beta-tetraethyl-beta'-tetrapyridin-4-yl porphyrins, their N-methylated tetracations, and heterodimers with ms-tetraphenylsulfonato porphyrins

A mixture of the four regioisomers of beta-tetraethyl-beta'-tetrapyridin-4-yl porphyrins and their N-methylated tetracations has been synthesized. The crystal structure of regioisomer I is determined by complicated edge-on interactions between the pyridinyl substituents, which arrange as a ''bowl''. The nonseparable mixture of regioisomers III+IV is extremely well soluble in chloroform and, as tetramethylated tetracation, in water (congruent to 10(-1) M). It forms well-defined and water-soluble (5 x 10(-4) M) heterodimers with ms-tetraphenylsulfonatoporphyrin as a free base, a zinc and a copper complex (K-dimer = 1.3 x 10(8) M(-1)). Dimers containing one copper porphyrinate show no fluorescence. Cofacial porphyrin-porphyrin distances were estimated from transition dipole interaction as 7-8 Angstrom. Tetracationic zinc porphyrinates are stable against acid demetalation, the corresponding free base is not protonated down to pH 1. NH-Deprotonation has been achieved with sodium hydroxide and leads to chain-like assemblies in water. Application of the new porphyrins in vesicle entrapment measurements, formation of electron donor-acceptor pairs, and molecular assemblies is shortly discussed.