Supramolecular conformational effects in the electrocatalytic properties of electrostatic assembled films of meso(3- and 4-pyridyl) isomers of tetraruthenated porphyrins

Abstract

Meso (3-e 4-piridil)porfirinas coordenadas a quatro complexos [Ru(bipy) 2 Cl] + , M(3-TRPyP) e M(4-TRPyP), onde M = 2H + e Zn 2+ , foram obtidas e caracterizadas por métodos eletroquímicos, espectroscopia e espectrometria de massas. Os filmes eletrostaticamente montados camada por camada com ftalocianina de cobre tetrassulfonada, CuTSPc, apresentaram atividade eletrocatalítica diferenciada para a oxidação de sulfito e nitrito. Em geral, os filmes derivados dos isômeros M(4-TRPyP) são mais ativos para a oxidação de nitrito, enquanto aqueles contendo os isômeros M(3-TRPyP) são mais eficientes para a oxidação de sulfito. Os resultados revelaram uma influência significativa da geometria molecular no sítio ativo dos nanomateriais porfirínicos, que favorece os processos de transferência eletrônica nos derivados de M(3-TRPyP), através de mudanças no empacotamento molecular com a CuTSPc.Meso (3-and 4-pyridyl)porphyrins coordinated to four [Ru(bipy) 2 Cl] + complexes, M(3-TRPyP) or M(4-TRPyP), where M=2H + and Zn 2+ , have been obtained and characterized by electrochemistry, spectroscopy and mass spectrometry. Layer-by-layer electrostatic assembled films with tetrasulfonated phthalocyaninatecuprate(II) anion, CuTSPc, displayed distinct electrocatalytic activity towards sulfite and nitrite oxidation. In general, the films derived from the M(4-TRPyP) isomers are more effective for the oxidation of nitrite, whereas those containing the M(3-TRPyP) isomers are more efficient for the oxidation of sulfite. The results demonstrated the influence of molecular geometry on the active sites of porphyrinic nanomaterials, enhancing the electron-transfer process in the M(3-TRPyP) derivative. This effect results from changes in the chemical environment around the active sites, induced by the contrasting molecular packing interactions with CuTSPc.Keywords: supramolecular chemistry, metalloporphyrins, electrostatic assembled films, electrocatalysis, electrochemistry, mass spectrometry IntroductionMetalloporphyrins have been of great interest in the design of supramolecular systems because their electrochemical, photochemical and catalytic properties can be modulated by employing suitable ancillary bridging transition-metal complexes. [1][2][3][4][5][6][7] In such systems, the ancillary complexes can either modify the local environment around the porphyrin ring, improving the solvation and solubility properties, or act as cofactors in redox processes providing electron acceptor-donor sites and relays. They can also modify the intrinsic activity of the metalloporphyrin center by means of electronic interactions, and contribute with additional sites for intraand intermolecular interactions, allowing the assembly of higher order supramolecular structures and materials.The electrocatalytic properties of porphyrins in homogeneous and heterogeneous systems 7-20 have attracted considerable attention, particularly for multielectronic processes such as the 4-electron reduction of dioxygen to water; 21,22 and the reduction of dinitrogen 11,16,23 and...

Steric and Catalytic Effects in Tetraruthenated Manganese Porphyrins

“…The fragmentation profiles of the polymetalated pyridylporphyrins were found to be analogous to those previously found for the derivatives H 2 (3-TRPyP) and Zn(3-TRPyP). [26,27,30,31] The peak for the [Mn suggesting the occurrence of a Mn III/II redox process in the spray.…”

“…The anodic and cathodic peak current intensities increase linearly as a function of the scan rate, as expected for redox species immobilized on the surface. [9,27,40] As aliquots of a stock solution of nitrite and sulfite were added to the electrolyte solution ( Figure 4) the anodic wave at 1 V intensified linearly as a function of the concentration of those species. This indicates a relatively fast heterogeneous charge-transfer process mediated by the supramolecular films, in contrast with the bare electrodes, which exhibit broad, irreproducible responses.…”

Electronic conduction and electrocatalysis by supramolecular tetraruthenated copper porphyrazine films

“…[20][21][22][23][24][25][26] In particular, the coordination of ruthenium complexes to meso-pyridylporphyrins has provided rather versatile systems, in which the chemical and photochemical reactivity can be modulated by the electronic, structural and steric effects induced by the peripheral complexes. [27][28][29][30][31][32] However, it should be noticed that in the case of tetrapyridyl porphyrins, the electronic coupling between the porphyrin center and the ruthenium complexes is mediated by a Vol. 20, No.…”

Application of the Double Pulse Potential Chronoamperometry Technique to Modify the ITO Electrode Surface

“…The catalyst immobilized on the electrode surface produces a Chemically Modified Electrode (CME). Some CMEs have been reported to be capable of breaking down some compounds; other CMEs are able to detect the presence of an organic pollutant; among the modifying agents applied to these CMEs we can find metallic complexes, such as Ni (salen), Ni (cyclam) [2], Cobalt and Nickel Metalloporphyrins [2], Cobalt phtalocyanines [3], Schiff's bases [3], and Ruthenium Porphyrins, which have been used in the oxidation of sulfite and nitrate [4] and 2,3-dimetil-N,N'-bis(salicildene)butane-2,3-diaminatenickel(II) [5]. Present day methods available to modify electrodes are [6]: a) Direct Absorption, b) Covalent Immobilization, c) Electrode Matrix Modification, and d) Polymer Immobilization.…”