γ-Cyclodextrin can be used to control the orientation of alkenes and direct their photodimerization into specific stereoisomers. This document reports on research investigating the use of γ-cyclodextrin to promote the selective photo-heterodimerization of cinnamic acid and coumarin derivatives. It was found that γ-cyclodextrin forms inclusion complexes that favor the head-to-head heterodimer product over homodimers. Substituents on the alkenes influence complex formation based on their steric and electronic properties. Electron-withdrawing groups may stabilize heterodimer formation through weak interactions. Overall, steric complementarity between guest molecules governs the