Trinuclear assembly

Rawashdeh-Omary, M.A., Pietroni, B.R. and Staples, R.J. (2000) Supramolecular chain assemblies formed by interaction of a B molecular acid complex of mercury with B-Base trinuclear gold complexes. Journal of the American Chemical Society, 122, 11264. 

In order to assess how the bulk of the arene influences the structure of such stacked assemblies, the adducts of 137 with toluene, o-, m-, and -xylenes, and mesitylene have been synthesized and structurally characterized.236 These adducts tend to form extended binary stacks similar to those found in [137-benzene], The substituted benzene molecules adopt an apparently random orientation with respect to the trinuclear core of 137, thus suggesting that the binding might be... 

The use of other potential bidentate ligands also permits the synthesis of cyclic trinuclear gold complexes that form, by stacking, supramolecular assemblies. This is the case for the trinuclear complex [Au3(NC5H4)3] [47] that crystallizes in two... 

Lacunary spedes can act as structural motifs with numerous metal cations, leading to mono-, di- and trinuclear transition-metal-substituted POMs according to the number of vacant sites. The metal incorporation involves the reaction of aquated first-row and occasionally second-row d-block metal ions, M(H20)6z +, with a lacunary POM derived from the Keggin, Wells-Dawson and other POM families. In addition, lacunary spedes assemble into large POM structures, either directly or with incorporation of metal ion linkers. 

Of course, it is quite possible to further extend these assembly processes to give doublehelical complexes with even more bond crossings. For example, a double-helical complex with three bond-crossings should result from the reaction of a molecular thread containing three metal-binding domains with three tetrahedral metal ions (Fig. 7-32). An example of the assembly of such a trinuclear double-helical complex is seen in the formation of 7.52 from the reaction of 7.51 with silver(i) salts (Fig. 7-33). 

Figure 7-33. The interaction of the ligand 7.51, which contains three didentate metal-binding domains with copper(i) or silver(i) ions, results in the assembly of a trinuclear double-helical structure, 7.52.

We present here a few examples of enantiomeric supramolecular absolute structures. In fact, many supramolecular diastereomers with chiral ligands have been isolated stereoselectively. For example, enantiomers of the chiral self-assembled triple helicates trinuclear [Ni3(L)3](C104)6 (L = tris(bpy)) and dinuclear [Co2(L)3]4 + (L = 5-bismpmb) were partially resolved by SP Sephadex chromatography.63,64 The ligands and structures are given in Figure 5.17a and b. 

Kramer R et al (1993) Self-assembly, structure, and spontaneous resolution of a trinuclear triple-helix from an oligobipyridine ligand and Ni(II) ions. Angew Chem Int Ed Engl 32 703-706... 

When four monodentate ligands, including solvent molecules, are bound to the central metal ion, a trans disposition of the bridging cyanides is the preferred orientation [Fig. 18(c)]. The only exception to this trend is found in the structure of cw- [(pcq)Fe (CN)3l2[Mn (Me0H)2(H20)2] (119) [Fig. 18(kinetic products, given the presence of terminal cyanides or labile solvent molecules in their structures. The availability of these potential coordination sites renders such trinuclear complexes convenient scaffolds for the assembly of higher nuclearity clusters or extended structures (Section V). 

Of specific relevance to MCOs are biomimetics that attempt to reproduce the intramolecular electron transfer between a type 1 site and a bi- or trinuclear copper cluster, or model the trinuclear cluster itself Three recent reports exemplify these attempts. Lever and his coworkers synthesized the tetracop-per assembly shown in Figure 5(a) and demonstrated that it was reduced stepwise by 3e Cu(II)-Cu2(II,II)-Cu(II) - Cu(I)-Cu2 (II,II)-Cu(II) — Cu(I)-Cu2 (II,II)-Cu(I) / Cu(I)-Cu2(I,II)-Cu(II) — Cu(I)-Cu2(I,II)-Cu(I). Figure 5(b) illustrates the polarogram for this reduction. EPR spectra were consistent with the reduction scheme proposed and indicated that the last of these 1 e electron transfers was associated with the reduction potential of —0.42 V. In summary, this complex... 

Figure 8 Assembly of trinuclear monocapped units into tetranu-clear frameworks the structure ofNb4Clio(PMe3)4...

Figure 2.40 Crystal structure of [Eu3(L )3(H20)e]. View of the trinuclear complex (a) along and (b) perpendicular to the threefold axis [45]. (Reproduced with permission from S. Zebret, N. Dupont, G. Bemardinelli and J. Hamacek, Self-assembly of a trinuclear luminescent europium complex, Chemistry-A European Journal, 2009,15, 3355-3358. Wiley-VCH Verlag GmbH Co. KGaA.)...

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