The Royal Society of NSW
Dwyer and Lions Revisited: Complexes of Sexadentate Ligands
A/Prof. Tony BakerUniversity of Technology, Sydney
Date: Wednesday, 7 October 1998
Location: University of Technology, Sydney
ABSTRACT
Frank Dwyer and Francis Lions successfully collaborated in the 1950s in the synthesis of metal complexes of sexadentate ligands with a view to producing systems with high molecular rotations. This body of work represents a high-point for the "Sydney School" of coordination chemistry. The chemistry deserves further consideration because of recent research indicating that sexadentate ligands can give rise to metal complexes of unusual topologies.
Two of the sexadentate ligands first reported by Dwyer and Lions have been re-prepared and metal complexes isolated. These complexes have been characterised by a number of techniques including x-ray crystallography and electrospray mass spectrometry.
The presentation will include some biographical detail for both Dwyer and Lions. It is noted that both published extensively in the Journal and Proceedings of the Royal Society of NSW. The current impact of the original work has been determined through the Science Citation Index. The relationship of Dwyer, in particular, to the other members of the "Sydney School" will also be discussed.
Further information: Tony Baker Ph: 9514 1764, email: Tony.Baker@uts.edu.au
Report on the Lecture
by Dr Edmund PotterVice-President
There should be more of it - dissecting the scientific advances of the past to see what today's superior tools and techniques can add to knowledge and understanding.
Associate Professor Tony Baker and several co-workers at the University of of Technology, Sydney, did this recently when they followed up the chemical coordination advances made in the 1950's and 60's by Frank Dwyer (1910-1962) and Francis Lions (1901-1972). The new work was described at the 1077th General Monthly Meeting of the Society on October 7th last at UTS in the presence of a co-worker of lions, Dr Frank Garvan, providing a direct link with 40+ years ago.
Dwyer sought chiral metal complexes with high molecular rotations. In supporting this theme Dwyer and Lions designed sexadentate ligands that were constrained to bind in such a way that only the two enantiomers of metal complexes would arise. The first ligand they prepared (H2L1) comprised two salicylaldehyde residues linked by a methylene chain including N and S donor atoms.
Deprotonated H2L1 (ie, l1) complexes with nickle (II), iron (II) and copper (II). An x-ray structure determination of a copper of a copper (II) complex confirms the sexadentate nature of the ligand. The related ligand (L2) where the salicylaldehyde residues are replaced by 2-pyridyl groups has also been re-prepared. Structures have been determined for [NiL2](ClO4)2 and [FeL2](ClO4)2, confirming that this ligand also functions as a sexadentate.
Dwyer, Lions and Mellor reported an unusual magnetic moment for [FeL1]. In this work [FeL1].2H2O was isolated and a variable temperature magnetic study suggests some tendency to spin pairing at liquid nitrogen temperature. This complex may undergo a spin transition at a temperature lower than 100K. This would be an interesting result as a student of Dwyer and Lions, Dr Harry Goodwin and, through him many "grand students" have studied iron (II) spin-transition compounds extensively.
The speaker included historical sketches of Dwyer and Lions. Both were Australian and "related to" the originators of the "Sydney School" of coordination chemistry. After graduation in chemistry at Sydney, Dwyer held a personal Chair in Biological and Inorganic Chemistry at the Australian National University from 1955 until his early death. He is now credited with 187 papers, some posthumus by as much as 8 years. Lions, after a Ph.D. at Manchester and a post-doc at Oxford with Robert Robinson, spent most of his career at the University of Sydney from 1926 to retirement in 1966. From 1949 to 1959 he added an administrative strand to his work through attachment to the University Senate, and was President of our Society in 1946.