Silver Pyroarsonates Obtained from Ag(I)-Mediated in Situ Condensation of Aryl Arsonate Ligands under Solvothermal Conditions

Four new layered silver(I) organoarsonates, namely, [Ag3(L3)(CN)] (1) (H2L3 = (PhAsO2H)2O), [Ag3(L4)(CN)] (2) (H2L4 = (2-NO2-C6H4-AsO2H)2O), [Ag3(HL5)(H2L5)] (3) (H3L5 = 3-NO2-4-OH-C6H3-AsO3H2) and [Ag2(HL5)] (4), were synthesized under solvothermal conditions. During the preparations of 1 and 2, condensation of organoarsonate ligands (H2L1 = Ph-AsO3H2; H2L2 = 2-NO2-C6H4-AsO3H2) and the decomposition of acetonitrile molecules to cyanide anions occurred. Single crystals of H2L4 ligand and compounds 1–4 were isolated, and their crystal structures have been determined by single crystal X-ray diffraction studies. In 1, the one-dimensional (1D) chains based on Ag(I) ions and {L3}2– anions are further interconnected by CN– into two-dimensional (2D) layers. In 2, adjacent Ag(I) ions within the silver(I) organoarsonate layer are further bridged by μ4-CN– anions with very short Ag···Ag contacts. In 3, the hexanuclear {Ag6O12} clusters are interconnected by bridging organoarsonate ligands into a silver(I) arsonate hybrid layer. In 4, the right-handed {Ag4O4} chains are further interconnected by organoarsonate ligands as well as additional Ag–O–Ag bridges into a novel silver(I) arsonate layer. Compounds 1 and 2 display red and orange-red emissions, respectively, which may be assigned to be an admixture of ligand-to-metal charge transfer (LMCT) and metal-centered (4d-5s/5p) transitions perturbed by Ag(I)···Ag(I) interactions. Upon cooling from room temperature to 10 K, compound 1 exhibits interesting temperature-dependent emissions.