Electronic and optical spectroscopic insights into 2.3.4-trimethyl pentane conformations by long-range corrected DFT calculations, experimental low frequency Raman and IR temperature sensitivity and scaled vibrational assignment

Conformational, spectroscopic and electronic behaviors of the 2.3.4-trimethyl pentane (2.3.4-TMP) molecule were carried out based on density functional theory DFT calculations with the long-range dispersion correction through CAM-B3LYP and WB97XD levels at aug-cc-pvtz basis set. Electronic properties of this molecule, such as HOMO-LUMO, molecular static polarizability, hyperpolarizability parameters, and molecular electrostatic surface potential (MEP) are also investigated. Deep and multiple spectroscopic investigations were used to characterize and differentiate between the stable conformers of 2.3.4-TMP. The experimental Fourier Transform infrared (FTIR) and Raman spectra were recorded. The spectral temperature sensitivity and scaled vibrational assignment for all the five lowest conformers A-E were carried out. A good correlation between experimental and calculated frequencies was observed with a standard deviation (RMS) of 4 cm -1 below 1500 cm -1 and 6 cm -1 for all other frequencies. 1 H and 13 C NMR spectra were simulated using GIAO-WB97XD/aug-cc-pvtz in Dimethyl Sulfoxide (DMSO) solvent, and the observed results agreed well with their experimental counterparts. Electronic transitions were analyzed using TD-WB97XD/aug-cc-pvtz simulated to have the UV-Vis spectra of the five conformers.