Self-assembly between Ag+ and [PW11NbO40]4- in N- and O-donor solvents (nitriles and amides) has been studied. In the case of dimethylformamide (DMF), formation of a yellow [Ag4(DMF)12][PW11NbO40] (1a) metastable phase and a colorless [Ag4(DMF)10][PW11NbO40] (1) stable phase was observed. In acetonitrile (CH3CN), the product was [Ag(CH3CN)4]2{[Ag(CH3CN)3]2[PW11NbO40]} (2a). By contrast, [SiW12O40]4- of the same size and charge as [PW11NbO40]4- produces [Ag(CH3CN)3]4[SiW12O40] (3a). Partial desolvation of 2a and 3a leads to Ag4[PW11NbO40]·7.5CH3CN (2) and Ag4[SiW12O40]·7.5CH3CN (3), respectively. The CH3CN molecules in the structure of 2 are labile, and this compound was used as the starting material to study solvent-exchange processes in N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMA), diethylformamide (DEF), and benzonitrile (PhCN) solutions. These solvent reactions yield [Ag(DMA)4][Ag3(DMA)6][PW11NbO40] (4), [Ag2(NMP)4(CH3CN)]2[PW11NbO40]·1.3NMP (5a), [Ag2(NMP)5]2[PW11NbO40] (5b), Ag4[PW11NbO40]·9.5DEF (6), and [Ag(PhCN)4]2[{Ag(PhCN)3}2PW11NbO40] (7). All products were isolated and characterized by single-crystal X-ray diffraction (except for 2 and 3), IR, elemental analysis, and thermogravimetric analysis techniques. The O-donor solvents favor polynuclear, solvent-bridged cationic aggregates. In the case of DMF, DMA, and DEF discrete, tri- and tetranuclear polycations are observed, while in the case of NMP, the formation of infinite polycationic structures takes place. By contrast, the N-donor solvents (CH3CN and PhCN) favor mononuclear cations, which can exist either as distorted tetrahedral, isolated [Ag(Solv)4]+ cations or as pseudotriangular {Ag(Solv)3}+ units, additionally coordinated to a polyoxometalate. Screening of the luminescent properties for solid samples of 1-7 revealed that only 5a/5b and 7 are emissive. In particular, the sample containing 5a and 5b demonstrates long-lived phosphorescence with a 30 ms lifetime.