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Interpenetrated Uranyl–Organic Frameworks with bor and pts Topology: Structure, Spectroscopy, and Computation

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journal contribution
posted on 01.11.2017, 19:20 by Chao Liu, Fang-Yuan Chen, Hong-Rui Tian, Jing Ai, Weiting Yang, Qing-Jiang Pan, Zhong-Ming Sun
Two novel three-dimensional interpenetrated uranyl–organic frameworks, (NH4)4[(UO2)4(L1)3]·6H2O (1) and [(UO2)2(H2O)2L2]·2H2O (2), where L1 = tetrakis­(3-carboxyphenyl)silicon and L2 = tetrakis­(4-carboxyphenyl)­silicon, were synthesized by a combination of two isomeric tetrahedral silicon-centered ligands with 3-connected triangular [(UO2)­(COO)3] and 4-connected dinuclear [(UO2)2(COO)4] units, respectively. Structural analyses indicate that 1 possesses a 2-fold interpenetrating anion bor network, while 2 exhibits a 3-fold interpenetrated 4,4-connected neutral network with pts topology. Both compounds were characterized by thermogravimetric analysis and IR, UV–vis, and photoluminescence spectroscopy. A relativistic density functional theory (DFT) investigation on 10 model compounds of 1 and 2 shows good agreement of the structural parameters, stretching vibrational frequencies, and absorption with experimental results; the time-dependent DFT calculations unravel that low-energy absorption bands originate from ligand-to-uranium charge transfer.