Hydrogen bonded networks based on hexarhenium(III) chalcocyanide cluster complexes: structural and photophysical characterization

Two series of isostructural compounds resulting from the combination of the four-fold hydrogen bond donors bisamidinium cations, namely 1-2H(+) and 2-2H(+), and the anionic chalcocyanide clusters of general formula [Re(6)Qi8(CN)a6](4-) are presented (Q = S or Se; where i and a denote inner and apical position, respectively). 1-2H(+) is built upon two imidazolium groups linked together by a -(CH2)(2)- alkyl chain. 2-2H(+) is built upon two hydroxyamidinium groups linked together via a phenyl group and, in consequence, it exhibits a planar geometry. This ionic association leads to either two or three-dimensional hydrogen-bonded networks in the solid state, as confirmed by X-ray crystallographic analysis. The solid-state structures arise from the recognition between the pendant -C?N ligands of the cluster cores and the amidinium H-bond donors. The luminescence properties of the compounds are investigated in the solid state by means of steady-state and time-resolved techniques. Results are discussed and compared with those measured for the parent Cs-4[Re(6)Si8(CN)a6] and Cs-4[Re(6)Sei8(CN)a6] species. The H-bonded networks display featureless deep-red emission bands centered at (em) = 722 and 737 nm and average excited-state lifetimes ranging between 11.5 and 14.8 s, in accordance with the triplet nature of the radiative process. These photoluminescence properties are similar to the Cs+ homologues and are attributed to the [Re(6)Qi8](2+) emitting core.