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Associate Professor, Physical Chemistry
B.S. 1991, Universidad del Valle, Colombia
Ph.D. 1999, Baylor University
Postdoctoral: 1999-2001, Northwestern University
Email: dcedeno@ilstu.edu
Phone: (309)438-5595
Office: 211 Science Laboratory Building
The main objective of
our research is to use laser calorimetric and spectroscopic
techniques to study the photophysics, photochemistry and
energetics occurring in two different areas:
1. Rational design of photodynamic therapy (PDT) photosensitizers
One area of interest deals with the understanding of how the
molecular structure and electronic environment of a
photosensitizer molecule affects its photophysics. The research
is aimed to increase the photoactivity of photosensitizer drugs
used in the PDT of cancer by increasing the singlet-triplet
intersystem crossing (ISC) yield. As shown in the scheme below,
in terms of the conventional mechanism for photodynamic therapy,
the activity of the drug is largely dependent on the yield of
photosensitizer molecules in the triplet state that could
eventually activate ground state oxygen to its very reactive
singlet state. Our research will mainly focus in investigating
how the molecular structure (aromaticity, conjugation,
planarity, etc), and substitution of the photosensitizer affects
its ISC and fluorescence rates. We are specially interested, but
not limited, to study porphyrin-type molecules. Our goal is to
be able to correlate the activity of the drug (measured as
quantum yield) vs. the drug structure and to understand the
physical aspects involved in the optimization of the ISC process
using our experimental results and computational chemistry.
2. Bonding in organometallic complexes
In another area of research we will study the energetics and
kinetics of metal-ligand interactions in organometallic
complexes in solution. We want to understand how electronic,
steric and reorganizational effects affect metal-ligand bond
energies, and reaction activation energies. This is a field of
interest in chemical and enzymatic catalysis, because the
understanding of the interaction of a given ligand with the
metal and its environment would give important information that
can be used to improve the performance of a catalyst in a given
chemical process. We will use computational chemistry (DFT
level) to interpret and rationalize our experimental results at
their most basic level. Some systems of interest include olefin
complexes of transition metal carbonyls and phosphines which are
involved as intermediates in important industrial processes such
as olefin hydroformilation, isomerization and hydrogenation.
Common Experimental Techniques:
- Organic synthesis: derivatization of photosensitizers
- UV/VIS Absorption: Determine absorption coefficients of molecules
- Fluorescence Spectrophotometry: Determine emission spectra of molecules, and fluorescence yields
- Laser Photoacoustic Calorimetry: Measurement of ISC yields, metal-ligand bond
energies, and addition rates.
- Laser Thermal Lensing: Measurement of absolute fluorescence yields, and singlet oxygen yields
- Near Infrared Laser Spectroscopy: Detection of fluorescence of singlet oxygen
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SELECTED PUBLICATIONS
D. L. Cedeño, R. Sniatynsky, "Metal-Olefin Interactions in M(CO)5(cycloolefin)
(M = Cr, Mo, W; cycloolefin = cyclopropene to cyclooctene): Strain Relief and Metal-Olefin Bond
Strength" Organometallics, 2005, 24, 3882-3890.
D. L. Cedeño, E. Weitz, "Reactions of Fe(CO)4 with C2H5I
in the gas phase: Evidence for the formation of IFe(CO)4(C2H5),
IFe(CO)3(η2-COC2H5), and IFe(CO)4(COC2H5)",
Organometallics, 2005, 24, 1233-1241.
R. Sniatynsky, D. L. Cedeño, "A Density Functional Theory benchmark of
the formation enthalpy and first CO dissociation enthalpy of hexacarbonyl complexes of chromium,
molybdenum, and tungsten", J. Mol. Struct.: THEOCHEM, 2004, 711, 123-131.
D. N. Schlappi, D. L. Cedeño, “Electron-withdrawing effects on metal-olefin
bond strengths in Ni(PH3)2(CO)(C2XnH4-n),
X = F, Cl; n = 0-4: A DFT Study”, J. Phys. Chem. A, 2003, 107, 8763-8773.
D.L. Cedeño and E. Weitz, "Density Functional Theory Study of
Fe(CO)3(h2-C3H6),
HFe(CO)3(h3-C3H5) and the Iron-Allyl Bond
Energy," Organometallics, 22 (2003) 2652-2659.
D.L. Cedeño and E. Weitz, "An Experimental Determination of the Cr-DMB (DMB
= 3,3-dimethyl-1-butene) Bond Energy in Cr(CO)5(DMB): Effects
of alkyl substitution on Chromium-Olefin Bond Energies in Cr(CO)5(olefin)
Complexes," Journal of Physical Chemistry A, 106 (2002)
4651-4660.
D.L. Cedeño and E. Weitz, "Experimental Determination of the Cr-C2Cl4
Bond Dissociation Enthalpy in Cr(CO)5(C2Cl4):
Quantifying Metal-olefin Bonding Interactions," Journal
of the American Chemical Society, 123 (2001) 12857-12865.
D.L. Cedeño, E. Weitz, and A. Bérces, "Bonding Interactions in Olefin (C2X4,
X = H, F, Cl, Br, I, CN) Iron Tetracarbonyl Complexes: Role of the
Deformation Energy in Bonding and Reactivity"
Journal of Physical Chemistry A, 105 (2001) 8077-8085.
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