David A. Modarelli

Research Interests

Solar Energy Conversion, Organic Photovoltaics, Artificial Photosynthesis, Dendrimer synthesis, Electron-Transfer Reactions, Time-Resolved Laser Spectroscopy, Single Molecule Spectroscopy, Photophysics and Photochemistry.

My group combines synthetic chemistry with ultrafast laser spectroscopy and single molecule spectroscopy to study the electronic properties of molecules, polymers, and materials.  All of our work involves understanding these electronic properties from a physical organic and materials point of view.  The properties of both molecules and supramolecular assemblies (i.e., photovoltaic devices) are directly affected by structure.

Synthesis and Ultrafast Time-Resolved Spectroscopy of Organic Photovoltaics 
Photovoltaic devices (PDs) are designed to convert solar energy into electricity.  Our research on organic PDs is focused on developing new paradigms in PD design by synthesizing self-assembled electron-donor and electron-acceptor arrays.  We use ultrafast laser spectroscopy on the femtosecond and picosecond time scales to study energy and electron transfer in these compounds.  The results from these experiments are translated into preparing new organic PDs.

Monitoring Organic Catalysis: Time-Resolved Fluorescence Anisotropy of Chiral Dendrimers
A second area of research in our group is the study, in real time, of enantioselective reactions catalyzed by chiral dendrimeric catalysts.  We use single molecule fluorescence spectroscopy and  time-resolved fluorescence anisotropy measurements to examine the time dependent changes in dendrimer structure occurring as catalysis takes place.  This research is expected to have far-reaching implications in catalysis as well as biological chemistry.

Electron-Transfer in Photosynthetic Reaction Center Mimics
The photosynthetic reaction center in green plants and purple bacteria utilizes light to initiate a series of electron-transfer steps that transports an electron over extremely long distances. A third area of research in our group involves the synthesis and study of photosynthetic mimics, that is, nanoscale molecules that are designed to replicate the complex and elegant process of electron-transfer in biological systems. The photosynthetic mimics synthesized and studied in our research group are based upon dendrimers that  contain porphyrins or porphyrin analogs at the core of the dendrimer and electron acceptor groups as end-groups.

Photophysical Properties of Unusual Porphyrins and Porphyrinoids 
Within our group we also study the optical properties (steady state and ultrafast time-resolved) of unusual porphyrins and porphyrinoids.  We have recently studied the photophysical properties of N-confused porphyrins, corroles and octaphyrins using these techniques. 

Selected Publications

1. Nguyen, T.; He, D.; Turner, D.; Alemán, E.A.; Wu, Y.; Hadad, C.M.; Parquette, J.R.; Modarelli, D.A. "Energy and Electron-Transfer in Two Novel Types of Diporphyrin Naphthalene Diimide Dendrons" J. Am. Chem. Soc. 2009, submitted.
2. Vyas, S.; Hadad, C.; Modarelli, D.A. "TDDFT Calculations of the Structure and Absorption Spectra of Free-Base N-Confused Porphyrin and N-Confused Tetraphenylporphyrin" J. Phys. Chem. A 2008, 112, 6533-6549.
3. Smith, T.; Modarelli, D.A. "The Efficient Synthesis of Unsymmetrical Oligo(phenylenevinylenes) Tetrahedron Lett. 2008, 49, 526 - 528.
4. Alemán, E.A.; Rajesh, C.S.; Ziegler, C.J.; Modarelli, D.A. "Ultrafast Spectroscopy of Free Base N-Confused Porphyrins" J. Phys. Chem. A 2006, 110, 8605-8612.
5. Shaw, J.L.; Wolff, S.A.; Aleman, E.A.; Ziegler, C.J.; Modarelli, D.A. "Synthesis and Spectroscopy of a Series of Substituted N-Confused Tetraphenylporphyrins" J. Org. Chem. 2004, 69, 7423-7427.
6. Wolff, S.A.; Alemán, E.A.; Banerjee, D.; Rinaldi, P.L.; Modarelli, D.A. "One-Step Synthesis and Characterization of Difunctionalized N-Confused Tetraphenylporphyrins" J. Org. Chem. 2004, 69, 4571-4576.
7. Belair,J.P.; Ziegler, C.J.; Rajesh, C.S.; Modarelli, D.A. "Photophysical Characterization of Free-Base N-Confused Tetraphenylporphyrins" J. Phys. Chem. A 2002, 106, 6445-6451.
8. Rajesh, C.S.; Capitosti, G.J.; Cramer, S.C.; Modarelli, D.A. "Photoinduced Through-Space Electron-Transfer within a Series of Free-Base and Zinc Porphyrin- Containing Poly(Amide) Dendrimers" J. Phys. Chem. B 2001, 105, 10175-10188.
9. "Intramolecular Photoinduced Electron-Transfer Within Porphyrin-Containing Polyamide Dendrimers" Capitosti, G.J.; Cramer, S.J.; Rajesh, C.S.; Modarelli, D.A. Org. Lett. 2001, 3, 1645-1648.