Recent advances in heteroleptic multiple-stranded metallosupramolecules

Tran, Ngoc Minh; Yoo, Hyojong

doi:10.1039/d0dt02243h

Cited by 10 publications

(9 citation statements)

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“…Likewise, Schmittel and co-workers have avoided the formation of homoleptic phenanthroline complexes by grafting bulky aryl groups at the 2,9-positions. , The resulting spatial hindrance avoids the complexation of two bulky ligands while still allowing heteroleptic complexes to form in combination with less sterically demanding ligands like terpyridine or unsubstituted phenanthroline. Heteroleptic complexes have also been widely used as static units for the construction of highly ordered complex supramolecular arrays − and as dynamic groups for the induction of structural rearrangements in molecular machines. − However, their application in the field of polymer science has been limited to recent reports on the formation of A–B-type block copolymers. − This is unfortunate as the incorporation of dynamic heteroleptic complexes not only defines new paradigms for designing smart polymeric materials but can also provide a new scale for the recognition of self-sorting mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Direct Evidence of Heteroleptic Complexation in the Macroscopic Dynamics of Metallo-supramolecular Polymer Networks

Ahmadi

Seiffert

2021

Macromolecules

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Heteroleptic complexes are widely employed in small-molecule supramolecular arrays for the construction of complex architectures or for inducing nanoscopic rearrangements upon application of external stimuli that change the coordination-geometry preference. Despite this potential, they are rarely employed in the development of metallo-supramolecular polymer networks; this is unfortunate as that strategy might actually provide a tool to build highly homogeneous model-type networks that could form a basis for both a myriad of elementary investigations on transient networks and for their use in rational soft-functional materials design. To close that gap, we mix aqueous solutions of terpyridine- and phenanthroline-functionalized tetra-arm poly(ethylene glycol) (tetraPEG) precursors right at the overlap concentration and form physical hydrogels by introducing various types of divalent transition metal ions. The formation of heteroleptic complexes is comprehended by the persistence of the network percolation at intermediate network compositions, as revealed by rheological measurements. Specifically, shear stress curves and the resulting relaxation time spectra demonstrate the emergence of a third relaxation mode, on top of those associated with homoleptic complexes, which is indicative of heteroleptic complexation. Spectroscopic analyses and DFT calculations suggest the possible formation of heteroleptic complexes with all studied metal ions, whereby their fraction and lifetime are traceable using rheological measurements in the case of networks formed by Co2+ ions. Moreover, employing over-stoichiometric Co2+-to-ligand ratios eventually results in the selective formation of heteroleptic complexes. These results not only suggest new paradigms for devising smart soft materials, but they also propose new dimensions for characterizing heteroleptic complexes.

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Section: Introductionmentioning

confidence: 99%

Direct Evidence of Heteroleptic Complexation in the Macroscopic Dynamics of Metallo-supramolecular Polymer Networks

Ahmadi

Seiffert

2021

Macromolecules

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“…Systems have been studied for their anti-cancer and anti-microbial activity and their potential as drug delivery agents. Helicates ( Piguet et al, 1997 ; Albrecht, 2001 ; Hannon and Childs, 2004 ; Howson and Scott, 2011 ; Boiocchi and Fabbrizzi, 2014 ; Paneerselvam et al, 2018 ; Albrecht et al, 2019 ; Albrecht, 2020 ; Tran and Yoo, 2020 ) are one of the earlier known and well-studied sub-classes of MSAs. Lehn and co-workers reported the first helicates; a double-stranded dinuclear and larger trinuclear system were generated from poly(2,2′-bipyridine) ligands and Cu(I) ions ( Lehn et al, 1987 ) Subsequently, single, triple, and quadruple stranded helicates have all been synthesized and these systems are chiral featuring P (plus, right-handed) and M (minus, left-handed) helices ( Figure 1 ).…”

