Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1517191 | Journal of Physics and Chemistry of Solids | 2008 | 8 Pages |
Abstract
Four molecular solids consisting of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical and benzylpyridinium or benzylquinolinium derivatives with molar ratios of 1:1 (1-3) and 2:1 (4) have been prepared and characterized. In the crystals of 1 and 3, TCNQâ monoanions and the corresponding cations form segregated stacks, which are regular in 1 but irregular in 3. Instead of segregated stacks, TCNQâ monoanions in 2 form isolated Ï-dimers. In the crystals of 4, two crystallographic independent TCNQ species possess almost equal fractional negative charge (ca. â0.5). Two types of TCNQ species form a tetrad, these tetrads make a TCNQ stack with the pattern â¦BAABâ¦BAAB⦠along the crystallographic a-b direction. The magnetisms for 1-4 can be simply explained by the formation of singlet spin state. A broken symmetry approach in a density functional theory framework at the ub3lyp/6-31 g level was used to calculate the magnetic exchange constants in 1-4. The results qualitatively demonstrate the observed magnetic properties.
Keywords
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Physical Sciences and Engineering
Materials Science
Electronic, Optical and Magnetic Materials
Authors
You-Cun Chen, Peng-Fei Wang, Guang-Xiang Liu, Heng Xu, Xiao-Ming Ren, You Song, Zhao-Ping Ni,