Template Synthesis

and, Jack K. Clegg; Lindoy, Leonard F.

doi:10.1002/9783527639502.ch5

Cited by 5 publications

(3 citation statements)

References 97 publications

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“…Unusually, this structure direction appears to be almost completely independent of the anions present, with the same 3D MOF arrangement being formed regardless of the chemical nature and size of the anion. This situation differs from the anion direction commonly found in supramolecular chemistry 35 , 36 as well as that seen previously in Group 14 tris(3-pyridyl) metal complexes, in which the chemical and physical characters of the anion normally have profound effects on supramolecular assembly. 34 …”

Section: Introductioncontrasting

confidence: 73%

Cation- and Anion-Mediated Supramolecular Assembly of Bismuth and Antimony Tris(3-pyridyl) Complexes

et al. 2021

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The use of antimony and bismuth in supramolecular chemistry has been largely overlooked in comparison to the lighter elements of Group 15, and the coordination chemistry of the tripodal ligands [Sb(3-py) 3 ] and [Bi(3-py) 3 ] (L) containing the heaviest p-block element bridgehead atoms has been unexplored. We show that these ligands form a common hybrid metal–organic framework (MOF) structure with Cu(I) and Ag(I) (M) salts of weakly coordinating anions (PF 6 – , SbF 6 – , and OTf – ), composed of a cationic substructure of rhombic cage (M) 4 (L) 4 units linked by Sb/Bi–M bonding. The greater Lewis acidity of Bi compared to Sb can, however, allows anion···Bi interactions to overcome Bi–metal bonding in the case of BF 4 – , leading to collapse of the MOF structure (which is also seen where harder metals like Li + are employed). This study therefore provides insight into the way in which the electronic effects of the bridgehead atom in these ligand systems can impact their supramolecular chemistry.

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Section: Introductioncontrasting

confidence: 73%

Cation- and Anion-Mediated Supramolecular Assembly of Bismuth and Antimony Tris(3-pyridyl) Complexes

et al. 2021

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“…Following Sauvage’s ground-breaking use of metal ions as templating species for the synthesis of MIMs [ 22 , 23 ], a variety of interactions have been utilized to arrange components prior to formation of the final covalent bond that establishes the mechanical bond [ 24 , 25 ]. These have included coordination bonds with a range of main group and transition row metal ions [ 26 , 27 , 28 ], anion-templation [ 29 , 30 , 31 , 32 ], π-stacking interactions [ 33 ], H-bonding [ 34 , 35 ] and radical-radical interactions [ 36 ], amongst others. However, the synthesis of more complex rotaxanes in which two or more macrocycles encircle a thread remains challenging [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ].…”

Section: Introductionmentioning

confidence: 99%

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

2017

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Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry. Whilst the first two iterations proceeded in good yield, the steric shielding that affords this selectivity also significantly reduces the efficacy of the active template (AT)-CuAAC reaction of the third alkyne towards the preparation of [4]rotaxanes, resulting in severely diminished yields.

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“…The strategy of exposing the system to a template to favor a desired supramolecular entity is an extremely important tool in supramolecular chemistry, with the impact on the self-assembly reaction outcome underscored in several notable paradigms. ,− The template can be a temporary or permanent helper, but its presence, however fleeting, is always necessary for the formation of the final product and essential for its integrity in some cases. , From a structural point of view, the size and geometry of the template are important in targeting the desired templated product, whereas in terms of electrostatics, the template can be cationic, neutral, or anionic. Despite the extensive use of cationic templates, the ability of anions to operate as templates (or guests) and direct the course of an assembly process through noncovalent interactions was not fully appreciated until recently. ,,, Anion binding typically involves noncovalent interactions, such as hydrogen-bonding, electrostatic, π–π stacking, and other van der Waals forces, but recently, another novel noncovalent attractive force involving anions and π-acidic (or electron-deficient) charge-neutral aromatic rings, namely, the anion−π interaction, − has become a topic of great interest. The pioneering theoretical studies − that established the favorable nature of anion−π interactions (∼20–70 kJ/mol), albeit at first glance counterintuitive, were complemented by an ever-increasing arsenal of experimental evidence for their presence in the solid state − and in solution, ,− as well as additional theoretical studies − that lend further insight into aspects of the interaction.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Architectures with π-Acidic 3,6-Bis(2-pyridyl)-1,2,4,5-tetrazine Cavities: Role of Anion−π Interactions in the Remarkable Stability of Fe(II) Metallacycles in Solution

