title: Direct observation of bis(dicarbollyl)nickel conformers in solution by fluorescence spectroscopy: an approach to redox-controlled metallacarborane molecular motors.
abstract: As a continuation of work on metallacarborane-based molecular motors, the structures of substituted bis(dicarbollyl)nickel complexes in Ni(III) and Ni(IV) oxidation states were investigated in solution by fluorescence spectroscopy. Symmetrically positioned cage-linked pyrene molecules served as fluorescent probes to enable the observation of mixed meso-trans/dl-gauche (pyrene monomer fluorescence) and dl-cis/dl-gauche (intramolecular pyrene excimer fluorescence with residual monomer fluorescence) cage conformations of the nickelacarboranes in the Ni(III) and Ni(IV) oxidation states, respectively. The absence of energetically disfavored conformers in solution--dl-cis in the case of nickel(III) complexes and meso-trans in the case of nickel(IV)--was demonstrated based on spectroscopic data and conformer energy calculations in solution. The conformational persistence observed in solution indicates that bis(dicarbollyl)nickel complexes may provide attractive templates for building electrically driven and/or photodriven molecular motors.
authors.affiliation: International Institute of Nano and Molecular Medicine, School of Medicine, University of Missouri , Columbia, Missouri 65211, United States.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Safronov
authors.forename: Natalia I
authors.initials: NI
authors.lastname: Shlyakhtina
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Everett
authors.forename: Monika R
authors.initials: MR
authors.lastname: VanGordon
authors.forename: Yulia V
authors.initials: YV
authors.lastname: Sevryugina
authors.forename: Satish S
authors.initials: SS
authors.lastname: Jalisatgi
authors.forename: M Frederick
authors.initials: MF
authors.lastname: Hawthorne
mesh_terms: D001880:Boranes / Q000737:chemistry*; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D012996:Solutions; D013050:Spectrometry, Fluorescence
chemical_list: D001880:Boranes; D009942:Organometallic Compounds; D012996:Solutions; D009532:Nickel