Anion-templated assembly

Beer, P. D., Sambrook, M. R., Curiel, D., Anion-templated assembly of interpenetrated and interlocked structures. Chem. Commun. 2006, 2105-2117. 

For a number of years the research interests of the Beer group have covered many areas of macrocychc coordination and supramolecular chemistry. This article reviews our latest results of current research by focusing on three major sections sensing of cations and anions anion templated assembly of pseudorotaxanes and rotaxanes, and metal-directed self-assembly using the dithiocaibamate ligand. 

Anion templated assembly of mechanically interlocked structures 07CSR211. 

Anion-templated assembly of interpenetrated and interlocked structures 06CC2105. 

Fig. 1 The anion-templated assemblies reported by Hawthorne. WWW. dekker. com.)...

Campos-Fernandez, C.S. Clerac. R. Dunbar, K.R. A one-pot, high yield synthesis of a paramagnetic nickel square from divergent precursors by anion template assembly. Angew. Chem.. Int. Ed. 1999. 38 (23). 3469-3477. 

Sambrook MR, Curiel D, Hayes EJ, Beer PD, Pope SJA, Eaulkner S (2006) Sensitised near infrared emissitm from lanthanides via anion-templated assembly of d-f heterraiuclear [2] pseudorotaxanes. New J Chem 30 1133—1136... 

Metrangolo P, Pilati T, Terraneo G, Biella S, Resnati G (2009) Anion coordination and anion-templated assembly under halogen bonding control. CrystEngComm 11 1187... 

Serpell CJ, Kilah ML, Costa PJ, Felix V, Beer PD (2010) Halogen bond anion templated assembly of an imidazolium psendorotaxane. Angew Chem Int Ed 49 5322... 

Fleming JS, Mann KLV, Carraz C-A, Psillakis E, Jeffery JC, McCleverty JA, Ward MD (1998) Anion-templated assembly of a supramolecular cage complex. Angew Chem Int Ed 37 1279-1281... 

One of the most successful approaches to the synthesis of metalla-supramolecular systems has been by templated self-assembly processes. Most of the templating agents used by synthetic chemists are either cationic or neutral species. Anions, on the other hand, have only fairly recently been successfully utilized as templates. The new metalla-macrocycles [Pd2Ni2(atu)4(PPh3)4X]3+ (atu = deprotonated amidinothiourea, X = C1, Br, I) have been prepared using anion templated syntheses. Only in the presence of each of these three halides are the metalla-macrocycles... 

The spherical metalla-cages [M2Ni4(atu)8X]3+ (M=Ni, 8a,b Pd, 9a,b X=C1, Br) have also been prepared by an anion templated process. These species can be obtained by reacting Ni(atu)2 with NiX2 and [PdX2(PhCN)2] respectively. Once again the formation of these metalla-assemblies is highly dependent on the pres-... 

The anion-templated synthesis of rotaxanes first introduced by Vogtle has now been employed by others to produce other interlocked assemblies. Schalley for example [68], has reported an improved yield for the synthesis of rotaxanes by... 

De Mendoza reported the first example of anion-directed helix formation in 1996 [91]. The assembly of this helical structure relies, not only on electrostatic interactions between the anionic template and the positively charged strands, but also on hydrogen bonding. The tetraguanidinium strand 69 (see Scheme 34) self-assembles around a sulfate anion via hydrogen bonding to produce a double helical structure. The formation of this assembly and its anion-dependence was proposed on the basis of NMR and CD spectroscopic studies. 

Such complexes form a precursor to a full discussion of the vast and highly topical field of self-assembly (Chapter 10). We consider them here since they resemble structurally the types of compounds discussed in Section 4.7, but unlike metal-based anion receptors the simple thermodynamic equilibrium between host, anion and complex is not the only process occurring in solution. In fact multiple equilibria are occurring covering all possible combinations of interaction between anions, cations and ligands. These systems have the appeal that the formation of particular metal coordination complexes are thus subject to thermodynamic anion templating (cf. the thermodynamic template effect in macrocycle synthesis, Section 3.9.1) and vice versa. 

Anion templating is a formidable approach to the construction of large coordination complexes, cages and polyhedra by self-assembly using relatively simple ligands and we will examine some anion templated systems as part of our discussion of self-assembly in Chapter 10. For example, a... 

Scheme 5.4 Anion templated self-assembly of gold(I) phosphine macrocycles.34...

Figure 4. Anion-templated self-assembly ofpseudorotaxanes. Recognition of the anion by macrocycle results in the formation of an interpenetrated structure.

Building on their technique for assembling [2]pseudorotaxanes through anion templation, P.D. Beer and S. Faulkner have designed supramolecular d-f heterometallic assemblies in which the luminescence of the lanthanide ion is sensitized by a d-transition metal ion (fig. 94). 

The templation of metal-ligand assemblies by anions can occur in two ways a Lewis acid/base interaction between the anion and the metal or via hydrogen bonding between the anion and organic ligands. One system that displays both of these interactions is the halide templated assembly between 19, one of the tautomeric forms of amidinothiourea (Scheme 5), and NiX2 (X=C1, Br) [55]. In the... 

Fig. 5 Anion-templated self-assembly of two coordination squares and a pentagon, and their dynamic interconversion...

Campos-Femandez C, Schottel BL, Chifotides HT et al (2005) Anion template effect on the self-assembly and interconversion of metallacyclophanes. J Am Chem Soc 127 12909-12923... 

In contrast to most other circular helical systems, 44 assembles from the metal ions and the ligands alone without the support of an anionic template. 

Acetone-sensitized irradiation of uracil (107) with ethene affords the adduct (108) in 75% yield. This compound can be transformed into the cyclobutane derivative (109) in an overall yield of 52%. The intramolecular cyclization of the dinucleotide model (110) has been investigated. The reaction affords the cycloadduct (111) by irradiation using wavelengths > 300 nm. The use of an anionic template for photochemical dimerization of a thymine system has been demonstrated. The thymine forms an assembly (112) with pyrophosphate. Irradiation of this brings about syn- 2 + 2)-cycloaddition of the thymine units. ... 

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