Single-Turn Helix–Coil Strands Stabilized by Metal···Metal and π–π Interactions of the Alkynylplatinum(II) Terpyridyl Moieties in meta-Phenylene Ethynylene Foldamers

Abstract

Dinuclear alkynylplatinum(II) terpyridyl complexes with oligomeric bridge consisting of five repeating meta-phenylene ethynylene (mPE) units have been found to exhibit a strong tendency to fold back onto themselves to form short helical strands through the stabilization of Pt···Pt and π-π interactions. The steric bulk of the terpyridine ligands and the length of the oligomeric bridge have been found to affect the extent of the intramolecular Pt···Pt interaction that governs the stabilization of the short helical strand in solution. Their folding properties via Pt···Pt and π-π stacking interactions have been studied by (1)H NMR, 2D ROESY NMR, electronic absorption, and emission spectroscopies.

Sulfoxide‐Induced Homochiral Folding of ortho‐Phenylene Ethynylenes (o‐OPEs) by Silver(I) Templating: Structure and Chiroptical Properties

“…In particular,a ll-conjugateda ryl ethynyl oligomers have been extensivelyused as hosts of different species. [13] For instance, meta- [14] and ortho-phenylene ethynylenes (o-OPEs) [15] are able to reversibly fold into helical arrangements, [16][17][18] even in ac hiral way if chiral side chains [19] or chiral subunits exist in the backbone, [20] or in the presence of chiral guests. [21] We recently showedt hat folded o-OPE-based nanopores could be filled with silver(I)c ations through carbophilic interactions with alkynes, [22] to give an ew class of metallofoldamers (Figure 1, acyclica chiral organic emitters).…”

Self-assembly of alkynylplatinum(II) terpyridine amphiphiles into nanostructures via steric control and metal–metal interactions

“…Earlier work by our group showed the first example, to our knowledge, of an alkynylplatinum(II) terpyridine system [Pt(tpy)(C ≡ CR)] + that incorporates σ-donating and solubilizing alkynyl ligands together with the formation of Pt···Pt interactions to exhibit notable color changes and luminescence enhancements on solvent composition change (25) and polyelectrolyte addition (26). This approach has provided access to the alkynylplatinum(II) terpyridine and other related cyclometalated platinum(II) complexes, with functionalities that can self-assemble into metallogels (27)(28)(29)(30)(31), liquid crystals (32,33), and other different molecular architectures, such as hairpin conformation (34), helices (35)(36)(37)(38), nanostructures (39)(40)(41)(42)(43)(44)(45), and molecular tweezers (46,47), as well as having a wide range of applications in molecular recognition (48)(49)(50)(51)(52), biomolecular labeling (48)(49)(50)(51)(52), and materials science (53,54). Recently, metalcontaining amphiphiles have also emerged as a building block for supramolecular architectures (42)(43)(44)(55)(56)(57)…”

Dynamic scaffold of chiral binaphthol derivatives with the alkynylplatinum(II) terpyridine moiety

“…S2). With reference to our previous works (21)(22)(23)(24)(25)(26)(27), the appearance of the absorption tail at longer wavelengths is ascribed to the formation of metal···metal interactions, and the absorption tail is tentatively assigned as the metal-metalto-ligand charge transfer (MMLCT) transition. Because the absorption tail at 510 nm in CH 3 CN is found to obey Beer's law within the concentration range of 10 −6 -10 −4 M, it establishes the MMLCT transition as being one that is of an intramolecular association in nature.…”

“…Such studies have benefited from the early works on the understanding of the influence of the metal···metal interaction on the spectroscopic properties of the d 8 platinum(II) system (1−36, 46−54) and a recent study on the energy landscape of the ligandbridged dinuclear iridium compound, which demonstrates the versatility of metal···metal interactions in governing the conformational change of the geometry (55). Apart from using metal···metal and π−π stacking interactions in stabilizing supramolecular nanostructures (28), hairpin conformation (25), and organogel formation (24), our group recently demonstrated the utilization of Pt···Pt and π−π interactions in controlling the helix-coil transition in meta-phenylene ethynylene (mPE) oligomers and in stabilizing reversibly the construction of a single-turn helix (26). The use of metallophilic interactions as the driving force has opened up a new strategy for the construction of helical strands of metallo-foldamers that are of immense interest in supramolecular architectures.…”