Department of Chemistry, Columbia University
3000 Broadway, mail code 3119
New York, NY 10027
work:+1 212-854-2175
fax:+1 212-932-1289
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Research Summary
In my research group we view a photon both as a reagent (photon absorption) for initiating photoreactions and as a product (photon emission) which allows molecules to be imaged in space and time. Photons as reagents possess some outstanding properties, e.g., they may be used to selectively excite specific groups of atoms in a single molecule or a specific molecule in a mixture, because the light absorption depends on definite and unique electron energy gaps. This selectivity of photon absorption may be controlled and varied at will by use of lasers or by a monochrometer. The concentration of photons may be varied at will by controlling the light intensity. Photons can even be made optically active by the use of circularly polarized light. Finally, by use of lasers that can produce short pulses of light, high concentrations of photons can be injected into a system to trigger reactions in times as short as a trillionth of a second (a picosecond).
We study the structure and dynamics of a range of reactive intermediates such as carbenes, singlet oxygen, radicals, radical pairs, and biradicals. These species are produced by photochemical excitation. Their chemistry is investigated directly by a range of time-resolved techniques and then characterized in real time by UV-VIS, IR, ESRor NMR analysis.
Our group is developing a novel field termed "supramolecular photochemistry”, or photochemistry beyond the conventional intellectual and scientific constraints implied by the term "molecular photochemistry." In supramolecular processes, non-covalent bonds between molecules play a role analogous to that of covalent bonds between atoms of a molecule. Many of the supramolecular structures of interest may be considered as "guest@host" complexes, where the @ represents a non-covalent bond between guest and host. Among the host structures investigated are polymers (such as starburst dendrimers), porous solids (such as molecular sieve zeolites), and biological molecules (such as DNA and RNA). Photochemical and photophysical methods are employed to investigate the structure and dynamics of reactive intermediates produced by photolysis of guest@host complexes. Current projects include: the use of photoemission to track mRNA molecules in living cells with “molecules beacons” which are specifically designed to “light up” when they hybridize with their complimentary strand on the mRNA; an investigation of the mechanism of reversible oxidation of carbon nanotubes; the stereoselective addition of singlet oxygen to double bonds; the characterization of the surface of nanocrystals; and the mechanism of paramagnetic interconversion of electron and spin paired systems.
The research of students in my group is strongly interdisciplinary and collaborative. Typically, a student will be working together and actively with other research groups in the Chemistry Department, other departments at Columbia , or even departments in other universities. This approach familiarizes students with the advantages of teamwork in research, and allows students to be exposed to a range of intellectual and scientific methods to solve scientific problems and to be engaged in projects ranging from materials science, to environmental science, to chemical biology.
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Mehmet A. Tasdelen, Volkan Kumbaraci, Steffen Jockusch, Nicholas J. Turro, Naciye Talinli, and Yusuf Yagci, "Photoacid Generation by Stepwise Two-Photon Absorption: Photoinitiated Cationic Polymerization of Cyclohexene Oxide by Using Benzodioxinone in the Presence of Iodonium Salt", Macromolecules, 41, 295-297 (2008)
Aya Wakata, Sean M. Cahill, Michael Blumenstein, Rosalind H. Gunby, Steffen Jockusch, Angel A. Marti, Barbara Cimbro, Carlo Gambacort-Passerini, Arianna Donella-Deana, Lorenzo A. Pinna, Nicholas J. Turro, and David S. Lawrence, "A Mechanistic Design Principle for Protein Tyrosine Kinase Sensors: Application to a Validated Cancer Target", Organic Letters, 10, 301-304 (2008)
Patrick Conlon, Chaoyong J. Yang, Yanrong Wu, Yan Chen, Karen Martinez, Youngmi Kim, Nathan Stevens, Angel A. Marti, Steffen Jockusch, Nicholas J. Turro, and Weihong Tan, "Pyrene Excimer Signaling Molecular Beacons for Probing Nucleic Acids", J. AM. CHEM. SOC., 130, 336-342 (2008)
Guang S. He, Hai-Yan Qin, Qingdong Zheng, Paras N. Prasad, Steffen Jockusch, Nicholas J. Turro, Marlin Halim, Dalibor Sames, Hans Agren, and Sailing He, "Dynamic properties and optical phase conjugation of two-photon pumped ultrashort blue stimulated emission in a chromophore solution", Physical Review A, 77, 013824 (2008)
Steffen Jockusch, Nicholas J. Turro, Elizabeth K. Thompson, Martin Gouterman, James B. Callis, and Gamal Khalil, "Singlet molecular oxygen by direct excitation", Photochem. Photobiol. Sci., 7, 235-239 (2008)
Gregory T. Carroll, Denong Wang, Nicholas J. Turro, Jeffrey T. Koberstein, "Photons to illuminate the universe of sugar diversity through bioarrays", Glycoconj. J., 25, 5-10 (2008)
Minzhong Xu, Francesco Sebastianelli, Zlatko Bacic, Ronald Lawler, and Nicholas J. Turro, "Quantum dynamics of couples translational and rotational motions of H2 inside C60", J. Chem. Phys., 128, 011101 (2008)
Elena Sartori, Marco Ruzzi, Nicholas J. Turro, Koichi Komatsu, Yasujiro Murata, Ronald G. Lawler, and Anatoly L. Buchachenko, "Paramagnetic Enhanced Nuclear Relaxation of H2 in Organic Solvents and in H2@C60", J. AM. CHEM. SOC., 130, 2221-2225 (2008)
J. Sivaguru, Marissa Solomon, Thomas Poon, Steffen Jockusch, Sara G. Bosio, Waldemar Adam, and Nicholas J. Turro, "The Reaction of Singlet Oxygen with Enecarbamates: A Mechanistic Playground for Investigating Chemoselectivity, Stereoselectivity, and Vibratioselectivity of Photooxidants", Acc. Chem. Res., 41, 387-400 (2008)
Marissa Solomon, J. Sivaguru, Steffen Jockusch, Waldemar Adam and Nicholas J. Turro, "Vibrational Deactivation of Singlet Oxygen: Does It Play a Role in Stereoselectivity during Photooxygenation?", Photochem. Photobiol. Sci., 7, 531-533 (2008)
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