Can Nitriles Be Stronger Bases Than Proton Sponges in the Gas Phase? A Computational Analysis

2015 ◽  
Vol 119 (29) ◽  
pp. 8225-8236 ◽  
Author(s):  
Ewa D. Raczyńska ◽  
Mariusz Makowski ◽  
Pierre-Charles Maria ◽  
Jean-François Gal
Keyword(s):  
Gas Phase ◽  
Computational Analysis ◽  
Proton Sponges

Sind Metalloprotonencryptanden möglich? – DFT-Studie zur Protonenaffinität von [2.2.2]-analogen Metallocryptanden / Can Metallocryptands act as Proton Cages? – DFT Study of Proton Affinity in [2.2.2]-analogousMetallocryptands Sind Metalloprotonencryptanden m¨oglich? – DFT-Studie zur Protonenaffinit¨at von [2.2.2]-analogen Metallocryptanden

2010 ◽  
Vol 65 (3) ◽  
pp. 231-s261 ◽  
Author(s):  
Ralph Puchta ◽  
Andreas Scheurer
Keyword(s):  
Coordination Chemistry ◽  
Gas Phase ◽  
Proton Affinity ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Dft Study ◽  
Proton Sponges

Based on density functional calculations (RB3LYP/LANL2DZp) the bicyclic metallocryptand [Pd3(L2)2] [(L2)3−: 1,1´ ,1´´-nitrilotris(5,5-dimethylhexane-2,4-dione trianion)] shows the same high gas-phase basicity (−257.1 kcal mol−1) as Lehn’s [2.2.2] cryptand (−254.4 kcal mol−1). This illustrates that the concept of metallotopomers adopted by Saalfrank et al. can be applied to design proton sponges as well as proton cryptands by metallosupramolecular coordination chemistry. The slightly higher gas-phase proton affinity of [Pd3(L2)2] compared to [2.2.2] can be attributed to the smaller cavity in the metallotopomer.

scholarly journals Trichloro(Dinitrogen)platinate(II)

2020 ◽  
Author(s):  
Gilian T. Thomas ◽  
Sofia Donnecke ◽  
Irina Paci ◽  
J Scott McIndoe
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Ion Mobility ◽  
Computational Analysis ◽  
Ionization Mass ◽  
Organometallic Complex ◽  
Polar Solvents ◽  
Dinitrogen Complexes ◽  
Ion Mobility Spectroscopy ◽  
Platinum Salt

<p>Zeise’s salt, [PtCl<sub>3</sub>(H<sub>2</sub>C=CH<sub>2</sub>)]<sup>–</sup><sub>,</sub> is the oldest known organometallic complex, featuring ethylene strongly bound to a platinum salt. Many derivatives are known, but none involving dinitrogen, and indeed dinitrogen complexes are unknown for both platinum and palladium. Electrospray ionization mass spectrometry of K<sub>2</sub>[PtCl<sub>4</sub>] solutions generate strong ions corresponding to [PtCl<sub>3</sub>(N<sub>2</sub>)]<sup>–</sup>, whose identity was confirmed through ion mobility spectroscopy and MS/MS experiments that proved it to be distinct from its isobaric counterparts [PtCl<sub>3</sub>(C<sub>2</sub>H<sub>4</sub>)]<sup>–</sup> and [PtCl<sub>3</sub>(CO)]<sup>–</sup>. Computational analysis established a gas-phase platinum-dinitrogen bond strength of 116 kJ mol<sup>-1</sup>, substantially weaker than the ethylene and carbon monoxide analogues but stronger than for polar solvents such as water, methanol and dimethylformamide, and strong enough that the calculated N-N bond length of 1.119 Å represents weakening to a degree typical of isolated dinitrogen complexes. </p>

scholarly journals Trichloro(Dinitrogen)platinate(II)

2020 ◽  
Author(s):  
Gilian T. Thomas ◽  
Sofia Donnecke ◽  
Irina Paci ◽  
J Scott McIndoe
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Ion Mobility ◽  
Computational Analysis ◽  
Ionization Mass ◽  
Organometallic Complex ◽  
Polar Solvents ◽  
Dinitrogen Complexes ◽  
Ion Mobility Spectroscopy ◽  
Platinum Salt

<p>Zeise’s salt, [PtCl<sub>3</sub>(H<sub>2</sub>C=CH<sub>2</sub>)]<sup>–</sup><sub>,</sub> is the oldest known organometallic complex, featuring ethylene strongly bound to a platinum salt. Many derivatives are known, but none involving dinitrogen, and indeed dinitrogen complexes are unknown for both platinum and palladium. Electrospray ionization mass spectrometry of K<sub>2</sub>[PtCl<sub>4</sub>] solutions generate strong ions corresponding to [PtCl<sub>3</sub>(N<sub>2</sub>)]<sup>–</sup>, whose identity was confirmed through ion mobility spectroscopy and MS/MS experiments that proved it to be distinct from its isobaric counterparts [PtCl<sub>3</sub>(C<sub>2</sub>H<sub>4</sub>)]<sup>–</sup> and [PtCl<sub>3</sub>(CO)]<sup>–</sup>. Computational analysis established a gas-phase platinum-dinitrogen bond strength of 116 kJ mol<sup>-1</sup>, substantially weaker than the ethylene and carbon monoxide analogues but stronger than for polar solvents such as water, methanol and dimethylformamide, and strong enough that the calculated N-N bond length of 1.119 Å represents weakening to a degree typical of isolated dinitrogen complexes. </p>

scholarly journals Structure of isolated tyrosyl-glycyl-glycine tripeptide. A comparative conformational study with peptides containing an aromatic ring

