Luminescent Complexes of the Trinuclear Silver(I) and Copper(I) Pyrazolates Supported with Bis(diphenylphosphino)methane.

The first example of trinuclear copper(I) and silver(I) pyrazolates adducts with a tertiary diphosphine (Ph ₂ PCH ₂ PPh ₂ ) retaining trimeric [MPz] ₃ core is reported. Despite rather strong M-P bonding, the complexes are able to undergo the dissociation of one M-P bond leading to the "merry-go-round" movement of P atoms over the M ₃ triangle. The copper complex displays emission from ¹ MLCT and ³ MLCT states. The triplet and singlet states are separated by a relatively small energy gap (1080 cm ^-1 ) that triggers the thermally activated delayed fluorescence (TADF) behavior and leads to the worthy quantum yield of 41% at 298 K. The silver complex in the solid state and frozen solution shows dual emission originating from the ¹ IL and ³ MLCT states that is dictated by the much higher energy difference between the emissive singlet and triplet as well as by the essentially different nature of these states.