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A new series of electron-deficient porphyrins were prepared by attaching one or two N-methylated 2-, 3- or 4-pyridylethynyl groups to the 10,20-meso positions of (5,15-biphenylporphinato)zinc(II). Electrochemical studies showed significant changes in the reduction potentials of these porphyrins, and N-methyl-2-pyridylethyne is the strongest electron-withdrawing substituent in the series. UV-visible spectra demonstrated largely red-shifted absorptions, and N-methyl-4-pyridylethyne has the greatest impact to the porphyrin absorptions. Electrochemical, UV-visible and EPR results concluded that porphyrins Zn2 and Zn6 reversibly undergo two one-electron porphyrin-ring reductions to their anion radicals then dianions. The first reductions of porphyrins Zn1, Zn3, Zn4 and Zn5 were irreversible one-electron transfer processes. The instability of these reduction products was suggested to result from the eletrophilic attacks at the substituents.

Facile One-Step Synthesis of a Thia-Bridged Bis-1,10-phenanthroline Macrocycle. -A novel and convenient one-pot method for the synthesis of macrocycle (II) is reported. Furthermore, symmetrical NH-and S-bridged tetradentate ligands are also synthesized by this approach. -(WANG*, W.-J.; SENGUL, A.; LUO, C.-F.; KAO, H.-C.; CHENG, Y.-H.; Tetrahedron Lett. 44 (2003) 37, 7099-7101; Dep. Chem., Tamkang Univ., Tamsui, Taipei 25137, Taiwan; Eng.) -M. Paetzel 51-159

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