Detailed Research Overview
and Recent Publications

 

Department of Chemistry
Columbia University
3000 Broadway
MC 3119 New York
NY 10027
Tel: (212) 854 2175
email: njt3@columbia.edu

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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, ESR or 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.


Selected Publications (Recently Published)

J. Wu, S. Zhang, Q. Meng, H. Cao, Z. Li, X. Li, S. Shi, D. H. Kim, L. Bi, N.J. Turro, and J. Ju, 𚌖-Modified Nucleotides as Reversible Terminators for Pyrosequencing, Proc. Nat抣. Acad. Soc., 104, 16462-16467 (2007). PDF

B. White, S. Banarjee, S. O払rien, N.J. Turro, and Irving P. Herman, 揨eta-Potential Measurements of Surfactant-Wrapped Individual Single-Walled Carbon Nanotubes, J. Phys. Chem., C, 111, 13684-13690 (2007). PDF

C. Abeywickrama, H. Matsuda, S. Jockusch, J. Zhou, Y. P. Jang, B.-X. Chen, Y. Itagaki, B. F. Erlanger, K. Nakanishi, N. J. Turro and J. R. Sparrow, 揑mmunochemical Recognition of A2E, a Pigment in the Lipofuscin of Retinal Pigment Epithelial Cells. Proc. Nat抣 Acad. Sci., 104, 14610-14675 (2007). PDF

N. Stevens, J. Dyer, A. A. Marti, M. Solomon, and N.J. Turro, 揊RETView: A Computer Program to Simplify the Process of Obtaining Fluorescence Resonance Energy Transfer Parameters, Photochem. Photobiol. Sci., 6, 909-911 (2007). PDF

J. Lopez-Gejo, J. T. Kunjappu, J. Zhou, B. W. Smith, P. Zimmerman, W. Conley, and N.J. Turro, 揚olycycloalkanes as Potential Third-Generation Immersion Fluids for Photolithography at 193 nm, Chem Mater., 19, 3641-3647 (2007). PDF

A. A. Marti, C. A. Puckett, J. Dyer, N. Stevens, S. Jockusch, J. Ju, J. K. Barton, and N.J. Turro, 揑norganic-Organic Hybrid Luminescent Binary Probe for NDA Based on Spin-Forbidden Resonance Energy Transfer, J. Am. Chem. Soc., 129, 8680-8681 (2007). PDF

I. Washington, J. Zhou, S. Jockusch, N.J. Turro, K. Nakanishi, and J. Sparrow, 揅hlorophyll Derivatives as Visual Pigments for Super Vision in the Red, Photochem. Photobiol. Sci., 6, 775-779 (2007). PDF

J. A. Johnson, M. G. Finn, J. T. Koberstein, and N.J. Turro, 揝ynthesis of Photocleavable Linear Macromonomers by ATRP and Star Macromonomers by a Tandem ATRP-Click Reaction: Precursors to Photodegradable Model Network, Macromolecules, 40, 3589-3598 (2007). PDF

Y. Yagci, S. Jockusch, and N.J. Turro, 揗echanism of Photoinduced Step Polymerization of Thiophene by Onium Salts: Reactions of Phenyliodinium and Diphenylsulfinium Radical Cations with Thiophene, Macromolecules, 40, 4481-4485 (2007). PDF

S. Jockusch, Q. Zheng, G. S. He, H. E. Pudavar, D. J. Yee, V. Balsanek, M. Halim, D. Sames, P. N. Prasad, and N.J. Turro, 揟wo-Photon Excitation of Fluorogenic Probes for Redox Metabolism: Dramatic Enhancement of Optical Contrast Ratio by Two-Photon Excitation, J. Phys. Chem. C, 111, 8872-8877 (2007). PDF

M. Halim, M. S. Tremblay, S. Jockusch, N. J. Turro, and D. Sames, 揟ransposing Molecular Fluorescent Switches into the Near-IR: Development of Luminogenic Reporter Substrates for Redox Metabolism, J. Am. Chem. Soc., 129, 7704-7705 (2007). PDF

E. Sartori, I. V. Khudyakov, X. Lei, and N. J. Turro, 揂 Time-Resolved Electron Paramagnetic Resonance Investigation of the Spin Exchange and Chemical Interactions of Reactive Free Radicals with Isotopically Symmetric (14N-X-14N) and Isotopically Asymmetric (14N-X-15N) Nitroxyl Biradicals, J. Am. Chem. Soc., 129, 7785-7792 (2007). PDF

A. A. Marti, S. Jockusch, N. Stevens, J. Ju, and N.J. Turro, 揊luorescent Hybridization Probes for Sensitive and Selective DNA and RNA Detection, Acc. Chem. Res., 40, 402-409 (2007). PDF

D. K. Balta, N. Arsu, Y. Yugci, S. Jockusch, and N.J. Turro, 揟hioxanthone-Anthracene: A New Photoinitiator for Free Radical Polymerization in the Presence of Oxygen, Macromolecules, 40, 4138-4141 (2007). PDF

S. Funk, U. Burghaus, B. White, S. O払rien, and N.J. Turro, 揂dsorption Dynamics of Alkanes on Single-Wall Carbon Nanotubes: A Molecular Beam Scattering Study, J. Phys. Chem. C, 111, 8043-8049 (2007). PDF

A. Natarajan, L. S. Kaanumalle, S. Jockusch, C. L. D. Gibb, B. C. Gibb, N.J. Turro, and V. Ramamurthy, 揅ontrolling Photoreactions with Restricted Spaces and Weak Intermolecular Forces: Exquisite Selectivity during Oxidation of Olefins by Singlet Oxygen, J. Am. Chem. Soc., 129, 4132-4133 (2007). PDF

P. Deo, N. Deo, P. Somasundaran, A. Moscatelli, S. Jockusch, N.J. Turro, K. P. Ananthapadmanabhan, and M. F. Ottaviani, 揑nteractions of a Hydrophobically Modified Polymer with Oppositely Charged Surfactants, Langmuir, 23, 5906-5913 (2007). PDF

A.A. Marti, X. Li, S. Jockusch, N. Stevens, Z. Li, B. Raveendra, S. Kalachikov, I. Morozova, J. J. Russo, D. L. Atkins, J. Ju and N.J. Turro, 揇esign and Characterization of Two-Dye and Three-Dye Binary Fluorescent Probes for mRNA Detection, Tetrahedron, 63, 3591-3600 (2007). PDF

H. Saito, J. Sivaguru, S. Jockusch, J. Dyer, Y. Inoue, W. Adam and N.J. Turro, 揅ontrolled Diastereoselectivity at the Alkene-Geometry through Selective Encapsulation: E-Z Photoisomerization of Oxazolidinone-Functionalized Enecarbamates within Hydrophobic Nano-Cavities, Chem. Comm., 819-821 (2007). PDF

G. E. Khalil, E. K. Thompson, M. Gouterman, J. B. Callis, L. R. Dalton, N. J. Turro, and S. Jockusch, 揘IR Luminescence of Gadolinium Porphyrin Complexes, Chem. Phys. Letts., 435, 45-49 (2007). PDF