Assembly of multinuclear Ag complexes and Keggin polyoxometalates adjusted by organic ligands: syntheses, structures and luminescence

Two unusual α-Keggin-based compounds with multinuclear silver clusters, {[Ag7(H2biim)5][PW11O39]}·Cl·H3O (1) and {[Ag2(H2biim)2][Ag(phnz)](PW12O40)}·H2O (2) (H2biim = 2,2′-biimidazole, phnz = phenazine), have been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectra, thermogravimetric analysis and X-ray crystallography. Compound 1 displays a 2D network featuring dimerized monolacunary Keggin anions {PW11O39}2 which are connected together through pentanuclear silver clusters. Interestingly, besides {Ag5}5+ clusters, there are another kinds of argentophilic {Ag4}4+ clusters coexisting in compound 1. Compound 2 consists of four subunits: 1D cationic chains [Ag(phnz)]+, dinuclear silver-H2biim units [Ag2(H2biim)2]2+, discrete polyanions {PW12O40}3− and water molecules, which are further joined by hydrogen bonds to form a 3D supramolecular structure. The differences in the structures of compounds 1 and 2 indicate that the introduction of the secondary organic ligand plays a key role in determining the final structure. The electrochemical, electrocatalytic behaviors and luminescent properties of compounds 1 and 2 have also been investigated.