Pergamon Tetrahedron 55 (1999) 2401-2418 TETRAHEDRON A Convenient Synthesis of Trimeric Porphyrins with Systematically Variable Geometry Warwick J. Belcher, Anthony K. Burrell*, Wayne M. Campbell, David L. Officer*, David C. W. Reid and Kirstie Y. Wild. IFS - Chemistry, Massey University,Private Bag 11222, PalmerstonNorth, New Zealand. Received 8 October 1998; revised 7 December 1998; accepted 7 January 1999 Abstract: A facile synthesisoftrimeric porphyrinsis reported. The geometry of the terminal porphyrins relative to the central macrocycle can be varied without significantchanges to the synthetic procedure. This procedurealso enables systematiccontrol over the metallationstates of the trimeric porphyrins. O 1999 ElsevierScienceLtd. All rights reserved. INTRODUCTION The extensive investigations into the primary events occurring within the reaction centers of photosynthetic bacteria have served to elucidate the mechanisms and dynamics of electron transfer within these membrane-bound proteins.I These investigations have been greatly assisted by a number of model studies incorporating derivatized porphyrins. 2 As a direct result of the continued search for realistic model systems many new synthetic routes to functionalized porphyrins have been developed. Of particular note are the advances reported in the synthesis of covalently-assembled multiporphyrin arrays) The synthesis of dimeric porphyrins represents major synthetic achievement in porphyrin chemistry. Yet today, thanks to the efforts of a number of research groups, dimerie porphyrins are becoming relatively common. Indeed, many much larger porphyrin arrays have been reported in recent years) However, even the preparation of dimeric porphyrins can require long and difficult synthetic procedures that result in the isolation of only small amounts of material. Nonetheless the chemistry displayed by the metal complexes of dimeric porphyrins is so intriguing that the laborious procedures are often worth the effort. Reactions such as the electrocatalytic reduction of oxygen to water by dicobalt face-to face porphyrins 4 and of dioxygen by diruthenium cofacial diporphyrins5 give some indication of the potential of these systems. To date, explorations of the chemistry oftrimeric or larger porphyrin arrays has been severely limited by the complex procedures that are required for their synthesis. Porphyrin arrays with specific metallafion sites could be useful for a variety of tasks such as light harvesting, small molecule activation, catalysis and molecular recognition. Here we report a convenient route to trimeric porphyrins that can be prepared in good yield, with a minimal number of steps. The methodology described gives good control over the metallation states of the trimeric porphyrin and enables simple control of the overall trimer geometry. 6 0040-4020/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. Pll: S0040-4020(99)00033-2