Experimental isolation and spectroscopic characterization of squamocin acetogenin combining FT-IR, FT-Raman and UV–Vis spectra with DFT calculations

HIDALGO, JOSÉ RUIZ; NESKE, ADRIANA; IRAMAIN, MAXIMILIANO A.; ALVAREZ, PATRICIA E.; BONGIORNO, PATRICIO LEYTON; BRANDÁN, SILVIA ANTONIA

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Año: 2020 vol. 1219

0022-2860

Squamocin, an annonaceous acetogenin has been experimentally isolated and characterized in the solidstate using the FT-IR and FT-Raman spectra and in methanol solution by UVevisible spectrum. The mainbands observed were assigned combining the IR and Raman spectra with hybrid functional B3LYP/6-31G* calculations. Structural, electronic and topological properties were predicted at the same level oftheory for the most stable conformer of squamocin in gas phase and methanol solution. A correctedsolvation energy value of 147.54 kJ/mol was predicted for squamocin in methanol while the atomicpopulation natural (NPA) charges evidence higher values on O atoms of R2 and R3 rings, as comparedwith the corresponding to lactone ring. Mapped MEP surfaces suggest that nucleophilic regions arelocated on the O atoms of three rings and of OH bonds belonging to side chain, in agreement with thehigher charges values evidenced on these O atoms while electrophilic regions are predicted on the Hatoms of OH groups. High stabilities of squamocin in both media was revealed by AIM studies while onlyin methanol solution by NBO calculations. The expansion of volume and the higher dipole moment inmethanol suggest a clear solvation of squamocin by solvent molecules. Gap values have evidenced thatsquamocin is most reactive in methanol while that its large aliphatic chain produces an increases thereactivity of this g-lactone, as compared with ascorbic acid lactone. Reasonable concordances among thepredicted UVevisible and IR, Raman spectra with the corresponding experimental ones were found.