Supramolecular Circular Helicates Formed by Destabilisation of Supramolecular Dimers

Hamblin, J. Nicole; Tuna, Floriana; Bunce, Siona; Childs, Laura J.; Jackson, Alexander; Errington, William; Alcock, Nathaniel W.; Nierengarten, Hélène; Dorsselaer, Alain Van; Leize‐Wagner, Emmanuelle; Hannon, Michael J.

doi:10.1002/chem.200700848

Cited by 37 publications

(20 citation statements)

References 90 publications

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“…In this case a bis-bidentate ligand containing a 1,3-bis(aminomethyl)phenyl spacer formed linear dimers with tetrahedral metal ions and trinuclear circular helicates with octahedral metal ions. 10 Other reports have cited inter-strand CHÁ Á Áp interactions as the principal driving force for the preferential formation of high complexity cyclic assemblies over their dimeric In this communication we describe how the formation of either dinuclear double-stranded or pentanuclear circular helicates can be controlled by inter-ligand steric interactions which, in turn, are governed by the size of the metal ion. This approach allows for the specific formation of either of the two structures and gives valuable insight into some of the factors which control the formation of cyclic helicates.…”

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confidence: 86%

Controlling the formation of metallosupramolecular assemblies by metal ionic radii

et al. 2010

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The formation of either dinuclear double-stranded or pentanuclear circular helicates from a ligand containing two tridentate domains separated by a phenylene unit can be controlled by inter-ligand steric interactions which themselves are governed by the size of the metal ion.Controlling the structure of multi-component assemblies is one of the leading challenges for the supramolecular chemist. One of the simplest assemblies is the dinuclear doublestranded helicate, and the rules that govern the formation of this species are largely established. [1][2][3][4][5][6][7] The formation of the helicates' higher nuclearity cousin, the cyclic helicate, is conversely less well understood. One of the major problems in the formation of these higher nuclearity assemblies is that the design principles that apply to helicate formation, i.e. using a ligand that contains two binding domains that coordinate different metal ions, equally apply to the formation of cyclic helicates. For the larger cyclic species to preside in solution, the formation of the entropically favoured dimer has to be prevented and this can be achieved by intermolecular interactions (e.g. templation by anions) 8 or by intramolecular interactions which stabilise the formation of the cyclic species relative to its double-stranded alternative. As an example of the first of these approaches, in the work carried out by Ward et al., a ligand with two bidentate domains separated by a 1,8-naphthalenediyl spacer was reported to form a simple mononuclear species with Cu(CF 3 SO 3 ), but in the presence of tetrafluoroborate, a tetranuclear cyclic helicate [Cu 4 L 4 ] 4+ was observed. 9 Hannon et al., on the other hand, demonstrated that a metal ion's preference for different coordination geometries could affect the self-assembly outcome. In this case a bis-bidentate ligand containing a 1,3-bis(aminomethyl)phenyl spacer formed linear dimers with tetrahedral metal ions and trinuclear circular helicates with octahedral metal ions. 10 Other reports have cited inter-strand CHÁ Á Áp interactions as the principal driving force for the preferential formation of high complexity cyclic assemblies over their dimeric In this communication we describe how the formation of either dinuclear double-stranded or pentanuclear circular helicates can be controlled by inter-ligand steric interactions which, in turn, are governed by the size of the metal ion. This approach allows for the specific formation of either of the two structures and gives valuable insight into some of the factors which control the formation of cyclic helicates.The ligand L 1 , which was prepared by the reaction of 2,2 0 -bipyridine-6-thioamide with 1,3-di(a-bromoacetyl)benzene, contains two tridentate binding domains separated by a phenylene ring (Fig. 1) was confirmed by a single crystal X-ray diffraction study (Fig. 2).z In the solid-state the ligand partitions into two tridentate domains, each comprising a thiazole-pyridyl-pyridyl

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Controlling the formation of metallosupramolecular assemblies by metal ionic radii

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“…A few other routes to select the nuclearity of polymetallic d‐block or lanthanide helicates that incorporate diimine‐based ligands have also been explored 16. In these examples, the selection of a given assembly is governed by the choice of coordination geometry and ionic radii of the metal ions,15b, 17, 18 fine‐tuning of the ligand design,19 and post‐coordination of a ligand to a double‐stranded helicate assembly 20. Other reports also mention the role of interstrand CH⋅⋅⋅π interactions to govern the formation of circular helicates over dimeric assemblies 19.…”

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A Remarkable Solvent Effect on the Nuclearity of Neutral Titanium(IV)‐Based Helicate Assemblies

