Structures and luminescent properties of new uranyl-based hybrid materials

Abstract

Six uranyl coordination compounds, UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)·2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) were grown as single crystals via hydrothermal synthesis (PYCA = pyrazine-2-carboxylate, PIC = picolinate, NIC = nicotinate, INIC = isonicotinate, and PYTAC = 2-(pyridin-4-yl)thiazole-5-carboxylate) to study their optical properties. All six compounds have been identified via single crystal X-ray diffraction and fully characterized via powder X-ray diffraction, infrared spectroscopy, UV–Vis spectroscopy, and fluorescence spectroscopy. Three of the complexes, 1, 3, and 6, represent new structures, and their synthesis and structural characterization is detailed within. The structures of 2, 4, and 5 have previously been reported in the literature. Coordination polymer 1 crystallizes in the orthorhombic space group Pca21 ( a = 13.5476(5) Å, b = 6.6047(2) Å, c = 8.3458(3) Å), and forms infinite 1-D chains of corner-sharing uranium polyhedra connected into 2-D layers by bridging ligands. Coordination polymer 3 crystallizes in the monoclinic space group Cc ( a = 8.4646(8) Å, b = 13.0357(11) Å, c = 11.8955(10) Å, β = 96.815(2)°), and forms ligand-bridged 1-D chains. Complex 6 crystallizes in the triclinic space group P-1 ( a = 5.6272(7) Å, b = 8.9568(10) Å, c = 10.4673(12) Å, α = 90.508(2)°, β = 104.194(2)°, γ = 91.891(2)°), and consists of isolated uranyl complexes connected via hydrogen bonds. The structures and luminescent properties of UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)·2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) are discussed.