Recent Progress on Supramolecular Luminescent Assemblies Based on Aurophilic Interactions in Solution

Abstract

The development of supramolecular systems showing aurophilic interactions in solution is gaining much attention in the last years. This is due to the intriguing photophysical properties of gold(I) complexes, which usually confer to these supramolecular assemblies interesting luminescent properties, as well as the possibility of morphological modulation, through fine tuning of inter- and intramolecular aurophilic interactions, in synergy with the formation of other supramolecular contacts. In this work, an overview of the advances made in this area since 2015 is presented. A large variety of systems showing different spectroscopical and structural topologies has been reported. Moreover, these supramolecular assemblies have proven to be useful in a wide range of applications.

Self-Assembly and Mechanochromism Behavior of Gold(I) Supramolecular Cluster

“…Moreover, the Gibbs free energy of the intermolecular dimerization in acetonitrile solution was also calculated. The Δ G of cluster 1 2+ ·2BF 4 – reached −34.1 kJ/mol, which is very consistent with the self-aggregation trends observed in concentration-dependent luminescence. − Furthermore, additional bands were not observed beyond 380 nm when the attainable concentration reached 5 × 10 –4 M, suggesting that it was impossible to form a trimer or a higher oligomer under the conditions studied. − ,, Based on the bonding characteristics of aurophilicity interactions, the molecular conformation of the aggregates observed in the gold-based cluster may be staggered (crossed) or eclipsed (parallel) or in the opposite directions to individual cluster or mononuclear complex units. − We proposed that two Au 4 planar motifs were able to aggregate into polymeric assembles in head-to-head or face-to-face stacking mode by integrating strong intermolecular aurophilicity and π–π stacking interactions in solution even at room temperature.…”

“…. − Organometallic complexes are excellent luminescent materials capable of effectively regulating the molecular configuration under external stimuli due to their intermolecular noncovalent interactions such as halogen bonds, hydrogen bonds, C–H···π interactions, π–π superposition, etc. − Among these metal-based coordination compounds, gold­(I) complexes feature not only intermolecular noncovalent interactions but also attractive aurophilic interactions, which greatly enrich their structures and functions. − Moreover, intramolecular and intermolecular aurophilic Au I ···Au I interactions are potentially jointly induced by relativistic effects and dispersion forces, − which are beneficial for the preparation of high-efficiency mechanochromic materials. − Accordingly, the rational introduction of gold­(I)-containing structural units into an ideal molecular skeleton to obtain a mechanochromic luminescent material remains a challenge to date. − …”

“…The aurophilicity interactions found in gold­(I) complexes with a binding energy of 7–12 kcal/mol have been utilized to construct a variety of sophisticated gold­(I)-based supramolecular assemblies. − The binding strength of aurophilicity interactions is comparable to that of hydrogen bonds, enabling the assembly of polynuclear clusters, metallocycles and cages, and catenanes. − Aurophilic-bonded gold­(I) clusters have received particular attention because of not only their structural sophistication and diversity − but also their applications in catalysis, photoluminescence, bioimaging, and chiral sensing, giving rise to their unique physicochemical properties. − Mixing ligands with various gold­(I) units at once form a conventional method for preparing homo- and heterometallic gold­(I) clusters. − Che et al reported an early example of an unexpected hexagold­(I) cluster [Au­( tatt 3 – )­(AuPPhMe 2 ) 2 ] 2 complex from initial trigold unit [ tatt 3 – (AuPPhMe 2 ) 3 ] ( tatt 3 – = trithiocyanuric anion, C 3 N 3 S 3 3– ) by treating mononuclear monophosphine-protected gold­(I) unit AuCl­(PPhMe 2 ) with ditopic trithiocyanuric ligand in methanol solution . Similar cluster growth and supramolecular aggregation behavior have also been observed in the preparation process of unpredicted supramolecular cluster Au 12 and 2D supramolecular polymers, − respectively.…”

Inorganic Self‐assembly: Going Bio

“…[38,[83][84][85] For instance, when compared to purely organic building blocks the possibilities of self-assembly of metal-organic entities are enriched by the extended toolbox of available non-covalent interactions, [86] for example, coordination bonds or metallophilic contacts, [87,88] which further generate aggregates with attractive properties. [59,89] The design of building blocks that self-assemble under these principles could render the assembly process selective in complex biological matrices. Moreover, the possibility of modulating the strength of these interactions [90,91] should be applied to generate stimuli-responsive and adaptative materials.…”

Spontaneous in situ generation of photoemissive aurophilic oligomers in water solution based on the 2-thiocytosine ligand

“…This is because of aurophilicity as the origin of the self-aggregation of gold( i ) centres at sub-van der Waals distances. 1,2 This close approximation of coordinatively unsaturated gold( i ) atoms is by no means innocent, as it induces (a) a deviation from the hardly-photoemissive ideal dicoordinate linearity of gold( i ), and (b) the mixing of suitable “atomic orbitals” (fully gold( i )-centered molecular orbitals would be a more realistic image) into pairs of new Au I ⋯Au I axis-centered molecular orbitals. Those new orbitals are now accessible by optical excitation of the sample, giving rise to one of the most appealing properties of gold( i ) complexes, photoluminescence.…”