korea inu

Molecular Spectroscopy Lab

 Name   Han-Gook Cho
 Office   Rm. 448, Natural Science Building / TEL : +82-32-835-8236
 Lab   Molecular Spectroscopy Group / Rm. 412, Natural Science Building / TEL : +82-32-835-4561
 E-mail   hgc@incheon.ac.kr

 Research Fields

• main research field
   - Molecular Spectroscopy

• detail research field
   - Vibrational Spectroscopy, Matrix Isolation, Coordination Chemistry


• Ph.D., Physical Chemistry, Michigan State University, USA., 1989
• M.S., Physical Chemistry, Korea Advance Institute of Science, 1981
• B.S., Chemistry, Yonsei University, 1979

 Research Interests

We are primarily interested in preparation and identification of small transition-metal coordinated complexes. While more amenable to high level theoretical computations, these new breed of metal complexes reveal distinct structures and ligand effects that normally the much larger cousins possess. They also often show interesting photochemical reactions including photo-reversibility. Therefore, they are considered as model systems to study the structural and electronic properties of the much larger transition-metal complexes.

Many of the newly introduced small transition-metal complexes are in fact high oxidation-state complexes (carbenes and carbynes), which were first discovered by Schrock and Fischer in early 1970's. They have played an important role in understanding the nature of carbon-metal bonds, and become an essential part of coordination chemistry. Importance of the high oxidation-state complexes can not be overemphasized; they are efficient double-bond addition and C-H bond insertion agents and important catalysts for many methathesis reactions. As a result, numerous high oxidation-state complexes with various conformations have been introduced, thanks to the chemical interests and industrial purposes.

Our transition-metal complexes are provided in gas-phase reactions of laser-ablated transition-metal atoms and small organic compounds and isolated in a noble gas matrix. Photolysis and annealing often create dramatic variations among the product absorptions, providing clues for the photochemistry, reactivity, and relative stability of each complex. Spectral variation by isotopic substitution is crucial information for identification of the generated metal complexes. The observed frequencies and intensities and variation of them by isotopic substitution are interpreted with help of computational results for the plausible reaction products. Therefore, our research is a combination of gas-phase reactions between metals and organic compounds, isotopic bstitutions, spectroscopic observations, and electronic-state calculations, eventually leading to the reaction mechanism.

These results not only expand the horizon for transition-metal coordination chemistry and understanding of the reaction paths but provide valuable information for activation of naturally abundant simple organic species such as small alkanes to convert them to more precious products as well. Studies originally started with methyl halides to discover formation of agostically distorted methylidene complexes and more symmetric methylidyne species and later are extended to reactions with small alkanes, CFC's, ethylene, and acetylene. High oxidation-state complexes of Group 3-10 transition-metals, lanthanides, and actinides have been identified, and therefore, C-H(X) insertion by transition-metal atoms and following rearrangements are now considered as a general phenomenon.

 Selected Publications

1. “Preparation and Characterization of Simple Dihalomethylidene Platinum Dihalide Complexes in Reactions of Laser-
    Ablated Pt Atoms with Tetrahalomethanes,”
    Han-Gook Cho and Lester Andrews, J. Am. Chem. Soc. 2008, 130(47), 15836-15841

2. “Infrared Spectra of HC≡C-MH and M-η2-(C2H2) from Reactions of Laser-Ablated Group-4 Transition-Metal Atoms with
    Han-Gook Cho, Gary P. Kushto, Lester Andrews, and Charles W. Bauschlicher, Jr. J. Phys. Chem. A 2008, 112, 6295-
    6304. [Front Cover Article].

3. “Formation of HC≡ReH3 in Methane Activation by Re Atoms: Observation of the Illusive Methylidyne C-H Stretching
    Han-Gook Cho and Lester Andrews, Organometallics 2007, 26, 4098-4101. [Communication].

4. “Matrix Preparation and Spectroscopic and Theoretical Investigations of Simple Methylidene and Methylidyne
    Complexes of Group 4-6 Transition Metals,”
    Lester Andrews and Han-Gook Cho, Organometallics 2006, 25, 4040-4053. [Front Cover Article, Review].

5. “Infrared Spectra of CH3-MoH, CH2=MoH2, and CH≡MoH3 Formed by Activation of CH4 by Molybdenum Atoms,”
    Han-Gook Cho and Lester Andrews, J. Am. Chem. Soc. 2005, 127, 8226-8231.

6. “The C-H Activation of Methane by Laser-Ablated Zirconium Atoms: CH2=ZrH2, the Simplest Carbene Hydride Complex,
    Agostic Bonding, and (CH3)2ZrH2,”
    Han-Gook Cho, Xuefeng Wang, and Lester Andrews, J. Am. Chem. Soc. 2005, 127, 465-473.

7. “[H2C=ZrH2]: The Simplest Carbene Hydride Complex, Agostic Bonding, and C-H Activation of CH4 to Form
    Lester Andrews, Han-Gook Cho, and Xuefeng Wang, Angew. Chem. Int. Ed. 2005, 44, 113-116. [Communication].

8. “Persistent Photo-Reversible Transition-Metal Methylidene System Generated from Reaction of Methyl Fluoride with
    Laser-Ablated Zirconium Atoms and Isolated in a Solid Argon Matrix,”
    Han-Gook Cho and Lester Andrews, J. Am. Chem. Soc. 2004, 126, 10485-10492.