NMR spectra, GIA and charge density calculations of five-membered aromatic heterocycles

Katritzky A. R., Akhmedov N. G., Doskocz J., Mohapatra P. P., Hall C. D., Guven A.

MAGNETIC RESONANCE IN CHEMISTRY, vol.45, no.7, pp.532-543, 2007 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 45 Issue: 7
  • Publication Date: 2007
  • Doi Number: 10.1002/mrc.1967
  • Journal Name: MAGNETIC RESONANCE IN CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.532-543
  • Keywords: NMR, coupling constants, GIAO, pyrrole, five-membered heterocycles, NUCLEAR-MAGNETIC-RESONANCE, SPIN COUPLING-CONSTANTS, CARBON CHEMICAL-SHIFTS, SOLID-STATE, ELECTROSTATIC POTENTIALS, C-13, PROTON, H-1, TAUTOMERISM, N-15
  • Anadolu University Affiliated: No

Abstract

The B3LYP/6-31+G(d) molecular geometry optimized structures of 17 five-membered heterocycles were employed together with the gauge including atomic orbitals (GIAO) density functional theory (DFT) method at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p) and B3LYP/6-311+G(2d,p) levels of theory for the calculation of proton and carbon chemicals shifts and coupling constants. The method of geometry optimization for pyrrole (1), N-methylpyrrole (2) and thiophene (7) using the larger 6-311++G(d,p) basis sets at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p), B3LYP/6-31+G(2d,p) and B3LYP/cc-pVTZ levels of theory gave little difference between calculated and experimental values of coupling constants. In general, the H-1 and C-13 chemical shifts for all compounds are in good agreement with theoretical calculations using the smaller 6-31 basis set. The values of (n)J(HH)(n = 3, 4, 5) and (rmn)J(CH)(n = 1, 2, 3, 4) were predicted well using the larger 6-31+G(d,p) and 6-311++G(d,p) basis sets and at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p), B3LYP/6-31+G(2d,2p) levels of theory. The computed atomic charges [Mulliken; Natural Bond Orbital Analysis (NBO); Merz-Kollman (MK); CHELP and CHELPG] for the B3LYP/6-311++G(d,p) geometry optimized structures of 1-17 were used to explore correlations with the experimental proton and carbon chemical shifts. Copyright (c) 2007 John Wiley & Sons, Ltd.