Electrochemistry of metal complexes with quinone-functionalized ligands.
    Our group is interested in developing transition metal complexes that can catalyze the multi-electron reduction of small molecules, such as O₂ and CO₂. Much of this work centers around the synthesis of macrocyclic ligands that have quinone groups incorporated into their structures. The quinones function as multi-electron redox centers.¹ The cyclic voltammogram of a Ni(II) complex with a Schiff base ligand that incorporates two naphthoquinone groups is shown below.² The reversible wave at -1.30 V represents the two-electron reduction of the two quinones to semiquinone radical anions. Analysis of the wave shape indicates that the two Eos differ by 35 mV (i.e. E₂^o - E₁^o = -35 mV), a value characteristic of two independent redox centers.³

Subphthalocyanines and subtriazaporphyrins.
    The subphthalocyanine (SubPc) macrocycles have recently received a great deal of attention because of their interesting optical properties and their utility in the synthesis of unsymmetrical phthalocyanines.⁴  We are interested in the synthesis of new forms of the subphthalocyanines and the related subtriazaporphyrins.
 We recently synthesized mixed SubPc/subnaphthalocyanine (SubNc) complexes by cyclizing mixtures of two different ortho-dinitriles.⁵ The x-ray crstal structure of one these complexes, derived from tetrafluorophthalonitrile and 2,3-naphthalenedicarbonitrile, is shown below.

The x-ray crystal structures of a mixed subPC/subNC

Hemiporphyrazines.
    We are also interested in the materials chemistry of main group and lanthanide complexes of the hemiporphyrazine macrocyclic ligand. The x-ray crystal structure of a tin(IV) hemiporphyrazine that was recently synthesized in our laboratory is shown below.⁶

The thermal ellipsoid plot of trans-dichloro(hemiporphyrazinato)tin(IV).

Tris(salicylaldehyde)tame metal complexes.
    We recently started to re-examine the chemistry of the tris(salicylaldehyde)tame (tame =1,1,1-tris{aminomethyl}ethane) Schiff base ligand.⁷  The x-ray crystal structure of the Co(III) form is shown. The Co(II) complex (not shown) is a metal trimer with the formula Co(II)[Co(II)sal₃tame]₂; two Co ions sit in N₃O₃ coordination sites and one in an O₆ site. The magnetism of the Co(II) form is being studied in collaboration with Professor Gordon T. Yee of the University of Colorado at Boulder.
 
 
 
 
 
 
 

1. Durfee, W. S.; Pierpont, C. G. Inorg. Chem.1993, 32, 493.
2. Trimm, J. M.; Alkaire, N. L.; Durfee, W. S. in preparation.
3. Flanagan, J. B.; Margel. S.; Bard, A. J.; Anson, F. C. J. Am. Chem. Soc. 1978, 100, 4248.
4. Geyer, M.; Plenzig, F.; Rauschnabel, J.; Hanack, M.; del Rey, B.; Sastre, Á.; Torres, T. Synthesis 1996, 1139.
5. Stork, J. R.; Potucek, R. J.; Durfee, W. S.; Noll, B. C. Tetrahedron Lett. 1999, 40, 8055-8058.
6. Farris, P. J.; Jacobs, J. T.; Okonczak, M. P.; Durfee, W. S.; Noll, B. C. Acta Crystallogr., 1998, C54, 32.
7. Fleischer, E. B.; Gebala, A. E.; Tasker, P. A. J. Org. Chem. 1971, 36, 3042.