Conformal groups symmetry properties

The crystal structures of (EDT-TTFBr2)2MX4 and (EDO-TTFBr2)2MX4 are quite similar, although the space group symmetry is different in these two systems. However, this difference comes only from the conformation of terminal six-membered rings of the donor molecules, which plays no important role in the physical properties of the present salts. The donor molecules are stacked in a head-to-tail manner to form quasi-one-dimensional columns as shown in Fig. 6a. 

The same relationships hold for D /, symmetric molecules when ft, is set to zero (44). For both C3/, and D3), symmetry, the depolarization ratio is expected to be p = 1.5. However, the converse need not be true a depolarization ratio of close to 1.5 does not prove a point group with a threefold rotational axis. The molecule may be conformationally flexible then HRS detects a superposition of (ft) of the different conformers. A case in point is l,3,5-trinitro-2,4,6-triisopropylaminobenzene which exists as an interconverting mixture of strongly distorted boat and twist-boat forms (Wolff etal., 1993), with approximate C5 and C2 symmetry, respectively, but still shows a depolarization ratio of close to 1.5 (Verbiest et al., 1994 Wortmann et ai, 1997). Even in the case of conformational homogeneity it may still strongly deviate from the ideal symmetry provided the impact of conformational distortion on the electronic properties is not great. 

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