Chemistry of tripodal ligands. Part III. Copper complexes of tris(benzimidazol-2-ylmethyl)amine and of its N-n-propyl derivative

The reactions of copper (I or II) salts with ligands Rntb (tris(N-alkylbenz imidazol-2-ylmethyl)amine) gave complexes [Cu(II)(ntb)Cl]Cl . 3H(2)O (1), [ Cu(I)(ntb)(PPh3)](NO3). 1.5H(2)O (2), [Cu(II)(Pmtb)I]Cl (3) and [Cu(I)(Prnt b)I] (4), depending on the reaction conditions. X-ray single crystal diffra ction analyses showed the copper atom to be tetrahedrally coordinated in 2 and 4, but square pyramidal in 1 and trigonal bipyramidal in 3. Structural characteristics were revealed for the complexes and compared, and complex 3 was shown to be the best model compound among the four for the active cent er of blue copper proteins. CV studies showed the electrochemical behaviors of the complexes: 1 has two redox couples, phosphine ligation stabilizes 2 towards redox reactions, while 3 and 4, with the same cationic formula [Cu (Prntb)I](1+,0) have very similar complicated redox patterns, indicating th e reversibility of the two species. IR and UV-Vis spectroscopic studies wer e also reported. (C) 1999 Elsevier Science Ltd. All rights reserved.