Synthesis and Characterization of Copper Complexes Containing the Tripodal N7 Ligand Tris{2-[(pyridin-2-ylmethyl)amino]ethyl}amine (=N′-(Pyridin-2-ylmethyl)-N,N-bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine): Equilibrium, Spectroscopic Data, and Crystal Structures of Mono- and Trinuclear Copper(II) Complexes
✍ Scribed by Christian Gérard; Aminou Mohamadou; Jérôme Marrot; Stéphane Brandes; Alain Tabard
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- German
- Weight
- 201 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The stability constants of the Cu^II^ chelates with the tripodal heptadentate ligand tris{2‐[(2‐pyridylmethyl)amino]ethyl}amine (=N′‐(pyridin‐2‐ylmethyl)‐N,N‐bis{2‐[(pyridin‐2‐ylmethyl)amino]ethyl}ethane‐1,2‐diamine; tpaa), determined by potentiometry and UV spectrometry, show the formation of [Cu(tpaaH)]^3+^ and [Cu(tpaa)]^2+^ species. In the solid state, two mononuclear Cu^II^ compounds, Cu(tpaa)~2~ (1) and Cu(tpaaH)~3~⋅H~2~O (2), and one trinuclear Cu~3~(tpaa)~2~(ClO~4~)~2~~4~⋅2 H~2~O (3) complex were isolated and characterized by IR, UV/VIS, and EPR spectroscopy. An X‐ray structure of the mononuclear protonated complex 2 shows that the Cu^2+^ ion has a distorted square‐pyramidal geometry (τ=0.21). and the proton is bound to the secondary‐amine function of one uncoordinated arm of the tripod ligand (Fig. 4). The crystal lattice for 2 is stabilized by the H‐bonds between the N‐atom of the free pyridinyl group with the proton of the free secondary‐amine function of the neighboring molecule. The linear trinuclear complex 3 consists of two entities of the pyramidal mononuclear complex 1 bound to the third central Cu^2+^ ion by the free unprotonated arms of the ligands in equatorial position (Fig. 5). The octahedral geometry of the third Cu^II^ atom is achieved by two perchlorate anions in the axial positions. The redox properties of 1–3 compounds was examined by cyclic voltammetry.