Naphthyl substituted Carbodiphosphoranes: Synthesis, Reactivity towards CuCl and Thermally Activated Delayed Fluorescence Properties

Herein we present the two-step synthesis of two new 2‑naphthyl substituted Carbodiphosphoranes (CDPs). In the first step either two equivalents of P(Naph)Ph 2 (Naph = 2-naphthyl-) and CH 2 Br 2 or P(Naph)Ph 2 and [Ph 3 P(CH 2 Br)]Br are reacted whereby the symmetrical bis phosphonium salt 1a and the unsymmetric salt 1b are obtained. Subsequently, the CDPs 2a and 2b where prepared by deprotonation with two equivalents of potassium hexamethyldisilazanide. After isolation, the coordination chemistry of 2a and 2b towards CuCl is explored where, depending on educt stoichiometry, mononuclear ( 3a , 3b ) and dinuclear compounds ( 4a , 4b ) are obtained. All prepared compounds were characterised by NMR spectroscopy, mass spectrometry and elemental analysis, and for 1a / b , 2a , 3b , and 4a / b single crystals suitable for X-ray diffraction studies could be obtained. Furthermore, the photophysical properties of the free 2-naphthyl substituted CDPs 2a / b and their corresponding Cu I complexes 3a / b and 4a / b have been investigated by steady-state and time-resolved luminescence studies at room temperature and at 77 K in various aggregation states, and further insight is provided by DFT/TD-DFT calculations. While 2a/b display features of thermally activated delayed fluorescence (TADF), 3a/b and 4a/b exhibit a much more complex excited state behaviour due to the interplay of metal-to-ligand charge transfer (MLCT) and napthyl ligand centered (LC) states, resulting in multiple simultaneous luminescence phenomena involving TADF, 1 LC and 3 LC emission.