Metal Complex Not Stacked

The four systems listed in Table 6 consist of stacks of planar organic molecules surrounded by transition-metal complexes that are not closely associated with each other. All but the [Pt(bipy)2][TCNQ]3 system contain planar organic cations and metal dithiolene anions. The properties of these compounds vary considerably, so each system will be described briefly. 

The transition-metal component of [Pt(bipy)2][TCNQ]3 is also diamagnetic. The structure86 consists of stacks of trimers, [T CNQ], surrounded by non-interacting Pt(bipy)2+ cations. Adjacent trimers are closely spaced with an interplanar separation of only 3.33 A as compared with 3.23 A within the trimer. The magnetic properties of this system have been studied much less extensively than those of [TMPD]2[Ni(mnt)2]. Single crystal EPR spectra do show, however, that spins are interacting along the TCNQ stacks. Structurally, this compound is very different from the 1 2 compound [Pt(bipy)2][TCNQ]258 (Sect. 2) which forms Da stacks with the two TCNQ moieties 7-bonded to each other..  

S-S contacts of 3.48 A. Given the overall composition of the unit cell, this compound is most instructively formulated as [TTP]2[TiT+]2[Ni(edt)2 ]2. 

Electrical conductivity measurements of the [TTF]2[Ni(edt)2] and [TTT ]12[Ni(edt)2] systems show them to be semiconductors with conductivities of 10-3 and 30 Q-1cm-1, respectively. In both compounds, the direction of highest conductivity is along the stacks of organic molecules. Since the [TTT]i.2[Ni(edt)2] system contains chains of partially oxidized organic molecules that appear to be uniformly spaced along the stacking axis, a high conductivity would be expected. The low room-temperature conductivity (compared with other partially oxidized TTT salts) and its temperature dependence, which is typical of a semiconductor, are presumed to be a consequence of the postulated Peierls distortion. 

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Table 6. Structural data for segregated stack, integral oxidation state crystals with the metal complex not stacked ...

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