Syntheses, structures, and properties of a series of supramolecular hybrids based on Keggin or Wells–Dawson polyoxometalates and 4,4′-bipyridines

Exploring Wells-Dawson Clusters Associated With the Small Ribosomal Subunit

“…In Figure 5 four different possible classes of dimeric structures are shown. In examining the 105 structures emerged in the CSD “P 2 W 18 O 62 ” search, four structures that can been described as a “double cluster” were identified by containing two crystallographically unique clusters in close proximity, i.e., refcodes JETSOR, PUPJUG, PUPJOA, and FUVXAW ( vide infra ) (Gong et al, 2006; Barrier et al, 2009; Yang et al, 2010). Although these reported structures also suffer from relatively large reliability (R 1 ) indices in their models, the resolution is much higher for these solid-state structures than in proteins and allows a glimpse of possible examples.…”

“…Interactions directly between the clusters themselves are between oxo-oxo, oxo-bridged, and bridged-bridged oxygens atoms. In the structure with refcode PUPJUG (CCDC #743675, Yang et al, 2010), there are numerous interactions, but the shortest include one terminal W = O bond on the belt (O d2 ). This oxygen interacts with a triangular face of W = O on the other cluster (O d1 , O d1 , and O d2 ) with distances ranging from 2.818 to 3.641 Å.…”

“…In the structure with refcode PUPJOA, (CCDC #743674, Yang et al, 2010) there are three 4,4-bipyridine molecules directly between the clusters and, therefore fewer direct interactions. Two belt oxo units (O d2 ) of one cluster interact with one belt (O d2 ) and one cap (O d1 ) of the other.…”

“…For example, the Zr(IV)–containing polyoxometalates derivatives that are found to effectively cleave proteins near aspartate residues (Absillis and Parac-Vogt, 2012; Ly et al, 2013; Stroobants et al, 2013; Vanhaecht et al, 2013). Both experimental studies and theoretical studies are available in some cases documenting the dimerization of polyoxometalates and formation of different isomers (Gong et al, 2006; Zhao et al, 2008; Barrier et al, 2009; Kurashina et al, 2009; Yang et al, 2010; Liu et al, 2014), e.g., the mechanistic study of peptide bond hydrolysis by the Wells-Dawson cluster (Absillis and Parac-Vogt, 2012). Dimerization of Lindqvist and Keggin Clusters through M-μ-O-M junctions have been investigated using DFT methods (Lopez et al, 2006), but it should be noted that W is not commonly engaged in these processes and dimer formation is more common for metal ions such as Nb, Ti, Cr, Fe, and Zr (Gong et al, 2006; Zhao et al, 2008; Barrier et al, 2009; Kurashina et al, 2009; Yang et al, 2010; Liu et al, 2014).…”

“…Both experimental studies and theoretical studies are available in some cases documenting the dimerization of polyoxometalates and formation of different isomers (Gong et al, 2006; Zhao et al, 2008; Barrier et al, 2009; Kurashina et al, 2009; Yang et al, 2010; Liu et al, 2014), e.g., the mechanistic study of peptide bond hydrolysis by the Wells-Dawson cluster (Absillis and Parac-Vogt, 2012). Dimerization of Lindqvist and Keggin Clusters through M-μ-O-M junctions have been investigated using DFT methods (Lopez et al, 2006), but it should be noted that W is not commonly engaged in these processes and dimer formation is more common for metal ions such as Nb, Ti, Cr, Fe, and Zr (Gong et al, 2006; Zhao et al, 2008; Barrier et al, 2009; Kurashina et al, 2009; Yang et al, 2010; Liu et al, 2014). Some of these clusters form through interaction with coordination complexes such as a peptide complex which can then react by replacement of the ligand to form a dimer (Lopez et al, 2006).…”