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 ( J HH n and J CH n ) 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 J C NO2,H n 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.