Understanding spectroscopic features of trihexyltetradecylphosphonium chloride

Abstract

A comprehensive structural and spectroscopic characterization of trihexyltetradecylphosphonium chloride, [P-666(14)][Cl], was conducted by combining experiments with density functional theory (DFT) calculations. The structure of [P-666(14)][Cl] was first characterized experimentally by IR and NMR spectroscopies. Then, conformer search was performed by DFT calculations at B3LYP/6-31+ G(d) level to elucidate the molecular structure and intermolecular interactions prevailing in the [P-666(14)][Cl]. Vibrational and 1HNMR spectra computed on the most stable conformer geometry were used to identify the features in the experimental spectroscopic data. Results revealed that experimental IR and NMR spectra correlated very well with the corresponding computational spectra confirming that the DFT-optimized equilibrium geometry of the most-stable conformer represents a probable analogue to the experimental conformation. Consequently, hydrogen bonds between [CI](-) and three alpha-hydrogens of [P-666(14)]+ closest to the anion were identified by Natural Bond Orbital (NBO) analysis confirmed by the shifts in the corresponding IR bands.