2010 ◽  
Vol 8 (3) ◽  
pp. 566-575 ◽  
Author(s):  
Exequiel Barrera Guisasola ◽  
Marcelo Masman ◽  
Ricardo Enriz ◽  
Ana Rodríguez
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
Computational Analysis ◽  
Energy Surface ◽  
Side Chain ◽  
Small Peptides ◽  
Peptide Backbone ◽  
X Ray ◽  
Backbone Conformation ◽  
Glycyl Glycine

AbstractThe potential energy surface (PES) of tyrosyl-glycyl-glycine (YGG) tripeptide in solution was explored using EDMC (Electrostatically Driven Monte Carlo) and in the gas-phase by means of ab initio quantum chemical calculations. The theoretical computational analysis revealed that this tripeptide possesses a significant molecular flexibility. A C7 backbone conformation was the most energetically preferred for the central Gly residue, using both methodologies. Some new stable conformers that have not been previously reported were identified in the gas phase as well. This study points out the interplay of backbone and side-chain contributions in determining the relative stabilities of energy minima. In addition, the peptide backbone of YGG was compared with other small peptides containing aromatic side-chains (Phe-Gly-Gly and Trp-Gly-Gly). The comparison with experimental X-ray results was also satisfactory.

scholarly journals The Sn2 Reaction: A Theoretical-Computational Analysis of a Simple and Very Interesting Mechanism

Proceedings ◽  
2019 ◽  
Vol 41 (1) ◽  
pp. 81
Author(s):  
Matías Capurso ◽  
Rodrigo Gette ◽  
Gabriel Radivoy ◽  
Viviana Dorn
Keyword(s):  
Gas Phase ◽  
Computational Analysis ◽  
Bond Distance ◽  
Atomic Charge ◽  
Reaction Rates ◽  
Basis Set ◽  
Dft Methods ◽  
Process Gas ◽  
Sn2 Reaction ◽  
Leaving Group

Bimolecular nucleophilic substitution (SN2) reaction is one of the most frequently processes chosen as model mechanism to introduce undergraduate chemistry students to computational chemistry methodology. In this work, we performed a computational analysis for the ionic SN2 reaction, where the nucleophile charged (X−; X=F, Cl, Br, I) attacks the carbon atom of the substrate (CH3Cl) through a backside pathway, and simultaneously, the leaving group is displaced (Cl−). The calculations were performed applying DFT methods with the Gaussian09 program, the B3LYP functional, the 6-31+G* basis set for all atoms except iodine (6-311G*), and the solvents effects (acetonitrile and cyclohexane) were evaluated with the PCM model. We evaluated the potential energy surface (PES) for the mentioned reaction considering the reactants, the formation of an initial complex between the nucleophile and the substrate, the transition state, a final complex where the leaving group is still bound to the substrate and the products. We analyzed the atomic charge (ESP) and the bond distance throughout the process. Gas phase and solvent studies were performed in order to analyze the solvation effects on the reactivity of the different nucleophiles. We observed that increasing solvent polarity, decreases reaction rates. On the other hand, we thought it would be enriching, to carry out a reactivity analysis from the point of view of molecular orbitals. Therefore, we analyzed the MOs HOMO and the MOs LUMO of the different stationary states on PES, both in a vacuum (gas phase) and in acetonitrile as the solvent.

Aplicyanins – brominated natural marine products with superbasic character

2016 ◽  
Vol 71 (8) ◽  
pp. 883-889 ◽  
Author(s):  
Marina D. Kostić ◽  
Vera M. Divac ◽  
Basam M. Alzoubi ◽  
Ralph Puchta
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
Proton Affinities ◽  
Chemical Methods ◽  
Nucleus Independent Chemical Shift ◽  
Quantum Chemical Methods ◽  
Acetyl Group ◽  
Marine Products ◽  
Nics Calculations ◽  
Proton Sponges

AbstractBy using quantum chemical methods (B3LYP/6-311+G(2df,p)//B3LYP/6-31G(d)), we investigated the structures of aplicyanin A, aplicyanin B, aplicyanin C, aplicyanin D, aplicyanin E, and aplicyanin F along with their protonated structures. The calculated gas phase proton affinities of aplicyanin A, aplicyanin C, and aplicyanin E are around –250 kcal mol−1 and therefore more than 10 kcal mol−1 higher as in typical proton sponges such as 1,8-bis(dimethylamino)naphthalene. The compounds aplicyanin B, aplicyanin D, and aplicyanin F show reduced proton affinities of approximately –240 kcal mol−1 because of the acetyl group being conjugated with the imine N=C moiety. Nucleus-independent chemical shift (NICS) calculations on the same level of theory do not show any peculiarities, and a reasonable correlation between the toxicity of aplicyanins and the gas phase proton affinity is not observed.

Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

1968 ◽  
Vol 26 ◽  
pp. 292-293
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman ◽  
Peter L. Ramos
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Gas Phase ◽  
Absolute Temperature ◽  
Residual Gas ◽  
Gas Reactions ◽  
Image Position ◽  
The Right ◽  
Water Gas ◽  
Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

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