¹H and ¹³C chemical shift–structure effects in anhydrous β-caffeine and four caffeine–diacid cocrystals probed by solid-state NMR experiments and DFT calculations

Abstract

By using density functional theory (DFT) calculations, we refined the H atom positions in the structures of β-caffeine (C), α-oxalic acid (OA; (COOH)₂), α-(COOH)₂⋅2H₂O, β-malonic acid (MA), β-glutaric acid (GA),...