Metal–organic frameworks based on tri- and penta-nuclear manganese(ii) secondary building units self-assembled by a V-shaped silicon-containing dicarboxylate

Abstract

A bent V-shaped silicon-containing linker, bis(p-carboxyphenyl)diphenylsilane (H₂cpdps), has been used to synthesize two coordination polymers, [Mn₅(cpdps)(HCOO)₂(H₂O)₂(DMF)₄]·6DMF (1) (DMF – dimethylformamide) and [Mn₃(μ-H₂O)₂(Hcpdps)₂(cpdps)₂(DMF)₂]·2DMF·12H₂O (2). The crystal structure of both compounds was determined by single-crystal X-ray diffraction. In complex 1, pentanuclear manganese(II) secondary building units (SBUs) are held together by cpdps²⁻ ligands to form a 2D (4,4) coordination polymer. Crystal 2 is built of trinuclear manganese(II) SBUs that are held together by cpdps²⁻ and Hcpdps⁻ ligands within a 2D (4,4) coordination polymer. The magnetic susceptibility measurements revealed antiferromagnetic exchange interactions between the paramagnetic manganese(II) ions (d⁵). The exchange interactions are ranging between −0.6 and −2.25 cm⁻¹. Thermal analysis consisting in simultaneous thermogravimetry and automated FTIR analysis of the evolved gases permitted to evaluate the stability of the compounds and identify the main processes underlying decomposition. The void volumes accessible for particular guest molecules (CO₂, H₂O, Ar, N₂) were theoretical estimated on the basis of the crystallographic data. Water vapor sorption capacity was measured experimentally in dynamic regime at room temperature.