The metacyclophanediene-dihydropyrene photochromic pi switch

This Microreview highlights the chemistry of the metacyclophanediene-dihydr opyrene system, which is a reversible photochromic pi switch. Although most studies have been carried out on systems with a single dihydropyrene, rece ntly multiple dihydropyrenes have been fused to conjugated spacers to give multi-state switches.