Hydrogen bonds and steric effects induced structural modulation of three layered iodoplumbate hybrids from nonperovskite to perovskite structure

Abstract

Directed by diprotonated organic diamines containing both primary and tertiary ammonium groups, three layered iodoplumbate hybrids, {[H₂DMPDA][PbI₄]}_n (1), {[H₂DEPDA]₄[Pb₅I₁₈]}_n (2) and {[H₂TMEDA][Pb₃I₈]}_n (3) (DMPDA = N,N-dimethyl-1,3-propanediamine, DEPDA = N,N-diethyl-1,3-propanediamine, TMEDA = N,N,N′,N′-tetramethylethylenediamine), have been synthesized solvothermally. 1 presents a layered perovskite structure based on corner-sharing PbI₆ octahedra, compound 2 consists of a Pb₄I₂₀ perovskite motif and a Pb₂I₁₀ dimeric motif and compound 3 comprises Pb₃I₁₃ units connected by face-sharing and edge-sharing modes. Structural modulations from nonperovskite to perovskite structure are strongly correlated to steric effects and hydrogen bonding interaction at the organic–inorganic interface. Band gaps for 1–3, estimated as 2.21, 2.58 and 2.73 eV, respectively, also reveal an interesting correlation with structural modulation, and the red shift for 1 is attributed to large Pb–I_equatorial–Pb bond angles.