Phosphorescent Host–Guest Complexes on the Basis of Polyhedral Oligomeric Silsesquioxane-Functionalized Metallotweezers

Abstract

Phosphorescent host–guest systems have attracted considerable attention because of their intriguing properties and diverse applications. In this study, a polyhedral oligomeric silsesquioxane-functionalized gold­(III) tweezer receptor has been designed and synthesized. It is capable of sandwiching platinum­(II) terpyridine compounds into its cavity with a high noncovalent binding affinity (association constants: ∼105 M–1 in chloroform). The resulting heterometallic host–guest complexes exhibit enhanced phosphorescent emission compared with those of the individual species in chloroform, thanks to the prevention of vibration and rotation upon noncovalent complexation. They can further assemble into nanospheres in chloroform/diethyl ether (1:9, v/v) owing to phase segregation between the metallotweezer/guest motif and the peripheral polyhedral oligomeric silsesquioxane unit. When terpyridine platinum­(II) chloride serves as the complementary guest, the resulting noncovalent system displays an intraligand emission at the individual host–guest complexed state yet excimeric emission at the supramolecular assembled state, yielding the phosphorescent solvatochromic behaviors. Overall, the polyhedral oligomeric silsesquioxane-functionalized metallotweezer combines guest encapsulation and supramolecular assembly capabilities, which provides new avenues for color-tunable phosphorescent materials.

End Functionalization of Polynorbornene with Platinum–Acetylide Complexes Utilizing a Cross-Metathesis Reaction

“…There was no significant difference of emission wavelengths between the three samples, as shown in Figure , while the fluorescence and phosphorescence lifetimes became long by connecting the Pt-complex to the polymer at the chain end. It is likely that lowering the molecular motion of the Pt-complex moiety elongates the photoluminescence lifetimes, in a manner similar to the report on phosphorescent host–guest complexes on the basis of polyhedral oligomeric silsesquioxane-functionalized metallotweezers . This finding suggests a strategy for developing photoluminescent materials with long lifetimes.…”

“…It is likely that lowering the molecular motion of the Pt-complex moiety elongates the photoluminescence lifetimes, in a manner similar to the report on phosphorescent host−guest complexes on the basis of polyhedral oligomeric silsesquioxane-functionalized metallotweezers. 58 This finding suggests a strategy for developing photoluminescent materials with long lifetimes. It is important to examine the photoluminescent properties in the solid state for practical usage.…”

Dual supramolecular chirogenesis based on platinum(ii) metallotweezers

“…S17, ESI†). With reference to previous reports, 9 these signals were assigned to the admixture of metal-to-ligand and ligand-to-ligand charge-transfer (MLCT/LLCT) transitions of the alkynyl Pt( ii )(N^N^N) moiety. Upon switching the solvent from chloroform to acetonitrile, the MLCT/LLCT emission signal declined for the intensity (Fig.…”

“…When the cyclometalated Pt( ii ) pincers are kept at the distance of 7 Å by a rigid spacer, the metallotweezers are capable of encapsulating a guest molecule into their cavity. 9 The non-covalent host–guest complexation structure is stabilized by π–π stacking interactions between the Pt( ii ) pincers and the complementary guest (interplanar distance: ∼3.5 Å). It can be endowed with fruitful photo-physical properties due to the spin–orbit coupling effect, leading to metal-to-ligand charge transfer (MLCT), ligand-to-ligand charge transfer (LLCT), and metal–metal-to-ligand charge transfer (MMLCT) transitions in the low-energy absorption region.…”

Precise Regulation the Multiemission Based on Soft Double Salt for Information Encryption

“…As important supramolecular assembly building blocks, the platinum­(II) complexes adopt unique square-planar geometry and could represent attractive candidates. − The existence of noncovalent Pt···Pt interactions could introduce intriguing luminescence properties along with fascinating spectral features. ,− The exploration of platinum­(II) complexes with abundant types of π-conjugated ligands has been reported. − As two main kinds of tridentate pincer ligands, the cyclometalated platinum­(II) 1,3-di­(2-pyridyl)­benzene (N^C^N) complexes and 6-phenyl-2,2′-bipyridine (C^N^N) complexes have been studied and found to show strong phosphorescence properties due to the higher energy of the d–d excited state. , Williams and co-workers first reported a series of N^C^N ligands of 1,3-di­(2-pyridyl)­benzene and its derivatives that display strong green emission originating from the 3 IL [π → π* (N^C^N)] excited state . We recently reported two series of dinuclear complexes: (i) we fabricated an artificial single-molecular hinge with motions associated with visual phosphorescence changes of green to red; (ii) upon changing the alkoxyl chain length, multidimensional aggregation structures can be obtained, in association with both apparent color and phosphorescence changes .…”