Please use this identifier to cite or link to this item:
Scopus Web of Science® Altmetric
Type: Journal article
Title: Solution and solid state structures of binuclear zinc(II) complexes of bis(pentadentate)ligands derived from bis(1,4,7-triazacyclononane) macrocycles
Author: Brudenell, Suzanne J.
Spiccia, Leone
Hockless, David C. R.
Tiekink, Edward Richard Tom
Citation: Journal of the Chemical Society. Dalton Transactions. None:1475-1481
Issue Date: 1999
ISSN: 0300-9246
School/Discipline: School of Chemistry and Physics
Statement of
Suzanne J. Brudenell, Leone Spiccia, David C. R. Hockless and Edward R. T. Tiekink
Abstract: Binuclear zinc(II) complexes have been prepared for bis(pentadentate) ligands, generated by addition of 2-pyridylmethyl arms to the secondary nitrogens in bis(1,4,7-triazacyclononane) macrocycles, and supported by CH2CH2 {tmpdtne, [Zn2(tmpdtne)Br2][ClO4]2?H2O 1], CH2CH2CH2 {tmpdtnp, [Zn2(tmpdtnp)Br2][ClO4]2?3H2O 2}, CH2CH2CH2CH2 {tmpdtnb, [Zn2(tmpdtnb)][ClO4]4?3DMSO 3}, m-CH2C6H4CH2 {tmpdtnm-X, [Zn2(tmpdtnm-X)]- [ClO4]4 4} and CH2CH(OH)CH2 {tmpdtnp-OH, [Zn2(tmpdtnp-O)][ClO4]3 5} backbones. The crystal structure of 5 confirmed that the two zinc(II) centres are linked by an endogenous alkoxo bridge generated by deprotonation of the CH2CH(OH)CH2 backbone. A short intramolecular Zn · · · Zn separation of 3.904(2) Å is observed, which matches that found at the active site of alkaline phosphatase. For 1 a binuclear complex with Zn · · · Zn separation of 6.545(9) Å is formed. The distorted octahedral geometry about each zinc(II) centre is defined by five N-donors from the ligand and a bromide in the sixth position. The transoid angles involving one of the tacn nitrogens and either the bromide or a pyridyl nitrogen (148–1698) highlight the degree of distortion. The arrangement of donor atoms within the distorted octahedral co-ordination sphere of ZnII is asymmetric with the bromide ligand cis to the bridgehead nitrogen. The series of zinc complexes display interesting variations in their solid state and solution stereochemistries. The 1H NMR spectrum recorded at 300 K is broad indicating rearrangement between different structures on the NMR timescale. The signals become sharper at higher temperatures but only half the number expected from the solid state structure are observed. A rearrangement to a geometry (square pyramidal through loss of the halide ligand) that preserves the symmetry of the ligand occurs at higher temperatures. Compound 2 exhibits similar solution behaviour while for 3 and 4 the 1H NMR spectra indicate that the symmetric disposition of the ligand is adopted even at room temperature. A correlation exists between the type of bridge linking the pentadentate compartments of the ligands and the preferred solution structure.
DOI: 10.1039/A809946D
Appears in Collections:Chemistry publications

Files in This Item:
There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.