Experimental and DFT evaluation of the 1H and 13C NMR chemical shifts for calix[4]arenes

Abstract The density functional theory is employed to determine the efficiency of 11 exchange-correlation (XC) functionals to compute the 1 H and 13 C NMR chemical shifts of p -tert-butylcalix[4]arene (ptcx4, R 1  = C(CH 3 ) 3 ) and congeners using the 6-31G(d,p) basis set. The statistical analysis shows that B3LYP, B3PW91 and PBE1PBE are the best XC functionals for the calculation of 1 H chemical shifts. Moreover, the best results for the 13 C chemical shifts are obtained using the LC-WPBE, M06-2X and w B97X-D functionals. The performance of these XC functionals is tested for three other calix[4]arenes: p -sulfonic acid calix[4]arene ( sfxcx4 - R 1  = SO 3 H), p -nitro-calix[4]arene ( ncx4 , R 1  = NO 2 ) and calix[4]arene ( cx4 - R 1  = H). For 1 H chemical shifts B3LYP, B3PW91 and PBE1PBE yield similar results, although B3PW91 shows more consistency in the calculated error for the different structures. For 13 C NMR chemical shifts, the XC functional that stood out as best is LC-WPBE. Indeed, the three functionals selected for each of 1 H and 13 C show good accuracy and can be used in future studies involving the prediction of 1 H and 13 C chemical shifts for this type of compounds.