The syntheses, structures, and N2 adsorption properties of six new supramolecular metallacycles are reported. Flexible ditopic linkers, 1-4, with systematically varied lengths and conformational degrees of freedom were synthesized utilizing ester linkages. They were used in combination with (dppp)M(OTf)2, where M = Pt(II) and Pd(II), and cis-(Me3P)2Pt(OTf)2 to form flexible supramolecular metallacycles 5-10 in 88-98% isolated yields. Their structures were characterized via multinuclear NMR and X-ray crystallography. The metallacycles stack to form porous structures in the crystalline state. The pore dimensions depend on both the phosphorus ligands attached to the metals and the flexible linkers. Adsorption studies on the porous materials show that 5a, 6, 8, and 9 held 11.7, 16.5, 5.7, and 6.8 cm3/g STP of N2 at 77 K, respectively. A guest-exchange study with nitromethane and toluene reveals that the nanopore in 5 is flexible, a property which was transferred from the linker to the supramolecular structure in the solid state.
We report the formation of two thermally stable supramolecular structures based on 2,6-pyridyldicarboxylic acid bis-4-pyridylamide (PyI) and bis(hexafluoroacetylacetonato)manganese(II) that exhibits a microporous structure with cavities bearing hydrogen bonding motifs that can enclathrate acetone and methanol molecules via well-positioned hydrogen bonding interactions. Single-crystal x-ray diffraction in combination with thermogravimetric analysis and X-ray powder diffraction (XRPD) studies were utilized to study the structure and thermal behavior of trans-[Mn(hfacac) 2 (PyI) 2 ] Á 2(CH 3 ) 2 CO (1) and trans-[Mn(hfacac) 2 (PyI) 2 ] Á 2CH 3 OH (2). Our studies indicated that 1 and 2 are isostructural with respect to their supramolecular assembly and trap solvent molecules along the crystallographic b direction via the inwardly directed hydrogen bonding motifs of the PyI component. These solvent molecules can be thermally removed to generate a crystalline material with micropores bearing hydrogen bonding rich sites within an overall supramolecular matrix similar to 1 and 2. The removal of the guest solvent molecules is reversible and can be followed with XRPD. Plate 1. Crystal lattice of 1 as seen from the crystallographic b direction Plate 2. p±p stacking of 1 and 2. (a) View from b direction; (b) and (c) two types of p±p stacking interaction between the PyI groups 16: 420-425 THERMALLY STABLE POROUS SUPRAMOLECULAR FRAMEWORKS 423 Plate 3. Representation of the van der Waals surfaces of the H-bonding rich pocket formed by two groups of PyI in 1 and 2 Plate 4. TGA and XRDP patterns of (a) 1 and (b) 2. (c) XRDP pattern after removal of guest acetone and methanol molecules from the structures of 1 or 2. (d) Microscopy image of crystals of 1 before (left) and after desolvation (right)
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