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Close encounters of the weak kind: Investigations of electron-electron interactions between dissimilar spins in hybrid rotaxanes

DOI: 10.1021/jacs.9b05590 DOI Help

Authors: Selena J. Lockyer (The University of Manchester) , Alistair J. Fielding (Liverpool John Moores University) , George F. S. Whitehead (The University of Manchester) , Grigore A. Timco (The University of Manchester) , Richard E. P. Winpenny (The University of Manchester) , Eric J. I. Mcinnes (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Chemical Society

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 17379

Abstract: We report a family of hybrid [2]rotaxanes based on inorganic [Cr7NiF8(O2CtBu)16]- (“{Cr7Ni}”) rings templated about organic threads that are terminated at one end with pyridyl groups. These rotaxanes can be coordinated to [Cu(hfac)2] (where hfac = 1,1,1,5,5,5-hexafluoroacetylacetone), to give 1:1 or 1:2 Cu:{Cr7Ni} adducts: {[Cu(hfac)2](py-CH2NH2CH2CH2Ph)[Cr7NiF8(O2CtBu)16]}, {[Cu(hfac)2][py-CH2NH2CH2CH3][Cr7NiF8(O2CtBu)16]}, {[Cu(hfac)2]([py-CH2CH2NH2CH2C6H4SCH3][Cr7NiF8(O2CtBu)16])2}, {[Cu(hfac)2]([py-C6H4-CH2NH2(CH2)4Ph][Cr7NiF8(O2CtBu)16])2}, and {[Cu(hfac)2]([3-py-CH2CH2NH2(CH2)3SCH3][Cr7NiF8(O2CtBu)16])2}, the structures of which have been determined by X-ray diffraction. The {Cr7Ni} rings and CuII ions both have electronic spin S = ½, but with very different g-values. Continuous-wave EPR spectroscopy reveals the exchange interactions between these dissimilar spins, and hence the communication between the different molecular components that comprise these supramolecular systems. The interactions are weak such that we observe AX or AX2 type spectra. The connectivity between the {Cr7Ni} ring and thread terminus is varied such that the magnitude of the exchange interaction J can be tuned. The coupling is shown to be dominated by through-bond rather than through-space mechanisms.

Journal Keywords: Supramolecular chemistry; rotaxanes; exchange coupling; EPR

Subject Areas: Chemistry


Instruments: I19-Small Molecule Single Crystal Diffraction