Propriedades estruturais e vibracionais da acetofenona C11O5H14 e da chalcona C15H13NO por Espectroscopia Raman e infravermelho e cálculos de primeiros princípios

Abstract

In this we presente a sytematic study regarding the strutural and vibrational properties of both acetophenone 2 – hydroxy-3, 4, 6 – Trimethoxyacetophene (C11O5H14) and chalconr (2E) - 1 – (4 - aminophenyl) - 3 – phenyl – prop – 2 em – 1 – one ( C15H13NO) . We have used quantum chemical calculations and Raman and infra red spectroscopy, as well as X - ray diffraction in order to achieve our objetives. Acetophenones are known due their interesting chemical properties and the wide range of possible pharmacological appcations, incleuding antimi-crobial one. Chalcone, on the other hand, conotitutes a class of organic compound derived from natural or sintetic compunds having in its struture two aromatic rings linked byaα, β -unsaturatedketone system. They act in the synthesis of flavonoids, therefore, they have important role in the defense mechanism in plants. Chalconesandderivativespresentmanypharmacologicalproperties such as ant – HIV, antimalarial, anti-leishmanial, ant – fungal, ant – inflammatory, antimicrobial, among others. The acetophenone C11O5H14 was obtained from the stem bark of Croton anisodontus Mull. Arg., and endemic specie found in the caatinga hinterland, Northest Brazil. Chalcone C15H13NO was synthesized by the Claisen – Schmidt condensation reaction using p – aminoacetophenone and benzaldehyde. The molecular strutures of the two compounds were determined through Nuclear Magnetic Resonance (NMR) technique. X - ray diffraction was utilized to determine the crystal structure of the natural substance C11O5H14 in two diferent temperatures, 100 and 298 K. The vibrational spectroscopy study was performed using both Fourier – Transform Raman spectroscopy (FT – Raman) and Fourier Transform infra red spectroscopy (FT – IR). FT – Raman and FT – IR spectra were recorded at room temperature in the spectral ranges 40 – 4000 cm−1 and 400 – 4000 cm−1, respectively. Computitional calculations using the Density functional Theny (DFT) were used in order to obtain informations about the normal modes of the two materials. A complete discussion of the normal modes was achieved through the Potencial Energy Distribuition (PED). Theoretical and experimental absorption spectral from the C11O5H14 were also obtained in order to infer the electronic transitions energies. Additionally,the acetophenone crystal was investigated via Raman spectroscopy as function of tempeture and pressure interval 300 to 8 K, and in the pressure interval 1 atm to 9.7 GPa. However, some changes were observed in certain spectral regions, including the appearance and/or disppeare of bands, change in the intensity and discontinuities in the curve frequencyvs. pressure. These changes were interpreted as small distortion of the acetophenone crytal struture between 300 and 100 K was observed thrugh X – ray diffraction, although the space group P1 from the results from the spectroscopic technique.