13 The goal for the research described herein is the development of a series of transition metal based metal organic chromophores that display both two-photon and excited state absorption (TPA/ESA) character. With this goal in mind, we present the preparation and photophysical characterization for a series of metal-organic chromophores containing a two photon absorbing bipyridine core combined with a transition metal component which yields a long-lived triplet excited state. The combination of these two photophysical properties represents a dual mode nonlinear optical (NLO) mechanism. Three major areas of interest for this project are addressed here. First, to develop and instrument an in-house photophysical apparatus with the ability to evaluate and measure two photon activity as well as detect nonlinear optical responses. Second, to synthesize, characterize and evaluate an all organic chromophore system, centered on a bipyridine core, which utilizes known TPA architecture. Lastly, to synthesize, characterize and evaluate the metal organic analogs of the TPA chromophore system utilizing transition metals with high spin-orbit coupling values which help create long-lived triplet excited states leading to a possible ESA. The metalorganic analogs in turn should exhibit a dual mechanism for NLO response comprised of both TPA and ESA.