Pb4V6O16(SeO3)3(H2O), Pb2VO2(SeO3)2Cl, and PbVO2(SeO3)F: New Lead(II)–Vanadium(V) Mixed-Metal Selenites Featuring Novel Anionic Skeletons

Hydrothermal reactions of PbCO3 (or PbCl2), V2O5, and SeO2 in KOH solution or HF solution resulted in three new lead­(II)–vanadium­(V) mixed-metal selenites, namely, Pb4V6O16(SeO3)3(H2O) (1), Pb2VO2(SeO3)2Cl (2), and PbVO2(SeO3)F (3). Compounds 1 and 2 are polar (space group P21), whereas compound 3 is centrosymmetric (space group Pbca). Compound 1 displays an unusual [V6O16(SeO3)3]8– anionic chain, which is composed by a 1D [V4O12]2– anionic chain that is further decorated by dimeric [V2O6(SeO3)3]8– units via corner-sharing. Compound 2 features two types of 1D chains, a cationic [Pb2Cl]3+ chain and a [VO2(SeO3)2]3– anionic chain, whereas compound 3 contains dimeric [V2O4(SeO3)2F2]2– units. The powder second-harmonic-generating (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.2 × KDP (KH2PO4) under 1400 nm laser radiation. Thermal stability and optical properties as well as theoretical calculations based on density functional theory methods were also performed.