Resonating valence bond and {sigma}-charge density wave phases in a benzannulated phenalenyl radical.
We report the preparation of the first benzannulated phenalenyl neutral radical conductor (18), and we show that the compound displays unprecedented solid state behavior: the structure is dominated by two sets of intermolecular interactions: (1) a {pi}-chain structure with superimposed {pi}-overlap of the benzannulated phenalenyls along [0 0 1], and (2) an interchain overlap involving a pair of carbon atoms (C4) along [0 1 0]. The {pi}-chain-type stacking motif is reminiscent of previously reported phenalenyl radicals and the room temperature structure (space group P2/c) together with the conductivity of {sigma}{sub RT} = 0.03 S/cm and the Pauli-like magnetic susceptibility are best described by the resonating valence bond (RVB) model. The interchain interaction is unstable with respect to the formation of a {sigma}-charge density wave ({sigma}-CDW) involving pairs of C4 carbon atoms between adjacent radicals and this phase is characterized by the P2{sub 1}/c space group which involves a doubling of the unit cell along the [0 1 0] direction. The RVB and CDW phases compete for structural occupancy throughout the whole temperature range (15-293 K) with the RVB phase predominating at 15 and 293 K and the {sigma}-CDW phase achieving a maximum structural occupancy of about 60% at 150 K where it produces clearly discernible effects on the magnetism and conductivity.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 979879
- Report Number(s):
- ANL/MSD/CP-65014; JACSAT; TRN: US201011%%444
- Journal Information:
- Science, Vol. 132, Issue 8 ; 2010; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- ENGLISH
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