Conjugated Porphyrin Ladders

Abstract

A conjugated porphyrin dimer has been synthesized from a meso-diethynylporphyrin. The zinc complex of the dimer aggregates much more strongly (K Agg =1.2×10 -7 M -1 ) than its analogous monomer (K Agg =3-8×10 2 M -1 ) and forms a very stable 2:2 bladder complex with 1,4-diazatilcyclo[2-2-2]octane (K Agg =4×10 21 M -3 ), which is in slow exchange on the NMR time scale at 30 o C. The effective molarities for aggregation and bladder formation are 80 and 0.3 M, respectively. NMR ring current shifts and UV exciton coupling show that the porphyrins are coplanar in the aggregate