SYNTHESIS OF PORPHYRIN QUINONES WITH ALIP HATIC AND CYCLOALIPHATIC BRIDGES AS MODEL COMPOUNDS FOR STUDYING THE LIGHT-INDUCED CHARGE SEPARATION IN PHOTOSYNTHESIS

Covalently linked porphyrin quinones (P-Qs) are well-suited as biomime tic model compounds in studying the light-induced charge separation oc curring in primary processes of photosynthesis. We report on a synthet ic strategy which leads to P-Qs with the porphyrin donor covalently li nked to the quinone acceptor via aliphatic and cycloaliphatic spacers. Preparation of two diastereomeric cyclohexylene-bridged P-Qs 1 and 2 and of 3 bearing a butylene spacer is described. Structures, including the spatial arrangements of the donor, bridge and acceptor, are deter mined by various NMR techniques. These data are compared with those de duced from simple force-field calculations using the molecular modelli ng program ALCHEMY II (Tripos Associates) and MNDO (MOPAC-6) calculati ons.