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Computational studies of the cone and 1,2,3 alternate calix[6]arene bis‐crown‐4 isomers: structures, NMR shifts, atomic charges, and steric compression
Author(s) -
Lawson Meghan N.,
Blanda Michael T.,
Staggs Sara J.,
Sederholm Lauren N.,
Easter David C.
Publication year - 2009
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1621
Subject(s) - chemistry , steric effects , computational chemistry , molecular geometry , bond length , dipole , chloroform , solvent effects , mulliken population analysis , solvent , atomic charge , ground state , molecule , density functional theory , stereochemistry , organic chemistry , atomic physics , physics
The cone and 1,2,3 alternate isomers of calix[6]arene bis‐crown‐4 were investigated computationally. Structural optimizations, energies, bond distances, and Mulliken charges were calculated by the application of the B3LYP/6‐31g(d) method/basis, followed by NMR calculations via both B3LYP/6‐31g(d) and HF/6‐31g(d). Calculations were completed at three different levels of imposed symmetry, and two calculations investigated the chloroform solvent effects. Better NMR results were obtained from HF/6‐31g(d) calculations that did not impose molecular symmetry constraints. Consideration of solvent effects improved ground state energies, but other improvements were minimal and not significant enough to justify the added computational expense of solvent calculations. Overall results are consistent with known experimental assignments and were valuable for assigning previously unknown NMR peaks. Net charges, electrostatic forces, and local dipoles – but not bond lengths – are strongly correlated to spectroscopic manifestations of steric compression. Copyright © 2009 John Wiley & Sons, Ltd.