Search results for "NCT"

Computational study of the spin-forbidden H 2 oxidative addition to 16-electron Fe(0) complexes

2003

International audience; The spin-forbidden oxidative addition of H2 to Fe(CO)4, Fe(PH3)4, Fe(dpe)2 and Fe(dmpe)2 [dpe = H2PCH2CH2PH2, dmpe = (CH3)2PCH2CH2P(CH3)2] has been investigated by density functional theory using a modified B3PW91 functional. All 16-electron fragments are found to adopt a spin triplet ground state. The H2 addition involves a spin crossover in the reagents region of configurational space, at a significantly higher energy relative to the triplet dissociation asymptote and, for the case of Fe(CO)4·H2, even higher than the singlet dissociation asymptote. After crossing to the singlet surface, the addition proceeds directly to the classical cis-dihydride product. Only for…

Modellmembranen auf Oberflächen. Verankert und doch mobil

2008

Membranmodelle, die auf Festkorperoberflachen verankert sind, ermoglichen es, elektrische Verfahren sowie oberflachenanalytische und abbildende Methoden einzusetzen. So kann mit Membranen auf Oberflachen die laterale Organisation von Lipiden und Proteinen bis in den Nanometerbereich hinein visualisiert werden. Gleichzeitig sind diese Membranen sehr stabil und damit attraktiv fur verschiedene Bereiche der Biosensorik. Durch eine individuelle Adressierung kleinster mikrometergroser Membranareale mit verschiedenen Lipidkompositionen ist es moglich geworden, die Bindung von Proteinen an funktionale Membranen auf kleinstem Raum zu quantifizieren und zu parallelisieren. Fur die Untersuchung von T…

Novel Stannatrane N(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu and Related Oligonuclear Tin(IV) Oxoclusters. Two Isomers in One Crystal

2016

The syntheses of the alkanolamine N(CH2CMe2OH)2(CMe2CH2OH) (1), of the stannatrane N(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu (2), and of the trinuclear tin oxocluster 3 consisting of the two isomers [(μ3-O)(O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3a) and [(μ3-O)(μ3-O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3b) as well as the isolation of a few crystals of the hexanuclear tin oxocluster [LSnOSn(OH)3LSnOH]2 [L = N(CH2CMe2O)2(CMe2CH2O)] (4) are reported. The compounds were characterized by 1H, 13C, 15N, and 119Sn (1–3) nuclear magnetic resonance and infrared spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction analysis (1–4). A graph set analysis was performed for compoun…

Exploring the Chemoselectivity towards Cysteine Arylation by Cyclometallated Au III Compounds: New Mechanistic Insights

2020

To gain more insight into the factors controlling the efficient cysteine arylation by cyclometalated Au(III) complexes, the reaction between selected gold compounds and different peptides was investigated by high‐resolution liquid chromatography electrospray ionization mass spectrometry (HR‐LC‐ESI‐MS). The deducted mechanisms of C–S cross‐coupling, also supported by density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations, evidenced the key role of secondary peptidic gold binding sites in favouring the process of reductive elimination.

2020

The course of organic chemical reactions is efficiently modelled through the concepts of “electrophiles” and “nucleophiles” (meaning electron-seeking and nucleus-seeking reactive species). On the one hand, an advanced approach of the correlation of the nucleophilicity parameters N and electrophilicity E has been delivered from the linear free energy relationship log k (20 °C) = s(N + E). On the other hand, the general influence of the solvent mixtures, which are very often employed in preparative synthetic chemistry, has been poorly explored theoretically and experimentally, to date. Herein, we combined experimental and theoretical studies of the solvent influence on pyrrolidine nucleophili…

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.

Theoretical search for very short metal-actinide bonds: NUIr and isoelectronic systems.

2004

, respectively. These analogues provide anexample ofthe isolobal principle, now without any outsideligands onthePt atom,asituation describedasits “autogenicisolobality”. These systems have multiple C Pt bonds. Theisolobal principle of Hoffmann refers to the similar chemicalbehaviorofansphybridandametalatomwithligands,-ML

Chiral footprint of the ligand layer in the all-alkynyl-protected gold nanocluster Au144(CCPhF)60

2019

The electronic structure and chiroptical properties of the recently isolated and structurally characterized all-alkynyl-protected gold nanocluster Au144(CCPhF)60 were analyzed via density functional theory (DFT) computations and compared to those of the structurally similar all-thiolate-protected Au144(SCH2Ph)60. While DFT predicts very strong CD signals of similar strength for both clusters, the origins of chiroptical activity are markedly different. The chiral response of Au144(CCPhF)60 originates only from the footprint of the outermost gold-ligand layer of 30 FPhCC-Au-CCPhF units covering an achiral Ih-symmetric Au114 core whereas the Au114 core of the Au144(SCH2Ph)60 cluster has a chir…

Three‐in‐One Crystal: The Coordination Diversity of Zinc Polypyridine Complexes

2017

The synthesis, structural and photophysical properties of two novel zinc(II) complexes bearing the tridentate ddpd (N,N' dimethyl N,N' dipyridin 2 ylpyridine 2,6 diamine) ligand are presented. Structural investigations have been carried out by single crystal X-ray diffractometry, NMR spectroscopy and Density Functional Theory calculations, revealing a diverse coordination behavior depending on the counter ion. Spectroscopic (UV-VIS and emission spectroscopy) and theoretical techniques (density functional theory and time dependent DFT calculations) have been employed to explore the photophysical properties of the complexes.

A Molecular Electron Density Theory Study of the Role of the Copper Metalation of Azomethine Ylides in [3 + 2] Cycloaddition Reactions.

2018

The copper metalation of azomethine ylides (AYs) in [3 + 2] cycloaddition (32CA) reactions with electron-deficient ethylenes has been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) level, in order to shed light on the electronic effect of the metalation in the course of the reaction. Analysis of the Conceptual Density Functional Theory reactivity indices indicates that the metalation of AYs markedly enhances the nucleophilicity of these species given the anionic character of the AY framework. These 32CA reactions take place through stepwise mechanisms characterized by the formation of a molecular complex. Both nonmetalated and metalated 32CA reactions …