Weekes¹,

Diebold²,

Mobian³

et al. 2014

Chemistry A European J

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The spontaneous self-assembly of a neutral circular trinuclear Ti(IV) -based helicate is described through the reaction of titanium(IV) isopropoxide with a rationally designed tetraphenolic ligand. The trimeric ring helicate was obtained after diffusion of n-pentane into a solution with dichloromethane. The circular helicate has been characterized by using single-crystal X-ray diffraction study, (13) C CP-MAS NMR and (1) H NMR DOSY solution spectroscopic, and positive electrospray ionization mass-spectrometric analysis. These analytical data were compared with those obtained from a previously reported double-stranded helicate that crystallizes in toluene. The trimeric ring was unstable in a pure solution with dichloromethane and transformed into the double-stranded helicate. Thermodynamic analysis by means of the PACHA software revealed that formation of the double-stranded helicates was characterized by ΔH(toluene)=-30 kJ mol(-1) and ΔS(toluene)=+357 J K(-1) mol(-1) , whereas these values were ΔH(CH2 Cl2 )=-75 kJ mol(-1) and ΔS(CH2 Cl2 )=-37 J K(-1) mol(-1) for the ring helicate. The transformation of the ring helicate into the double-stranded helicate was a strongly endothermic process characterized by ΔH(CH2 Cl2 )=+127 kJ mol(-1) and ΔH(n-pentane)=+644 kJ mol(-1) associated with a large positive entropy change ΔS=+1115 J K(-1) ⋅mol(-1) . Consequently, the instability of the ring helicate in pure dichloromethane was attributed to the rather high dielectric constant and dipole moment of dichloromethane relative to n-pentane. Suggestions for increasing the stability of the ring helicate are given.

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“…[3] The understanding of the interplay between the metals and the ligands in helicates and their applications in the selective preparation of complicated organised chemical architectures remains the subject of systematic investigations, with great potential applications in asymmetric synthesis [4] and in the development of double-helical molecular architectures because life itself is encoded within double-helical DNA arrays. [5] Furthermore, heteroscorpionates are amongst the most versatile types of tridentate ligand and they can coordinate to a wide variety of elements. [6,7] In the last decade our research group has contributed widely to this field, designing new heteroscorpionate ligands related to the bis(pyrazol-1yl)methane system and incorporating several pendant donor arms.…”

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Straightforward Generation of Helical Chirality Driven by a Versatile Heteroscorpionate Ligand: Self‐Assembly of a Metal Helicate by Using CHπ Interactions

Otero

Lara‐Sánchez

Fernández‐Baeza

et al. 2010

Chemistry A European J

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The assembly of architecturally sophisticated, high-nuclearity coordination complexes from the reactions of relatively simple ligands with suitable metal ions remains an area of intense activity driven not only by the aesthetic appeal of the structures, but also by the potentially wide applications of the resulting supramolecular entities as functional materials.[1] In particular, stereochemically well-defined building blocks are needed for the assembly of metallo-supramolecular structures, the dimensions of which are greater than those found in traditional covalent-based chemistry.[2] Helicates represent one of the paradigmatic branches of supramolecular architecture and these metallo-supramolecular arrays that contain one or more strand ligands have attracted much attention.[3] The understanding of the interplay between the metals and the ligands in helicates and their applications in the selective preparation of complicated organised chemical architectures remains the subject of systematic investigations, with great potential applications in asymmetric synthesis [4] and in the development of double-helical molecular architectures because life itself is encoded within double-helical DNA arrays. [5] Furthermore, heteroscorpionates are amongst the most versatile types of tridentate ligand and they can coordinate to a wide variety of elements. [6,7] In the last decade our research group has contributed widely to this field, designing new heteroscorpionate ligands related to the bis(pyrazol-1-yl)methane system and incorporating several pendant donor arms.[8] Acetamide and thioacetamide heteroscorpionate ligands exhibit high versatility in terms of coordination modes due to the existence of three possible tautomers (Scheme 1).[9] Inspired by this versatility and taking into consideration tautomer c, which could be capable of forming a helical surface by attachment to metal atoms, we attempted to generate a series of single-helical dinuclear complexes that could be appropriate building blocks to self-assemble into supramolecular helical structures. Herein, we report the [a] Prof.

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Supramolecular Circular Helicates Formed by Destabilisation of Supramolecular Dimers

Cited by 37 publications

References 90 publications

Controlling the formation of metallosupramolecular assemblies by metal ionic radii

Controlling the formation of metallosupramolecular assemblies by metal ionic radii

A Remarkable Solvent Effect on the Nuclearity of Neutral Titanium(IV)‐Based Helicate Assemblies

Straightforward Generation of Helical Chirality Driven by a Versatile Heteroscorpionate Ligand: Self‐Assembly of a Metal Helicate by Using CHπ Interactions

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