Porphyrin dimers linked in the meso-positions by bridges containing alkynes conjugated with the porphyrin π-systems display highly perturbed electronic absorption spectra. We have prepared a series of such dimers using meso-ethynyl nickel(II) octaethylporphyrin as the primary building block. The bridging units include diethynylbenzenes, 2,5-diethynylthiophene, hexenediyne, octatetrayne, butenyne, hexenediyne, and octadienediyne. Some meso-to-β dimers were also made. The dimers are complemented by a set of monomers containing the bridging units as mesosubstituents. The compounds were prepared by a combination of palladium-catalyzed couplings of alkynes with unsaturated halides and oxidative alkyne couplings. The separate effects of the substituents and the presence of the second porphyrin chromophore are delineated by comparisons of the visible absorption spectra for the various monomers and dimers. The dimers fit into three spectral classes: (i) those displaying strongly split Soret bands indicative of inter-porphyrin conjugation (diyne, tetrayne, enediyne, enyne, diethynylthiophene), (ii) those in which this conjugation is interrupted (diethynylbenzenes), and (iii) those with double bonds attached to the meso-carbons, which exhibit broad, low-energy bands, but small splittings of the Soret band. These illustrate some of the promising light-harvesting properties which can be achieved by tailoring the composition of the conjugating bridges linking the units in multi-porphyrin arrays.

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A cobalt porphyrin equipped with two different but geometrically complementary pyridine ligands self-assembles to form an unusually stable complex with approximately 12 porphyrin monomers arranged in a macrocyclic array.

A series of novel indolizine 2-oxoacetamides were designed and synthesized as PDE4 inhibitors. Preliminary SAR of this new class of compounds revealed key structural features required for high potency. Compounds 1ab and 2a are among the most potent inhibitors of PDE4 with low single nM IC 50 . Cellular activity was demonstrated by the inhibition of TNFa production from human PBMC with IC 50 ranging from 14 to 72 nM. Docking analyses suggest the OH group in 1ab enhance the binding via an H-bond interaction with the PDE4 enzyme.

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