Crystal structures and theoretical investigation of anti-/syn-2,4-diphenylpentane- and 2,4-di-p-tolylpentane-2,4-diols

Abstract

2,4-diphenylpentane- and 2,4-di-p-tolylpentane-2,4-diols were investigated employing experimental and density functional theory (DFT) method at B3LYP/6-31G (d) level. The structure of syn-2,4-di-p-tolylpentane-2,4-diol (2b) was characterized by X-ray diffraction and compared with the crystal structures of anti- and syn-2,4-diphenylpentane-2,4-diols (1a and 1b). X-ray diffraction indicates that inter and intra-molecular hydrogen bonds are formed in the crystal structures. There is π-π staking interaction in 1b and 2b. Good linear correlations and similar results are found between the experimental 1H and 13C NMR chemical shifts (δexp) and GIAO (Gauge Independent Atomic Orbital) method calculated magnetic isotropic shielding tensors (δcalc). HOMO and LUMO molecular orbitals were calculated at the same levels with the different results. UV-vis absorption spectra of the compounds were recorded in EtOH, MeCN, n-BuOH and cyclohexane with different dielectric constants. It is found that the solvent effect is obvious when ɛ is 24.85(EtOH), 35.69(MeCN) and it is weak when ɛ is decreased to 17.33(n-BuOH), 1.18 (cyclohexane).