Structural Diversity in 2,2′-[Naphthalene-1,8:4,5-bis(dicarboximide)-<i>N,N</i>′-diyl]-bis(ethylammonium) Iodoplumbates

Abstract

Crystallization from solutions containing 2,2'-[naphthalene-1,8:4,5-bis(dicarboximide)-<i>N,N</i>'-diyl]-bis(ethylammonium) diiodide ((NDIC2)I₂) and PbI₂ has been investigated. Eight different materials are obtained, either by variation of crystallization conditions or by subsequent thermal or solvent-induced transformations. Crystal structures have been determined for five materials. [(NDIC2)₂Pb₅I₁₄(DMF)₂]·4DMF (DMF = <i>N,N</i>-dimethylformamide) (<b>1</b>), [(NDIC2)Pb₄I₁₀]·4DMF (<b>3</b>), [(NDIC2)Pb₂I₆]·4NMP (NMP = <i>N</i>-methyl-2-pyrrolidone) (<b>4</b>), and [(NDIC2)Pb₂I₆]·2H₂O (<b>5</b>) form 1-dimensional (1D) chains consisting of PbI₆ (and, in the case of <b>1</b>, PbI₅(DMF)) octahedra, either solely face-sharing or a mixture of face-sharing and vertex-sharing. The structure of [(NDIC₂)₃Pb₅I₁₆]·6NMP (<b>2</b>) contains 0D clusters; these consist of three PbI₆ octahedra and two unusually coordinated lead centers that exhibit three relatively short Pb-I bonds, two very long Pb-I contacts, and η²-coordination of an aromatic ring of NDIC2 to the lead. Close contacts between iodide ions and the imide rings of NDIC2 in four of the structures suggest that an iodide-to-NDIC2 charge-transfer interaction may be responsible for the observed red coloration of the materials. The optical and electrical properties of <b>1</b> have been studied; its onset of absorption is at 2.0 eV, and its conductivity was measured as 5.4 × 10^-5 ± 1.1 × 10^-5 S m^-1.