Browse
Submit Data
Databases
API
Help

Dataset Information

31 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Coordination chemistry and reactivity of a cupric hydroperoxide species featuring a proximal H-bonding substituent.

ABSTRACT: At -90 °C in acetone, a stable hydroperoxo complex [(BA)Cu(II)OOH](+) (2) (BA, a tetradentate N(4) ligand possessing a pendant -N(H)CH(2)C(6)H(5) group) is generated by reacting [(BA)Cu(II)(CH(3)COCH(3))](2+) with only 1 equiv of H(2)O(2)/Et(3)N. The exceptional stability of 2 is ascribed to internal H-bonding. Species 2 is also generated in a manner not previously known in copper chemistry, by adding 1.5 equiv of H(2)O(2) (no base) to the cuprous complex [(BA)Cu(I)](+). The broad implications for this finding are discussed. Species 2 slowly converts to a ?-1,2-peroxodicopper(II) analogue (3) characterized by UV-vis and resonance Raman spectroscopies. Unlike a close analogue not possessing internal H-bonding, 2 affords no oxidative reactivity with internal or external substrates. However, 2 can be protonated to release H(2)O(2), but only with HClO(4), while 1 equiv Et(3)N restores 2.

SUBMITTER: Kim S

PROVIDER: S-EPMC3513638 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Coordination chemistry and reactivity of a cupric hydroperoxide species featuring a proximal H-bonding substituent.

Kim Sunghee S Saracini Claudio C Siegler Maxime A MA Drichko Natalia N Karlin Kenneth D KD

Inorganic chemistry 20121115 23

At -90 °C in acetone, a stable hydroperoxo complex [(BA)Cu(II)OOH](+) (2) (BA, a tetradentate N(4) ligand possessing a pendant -N(H)CH(2)C(6)H(5) group) is generated by reacting [(BA)Cu(II)(CH(3)COCH(3))](2+) with only 1 equiv of H(2)O(2)/Et(3)N. The exceptional stability of 2 is ascribed to internal H-bonding. Species 2 is also generated in a manner not previously known in copper chemistry, by adding 1.5 equiv of H(2)O(2) (no base) to the cuprous complex [(BA)Cu(I)](+). The broad implications f ...[more]

PMID: 23153187

Similar Datasets

Intramolecular Hydrogen Bonding Enhances Stability and Reactivity of Mononuclear Cupric Superoxide Complexes.

Project description:[(L)CuII(O2•-)]+ (i.e., cupric-superoxo) complexes, as the first and/or key reactive intermediates in (bio)chemical Cu-oxidative processes, including in the monooxygenases PHM and D?M, have been systematically stabilized by intramolecular hydrogen bonding within a TMPA ligand-based framework. Also, gradual strengthening of ligand-derived H-bonding dramatically enhances the [(L)CuII(O2•-)]+ reactivity toward hydrogen-atom abstraction (HAA) of phenolic O-H bonds. Spectroscopic properties of the superoxo complexes and their azido analogues, [(L)CuII(N3-)]+, also systematically change as a function of ligand H-bonding capability.

| S-EPMC6217813 | biostudies-literature

Amine oxidative N-dealkylation via cupric hydroperoxide Cu-OOH homolytic cleavage followed by site-specific fenton chemistry.

Project description:Copper(II) hydroperoxide species are significant intermediates in processes such as fuel cells and (bio)chemical oxidations, all involving stepwise reduction of molecular oxygen. We previously reported a Cu(II)-OOH species that performs oxidative N-dealkylation on a dibenzylamino group that is appended to the 6-position of a pyridyl donor of a tripodal tetradentate ligand. To obtain insights into the mechanism of this process, reaction kinetics and products were determined employing ligand substrates with various para-substituent dibenzyl pairs (-H,-H; -H,-Cl; -H,-OMe, and -Cl,-OMe), or with partially or fully deuterated dibenzyl N-(CH2Ph)2 moieties. A series of ligand-copper(II) bis-perchlorate complexes were synthesized, characterized, and the X-ray structures of the -H,-OMe analogue were determined. The corresponding metastable Cu(II)-OOH species were generated by addition of H2O2/base in acetone at -90 °C. These convert (t1/2 ? 53 s) to oxidatively N-dealkylated products, producing para-substituted benzaldehydes. Based on the experimental observations and supporting DFT calculations, a reaction mechanism involving dibenzylamine H-atom abstraction or electron-transfer oxidation by the Cu(II)-OOH entity could be ruled out. It is concluded that the chemistry proceeds by rate limiting Cu-O homolytic cleavage of the Cu(II)-(OOH) species, followed by site-specific copper Fenton chemistry. As a process of broad interest in copper as well as iron oxidative (bio)chemistries, a detailed computational analysis was performed, indicating that a Cu(I)OOH species undergoes O-O homolytic cleavage to yield a hydroxyl radical and Cu(II)OH rather than heterolytic cleavage to yield water and a Cu(II)-O(•-) species.

| S-EPMC4482616 | biostudies-literature

Substituent Effects on the Coordination Chemistry of Metal-Binding Pharmacophores.

