Portal de Periódicos da CAPES

Novel Cu III Bis‐1,2‐dichalcogenene Complexes with Tunable 3D Framework through Alkaline Cation Coordination: A Structural and Theoretical Study

2004; Wiley; Volume: 10; Issue: 7 Linguagem: Inglês

10.1002/chem.200305422

1521-3765

Xavi Ribas, João C. Dias, Jorge Morgado, Klaus Wurst, Elı́es Molins, Eliseo Ruíz, Manuel Almeida, Jaume Veciana, Concepció Rovira,

Polyoxometalates: Synthesis and Applications

Abstract The deprotonated form of the ligands pyrazine‐2,3‐diselenol (pds) and pyrazine‐2,3‐dithiol (pdt) react with Cu(ClO 4 ) 2 ⋅6 H 2 O to form different Cu III complexes Na[Cu III (pds) 2 ]⋅2 H 2 O ( 1 ), Li[Cu III (pds) 2 ]⋅3 H 2 O ( 2 ), and Na[Cu III (pdt) 2 ]⋅2 H 2 O ( 4 ) depending on the countercation compound used as deprotonating agent (NaOH, LiOH). Two other Cu III complexes were obtained by replacement of the alkali metal cations with tetrabutylammonium (TBA + ), namely, TBA[Cu III (pds) 2 ] ( 3 ), and TBA[Cu III (pdt) 2 ] ( 5 ). All complexes were characterized by 1 H and 13 C NMR and IR spectroscopy, electronic absorption, elemental analysis, cyclic voltammetry (CV), and X‐ray crystallography. Electrical conductivity measurements on single crystals show that these salts exhibit insulating behavior. The crystal structure of these species revealed a lateral coordination capability of the N atoms of the pyrazine ring of both pds and pdt ligands towards the alkali metal ions, which leads to the build up of a net of coordinative bonds, hydrogen bonds, and contacts that result in the final 3D structure. Two parameters control the crystal engineering of the final 3D structures: the nature of the alkali metal countercation and the nature of the chalcogen atom (Se/S), which allow fine‐tuning of complex 3D crystal lattice. Density functional calculations were performed on the [Cu(pds) 2 ] and [Cu(pdt) 2 ] systems to investigate the electronic structure of the complexes and understand their electronic and electrochemical behavior by studying the frontier molecular orbitals. This study also reveals whether the redox processes take place on the ligands or on the metal center, a question under continuous discussion in the literature.