Adlayers of 15-crown-5-ether-substituted cobalt(I I) phthalocyanine (CoCRPc) were prepared by immersion of either Au(111) or Au(1 00) substrate into benzene-ethanol (9:1 v/v) mixed solutions containing CoCRPc. In situ STM imaging was carried out after transferring the CoORPc-modified Au crystals into aqueous HClO4 solution. The packing arrangement of the CoCRPc array on Au(1 11) was determined to be p(8 x 4 root3R - 30degrees), and the internal structure was clearly observed by high-resolution STIVI. Two adlayer structures of CoCRPc, (8 x 9) and (4root5 x 4root5)R26.7degrees, were found on the Au(100)-(1 x 1) terrace. In the presence of 1 mM Ca2+, two Ca2+ ions were trapped in two diagonally located 15-crown-5-ether moieties of each CoCRPc molecule on Au(1 11), whereas encapsulation of Ca2+ ions was not seen in the CoCRPc arrays on the Au(100)-(l x 1) surface. The present study demonstrates that the relationship between crown moieties of CRPc and the underlying Au lattice is important in the trapping of Ca2+ ions in crown rings.