Unprecedented single-crystal-to-single-crystal topochemical conformational change and photoreduction of ethylene units in π-stacked metallomacrocycle

Neutral π-stacked metallomacrocycle was prepared using fac-Re(CO)3, and linear ditopic π-conjugated nitrogen donors in water–toluene mixture under reflux condition. Two ethylene units in the cycle are parallel to each other with a distance of 3.4 Å, which undergo topochemical conformational change from a parallel conformation to criss-cross conformation and photoreduction under UV-light irradiation through single-crystal-to-single-crystal transformation (SCSC). The π-stacked cycle and its photoproducts were characterized by 1H NMR spectroscopy and X-ray diffraction studies.

Graphical abstractNeutral π-stacked metallomacrocycle was prepared. Ethylene units in metallacycle undergo topochemical conformational change from parallel conformation to criss-cross conformation and photoreduction under UV-light irradiation through single-crystal-to-single-crystal transformation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Neutral π-stacked metallomacrocycle ► Metallacycle to metallacycle via single-crystal-to-single-crystal transformation. ► Topochemical conformation change and reduction via SCSC under light. ► Transformation of CC bonds from a parallel to criss-cross conformation in the cycle.