This is a copy of the slides presented at the meeting but not formally written up for the volume.

We have explored the properties of triplet excited states in a series of platinum acetylide oligomers of the type [trans-Pt(PBu3)2(-CC-Ar)2], where Ar is a highly conjugated two-photon absorbing organic chromophore. Incorporation of two-photon absorbers into a pi-conjugated system produces short-lived excited states (fs/ps) with high efficiency. Platinum acetylide units introduce strong spin-orbit coupling into the pi-conjugated system to give rise to high yields of long-lived triplet excited states (ns/us) having large triplet-triplet absorption cross sections. Thus, a platinum acetylide having two-photon absorbers will, in principle, feature a strong non-linear absorption in broad time domain. The presentation will focus on (1) the synthesis and photophysical characterization under one- and two-photon excitation, (2) the effect of two-photon absorbing chromophores on nonlinear absorption properties of platinum acetylides and (3) the evidence for reverse saturable absorption.