π-Stacking attraction vs. electrostatic repulsion: competing supramolecular interactions in a tpphz-bridged Ru(II)/Au(III) complex

The synthesis and characterization of a mixed metal ruthenium(II)/gold(III) complex bridged by tetrapyridophenazine (tpphz) are described. It is isostructural and isoelectronic to the well-known photocatalysts with palladium(II) or platinum(II). Concentration dependent 1H-NMR spectroscopy and XRD studies show that the electrostatic repulsion between the gold(III) moieties exceeds the attractive π-stacking interaction. Theoretical calculations based on the new structural data confirm an increased positive charge on the bridging ligand as well as significantly altered orbital symmetry as compared to the previously investigated palladium(II) complex. This is the first example of a tpphz ruthenium(II) complex where π-stacking is completely inhibited. The detailed investigation of the solid-state structure showed for the first time in bimetallic tpphz bridged complexes no significant torsion within the bridging ligand itself. Although catalytic performance for proton reduction by gold(III) is naturally not observed, its photochemical decomposition in colloidal gold particles could be shown by TEM and DLS

Photoelectron spectroscopy of a series of acetate and propionate esters

The electronic state and photoionization spectroscopy of a series of acetate esters: methyl acetate, isopropyl acetate, butyl acetate and pentyl acetate as well as two propionates: methyl propionate and ethyl propionate, have been determined using vacuum-ultraviolet photoelectron spectroscopy. These experimental investigations are complemented by ab initio calculations. The measured first adiabatic and vertical ionization energies were determined as: 10.21 and 10.45 eV for methyl acetate, 9.99 and 10.22 eV for isopropyl acetate, 10.07 and 10.26 eV for butyl acetate, 10.01 and 10.22 eV for pentyl acetate, 10.16 and 10.36 eV for methyl propionate and 9.99 and 10.18 eV for ethyl propionate. For the four smaller esters vibrational transitions were calculated and compared with those identified in the photoelectron spectrum, revealing the most distinctive ones to be a C–O stretch combined with a C[dbnd]O stretch. The ionization energies of methyl and ethyl esters as well as for a series of formates and acetates were compared showing a clear dependence of the value of the ionization energy on the size of the molecule with very little influence of its conformation

Electronic state spectroscopy by high-resolution vacuum ultraviolet photoabsorption, He(I) photoelectron spectroscopy and ab initio calculations of ethyl acetate

Abstract: The high-resolution vacuum ultraviolet photoabsorption spectrum of ethyl acetate,C4H8O2, is presented over the energy range 4.5−10.7 eV (275.5−116.0 nm). Valence and Rydberg transitionsand their associated vibronic series observed in the photoabsorption spectrum, have beenassigned in accordance with new ab initio calculations of the vertical excitation energiesand oscillator strengths. Also, the photoabsorption cross sections have been used tocalculate the photolysis lifetime of this ester in the upper stratosphere(20−50 km). Calculationshave also been carried out to determine the ionisation energies and fine structure of thelowest ionic state of ethyl acetate and are compared with a newly recorded photoelectronspectrum (from 9.5 to 16.7 eV). Vibrational structure is observed in the firstphotoelectron band of this molecule for the first time

Étude théorique de molécules conjuguées d intérêt biologique pour l optique non linéaire

This thesis presents a density functional theory (DFT and TDDFT) study, in which we describe the non linear optical response of molecular probes in biological environment. The considered systems are first push-pull molecules (nitrobenzene substituted by an electronic donor group) in connection with the para-nitrophenylphosphate molecule and secondly the aromatic amino acids, tryptophan, tyrosine and phenylalanine. In this work, we determine the ground state and excited states electronic structure, as well as the components of the polarizability and hyperpolarizability tensors, describing the optical properties of the molecule. The description of the biological environment, particularly the aqueous solvent surrounding the molecules, is realized by means of a polarisable dielectric model and by solvent molecules forming hydrogen bounds with the soluteCette thèse présente une étude théorique menée par des méthodes de la théorie de la fonctionnelle de la densité (DFT et TDDFT), dans laquelle on modélise la réponse optique non linéaire de molécules sondes en milieu biologique. Les systèmes considérés sont d une part des molécules push-pull (nitrobenzène substitué par un groupe donneur d électrons) en relation avec la molécule de para-nitrophénylphosphate et d autre part les acides aminés aromatiques, tryptophane, tyrosine et phénylalanine. Dans ce travail on détermine la structure électronique de l état fondamental et des états excités, ainsi que les composantes des tenseurs de polarisabilité et d hyperpolarisabilité décrivant les propriétés optiques de la molécule. La description de l environnement biologique, notamment celle du solvant aqueux entourant les molécules, est réalisée au moyen d un modèle diélectrique polarisable et de molécules de solvant formant des liaisons hydrogène avec le solutéLYON1-BU.Sciences (692662101) / SudocSudocFranceF