New barium-organic derivatives are introduced as countercations in the iodocuprates and -argentates to yield novel hybrids with unique structural motifs and bonding modes, many of them also showing vivid fluorescence on exposure to UV light. The tetrahedral MX4/trigonal-coplanar MX3 unit in these hybrids [Ba-2(DMSO)(12)Cu8I12] (1) and [Ba(tetraglyme)(2)]2[Ag8I12].EtOH (7) can be replaced by the M'I4/M'I3 unit without compromising their basic structural motifs, thus leading to the formation of the rare mixed Cu-Ag iodometalates [Ba-2(DMSO)(12)Cu4Ag4I12] (9) and [Ba(tetraglyme)(2)]2[CuAg7I12].EtOH (10), respectively. In contrast, a breakdown in the structure-directing properties of these iodometalates was observed in the mixed Ag-Pb iodometalate [Ba(tetraglyme)(2)]2[Pb2Ag2I10].2Me(2)CO (11), where the basic structure of the synthon [Ba(tetraglyme)(2)]2[Ag4I8] (8) was not retained due to the compulsory molecular rearrangement required as a result of replacing AgI4/AgI3 units with octahedral PbI6 units.