Project description:A combination of XAS, UV-vis, NMR, and EPR was used to examine the binding of a series of α-hydroxythiones to CoCA. All three appear to bind preferentially in their neutral, protonated forms. Two of the three clearly bind in a monodentate fashion, through the thione sulfur alone. Thiomaltol (TM) appears to show some orientational preference, on the basis of the NMR, while it appears that thiopyromeconic acid (TPMA) retains rotational freedom. In contrast, allothiomaltol (ATM), after initially binding in its neutral form, presumably through the thione sulfur, forms a final complex that is five-coordinate via bidentate coordination of ATM. On the basis of optical titrations, we speculate that this may be due to the lower initial pKa of ATM (8.3) relative to those of TM (9.0) and TPMA (9.5). Binding through the thione is shown to reduce the hydroxyl pKa by ∼0.7 pH unit on metal binding, bringing only ATM's pKa close to the pH of the experiment, facilitating deprotonation and subsequent coordination of the hydroxyl. The data predict the presence of a solvent-exchangeable proton on TM and TPMA, and Q-band 2-pulse ESEEM experiments on CoCA + TM suggest that the proton is present. ESE-detected EPR also showed a surprising frequency dependence, giving only a subset of the expected resonances at X-band.

| S-EPMC6489498 | biostudies-literature

Impact of Intramolecular Hydrogen Bonding on the Reactivity of Cupric Superoxide Complexes with O-H and C-H Substrates.

Project description:The dioxygen reactivity of a series of TMPA-based copper(I) complexes (TMPA=tris(2-pyridylmethyl)amine), with and without secondary-coordination-sphere hydrogen-bonding moieties, was studied at -135 °C in 2-methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H-bonded [( ( X 1 ) ( X 2 ) TMPA)CuII (O2 .- )]+ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( ( X 1 ) ( X 2 ) TMPA)CuII (N3 - )]+ azido analogues were compared, and the O2 .- reactivity of ligand-CuI complexes when an H-bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C-H bond-dissociation energies is observed, correlating with the number and strength of the H-bonding groups.

| S-EPMC6878127 | biostudies-literature

Cupric superoxo-mediated intermolecular C-H activation chemistry.

Project description:The new cupric superoxo complex [LCu(II)(O(2)(•-))](+), which possesses particularly strong O-O and Cu-O bonding, is capable of intermolecular C-H activation of the NADH analogue 1-benzyl-1,4-dihydronicotinamide (BNAH). Kinetic studies indicated a first-order dependence on both the Cu complex and BNAH with a deuterium kinetic isotope effect (KIE) of 12.1, similar to that observed for certain copper monooxygenases.

| S-EPMC3091961 | biostudies-literature

A Thioether-Ligated Cupric Superoxide Model with Hydrogen Atom Abstraction Reactivity.

Project description:The central role of cupric superoxide intermediates proposed in hormone and neurotransmitter biosynthesis by noncoupled binuclear copper monooxygenases like dopamine-β-monooxygenase has drawn significant attention to the unusual methionine ligation of the CuM ("CuB") active site characteristic of this class of enzymes. The copper-sulfur interaction has proven critical for turnover, raising still-unresolved questions concerning Nature's selection of an oxidizable Met residue to facilitate C-H oxygenation. We describe herein a model for CuM, [(TMGN3S)CuI]+ ([1]+), and its O2-bound analog [(TMGN3S)CuII(O2•-)]+ ([1·O2]+). The latter is the first reported cupric superoxide with an experimentally proven Cu-S bond which also possesses demonstrated hydrogen atom abstraction (HAA) reactivity. Introduction of O2 to a precooled solution of the cuprous precursor [1]B(C6F5)4 (-135 °C, 2-methyltetrahydrofuran (2-MeTHF)) reversibly forms [1·O2]B(C6F5)4 (UV/vis spectroscopy: λmax 442, 642, 742 nm). Resonance Raman studies (413 nm) using 16O2 [18O2] corroborated the identity of [1·O2]+ by revealing Cu-O (446 [425] cm-1) and O-O (1105 [1042] cm-1) stretches, and extended X-ray absorption fine structure (EXAFS) spectroscopy showed a Cu-S interatomic distance of 2.55 Å. HAA reactivity between [1·O2]+ and TEMPO-H proceeds rapidly (1.28 × 10-1 M-1 s-1, -135 °C, 2-MeTHF) with a primary kinetic isotope effect of kH/kD = 5.4. Comparisons of the O2-binding behavior and redox activity of [1]+ vs [2]+, the latter a close analog of [1]+ but with all N atom ligation (i.e., N3S vs N4), are presented.

| S-EPMC8023764 | biostudies-literature

Synthesis and reactivity of cyclo-tetra(stibinophosphonium) tetracations: redox and coordination chemistry of phosphine-antimony complexes.

