Density functional based studies of transition states and barriers for hydrogen exchange and abstraction reactions

1995 ◽  
Vol 102 (23) ◽  
pp. 9345-9349 ◽  
Author(s):  
Dirk Porezag ◽  
Mark R. Pederson
Keyword(s):  
Density Functional ◽  
Hydrogen Exchange ◽  
Transition States

scholarly journals Benchmarking the Fluxional Processes of Organometallic Piano-Stool Complexes

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2310
Author(s):  
Nathan C. Frey ◽  
Eric Van Dornshuld ◽  
Charles Edwin Webster
Keyword(s):  
Transition Metals ◽  
Density Functional ◽  
Chemical Shifts ◽  
Transition States ◽  
Electronic Energy ◽  
Basis Set ◽  
Composite Approach ◽  
Temperature Regimes ◽  
Correlation Consistent Composite Approach ◽  
Correlation Consistent

The correlation consistent Composite Approach for transition metals (ccCA-TM) and density functional theory (DFT) computations have been applied to investigate the fluxional mechanisms of cyclooctatetraene tricarbonyl chromium ((COT)Cr(CO)3) and 1,3,5,7-tetramethylcyclooctatetraene tricarbonyl chromium, molybdenum, and tungsten ((TMCOT)M(CO)3 (M = Cr, Mo, and W)) complexes. The geometries of (COT)Cr(CO)3 were fully characterized with the PBEPBE, PBE0, B3LYP, and B97-1 functionals with various basis set/ECP combinations, while all investigated (TMCOT)M(CO)3 complexes were fully characterized with the PBEPBE, PBE0, and B3LYP methods. The energetics of the fluxional dynamics of (COT)Cr(CO)3 were examined using the correlation consistent Composite Approach for transition metals (ccCA-TM) to provide reliable energy benchmarks for corresponding DFT results. The PBE0/BS1 results are in semiquantitative agreement with the ccCA-TM results. Various transition states were identified for the fluxional processes of (COT)Cr(CO)3. The PBEPBE/BS1 energetics indicate that the 1,2-shift is the lowest energy fluxional process, while the B3LYP/BS1 energetics (where BS1 = H, C, O: 6-31G(d′); M: mod-LANL2DZ(f)-ECP) indicate the 1,3-shift having a lower electronic energy of activation than the 1,2-shift by 2.9 kcal mol−1. Notably, PBE0/BS1 describes the (CO)3 rotation to be the lowest energy process, followed by the 1,3-shift. Six transition states have been identified in the fluxional processes of each of the (TMCOT)M(CO)3 complexes (except for (TMCOT)W(CO)3), two of which are 1,2-shift transition states. The lowest-energy fluxional process of each (TMCOT)M(CO)3 complex (computed with the PBE0 functional) has a ΔG‡ of 12.6, 12.8, and 13.2 kcal mol−1 for Cr, Mo, and W complexes, respectively. Good agreement was observed between the experimental and computed 1H-NMR and 13C-NMR chemical shifts for (TMCOT)Cr(CO)3 and (TMCOT)Mo(CO)3 at three different temperature regimes, with coalescence of chemically equivalent groups at higher temperatures.

THE H2NO POTENTIAL ENERGY SURFACE EXPLORED WITH HIGH LEVEL AB INITIO AND DENSITY FUNCTIONAL THEORY METHODS

2007 ◽  
Vol 06 (03) ◽  
pp. 549-562
Author(s):  
ABRAHAM F. JALBOUT
Keyword(s):  
Density Functional Theory ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Hybrid Methods ◽  
Transition States ◽  
Basis Set ◽  
Functional Theory ◽  
High Level

The transition states for the H 2 NO decomposition and rearrangements mechanisms have been explored by the CBS-Q method or by density functional theory. Six transition states were located on the potential energy surface, which were explored with the Quadratic Complete Basis Set (CBS-Q) and Becke's one-parameter density functional hybrid methods. Interesting deviations between the CBS-Q results and the B1LYP density functional theory lead us to believe that further study into this system is necessary. In the efforts to further assess the stabilities of the transition states, bond order calculations were performed to measure the strength of the bonds in the transition state.

scholarly journals Solid state catalytic hydrogen exchange for deuterium in cycloprolylglycine

2019 ◽  
Vol 484 (3) ◽  
pp. 307-311
Author(s):  
A. K. Dadayan ◽  
Yu. A. Borisov ◽  
E. V. Bocharov ◽  
Yu. A. Zolotarev ◽  
I. Yu. Nagaev ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Solid State ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Density Functional ◽  
Hydrogen Exchange ◽  
Functional Theory ◽  
Catalytic Hydrogen ◽  
Spillover Hydrogen ◽  
High Stereoselectivity

The reaction of spillover hydrogen (SH) with cyclopropylglycine (cPG) in high-temperature solid-state catalytic hydrogen isotope exchange (HTCIE) has been studied experimentally and using density functional theory (DFT). NMR spectroscopy and mass spectrometry have shown a high regioselectivity and stereoselectivity for the reaction of spillover hydrogen with cPG fragments. The Gly fragment has been shown to be the most reactive in HTCIE, for which high stereoselectivity of substitution of hydrogen by deuterium has been demonstrated.

A Topological Study of the Transition States of the Hydrogen Exchange and Dehydrogenation Reactions of Methane on a Zeolite Cluster

2001 ◽  
Vol 105 (29) ◽  
pp. 7079-7084 ◽  
Author(s):  
N. B. Okulik ◽  
R. Pis Diez ◽  
A. H. Jubert ◽  
P. M. Esteves ◽  
C. J. A. Mota
Keyword(s):  
Hydrogen Exchange ◽  
Transition States ◽  
Dehydrogenation Reactions

Performance of Density Functional for Transition States

1999 ◽  
pp. 20-32 ◽  
Author(s):  
D. R. Salahub ◽  
S. Chrétien ◽  
A. Milet ◽  
E. I. Proynov
Keyword(s):  
Density Functional ◽  
Transition States
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