Large Pore Isoreticular Strontium-Organic Frameworks: Syntheses, Crystal Structures, and Thermal and Luminescent Properties
Two isoreticular and topologically unique metal-organic frameworks (MOFs) have been synthesized using Sr(NO3)2 and the organic linkers 2-nitro-[1,1′-biphenyl]-4,4′-dicarboxylic acid (H2bpdcNO2) and 2,2′-dinitro-[1,1′-biphenyl]-4,4′-dicarboxylic acid (H2bpdc(NO2)2). The structures of [Sr(bpdcNO2)2(DMF)2(H2O)2] (WUF-15; WUF = Wollongong University Framework) and [Sr4(bpdc(NO2)2)4(DMF)2(H2O)4·2DMF] (WUF-16) were determined by single crystal X-ray diffraction (SCXRD) and are composed of infinite strontium carboxylate SBUs and contain large square (∼18 Å) and smaller triangular channels (∼9 Å) orientated parallel to each other and lined with nitro functional groups. An in situ ligand transformation of H2bpdc(NO2)2 to benzo[c]cinnoline-3,8-dicarboxylic acid (H2bc) and formation of a nonporous coordination polymer of formula [Sr(bc)(H2O)2] (WUF-17) with interesting photoluminescent properties was discovered. Independent synthesis of H2bc enabled the preparation of WUF-17 crystals suitable for SCXRD structure determination. Powder X-ray diffraction and thermal and elemental analyses support the structures of all complexes.