  Cuprates and iron-based superconductors are two classes of unconventional
high Tc superconductors based on 3d transition elements. Recently, two
principles, correspondence principle and magnetic selective pairing rule, have
been emerged to unify their high Tc superconducting mechanisms. These
principles strongly regulate electronic structures that can host high Tc
superconductivity. Guided by these principles, here we propose high Tc
superconducting candidates that are formed by cation-anion trigonal bipyramidal
complexes with a d^7 filling configuration on the cation ions. Their
superconducting states are expected to be dominated by the d+id pairing
symmetry.
