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

Under hydrothermal conditions, six series of novel lanthanide (Ln) organogermanates (LnGs) [Ln8Ge12(μ3-O)24E12­(H2O)16]­·14H2O (Ln3+ = Pr3+, 1; Nd3+, 2; Sm3+, 3; Eu3+, 4; Gd3+, 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 (Ln3+ = Pr3+, 7; Nd3+, 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.