Exploiting Aurophilic Interactions in a [2 + 2] Photocycloaddition: Single-Crystal Reactivity with Changes to Surface Morphology.

A single-crystal-to-single-crystal (SCSC) photodimerization is achieved using Au(I) coordination and aurophilic interactions. The rigid Au(dppbz)(CFCOO) precursor (dppbz = 1,2-bis(diphenylphosphino)benzene) self-assembles with 1,2--bis(4-pyridyl)ethylene (bpe) to afford a discrete [Au(dppbz)(bpe)] macrocycle in the solid state. The alkene undergoes a [2 + 2] photocycloaddition reaction. The photoreaction proceeds via a rare SCSC transformation in quantitative yield that generates [Au(dppbz)(4,4'-tpcb)] (4,4'-tpcb = -tetrakis(4-pyridyl)cyclobutane) stereoselectively. Mechanical strain induced by the photoreaction is evidenced by the formation of ramp features on single-crystal surfaces using scanning electron microscopy.