Spring-loaded supramolecular chemistry: Pyridine-2-carboxaldehyde reacts with the m-phenylenediamine shown in aqueous solution in the presence of CuI ions to give a tetracopper(I) grid complex (see structure). This structure is stable in water, but not in any of the organic solvents tried. The strain incorporated into the structure is compensated by a diffuse pressure applied by the hydrophobic effect. R=2-hydroxyethylcarbamoyl.