gNMR simulated 1H and proton-coupled 13C NMR spectra of substituted 3-nitropyridines. GIAO/DFT calculated values of proton and carbon chemical shifts and coupling constants

The magnitude of one bond and long-range coupling constants in 3-nitropyridine 1 and its derivatives 2–16 were determined from the proton-coupled 13C NMR spectra in CDCl3. The GIAO/DFT (Density Functional Theory/Gauge Including Atomic Orbitals) calculations on B3LYP/6-31+G(d,p)//6-31G(d) and B3LYP/6-311++G(d,p)//6-31G(d) optimized structures of 1–16 were employed for the determination of proton and carbon chemical shifts and coupling constants (JHHn and JCHn) and the calculated data compared with the experimental NMR data. The GIAO/DFT calculations, in conjugation with iterative simulations of the proton-coupled 13C NMR spectra using gNMR software, provide reliable values of JCNO2,Hn couplings, which could not be obtained from the proton-coupled 13C NMR spectra of 1–16 due to line broadening associated with quadruple relaxation involving the 14N nuclei and non-zero 13C–14N couplings.