Selective intercalation of Cs+ in the "V"-shaped cavity of a bichromophoric anion radical: Cs+ assisted pi-s-pi-delocalization of an electron.
EPR studies in tetrahydrofuran, reveal that the one electron reduction of 1-(9-methyl-9H-fluoren-9-yl)-4-methylbenzene via electron transfer from cesium metal produces an anion radical that has a large affinity for the cesium cation. The affinity of this anion radical for Cs+ is so great that it will actually "suck" the Cs+ (but not Na+ or K+) right out of the grasp of 18-crown-6, leading to a cation-assisted pi-stacked complex, where the s-orbital of the metal cation is simultaneously overlapped with the pi-clouds of the phenyl and fluorenyl moieties. At ambient temperature, proton- and cesium-electron coupling constants are rapidly (on the EPR time scale) modulated as a result of the simultaneous existence of two interconverting conformers having an averaged cesium splitting (a(Cs)) of about 1.6 G. The pi-s-pi-electronic coupling can be turned on or off via the addition or removal of cesium cations. Analogous pi-s-pi-electronic coupling is observed in the 1,4-bis(9-methyl-9H-fluoren-9-yl)benzene-cesium system.
Stevenson
Cheryl D
CD
Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA. cdsteve@ilstu.edu
Kiesewetter
Matthew K
MK
Reiter
Richard C
RC
Chebny
Vincent J
VJ
Rathore
Rajendra
R
D000838:Anions / Q000737:chemistry*; D002586:Cesium / Q000737:chemistry*; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D015394:Molecular Structure
D000838:Anions; D005609:Free Radicals; D002586:Cesium