A multinuclear NMR spectral study of parent azoles and benzazoles: Experimental results and GIAO ab initio calculations

The C-13 and N-15 chemical shifts of twelve azoles and benzazoles have been determined in the solid state at room temperature and in methanol solution at 178 K. The experimental values were compared with the absolute shieldin gs calculated at the GLAO/B3LYP/6-31G* level. These comparisons show that s ome signals, 13C NMR but especially N-15 NMR, have to be corrected for hydr ogen bonds present in certain solvents and in the solid state. The linear r egressions are good enough to be used to predict some missing values.