Three-coordinated mononuclear Cu(I) complexes with crystallization-enhanced thermally activated delayed fluorescence characteristics

Stabilization of Luminescent Mononuclear Three‐Coordinate CuI Complexes by Two Distinct Cavity‐Shaped Diphosphanes Obtained from a Single α‐Cyclodextrin Precursor

“…Compared to analogous cavity‐free trigonal [CuX(PP)] complexes studied by Osawa et al., [5a,b] Daly et al., [5d] and Du, Zhang et al., [5f] the PLQYs of the systems presented here are significantly lower, whether in solution or in the solid state, and more in line with those observed by Liu, Zhong, Wang, Wong, Cong et al [5c] . On the other hand, the excited state lifetimes in amorphous films at room temperature of all of our Cu I complexes are about two‐orders of magnitude longer than those observed by Osawa [5a] .…”

“…This behavior has been observed previously in Cu I complexes [26] and highlights the predominance of rigidochromic effects in the glass matrix on electronic effects. The excited state lifetimes (also measured by exciting outside the free ligand absorption window) are generally biexponential, as it often happens with Cu I complexes with phosphane ligands [5f,26b] . At 298 K, the longer component (in the range 220–230 ns) is largely predominant for 8 a – 8 c .…”

“…The two absorption features characteristic of the complexes are similar to those observed in trigonal Cu I analogues. They can be assigned to a mixed transition (σ→π* and π→π*) and to an X→π* transition (where X is Cl, Br, or I) [5a,c,f,13,20] . The absorption spectral shapes and intensities of the free ligands in CH 2 Cl 2 do not vary significantly over time.…”

“…The nature of the halide ions, which are directly bound to the copper center, notably affects the luminescent excited state. The latter has a charge transfer character, where the donor orbital can be both on the Cu center and on the halogen atom, whereas the acceptor is an antibonding orbital on the phosphane ligand (Cu→π*, MLCT; X→π*, XLCT) [5c,f] . In particular, a decrease in the ligand‐field strength reduces the splitting of the d‐orbitals on the Cu center, leading to a larger MLCT energy and a shorter emission wavelength [20,24d,e] .…”

Columnar Liquid Crystals of Copper(I) Complexes with Ionic Conductivity and Solid State Emission

“…Over the last few years, we have seen an increase in the development and manufacture of materials for emission applications (OLEDs, luminescence-based sensors, etc.). In this respect, the search for new emitting materials have led to low-cost copper(I) complexes, which can show exceptional luminescent properties, including thermally activated delayed fluorescence (TADF) and high emission efficiencies of nearly 100%, by using both singlet and triplet excitons, despite small spin-orbit coupling [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Copper represents a cheaper alternative to that offered by platinum or iridium (commonly used in practical lighting applications) due to its higher natural abundance (27 ppm) as well as lower production costs.…”