Solid-state structural transformations in metal organic-inorganic hybrids constructed from terbium(iii) complexes and iodocuprate clusters

Abstract

Using precursors of the type [Tb(DMSO)₈]I₃ (a) and [Tb(DMF)₈]I₃ (b), syntheses of two new heterometal organic–inorganic hybrid complexes based on discrete iodocuprate clusters [Tb(DMSO)₈][Cu₂I₅] (1) and [Tb(DMF)₈][CuI₃][I] (2), respectively, are reported. Though stable in air for few days, the colorless complex 1 slowly turns into a purple-colored mixture over the course of several days. Two complexes, namely [Tb(DMSO)₈][CuI₃][I] (3) and [Tb(DMSO)₈](I)₂(I₃) (4), were isolated from this mixture and characterized structurally, the I₃⁻ anion in latter being responsible for the purple color of this mixture. In comparison, complex 2 is quite deliquescent in air but undergoes solid state structural transformation in a confined environment of paratone to afford a 2D honeycomb-like microporous structure containing mixed-valent copper atoms [Tb(DMF)₆(H₂O)₃][Cu^II₂Cu^I₇I₁₄]_2∞ (5), the bifurcate H-bonding between water ligands on terbium and iodides of the Cu–I cluster playing a pivotal role in the evolution of its structure. Single crystal X-ray structures are reported for all the complexes. Thermal and luminescent properties of 1 and 2, complexes, which were obtained exclusively and in pure form, are described. Compared to the precursor terbium iodide complexes (a) and (b), the high energy transitions in the excitation spectra of the complexes 1 and 2 are quenched by auto-ionization of the carriers in the material.