B.A., Hamline University, 1984
Ph.D. Louisiana State University, 1992
Postdoctoral Fellow, Office of Naval Research, 1992-1994

Hank Speaks:
propane
lawns
hydrocarbons

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Research Interests:

Synthesis of Novel Molecules and Materials with Extended pi-Backbones

The main focus of my research group's efforts are to synthesize molecules with conjugated extended pi-backbones for use in conducting or semiconducting polymers, nonlinear optics material (NLO), and organic light emitting devices (LED's).  In some of these extended pi-systems, metals will complexed to integrated cyclopentadienyls and aryls to modify the electronic properties of the material.

1.  Conducting Polymers: One focus of our research interest is to synthesize and fully characterize conducting polymers based on an extended pi-system hybrid of polyacetylene or poly(1,4-phenylenevinylene) linking a polymetallocene such as polyferrocene or an aromatic heterocycle such as furan or thiophene. The drawbacks of most existing conducting polymers are air-sensitivity, brittleness, and lack of solubility. The design of a new generation of conducting polymers must overcome these limitations. The proposed conducting polymer hybrids combine the high conductivity associated with an extended planar pi-system of polyacetylene and poly(1,4-phenylenevinylene) with thermodynamic stability of ferrocene.

The proposed route to the proposed conducting polymers is based on  Acyclic Diene Metathesis Polymerization (ADMET) of vinyl substituents of aromatics or Ring Opening Metathesis Polymerization (ROMP) of strained alkenes bridging aromatic rings. One such design involves a modification of the poly(1,4-phenylenevinylene) synthesis developed by Grubbs and co-workers at Cal Tech. The advantage of the proposed polymer synthesis is that high polymer forms before the final step, where the extended planar pi-system is formed.  Polymers with extended planar pi-backbones tend to be insoluble in the reaction mixture, thus limiting the molecular weight of the polymer formed. The ROMP of the monomer results in a soluble polymeric precursor to the conducting polymer, which can be easily processed subsequent to the formation of the insoluble conducting polymer in the last step. To prove the validity of electron transport through the conjugated pi-system, a series of mixed-valence ferrocenes will be prepared and subjected to cyclic voltammetry. If mixed valancy is demonstrated in the model compounds, the monomers will be prepared and polymerized via ROMP.

2.  Organometallic Nonlinear Optics Materials:  The common thread running through our research interests is the creation of an extended conjugated pi-backbone between aromatic components. The organometallic polymers designed using this concept have potential use as a third order nonlinear optical material. The mixed-valence molecular models for the conducting polymers proposed in Section 1 may also be useful as molecules showing second order nonlinear optical properties.

The important component of nonlinear optical material is an easily polarizable molecule. The proposed NLO active molecules here are of the "electron push-pull" category, possessing an electron donor and acceptor at opposite ends of an extended conjugated pi-system. The delocalized pi-backbone is responsible for the NLO activity, and through a wide range of substitutions, aromatic substrates, and complexed transition metals, there will be control of the optical properties and material processability.

Many of the proposed polymetallocenes are expected to show significant second order NLO activity. Included are the molecular models of the ferrocene and chromium(0) arene containing conducting polymers. Other systems can be modified by replacing one of the end ferrocenes with an electron donor and the other with an electron acceptor. An added synthetic goal for the metallocenes is that they be chiral which is essential for the formation of a non-centrosymmetric crystals required for nonlinear optical activity.

3.  Polycyclic Aromatic Compounds:  Which Ring Gets the Huckel (4n+2) pi- Electrons When Complexed to a Transition Metal?   One of the more basic chemical questions we are investigating involves complexing the pi-electrons on one of the aromatic rings in a fused aromatic substrate with a transition metal, leaving the pi-electrons on the other aromatic ring isolated from the metal complexed ring. Attempts to quantify this effect will include x-ray crystal structure analysis to measure the degree of bond lengthening or shortening in the uncomplexed aromatic ring of the transition metal-polycyclic aromatic complex relative to the free ligand and chemical reactivity of the complexed ligand relative to the free ligand. Systems of interest include transition metal complexes of the isoelectronic series of benzo[c]furan, benzo[c]thiophene, indenyls, and cyclopentadienyl[c]thiophenes. Also of interest are transition metal complexes of fused aromatic-antiaromatic compounds where the transition metal is bound to the aromatic ring.

