Self-Assembly of Ambivalent Organic/Inorganic Building Blocks Containing Re₆ Metal Atom Cluster: Formation of a Luminescent Honeycomb, Hollow, Tubular Metal-Organic Framework

Abstract

Reactions in a sealed glass tube between melted pyrazine (pyz) and a Cs(3)Re(6)Q(i)(7)Br(i)Br(a)(6).H(2)O inorganic rhenium cluster compound (Q = S, Se; "i" for inner and "a" for apical positions) containing [Re(6)Q(i)(7)Br(i)Br(a)(6)](3-) units led to the substitution of three apical bromine ligands by three pyrazine groups with the formation of 3 CsBr as a byproduct. The resulting fac-Re(6)Q(i)(7)Br(i)(pyz)(a)(3)Br(a)(3) building unit, based on a Re(6) metal atom cluster, is neutral and noncentrosymmetric and exhibits an ambivalent organic/inorganic nature owing to the opposite disposition of the three apical pyrazine groups versus the three apical bromine atoms. These compounds were characterized by single-crystal and powder X-ray diffraction, elemental and thermal analyses, and luminescence measurements. The crystal structure of fac-Re(6)Q(i)(7)Br(i)(pyz)(a)(3)Br(a)(3).xH(2)O (Q = S (1) and Se (2)) displays an original, neutral metal-organic framework based on the self-assembling of fac-Re(6)Q(i)(7)Br(i)(pyz)(a)(3)Br(a)(3) hybrid building units. The latter are held together by supramolecular interactions: pi-pi, hydrogen bonds (C-H...N, C-H...Br(a), and C-H...Br(i)), and van der Waals contacts. It gives rise to a honeycomb porous structure of parallel hollow open-ended channels wherein the water molecules are located. Their removal does not lead to the collapsing of the structural edifice. The channel walls are constituted by hydrogen atoms from pyrazine as well as apical bromine from the cluster unit. To our knowledge, the structures of 1 and 2 constitute with that of PTMTC (perchlorotriphenylmethyl functionalized by carboxylic group radicals) one of the rare examples of stable open frameworks stabilized by supramolecular interactions between neutral molecules. Moreover, 1 is the first example of luminescent Re(6) compound built up from a noncentrosymmetric Re(6)S(i)(7)Br(i) cluster core.

Low‐Dimensional Frameworks in Solid State Chemistry of Mo6 and Re6 Cluster Chalcohalides

“…[49] These three bridges are located on one side of the cluster unit while the three apical chlorines are located on the opposite side giving a fac geometry to this arrangement which is very rare in M 6 cluster solid-state chemistry. However, few examples of fac isomers have been reported in the literature in hybrid organic/inorganic Re 6 cluster compounds, for instance in [(n-C 4 H 9 ) 4 [72] However it is noteworthy that all these compounds were obtained by "soft" chemistry.…”

Octahedral clusters with mixed inner ligand environment: Self-assembly, modification and isomerism

“…Note that the neutral complexes with mixed-ligand apical ligand environment were obtained in reactions with a large excess of EPh 3 . Reactions of Cs 3 [{Re 6 Q 7 Br}Br 6 ]·H 2 O with molten pyrazine (pyz) were investigated [105]: it turned out that this reaction at 140 °C for 2 days in a sealed glass tube afforded very interesting supramolecular compounds, built up from fac-[{Re 6 Q 7 Br}(pyz) 3 Br 3 ] (Q = S, Se).…”

Synthesis and structures of new octahedral heterometal rhenium-osmium cluster complexes

“…Like the majority of previously studied chalcogenide octahedral rhenium cluster complexes [12,13,[23][24][25][26][27][28][29][30][31][32][33][34][35], the [Re 5 OsSe 8 (OH) 6 ] 3-in the solution shows broad and structureless emission in the wave length region from ~550 to longer than 950 nm with the maximum wavelengths (λ em ) centered at around 717 nm (Fig. 3).…”