Nickel(II) complexes of azacyclams: Oxidation and reduction behavior and catalytic effects in the electroreduction of carbon dioxide

Journal Article · Wed Mar 30 00:00:00 EST 1994 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00085a026· OSTI ID:7027853

Abba, F; De Santis, G; Fabbrizzi, L; Licchelli, M; Pallavicini, P; Poggi, A ^[1]; Manotti Lanfredi, A M; Ugozzoli, F ^[2]

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1. Universita di Pavia (Italy)
2. Universita di Parma (Italy)

A wide range of functionalized azacyclam complexes of Ni[sub II] have been prepared through a template reaction which involves the open-chain tetramine complex [Ni[sup II](2[center dot]3[center dot]2[center dot]tet)][sup 2+], formaldehyde, and a locking fragment which is a primary carboxamide or sulfonamide, either aliphatic or aromatic (RNH[sub 2]). The crystal and molecular structure has been determined for the low-spin [3-(4-tolylsulfonyl)-1,3,5,8,12-pentaazacyclotetradecane]nickel(II) complex. The crystal structure consists of three crystallographically independent cationic complexes. All the investigated azacyclam derivatives display the typical solution behavior of the Ni[sub II] macrocyclic complexes: inertness toward demetalation by strong acids and the blue-to-yellow interconversion in coordinating media. Electrochemical investigations in acetonitrile have shown that E[sub 1/2] values associated with Ni[sup III]/Ni[sup II] and Ni[sup II]/Ni[sup I] couples are influenced by the nature of the substitutent appended to the azacyclam ring: such an effect is interpreted on the basis of a [pi] interaction between the metal center and the fifth nitrogen atom inserted in the azacyclam ring. Water soluble Ni[sub II]-azacyclam complexes catalyze the electroreduction of CO[sub 2], as indicated by cyclic voltammetry investigations and controlled-potential coulometry studies, with an efficiency comparable to that of [Ni[sub III](cyclam)][sup 2+]. Such a high efficiency is strictly related to the structural features of the cyclam and azacyclam framework: a 14-membered cycle forming a 5,6,5,6 sequence of chelate rings. Even small deviations from such a geometrical arrangement cause the electrocatalytic effect to be drastically reduced or completely lost.

• OSTI ID: 7027853
• Journal Information: Inorganic Chemistry; (United States), Vol. 33:7; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE
REDUCTION
NICKEL COMPLEXES
CATALYTIC EFFECTS
CATIONS
ELECTROCATALYSTS
ELECTROCHEMISTRY
VOLTAMETRY
CARBON COMPOUNDS
CARBON OXIDES
CATALYSTS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
IONS
OXIDES
OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPLEXES
400400* - Electrochemistry