Light-emitting molecular machines: pH-induced intramolecular motions in a fluorescent nickel(II) scorpionate complex

Chemistry. 2002 Nov 4;8(21):4965-72. doi: 10.1002/1521-3765(20021104)8:21<4965::AID-CHEM4965>3.0.CO;2-X.

Abstract

A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of trigonal bipyramidal stereochemistry, as shown by X-ray diffraction studies performed on the crystalline complex salt. At pH 7.5, an OH- ion binds the metal and a six-coordinate species forms. The binding-detachment of the pendant arm to/from the NiII center is signaled by changes in the emission properties of the dansyl subunit in the side chain; the fluorescence of this side chain is high when the pendant arm is not coordinated and low when the sulfonamide group is bound to the metal. The system investigated represents the prototype of a light-emitting molecular machine, driven by a pH change.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Fluorescence*
  • Hydrogen-Ion Concentration
  • Light*
  • Molecular Motor Proteins / chemical synthesis*
  • Molecular Motor Proteins / chemistry
  • Molecular Structure
  • Motion
  • Nickel / chemistry
  • Organometallic Compounds / chemistry

Substances

  • Molecular Motor Proteins
  • Organometallic Compounds
  • Nickel