Section: Introductionmentioning

confidence: 99%

Cavity-Containing [Fe2L3]4+ Helicates: An Examination of Host-Guest Chemistry and Cytotoxicity

et al. 2021

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Two new di(2,2′-bipyridine) ligands, 2,6-bis([2,2′-bipyridin]-5-ylethynyl)pyridine (L1) and bis(4-([2,2′-bipyridin]-5-ylethynyl)phenyl)methane (L2) were synthesized and used to generate two metallosupramolecular [Fe2(L)3](BF4)4 cylinders. The ligands and cylinders were characterized using elemental analysis, electrospray ionization mass spectrometry, UV-vis, 1H-, 13C and DOSY nuclear magnetic resonance (NMR) spectroscopies. The molecular structures of the [Fe2(L)3](BF4)4 cylinders were confirmed using X-ray crystallography. Both the [Fe2(L1)3](BF4)4 and [Fe2(L2)3](BF4)4 complexes crystallized as racemic (rac) mixtures of the ΔΔ (P) and ΛΛ (M) helicates. However, 1H NMR spectra showed that in solution the larger [Fe2(L2)3](BF4)4 was a mixture of the rac-ΔΔ/ΛΛ and meso-ΔΛ isomers. The host-guest chemistry of the helicates, which both feature a central cavity, was examined with several small drug molecules. However, none of the potential guests were found to bind within the helicates. In vitro cytotoxicity assays demonstrated that both helicates were active against four cancer cell lines. The smaller [Fe2(L1)3](BF4)4 system displayed low μM activity against the HCT116 (IC50 = 7.1 ± 0.5 μM) and NCI-H460 (IC50 = 4.9 ± 0.4 μM) cancer cells. While the antiproliferative effects against all the cell lines examined were less than the well-known anticancer drug cisplatin, their modes of action would be expected to be very different.

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“…The maintenance of heteroleptic structures when changing metal ions, as well as extending the ligand length and flexibility, also suggests that the symmetry and helicity of triple-stranded metallosupramolecules are energetically favorable. 37 On the basis of the results about metallosupramolecules we have obtained so far, we expect that the extension in bridging ligand length, together with the variation of the substituent/ functional groups in the backbone, could create metallosupramolecules with unprecedented assembly modes. The lengthening of the bridging ligand is also expected to generate voids with large size, which is meaningful in host−guest interaction.…”

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, the higher length and flexibility of CDBA initiate a higher potential for the generation of unprecedented higher-order assembly modes with high complexity, flexibility, and diversity. The maintenance of heteroleptic structures when changing metal ions, as well as extending the ligand length and flexibility, also suggests that the symmetry and helicity of triple-stranded metallosupramolecules are energetically favorable …”

Section: Introductionmentioning

confidence: 99%

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Heteroleptic Triple-Stranded Metallosupramolecules with Hydrophobic Inner Voids

et al. 2022

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The systematic combination of well-defined coordination spheres and multiple types of ligands (heteroleptic) can lead to the generation of hierarchical metallosupramolecules with a high level of complexity and functionality. In particular, a specific multilevel coordination-driven assembly through the initiate generation of multinuclear clusters can form unique heteroleptic multiple-stranded supramolecular complexes. Herein, we report novel triple-stranded nickel-based supramolecules constructed from two different ditopic ligands ([1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylate (TP) and 2,6-pyridinedicarboxylate (PDA)) and a nickel precursor. The solid-state structures of the as-synthesized supramolecules revealed that three PDA ligands are employed to fabricate a tetranuclear ({Ni 4 }) cluster, and two {Ni 4 } clusters are assembled to form the final triple-stranded metallosupramolecules by three TP ligands. The bridging TP ligands also provide large inner voids with highly hydrophobic environments. Structural investigation of the generated complexes provided a deeper understanding of the aspects driving the formation of heteroleptic supramolecules, which is crucial for the design of multiple-strands with desired morphologies and functionalities.

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Recent advances in heteroleptic multiple-stranded metallosupramolecules

Abstract: Well-ordered combinations of defined coordination spheres and multiple types of ligands (heteroleptic) in a given structure can expand the structural complexity and functional diversity of the resulting metallosupramolecules. Such supramolecular...

Cited by 10 publications

References 114 publications

Direct Evidence of Heteroleptic Complexation in the Macroscopic Dynamics of Metallo-supramolecular Polymer Networks

Direct Evidence of Heteroleptic Complexation in the Macroscopic Dynamics of Metallo-supramolecular Polymer Networks

Cavity-Containing [Fe2L3]4+ Helicates: An Examination of Host-Guest Chemistry and Cytotoxicity

Heteroleptic Triple-Stranded Metallosupramolecules with Hydrophobic Inner Voids

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