Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
J Am Chem Soc. 2010 Mar 3;132(8):2684-94. doi: 10.1021/ja908768a.
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(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(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.
我们报告了首例苯并薁并菲咯啉中性自由基导体（18）的制备，并展示了该化合物表现出前所未有的固态行为：结构主要由两组分子间相互作用决定：（1）沿[0 0 1]方向的苯并薁并菲咯啉的π-链结构与π-重叠；（2）沿[0 1 0]方向涉及一对碳原子（C4）的链间重叠。π-链型堆积模式让人联想到先前报道的菲咯啉自由基，室温结构（空间群 P2/c）以及西格玛（RT）= 0.03 S/cm 的电导率和类玻色子磁 susceptibility 最好用共振价键（RVB）模型来描述。与相邻自由基之间的 C4 碳原子对形成西格玛电荷密度波（sigma-CDW）有关的链间相互作用是不稳定的，这种相的特征是 P2(1)/c 空间群，涉及沿[0 1 0]方向的单位晶胞的两倍。RVB 和 CDW 相在整个温度范围内（15-293 K）竞争结构占有率，RVB 相在 15 和 293 K 占主导地位，sigma-CDW 相在 150 K 时达到约 60%的最大结构占有率，在该温度下，它对磁性和电导率产生明显的影响。
