Search results for "Protonation"

Selective formation of a unique diphosphonium-diphosphine from a tetraphosphine double protonation induced by zirconium salts

2008

A mixed ferrocenyl diphosphonium-diphosphine cation, associated with two [ZrCl(5).thf](-) anions, is obtained from a ferrocenyl tetraphosphine, as a unique didentate ionic metalloligand in a perfectly selective reaction induced by ZrCl(4) in THF.

ChemInform Abstract: Theoretical and Spectroscopic Studies on Imino-Carbon Palladated Pyridine-2-carbaldimines.

1987

Abstract Ab initio LCAO-MO-SCF calculations on the model compounds C 5 H 4 N-2-C(R 1 )=NH [R 1 = H ( 2c ) and R 1 = trans -PdCl(PH 3 ) 2 ( 4c )] indicate that the E - trans conformation is favored over the E - cis one by 16.9 kJ mol −1 for 2c and by 25.0 kJ mol −1 for 4c . One of the factors which stabilizes the E-trans arrangement for 4c is a weak bonding interaction between the palladium center and the pyridine nitrogen. On going from 2c to 4c a slight charge enrichment on the pyridine carbons and a more pronounced one on the nitrogen atoms is computed, whereas the charge density of the imino carbon atom is decreased. In 4c no π contribution to the PdC bond is observed. Protonation of th…

Efficient stabilisation of a dihydrogenphosphate tetramer and a dihydrogenpyrophosphate dimer by a cyclic pseudopeptide containing 1,4-disubstituted …

2017

A cyclic pseudooctapeptide 2 is described containing 1,4-disubstituted 1,2,3-triazole moieties. This compound features eight converging hydrogen bond donors along the ring, namely four amide NH and four triazole CH groups, which enable 2 to engage in interactions with anions. While fully deprotonated sulfate anions exhibit only moderate affinity for 2, protonated anions such as dihydrogenpyrophosphate and dihydrogenphosphate anions are strongly bound. Complexation of the phosphate-derived anions involves sandwiching of a dihydrogenpyrophosphate dimer or a dihydrogenphosphate tetramer between two pseudopeptide rings. X-ray crystallography provided structural information, while 1H NMR spectro…

Tuning the Electrochemistry of Free-Base Porphyrins in Acidic Nonaqueous Media: Influence of Solvent, Supporting Electrolyte, and Ring Substituents

2016

International audience; A detailed study of reduction potentials, electroreduction mechanisms and acid-base chemistry was carried out on two series of free-base porphyrins in nonaqueous media. The first series is represented by four-pyrrole substituted tetraphenylporphyrin (TPP) derivatives, two of which are planar and two of which are nonplanar in their non-protonated form. The second comprises porphyrins with 0-4 meso-phenyl groups on the macrocycle. Equilibrium constants for conversion of each neutral porphyrin to its diprotic [H4P] 2+ form were determined and the electrochemistry was then elucidated as a function of: (i) type of nonaqueous solvent, (ii) anion of supporting electrolyte, …

Conserved histidine and tyrosine determine spectral responses through the water network in Deinococcus radiodurans phytochrome

2022

Funding Information: This work was supported by Academy of Finland grants 285461 (H.T.), 330678 (H.T., J.R.), 277194 (H.L.), and 290677 (S.M.). We acknowledge the European Synchrotron Radiation Facility (ESRF) for providing synchrotron access for crystal data collection. We thank Prof. Janne Ihalainen (University of Jyväskylä) for all the help in all aspects of the paper, Prof. Gerrit Groenhof (University of Jyväskylä) for support, and Prof. Nikolai V. Tkachenko (Tampere University) for help and facilities for time-resolved absorption spectroscopy. We also thank M.Sc. Alli Liukkonen (University of Jyväskylä) and Dr. Heikki Häkkänen (University of Jyväskylä) for the assistance in laboratory …

Diorganotin(IV) complexes ofD-galacturonic acid: solid-state and solution-phase structural study

2003

Three diorganotin(IV) complexes of D-galacturonic acid (H2GalA; R = Me, n-Bu, Ph), two of which are new derivatives (R = Me, Ph), have been synthesized and their solid-state and solution-phase investigated by IR, Mossbauer, 1H, 13C and 119Sn NMR spectroscopy. The FTIR data suggest that H2GalA, in the dialkyltin derivatives, behaves as a dianionic ligand, coordinating the tin(IV) atom through an ester-type carboxylate and deprotonated alcoholic hydroxo groups, whereas a bridging carboxylate occurs in the diphenyltin(IV) complex. Octahedral and trigonal bipyramidal local geometries on tin(IV) atoms are proposed for dialkyltin(IV)GalA and diphenyltin(IV)GalA complexes respectively on the basis…

Revisited Dual Luminescence of 2,2′-Dipyridylamine Hydrochloride in Solution and Physical Processes behind It

2018

On the physicochemical properties of pyridohelicenes.

2014

A comprehensive study on the physicochemical properties of a series of mono- and diaza[5]helicenes as well as mono- and diaza[6]helicenes is reported. Through the use of both computational and experimental methods, these helically chiral pyridohelicenes with the nitrogen atom(s) in various positions are characterised according to their inversion barriers, protonation constants and redox potentials. By using DFT calculations, kinetic measurements, UV/Vis titrations, cyclic voltammetry and EPR spectroscopy, a self-contained picture of their behaviour under conventional treatment by heat, acids and oxidising/reducing agents is provided.

Equilibrium and structural studies of complexes with a hexadentate ligand containing amide, amine and pyridyl nitrogen donors. Crystal structures of …

2002

A novel potentially hexadentate ligand, 1,8-bis(2-pyridylcarbamoyl)-3,6-diazaoctane (pyctrien) has been synthesised as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Amide group deprotonation permits the formation of [MLH−1]+ and [MLH−2] species in all cases, whereas the detection of the neutral or the protonated species depends on the nature of the metal ions. The solid complexes of copper, nickel and cobalt with the neutral and the deprotonated ligand have been synthesised and characterised by IR and UV–VIS spectroscopy. The amidic groups are coordinated through the oxygen …

Open-chain polyamine ligands bearing an anthracene unit - Chemosensors for logic operations at the molecular level

2001

In this work the absorption and the fluorescence emission properties as well as the protonation sequence of three open chain polyamine ligands of different dimensions bearing an anthracene unit were studied. The protonation and stability constants with Ni2+, Cu2+, Zn2+, and Cd2+ have been determined in 0.15 mol·dm−3 NaCl at 298.1 ± 0.1 K. The values of both protonation and stability constants follow the expected trends according to the number of nitrogen donors, sequence of chelate rings and hydrophilic−hydrophobic balance. Chelation enhancement of the fluorescence emission (CHEF) was observed for some complexes of these ligands with Zn2+ and Cd2+. In contrast the analog complexes containin…