Two simple pathways using metallic copper or copper salts are proposed for the synthesis of hybrid compounds under mild conditions. A variety of Strandberg-and mixedmetal Keggin-based products, namely, (NH 4 ) 5n {[Cu(en) 2 ]-[PMo 8 V 4 O 40 ]} n ·9nH 2 O (1), (NH 4 ) 4n {[Cu(en)(H 2 O)][P 2 Mo 5 O 23 ]} n · 3.5nH 2 O (2), (NH 4 ) 7 [PMo 8 V 4 O 40 ]·17H 2 O (3) and (NH 4 ) 2n -{[Cu(en) 2 ][Cu(en)(H 2 O)][P 2 Mo 5 O 23 ]} n ·3nH 2 O (4), were isolated upon the variation of the composition of the reaction system. A rare four-substituted [PMo 8 V 4 O 40 ] 7-Keggin anion was obtained. The influence of the vanadium source [V 2 O 5 , NH 4 VO 3 or [a]
A one-pot reaction of a copper source (metallic powder Cu 0 or Cu 2+ salts) and bpy (bpy = 2,2′-bipyridine) in the presence of (NH 4 ) 2 HPO 4 and (NH 4 ) 6 Mo 7 O 24 •4H 2 O yields heterometallic hybrid compounds of the general type {[Cu-(bpy) n (H 2 O) m ] p [P 2 Mo x O y ]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P 2 Mo 5 O 23 ] 6− but also its unprecedented biand trilacunary derivatives [P 2 Mo 3 O 18 ] 8− and [P 2 Mo 2 O 15 ] 8− . The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different Cu II complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1−3 indicate rather strong antiferromagnetic metal−metal exchange interactions. Compound 1 exhibits fieldinduced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.
A number of new POM-based coordination polymers, including two-dimensional (NH 4 ) 4 {[Ca(H 2 O) 5 ][P 2 Mo 5 O 23 ]}· 3H 2 O (4) (bpy = 2,2′-bipyridine), and a rare anion-based (NH 4 ) 5 [Co III (bpy) 3 ]{[Ca(H 2 O) 4 ] 2 [Ca(H 2 O)] 6 [PMo 6 O 22 (PO 4 ) 3 ] 2 }· 17H 2 O (3), as well as three-dimensional (NH 4 ) 8 [Co III (bpy) 3 ] 2 -{[Ca(H 2 O) 3 ] 2 [P 2 Mo 5 O 23 ] 3 }·21H 2 O (2) have been prepared using a facile wet-chemistry approach and have been characterized by X-ray diffraction analysis and a variety of physicochemical methods. The self-assembly in the above compounds has been rendered by the use of Ca 2+ ions as a suitable linker in the [a] 3525 network formation. Moreover, Ca 2+ ions were also involved in the formation of an extremely rare type of POM anion {[Ca(H 2 O)] 6 [PMo 6 O 22 (PO 4 ) 3 ] 2 } 12-. The synthesis attempt without the alkaline-earth metal led, predictably, to the formation of the discrete Strandberg-based compound (NH 4 ) 3 [Co III (bpy) 3 ]-[P 2 Mo 5 O 23 ]·14H 2 O (1). Thus, the present work reports on a suitable strategy to influence complex POM-based systems towards self-organization into multidimensional structures of higher hierarchy. The obtained compounds have been shown to possess electrocatalytic activity towards the reduction of iodates(V).Some of the common strategies to obtain multidimensional POM-based coordination polymers include the binding of densely charged POM anions with various linkage units, such as functional organic ligands, transition metals, and metal complexes, as well as rare-earth metals. [9][10][11][12][13][14] The majority of the reports related to POM-based heterometallic compounds cover examples with Cu as a second metal, [15][16][17] while only a few publications mention the anions' combination with cobalt. [18,19] Co-containing compounds based on POMs have gained popularity in the development of wateroxidation catalysts and have shown better activity than the widespread copper complexes. [20,21] Another intriguing possibility is the use of alkaline-earth metals as promising templates for discovering new binding motifs with POMs. [22] With charge numbers similar to those of typical d-elements, and possessing coordination modes and sizes similar to lanthanide ions, the alkaline-earth metals offer new and largely underexplored tools for driving self-assembly in POM-based hybrids. [23] There are also a number of vanadiumbased polyanions linked by alkaline-earth metals. [24][25][26] Moreover, the influence of the size of the guest metal ions (Ca 2+ , Sr 2+ , or Ba 2+ ) on the arrangement of Pd II -oxo shells in polyoxo noble metalates has been demonstrated. [27] Inspired by the reported structure-directing template effect of the metals on the formation of POMs, we decided to study the influence of Ca 2+ and Sr 2+ ions on phosphomolybdate-based structures. According to the CCDC, most of the publications cover [P 6 Mo 18 O 73 ] 8and [P 4 Mo 6 O 28-x (OH) 3+x ] (9-x)based compounds with Ca, Sr, and (rarely) Ba. [28][29][30][31][32] Another unique hig...
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