| Abstract
| - The biradicals 1,8-di([5]trovacenyl)naphthalene (6), 1,5-di([5]trovacenyl)naphthalene (7),and 1,3-di([5]trovacenyl)benzene (8) and the monoradical 1-[5]trovacenylnaphthalene (9) havebeen prepared and studied by means of single-crystal X-ray diffraction (6, 8, 9), cyclicvoltammetry, EPR spectroscopy, and magnetic susceptometry. Comparison of the magneticproperties of 6−9 reveals that π-stacking, as encountered in 6, largely enhances exchangeinteraction between the two singly occupied V(3dz2) orbitals. The effect of π-stacking on theelectrochemical properties, as manifested in the redox splitting between consecutive electrontransfer steps, is less pronounced. Redox splittings δE1/2 for consecutive reductions exceedthose for oxidations of binuclear trovacenes, δE1/2(2+/+, +/0) being apparent for π-stacked6 only. Because of the orthogonality of the metal-centered redox orbitals V1(dz2) and V2(dz2)and the η5-cyclopentadienyl π-orbitals, electro- and magnetocommunication are indirectprocesses. Electrocommunication rests on changes of the donor/acceptor properties ofV1,V2 caused by oxidation or reduction which govern metal−ligand charge distribution; thelatter changes are transmitted via the spacer. Magnetocommunication takes the form ofantiferromagnetic coupling, which can be traced to spin polarization of filled π-orbitals ofthe bridge by orthogonal singly occupied vanadium 3dz2 orbitals.
- [5-5]Bitrovacenes have been synthesized in which the two paramagnetic units adopt head-on (6••) compared to side-on (8••) positions. EPR and susceptometry studies reveal that magnetocommunication in π-stacked 6•• exceeds that encountered in side-on structered 8••. Electrocommunication, which governs the redox splitting δE1/2 of consecutive ET processes, depends less extensively on the disposition of the trovacene units.
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