AbstractStudies have shown that complex Zintl phases exhibit a rich diversity of crystal structures. These have also revealed a remarkable success of the Zintl concept in rationalizing stoichiometry, crystal structure and chemical bonding of many main group intermetallics. Still there are unresolved questions about the usefulness of the concept in explaining structure-property relationships in intermetallics near the Zintl border, and as a rational tool in designing new materials. Limitations of the concept are represented by violations often associated with “electron-deficient” phases that contain Group 13 metalloids. Recent investigations on “electron-deficient” Zintl phases containing post transition metals have led to the synthesis of a number of novel inorganic-intermetallic π-systems. Since unique structures and properties are already apparent in normal Zintl phases, it is anticipated that the exploratory synthesis and characterization of conjugated and multiple-bonded inorganic systems will produce not only unusual crystal chemistry but interesting physical properties as well. We report on new complex Zintl phases that include the semiconducting SrCa2In2Ge - which features [In2Ge]6- chains and represents a novel inorganic conjugated π-system analogous to a polyallyl chain with In-In double bonds, and Ca5In9Sn6 - which contains In trimers, [In3]5- analogous and isoelectronic with the aromatic cyclopropenium cation, [C3H3]+. These unusual materials, Zintl π-systems, represent a promising class of electronic materials with a range of potential applications.