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

Abstract

The series of cyanide-bridged coordination polymers [(P )CuCN] (1), [(P )Cu{M(CN) }] (M=Cu 3, Ag 4, Au 5) and molecular tetrametallic clusters [{(P )MM'(CN)} ] (MM'=Cu 6, Ag 7, AgCu 8, AuCu 9, AuAg 10) were obtained using the bidentate P and tetradentate P phosphane ligands (P =1,2-bis(diphenylphosphino)benzene; P =tris(2-diphenylphosphinophenyl)phosphane). All title complexes were crystallographically characterized to reveal a zig-zag chain arrangement for 1 and 3-5, whereas 6-10 possess metallocyclic frameworks with different degree of metal-metal bonding. The d -d interactions were evaluated by the quantum theory of atoms in molecules (QTAIM) computational approach. The photophysical properties of 1-10 were investigated in the solid state and supported by theoretical analysis. The emission of compounds 1 and 3-5, dominated by metal-to-ligand charge transfer (MLCT) transitions located within {CuP } motifs, is compatible with thermally activated delayed fluorescence (TADF) behaviour and a small energy gap between the T and S excited states. The luminescence characteristics of 6-10 are strongly dependent on the composition of the metal core; the emission band maxima vary in the range 484-650 nm with quantum efficiency reaching 0.56 (6). The origin of the emission for 6-8 and 10 at room temperature is assigned to delayed fluorescence. AuCu cluster 9, however, exhibits only phosphorescence that corresponds to theoretically predicted large value ΔE(S -T ). DFT simulation highlights a crucial impact of metallophilic bonding on the nature and energy of the observed emission, the effect being greatly enhanced in the excited state.

Luminescence Thermochromism of Gold(I) Phosphane–Iodide Complexes: A Rule or an Exception?

“…Nevertheless, ligand X has a noninnocent influence on luminescence efficiency because the iodide induces about a threefold increase in the radiative rate constant ( k r =1.5×10 5 s −1 for 10 vs. 5.8×10 4 s −1 for [(AuCN)(tpdp)]), and consequently, enhances the quantum yield of 10 ( Φ em =0.35) by a factor of four, with respect to its cyanide congener ( Φ em =0.08) . The radiative lifetime at 298 K for 10 ( τ r =5.1 μs) is compatible with thermally activated delayed fluorescence behavior, which has been suggested earlier for a [Au(dppb)(PS)] complex (PS=2‐diphenylphosphinobenzenethiolate), and thus, cannot be excluded for 10 , but still remains an extremely rare phenomenon for gold(I)‐containing compounds …”

Luminescent Tetranuclear Gold(I) Dibenzo[g,p]chrysene Derivatives: Effect of the Environment on Photophysical Properties

“…The linearity of the M-C≡C moiety and the preference of gold(I) for linear coordination makes alkynyl gold(I) compounds [10,11] attractive candidates for the design of discotic molecules derived from a DBC core. 2 of 11 Gold(I) complexes are very well known to display aurophilic (Au(I)···Au(I)) interactions, and this particular property modulates the energy of excited states while retaining the coordination sphere and remaining capable of considerably affecting the photophysical properties of the polymetallic molecules [12]. These aggregates can affect the molecules' photophysical properties and introduce a scaling up of the spin-orbit coupling (SOC), which is enhanced by metallophilic bonding.…”

Excitation‐Wavelength‐Dependent Emission and Delayed Fluorescence in a Proton‐Transfer System

“…The ESIPT leads to significant spatial separation of HOMO and LUMO which reduces the singlet–triplet (S 1 –T 1 ) energy separation, Δ E ST . Importantly, small Δ E ST values (≤0.2 eV or 19 kJ mol −1 ) facilitate thermally activated delayed fluorescence (TADF) . In this case, the T 1 →S 1 →S 0 pathway is used for radiative relaxation (Scheme ) .…”

“…[25][26][27][28][29][30][31][32][33][34] In this case, the T 1 !S 1 !S 0 pathwayi su sed for radiativer elaxation (Scheme 2). [25][26][27][28][29][30][31][32][33][34] The TADF process allows the internal quantum efficiency of organic light emitting diodes (OLEDs) to reach1 00 %d ue to harvesting both singlet and triplete xcitons. Despite the ESIPT process brings about significant spatial separationo fH OMO and LUMO in the ESIPT molecules, however,t here are only two attempts to design chromophores benefiting from interplay between ESIPT and TADF.…”