Guanfan Chen

A QSPR correlation on the 13C NMR chemical shifts of bridge carbons for different series of aromatic Schiff bases

Nuclear magnetic resonance (NMR) spectroscopy has attracted immense attention because of playing an important role in not only determining molecular structures but also explaining reaction mechanisms, molecular dynamics, chemical equilibrium, etc. With the advancement of NMR technology, there is more and more NMR experimental information obtained. Consequently, many efforts have been made to understand relationships between molecular structures and different kinds of NMR chemical shifts. In investigations on C NMR of specific carbons for aromatic systems with a changing substituent, the chemical shift (δC) values are usually calculated with the single substituent parameter treatment or the dual substituent parameter treatment, [15] shown as Eqns (1) and (2), where σ, σF (or σI) and σR are the Hammett parameter, inductive parameter, and resonance parameter, respectively, and C is a constant.