Phenylenes topologies

Figure 4.2. Simple phenylene topologies (a) linear [4]-, (b) angular [4]-, (c) zigzag [4]-, (d) branched [4]-, (e) (mixed) bent [4]-, and (f) circular [6 phenylene.

Eickmeier, C., Holmes, D., Junga, H., et al. (1999) A novel phenylene topology total syntheses of zigzag [4] and [5]phenylene. Angewandte Chemie International Edition, 38(6), 800-804. 

The electronic properties of the ortho and para topologies share a lot in common due to their similar mesomeric effects. Thus, electronic configurations, analogous to the ones shown in Fig. 3 for p-phenylene-linked bis(diradicals), are expected to be operative for the systems discussed in this section. An important difference, though, between the ortho topology, on one hand, and the para and meta topologies, on the other, is the proximity of the two reactive centers in the former, which allows for intramolecular reactions not possible in the latter. This extra complication makes the study of o-phenylene-linked bis(diradicals) more challenging, and, perhaps, is responsible that such systems have not been as widely studied. 

The most easily identifiable characteristics are those related to the shape of the complexes, with their double-stranded helical cores. In this respect, the electrochemical and photochemical properties of Cu2(K-84)2+ are not much different from those of the open-chain helical precursor or its O-methylated version. The strong electronic coupling between the two copper centers is clearly a consequence of the 1,3-phenylene bridges between the two complex subunits and the topological properties of the ligand have virtually no influence. 

Crystal structure of MOF-5. (a) Z114O tetrahedra joined by benzenedicarboxylate linkers. H atoms are omitted for clarity, (b) The topology of the framework (primitive cubic net) shown as an assembly of i/iu (>)()— clusters (represented as truncated tetrahedra) andp-phenylene (-CgFLj-) links (represented by rods). From O. M. Yaghi, M. O Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, and J. Kim, Nature 423, 705-14 (2003). 

Paracyclophane (i)1 2) is characterized by the close vicinity of the phenylene rings, which are yoked face to face in parallel planes. Their distance is substantially (by more than 0.3 A) shorter than the van der Waals distance in common crystalline arenes. This strange topology gives rise to the consequences indicated below ... 

Another interesting consequence of the Ji-topology of an extended system can be demonstrated when comparing the electron-transfer behavior of the para-substituted phenylene species 33 with that of their corresponding ortho-... 

These results strongly suggest that the electrochemical properties of the knots are not governed by the topological factors alone. They are obviously also very sensitive to structural parameters which become prevailing when switching from the aliphatic flexible spacers between two phenanthroline units to the more rigid 1,3-phenylene spacer in knot CuCu.l4 +. 

Three limiting topologies (Fig. 16), based upon 1,3-phenylene coupling unit, can be considered for Class I polyarylmethyl triradicals quasi-linear, quasi-cyclic, and macrocyclic (calyx[3]arene-based).3,85 89... 

In order to synthesize the topologically equivalent metallacryptate 65 in an analogous manner to 64, the w-phenylene spacer was substituted by an m-pyridylene spacer. Deprotonation of l,l -(2,6-pyridylene)bis-l,3-(4-dimethyl)pentanedione 63... 

Furtula, B., Gutman, I., Tomovic, Z., Vesel, A. and Pesek, I. (2002) Wiener-type topological indices of phenylenes. Indian J. Chem., 41, 1767—1772. 

Gutman, I. (1995) The topological indices of linear phenylenes./. Serb. Chem. Soc., 60, 99-104. 

These monolayers (SAMs) are characterised by UV-Vis, fluorescence and Raman spectroscopy. This is made easy because of the presence of benzene cores within the acetylene and linker chains, these being made of poly(l,4-phenylene-l,3-butadiynylene) polymers. AFM then provides the topology, i.e. shapes (contours), thicknesses and aspect ratios (length and width), of the 2D S.AMs. This is done at all stages including those described below. 

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