ARGON MATRIX ISOLATION AND SPECTROSCOPIC CHARACTERIZATION OF COMPLEXES BETWEEN AROMATIC LIGANDS AND TRANSITION METAL ATOMS AND DI-OR TRI-ATOMIC METAL AGGREGATES.

1. A KLOTZ, G. SERRA, P. BOISSEL, J.MASCETTI, J DEROUAULT, B. CHAUDRET, et al Planetary \& Space Science, 1996, 44, 957. 2. B. CHAUDRET et al. New J. Chem. 1991, 15, 791.Author Institution: LSMC, University of Bordeaux IIn the first stage of this work, the co-condensation of chronium metallic vapors and benzene in an argon matrix has demonstrated the existence of a number of complexes involving one, two or three chromium atoms and one or two benzene molecules. These complexes have been identified through their Raman and UV-Visible spectra and by using deuterium/hydrogen substitution. The inter conversion of these complexes may be induced and monitored by using selective photo-irradiations. In the second part of the study. the reactivity of several PAH Aromatic ligands with iron atoms and di-atomic iron molecules have been studied because of their interest for the Astro-physicians community (1). The PAH are actually thought to be responsible for the Unidentified Infrared Bands coming from the Inter-Stellar Medium. A second question to be resolved is the problem of the iron depletion. Some author (2) assume that a part of the missing Iron could be masked inside Fe-PAH complexes. FTIR investigations of Argon matrices have demonstrated that such neutral complexes are like to be formed in low temperature dense regions of the ISM. Furthermore, the results strongly suggest that the Iron dimer reacts preferentially with the coronene molecule. When pyrene is used as a PAH ligand, three different complexes may be obtained, with different metal-ligand bonding. Unlike Chromium complexes, Iron compounds do not seem to be sensitive to photo-irradiation; but careful annealing may induce some evolution of them. Studies involving naphtalene as a PAH are planed for the next future in order to compare the results with those obtained by P.BOISSEL in ion-trapped experiments concerning cationic iron-naphtalene complexes

On the catalytic properties of mixed oxides obtained from the Cu-Mg-Al LDH precursors in the process of hydrogenation of the cinnamaldehyde

International audienceCatalytic hydrogenation of cinnamaldehyde (CNA) was investigated over oxidic materials obtained by the calcination of Cu-Mg-Al layered double hydroxide (LDH) precursors. A series of precursors with different Cu/Mg ratios (with a constant M2+/Al3+ ratio) were prepared by coprecipitation (under low supersaturation) and heated under reductive atmosphere until 623K in order to avoid the formation of Cu-based spinels and to reduce the copper cations. The presence of Mg noticeably enhanced the selectivity of Cu-based catalysts with respect to the hydrogenation of the carbonyl group relative to the favoured hydrogenation of the C=C bond. Moreover, the self-condensation of hydrocinnamaldehyde (HCNA) and the cross-condensation of hydrocinnamaldehyde with cinnamaldehyde were also observed especially when the basic sites of LDH structures are preponderant over hydrogenation species. Finally, all that reaction from CNA are of great interest for getting information about: (i) basic sites involved in condensation of CNA and HCNA; and (ii) active species for selective hydrogenation of CNA to cinnamyl alcohol (CNOL) which seem in strong interaction with the first ones. © 2003 Elsevier B.V. All rights reserved

Vibrational study of N-phenyl-substituted hydroxynaphthylaldiminate copper(II) complexes

The infrared spectra of seven bis(N-phenyl-substituted hydroxynaphthylaldiminate) complexes of Cu(II) were scanned from 4000 to 100 cm-1. Particular emphasis is given to the low-energy region. The assignment of the chelate normal modes is supported by an approximate normal coordinate analysis based on a simplified general valence force field, and the geometrical parameters of the bis(N-phenylsalicylaldiminate)Cu(II) complex. The bands near 390 and 285 cm-1 are assigned to the CuO and CuN stretching vibrations, respectively. The corresponding force constants are estimated to be 1.37 and 0.88 mdyn Å-1. Influence of the nature of the different ligands on the structure of complexes is discussed. Similarity of the vibrational spectra for all the complexes suggests that they possess the same type of structure. © 1993

Photo-induced generation of the riboflavin-tryptophan adduct and a vibrational interpretation of its structure

A pure fraction of a riboflavin-tryptophan adduct was obtained for the first time from a mixture of products resulting from the anaerobic photoirradiation of riboflavin and tryptophan in solution. The procedure used to isolate the adduct is described. Characterization of the compound was performed by using absorption spectra and fluorescence measurements. A vibrational interpretation of the structure of this adduct was performed on the basis of its infrared spectrum. The vibrational assignment suggests an important electronic redistribution in the structure of riboflavin and tryptophan when the adduct is formed. From this fact can be inferred at least two ways of binding between the indole and isoalloxazine rings. Stability of the adduct is also discussed. © 1994

Evolution of the banana genome (Musa acuminata) is impacted by large chromosomal translocations

Most banana cultivars are triploid seedless parthenocarpic clones derived from hybridization between Musa acuminata subspecies and sometimes M. balbisiana. M. acuminata subspecies were suggested to differ by a few large chromosomal rearrangements based on chromosome pairing configurations in inter-subspecies hybrids. We searched for large chromosomal rearrangements in a seedy M. acuminata ssp. malaccensis banana accession through mate-pair sequencing, BAC-FISH, targeted PCR and marker (DArTseq) segregation in its progeny. We identified a heterozygous reciprocal translocation involving two distal 3 Mb and 10 Mb segments from chromosomes 01 and 04, respectively, and showed that it generated high segregation distortion, reduced recombination and linkage between chromosomes 01 and 04 in its progeny. The two chromosome structures were found to be mutually exclusive in gametes and the rearranged structure was preferentially transmitted to the progeny. The rearranged chromosome structure was frequently found in triploid cultivars but present only in wild malaccensis ssp. accessions, thus suggesting that this rearrangement occurred in M. acuminata ssp. malaccensis. We propose a mechanism for the spread of this rearrangement in Musa diversity and suggest that this rearrangement could have played a role in the emergence of triploid cultivars