A series of five unique d-f heteronuclear luminescent metal-organic frameworks (MOFs) in an entangled polyrotaxane array and the light-harvesting block homonuclear zinc compound have been isolated successfully and characterized. The series of isostructural polymers feature 3,4-connected (4.8)(4.8.9)(6.8.9)(6.9)(8) topology and high stability, exhibiting diverse void spaces. By taking advantage of the isostructural MOFs 2 and 3, the intensities of red and green emissions can be modulated by adjusting the ratios of Eu and Tb ions correspondingly, and white-light emission can be generated by a combination of different doped Tb and Eu concentrations. The Tb-Zn-based framework {[TbZn(bipy)(Hmimda) (HO)]·5HO} (3; Hmimda = 2-methyl-1-H-imidazole-4,5-dicarboxylic acid and bipy = 4,4'-bipyridine) can detect trace Mg ion with relatively high sensitivity and selectivity. Dehydrated MOF 3a shows a remarkable emission quenching effect through the introduction of I solids. Further investigation indicates that it exhibits turn on/off switchable properties for small solvent molecules or heavy-metal ions. Steady/transient-state near-IR luminescence properties for MOFs 1, 4, and 5 were investigated under visible-light excitation.
A family of heteronuclear metal organic frameworks (MOFs) using lanthanide and transition metal ion based on a rigid ligand of substituted imidazoledicarboxylic acid, namely, {[Ln2Zn2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·mn H2O}, Ln = Nd, m = 2 (1), Ln = Ho, m = 3 (2), Ln = Er, m = 2 (3), Ln = Yb, m = 3 (4), [Tb2Co2(μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·2nH2O} (5) and [Dy2Co2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·nH2O} (6), (H3mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid), have been developed and characterized. All the complexes (except for a little disparity for 1) are isostructural, and all crystallize in the monoclinic system. They possess an extended reticular-like porous structure constructed from corrugated 2D layers. Direct current (dc) magnetic susceptibility measurements for 1-5 indicated depopulation of the Stark components at low temperature and/or possible weak anti-ferromagnetic interactions within hetero-nuclear MOFs. Alternating current (ac) susceptibility studies reveal that the Dy(III)-Co(II) complex exhibits both possible ferromagnetic couplings and frequency-dependent out-of-phase signals, behaviour of single-ion magnet nature. Fluorescence properties of series complexes both in near-infrared (NIR) and visible regions have been comparatively studied.
A new zinc compound, together with a corresponding series of Zn-4f heterometallic coordination polymers, namely, [Zn(H2PBDA)(PBDA)]n (1), {[Ln2(PBDA)2·2H2O] [Zn2(PBDA)2Cl2]}n [H2PBDA = 3-(pyridin-3-yl-oxy) benzene-1,2-dicarboxylic acid, and Ln = Pr(2), Nd(3), Eu(4), Gd(5), Dy(6), Ho(7), Er(8)] have been hydrothermally synthesized and characterized systematically. Polymers 2-8 feature two-dimensional (2D) 4,4 networks, containing the original 1D heterometallic double stranded chains composed of [Ln2Zn2(PBDA)2] entities. The extensive hydrogen bonding and π-π stacking interactions were observed to stabilize the extended architectures. The luminescence emission spectra of the polymers vary depending on the lanthanide(III) ion present. Informative magnetic susceptibility measurements show that the same carboxylate bridging fashion of the PBDA ligand results in the different magnetic properties occurring within the heterometallic coordination polymers. In addition, polymer 6 exhibits an interesting slow magnetic relaxation behavior at lower temperatures.
A new 3-D open-framework cadmium borovanadate with 6-connected topology was hydrothermally obtained and structurally characterized. It not only features new cadmium(II) borovanadate which possesses an open-framework structure with unique plane-shaped channels, but also exhibits interesting absorption properties and high catalytic activities for the oxidation of cyclohexanol.
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