Reactions of metal iodides as a simple route to heterometallics: synthesis, structural transformations, thermal and luminescent properties of novel hybrid iodoargentate derivatives templated by [YL8]3+ or [YL7]3+cations (L = DMF or DMSO)

Abstract

A 1 : 3 molar reaction of YI₃ and AgI in dimethylformamide (DMF) in the presence of NH₄I afforded [Y(DMF)₈][Ag₃(μ₃-I)(μ-I)₃I₂] (1) with good yield, whereas the similar reaction in dimethylsulfoxide (DMSO) gave complexes [Y(DMSO)₈][Ag₂(μ-I)₃I₂] (2) and/or [Y(DMSO)₈]₂[Ag₄(μ₃-I)₂(μ-I)₄I₂][I]₂ (3), depending on the reaction and crystallization conditions. These discrete heterometallic hybrid compounds 1–3 undergo solid- and solution-state transformations via condensation of iodoargentate anions. So in the confined and solvent-free environment of paratone, crystals of 1 transformed into a 1D zig-zag structure [Y(DMF)₈]³⁺[Ag₆(μ₄-I)₂(μ₃-I)₂(μ-I)₅]_1∞³⁻ (4), whereas those of 2 were first converted into 3 and finally into [Y(DMSO)₇]₄[Ag₄(μ₃-I)₄I₄]₃ (5). In solution phase, re-crystalization of 1 or 2 from DMSO–toluene gave 3 as an exclusive species, whereas reaction of 1 with 3 equiv of AgI in DMF afforded 4 with good yield. Alternatively, 4 could also be synthesized with excellent yield from a 1 : 6 molar reaction of YI₃ and AgI. The above transformations suggest that, for a given metal–organic cation, an iodometallate cluster with higher nuclearity is thermodynamically more stable. Single crystal X-ray structures are reported for all the compounds and a mechanism for the structural transformation of 2 to 3 is proposed. In addition, spectroscopic, thermo-gravimetric and luminescent properties of the complexes 1, 3 and 4, which were obtained exclusively and in pure form, are also described.