Heteroleptic Copper(I) Pseudorotaxanes Incorporating Macrocyclic Phenanthroline Ligands of Different Sizes

A series of copper(I) pseudorotaxanes has been prepared from bis2-(diphenylphosphino)phenyl ether (POP) and macrocyclic phenanthroline ligands with different ring sizes ( m30, m37, and m42 ). Variable-temperature studies carried out on the resulting Cu( mXX )(POP) + ( mXX = m30, m37, and m42 ) derivatives have revealed a dynamic conformational equilibrium due to the folding of the macrocyclic ligand. The absorption and luminescence properties of the pseudorotaxanes have been investigated in CH 2 Cl 2 . They exhibit metal-to-ligand charge-transfer emission with photoluminescence quantum yields (PLQYs) in the range 20–30%. The smallest system Cu( m30 )(POP) + shows minimal differences in spectral shape and position compared to its analogues, suggesting a slightly distorted coordination environment. PLQY is substantially enhanced in poly(methyl methacrylate) films (∼40−45%). The study of emission spectra and excited-state lifetimes in powder samples as a function of temperature (78–338 K) reveals thermally activated delayed fluorescence, with sizable differences in the singlet–triplet energy gap compared to the reference compound Cu(dmp)(POP) + (dmp = 2,9-dimethyl-1,10-phenanthroline) and within the pseudorotaxane series. The system with the largest ring (Cu( m42 )(POP) + ) has been tested as emissive material in OLEDs and affords bright green devices with higher luminance and greater stability compared to Cu(dmp)(POP) +, which lacks the macrocyclic ring. This highlights the importance of structural factors in the stability of electroluminescent devices based on Cu(I) materials.