27 results found
Lewis JEM, Tarzia A, White AJP, et al., Conformational control of Pd2L4 assemblies with unsymmetrical ligands, Chemical Science, ISSN: 2041-6520
With increasing interest in the potential utility of metallo-supramolecular architectures for applications as diverse as catalysis and drug delivery, the ability to develop more complex assemblies is keenly sought after. Despite this, symmetrical ligands have been utilised almost exclusively to simplify the self-assembly process as without a significant driving force a mixture of isomeric products will be obtained. Although a small number of unsymmetrical ligands have been shown to serendipitously form well-defined metallo-supramolecular assemblies, a more systematic study could provide generally applicable information to assist in the design of lower symmetry architectures. Pd2L4 cages are a popular class of metallo-supramolecular assembly; research seeking to introduce added complexity into their structure to further their functionality has resulted in a handful of examples of heteroleptic structures, whilst the use of unsymmetrical ligands remains underexplored. Herein we show that it is possible to design unsymmetrical ligands in which either steric or geometric constraints, or both, can be incorporated into ligand frameworks to ensure exclusive formation of single isomers of three-dimensional Pd2L4 metallo-supramolecular assemblies with high fidelity. In this manner it is possible to access Pd2L4 cage architectures of reduced symmetry, a concept that could allow for the controlled spatial segregation of different functionalities within these systems. The introduction of steric directing groups was also seen to have a profound effect on the cage structures, suggesting that simple ligand modifications could be used to engineer structural properties.
Denis M, Lewis J, Modicom F, et al., 2019, An auxiliary approach for the stereoselective synthesis of topologically Chiral catenanes, Chem, Vol: 5, Pages: 1512-1520, ISSN: 2451-9294
Catenanes, molecules in which two rings are threaded through one another like links in a chain, can form as two structures related as object and mirror image but otherwise identical if the individual rings lack bilateral symmetry. These structuresare described as “topologically chiral” as, unlike most chiral molecules,it is not possible to convert onemirror-image formto the other undertherules of mathematical topology. Although intriguing, and discussed as early as 1961, to date all methods to access molecules containing only this topological stereogenic element requiretheseparation ofthe mirror imageforms using chiral stationary phase high performance liquid chromatography (PCSP-HPLC)which has limited their investigation to date. Here we present a simple method that uses a readily available source of chiral information to allow the stereoselective synthesis of topologically chiral catenanes.
Lewis JEM, 2019, Self-templated synthesis of amide catenanes and formation of a catenane coordination polymer, Organic & Biomolecular Chemistry, Vol: 17, Pages: 2442-2447, ISSN: 1477-0520
A self-templation strategy was used to synthesise isophthalamide catenanes of various sizes in up to 51% yield without the need for metal ions as templates or mediators of covalent bond formation. Using this strategy a bis-monodentate catenane was prepared incorporating exohedral pyridine units. Upon complexation of this ligand with AgOTf a one-dimensional coordination polymer was obtained in the solid state in which both macrocycles of the catenane are involved in binding to the metal nodes, resulting in a rare example of a coordination assembly in which mechanical bonds are incorporated into the structure backbone.
Cirulli M, Kaur A, Lewis JEM, et al., 2019, Rotaxane-based transition metal complexes: Effect of the mechanical bond on structure and electronic properties, Journal of the American Chemical Society, Vol: 141, Pages: 879-889, ISSN: 0002-7863
Early work by Sauvage revealed that mechanical bonding alters the stability and redox properties of their original catenane metal complexes. However, despite the importance of controlling metal ion properties for a range of applications, these effects have received relatively little attention since. Here we present a series of tri-, tetra-, and pentadentate rotaxane-based ligands and a detailed study of their metal binding behavior and, where possible, compare their redox and electronic properties with their noninterlocked counterparts. The rotaxane ligands form complexes with most of the metal ions investigated, and X-ray diffraction revealed that in some cases the mechanical bond enforces unusual coordination numbers and distorted arrangements as a result of the exclusion of exogenous ligands driven by the sterically crowded binding sites. In contrast, only the noninterlocked equivalent of the pentadentate rotaxane CuII complex could be formed selectively, and this exhibited compromised redox stability compared to its interlocked counterpart. Frozen-solution EPR data demonstrate the formation of an interesting biomimetic state for the tetradentate CuII rotaxane, as well as the formation of stable NiI species and the unusual coexistence of high- and low-spin CoII in the pentadentate framework. Our results demonstrate that readily available mechanically chelating rotaxanes give rise to complexes the noninterlocked equivalent of which are inaccessible, and that the mechanical bond augments the redox behavior of the bound metal ion in a manner analogous to the carefully tuned amino acid framework in metalloproteins.
Lewis JEM, Modicom F, Goldup SM, 2018, Efficient multicomponent active template synthesis of catenanes, Journal of the American Chemical Society, Vol: 140, Pages: 4787-4791, ISSN: 1520-5126
We describe a simple and high yielding active template synthesis of catenanes. In addition to mechanical bond formation using a single premacrocycle bearing an azide and alkyne moiety, our method is also suitable for the co-macrocyclization of readily available bis-alkyne and bis-azide comonomers and even short alkyne/azide components which oligomerize prior to mechanical bond formation.
