Counterion-Controlled Formation of Layered Honeycomb and Polythreading Uranyl Networks and the Highly Sensitive and Selective Detection of Fe3+ in Aqueous Media

Under hydrothermal conditions, six uranium coordination polymers were obtained by employing the ligand of tris(2-carboxyethyl) isocyanurate (H 3 tci) and different combinations of d-block metal ions (Mn 2+, Co 2+, Zn 2+, Ni 2+ ) or N-donors (triethylamine (Et 3 N), 2,2′-bipyridine (2,2′-bipy)). Three uranium polymers [(UO 2 ) 2 (tci) 2 ] 1/2 – ·[Mn 2 (μ 2 -O)(H 2 O) 8 ] 1/2 + ·2H 2 O ( 1 ), [(UO 2 ) 2 (tci) 2 ] 1/2 – ·[Co 2 (μ 2 -O)(H 2 O) 8 ] 1/2 + ( 2 ), and [(UO 2 ) 2 (tci) 2 ] 1/2 – ·[Zn 2 (μ 2 -O)(H 2 O) 8 ] 1/2 + ·2H 2 O ( 3 ) containing transition metal hydrated ions, crystallized as two-dimensional coordination polymers with the common (6, 3) net topology. X-ray crystal structures of 1 – 3 display that they have similar honeycomb-like frameworks with all ligands bis-chelating. [UO 2 (tci)] − 3 ·[Ni(H 2 O) 6 ] 2+ (H 3 O) + ·2H 2 O ( 4 ) and [UO 2 (tci)] − ·[NH(CH 2 CH 3 ) 3 ] 1/3 + ·(2H 3 O + ) 1/3 ( 5 ) are made up of four interlocked sets and exhibit the 4-fold-interpenetrated frameworks. [UO 2 (tci)] − ·(C 10 H 9 N 2 ) + ·H 2 O ( 6 ) comprises the 2,2′-bipy cation as counterion and represents a 2D grid layered structure. Additional metals and the N-donors are all free in the complexes, acting as the templates and compensation of the charge equilibrium. The solid-state emission spectra indicate that all of the synthesized compounds own fluorescence emissions. Furthermore, the results of the quenching ability of Fe 3+ for complexes 5 and 6 exhibit their highly sensitive and selective detection for Fe 3+ ions. Moreover, the uranium complexes can be used as a potential probe for Fe 3+ in aqueous solutions.