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The reactions of 2,2′-bipyridyl-3,3′-dicarboxylic acid (H2bpdc) and 1,10-phenanthroline (phen) with lanthanide (III) salts in different concentrations under hydrothermal conditions formed two series of supramolecular isomers of 1D zigzag chains of [Ln(bpdc)1.5(phen)(H2O)]n·3nH2O (1Ln·3H2O), and 2D frameworks of [Ln(bpdc)1.5(phen)(H2O)]n (2Ln), (Ln = Ho, Er, Tm, and Yb). At lower concentrations, the supramolecular isomers of 1Ln were formed, in which each isomer has a dinuclear centrosymmetric dimeric unit of [Ln2(phen)2(H2O)2(μ2-bpdc)2]2+, and the dimeric units are alternately connected by μ2-bpdc2− to form a 1D zigzag chain of 1Ln. At higher concentrations, the supramolecular isomers of 2Ln were formed. All the compounds of 2Ln are isomorphous, in which two μ3-bpdc2− bridge two [Ln(phen)(H2O)]3+ units to yield a 1D double-chains of [Ln2(phen)2(H2O)2(bpdc)2]n2n+, and [Ln2(phen)2(H2O)2(bpdc)2]n2n+ chains are further connected by μ4-bpdc2− to form a 2D network of [Ln(bpdc)1.5(phen)(H2O)]n. The 2D sheets are combined through the intersheet π–π interactions between the adjacent phen molecules to form a 3D structure of 2Ln. The compounds of Er(III), and Yb(III) exhibit corresponding characteristic photoluminescence in the near-infrared (NIR) region, in which 1Ln and 2Ln show obviously different emission intensity due to their different structures. |
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