Polyoxometallate–Thiosemicarbazone Hybrid Compounds

Abstract

AbstractNew polyoxometallate–thiosemicarbazone hybrid compounds derived from pyridine‐2‐carbaldehyde thiosemicarbazone (HL), pyridine‐2‐carbaldehyde N4‐methylthiosemicarbazone (HL′) and their copper(II) complexes have been synthesized. Their formulae are (H2L)4(Mo8O26)(H2O)4 (1), [{(HL)2H}2(Mo6O19)]·C3H6O·0.24H2O (2), [(H2L′)4(HL′)2(Mo8O26)(H2O)2] (3), [{Cu(L)}4(Mo8O26)(H2O)4] (4), [{Cu(HL)(H2O)}2(Mo8O26)] (5), [{Cu(L′)}4(Mo8O26)(H2O)14] (6), Na6[{Cu(HL′)(H2O)2}4({Cu(L′)}2{Mo36O116(H2O)12})]·20H2O (7), [{Cu(HL)}2{Cu(L)}4{Mo36O112(H2O)16}(H2O)26] (8), [{Cu(HL′)}4{Mo36O112(H2O)16}(H2O)30] (9) and [{Cu(HL)(H2O)}2{Cu(L)S}2(H4V10O28)]n·6nH2O (10). Compounds 1–6 contain octamolybdate [Mo8O26]4– or hexamolybdate [Mo6O19]2– anions together with (H2L)+, (H2L′)+, [Cu(L)]+, [Cu(HL)(H2O)]2+ or [Cu(L′)]+ cations and neutral thiosemicarbazone molecules. The polyoxometallates (POMs) in 7–9 are [Mo36O116(H2O)12]16–, {Mo36} (7), and [Mo36O112(H2O)16]8–, {Mo36′} (8, 9). [Cu(HL′)]2+/[Cu(L′)]+ and [Cu(HL)]2+/[Cu(L)]+ units complete the respective lattices. Compound 10 consists of decavanadate anions (H4V10O28)2– and thiosemicarbazone‐copper(II) entities forming 1D [{Cu(HL)(H2O)}2{Cu(L)S}2(H4V10O28)]n structures connected through the hydrogen bonds of chains of water molecules. Structures of 2, 5, 7 and 10 have been characterized by single‐crystal X‐ray diffraction and other instrumental techniques (infrared, thermal analysis, electron paramagnetic resonance, nuclear magnetic resonance, magnetic susceptibility and mass spectrometry) were used to analyse all the compounds presented herein. The structural parameters of more than 1000 published thiosemicarbazone‐metal complexes have been used to determine some of the differences between metal complexes that contain anionic and neutral thiosemicarbazone ligands.