Search

Femtosecond mid-infrared pump-probe and two-dimensional mid-infrared spectroscopy have been used to investigate the dynamics of vibrational relaxation and vibrational spectral diffusion of the asymmetric N3-stretching vibration of pseudo-octahedral azidoiron(III) complexes, [L6-nFe(N3)n]+ with n = 1 or 2 and L being an auxiliary ligand of denticity 6-n, in acetonitrile at room temperature. Compared to the free azide anion in acetonitrile solution, the vibrational relaxation dynamics are considerably accelerated. Vibrational energy transfer to the solvent is accelerated by virtue of a resonance with an overtone transition of the solvent. Intramolecular vibrational redistribution is found to be accelerated by virtue of a coupling between the initial azide stretching vibration and the torsional modes involving the axial ligands. Vibrational spectral diffusion within the asymmetric N3-stretching resonance was found to be insensitive to solvent fluctuations because the axial azide ligands are only partially accessible to the solvent. The particular role of intramolecular structural relaxations of the complex for shaping the linear and nonlinear two-dimensional infrared spectra is discussed in terms of ultrafast symmetry-breaking torsional fluctuations and on the basis of density functional theory calculations. [ABSTRACT FROM AUTHOR]

Nanostructures are considered as chemical systems of high potential owing to their unusual properties at the interface of those of molecular species and bulk metals. Consequently, they are promising candidates for application in different domains such as catalysis, magnetism, medicine, opto-electronics or sensors. The control of the characteristics of nanostructures is a fundamental prerequisite if one envisages exploring their physical or chemical properties since they vary dramatically with size, shape and surface state. Thus, the development of efficient methods leading to reproducible nanostructures is presently one of the main objectives in the nanochemistry community. Although organometallic chemistry has been early involved, it arises only marginally in the field. Nevertheless, the concepts and techniques of organometallic chemistry appear to be well-adapted for the growth of well-controlled nanostructures. This will be discussed through recent advances in the synthesis of metal and metal oxide nanoparticles in terms of size dispersion, chemical composition, surface state, shape or organization, pointing out the role of ligands. Moreover their characterization at a molecular level and the development of their chemical/physical properties towards applications will be described. This review reflects more than 20 years of efforts of our team to achieve these goals. [ABSTRACT FROM AUTHOR]