Home > Research > Marcetta Y Darensbourg

Marcetta Y Darensbourg
Distinguished Professor of Chemistry
Ph. D., University of Illinois

Contact Information:
Department of Chemistry
Texas A&M University
College Station, TX 77843-3255

Phone: (979) 845-5417
Fax: (979) 845-0158
marcetta@chem.tamu.edu

Related Web Sites

Awards


Current Activities

Figure 1

Figure 2Bio-inspired Catalysts for Hydrogen Production: The ultimate, home-run, goal of our work is to synthesize and develop a robust, highly active hydrogen-producing catalyst comprised of earth-abundant transition metals within a ligand environment that is inspired by the biological Figure 3hydrogenase (H2ase) enzyme active sites. Progress in precise structural modeling of the illusive "rotated" structure displayed in the as-isolated, mixed-valent FeIIFe state in the past decade has permitted in depth analysis of electronic structure by Mö ssbauer, EPR (ENDOR), and computational chemistry. We can conclude why this unique organometallic structure, first spotted in biology (but now achieved by distinct but convergent synthetic strategies in three laboratories) is stable! The square pyramid-inverted square pyramid structures result from sufficient disruption of Fe—Fe bond order in the FeIFeI precursors that permits steric factors to dominate and enforce rotation of one square pyramid relative to the other.
Figure 4

Still, questions remain regarding functional matches: the need for two metals in the [FeFe]- and [NiFe]-H2ase active sites; whether additional collaborative redox activity is required; or whether innocent metallodithiolate ligands control the redox levels of a single metal site. These questions are being addressed by analysis of advanced synthetic analogues that have evolved from 1st and 2nd generation electrocatalysts, and, in collaborations, by comparison to spectroscopic signals from the [FeFe]-H2ase active site.

Figure 5New electrocatalysts for hydrogen production: The connection between the Fe(NO)2 unit and the Fe(CX)3 (X = O or N) unit found in hydrogenase enzyme active sites offers opportunity for design of new catalysts, one of which is shown. In this regard we explore the ability of N2S2 metal complexes to bind as metallodithiolate ligands to various metal acceptors. The properties of such complexes vary The connection of these to light harvesting molecules for dye sensitized, sacrificial electron donor, hydrogen production is also of interest.

When Iron Meets Nitric Oxide: Good Chemistry, Intriguing Biology. The affinity of iron for diatomic molecules, O2, CO, N2, and NO, is central to the most important of life processes, including those of human physiology. Figure 6In this research area we target synthetic chemistry involving dinitrosyl iron complexes (DNICs) that serve as biomimetics of products of FeS cluster degradation by excesses of NO, or as derived from the chelatable iron pool (CIP) in cells. The electronic ambivalence of the DNIC unit is expressed in the ease with which it interconverts between oxidized and reduced forms, {Fe(NO)2}9 and {Fe(NO)2}10, respectively (Enemark/Feltham notation), and serves as impetus to explore analogous reactions known to involve the CuII/CuI redox couple. The accessory ligands which stabilize one redox level over the other, including N-heterocyclic carbenes as histidine mimics, and properties of DNIC derivatives are explored.


Selected Publications

Hsieh, C.-H.; Ding, S.; Erdem, Ö. F.; Crouthers, D. J.; Lubitz, W.; Popescu, C. V.; Reibenspies, J. H.; Hall, M. B.; Darensbourg, M. Y. "Redox active iron nitrosyl units in proton reduction electrocatalysis." Nature Communications, 2014, 5, Article number 3684.

Hsieh, C.-H.; Erdem, Ö. F.; Harman, S. D.; Singleton, M. L.; Reijerse, E.; Lubitz, W.; Popescu, C. V.; Reibenspies, J. H.; Brothers, S. M.; Hall, M. B.; Darensbourg, M. Y. "Structural and Spectroscopic Features of Mixed Valent FeIIFeI Complexes and Factors Related to the Rotated Configuration of Diiron Hydrogenase" J. Am. Chem. Soc. 2012, 134, 13089-13102.

Darensbourg, M. Y.; Lyon, E. J.; Zhao, X.; Georgakaki, I. P. "The Organometallic Active Site of [Fe]Hydrogenase: Models and Entatic States" Proc. Natl. Acad. Sci. 2003, 100, 3683-3688.

Singleton, M. L.; Reibenspies, J. H.; Darensbourg, M. Y. "A Cyclodextrin Host/Guest Approach to a Hydrogenase Active Site Biomimetic Cavity" J. Am. Chem. Soc., 2010, 132, 8870-8871.

Hsieh, C.-H.; Darensbourg, M. Y. "A {Fe(NO)3}10 Trinitrosyliron Complex Stabilized by an N-Heterocyclic Carbene and the Cationic and Neutral {Fe(NO)2}9/10 Products of Its NO Release" J. Am. Chem. Soc., 2010, 132, 14118-14125.

Hess, J. L.; Hsieh, C.-H.; Brothers, S. M.; Hall, M. B.; Darensbourg, M. Y. "Self-Assembly of Dinitrosyl Iron Units into Imidazolate-Edge-Bridged Molecular Squares: Characterization Including Mossbauer Spectroscopy" J. Am. Chem. Soc. 2011, 133, 20426-20434.

Liu, T.; Li, B.; Popescu, C. V.; Bilko, A.; Pérez, L. M.; Hall, M. B.; Darensbourg, M. Y. "Analysis of a Pentacoordinate Iron Dicarbonyl as Synthetic Analogue of the Hmd or Mono-Iron Hydrogenase Active Site" Chem.- A Eur. Journal 2010, 16, 3083-3089.

Hsieh, C.-H.; Chupik, R. B.; Brothers, S. M.; Hall, M. B.; Darensbourg, M. Y. "cis-Dithiolatonickel as Metalloligand to Dinitrosyl Iron Units: the Di-Metallic Structure of Ni(m-SR)[Fe(NO)2] and an Unexpected, Abbreviated Metalloadamantyl Cluster, Ni2(m-SR)4[Fe(NO)2]3" Dalton Trans. 2011, 40, 6047-6053.

Li, B.; Liu, T.; Bilko, A.; Popescu, C. V.; Darensbourg, M. Y. "Synthesis and Mössbauer Characterization of Octahedral Iron(II) Carbonyl Complexes FeI(CO)3L and FeI2(CO)2L2: Developing Models of the [Fe]-H2ase Active Site" Inorganic Chemistry 2009, 48, 11283-11289.

Pulukkody, R.; Kyran, S. J.; Drummond, M. J.; Hsieh, C.-H.; Darensbourg, D. J.; Darensbourg, M. Y. "Hammett correlations as test of mechanism of CO-induced disulfide elimination from dinitrosyl iron complexes.", Chem. Sci. 2014, 3795-3802.

Accessibility | Site Policies | Texas A&M University | Contact Us