_Applied_  
_sciences_  
_Article_  
**Structural, Vibrational and Electrochemical Analysis**  
**and Antibacterial Potential of Isomeric Chalcones**  
**Derived from Natural Acetophenone**  
**[PERSON] \({}^{1}\)\({}^{\copyright}\), [PERSON] \({}^{1}\), [PERSON], Jr. \({}^{1}\)\({}^{\copyright}\), [PERSON] \({}^{2}\), [PERSON] \({}^{2}\), [PERSON] \({}^{3}\)\({}^{\copyright}\), [PERSON] \({}^{4}\), [PERSON] \({}^{4}\), [PERSON] \({}^{4}\)\({}^{\copyright}\), [PERSON] \({}^{1,5}\), [PERSON] \({}^{1}\), [PERSON] \({}^{1,6}\)\({}^{\copyright}\), [PERSON] \({}^{6}\)\({}^{\copyright}\), [PERSON] \({}^{7,8,*}\)\({}^{\copyright}\), [PERSON] \({}^{1}\)\({}^{\copyright}\) and [PERSON] \({}^{1,2,9,*}\)\({}^{\copyright}\) \begin{tabular}{l l} \({}^{1}\) & Departamento de Quimica Biologica, Universidade Regional do Cariri, Ctrao CE 63.105-000, Brazil; \\ [PERSON]P.T.d.S.); [EMAIL_ADDRESS] (T.S.d.F.); [EMAIL_ADDRESS] (D.M.S.J.); \\ [EMAIL_ADDRESS] (C.E.S.N.); [EMAIL_ADDRESS] (H.D.M.C.); \\ [EMAIL_ADDRESS] (A.L.A.B.L.); [EMAIL_ADDRESS] (A.M.R.T.) \\
2 & Centro de Ciencias Exatas Tecnologia, Curso de Quimica, Universidade Vale do Acarau, \\  & Sobral CE 62.040-370, Brazil; bandeira@uva.netbr (P.N.B.); [EMAIL_ADDRESS] (M.S.d.S.J.) \\
3 & Grupo de Quimica Teorica e eletroquimica, Faculdade de Filosofia Dom Aureliano Matos, FAFIDAM, \\  & Universidade Estadual do Ceara, Limoeiro do Norte CE 62.930-000, Brazil; [EMAIL_ADDRESS] \\
4 & Departamento de Quimica Analitica e Fisico-Quimica, Universidade Federal do Ceara, \\  & Fortaleza CE 60.440-900, Brazil; [PERSON]] (A.A.C.A.); [EMAIL_ADDRESS] (E.M.M.); [EMAIL_ADDRESS] (P.d.L.-N.) \\
5 & Departamento de Fisica, Universidade Regional do Cari, Ctrao CE 63.041-145, Brazil \\
6 & Departamento de Parasitologia e Microbiologia, Universidade Federal do Piaui, Teresa PI 64.049-550, Brazil; [EMAIL_ADDRESS] \\
7 & Faculty of Medicine, University of Porto, Alameda Prof. [PERSON], 4200-319 Porto, Portugal \\
8 & Institute for Research and Innovation in Health (i3S), University of Porto, 4200-135 Porto, Portugal \\
9 & Centro de Ciencias e Tecnologia, Universidade Estadual do Ceara, Fortaleza CE 60.714.903, Brazil \\ \({}^{*}\) & Correspondence: [EMAIL_ADDRESS] (N.M.); [EMAIL_ADDRESS] (H.S.d.S.) \\ \end{tabular}   
Received: 8 June 2020; Accepted: 2 July 2020; Published: 8 July 2020  
**Abstract:**_Background_:_ Chalcones are part of a family of small phenolic compounds that are being extensively studied for presenting a diversity of molecular structures and biological activities. In this paper, two chalcones, (_E_)-1-(2-hydroxy-3,4,6-trimethoxyphenyl)-3-(3-nitrophenyl)prop-2-en-1-one (1), (_E_)-1-(2-hydroxy-3,4,6-trimethoxyphenyl)-3-(4-nitrophenyl)prop-2-en-1-one (2), were synthesized by Claisen-Schmidt condensation. _Methods_: The molecular structures of these chalcones were determined by Nuclear Magnetic Resonance and characterized by infrared, Raman spectroscopy, and electrochemical analysis at room temperature. Vibrational wavenumbers were predicted using Functional Density Theory (DFT) calculations, and their normal modes were analyzed in terms of potential energy distribution (PED). Besides this, DFT calculations were performed to obtain the molecular orbitals and their quantum descriptors. The UV-Vis absorption spectrum of the synthesized chalcones was measured and compared with each other. In addition, analyses of antimicrobial activity and modulation of antibiotic resistance were carried out to assess the antibacterial potential of these chalcones. _Results_: The vibrational spectra of polycrystalline chalcones obtained by ATR-FTIR, FT-Raman and DFT calculations allowed a complete assignment of the vibrational modes, and revealed the quantum chemical parameters. Both chalcones did not show good responses when associated with the antibiotics Ciprofloxacin and Cephalexin against _S. aureus_ 10 and _E. coli_ 06 strains. However, a significant potentiating of the Gentamicin activity against _S. aureus_ 10 and _E. coli_ 06 strains was observed for chalcone 2.