Quantum Mechanical Calculations of Conformationally Relevant 1H and 13C NMR Chemical Shifts of N-, O-, and S-Substituted Calixarene Systems

QM GIAO calculations of 13C and 1H chemical shift values of the ArCH2Ar group in N-, O-, and S-substituted calixarene systems were performed with a hybrid DFT functional MPW1PW91 and 6-31G(d,p) basis set. A good reproduction of experimental data was obtained for some representative calixarenes and for a series of simplified calixarene models. This allowed the derivation of chemical shift surfaces versus ϕ and χ dihedral angles. The applicability of chemical shift surfaces in the study of calixarene conformational features is illustrated.