Contrast Solid-State Photoreactive Behavior of Two Two-Dimensional Zn(II) Coordination Polymers

A two-dimensional photoreactive coordination polymer (2D CP), [Zn-2(Fumarate)(2)(H2O)(2)(2F-spy)(4)] (1) (2F-spy = 2'-fluoro-4-styrylpyridine), undergoes partial [2 + 2] cycloaddition reaction under UV light in a single-crystal-to single-crystal manner to a three-dimensional (3D) CP [Zn-2(Fumarate)(2)(H2O)(2)(2F-spy)(3)(rctt-2F-ppcb)(0.5)] (2) (where rctt-2F-ppcb = 1,3-bis(4'-pyridyl)-2,4-bis(2'-fluoro-phenyl)cyclobutane), whereas another similar photoreactive 2D CP, [Zn-2(Fumarate)(2)(3F-spy)(2)] (3) (3F-spy = 3'-fluoro-4-styrylpyridine), when exposed to UV light, forms a cyclobutane ring arising from the hetero-cross-coupling of 3F-spy and fumarate, in addition to the expected cyclobutane ring, rctt-3F-ppcb (rctt-3F-ppcb = 1,3-bis(4'-pyridyl)-2,4-bis(3'-fluoro-phenyl)cyclobutane) by the [2 + 2] cycloaddition reaction of 3F-spy pairs aligned in a head-to-tail (HT) fashion. It is unusual to observe two different photoproducts in a solid-state [2 + 2] photo-cycloaddition reaction involving CPs. It is possible because the metal ions appear to support the reactions between two different types of ligands.