5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Abstract

O composto 5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) adsorve espontaneamente sobre ouro formando SAMs ("Self-Assembled Monolayers") que, de acordo com os resultados eletroquímicos e de STM ("Scanning Tunneling Microscopy"), contêm poros através dos quais as moléculas dos complexos [Fe(CN) 6 ] 4-, a dependência da corrente faradáica com o pH da solução eletrolítica permitiu o cálculo do pKa da molécula de Hpyt adsorvida sobre ouro (4,2). Os parâmetros termodinâmicos, H ads and G ads , para o processo de adsorção desta molécula foram estimados em -20,01 e -39,39 kJ mol -1 , respectivamente, utilizando-se o modelo de Langmuir. O processo redox da metaloproteína citocromo c foi estudado utilizando-se a SAM de Hpyt. A constante de velocidade heterogênea de transferência de elétrons foi calculada em 2,29 10 -3 cm s -1 .5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) spontaneously adsorbs on gold forming SAMs (self-assembled monolayers) that, based on STM (Scanning Tunneling Microscopy) and electrochemical data, contain pinholes through which [Fe(CN) 6 ] 4-and [Ru(NH 3 ) 6 ] 3+ probe molecules access the underlying gold electrode. For the former molecule, the dependence of the faradaic current on the electrolyte solution pH value allowed the evaluation of the surface pKa as 4.2. The thermodynamic parameters H ads and G ads for the Hpyt adsorption process could be described by the Langmuir model and were calculated as -20.01 and -39.39 kJ mol -1 , respectively. Electrodic redox reaction of cytochrome c metalloprotein was accessed by using the Hpyt SAM with a heterogeneous electron transfer rate constant of 2.29 10 -3 cm s -1 .

Polycyclic aromatic hydrocarbons from asphalt binder: extraction and characterization

“…This molecule forms a stable layer on the gold with a well-known structure, the √3x√3 R30°. 5 This lattice is also observed for the adsorption of other aromatic and alkyl thiols. 6,7 Thus, a different lattice from the thiol layer would be readily identified in the STM image as due to molecules from the PAH extract.…”

“…The HPYT molecule is a rigid ligand that has been employed as a surface modifier for the electrochemistry of proteins and in coordination chemistry. 5,12 The structure of HPYT on the gold surface has been characterized by STM previously. 5 The molecule forms a slightly distorted √3x√3 R30° lattice and the molecular structure has some defects such as a few clusters and pits on the surface.…”

“…5,12 The structure of HPYT on the gold surface has been characterized by STM previously. 5 The molecule forms a slightly distorted √3x√3 R30° lattice and the molecular structure has some defects such as a few clusters and pits on the surface. 5 Scanning on the modified surface was performed with a moderate gap impedance to minimize the effects of tip sample interaction.…”

“…5 The molecule forms a slightly distorted √3x√3 R30° lattice and the molecular structure has some defects such as a few clusters and pits on the surface. 5 Scanning on the modified surface was performed with a moderate gap impedance to minimize the effects of tip sample interaction. A representative image of the Au-HPYT surface is shown in Figure 1.…”

Electrocatalytic Hydroxylation of Sterols by Steroid C25 Dehydrogenase from Sterolibacterium denitrificans

“…The gold working electrode was first cleaned according to ap ublished protocol [28] then modified with Hpyt as described previously. [29] Experiments were performed on solutions that had been purged with argon gas for 30 min. Cyclic voltammetry was performed at different temperatures over the range of 15 to 40 8Cb yu sing aH uber Ministat recirculating water bath connected to aw ater-jacketed electrochemical cell.…”