American Chemical Society
cg0c01050_si_001.pdf (3.27 MB)

Isomerism in Benzenetricarboxylates: Variations in the Formation of Coordination Polymers with Uranyl Ion

Download (3.27 MB)
journal contribution
posted on 2020-09-30, 10:03 authored by Pierre Thuéry, Youssef Atoini, Jack Harrowfield
A series of uranyl ion complexes with fully or partially deprotonated 1,2,4-benzenetricarboxylic acid (H3btc) and involving either organic countercations or additional metal cations has been synthesized under solvo-hydrothermal conditions. The complexes [PPh4]­[UO2(btc)] (1) and [PPh4]2[(UO2)2(Hbtc)3]·H2O (2) crystallize as monoperiodic coordination polymers, while [PPh3Me]­[UO2(btc)]·H2O (3) is a diperiodic network with fes topology. Monoperiodic organization is also found in [H2DABCO]­[(UO2)2(btc)2]·2H2O (4) (DABCO = 1,4-diazabicyclo[2.2.2]­octane), but [Hquin]2[(UO2)5(btc)4]·2H2O (5) (quin = quinuclidine) is a triperiodic framework. Incorporation of azamacrocyclic complexes of d-block metal cations gives [(UO2)2(btc)2Ni­(cyclam)] (6) and [(UO2)2(btc)2Cu­(R,S-Me6cyclam)] (7) (cyclam = 1,4,8,11-tetraazacyclotetradecane, R,S-Me6cyclam = 7­(R),14­(S)-5,5,7,12,12,14-hexamethylcyclam), two diperiodic networks with the same V2O5 topology, but differing in the diaxial bonding of the 3d metal cation, either to uranyl oxo groups or to carboxylato groups, respectively. Triperiodic polymerization occurs in [UO2Ag2(Hbtc)2(H2O)2] (8) and [(UO2)2Ag2(btc)2(CH3CN)1.5(H2O)0.43]· 1.5H2O (9), with both oxo and carboxylato bonding of the bridging silver­(I) cations. The isomorphous complexes [UO2Rb­(btc)­(H2O)] (10) and [UO2Cs­(btc)­(H2O)] (11) also crystallize as triperiodic frameworks with bonding of the alkali metal cations to oxo and carboxylato groups. In 10 and 11, uranyl cations and btc3– ligands alone give a 2-fold interpenetrated triperiodic framework with utp topology. Emission spectra in the solid state display the usual vibronic fine structure for 15, 10, and 11, while uranyl emission is quenched in 7. Photoluminescence quantum yields range from 1.3 to 17.4%, less than that for solid UO2(NO3)2·6H2O, except for 1 which has the unusually large value of 35%. Comparisons are drawn with previous studies of uranyl ion complexes of all known benzenetricarboxylate isomers.