The Metal–Metal‐to‐Ligand Charge Transfer Excited State and Supramolecular Polymerization of Luminescent Pincer Pd^II–Isocyanide Complexes

Abstract

Pincer PdII–isocyanide complexes are described that display intermolecular interactions and emissive 3MMLCT excited states in aggregation state(s) at room temperature. The intermolecular PdII−PdII and ligand–ligand interactions drive these complexes to undergo supramolecular polymerization in a living manner. Comprehensive spectroscopic studies reveal a pathway with a kinetic trap that can be modulated by changing the counteranion and metal atom. The PdII supramolecular assemblies comprise two different aggregation forms with only one to be emissive. DFT/TDDFT calculations lend support to the MMLCT absorption and emission of these pincer PdII–isocyanide aggregates.

Counteranion‐ and Solvent‐Mediated Chirality Transfer in the Supramolecular Polymerization of Luminescent Platinum(II) Complexes

“…Consistent with our previous study, wherein certain counteranions were found to block the free rotation between two complex cations, the dimer pairs blocked by OTf − are also observed in the crystal structure of (+1)‐OTf . Because of the relatively strong cation‐OTf − interaction, dimer pairs were considered to be the major packing forms in the aggregates of (+1)‐OTf .…”

“…For example, chiral d 8 Pt II complexes in the solid state have been reported to show intriguing mechanical and vapor‐induced helicity‐switching properties . Reports on the living supramolecular polymerization of Pt II complexes, however, are sparse,,, and the development of their chiral counterparts remains a challenge. We recently reported cationic pincer Pd II complexes that underwent kinetically controlled supramolecular polymerization mediated by cation–anion electrostatic and cation–cation dispersive interactions …”

Controlling Metallophilic Interactions in Chiral Gold(I) Double Salts towards Excitation Wavelength‐Tunable Circularly Polarized Luminescence

“…It is postulated that the strong aurophilic and Coulombic interactions drive the directional assembly of the double salts, giving rise to thermodynamically stable superstructures. Recently, we have disclosed anion‐mediated living supramolecular polymerization/oligomerization for a few Pd II and Au III complexes through affecting the metal⋅⋅⋅metal interactions . With this in mind, we envision to modulate the strength of Au I ⋅⋅⋅Au I and Coulombic interaction by adjusting steric hindrance of the ligand, together with the materials processing, so as to perturb the assembly formation kinetics.…”

“…Metallophilic interactions of d 8 and d 10 transition metal complexes,m ainly Pt II ,P d II ,R h I ,A u I complexes have been harnessed for developing photofunctional materials for decades. [11] Thes trong dependence of their excited states properties on the intermetallic contacts offers ac onvenient route to tune the photoluminescence color through modulating the M···M distances by means of mechanical stress,vapor fuming,a nd heating. [12] Distinct from the widely explored metallophilic interactions based on neutral [XAu(CNAr)] isocyanide complexes, [11k, 13] we have been focusing on Au I double salts,n amely [Au(NHC) 2 ][M(CN) 2 ]( M = Ag, Au), [12f, 14] in which the synergetic Au I ···M I interaction and Coulombic attraction direct the assembly into strongly luminescent nanostructures with almost unity photoluminescence quantum yield (PLQY).…”

Consequences of hidden kinetic pathways on supramolecular polymerization

“…Complex supramolecular polymerization behaviour of 1 Self-assembled structures of d 8 metal complexes exhibit particularly interesting photophysical properties [29][30][31][32][33] and the presence of the metal fragment oen enables multiple competing non-covalent interactions, which is benecial to create kinetic aggregates. [34][35][36][37] Preliminary self-assembly studies of the (S)-enantiomer of Pd complex 1, however, suggested the presence of a single supramolecular species if monomer solutions in methylcyclohexane (MCH) were cooled from 363 K to 283 K at a rate of 1 K min À1 .…”