Two-Coordinate Dinuclear Donor-Gold(I)-Acceptor Complexes Exhibiting Multiple Excitation Wavelength Dependent Phosphorescence

Two-coordinate Au(I) complexes with a donor-metal-acceptor (D-M-A) structure have shown rich luminescent properties. However, charge-neutral dinuclear donor-metal-acceptor type Au(I) complexes featuring aurophilic interactions have been seldom explored. Herein, we describe the structures and photoluminescence properties of two dinuclear Au(I) complexes, namely DiAu-Ph and DiAu-Me. Single crystal X-ray structural analysis of DiAu-Ph reveals a short intramolecular Au-Au distance of 3.224 & Aring;. In dilute solution and doped films, excitation wavelength dependent multiple phosphorescence phenomena were observed for these dinuclear complexes. Theoretical calculations reveal that the aurophilic interaction causes increased contribution of the Au d orbital to the highest occupied molecular orbitals. Thus, the gap between singlet and triplet excited states (Delta EST) is enlarged, which disables the thermally activated delayed fluorescence (TADF). Moreover, the large energy separation (0.45-0.52 eV) and the different orbital configurations between the various excited states result in an inefficient internal conversion, accounting for their multiple phosphorescence properties. Dinuclear donor-Au-acceptor complexes with intramolecular aurophilic interactions were synthesized. The increased metal contribution to the highest occupied molecular orbital enlarges S1-T1 energy gap, which disables the thermally activated delayed fluorescence. Moreover, unexpected excitation wavelength dependent multiple phosphorescence was observed, attributed to the poor internal conversion originating from the large energy separation and spatially isolated orbital between various excited states. image