Di([5]trovacenyl)ethyne, Di([5]trovacenyl)butadiyne, and Di-1,4-([5]trovacenylethynyl)benzene: Electrocommunication and Magnetocommunication Mediated by -C
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- 作者：Christoph Elschenbroich ; Jö ; rn Plackmeyer ; Mathias Nowotny ; Klaus Harms ; Jü ; rgen Pebler ; and Olaf Burghaus
- 刊名：Inorganic Chemistry
- 出版年：2005
- 出版时间：February 21, 2005
- 年：2005
- 卷：44
- 期：4
- 页码：955 - 963
- 全文大小：212K
- 年卷期：v.44,no.4(February 21, 2005)
- ISSN：1520-510X
文摘
The synthesis of dinuclear derivatives of trovacene (
7-C7H7)V(5-C5H5) (1
) is reported, in which ethynyl (6),butadiynyl (7), and 1,4-di(ethynyl)phenyl (8) groups serve as spacers between paramagnetic (S = 1/2) [5]trovacenylunits. The mononuclear precursors [5]trovacenylcarbaldehyde (2) and [5]trovacenylacetylene (4) are also described.Structural characterization by X-ray diffraction has been performed for 4, 6, 7, and 8. Electronic communicationas gleaned from cyclic voltammetry only manifests itself in the reduction processes where redox splitting 
E1/2(0/1-, 1-/2-) is resolved for 6 (E1/2 = 150 mV) and indicated for 7 (E1/2 
80 mV). Magnetocommunicationleads to exchange coupling of the two electron spins which reside in vanadium centered orbitals. The valuesJEPR(6) = (-)0.92, JEPR(7) = (-)0.56, and JEPR(8) = (-)0.005 cm-1 are derived from the 51V hyperfine patterns.Accordingly, attenuation of exchange interaction by oligoalkyne spacers is weak, corresponding to a factor of 0.6only per added -C
C- unit. In the determination of very weak long distance exchange interactions, EPR excelsbecause of the range 5 × 10-4 J 1.5 cm-1 accessible in the case of 51V as a reporting magnetic nucleus andbecause competing intermolecular exchange is quenched in dilute fluid solution. This is demonstrated by the valueJ
(7) = -3.84 cm-1 obtained from a magnetic susceptibility study, which exceeds JEPR(7) by a factor of 7. Thesmall magnitude of spin exchange interaction between trovacene units reflects the fact that the spin bearing V3dz2orbital is virtually orthogonal to the 
-perimeter ligand orbitals and weakly overlapping only with the a1g(
) ringorbitals, creating two bottlenecks for spin-exchange in the spacer-containing ditrovacenes.
7-C7H7)V(5-C5H5) (1) is reported, in which ethynyl (6),butadiynyl (7), and 1,4-di(ethynyl)phenyl (8) groups serve as spacers between paramagnetic (S = 1/2) [5]trovacenylunits. The mononuclear precursors [5]trovacenylcarbaldehyde (2) and [5]trovacenylacetylene (4) are also described.Structural characterization by X-ray diffraction has been performed for 4, 6, 7, and 8. Electronic communicationas gleaned from cyclic voltammetry only manifests itself in the reduction processes where redox splitting E1/2(0/1-, 1-/2-) is resolved for 6 (E1/2 = 150 mV) and indicated for 7 (E1/2 80 mV). Magnetocommunicationleads to exchange coupling of the two electron spins which reside in vanadium centered orbitals. The valuesJEPR(6) = (-)0.92, JEPR(7) = (-)0.56, and JEPR(8) = (-)0.005 cm-1 are derived from the 51V hyperfine patterns.Accordingly, attenuation of exchange interaction by oligoalkyne spacers is weak, corresponding to a factor of 0.6only per added -CC- unit. In the determination of very weak long distance exchange interactions, EPR excelsbecause of the range 5 × 10-4 J 1.5 cm-1 accessible in the case of 51V as a reporting magnetic nucleus andbecause competing intermolecular exchange is quenched in dilute fluid solution. This is demonstrated by the valueJ(7) = -3.84 cm-1 obtained from a magnetic susceptibility study, which exceeds JEPR(7) by a factor of 7. Thesmall magnitude of spin exchange interaction between trovacene units reflects the fact that the spin bearing V3dz2orbital is virtually orthogonal to the -perimeter ligand orbitals and weakly overlapping only with the a1g() ringorbitals, creating two bottlenecks for spin-exchange in the spacer-containing ditrovacenes.