Syntheses and characterizations of polymeric silver iodoplumbates, and iodoplumbates with lanthanide complexes

Abstract

Novel heterometallic Ag–iodoplumbates [Ln(DMSO)₈]Pb₂Ag₂I₉ [Ln = La(1), Gd(2), Tm(3)] were prepared by reactions of LnCl₃, PbI₂, AgNO₃ and KI in dimethyl sulfoxide (DMSO). The same reactions without reactant AgNO₃ produced new iodoplumbates [Ln(DMSO)₈][(DMSO)Pb₄I₁₁] [Ln = La(4), Pr(5), Nd(6)]. All Ln³⁺ ions are solvated with eight DMSO molecules in the reactions, forming [Ln(DMSO)₈]³⁺ complex cations to act as counterions to the iodometallate anions. In compounds 1–3, two AgI₄ tetrahedra and two PbI₆ octahedra are connected into the 1D heterometallic Ag–Pb iodometallate [Ag₂Pb₂I₉]_n³ⁿ⁻via face-sharing. The [Ag₂Pb₂I₉]_n³ⁿ⁻ anionic chains run parallel along the b axis in 1, and along the a axis in 2 and 3. The [Ln(DMSO)₈]³⁺ cations are located between the chains. In compounds 4–6, two PbI₆ and two PbI₅O octahedra are interlinked end to end via sharing common faces to generate a 1D [(DMSO)Pb₄I₁₁]_n³ⁿ⁻ chain, which represents a new member of iodoplumbate aggregates. In the [(DMSO)Pb₄I₁₁]_n³ⁿ⁻ chain, the Pb²⁺ ions are joined not only via μ-I bridges, but also via μ-O bridges. The μ-O oxygen bridging has never been observed in iodoplumbates. Solid state optical absorption spectral analyses show optical band gaps in the range of 2.25–2.88 eV for compounds 1–6. Blue shift of the absorption edge caused by copolymerization of the AgI₄ unit occurs on the iodoplumbates.