4.  Retinoid Anticancer Drugs:   Our most recent interest focuses on the design and synthesis of reinoids (derivatives of retinoic acid and Vitamin A).   We are modifying the carboxylate end of retinoic acid to study the effect on the retinoid's anticancer activity and toxicity.
 

Recent Publications:

Novel Synthesis of Three C30H12 Bowl-Shaped Polycyclic Aromatic Hydrocarbons.  Hagen, S.; Bratcher, M.S.;
Erickson, M.S; Zimmermann, G.; Scott, L.T. Angewendte Chemie, International Edition, English 1997, 36(4), 406-408.

Synthesis of Benzonaphthochrysene:  A Potential Fullerene Precursor.ä Erickson, M.S. and Milliken, J.  J. Polycyclic Aromatic Compounds 1996, 8, 1-7.

Routes to Conjugated Polymers with Ferrocenes in their Backbones:  Synthesis and Characterization of Poly(ferrocenylene divinylene) and Poly(ferrocenylene butenylene).  Stanton, C.E.; Lee, T.R.; Grubbs, R.H.; Lewis, N.S.; Pudelski, J.K.; Callstrom, M.R.; Erickson, M.S.; McLaughlin, M.L. Macromolecules 1995, 28, 8713-8721.

Refinements of the Crystal Structures of 1,4-diphenylbutadiene and Its Complex with Two Moles of Co2(CO)6.   Fronczek, F.R. and Erickson, M.S.  J. of Chemical Crystallography 1995, 25 , 737-742.

Structure of a Cyclotetradecadiene.   Erickson, M.S.; Schilling, P.J.; Fronczek, F.R.; Watkins, S.F. Acta Cryst. 1993, C49 , 165-167.

Synthesis of 1,4-(1,1'-Ferrocenediyl)-1,3-butadiene:  A Dieno-ferrocenophane.   Erickson, M.S.; Fronczek, F.R.; McLaughlin, M.L., Tetrahedron Lett. 1993, 34, 197-198.

3-Benzoyl-1-Tosylpyrrole.  Erickson, M.S.; Fronczek, F.R.; McLaughlin, M.L.   Acta Cryst. 1992, C48, 202-203.

Syntheses of Dipentafulvenes:  Bichromophoric Effects Correlated with Structure.  Erickson, M.S.; Cronan, J.M., Jr.; Garcia, J.G.; McLaughlin, M.L.  J. Org. Chem. 1992, 57, 2504-2508.

Stereoselectivity in the Synthesis of Tetramethylethano-Bridged 3,3'-Di-tert-butyltitanocene Dichloride.  Erickson, M.S., Fronczek, F.R., McLaughlin, M.L. J. Organomet. Chem.1991, 415, 75-85.

S-Oxo-2-thia-[3]-ferrocenophane.  Erickson, M.S.; Yu, Y.; Fronczek, F.R.; McLaughlin, M.L.  Acta Cryst.  1991, C47 , 2668-2669.

The Syn Tetramethylethano-Bridged 3,3'-[Bis-(1,1-dimethylethyl)]titanocene Dichloride.  Erickson, M.S.; Fronczek, F.R.; McLaughlin, M.L. Acta Crystallogr., Sec. C. 1990, C46, 1802-1804.

Tetramethylethano Bridged Dipentafulvene.  Erickson, M.S.; McLaughlin, M.L.; Fronczek, F.R.  Acta Cryst. 1989, C45, 1260-1261.