Lanthanide Germanate Cluster Organic Frameworks Based on {Ln8Ge12} Clusters: From One-Dimensional Chains to Two-Dimensional Layers and Three-Dimensional Frameworks.

Abstract

Under hydrothermal conditions, six series of novel lanthanide (Ln) organogermanates (LnGs) [Ln8Ge12(μ3-O)24E12(H2O)16]·14H2O (Ln(3+) = Pr(3+), 1; Nd(3+), 2; Sm(3+), 3; Eu(3+), 4; Gd(3+), 5; one-dimensional (1-D) LnG cluster organic chain (LnGCOC)), {[Nd8Ge12(μ3-O)24E12(H2O)10](μ2-H2O)2[Nd8Ge12(μ3-O)24E12(H2O)16]}·18H2O (6, two-dimensional (2-D) planar LnG cluster organic layer (LnGCOL)), {[Ln2GeE(HO)2O(H2O)(CH3COO)2(CO3)]2[Ln8Ge12E12(μ3-O)24(H2O)10]}·6H2O (Ln(3+) = Pr(3+), 7; Nd(3+), 8; 2-D wave-shaped LnGCOL), [TbGeE(HO)2O(H2O)(pca)]2[Tb8Ge12E12(μ3-O)24(H2O)8]·10H2O (9, three-dimensional (3-D) LnG cluster organic framework (LnGCOF)), {([Nd(pza)2(H2O)2]2[Nd8Ge12E12(μ3-O)24(H2O)12])([Nd(pza)2]2[Nd8Ge12E12(Hpza)2(μ3-O)24(H2O)10])}·4OH·14H2O (10, 3-D LnGCOF), {[Nd8Ge12E12(μ3-O)24(H2O)10][Nd(pca)(pda)(H2O)]2}·12H2O (11, 3-D LnGCOF) and {[Nd8Ge12E12(μ3-O)24(H2O)10][Nd(pza)(pda)(H2O)]2}·12H2O (12, 3-D LnGCOF) (Hpca = 2-picolinic acid, H2pda = 2,6-pyridinedicarboxylic acid, Hpza = 2-pyrazinecarboxylic acid) were prepared by introducing the second auxiliary ligands into the organogermanate-lanthanide-oxide reaction system. The obtainment of these LnGs realized the utilization of the second auxiliary ligands inducing the assembly from 1-D LnGCOCs to 2-D LnGCOLs and 3-D LnGCOFs based on LnG cluster (LnGC) {Ln8Ge12E12(μ3-O)24(H2O)16}({Ln8Ge12}) units and Ln-organic complexes or organic ligand connectors. It should be noted that the well-organized structural constructions of 1-12 can be visualized as the gradual replacement of active water sites located at equatorial and polar positions on the hypothetical [Ln8Ge12(μ3-O)24E12(H2O)18] LnGC core with oxygen or nitrogen atoms from organic ligands. The solid-state luminescent properties of 2, 3, 4, 6, and 8-12 have been investigated at room temperature.