Issue 22, 2001

Synthesis and characterisation of zinc(ii) complexes of tripodal N7ligands involving pyridine and amine or amidenitrogen donors. Crystal structure of a zinc(ii) complex

Abstract

Two tripodal heptadentate ligands tris[2-(2-pyridylmethyl)aminoethyl]amine (tpaa), and tris[2-picolinamidoethyl]amine (trenpicam) were synthesized as their hydrochloride salts and their protonation constants determined by potentiometry; variable pH 1H NMR spectroscopy allows the determination of the order of protonation of their different basic nitrogen atoms. The stability constants of the zinc(II) chelates with these ligands, determined by potentiometry and UV spectrometry, show the formation of [Zn(LH2)]4+, [Zn(LH)]3+ and [ZnL]2+ species with tpaa, whereas amide group deprotonation of trenpicam permits the detection of the variable stoichiometry species [ZnL]2+, [ZnL2]2+, [Zn(L2H−1)]+, [Zn(L2H−3)], [Zn2(LH−2)2] and [Zn2(L2H−5)], where LHx is an amide-deprotonated ligand. The zinc(II) complexes [ZnL](ClO4)2 (L = tpaa or trenpicam), and the dinuclear complex [Zn2(LH−2)Cl2] (L = trenpicam) have been prepared and characterized by IR and mass spectroscopy. The crystal structure of the protonated ligand [Htrenpicam](ClO4) and the complex [Zn(tpaa)](ClO4)2 are reported. [Htrenpicam]+ contains one intra-molecular H-bond and in the cation [Zn(tpaa)]2+ the geometry around the Zn2+ ion is distorted octahedral with one pyridyl nitrogen uncoordinated.

Graphical abstract: Synthesis and characterisation of zinc(ii) complexes of tripodal N7 ligands involving pyridine and amine or amide nitrogen donors. Crystal structure of a zinc(ii) complex

Supplementary files

Article information

Article type
Paper
Submitted
31 May 2001
Accepted
11 Sep 2001
First published
17 Oct 2001

J. Chem. Soc., Dalton Trans., 2001, 3320-3328

Synthesis and characterisation of zinc(II) complexes of tripodal N7 ligands involving pyridine and amine or amide nitrogen donors. Crystal structure of a zinc(II) complex

A. Mohamadou and C. Gérard, J. Chem. Soc., Dalton Trans., 2001, 3320 DOI: 10.1039/B104777A

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