DFT calculated structures and IR spectra of the conformers of para-bromocalix[4]aryl derivatives

Molecular structures of the various conformers of para-bromocalix[4]aryl derivatives 1-4 were optimized using the DFT B3LYP calculation method. The total electronic and Gibbs free energies and normal vibrational frequencies of the different structures (CONE, partial cone (PACO), 1, 2-Alternate(1, 2-A) and 1, 3-Alternate(1, 3-A)) were calculated from the four kinds of para-bromocalix[4]aryl derivatives. The B3LYP/6-31G(d, p) calculations suggested the following: 1(PACO) is the most stable among four conformers of 1; 2(CONE) is the most stable among five conformers of 2; 3(PACO) is the most stable among four conformers of 3; 4(1, 3-A) is the most stable among four conformers of 4. All the most stable structures optimized by the B3LYP calculation method were in accordance with the experimental crystal structures of 1-4. The calculated IR spectra of the various conformers (CONE, PACO, 1, 2-A and 1, 3-A) of 1-4 were compared.