Excitation of Highly Conjugated (Porphinato)palladium(II) and (Porphinato)platinum(II) Oligomers Produces Long-Lived, Triplet States at Unit Quantum Yield That Absorb Strongly over Broad Spectral Domains of the NIR

Transient dynamical studies of bis[(5 5`-10,20-bis(2,6-bis(3,3-dimethylbutoxy)phenyl)porphinato)palladium(II)] ethyne (PPd2), 5,15-bis{[(5`-10,20-bis(2,6-bis(3,3-dimethylbutoxy)phenyl)porphinato)palladium(II))ethynyl} (10,20-bis(2 6-bis(3 3-dimethylbutoxy)phenyl)porphinato)palladium(I) (PPd3), bis[(5,5`-10,20-bis(2,6-bis(3 3-dimethylbutoxy)phenyl)porphinato)platinum(II)ethyne (PPt2), and 5,15-bis {[(5`-10,20-bis(2,6-bis(3,3-dimethylbutoxy)phenyl)porphinato)platinum(II)]ethynyl} (10 20-bis(2,6-bis(3,3-dimethylbutoxy)phenyl)porphinato)platinum(II) (PPt3) show that the electronically excited triplet states of these highly conjugated supermolecular chromophores can be produced at unit quantum yield via fast S-1 -> T-1 intersystem crossing dynamics (tau(isc) 5 2-49 4 ps) These species manifest high oscillator strength T-1 -> T-n transitions over broad NW spectral windows The facts that (i) the electronically excited triplet lifetimes of these PPdn and PPtn, chromophores are long, ranging from 5 to 50 mu s and (ii) the ground and electronically excited absorptive manifolds of these multipigment ensembles can be extensively modulated over broad spectral domains indicate that these structures define a new precedent for conjugated materials featuring low-lying pi-pi* electronically excited states for NIR optical limiting and related long-wavelength nonlinear optical (NLO) applications