emitting devices or even medicine, where the demand for optoelectronic devices is increasing every day.

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Classical culturing and denaturing gradient gel electrophoresis (DGGE) techniques have been used for studying the microbial diversity and dynamics of the traditional Spanish Casín cheese during manufacturing and ripening. As with other starter-free cheeses made from raw milk, the microbial diversity of Casín was shown to be high by both culturing and DGGE analyses. The culture technique showed that lactic acid bacteria (LAB) species constituted the majority of the microbial populations. Of the 14 bacterial species identified, Lactococcus garvieae was predominant in the three-day-old cheese sample, although it was replaced by Lactococcus lactis subsp. lactis at day 30. As expected, the DGGE profiles obtained were complex, consisting, depending on the sample, in five to ten different amplification bands. Among these, a band corresponding to Streptococcus thermophilus was observed throughout the whole manufacturing process. This species had never been identified from traditional Spanish cheeses previously. Culturing and molecular methods showed high populations of undesirable microorganisms, arguing for a required improvement in the hygiene of Casín manufacture. Random amplification of polymorphic DNA (RAPD) profiling suggested that the L. garvieae and L. lactis populations were composed of one and five strains, respectively. In addition, only a single L. lactis RAPD pattern was stably maintained from day three to day 30, indicating high succession of strains along ripening. After a thoroughly characterisation, strains of the two Lactococcus species could be used in designing specific starter cultures for Casín. Additional species (such as Lactobacillus plantarum and Corynebacterium variabile) might be included as adjunct cultures.

The synthesis, structural characterization, and the study of the photophysical properties of complexes [Au 2 Ag 2 (C 6 F 5 ) 4 (NtCCH 3 ) 2 ] n (1) and [Au 2 Cu 2 (C 6 F 5 ) 4 (NtCCH 3 ) 2 ] n (2) have been carried out. The crystal structure of both complexes consists of polymeric chains formed by repetition of Au 2 Ag 2 or Au 2 Cu 2 units built up by metallophilic Au(I)‚‚‚M(I) interactions that are linked through Au(I)‚‚‚Au(I) interactions. Complexes 1 and 2 are brightly luminescent in the solid state at room temperature and at 77 K with lifetimes in the nanosecond range. Both compounds 1 and 2 undergo oligomerization in solution, as observed through UV-vis and excitation spectra in acetonitrile solutions at high concentrations. Thus, a correlation between the excitation spectra in solution at different concentrations and the absorption spectra in the solid state for complex 1 can be established. Time-dependent DFT calculations agree well with the experimental results and support the idea of that the origin of the luminescence of these complexes arises from orbitals located in the tetranuclear Au 2 M 2 units.

The reactions of solutions of TlPF(6) and OPPh(3) in tetrahydrofuran or acetone with NBu(4)[AuR(2)] (R=C(6)Cl(5), C(6)F(5)) gave the new complexes [Au(C(6)Cl(5))(2)](2)[Tl(OPPh(3))][Tl(OPPh(3))(L)] (L=THF (1), acetone (2)) and the previously reported [Tl(OPPh(3))(2)][Au(C(6)F(5))(2)] (3). The crystal structures of complexes 1 and 2 display extended unsupported chains with short intermolecular interactions between alternating gold(I) and thallium(I) centres. Moreover, the Tl(I) centres show two different types of geometrical environments, such as pseudotetrahedral and distorted trigonal-bipyramidal, due to the presence of solvent molecules that act as ligands in the solid-state structure. Quasirelativistic and nonrelativistic ab initio calculations were performed to study the nature of the intermetallic Au(I)-Tl(I) interactions and are consistent with the presence of a high ionic contribution (80 %) and dispersion-type (van der Waals) interaction with a charge-transfer contribution (20 %) when relativistic effects are taken into account. All complexes are luminescent in the solid state at room temperature and at 77 K. Complexes 1 and 2 show site-selective excitation, probably due to the different environments around the Tl(I) centres. The DFT and time-dependent (TD)-DFT calculations are in agreement with the experimental excitation spectra for all complexes and confirm the site-selective excitation behaviour as a function of the Tl(I) geometrical environment.

The dinuclear head-to-tail complexes [M(2)(PPh(2)CH(2)SPh)(2)](2+) (M = Cu (1), Ag (2a, 2b), Au (4)) are obtained either by reaction of [Cu(CH(3)CN)(4)]CF(3)SO(3), AgClO(4), AgCF(3)SO(3), with equimolecular amounts of PPh(2)CH(2)SPh or of [AuCl(PPh(2)CH(2)SPh)] (3), prepared by reaction of [AuCl(tht)] and PPh(2)CH(2)SPh, with AgCF(3)SO(3). The crystal structures of complexes 2a and 4 have been established by X-ray diffraction studies. Ab initio HF/II and MP2/II calculations have been performed on the [M(2)(H(2)PCH(2)SH)(2)](2+) model, indicating that metallophilic attraction is indeed present for all the coinage metals as a correlation effect and is strengthened in the case of gold by relativistic effects. Since experimental and theoretically predicted geometries are in close agreement, we assume that our calculations are accurate enough to obtain valid conclusions.