Single-stranded nucleic acid-induced helical self-assembly of alkynylplatinum(II) terpyridyl complexes

Abstract

Single-stranded nucleic acids, which carry multiple negative charges in an aqueous medium at near neutral pH, are found to induce the aggregation and self-assembly of the positively charged alkynylplatinum(II) terpyridyl complexes via electrostatic binding of the platinum complexes to the single-stranded nucleic acids, as revealed by the appearance of new UV-vis absorption and emission bands upon addition of single-stranded nucleic acids to a buffer solution of the complex. Changes in the intensity and pattern of circular dichroism (CD) spectroscopy are also observed, many of which are consistent with the assembly of the platinum complexes into helical structures, via metal⅐⅐⅐metal and ⅐⅐⅐ stacking interactions. The induced spectroscopic property changes are found to depend on the structural properties of the nucleic acids.helicity ͉ noncovalent interactions ͉ platinum complex N ucleic acids are, in a sense, the most fundamental and important class of biomolecules in a living cell. Detection of nucleic acids, analysis of their sequence, structure, and the corresponding properties, as well as their self-replication, interactions with regulation factors, and the details of transcription and translation are among the major foci of numerous biochemical and biophysical research works (1, 2). Single-stranded nucleic acid sensing and characterization are therefore of great importance, which not only can help us to understand how the cell functions and to assist biological research, but also facilitate the development of new tools for disease diagnosis and treatment and new drug developments.It has been known for many years that many of the square planar metal complexes arrange themselves into highly ordered extended linear chain or oligomeric structures in the solid state. Depending on the extent of the metal⅐⅐⅐metal and the ligand ⅐⅐⅐ stacking interactions, different colors could be observed (3, 4). Square planar platinum(II) complexes belong to a particularly interesting class of this type of complexes, as a result of their rich spectroscopic and luminescence properties revealed during the past few decades (3-16).Recently, we have synthesized a number of platinum(II) polypyridyl alkynyl complexes that show interesting spectroscopic and luminescence properties (17-21). One particularly interesting observation is that solvents of different polarity and also polyacrylate could induce the aggregation of the positively charged platinum complexes in organic solvent mixtures (19, 21). As a result, remarkable spectroscopic property changes were observed. Because single-stranded nucleic acids carry multiple negatively charged phosphate functional groups, they are polyanions. It is therefore reasonable to envisage that single-stranded nucleic acids may have the possibility to induce the self-assembly of the square planar platinum(II) complexes in an aqueous environment. Here, we describe the synthesis and characterization of a water-soluble platinum(II) terpyridyl alkynyl complex, [Pt(tpy)C'CC'CCH 2 OH]OTf (1) (Fig. 1), and it...

Luminescence color switching of supramolecular assemblies of discrete molecular decanuclear gold(I) sulfido complexes

“…As demonstrated by our previous studies on the aggregation behavior of square-planar platinum(II) complexes (77)(78)(79)(80) where an enhancement of the solubility of the metal complexes via introduction of solubilizing groups on the ligands and the fine control between solvophobicity and solvophilicity of the complexes would have a crucial influence on the factors governing supramolecular assembly and the formation of aggregates (80), introduction of long alkyl chains as solubilizing groups in the gold(I) sulfido clusters may serve as an effective way to enhance the solubility of the gold(I) clusters for the construction of supramolecular assemblies of novel luminescent nanoaggegrates.…”

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.…”

“…Apart from the rich photophysical and luminescence properties, as well as interesting solid-state polymorphism, such complexes exhibit notable color changes and luminescence enhancements as a result of Pt···Pt and π−π stacking interactions that occur from solvent composition change (21), polyelectrolyte addition (22,23), and gel formation (24). 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).…”