Energy Transfer on Demand: Photoswitch-Directed Behavior of Metal-Porphyrin Frameworks

In this paper, a photochromic diarylethene-based derivative that is coordinatively immobilized within an extended porphyrin framework is shown to maintain its photoswitchable behavior and to direct the photophysical properties of the host. In particular, emission of a framework composed of bis(5-pyridyl-2-methyl-3-thienyl)-cyclopentene (BPMTC) and tetrakis(4-carboxyphenyl)-porphyrin (H4TCPP) ligands anchored by Zn2+ ions can be altered as a function of incident light. We attribute the observed cyclic fluorescence behavior of the synthesized porphyrin-BPMTC array to activation of energy transfer (ET) pathways through BPMTC photoisomerization. Time-resolved photoluminescence measurements show a decrease in average porphyrin emission lifetime upon BPMTC insertion, consistent with an ET-based mechanism. These studies portend the possible utilization of photochrornic ligands to direct chromophore behavior in large light-harvesting ensembles.