Tetravalent Silicon Connectors Me_nSi(p-C₆H₄CO₂H)_4−n(n= 0, 1, 2) for the Construction of Metal−Organic Frameworks

Abstract

A series of silicon-centered connecting units, Me(n)Si(p-C6H4CO2H)(4-n) (n = 0, 1, 2), have been prepared and their coordination polymers with Zn(II) metal atoms studied. The tetra-acid L1 (n = 0) acts as a tetrahedral node and reacts with Zn(II) centers to give 1, a novel interpenetrating 3D network containing distorted tetrahedral bimetallic secondary building units (SBUs). The triacid L2 (n = 1) acts as a trigonal pyramidal node and forms an intercalated 2D layered network, 2, with Zn(II) ions, containing distorted octahedral tetranuclear SBUs. Last, the bent diacid L3 (n = 2) reacts with Zn(II) centers to give 3, a corrugated 2D layered structure containing 1D zinc hydroxo chains. Together these three new coordination polymers demonstrate the potential versatility of tetravalent silicon containing connecting ligands for metal-organic framework construction.

Siloxane-based linkers in the construction of hydrogen bonded assemblies and porous 3D MOFs

“…3,4 We have been interested for some time in the synthesis of highly branched organosilicon linkers and their use in the assembly of MOFs, largely due to their synthetic accessibility compared to their carbon-centred analogues. [5][6][7][8][9][10] However, despite the siloxane linkage (Si-O-Si) being ubiquitous in many classes of materials including zeolites, 11,12 periodic mesoporous organosilicas, 13,14 POSS hybrids and other porous materials, 15,16 we were surprised to find that there has been little interest in siloxane-based linkers [17][18][19][20][21] for MOFs, and that their incorporation into a porous 3D MOF has not been reported to date. We have thus recently focussed upon the development of siloxane-based polycarboxylates, and report herein the synthesis of the novel pseudooctahedral hexa(4-carboxyphenyl)disiloxane molecule (L1-H 6 ), its unusual hydrogen bonded network assembly and its application in the preparation two new MOF materials.…”

Structural Diversity in Metal−Organic Frameworks Built from Rigid Tetrahedral [Si(p-C6H4CO2)4]4− Struts

“…17 Contrary to previous assumptions, 13,14 this therefore shows that given the appropriate synthetic conditions, silicon-based connectors can be used to directly replace carbon based connectors in MOF construction, leading to isostructural products. The main advantage of using silicon-based L over L1 lies in its relatively facile synthetic accessibility.…”

“…20 The analogous silicon based connector L, which is the focus of study in this paper, has been used in the construction of morphologically different Zn(II) based MOFs by Lambert 14 and ourselves. 13 In addition, Lambert has also reported a Zn(II) MOF with the germanium-centered ligand L2. 14 A small number of studies involving the adamantyl based tetracarboxylates L3 and L4 have also been reported with Cu(II), Zn(II), Cd(II) and Ni(II) based SBUs.…”

“…12 We have been interested in the preparation of novel silicon-based connecting units for the construction of MOFs. 13 When compared to their carbon analogues, the increased bond angle flexibility, decreased conformational rigidity and the longer bond lengths to silicon have been shown in some cases to contribute to the formation of coordination polymers with novel topological and structural forms. [13][14][15] Moreover, tetrahedral silicon centers are in general more synthetically accessible than their carbon equivalents, and are thus promising candidates for a series of new connecting units with easily modifiable structural and chemical properties.…”

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

“…Oligosilanes, molecules with Si−Si bonds, are a class of hybrid inorganic‐organic materials with remarkable light absorption and charge transport properties that uniquely combine flexibility and strong light absorption, a property that inspired us to construct 2D MOFs based on oligosilyl linkers. While organosilicon species have been previously used in MOF formation, the organic linker usually contains a single Si atom, which precludes access to properties inherent to σ‐conjugated extended oligosilanes.…”