New Polymorphs of Perylene:Tetracyanoquinodimethane Charge Transfer Cocrystals
New Polymorphs of Perylene:Tetracyanoquinodimethane Charge Transfer Cocrystals
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DOI：
10.1021/acs.cgd.7b01391
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发表时间：
2018-04-01
影响因子：
3.8
通讯作者：
Da Como, E.
中科院分区：
文献类型：
--
作者：
Henderson, J.;Masino, M.;Da Como, E.
我们报告了两种迄今为止未知的电荷转移（CT）共晶二萘嵌苯：四氰基对醌二甲烷（TCNQ）的多晶型物，其通过物理气相传输（PVT）在氩气气氛中生长。其中一种名为 beta 的多晶型物的化学计量比为 1:1，并添加到化学计量比为 1:1（α）、2:1 和 3:1 的三种已知结构中。有趣的是，低于 (280 +/- 10) K，β 结构会经历相变，转变为我们所说的 γ 多晶型物，晶胞减半，对称性从单斜晶系减少到三斜晶系。两种新的晶体结构都呈现出两个具有不同分子间和分子内几何形状的交替堆叠。在堆栈 S-I 中，苝分子显示出与平面性的显着偏差，萘分子内部分之间的角度为 6.69 度，苝和 TCNQ 分子质心偏移了 1.95 埃。在第二组 S-II 中，苝是平面的，并且质心几乎重合。由振动红外光谱补充的键长结构研究表明，在新的多晶型物中，电荷转移程度 rho 可以是 0 或 0.12。较高的离子度值归因于 S-II 中的供体-受体对，而 S-I 中的分子更接近中性。因此，供体-受体对的离子性取决于堆叠，并且与我们重新确定为 rho = 0.15 +/- 0.05 的 α 多晶型物的离子性相当。
We report two hitherto unknown polymorphs of the charge transfer (CT) cocrystal perylene:tetracyanoquinodimethane (TCNQ) grown by physical vapor transport (PVT) in argon atmosphere. One of the polymorphs, named beta, has stoichiometry 1:1 and adds to the three known structures with stoichiometry 1:1 (alpha), 2:1, and 3:1. Interestingly, below (280 +/- 10) K the beta structure undergoes a phase transition to what we refer to as the gamma polymorph, with halving of the unit cell and reduction of symmetry from monoclinic to triclinic. Both new crystal structures present two alternating stacks with different intermolecular and intramolecular geometries. In stack S-I the perylene molecules show substantial deviations from planarity, with the angle between the naphthalene intramolecular moieties of 6.69 degrees, and with the perylene and TCNQ molecular centroids shifted by 1.95 angstrom. In the second stack, S-II, the perylene is planar, and the centroids almost coincident. Structural investigations on bond length complemented by vibrational IR spectroscopy indicate that in the new polymorphs the degree of charge transfer, rho, can be 0 or 0.12. The higher value of ionicity to be due to donor-acceptor pairs in the S-II, while molecules in S-I are closer to neutrality. Thus, the ionicity of the donor-acceptor pair depends on the stack and is comparable to that of the alpha polymorph which we redetermined as rho = 0.15 +/- 0.05.