Coordination Polymer-Mediated Molecular Surgery for Precise Interconversion of Dicyclobutane Compounds.

A Cd(II)-based coordination polymer {[Cd 2 (5-F-1,3-bpeb) 2 (FBA) 4 ]·H 2 O} n ( CP 1 ) was obtained from Cd(II) salt, 5-fluoro-1,3-bis[2-(4-pyridyl)ethenyl]benzene (5-F-1,3-bpeb), and p -fluorobenzoic acid (HFBA). Within the one-dimensional chain structure of CP 1 , a pair of 5-F-1,3-bpeb was arranged in a face-to-face style. Upon UV irradiation and heat treatment, multiple cyclobutane isomers, including specific monocyclobutanes ( 1 with an endo -cyclobutane ring in CP 1 -1 and 1' with an exo -cyclobutane ring in CP 1 -1' ) and dicyclobutanes ( endo , endo -dicyclobutane 2α in CP 1 -2α , exo , endo -dicyclobutane 2β in CP 1 -2β , and exo , exo -dicyclobutane 2γ in CP 1 -2γ ) were stereoselectively produced. These isomers could be interconverted inside the CP via cutting/coupling specific bonds, which may be regarded as a type of molecular surgery. The precision of cutting/coupling relied on the thermal stability of the cyclobutanes and the alignment of the reactive alkene centers. The conversion processes were tracked through nuclear magnetic resonance, in situ powder X-ray diffraction, and IR spectroscopy. This approach can be considered as skeletal editing to construct complex organic compounds directly from one precursor.