The synthesis of the A,D-1,10-phenanthroline-bridged calixarene 3 is improved by applying a new strategy for the synthesis of the important intermediate 2,9-bis(bromomethyl)-1,10-phenanthroline (2) and variation of the bridging conditions. Crystals were obtained from two different solvent systems. Two structures were determined by X-ray studies. Both analyses reveal a rare conformation for A,D-bridged ca-lixarenes (uduuuu). Calculations with different methods were performed for this and other relevant conformers, and revealed various local minima. The uduuuu conformation also explains the molecular asymmetry evident in low-temperature NMR spectra of metal complexes of 3. (c) Wiley-VCH Verlag GmbH T Co. KGaA, 69451 Weinheim, Germany, 2005).