Ngo TH, Labuta J, Lim GN, et al., 2017, Porphyrinoid rotaxanes: building a mechanical picket fence, CHEMICAL SCIENCE, Vol: 8, Pages: 6679-6685, ISSN: 2041-6520
Preston D, White KF, Lewis JEM, et al., 2017, Solid-State Gas Adsorption Studies with Discrete Palladium(II) [Pd-2(L)(4)](4+) Cages, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 23, Pages: 10559-10567, ISSN: 0947-6539
Lewis JEM, Beer PD, Loeb SJ, et al., 2017, Metal ions in the synthesis of interlocked molecules and materials, CHEMICAL SOCIETY REVIEWS, Vol: 46, Pages: 2577-2591, ISSN: 0306-0012
Preston D, Lewis JEM, Crowley JD, 2017, Multicavity [PdnL4](2n+) cages with controlled segregated binding of different guests, Journal of the American Chemical Society, Vol: 139, Pages: 2379-2386, ISSN: 1520-5126
Multicavity [Pdn(L)4]2n+ metallosupramolecular cages based on long backboned ligands are an attractive approach to increasing molecular size without loss of the binding specificity conferred by small cavity [Pd2(L)4]4+ assemblies. We herein report the synthesis of two double cavity polypyridyl [Pd3(L)4]6+ cages that bind cisplatin [Pt(NH3)2Cl2] within their internal cavities and interact with triflate (TfO–) on their exohedral faces. We also report the first example of a triple cavity [Pd4(L)4]8+ cage. This cage differs in that the central cavity is phenyl-linked rather than having the pyridyl core as in the peripheral cavities. The difference in cavity character results in selective guest binding of cisplatin in the peripheral cavities, with triflate binding within the central cavity and on the exohedral faces of the peripheral palladium(II) ions. All the cavities could be simultaneously filled by introducing both cisplatin and triflate concurrently, providing the first example of a discrete metallosupramolecular architecture with segregated guest binding in different designed internal cavities. The ligands and cages were characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and, in one case, X-ray crystallography.
Lewis JEM, Galli M, Goldup SM, 2017, Properties and emerging applications of mechanically interlocked ligands, CHEMICAL COMMUNICATIONS, Vol: 53, Pages: 298-312, ISSN: 1359-7345
Lewis JEM, Winn J, Goldup SM, 2017, Stepwise, Protecting Group Free Synthesis of Rotaxanes, MOLECULES, Vol: 22, ISSN: 1420-3049
Lewis JEM, Winn J, Cera L, et al., 2016, Iterative synthesis of oligo[n]rotaxanes in excellent yield, Journal of the American Chemical Society, Vol: 138, Pages: 16329-16336, ISSN: 1520-5126
We present an operationally simple iterative coupling strategy for the synthesis of oligomeric homo- and hetero[n]rotaxanes with precise control over the position of each macrocycle. The exceptional yield of the AT-CuAAC reaction, combined with optimized conditions that allow the rapid synthesis of the target oligomers, opens the door to the study of precision-engineered oligomeric interlocked molecules.
Preston D, McNeill SM, Lewis JEM, et al., 2016, Enhanced kinetic stability of [Pd2L4](4+) cages through ligand substitution, Dalton Transactions, Vol: 45, Pages: 8050-8060, ISSN: 1477-9234
There is considerable interest in exploiting metallosupramolecular cages as drug delivery vectors. Recently, we developed a [Pd2L4]4+ cage capable of binding two molecules of cisplatin. Unfortunately, this first generation cage was rapidly decomposed by common biologically relevant nucleophiles. In an effort to improve the kinetic stability of these cage architectures here we report the synthesis of two amino substituted tripyridyl 2,6-bis(pyridin-3-ylethynyl)pyridine (tripy) ligands (with amino groups either in the 2-(2A-tripy) or 3-(3A-tripy) positions of the terminal pyridines) and their respective [Pd2(Ltripy)4]4+ cages. These systems have been characterised by 1H, 13C and DOSY NMR spectroscopies, high resolution electrospray mass spectrometry, elemental analysis and, in one case, by X-ray crystallography. It was established, using model palladium(II) N-heterocyclic carbene (NHC) probe complexes, that the amino substituted compounds were stronger donor ligands than the parent system (2A-tripy > 3A-tripy > tripy). Competition experiments with a range of nucleophiles showed that these substitutions lead to more kinetically robust cage architectures, with [Pd2(2A-tripy)4]4+ proving the most stable. Biological testing on the three ligands and cages against A549 and MDA-MB-231 cell lines showed that only [Pd2(2A-tripy)4]4+ exhibited any appreciable cytotoxicity, with a modest IC50 of 36.4 ± 1.9 μM against the MDA-MB-231 cell line. Unfortunately, the increase in kinetic stability of the [Pd2(Ltripy)4]4+ cages was accompanied by loss of cisplatin-binding ability.
