All the starting reagents zinc hexafluorosilicate hydrate, (1E
)-1,2-bis(pyridin-4-ylmethylene)hydrazine were purchased from Sigma-Aldrich, Bangalore Karnataka, India and all the solvents were procured locally. Powder X-ray diffraction (PXRD) patterns were measured on Bruker D8 Advanced X-ray diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) at room temperature using Cu-Kα radiation (λ = 1.5406 Å) with a scan speed of 0.5° min–1
and a step size of 0.01° in 2 theta
. Thermogravimetric analysis results were obtained in the temperature range of 30–800 °C on Perkin-Elmer STA 6000 analyzer (TGA, STA 6000 Perkin Elmer, PerkinElmer, Inc., Waltham, MA, USA) under N2
atmosphere, at a heating rate of 10 °C min−1
. Single-crystal X-ray data of IPM-325_P1 was collected at 100 K on a Bruker KAPPA APEX II CCD Duo diffractometer (operated at 1500 W power: 50 kV, 30 mA, Bruker AXS GmbH, Karlsruhe, Germany) using graphite-monochromated Mo Kα adiation (λ = 0.71073 Å). A crystal was mounted on a nylon Cryoloop (Hampton Research) with Paraton-N oil (Hampton Research). The data integration and reduction were processed with SAINT software [29
]. A multi-scan absorption correction was applied to the collected reflections [30
]. The structure was solved by the direct method using SHELXS-2014 [31
] and was refined on F2
by full-matrix least-squares technique using the SHELXL-2017 [32
] program package within the WINGX program [33
]. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were located in successive difference Fourier maps and they were treated as riding atoms using SHELXL default parameters. Highly disordered guest solvent molecules were observed. SQUEEZE option was used that eliminate the contribution of disordered guest molecules [34
]. Residual electron density was calculated from the SQUEEZE function 49 electrons/unit cell. Gas adsorption measurements were performed using BelSorp-Max instrument (BEL Japan, Inc., Osaka, Japan).
Synthesis of Linker L ((1E
)-1,2-bis(pyridin-4-ylmethylene)hydrazine): Linker L was synthesized by modifying a reported protocol [35
]. 4-pyridinecarboxaldehyde (49.94 mmol, 4.704 mL) was taken in a round bottomed flask. To this flask (1:1) Methanol (15 mL) and ethanol (15 mL) solution was added and catalytic quantity of acetic acid was added to this mixture. This mixture was stirred at 120 °C for 0.5 h. Further, hydrazine hydrate (19.97 mmol, 0.970 mL) was added and the reaction was maintained at 120 °C for 12 h. Subsequent cooling to room temperature yielded yellow crystalline product. Crude product was recrystallized from a solvent combination of methanol: ethanol solvent mixture. Yield = 90%.
Synthesis of IPM-325_p1: Single crystals of IPM-325_p1 were obtained by slow diffusion 1:1 mixture of zinc hexafluorosilicate hydrate (ZnSiF6, H2O) (0.1 mmol, 20.7 mg) and L = (1E,2E)-1,2-bis(pyridin-4-ylmethylene)hydrazine (0.1 mmol, 21 mg) in a solvent combination of Dichloromethane, methanol and benzene. Block shaped yellow colored crystal was obtained after one week. Yield ~60%.
Desolvated phase preparation: IPM-325_p1 was heated at 160 °C overnight with slow increase in the temperature at the rate of 5 °C/h and then maintaining 160 °C overnight. The desolvated phase was further characterized by thermogravimetric analysis.