2013

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The comprehensive investigation reported herein provides compelling evidence that anion-π interactions are the main driving force in the formation of self-assembled Fe(II)-templated metallacycles with bptz [3,6-bis(2-pyridyl)-1,2,4,5-tetrazine] in high yields. It was demonstrated by X-ray crystallography, (1)H NMR, solution and solid-state MAS (19)F NMR spectroscopies, CV and MS studies that the anions [X](-) = [BF(4)](-), [ClO(4)](-) and the anions [Y](-) = [SbF(6)](-), [AsF(6)](-), [PF(6)](-) template molecular squares [Fe(4)(bptz)(4)(CH(3)CN)(8)][X](8) and pentagons [Fe(5)(bptz)(5)(CH(3)CN)(10)][Y](10), respectively. The X-ray structures of [{Fe(4)(bptz)(4)(CH(3)CN)(8)}⊂BF(4)][BF(4)](7) and [{Fe(5)(bptz)(5)(CH(3)CN)(10)}⊂2SbF(6)][SbF(6)](8) revealed that the [BF(4)](-) and [SbF(6)](-) anions occupy the π-acidic cavities, establishing close directional F···C(tetrazine) contacts with the tetrazine rings that are by ~0.4 Å shorter than the sum of the F···C van der Waals radii (ΣR(vdW) F···C = 3.17 Å). The number and strength of F···C(tetrazine) contacts are maximized; the F···C(tetrazine) distances and anion positioning versus the polygon opposing tetrazine rings are in agreement with DFT calculations for C(2)N(4)R(2)···[X](-)···C(2)N(4)R(2) (R = F, CN; [X](-) = [BF(4)](-), [PF(6)](-)). In unprecedented solid-state (19)F MAS NMR studies, the templating anions, engaged in anion-π interactions in the solid state, exhibit downfield chemical shifts Δδ((19)F) ≈ 3.5-4.0 ppm versus peripheral anions. NMR, CV, and MS studies also establish that the Fe(II) metallacycles remain intact in solution. Additionally, interconversion studies between the Fe(II) metallacycles in solution, monitored by (1)H NMR spectroscopy, underscore the remarkable stability of the metallapentacycles [Fe(5)(bptz)(5)(CH(3)CN)(10)][PF(6)](10) ≪ [Fe(5)(bptz)(5)(CH(3)CN)(10)][SbF(6)](10) < [Fe(5)(bptz)(5)(CH(3)CN)(10)][AsF(6)](10) versus [Fe(4)(bptz)(4)(CH(3)CN)(8)][BF(4)](8), given the inherent angle strain in five-membered rings. Finally, the low anion activation energies of encapsulation (ΔG(‡) ≈ 50 kJ/mol), determined from variable-temperature (19)F NMR studies for [Fe(5)(bptz)(5)(CH(3)CN)(10)][PF(6)](10) and [Zn(4)(bptz)(4)(CH(3)CN)(8)][BF(4)](8), confirm anion encapsulation in the π-acidic cavities by anion-π contacts (~20-70 kJ/mol).

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Template Synthesis

Cited by 5 publications

References 97 publications

Cation- and Anion-Mediated Supramolecular Assembly of Bismuth and Antimony Tris(3-pyridyl) Complexes

Cation- and Anion-Mediated Supramolecular Assembly of Bismuth and Antimony Tris(3-pyridyl) Complexes

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

Supramolecular Architectures with π-Acidic 3,6-Bis(2-pyridyl)-1,2,4,5-tetrazine Cavities: Role of Anion−π Interactions in the Remarkable Stability of Fe(II) Metallacycles in Solution

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