Structural Diversity and Vibrational Spectra of Nine Cu(I)-Cyanide Metal-Organic Frameworks with in Situ Generated N-Heterocyclic Ligands.

Nine Cu(I)-cyanide metal-organic frameworks (MOFs), namely, [Cu4(CN)2(4-bpt)2]n (1), {[Cu3(CN)2(4-bpt)]·H2O}n (2), [Cu2(CN)(3-bpt)]n (3), [Cu2(CN)2(3-Hptz)]n (4), [Cu3(CN)2(3-ptz)]n (5), [Cu7(CN)7(3-tpt)2]n (6), {[Cu9(CN)9(btb)2]·btb}n (7), [Cu2(CN)2(4-azpy)]n (8), and [Cu3(CN)3(bpp)]n (9) (4/3-Hbpt = 3,5-bis(4/3-pyridyl)-1,2,4-triazole; 3-Hptz = 3-pyridyl-tetrazole; 3-tpt = 2,4,6-tris(3-pyridyl)-1,3,5-triazine; btb = 1,4-bis(1,2,4-triazol-4-yl)benzene; 4-azpy = 4,4'-azobispyridine; bpp = 1,3-bis(4-pyridyl)propane), were synthesized under hydrothermal conditions and structurally characterized. The 4-bpt, 3-bpt, and 3-Hptz ligands in 1-4 were in situ generated by cycloaddition reactions. Their structural features vary from two-dimensional (2D) (3), three-dimensional (3D) (4, 5, 6), 3D 2-fold interpenetration (1, 2, 8), to 3D 3-fold interpenetration (7, 9). Complex 1 is an intriguing 3D metal-organic framework (MOF) with a nanosized rectangular channel. Complex 3 exhibits a chiral 2D double-layered network prepared by achiral component. Complex 6 is a 3D MOF constructed from six μ2-cyanides, a μ3-cyanide, and a μ3-tpt ligand. Complex 7 shows an interesting 3D MOF with (3.4)-connected 5-nodal net, containing a btb guest molecule in the rectangular channel. Complex 8 is a 3D MOF assembled by a 2D [Cu2(CN)2]n network pillared by a 4-azpy spacer. Complex 9 is a 3D MOF with ths topology. Their structural diversity originates from the variation of Cu(I) coordination numbers and three types of cyanide-bridging modes, tuned via various bidentate (4-azpy, bpp), tridentate (3-Hptz, 3-tpt), and tetradentate (4-bpt, 3-bpt, 3-ptz, btb) N-heterocyclic ligands. Infrared spectra and cyanide coordination modes are discussed in detail. The characteristic ν(C≡N) stretching frequencies in μ2-CN complexes show linear correlation with the Cu-CN bond distances. A decrease of about 6.7 cm-1 in ν(C≡N) corresponds to a 0.01 Å elongation of the Cu-CN bond. These Cu(I) complexes exhibit good thermally stability and emit strong luminescence at 386-593 nm. [ABSTRACT FROM AUTHOR]