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

• Published in: Journal of the American Chemical Society 2018-02, Vol.140 (6), p.2336-2347
• Main Authors: Mohankumar, Meera, Holler, Michel, Meichsner, Eric, Nierengarten, Jean-François, Niess, Frédéric, Sauvage, Jean-Pierre, Delavaux-Nicot, Béatrice, Leoni, Enrico, Monti, Filippo, Malicka, Joanna M, Cocchi, Massimo, Bandini, Elisa, Armaroli, Nicola
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Coordination chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b12671

A series of copper­(I) pseudorotaxanes has been prepared from bis­[2-(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 CH2Cl2. 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.