Banca de QUALIFICAÇÃO: VERÔNICA DA SILVA OLIVEIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : VERÔNICA DA SILVA OLIVEIRA
DATA : 22/06/2017
HORA: 13:00
LOCAL: Sala 3B5
TÍTULO:

Study of cis-[Fe(cyclam)ox]PF₆ complex: crossover spin, photochemical and antibacterial activity

PALAVRAS-CHAVES:

Iron-cyclam, photochemistry, antibacterial activity

PÁGINAS: 124
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Campos de Coordenação
RESUMO:

The present work aims at the synthesis and characterization of the cis-[Fe(cyclam)ox]PF₆ complex and investigation of its photochemical and antibacterial activity. The characterization was performed using elemental, spectroscopic (IR, Raman, UV-Vis and Mössbauer), electrochemical (CV and DPV) and thermal analysis. Photochemical reactivity was assessed by IR with white light exposure, and the results evidenced the degradation of the coordinated oxalate ligand to the metal. The IR spectrum showed vibrational modes in the range of 3286-2878 cm^-1, referring to the N-H group and C-H stretches of the cyclam macrocyclic, as well as n_as(O-C-O) at 1705 and 1679 cm^-1, and n_s(O-C-O) at 1351 cm^-1 attributed to the bidentate coordinated oxalate. The electronic spectrum of the complex in aqueous medium presented three bands, being the one of greater energy (230 nm), attributed to the intraligant transition of cyclam, and the others, 292 nm and 355 nm, referring to LMCT transitions. Cyclic voltammetry of the complex exhibited a reversible Fe^3+/2+ redox pair, with E_1/2= - 41.9 mV. The mössbauer spectrum in 300K showed a doublet (D1) with d=0.30 mm/s and DE_Q= 0.40 mm/s, typical of Fe³⁺ with high spin configuration. However, with the lowering of the temperature, observed the gradual reduction of the intensity of D1 and the appearance of a second doublet (D2), with d=0.19 mm/s and ΔE_Q=1.73 mm/s at 12 K, typical of Fe³⁺ low spin. Characterizing the existence of a temperature dependent spin state transition process. The photochemical reactivity of the cis-[Fe(cyclam)ox]PF₆ complex was shown to be relevant in the synthesis of new Fe-cyclam complexes and in the antibacterial activation. Through the photochemical reaction of the compound the binuclear [((cyclam)Fe)₂(μ-SO₄)](PF₆)2.H₂O was obtained, whose structure was identified by single crystal X-ray diffraction. The cyclic voltammogram of the binuclear showed two almost reversible redox processes, with E_1/2 equal to 169mV and -10.5mV, with K_c= 1.1x10³. The antibacterial activity of the cis-[Fe(cyclam)ox]PF₆ complex was evaluated against Pseudomonas aeruginosa (ATCC 9027), Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922). The best results were obtained for Pseudomonas, with minimum inhibitory concentration (MIC) of 293.5 μM. However, the exposure of the compound to white or blue light for 90 min, potentiated the inhibitory activity of the complex around 59% against Pseudomonas, reducing MIC values to 118.6 μM (white light) and 119.5 μM (blue light). When submitted to 240 min of exposure, the activity was potentiated in 79.5% (white light) and 77.4% (blue light). Therefore, the photochemical activity of the complex under study represents a promising alternative in bacterial combat.

MEMBROS DA BANCA:
Presidente - 1530500 - ANA CRISTINA FACUNDO DE BRITO PONTES
Interno - 1945343 - FRANCISCO ORDELEI NASCIMENTO DA SILVA
Externo ao Programa - 1715109 - DANIEL DE LIMA PONTES
Externo ao Programa - 2275890 - MARCELO DE SOUSA DA SILVA