## Revista CON-CIENCIA

*versión impresa* ISSN 2310-0265

#### Resumen

CHOQUE ASPIAZU, Rigoberto; NOGALES, Jorge y APAZA TORREZ, Nataly. **Study of the molecular and reactive properties of the antibiotic Ciprofloxacin at the level **** of Functional Density Theory DFT B3LYP / 6-31G ***.

*Rev.Cs.Farm. y Bioq*[online]. 2020, vol.8, n.2, pp.37-62. ISSN 2310-0265.

**Abstract** **Introduction:** A theoretical computational study of ciprofloxacin was performed, calculating in detail the molecular properties of it. This antibiotic was characterized, presenting values of link lengths and angles as well as chemical properties of interest in QSAR, energy and reactivity studies, obtained by quantum mechanic methods using the Functional Density Theory DFT B3LYP / 6-31G *. **Objective: **To determine the molecular, QSAR and reactivity properties of Ciprofloxacin using the theoretical calculation method called: Density Functional Theory (DFT) **Method: **The structure of ciprofloxacin was mapped using the SPARTAN interface; This was initially subjected to calculations of geometric optimization of Molecular Mechanics to obtain the most stable structure, later all the structures were analyzed using the Hartree-Fock theory to obtain more reliable values of energy and geometry. Subsequently on these structures the DFT Density Functional Theory is applied using the 6-31G * base. With this structure, energy calculations were performed in conjunction with a natural population analysis (NPA) for the neutral and ionized molecule (positive and negative) to determine the nucleophilic, electrophilic and radical centers, and subsequently obtain the descriptors of the local reactivity and the nucleophilic and electrophilic Fukui functions. **Results: **The experimental values of bond length for the aromatic C = C bonds of the phenyl of 1,400 Å, with respect to link lengths C (10q) -C (5) = 1,401 Å and C (8) -C (9q) = 1,406 Å showed differences of 0.001 and 0.006. The characteristic link with the reported aromatic F-C fluorine of 1,363Å, compared to that calculated in this study of 1,353Å shows a difference of 0.01 of the experimental value. The linkage length N1 of the quinoline and the C9 of the cyclopropyl reported with 1,465Å and the calculated 1,450Å shows a difference of 0.015. The experimental aromatic C = O link length of 1,230Å with respect to the found O (3) -C (4) of 1,227Å, shows a difference of 0.003. Finally, in the piperazine ring, the reported CN experimental length of 1,465 Å, the calculated 1,463 Å difference of 0.002 According to the data calculated and reported experimentally, it can be concluded that there is a good correlation in the values of the link lengths at the DFT level B3LYP / 6-31G *. The angles between carbon atoms of the aromatic system found in ciprofloxacin range from 120.02 ° to 122.27 °, in relation to the theoretical value of this type of carbon atoms with sp2 hybridization have an angle of 120 °. Regarding chemical reactivity, the indexes describing global and local chemical reactivity [2], the HOMO orbital is the donor and the LUMO orbital is the acceptor. A band-gap of 4.65 ev clearly indicates that the molecule is very stable. The chemical potential obtained for the neutral ciprofloxacin of (-3,715ev) indicates that the electronic density of the system can vary spontaneously, since it has a negative value. The hardness gave the value of 2,325ev, indicates that ciprofloxacin will have little tendency to give or receive electrons, that is, the hardness has been associated with the stability of the chemical system. **Conclusion: **Molecular and chemical properties values of interest were established in QSAR activity structure studies, energies and reactivity of the antibiotic ciprofloxacin.

**Palabras clave
:
****Ciprofloxacin**; **DFT**; **reactivity descriptors**; **Fukui function**.