Syntheses, structures and photocatalytic properties of five new praseodymium–antimony oxochlorides: from discrete clusters to 3D inorganic–organic hybrid racemic compounds

Abstract

Five novel praseodymium–antimony oxochloride (Pr–Sb–O–Cl) cluster-based compounds, namely (2-MepyH)₂[Fe(1,10-phen)₃]₂[Pr₄Sb₁₂O₁₈Cl_14.6(OH)_2.4(Hsal)]·H₂O (1), (2-MepyH)₂[Fe(1,10-phen)₃]₄{[Pr₄Sb₁₂O₁₈Cl_13.5(OH)_0.5](bcpb)₂[Pr₄Sb₁₂O₁₈Cl_13.5(OH)_0.5]}·42H₂O (2), (3-MepyH)₂[Fe(1,10-phen)₃]{[Pr₄Sb₁₂O₁₈Cl₁₃(H₂O)₂](bcpb)}·2(3-Mepy)·3H₂O (3), [Fe(1,10-phen)₃]₂{[Pr₄Sb₁₂O₁₈Cl₁₀(H₂O)₂](bcpb)₂}·3(3-Mepy)·13H₂O (4), and (2-MepyH)₆[Fe(1,10-phen)₃]₁₀{[Pr₄Sb₁₂O₁₈Cl₁₃(OH)₂]₂[Pr₄Sb₁₂O₁₈Cl₉][Pr₄Sb₁₂O₁₈Cl₉(OH)₂]₂(Hpdc)₁₀(pdc)₂}·110H₂O (5) (2-Mepy = 2-methylpyridine, 3-Mepy = 3-methylpyridine, 1,10-phen = 1,10-phenanthroline, H₂sal = salicylic acid, H₃bcpb = 3,5-bis(4-carboxyphenoxy)benzoic acid, H₃pdc = 3,5-pyrazoledicarboxylic acid) have been solvothermally synthesized and structurally characterized. Compound 1 is the first zero-dimensional (0D) Pr–Sb–O–Cl cluster decorated by an organic ligand. Compounds 2–4 are constructed from the same H₃bcpb ligands but adopt different structures: 2 represents a rare example of a one-dimensional (1D) nanotubular structure based on high-nuclearity clusters; 3 exhibits a two-dimensional (2D) mono-layered structure, in which left-handed and right-handed helical chains are alternately arranged, while 4 features a double-layered structure with an unprecedented (3,3,6)-connected 3-nodal topological net. Compound 5 is a unique three-dimensional (3D) 2-fold interpenetrating racemic compound, simultaneously containing three kinds of Pr–Sb–O–Cl–pdc clusters. UV-light photocatalytic H₂ evolution activity was observed for compound 3 with Pt as a co-catalyst and MeOH as a sacrificial electron donor. In addition, the magnetic properties of compounds 1 and 5 are also studied.