Electronic conduction and electrocatalysis by supramolecular tetraruthenated copper porphyrazine films

Abstract

Uma nova espécie cobre(II)-tetra(3,4-piridil)porfirazina tetrarrutenada, [CuTRPyPz] 4+ foi sintetizada e sua caracterização conduzida por meio de métodos analíticos, espectroscópicos e eletroquímicos. Sua extensa conjugação-π a distingue dos derivados análogos da mesotetrapiridilporfirina, levando à ocorrência de interações eletrônicas mais fortes entre os complexos periféricos e o anel porfirazínico central. Com base nas interações eletrostáticas e de empilhamento-π, foram realizadas montagens, camada-por-camada, de filmes funcionais, combinando-se a [CuTRPyPz] 4+ com a ftalocianina de cobre(II) tetrassulfonada, [CuTSPc] 4−. As propriedades condutoras e eletrocatalíticas desses filmes foram investigadas através de técnicas de impedância e de voltametria de disco rotatório, observando-se um comportamento metálico nas proximidades do potencial do par redox Ru(III)/(II), bem como uma pronunciada atividade catalítica na oxidação de íons nitrito e sulfito, em meio aquoso.A new tetraruthenated copper(II)-tetra(3,4-pyridyl)porphyrazine species, [CuTRPyPz] 4+ , has been synthesized and fully characterized by means of analytical, spectroscopic and electrochemical techniques. This π-conjugated system contrasts with the related meso-tetrapyridylporphyrins by exhibiting strong electronic interaction between the coordinated peripheral complexes and the central ring. Based on favorable π-stacking and electrostatic interactions, layer-by-layer assembled films were successfully generated from the appropriate combination of [CuTRPyPz] 4+ with copper(II)-tetrasulfonated phtalocyanine, [CuTSPc] 4− . Their conducting and electrocatalytic properties were investigated by means of impedance spectroscopy and rotating disc voltammetry, exhibiting metallic behavior near the Ru(III/II) redox potential, as well as enhanced catalytic activity for the oxidation of nitrite and sulphite ions.Keywords: molecular conductors, porphyrazines, ruthenium polypyridines, thin films, electrocatalysis IntroductionPhthalocyanines and porphyrins are important macrocyclic compounds exhibiting a wide variety of applications in science and technology. [1][2][3][4][5][6][7][8][9][10][11][12][13] Their main characteristics are associated with the π-conjugated ring which imparts interesting physical and chemical properties, including the facility of stacking and yielding molecular films. The possibility of rationally manipulating their properties at the nanoscale is a relevant issue to be pursued, aiming the generation of functional molecular materials for nanotechnology devices. [14][15][16][17] As a matter of fact, tetrapyridyl porphyrins have already been modified with transition metal complexes in order to generate convenient building-blocks and connectors for assembling supramolecular systems and nanostructured materials. 18,19 In such systems, the transition metal complexes can play many roles, because of their wide variety of structural, electronic, redox and catalytic properties. [20][21][22][23][24][25][26] In particular, the coordinati...

Synthesis, Structure, and Electronic Properties of RuN6 Dinuclear Ru-Hbpp Complexes

“…Consequently, for a particular transition metal, a vast array of complexes can be envisaged for which electronic properties can be fine-tuned via the bridging ligand, the auxiliary ligands, or both. This fine-tuning of the electronic interaction is of paramount importance to control magnetic effects and to tune electronic state energies in systems whose reactivities are initiated by means of photochemical and/or redox reactions, including charge separation devices for photochemical solar energy conversion, − information storage devices, − and redox catalysis. − …”