Exploiting Excited-State Molecules

Youngmin You
Ewha Womans University
Dec. 1 10:15~10:40


An excited state refers to the transient state that conveys energies greater than that of a state in equilibrium with surrounding media. Among various forms of excited states, electronically excited states are of significant importance because they are intimately associated with a diverse processes in chemistry, optics, and electronics. For instance, devices that convert photon into electron, or vice versa, rely on the identity and lifetime of electronic excited state of component materials. A promising, yet underdeveloped, approach to control processes involving excited states is to employ molecules. Quantum chemical tools, such as those based on density functional theory, enables prediction of electronic structures of any molecules with very high precision. Accumulated knowledge of synthetic chemistries permits design and preparation of molecules exhibiting aimed properties. A variety of physical/chemical methods allow us to directly monitor and to quantify ultrafast processes of molecules that interact with photon or electron. Most of all, versatility in molecular structures provides tremendous opportunities to create and improve function. Therefore, challenges in excited-state molecules are enormous.

My group initiated research to address the challenges in exploiting excited-state molecules. Prime interest is to control and utilize processes involving spin flip during electronic transition (e.g., phosphorescence) or in the excited state (e.g., intersystem crossing). We employ chemistries to approach the challenges. Specifically, we have developed novel classes of molecular emitters, triplet sensitizers, photoredox catalysts, and bioprobes, with combined use of quantum chemistry, organic/organometallic/polymer synthesis techniques, and photophysical and electrochemical methods. Such integrated research has been fruitful. A novel molecular mechanism was devised, which enabled very high quantum yields for photoelectrochemical functionalization of drugs through cycling of both photon and electron. As another example, we established n-p* fluorophore molecules that are capable of harnessing triplet exciton into singlet manifolds for high efficiency fluorescence emission. We also investigated molecular origin for short operation time of blue-phosphorescent organic light-emitting devices. Our mechanistic study revealed that reactive radical ion species could be generated even under balanced carrier injection, and that exciton-mediated intermolecular electron transfer between a host and a dopant was responsible for the generation of such species. Finally, we continue to extend our understanding to application into biological systems. Probes for use in metalloneurochemistry have been developed. In addition, biological utility of photosensitizers that generate singlet oxygen (1O2) has been successfully demonstrated.



  • 2007, Ph.D, DMSE, Seoul National University
  • 2003, MS, Chem. Eng., Seoul National University
  • 2001, BS, Chem. Eng., Seoul National University, cum laude


Professional Career

  • 2017-Present, Associate Professor, Ewha Womans University
  • 2015-2017, Assistant Professor, Ewha Womans University
  • 2013-2015, Assistant Professor, Kyung Hee University
  • 2012-2013, Senior Researcher, Korea Institute of Science and Technology
  • 2011-2012, Research Professor, Ewha Womans University
  • 2009-2010, Postdoctoral Fellow, Massachusetts Institute of Technology
  • 2007-2008, Postdoctoral Associate, Seoul National University


Awards and Honors

  • 2018, CSJ Lectureship Award (The Chemical Society of Japan)
  • 2017, Excellent Lecturer Award (Ewha Womans University)
  • 2008, Best Thesis Award (The Polymer Society of Korea)
  • 2006, Best Poster Award (IUPAC Macro2006)
  • 2004, Best Poster Award (Korea-Japan Joint Forum)
  • 2001, Honor Graduate (Seoul National University)