Search results for " Chemistry"
showing 10 items of 41321 documents
Polysubstituted ferrocenes as tunable redox mediators
2018
A series of four ferrocenyl ester compounds, 1-methoxycarbonyl- (1), 1,1’-bis(methoxycarbonyl)- (2), 1,1’,3-tris(methoxycarbonyl)- (3) and 1,1’,3,3’-tetrakis(methoxycarbonyl)ferrocene (4), has been studied with respect to their potential use as redox mediators. The impact of the number and position of ester groups present in 1–4 on the electrochemical potential E1/2 is correlated with the sum of Hammett constants. The 1/1+–4/4+ redox couples are chemically stable under the conditions of electrolysis as demonstrated by IR and UV–vis spectroelectrochemical methods. The energies of the C=O stretching vibrations of the ester moieties and the energies of the UV–vis absorptions of 1–4 and 1+–4+ c…
Progression of Diiminopyridines: From Single Application to Catalytic Versatility
2015
Diiminopyridyl metal complexes, first characterized several decades ago, found practical application in 1998 when they were used as precatalysts in coordinative ethylene polymerization. This discovery contributed to the so-called postmetallocene revolution and triggered the large-scale experimental and theoretical research aimed at understanding diversified diiminopyridine chemistry. The results of this quest, some of which were intriguing and difficult to anticipate, are discussed and summarized in the current Review.
The SO2F2 quasi-spherical top: Correspondence between tensorial and Watson's formalisms
2006
Abstract The SO2F2 quasi-spherical top molecule with C2v symmetry is considered as a distorted spherical top deriving from the SO 4 2 − tetrahedral ion. We present here a detailed correspondence between the tensorial formalism using the Td⊃C2v reorientation and the usual Hamiltonian of Watson. We have also performed ab initio calculations in order to determine the centrifugal distorsion constants in the vibrational ground state.
Self-assembly of square planar rhodium carbonyl complexes with 4,4-disubstituted-2,2′-bipyridine ligands
2020
The impact of non-covalent interactions and reaction conditions on formation and self-assembly of ionic pairs of Rh complexes with 4,4’-disubstituted bipyridine ligands ([Rh(L1)(CO)2][Rh(CO)2Cl2])n (1), [Rh(L1)2Cl2][Rh(CO)2Cl2] (2), ([Rh(L1)(CO)2][Rh(CO)2Cl2][Rh(L1)(CO)2]n([Rh(CO)2(Cl)2])n) (3), ([Rh(L2)CO2] [Rh(CO)2Cl2])n∙EtOH (4), ([Rh(L2)(CO)2])n ([Rh(CO)2Cl2])n (5) (L1 = 4,4’-dimethyl-2,2’-bipyridine, L2 = 4,4’-diamine-2,2’-bipyridine) have been studied. Packing of square planar Rh complexes favor formation of one-dimensional chains. In structure 1, the polymeric chain is formed by the alternating cationic [Rh(L1)(CO)2]+ and the anionic [Rh(CO)2Cl2]- units leading to a neutral pseudo li…
Potential-assisted deposition of mixed alkanethiol self-assembled monolayers
2010
Abstract Preparation of self-assembled monolayers (SAMs) usually involves passive incubation. The recently developed potential-assisted deposition is indeed more selective as well as 100-fold faster than passive adsorption, thereby enhancing the reproducibility of the monolayer deposition. This article aims to identify the electrodeposition conditions necessary to prepare mixed alkanethiol SAMs on gold surface. Parameters such as concentrations in solution, electrode polarization and deposition time were examined for two chain lengths, C 3 (mercaptopropionic acid, MPA) and C 18 (octadecanethiol, ODT). The kinetics and composition of the SAMs were systematically characterized by reductive st…
Relay Catalysis: Enantioselective Synthesis of Cyclic Benzo-Fused Homoallylic Alcohols by Chiral BrOnsted Acid-Catalyzed Allylboration/Ring Closing M…
2013
Six- and seven-membered benzo-fused cyclic homoallylic alcohols can be readily synthesized by a tandem chiral BrOnsted acid-catalyzed allyl (crotyl)boration/ring closing metathesis sequence performed under orthogonal relay catalysis conditions. Excellent enantio- and diastereoselectivities are obtained in most of the cases. In addition, the parent crotylboration/RCM process is also described. The required substrates, ortho-vinylbenzaldehydes, are readily available in one step from commercially available starting materials. Both catalysts and reactants are also available from commercial suppliers. The reaction shows broad functional group compatibility and is also suitable for heteroaromatic…
Dynamics of hydrofracturing and permeability evolution in layered reservoirs
2015
International audience; A coupled hydro-mechanical model is presented to model fluid driven fracturing in layered porous rocks. In the model the solid elastic continuum is described by a discrete element approach coupled with a fluid continuum grid that is used to solve Darcy based pressure diffusion. The model assumes poro-elasto-plastic effects and yields real time dynamic aspects of the fracturing and effective stress evolution under the influence of excess fluid pressure gradients. We show that the formation and propagation of hydrofractures are sensitive to mechanical and tectonic conditions of the system. In cases where elevated fluid pressure is the sole driving agent in a stable tec…
Synthesis, Electrochemistry, and Photophysics of Aza-BODIPY Porphyrin Dyes
2016
International audience; The synthesis of dyad and triad aza-BODIPY-porphyrin systems in two steps starting from an aryl-substituted aza-BODIPY chromophore is described. The properties of the resulting aza-BODIPY-porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination.
The Missing Member of the Partially O-Alkylated Resorcinarene Family: Synthesis and Conformation of Methyl Tetramethoxy Resorcinarene
2013
An improved Lewis acid catalyzed synthesis method for methyl tetramethoxy resorcinarene is described, which produced the missing lower rim methyl derivative of this partially O-alkylated resorcinarene family. Structural characterization by means of variable temperature NMR experiments and single crystal X-ray diffraction studies furthermore revealed that the resorcinarene core adopts different conformations in the solid state and in solution. peerReviewed
CCDC 1524101: Experimental Crystal Structure Determination
2017
UCUZOK : 6,12,18,24-tetramethoxy-2,8,14,20-tetranonyl-4,10,16,22-tetrahydroxycalix[4]arene propan-2-ol solvate Space Group: P-1, Cell: a 12.27090(10)Å b 13.96500(10)Å c 19.53620(10)Å, α 83.2880(1)° β 89.0250(1)° γ 84.9650(1)° Work published 2017 via Cambridge Crystallographic Data Centre.