Premium
Strain energy minimization study of the mechanism of, and the barrier to, conformational interconversion in five‐membered diamine chelate rings
Author(s) -
Hambley Trevor W.
Publication year - 1987
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540080510
Subject(s) - diamine , chemistry , denticity , nitrogen inversion , crystallography , dihedral angle , energy minimization , stereochemistry , computational chemistry , molecule , nitrogen , polymer chemistry , crystal structure , organic chemistry , hydrogen bond
The method of Lagrangian multipliers is used to constrain torsion angles during molecular mechanics refinement for the purpose of plotting strain energy against a reaction coordinate. A complete two‐dimensional analysis of the conformational interconversion from δ‐ to λ‐[Co(ethane‐1,2‐diamine) (NH 3 ) 4 ] 3+ reveals a mechanism in which the transition state geometry has an envelope conformation and an inversion barrier of 15.7 kJ mol −1 . Substitution at the carbon atoms, variation of the metal‐nitrogen distance, and replacement of the amine ligands with bidentate amines only slightly alters the inversion barrier. Substitution at the nitrogen atoms of the bidentate ligand increases the inversion barrier significantly to 24.6 kJ mol −1 for (N,N,N′,N′‐tetramethylethane‐1,2‐diamine) [(NH 3 ) 4 ] 3+ .