Abstract
A series of decavanadate based compounds, formulated as [Co(H2O)6][{Na4(H2O)14}{V10O28}]·4H2O (1), [Zn(H2O)6][Na3(H2O)14] [HV10O28]·4H2O (2), [HMTAH]2 [{Zn(H2O)4}2{V10O28}]·2H2O (3), [{Co(3-amp)(H2O)5}]2 [3-ampH]2 [V10O28] · 6H2O (4), [4-ampH]10[{Na(H2O)6}{HV10O28}][V10O28]·15H2O (5), [{4-ampH}6 {Co(H2O)6}3][V10O28]2·14H2O (6), and [{4-ampH}10{Zn(H2O)6}][V10O28]2·10H2O (7), have been synthesized (where HMTAH = mono-protonated hexamethylenetetramine, 3-ampH = protonated 3-amino pyridine and 4-ampH= protonated 4-aminopyridine) from the relevant aqueous sodium-vanadate solution, by varying the pH of the solution and amino pyridine/hexamine derivatives as well as transition metal salts (Co(II)- and Zn(II)-salts). In this series of compounds 1–7, the polyoxovanadate (POV) cluster [V10O28]6− is the common cluster anion, stabilized by diverse cations. The diverse supramolecular patterns around the decavanadate cluster anion in different cationic matrices have been described to understand the microenvironment in the decavanadate-based minerals. All of these compounds have solvent water molecules in their respective crystal lattices. Since water can interact directly with cations and anions, providing an additional stability and structural diversity, we have analyzed supramolecular water structures in all these compounds to comprehend the role of the lattice water in the formation of natural decavanadate containing minerals. Compounds 1–7, that are isolated at an ambient condition from aqueous solution, are characterized by routine spectral analysis, elemental analyses and finally unambiguously by single crystal X-ray crystallography.
Highlights
Numerious decavanadate based compounds are known in literature (Crans et al, 2017; Naslhajian et al, 2017; Yerra and Das, 2017) where the decavanadate cluster anion has been isolated using diverse cations including transition metal- and alkali metal-coordination complex cations; relevant supramolecular chemistry has been described in the context of POV based materials chemistry (Sánchez-Lombardo et al, 2014; Wang et al, 2016)
We have described the synthesis and characterization of seven decavanadate containing compounds [Co(H2O)6] [{Na4(H2O)14} {V10O28}] ·4H2O (1), [Zn(H2O)6] [Na3(H2O)14] [HV10O28] ·4H2O (2), [HMTAH]2[{Zn(H2O) 4}2{V10O28}] ·2H2O (3), [{Co(3-amp)(H2O)5} 2{3-ampH}2] [V10O28] ·6H2O (4), [4-ampH]10[{Na(H2O)6} {HV10O28}] [V10O28] ·15H2O (5), [{4-ampH}6 {Co(H2O)6}3] [V10O28]2·14H2O (6), [{4-ampH}10 {Zn(H2O)6}] [V10O28]2 ·10H2O (7)
In some of their crystal structures, non-covalent interactions among the lattice water molecules and metal coordinated water molecules lead to the formation of supramolecular water clusters
Summary
The modern chemical research on polyoxometalates (POMs)-based solid state materials fascinates synthetic chemists because of their potential applications in diverse research areas, such as, catalysis (Vazylyev et al, 2005; Hill, 2007; Zhou et al, 2014; Lechner et al, 2016; Mukhopadhyay et al, 2018), medicinal chemistry (Pope and Müller, 1991; Liu et al, 2012; Xie et al, 2018), and materials science (Guo et al, 2000; Rao et al, 2011; Kulikov and Meyer, 2013; Omwoma et al, 2015; Walsh et al, 2016). The metal salt, Co(NO3)2·6H2O (0.5 g, 1.7 mmol) was dissolved in 20 mL of water This reaction mixture of metal salt was added drop wise to the sodium vanadate solution with stirring. The Zn(NO3)2·6H2O and hexamine (0.25 g, 1.68 mmol) were dissolved in 20 mL of water This reaction mixture was added drop wise to the sodium vanadate solution with stirring. The Co(NO3)2·6H2O (0.5 g, 1.7 mmol) and 3-aminopyridine (0.25 g, 1.68) were dissolved in 20 mL of water The resulting reaction mixture was stirred for 5 h
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