National Repository of Grey Literature 5 records found  Search took 0.00 seconds. 
Influence of Adsorption on Electrochemical Reduction of Pyridinium Derivatives
Nováková Lachmanová, Štěpánka ; Dupeyre, G. ; Lainé, P. P. ; Hromadová, Magdaléna
Two expanded pyridinium-based compounds 1 and 2 were studied by cyclic voltammetry in two different environments. The nonaqueous solution suppresses the adsorption of the compounds on the electrode surface. Adsorption process in aqueous environment was confirmed by typical shape of the curve as well as by the linear dependence of peak current on the scan rate. The shift of standard redox potential in aqueous solution compared to nonaqueous environment toward more negative potential indicates the adsorption of reactant on the electrode surface. Larger shift observed for flat conjugated molecule 1 confirms its stronger adsorption than for the second molecule.
Single Molecule Conductance and Junction Formation in Solution. Solvent Effect
Lachmanová, Štěpánka ; Šebera, Jakub ; Gasior, Jindřich ; Dupeyre, G. ; Lainé, P. P. ; Mészáros, G. ; Hromadová, Magdaléna
The single molecule conductance of expanded pyridinium derivative terminated by pyridyl\nnitrogen as an anchoring group at both ends of the molecule in two different environments\nwas measured by scanning tunneling microscopy break junction technique (STM-BJ). The\nvalues obtained in commonly used 1,3,5-trimethylbenzene (TMB) significantly differ from\nthe values acquired in a mixture of TMB and ethanol. Markedly lower junction length and\nhigher conductance indicate strong influence of adsorption of the molecule to the substrate\nsurface in pure TMB compared to the TMB and ethanol mixture.
Dependence of Single-Molecule Conductance of Pyridinium Derivatives on Their Structure
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Kolivoška, Viliam ; Pospíšil, Lubomír ; Gasior, Jindřich ; Mészáros, G. ; Lainé, P. P.
The derivates of pyridinium belong to promising group of molecules applicable in molecular electronics. For this purpose, four expanded branched pyridinium compounds were synthetized and the influence of the molecular structure on their electrochemical properties and single-molecule conductances has been studied. The highest values of conductance provided compounds 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium tetrafluoroborate and 3,5-dimethyl-2´,6´-diphenyl-[4,1´:4´,4´´-terpyridin]-1´-ium tetrafluoroborate. By the electrochemical reduction both of these compounds received two electrons in two separated one-electron steps. On the other hand, the compounds 2´,6´-diphenyl-[4,1´:4´,4´´-terpyridin]-1´-ium tetrafluoroborate and 2,6-diphenyl-4-(4-(pyridin-4-yl)phenyl)-[1,4´-bipyridin]-1-ium tetrafluoroborate are reduced by different mechanism and their conductance was lower.
Comparison of Techniques for Single-Molecule Conductance Measurements of Expanded Pyridinium Molecules
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Sokolová, Romana ; Kocábová, Jana ; Gasior, Jindřich ; Mészáros, G. ; Lainé, P. P.
This work is focused on the comparison of two techniques of single-molecule conductance measurements: Scanning Tunneling Microscopy Break Junction technique and Mechanically Controlled Break Junction technique. The structure of studied compound 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium allows the formation of the molecular bridge between two gold electrodes, which are connected to a source of the constant voltage in both of the used methods. The differences, advantages and disadvantages of both of the techniques will be discussed. Both techniques provided two values of conductance of studied compound depending on the experimantal conditions.
Electrochemical Properties of Branched Pyridinium Cations
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Pospíšil, Lubomír ; Lainé, P. P.
The electrochemical properties of branched extended pyridinium cations depend strongly on the structure of the molecule. This work is focused on the redox processes of the electron transfer of four derivatives of pyridinium. The electron transfer mechanism was studied by various electrochemical methods. Although the structures of the studied molecules seem to be quite similar, 1-N-methyl-2,4,6-triphenylpyridinium and 1',3',5'-trimethyl-2,4,6-triphenyl-1,4'-bipyridine-1,1'-diium are reduced in two separate one-electron transfer steps. On the other hand, 1'-methyl-2,4,6-triphenyl-1,4'-bipyridine-1,1'-diium and 1',3,5-trimethyl-2,4,6-triphenyl-1,4'-bipyridine-1,1'-diium accept two electrons, but in a single two-electron transfer. The heterogeneous rate constants of the electron-transfer processes were determined.

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