Electronic investigation and spectroscopic analysis using DFT with the long-range dispersion correction on the six lowest conformers of 2.2.3-trimethyl pentane

The conformational stability and internal rotation barriers, HOMO-LUMO gap and related properties, molecular static polarizability and hyperpolarizability parameters, and the NBO delocalization energies associated with the internal charge transfer (ICT) of 2.2.3-trimethylpentane in the ground state were carried out taking into account the long range dispersion correction through CAM-B3LYP and WB97XD levels at aug-cc-pvtz basis set. The six lowest conformations were differentiated by a deep and multiple spectroscopic investigation. The ultraviolet-visible (UV-Vis) absorption bands are assigned using molecular orbital data obtained by TD-WB97XD/aug-cc-pvtz calculations, and carbon C-13 NMR signal peaks have been assigned using GIAO-WB97XD/aug-cc-pvtz method. In addition, the normal mode calculations of the most and less stable conformers using a scaled force field in terms of non-redundant local symmetry coordinates have been confronted to the experimental vibrational spectra temperature dependency.