Search results for "molecular electronic"
showing 10 items of 126 documents
Dynamic properties of some β-chain mutant hemoglobins
1995
The thermal behavior of the Soret band relative to the carbonmonoxy derivatives of some beta-chain mutant hemoglobins is studied in the temperature range 300-10 K and compared to that of wild-type carbonmonoxy hemoglobin. The band profile at various temperatures is modeled as a Voigt function that accounts for homogeneous broadening and for the coupling with high- and low-frequency vibrational modes, while inhomogeneous broadening is taken into account with a gaussian distribution of purely electronic transition frequencies. The various contributions to the over-all bandwidth are singled out with this analysis and their temperature dependence, in turn, gives information on structural and dy…
Structure-dynamics-function relationships in Asian elephant (Elephas maximus) myoglobin. An optical spectroscopy and flash photolysis study on functi…
1993
In this work we report the thermal behavior (10–300 K) of the Soret band lineshape of deoxy and carbonmonoxy derivatives of Asian elephant (Elephas maximus) and horse myoglobins together with their carbon monoxide recombination kinetics after flash photolysis; the results are compared to analogous data relative to sperm whale myoglobin. The Soret band profile is modeled as a Voigt function that accounts for the coupling with high and low frequency vibrational modes, while inhomogeneous broadening is taken into account with suitable distributions of purely electronic transition frequencies. This analysis makes it possible to isolate the various contributions to the overall lineshape that; in…
Isotope Shifts of Radium Monofluoride Molecules
2021
Isotope shifts of $^{223-226,228}$Ra$^{19}$F were measured for different vibrational levels in the electronic transition $A^{2}{}{\Pi}_{1/2}\leftarrow X^{2}{}{\Sigma}^{+}$. The observed isotope shifts demonstrate the particularly high sensitivity of radium monofluoride to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. Ab initio quantum chemical calculations are in excellent agreement with experimental observations. These results highlight some of the unique opportunities that short-lived molecules could offer in nuclear structure and in fundamental symmetry studies.
An Atom-Economical Approach to Functionalized Single-Walled Carbon Nanotubes: Reaction with Disulfides
2013
Owing to their unique structure, thermal stability, and mechanical and electronic properties, single-walled carbon nanotubes (SWCNTs) have been a subject of continuous and intense interest. However, various applications in many fields, such as molecular electronics, solar cells, and nanomedicine, often require the development of reproducible protocols for the chemical modification of SWCNTs. In fact, one of the main drawbacks of the use of SWCNTs is their tendency to aggregate and intrinsic poor solubility, which prevent their manipulation and limit their potential. To date, several methods have been described for the chemical functionalization of SWCNTs; however, new versatile and reliable…
Photokinetic examination of (Z,E,E)-4,4′-distyrylazobenzene
1995
Abstract 4,4′-Distyrylazobenzenes demonstrate a photokinetic equilibrium and a superimposed thermal backward reaction in which the absorption coefficient of one of the partners in the equilibrium is principally unknown. Using the dependence of the photostationary state on the irradiation intensity, the photochemical quantum yields ϕ 1 A and ϕ 2 B were determined, as well as the thermal rate constant k , as a function of the irradiation and observation wavelengths. Experimental difficulties and the wavelength dependence of ϕ 1 A and ϕ 2 B are discussed.
Chemical design of coordination polymers and functional materials: from pore control in MOFs through spin dynamics in nanomagnets to rotaxanes in mol…
2022
El trabajo de esta tesis se enmarca en el diseño químico de polímeros de coordinación y de materiales funcionales para poder ser utilizados en el campo de los materiales moleculares. El capítulo 1 ofrece una visión de los avances más significativos en la química de coordinación, así como una introducción general de los materiales moleculares más relevantes en la actualidad. El objetivo es proporcionar al lector el conocimiento necesario para establecer las bases sobre los campos a tratar. El resto de capítulos está organizado de acuerdo con un aumento de la dimensionalidad, empezando con moléculas discretas y terminando con polímeros de coordinación. El capítulo dos describe dos estructuras…
Hybrid Molecular Materials Based upon Organic π-Electron Donors and Inorganic Metal Complexes. Conducting Salts of Bis(ethylenediseleno)tetrathiafulv…
2002
Abstract The synthesis, structure and physical characterization of three new radical salts formed by the organic donor bis(ethylenediseleno)tetrathiafulvalene (BEDS-TTF or BEST) and the paramagnetic hexacyanoferrate(III) anion [Fe(CN)6]3− or the photochromic nitroprusside anion [Fe(CN)5NO]2− are reported: (BEST)4[Fe(CN)6] (1), (BEST)3[Fe(CN)6]2·H2O (2) and (BEST)2[Fe(CN)5NO] (3). Salts 1 and 3 show a layered structure with alternating organic (β–type packing) and inorganic slabs. Salt 2 shows an original interpenetrated structure probably due to the unprecedented presence of (BEST)2+ dications. The three salts are semiconductors although salt 1 exhibits a high room temperature conductivity …
Diamondoids: functionalization and subsequent applications of perfectly defined molecular cage hydrocarbons
2014
The term “diamondoid” describes cage hydrocarbon molecules that are superimposable on the diamond lattice. Diamondoids that are formally built by face-fusing of adamantane units, namely diamantane, triamantane, tetramantane, etc., have fascinated chemists since the beginning of the last century. The functionalization of these perfectly defined (C,H)-molecules is described here. Thus, diamondoid halides and diamondoid alcohols are first rank precursors for amino and phosphine-substituted diamondoids that have proved to be highly useful in therapeutic applications and metal catalysis, respectively. The extent of functionalization and polyfunctionalization achieved for adamantane and diamantan…
Experimental and theoretical studies on the electronic spectra of indole-3-acetic acid and its anionic and protonated species
1991
Abstract The geometrical and electronic structure of indole-3-acetic acid (IAH) have been investigated using the MINDO/3 molecular orbital method, the geometries being optimized by Rinaldi's method. The UV spectrum of IAH has been recorded in different solvents. The corresponding spectra of IAH + 2 and IA − were also respectively obtained, from IAH in different H 2 SO 4 /water mixtures and NaOH solutions. The agreement of experimental spectra with the ones theoretically calculated by the CNDO/M-Cl method after optimization of the κ parameter, is discussed. The p K a values of IAH have also been determined from the IAH + 2 spectra and are compared with literature data.
From linear quaterthiophene to sulflower: A comparative theoretical study
2009
Abstract In this paper, we report a theoretical study of four types of thiophene-based oligomers showing the same number of C C double bonds and very different molecular structures. The comparative study has been performed on the basis of B3LYP/6-31G∗∗ calculations. The way the thiophene rings are linked together has a remarkable influence on the molecular and electronic properties. Linear quaterthiophene and heptathienoacene show similar aromatic structures but a loss of π-conjugation is detected for the latter due to the condensation of thiophene rings. A blue shift of the most intense electronic transition is predicted for fused heptathienoacene compared with non-fused quaterthiophene. C…