Columnar stacked structures

Figure 1 Schematic representation of the band formation in a columnar stack structure. (A) Semiconductor based on integral oxidation state complex. (B) One-dimensional metal produced by partial oxidation and resulting in a non-integral oxidation state...

The simple integral oxidation state compounds behave as either insulators or semiconductors. The tetracyanoplatinates of monovalent cations form anionic columnar stack structures with conductivities in the range 10-4—10-9 fi 1 cm-1 and a systematic variation of cry with 1 /electrical conductivity can be increased by as much as a factor of 104 by pressures up to 180 kbar.27... 

Neutral square coplanar complexes of divalent transition metal ions and monoanionic chelate or dianionic tetrachelate ligands have been widely studied. Columnar stack structures are common but electrical conductivities in the metal atom chain direction are very low and the temperature dependence is that of a semiconductor or insulator. However, many of these compounds have been shown to undergo partial oxidation when heated with iodine or sometimes bromine. The resulting crystals exhibit high conductivities occasionally with a metallic-type temperature dependence. The electron transport mechanism may be located either on predominantly metal orbitals, predominantly ligand re-orbitals and occasionally on both metal and ligand orbitals. Recent review articles deal with the structures and properties of this class of compound in detail.89 90 12... 

The conductivity in the stack direction is 5 x 10 cm and the compound displays semiconductor behaviour from room temperature down to 110 K with a transition between 220-180 The structure of Rb[Pt S2C2(CN)2 2] 2H20 contains the planar anions arranged in a dimeric eclipsed configuration to form a columnar stacked structure. The conductivity in the metal atom chain direction is 2.5 x 10 cm . Polycrystalline. samples of compounds of the type... 

Much attention is currently devoted to the synthesis and properties of shape-persistent macrocycles[l]. Such compounds are interesting for a variety of reasons including formation of columnar stacks potentially capable of performing as nanopores for incorporation into membranes or for the generation of nanowires[2]. Furthermore, in shape-persistent macrocycles incorporating coordination units, enc/o-cyclic metal-ion coordination may be exploited to generate nanowires[3], whereas e.ro-cyclic coordination can be used to construct large arrays of polynuclear metal complexes[4]. Shape-persistent macrocycles with reactive substituents may also be linked to other units to yield multicomponent, hierarchical structures. 

Replacement of the N-methyl groups with the bulkier N-benzyl or N-isopropyl groups did not reproduce any columnar stack in the crystal structure that was found in 9, and no solvoluminescent behavior was observed [110, 111]. The closest intermolecular Au-Au contact of 3.662 and 6.417 A in the crystal packing in 10a and 10b (Fig. 14), respectively, indicated the absence of any intermolecular aurophilic interaction. 

Analysis of the electron density of the dimer sheds some light about the nature of the intermolecular interactions that produce such a drastic shortening in the distances between macrocycles within a column. Thus, the arrangement of the SubPz 278 (X = F) into columnar crystalline structures implies more than a simple p-stacking along the c direction but also the presence of three beps between the fluorine atoms of one of the molecules and the fluorosubazaporphyrin that is above. In addition, three beps are found that can be associated to n-n interaction between the two molecules (Fig. 10). 

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