Elliott ABS, Lewis JEM, van der Salm H, et al., 2016, Luminescent Cages: Pendant Emissive Units on [Pd2L4](4+) "Click" Cages, INORGANIC CHEMISTRY, Vol: 55, Pages: 3440-3447, ISSN: 0020-1669
Lewis JEM, Bordoli RJ, Denis M, et al., 2016, High yielding synthesis of 2,2 '-bipyridine macrocycles, versatile intermediates in the synthesis of rotaxanes, Chemical Science, Vol: 7, Pages: 3154-3161, ISSN: 2041-6520
We present an operationally simple approach to 2,2′-bipyridine macrocycles. Our method uses simple starting materials to produce these previously hard to access rotaxane precursors in remarkable yields (typically >65%) across a range of scales (0.1–5 mmol). All of the macrocycles reported are efficiently converted (>90%) to rotaxanes under AT-CuAAC conditions. With the requisite macrocycles finally available in sufficient quantities, we further demonstrate their long term utility through the first gram-scale synthesis of an AT-CuAAC rotaxane and extend this powerful methodology to produce novel Sauvage-type molecular shuttles.
Galli M, Lewis JEM, Goldup SM, 2015, A Stimuli-Responsive Rotaxane-Gold Catalyst: Regulation of Activity and Diastereoselectivity, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 54, Pages: 13545-13549, ISSN: 1433-7851
Noor A, Maloney DL, Lewis JEM, et al., 2015, Acid-Base Driven Ligand Exchange with Palladium(II) "Click" Complexes, ASIAN JOURNAL OF ORGANIC CHEMISTRY, Vol: 4, Pages: 208-211, ISSN: 2193-5807
McNeill SM, Preston D, Lewis JEM, et al., 2015, Biologically active [Pd2L4](4+) quadruply-stranded helicates: stability and cytotoxicity, DALTON TRANSACTIONS, Vol: 44, Pages: 11129-11136, ISSN: 1477-9226
Noor A, Huff GS, Kumar SV, et al., 2014, [Re(CO)(3)](+) Complexes of exo-Functionalized Tridentate "Click" Macrocycles: Synthesis, Stability, Photophysical Properties, Bioconjugation, and Antibacterial Activity, ORGANOMETALLICS, Vol: 33, Pages: 7031-7043, ISSN: 0276-7333
Lewis JEM, Elliott ABS, McAdam CJ, et al., 2014, 'Click' to functionalise: synthesis, characterisation and enhancement of the physical properties of a series of exo- and endo-functionalised Pd2L4 nanocages, CHEMICAL SCIENCE, Vol: 5, Pages: 1833-1843, ISSN: 2041-6520
Lewis JEM, Crowley JD, 2014, Exo- and endo-hedral interactions of counteranions with tetracationic Pd2L4 metallosupramolecular architectures, 8th International Symposium of Macrocyclic and Supramolecular Chemistry (ISMSC), Publisher: TAYLOR & FRANCIS LTD, Pages: 173-181, ISSN: 1061-0278
Vellas SK, Lewis JEM, Shankar M, et al., 2013, [Fe2L3](4+) Cylinders Derived from Bis(bidentate) 2-Pyridyl-1,2,3-triazole "Click" Ligands: Synthesis, Structures and Exploration of Biological Activity, MOLECULES, Vol: 18, Pages: 6383-6407, ISSN: 1420-3049
Lewis JEM, McAdam CJ, Gardiner MG, et al., 2013, A facile "click" approach to functionalised metallosupramolecular architectures, CHEMICAL COMMUNICATIONS, Vol: 49, Pages: 3398-3400, ISSN: 1359-7345
Lewis JEM, Crowley JD, 2013, Copper(II) Complexes of a Tripyridyl Ligand: Anion-Dependent Metallosupramolecular Structures, AUSTRALIAN JOURNAL OF CHEMISTRY, Vol: 66, Pages: 1447-1454, ISSN: 0004-9425
Lewis JEM, Gavey EL, Cameron SA, et al., 2012, Stimuli-responsive Pd2L4 metallosupramolecular cages: towards targeted cisplatin drug delivery, CHEMICAL SCIENCE, Vol: 3, Pages: 778-784, ISSN: 2041-6520
Anderson CB, Elliott ABS, Lewis JEM, et al., 2012, fac-Re(CO)(3) complexes of 2,6-bis(4-substituted-1,2,3-triazol-1-ylmethyl)pyridine "click" ligands: synthesis, characterisation and photophysical properties, DALTON TRANSACTIONS, Vol: 41, Pages: 14625-14632, ISSN: 1477-9226
Noor A, Lewis JEM, Cameron SA, et al., 2012, A multi-component CuAAC 'click' approach to an exo functionalised pyridyl-1,2,3-triazole macrocycle: synthesis, characterisation, Cu(I) and Ag(I) complexes, 7th International Symposium of Macrocyclic and Supramolecular Chemistry (ISMSC), Publisher: TAYLOR & FRANCIS LTD, Pages: 492-498, ISSN: 1061-0278
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