A solid state highly emissive Cu(i) metallacycle: promotion of cuprophilic interactions at the excited states

Abstract

The straightforward synthesis of a new Cu(i) metal-rich small metallacycle is presented. This compound is luminescent in the solid state with an emission quantum yield of 72% at room temperature and displays a pronounced reversible red-shift of its emission spectra upon cooling. Quantum chemical calculations reveal that these properties are governed by important geometrical relaxations that imply the formation of cuprophilic interactions at the excited states.

Cyanide‐Assembled d10Coordination Polymers and Cycles: Excited State Metallophilic Modulation of Solid‐State Luminescence

“…The latter was shown to have a crucial influence on the origin of emission and can be responsible for “switching” from TADF behaviour to pure T 1 → S 0 triplet emission . Notably, in the tetranuclear TADF luminophore [Cu 4 (μ 2 ‐dppm) 4 (CN) 2 ] 2+ (dppm=bis(diphenylphosphino)methane) the metallophilic contacts, even not operating in the ground state, may get activated upon photoexcitation as a result of molecular reorganization facilitated by a relative lability of the cyanide bridges . This approach to influence the properties of the emissive states through changing non‐covalent bonding in polymetallic systems seems to be an appealing strategy to design the emitters with adjustable optical behaviour that does not imply significant chemical modification of the ligand surrounding.…”

“…Most of the complexes exhibit two‐exponential decays at both 298 and 77 K that are not exceptional . A plausible explanation could be the presence of different emissive sites, for example, formed due to molecular disorder found in the crystal structures.…”

“…and provides the Δ E ( T 1 − S 1 ) energy difference between the S 1 and T 1 states of 491–779 cm −1 (Table ), which allows fast reverse ISC T 1 → S 1 at 298 K and therefore results in relatively short lifetimes of 3.9–13.6 μs upon warming. The prompt fluorescence lifetime derived for 6 ( τ ( S 1 )=129 ns) is comparable to its relatives studied here, and to other copper complexes with TADF property . Additionally, a relatively small gap Δ E ( T 1 – S 1 )=521 cm −1 and substantial SOC warrant efficient population of the S 1 state to give a TADF decay time of 4.4 μs at 298 K. The corresponding radiative rate constant for 6 ( k r =1.3×10 5 s −1 , 298 K) is visibly greater than those found for di‐ and tetranuclear TADF Cu(I) species with metal–metal interactions …”

“…The major structural variations, which occur upon one‐electron excitation, are associated with dramatic contraction of one intermetallic contact in each complex in both singlet and triplet excited states. The increase of the M–M bond order in the exciplex‐like forms of d 10 metal clusters has been highlighted in a number of earlier works . The most severe decrease of M … M separations has been predicted for complex 9 , which does not possess appreciable metallophilic bonds in the ground state (according to XRD and DFT analyses).…”

Binuclear Copper(I) Borohydride Complex Containing Bridging Bis(diphenylphosphino) Methane Ligands: Polymorphic Structures of [(µ2-dppm)2Cu2(η2-BH4)2] Dichloromethane Solvate

“…Rather, it has a tendency to act as either a monodentate (η 1 -dppm) or bridging bidentate ligand (µ 2 -dppm) [18]. Many examples The Cu(I)-dppm complexes are emerging class of polynuclear complexes, that are drawing considerable attention because of their photophysical properties [19][20][21][22] and prospective use as a catalyst [23][24][25] and a sensor for various organic bases [26] and anions [27]. Binuclear Cu(I) species possess an enhanced reactivity toward organic azides in copper-catalysed azide-alkyne cycloaddition compared to monomeric copper complexes [28][29][30][31][32][33][34][35].…”