Search results for "etica"

Mechanism of activated chemiluminescence of cyclic peroxides: 1,2-dioxetanes and 1,2-dioxetanones

2017

Almost all chemiluminescent and bioluminescent reactions involve cyclic peroxides. The structure of the peroxide and reaction conditions determine the quantum efficiency of light emission. Oxidizable fluorophores, the so-called activators, react with 1,2-dioxetanones promoting the former to their first singlet excited state. This transformation is inefficient and does not occur with 1,2-dioxetanes; however, they have been used as models for the efficient firefly bioluminescence. In this work, we use the SA-CASSCF/CASPT2 method to investigate the activated chemiexcitation of the parent 1,2-dioxetane and 1,2-dioxetanone. Our findings suggest that ground state decomposition of the peroxide com…

Identification and H(D)-bond energies of C-H(D)Cl interactions in chloride-haloalkane clusters: a combined X-ray crystallographic, spectroscopic, and…

2016

The cationic (1,3,5-triazapentadiene)Pt(II) complex [Pt{NH[double bond, length as m-dash]C(N(CH2)5)N(Ph)C(NH2)[double bond, length as m-dash]NPh}2]Cl2 ([]Cl2) was crystallized from four haloalkane solvents giving [][Cl2(CDCl3)4], [][Cl2(CHBr3)4], [][Cl2(CH2Cl2)2], and [][Cl2(C2H4Cl2)2] solvates that were studied by X-ray diffraction. In the crystal structures of [][Cl2(CDCl3)4] and [][Cl2(CHBr3)4], the Cl(-) ion interacts with two haloform molecules via C-DCl(-) and C-HCl(-) contacts, thus forming the negatively charged isostructural clusters [Cl(CDCl3)2](-) and [Cl(CHBr3)2](-). In the structures of [][Cl2(CH2Cl2)2] and [][Cl2(C2H4Cl2)2], cations [](2+) are linked to a 3D-network by a syste…

Photochemistry and Redox Chemistry of an Unsymmetrical Bimetallic Copper(I) Complex

2016

The bimetallic copper(I) complex Cu2L2 (cis-1) is formed with high diasteroselectivity from [Cu(NCCH3)4][BF4] and HL (4-tert-butyl phenyl(pyrrolato-2-yl-methylene)amine) in a kinetically controlled reaction. cis-1 features a rather short Cu···Cu distance of 2.4756(6) A and is weakly emissive at room temperature in solution. Oxidatively triggered disproportionation of cis-1 yields elemental copper and the mononuclear copper(II) complex CuL2 (trans-2). One-electron reduction of trans-2 gives cuprate [2]– with a bent bis(pyrrolato) coordinated copper(I) entity. The imine donor atoms of [2]– can insert an additional copper(I) ion giving exclusively the bimetallic complex cis-1 closing the oxida…

On the Road to MM′X Polymers: Redox Properties of Heterometallic Ni···Pt Paddlewheel Complexes

2014

On the quest of heterometallic mixed-valence MM'X chains, we have prepared two stable discrete bimetallic compounds: the reduced (PPN)[ClNi(μ-OSCPh)4Pt] (PPN = bis(triphenylphosphine)iminium; OSCPh = benzothiocarboxylato) and the oxidized [(H2O)Ni(μ-OSCPh)4PtCl] species. The role of the aqua and chlorido axial ligands is crucial to facilitate oxidation of the {Ni(μ-OSCPh)4Pt} core. Experimental and theoretical analyses indicate that a NiPt-Cl/Cl-NiPt isomerization process occurs in the oxidized species. The electronic structure of the reduced system shows two unpaired electrons, one located in a d(x(2)-y(2)) orbital of the Ni(II) ion and a second in the antibonding d(z(2)-dz(2)) combination…

Electrochemical, Spectroelectrochemical, and Structural Studies of Mono- and Diphosphorylated Zinc Porphyrins and Their Self-Assemblies

2019

International audience; Three series of porphyrins containing a Zn(II) central metal ion and zero, one or two phosphoryl groups at the meso-positions of the macrocycle were characterized as to their electrochemical, spectroscopic and structural properties in non-aqueous media. The investigated compounds are represented as 5,15-bis(4'-R-phenyl)porphyrinatozinc, 10-(diethoxyphosphoryl)-5,15-bis(4'-R-phenyl)porphyrinatozinc and 5,15-bis(diethoxyphosphoryl)-10,20-bis(4'-R-phenyl)porphyrinatozinc, where R = OMe, Me, H or CN. Linear-free energy relationships are observed between the measured redox potentials at room temperature and the electronic nature of the substituents at the 5 and 15 meso-ph…

Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy

1996

Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminat…

Intermolecular and Intramolecular Transamidation Reactions

2006

The amide functional group is resonance stabilised and direct reaction with amines is known to be difficult. Facile amide exchange reactions would enable the synthesis of important new amide based molecules, therefore transamidation reactions represent an important step in this direction. In order to ensure a transamidation reaction takes place, special requirements and conditions are required. According to the different structural characteristics of the carbox-amide group and types of activation, the most relevant examples of this reaction will be reviewed.

Synthesis of Lamellarin G Trimethyl Ether by von Miller-Plöchl-Type Cyclocondensation

2018

Harnessing Fluorescence versus Phosphorescence Ratio via Ancillary Ligand Fine-Tuned MLCT Contribution

2016

A series of gold(I) alkynyl-diphosphine complexes (XC6H4C2Au)PPh2—spacer—PPh2(AuC2C6H4X); spacer = —C2(C6H4)nC2— (A1, n = 2, X = CF3; A2, n = 2, X = OMe; A3, n = 3, X = CF3; A4, n = 3, X = OMe), —(C6H4)n— (B5, n = 3, X = OMe; B6, n = 4, X = OMe) were prepared, and their photophysical properties were investigated. The luminescence behavior of the titled compounds is dominated by the diphosphine spacer, which serves as an emitting ππ* chromophore. The complexes exhibit dual emission, comprising low and high energy bands of triplet (phosphorescence) and singlet (fluorescence) origins, respectively. The electron-donating characteristics of ancillary groups X significantly affect the LLCT/MLCT c…

Soluble Heterometallic Coordination Polymers Based on a Bis-terpyridine-Functionalized Dioxocyclam Ligand

2010

Soluble homo- and heterometallic coordination polymers containing transition metal cations (Cu(2+), Fe(2+), Co(2+), and Ni(2+) ions) were prepared in a two-step procedure using a polytopic bis(terpyridine)dioxocyclam ligand 1H(2) (dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione). These supramolecular systems incorporate two different metal complexes, the metal cations being located both between two terpyridine units and in the macrocyclic framework. The characterization of these soluble architectures was investigated by cyclic voltammetry, mass spectrometry, viscosimetry, and UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopies. Our results clearly indicate t…