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: N-(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 (1)H NMR chemical shifts correlate well with differences in association constants of several host-guest complexes.