Solid State Packing and Photoreactivity of Alkali Metal Salts of <i>trans</i>,<i>trans</i>-Muconate

Abstract

Three alkali-metal salts of <i>trans</i>,<i>trans</i>-muconate (<i>muco</i>) <i>viz</i>. Li₂<i>muco</i> (<b>1</b>), Na₂<i>muco</i> (<b>2</b>), and K₂<i>muco</i> (<b>3</b>) have been prepared, and the influence of the crystal packing on the solid state photoreactivity has been investigated. Although the CC bonds of the <i>muco</i> ligands are oriented infinitely parallel in <b>1</b>, it was found to be photoinert. In contrast, the <i>muco</i> ligands of <b>2</b> and <b>3</b> in the crystalline state undergo photodimerization yielding cycloocta-3,7-diene-1,2,5,6-tetracarboxylate which has been formed stepwise via the [2 + 2] cycloaddition reaction of a single pair of CC bonds and subsequent Cope rearrangement. This study demonstrates how the size of the metal ion can influence the crystal packing in metal organic salts