Optimizing Simultaneous Two-Photon Absorption and Transient Triplet−Triplet Absorption in Platinum Acetylide Chromophores

A series of platinum-containing organometallic dimer complexes has been synthesized and the photophysical properties have been investigated under one- and two-photon (2PA) absorption conditions. The complexes have the general structure [DPAF−C≡C−Pt(PBu3)2−C≡C−Ar−C≡C−Pt(PBu3)2−C≡C−DPAF], where Ar is a π-conjugated unit, Bu = n-butyl, and DPAF = diphenylamino-2,7-fluorenylene. The core Ar units include 1,4-phenylene, 2,5-thienylene, 5,5′-(2,2′-bithienylene), 2,5-(3,4-ethylenedioxythiophene, 2,1,3-benzothiadiazole, and 4,7-dithien-2-yl-2,1,3-benzothiadiazole. Absorption and photoluminescence spectroscopy indicates that the complexes feature low-lying excited states based on both the core [-Pt(PBu3)2−C≡C−Ar−C≡C−Pt(PBu3)2-] chromophore as well as the DPAF units. Photoexcitation of the complexes produces a singlet state excited state, which rapidly undergos intersystem crossing to afford a triplet state that has a lifetime in the microsecond time domain. In most cases, the lowest energy triplet state is localiz...