Abstract
The chemical reactivity of molecules in monolayers at the air-water interface is controlled by the molecular organization. Polycondensation and polymerization reactions as well as the reversible photoisomerization of a spiropyran-merocyanine system in mixed monolayers depend strongly on the applied surface pressure. The complex formation of a porphyrin in a mixed monolayer is controlled by the composition of the matrix. The limited mobility of molecules in monolayer systems requires the optimization of energy and electron transfer processes for efficient photochemical reactions.