scholarly journals Combined FTIR Matrix Isolation and Density Functional Studies of Indole-3-Pyruvic Acid Molecule. Spectroscopic Evidence of Gas-Phase Tautomerism

2012 ◽  
Vol 2012 ◽  
pp. 1-11
Author(s):  
Luigi Bencivenni ◽  
Andrea Margonelli ◽  
Alessandro Mariani ◽  
Andrea Pieretti ◽  
Stella Nunziante Cesaro
Keyword(s):  
Vibrational Spectrum ◽  
Gas Phase ◽  
Pyruvic Acid ◽  
Density Functional Calculations ◽  
Spectroscopic Data ◽  
Density Functional ◽  
Matrix Isolation ◽  
Vapour Phase ◽  
Acid Molecule ◽  
Functional Studies

The vibrational spectrum of matrix-isolated indole-3-pyruvic acid has been studied aiming to obtain information about the structures of the stable vapour-phase forms of the molecule. Together with results from theoretical density functional calculations, the spectroscopic data enable to undertake an attribution for most of the observed bands. The FTIR spectrum of crystalline indole-3-pyruvic acid has been compared with that of matrix isolation study.

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.

Rate Coefficients for Intramolecular Homolytic Substitution of Oxyacyl Radicals at Sulfur

2013 ◽  
Vol 66 (3) ◽  
pp. 323 ◽  
Author(s):  
Heather M. Aitken ◽  
Sonia M. Horvat ◽  
Michelle L. Coote ◽  
Ching Yeh Lin ◽  
Carl H. Schiesser
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Gas Phase ◽  
Sulfur Atom ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Rate Coefficients ◽  
Energy Barriers ◽  
Tert Butyl ◽  
Homolytic Substitution

It is predicted on the basis of ab initio and density functional calculations that intramolecular homolytic substitution of oxyacyl radicals at the sulfur atom in ω-alkylthio-substituted radicals do not involve hypervalent intermediates. With tert-butyl as the leaving radical, free energy barriers ΔG‡ (G3(MP2)-RAD) for these reactions range from 45.8 kJ mol–1 for the formation of the five-membered cyclic thiocarbonate (8) to 56.7 kJ mol–1 for the formation of the six-membered thiocarbonate (9). Rate coefficients in the order of 104–106 s–1 and 101–104 s–1 for the formation of 8 and 9, respectively, at 353.15 K in the gas phase are predicted at the G3(MP2)-RAD level of theory.

A New Pathway for Activation of C - C and C - H Bonds by Transition Metals in the Gas Phase

2005 ◽  
Vol 58 (2) ◽  
pp. 82 ◽  
Author(s):  
Dongju Zhang ◽  
Ruoxi Wang ◽  
Rongxiu Zhu
Keyword(s):  
Transition Metals ◽  
Gas Phase ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Bond Activation ◽  
Level Density ◽  
Elimination Mechanism ◽  
Activation Of Hydrocarbons ◽  
High Level ◽  
H2 Elimination

C–H and C–C bond activation of hydrocarbons at metal centres are of fundamental importance in biochemistry, organometallic chemistry, and catalysis. The present work aims to search for novel mechanisms for activation of C–C and C–H bonds by transition metals in the gas phase. Using high-level density functional calculations, we systemically studied the reactions of Ti+, V+, and Fe+ with ethane, and proposed new pathways of C–C and C–H bond activation—concerted activation of C–C and C–H bonds, and 1,2-H2 elimination. These two pathways clearly differ from the general addition–elimination mechanism.

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