Multiresponsive Luminescent Cationic Cyclometalated Gold(III) Amphiphiles and Their Supramolecular Assembly

Abstract

A new class of amphiphilic tridentate cyclometalated gold(III) complexes has been designed and synthesized as luminescent supramolecular building blocks. Positively charged trimethylammonium (−CH 2 NMe 3 + ) containing alkynyl ligands have been incorporated to introduce the electrostatic interactions. The X-ray crystal structures of two of the complexes have been determined, and the existence of π−π interactions between molecules has been observed. Steady-state and time-resolved absorption and emission studies have been carried out to investigate the nature of the excited states. The complexes are found to exhibit selfassembly properties with the assistance of π−π stacking and hydrophobic interactions and possibly weak Au•••Au interaction, resulting in notable emergence of low-energy absorption bands and luminescence changes. The presence of a large hydrophobic moiety is found to be crucial for the formation of aggregates, especially in polar media where hydrophobic interactions play an important role. The nature of the counterion has been shown to have a significant effect on the extent of self-assembly in different media. Upon aggregation, nanofibers are formed in polar media, while nanorods are observed in nonpolar media in one of the representative complexes. Interestingly, a small modification on the alkynyl ligand resulted in the formation of nanoribbons instead. Intriguing luminescence mechanochromic properties have also been observed. This orthogonal and rational molecular design strategy has been shown to be effective in the construction of gold(III)-based smart and multiresponsive materials.

Tuning energy landscapes and metal–metal interactions in supramolecular polymers regulated by coordination geometry

“… 15–17 In recent years, molecular design strategies 18,19 have been successfully exploited to drive and control molecular self-assembly processes. 20–22 The intriguing possibilities that arise from adding metal ions into the mix 23–26 have kickstarted the relatively young field of metal-based supramolecular polymers. 26 Due to the wide variety of available ligands and metal ions capable of forming supramolecular polymers, the structural diversity of such compounds is immense.…”

Loading Linear Arrays of CuII Inside Aromatic Amide Helices

“…Indeed metal-metal interactions often require shorter distances (less than % 2.8 for Cu II ), [17] as observed in various Pt and Aucomplexes. [18] Nevertheless, magnetic susceptibility measurements revealed an unanticipated ferromagnetic exchange between the paramagnetic Cu II . The data could be fitted to an isotropic Heisenberg spin Hamiltonian considering spin S = 1 = 2 Cu II centers (Figures S21, S22).…”

An Unexpected 4,5‐Diphenyl‐2,7‐naphthyridine Derivative with Aggregation‐Induced Emission and Mechanofluorochromic Properties Obtained from a 3,5‐Diphenyl‐4H‐pyran Derivative

“…[1] In the past decade, it has attracted increased interest due to its potential applications in information storages, fluorescent sensors, security inks, and anti-counterfeiting materials. [2][3][4][5][6][7][8][9][10] In particular, the color changes of MFC compounds caused by external pressure can be recovered by other stimulation modes, such as temperature or organic gas, which makes MFC compounds have a very important position in the field of solid-state fluorescence stimulus-responsive materials. Most of the MFC properties of these materials are due to the changes of the stacking modes of their molecules under the stimulation of external pressure.…”

“…Mechanofluorochromic (MFC) materials are a kind of intelligent fluorescent material which can change the color of solid‐state fluorescence under the external stimulation of pressure [1] . In the past decade, it has attracted increased interest due to its potential applications in information storages, fluorescent sensors, security inks, and anti‐counterfeiting materials [2–10] . In particular, the color changes of MFC compounds caused by external pressure can be recovered by other stimulation modes, such as temperature or organic gas, which makes MFC compounds have a very important position in the field of solid‐state fluorescence stimulus‐responsive materials.…”