Isoreticular Investigation into the Formation of Four New Zinc Alkylbisphosphonate Families

Abstract

Through the systematic investigation of zinc alkylbisphosphonates, four new structural families have been obtained. These families are named zinc alkyl-tunnel, -gate, -cation, and -sheet (ZAT, ZAG, ZAC, and ZAS) for convenience and have been synthesized and further extended through isoreticular design utilizing alkylbis(phosphonic acid) ligands of the formula H2O3P­C n H 2n ­PO3H2 (n = 3–6) (H 4 L n ). Both even- and odd-length chains were utilized to help determine the effect of chain conformation on structure formation. The investigation lead to two known compounds (ZAG-4, and ZAS-3) and nine new compounds, two of which contain large 1-D channels. The crystal structures of all compounds were determined by single-crystal X-ray diffraction. Of the nine new compounds, only seven of them fall into the new families. In three of the four families, the structure is controlled by alkyl-chain length and conformation (i.e., odd vs even), and in the fourth, a conformational distortion allows both odd and even lengths to form the given structure. Isoreticular species using n = 3 and 5 were obtained in both the ZAT and the ZAS families; using n = 4 and 6 were obtained in the ZAG family; and n = 4–6, in the ZAC family.

Responsive Metal–Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with Friends

“…The second example is found in the zinc alkyl gate (ZAG) family of zinc phosphonate MOFs . Two materials from this family, ZAG-4 and ZAG-6, exhibit negative linear compressibility at high pressure, due to a pressure-induced reversible proton transfer between an included water molecule and the linker’s phosphonate group .…”

“…44 The second example is found in the zinc alkyl gate (ZAG) family of zinc phosphonate MOFs. 45 Two materials from this family, ZAG-4 and ZAG-6, exhibit negative linear compressibility at high pressure, 46 due to a pressure-induced reversible proton transfer between an included water molecule and the linker's phosphonate group. 47 This phenomenon was revealed by combining high-pressure single-crystal X-ray crystallography and quantum mechanical calculations and has potential applications as a pressure-switchable proton conductor.…”

Remarkable Pressure Responses of Metal–Organic Frameworks: Proton Transfer and Linker Coiling in Zinc Alkyl Gates

“…Here, we report a study of the behavior under pressure of two zinc alkyl gate (ZAG) materials, − a family of metal–organic frameworks that present a common wine rack geometric motif but use alkyl chains as the linker molecules, by combining in situ single-crystal X-ray diffraction at high pressure and quantum chemical calculations. We show that both materials, ZAG-4 and ZAG-6, exhibit negative linear compressibility at high pressure and demonstrate that this NLC is due to the occurrence of a pressure-induced structural transition involving a reversible proton transfer between an included water molecule and the linker’s phosphonate group.…”

Flexible MOFs under stress: pressure and temperature

“…Our own interests centered on metal phosphonates with both rigid and flexible linkers. [9][10][11][12] Among the compounds synthesized were alkyl C 4 H 8 and C 6 H 12 diphosphonates of zinc. 11 Our purpose was to determine how a small pore MOF with flexible linkers would respond to pressure.…”

“…[9][10][11][12] Among the compounds synthesized were alkyl C 4 H 8 and C 6 H 12 diphosphonates of zinc. 11 Our purpose was to determine how a small pore MOF with flexible linkers would respond to pressure. This is in contrast to the earlier compression studies where the MOFs were highly porous and with rigid linkers.…”