Project description:Reductive elimination of [R3PPR3]2+, [11(R)]2+, from the highly electrophilic SbIII centres in [(R3P)3Sb]3+, [8(R)]3+, gives SbI containing cations [(R3P)Sb]1+, [9(R)]1+, which assemble into frameworks identified as cyclo-tetra(stibinophosphonium) tetracations, [(R3P)4Sb4]4+, [10(R)]4+. A phosphine catalyzed mechanism is proposed for conversion of fluoroantimony complexes [(R3P)2SbF]2+, [7(R)]2+, to [10(R)]4+, and the characterization of key intermediates is presented. The results constitute evidence of a novel ligand activation pathway for phosphines in the coordination sphere of hard, electron deficient acceptors. Characterization of the associated reactants and products supports earlier, albeit less definitive, detection of analogous phosphine ligand activation in CuIII and TlIII complexes, demonstrating that these prototypical ligands can behave simultaneously as reducing agents and σ donors towards a variety of hard acceptors. The reactivity of the parent cyclo-tetra(stibinophosphonium) tetracation, [10(Me)]4+, is directed by high charge concentration and strong polarization of the P-Sb bonds. The former explains the observed facility for reductive elimination to yield elemental antimony and the latter enabled activation of P-Cl and P-H bonds to give phosphinophosphonium cations, [Me3PPR'2]1+, including the first example of an H-phosphinophosphonium, [(Me3P)P(H)R']1+, and 2-phosphino-1,3-diphosphonium cations, [(Me3P)2PR']2+. Exchange of a phosphine ligand in [10(Me)]4+ with [nacnac]1- gives [(Me3P)3Sb4(nacnac)]3+, [15(Me)]3+, and with dmap gives [(Me3P)3Sb4(dmap)]4+, [16]4+. The lability of P-Sb or Sb-Sb interactions in [10(Me)]4+ has also been illustrated by characterization of heteroleptically substituted derivatives featuring PMe3 and PEt3 ligands.

| S-EPMC5647858 | biostudies-literature

Lanthanide-porphyrin species as Kondo irreversible switches through tip-induced coordination chemistry.

Project description:Metallosupramolecular chemical protocols are applied to in situ design dysprosium porphyrin complexes on Au(111) by sequential deposition of 2H-4FTPP species and Dy, resulting in the production of premetallated Dy-2H-4FTPP, partially metallated Dy-1H-4FTPP and fully metallated Dy-0H-4FTPP complexes, as determined by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. A zero bias resonance is found in the Dy-2H-4FTPP species which, upon study of its spatial distribution and behavior with temperature, is assigned to a Kondo resonance resulting from an unpaired spin in the molecular backbone, featuring a Kondo temperature (TK) of ≈ 21 K. Notably, the Kondo resonance can be switched off by removing one hydrogen atom of the macrocycle through tip-induced voltage pulses with submolecular precision. The species with this Kondo resonance can be laterally manipulated illustrating the potential to assemble artificial Kondo lattices. Our study demonstrates that the pre-metallation of macrocycles by lanthanides and their controlled manipulation is a novel strategy to engineer in situ tunable Kondo nanoarchitectures, enhancing the potential of coordination chemistry for spintronics.

| S-EPMC8118200 | biostudies-literature

Substituted adenine quartets: interplay between substituent effect, hydrogen bonding, and aromaticity.

Project description:Adenine, one of the components of DNA/RNA helices, has the ability to form self-organizing structures with cyclic hydrogen bonds (A4), similar to guanine quartets. Here, we report a computational investigation of the effect of substituents (X = NO2, Cl, F, H, Me, and NH2) on the electronic structure of 9H-adenine and its quartets (A4-N1, A4-N3, and A4-N7). DFT calculations were used to show the relationships between the electronic nature of the substituents, strength of H-bonds in the quartets, and aromaticity of five- and six-membered rings of adenine. We demonstrated how the remote substituent X modifies the proton-donating properties of the NH2 group involved in the H-bonds within quartets and how the position of the substituent and its electronic nature affect the stability of the quartets. We also showed the possible changes in electronic properties of the substituent and aromaticity of adenine rings caused by tetramer formation. The results indicate that the observed relationships depend on the A4 type. Moreover, the same substituent can both strengthen and weaken intermolecular interactions, depending on the substitution position.

| S-EPMC9054646 | biostudies-literature

Experimental Quantum Chemistry: A Hammett-inspired Fingerprinting of Substituent Effects.

Project description:The quantum mechanically calculable Q descriptor is shown to be a potent quantifier of chemical reactivity in complex molecules - it shows a strong correlation to experimentally derived field effects in non-aromatic substrates and Hammett σm and σp parameters. Models for predicting substituent effects from Q are presented and applied, including on the elusive pentazolyl substituent. The presented approach enables fast computational estimation of substituent effects, and, in extension, medium-throughput screening of molecules and compound design. An experimental dataset is suggested as a candidate benchmark for aiding the general development and comparison of electronic structure analyses. It is here used to evaluate the experimental quantum chemistry (EQC) framework for chemical bonding analysis in larger molecules.

| S-EPMC8049055 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data