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 photochromic
ligands to direct chromophore behavior in large light-harvesting ensembles.