Predicting experimental complexation-induced changes in 1H NMR chemical shift for complexes between zinc-porphyrins and amines using the ab initio/GIAO-HF methodology

Ab initio calculations were carried out on zinc-porphyrins complexed to several amines: M(3,5-dimethyl-pyridin-4-yl)-formamide, 1,4-diazabiciclo-[2.2.2]octane (DABCO), and 1-azabiciclo[2.2.2]octane (quinuclidine). The proton chemical shifts of these complexes were calculated ab initio at the GIAO-HF/6-311G*//HF/3-21G level of theory, and the obtained values agree satisfactorily with experimental results. The complexation-induced changes in H-1 NMR chemical shifts correlate well with differences in association constants of several host-guest complexes.