The synthesis of six unsymmetrically substituted tetraarylporphyrins is reported. The compounds prepared are 5‐(R),10,15,20‐tritolylporphyrins, where R = 2‐pyridyl, 3‐pyridyl, 4‐acet‐amido, and 2,3 or 4‐hydroxyphenyl. Four new tetrasubstituted tetraarylporphyrins (5,10,15,20‐tetra‐(R)‐porphyrin) are also reported, where R = 3‐pyridyl, 4‐acetylphenyl, 4‐hydroxyphenyl and 4‐butoxyphenyl. The proton nmr spectra of these porphyrins are presented.

Three covalently-linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy (285%) from the excited singlet state of the Zn(1I) chromophore to the free base chromophore.No evidence for such transfer of the excited singlet state energy was found in the Ni(I1) or Cu(I1) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(I1) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin.The donor-acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor-acceptor distance of 15 A was calculated with an associated rate constant (ke,) for energy transfer of 1.9 x lo9 s-'.

The synthesis of covalently linked porphyrin dimers and trimers is described. Mono‐ and dihydroxyporphyrins were synthesized by transeslerifying 5,10,15,20‐tetra(4‐carbomethoxy‐phenyl)porphyrin with ethylene glycol. The mixture of transesterified porphyrins were separated by preparative thin layer chromatography. Metal derivatives were made of the mono‐ and dihydroxyporphyrins and these were reacted with the acid chloride of a monocarboxyporphyrin to yield hybrid dimers and trimers containing one melalloporphyrin and either one or two free base porphyrins. The structures and purity of the dimers and trimers were established by measuring the absorbance spectra, nmr spectra, and molecular weight by gel permeation chromatography.

No abstract

Gettysburg’s legacy is a well-chronicled highlight of American history. However, its significance as a revered battleground overshadows a forgotten Iroquoian group (Susquehannock) that occupied the region. The battlefield contains a diabase outcrop known as Devil’s Den that displays rounded blocks and weathered rectangular joints. Field reconnaissance identified a leaning rock slab that forms openings aligned to the summer and winter solstices. Moreover, the rock openings align with the rising and setting of Pleiades and Sirius, respectively, stellar objects tracked by northeastern Native Americans for agricultural and religious purposes. A petroglyph-bearing rock shadowed by the slab is the first known occurrence of petroglyphs in Adams County and only the 22nd documented case in Pennsylvania. Petroglyphs relating to select cardinal directions, Ursa major, and Manitou (Great Spirit manifestations) were situated for sunlight to interact with them during certain times of the year. The discovery of an Iroquoian calendar implies the region was utilised by a sedentary society.