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Hybrid layered double perovskite (HLDP) halides comprise hexacoordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and organic amine cations between the layers. Progress on such materials has hitherto been limited to compounds containing main group 3+ ions isoelectronic with PbII (such as SbIII and BiIII). Here, we report eight HLDP halides from the A2MIMIIIX8 family, where A = para-phenylenediammonium (PPDA), 1,4-butanediammonium (1,4-BDA), or 1,3-propanediammonium (1,3-PDA); MI = Cu or Ag; MIII = Ru or Mo; X = Cl or Br. The optical band gaps, which lie in the range 1.55 to 2.05 eV, are tunable according to the layer composition, but are largely independent of the spacer. Magnetic measurements carried out for (PPDA)2AgIRuIIICl8 and (PPDA)2AgIMoIIICl8 show no obvious evidence of a magnetic ordering transition. While the t2g3 MoIII compound displays Curie-Weiss behavior for a spin-only d3 ion, the t2g5 RuIII compound displays marked deviations from the Kotani theory.
Vishnoi et al. (Mon,) studied this question.