Polymorphism and an unexpected reconstructive phase transition in [Cu(trop)(μ-OMe)]2 (trop = tropolonate) were studied by single crystal and powder X-ray diffraction; the phase transition is associated with a huge hysteresis of ca. 200 °C. In the readily reproducible crystal form, the methoxide-bridged dinuclear subunits aggregate to infinite chains by longer bonds in the Jahn-Teller distorted coordination sphere. Analogous alkoxide-bridged derivatives with the substituted ligand hinokitiol (hino), [Cu(hino)(μ-OR)]2 (R = Me, Et, iPr) form pairs of dinuclear complexes and aggregate to discrete tetranuclear molecules. The inter-cation distance patterns are reflected in the magnetic properties of these two structure types: Strong antiferromagnetic coupling within the dinuclear subunits is observed in either case, but susceptibility measurements confirm differences in exchange coupling between neighboring central CuII atoms.