The Life of Pi Star: Exploring the Exciting and Forbidden Worlds of the Benzophenone Photophore

Chem Rev. 2016 Dec 28;116(24):15284-15398. doi: 10.1021/acs.chemrev.6b00342. Epub 2016 Dec 16.


The widespread applications of benzophenone (BP) photochemistry in biological chemistry, bioorganic chemistry, and material science have been prominent in both academic and industrial research. BP photophores have unique photochemical properties: upon n-π* excitation at 365 nm, a biradicaloid triplet state is formed reversibly, which can abstract a hydrogen atom from accessible C-H bonds; the radicals subsequently recombine, creating a stable covalent C-C bond. This light-directed covalent attachment process is exploited in many different ways: (i) binding/contact site mapping of ligand (or protein)-protein interactions; (ii) identification of molecular targets and interactome mapping; (iii) proteome profiling; (iv) bioconjugation and site-directed modification of biopolymers; (v) surface grafting and immobilization. BP photochemistry also has many practical advantages, including low reactivity toward water, stability in ambient light, and the convenient excitation at 365 nm. In addition, several BP-containing building blocks and reagents are commercially available. In this review, we explore the "forbidden" (transitions) and excitation-activated world of photoinduced covalent attachment of BP photophores by touring a colorful palette of recent examples. In this exploration, we will see the pros and cons of using BP photophores, and we hope that both novice and expert photolabelers will enjoy and be inspired by the breadth and depth of possibilities.

Publication types

  • Review

MeSH terms

  • Benzophenones / chemistry*
  • Benzophenones / radiation effects
  • Binding Sites / drug effects
  • Biotinylation
  • Catalytic Domain / drug effects
  • Chemistry Techniques, Synthetic
  • Cross-Linking Reagents / chemistry
  • Cross-Linking Reagents / radiation effects
  • Enzymes / chemistry
  • Fluorescent Dyes / chemistry
  • Fluorescent Dyes / radiation effects
  • Light
  • Photoaffinity Labels / chemistry
  • Photoaffinity Labels / radiation effects
  • Photochemical Processes
  • Proteins / chemistry


  • Benzophenones
  • Cross-Linking Reagents
  • Enzymes
  • Fluorescent Dyes
  • Photoaffinity Labels
  • Proteins
  • benzophenone