Metal Ion Binding to Calixarenes: Pendent Arm Coordination Assisted by Self-Inclusion

1994 ◽  
Vol 47 (6) ◽  
pp. 1185 ◽  
Author(s):  
JM Harrowfield ◽  
M Mocerino ◽  
BW Skelton ◽  
CR Whitaker ◽  
AH White
Keyword(s):  
Structural Characterization ◽  
Metal Ion ◽  
Room Temperature ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Cone Conformation ◽  
X Ray ◽  
Partial Cone ◽  
Arm Coordination

The synthesis and room-temperature single-crystal X-ray structural characterization of 25,27- di(allyloxy)-5,17-di-t-butyl-26,28-dimethoxycalix[4]arene are recorded. Crystals are monoclinic, C2/c, a 29.089(5), b 10.742(2), c 26.218(8) Ǻ, β 110.09(2)°, Z = 8; the structure was refined to a residual of 0.065 for 4103 independent 'observed' [I > 3σ(I)] reflections. The flattened partial cone conformation of the molecule allows inclusion of one of the methoxy substituents in a way which could block inclusion of a metal ion capable of polyhapto aromatic coordination and which may therefore explain why solution n.m.r. measurements indicate that silver(I) binds to the pendent alkene groups.

Synthesis and ESI-MS Alkali Metal Ion Binding Selectivities of Cone, Partial Cone, and 1,3-Alternate 1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]arene Crown-6 and 1,1'-Binaphthalene-2,2'-diyl Crown-6 Conformers

2004 ◽  
Vol 69 (5) ◽  
pp. 1109-1125 ◽  
Author(s):  
George Ferguson ◽  
Alan J. Lough ◽  
Anna Notti ◽  
Sebastiano Pappalardo ◽  
Melchiorre F. Parisi ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Metal Ion ◽  
Ion Binding ◽  
Ionization Mass ◽  
Metal Ion Binding ◽  
Alkali Metal Ion ◽  
X Ray ◽  
Partial Cone ◽  
Competitive Complexation ◽  
New Compounds

The syntheses of 1,3-bis(α-picolyloxy)-p-tert-butylcalix[4]arene crown-6 and 1,1'-binaphthalene-2,2'-diyl crown-6 title conformers have been achieved by two complementary synthetic strategies, which differ in the order in which the polyether loop and the pendant picolyl groups are introduced. The structure and conformation of all new compounds have been firmly established by NMR spectroscopy, and further proven by X-ray analysis for the intermediate p-tert-butyl-25,27-(1,1'-binaphthalene-2,2'-diyl-crown-6)-26,28-dihydroxycalix[4]arene. Within each set of conformers, the nature of the polyether chain has little or no influence on the overall conformation of the calixarene platform. The alkali metal ion binding selectivities of the two series of calixarenes have been evaluated in competitive complexation experiments by electrospray ionization mass spectrometry. In the p-tert-butylcalix[4]arene crown-6 series, partial cone and 1,3-alternate conformers show a peak selectivity for the larger Cs+ ions, while the cone one preferentially binds the smaller Na+ ions. On the other hand, the cone and 1,3-alternate binaphthyl-containing analogues show a preference for Na+ ions, the partial cone being quite unselective.

scholarly journals Snapshots of a Non-Canonical RdRP in Action

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1260
Author(s):  
Diego S. Ferrero ◽  
Michela Falqui ◽  
Nuria Verdaguer
Keyword(s):  
Metal Ion ◽  
Rna Viruses ◽  
Ion Binding ◽  
Genome Replication ◽  
Metal Ion Binding ◽  
Insect Virus ◽  
X Ray ◽  
Template Strand ◽  
Nucleotide Incorporation ◽  
Elongation Process

RNA viruses typically encode their own RNA-dependent RNA polymerase (RdRP) to ensure genome replication and transcription. The closed “right hand” architecture of RdRPs encircles seven conserved structural motifs (A to G) that regulate the polymerization activity. The four palm motifs, arranged in the sequential order A to D, are common to all known template dependent polynucleotide polymerases, with motifs A and C containing the catalytic aspartic acid residues. Exceptions to this design have been reported in members of the Permutotetraviridae and Birnaviridae families of positive single stranded (+ss) and double-stranded (ds) RNA viruses, respectively. In these enzymes, motif C is located upstream of motif A, displaying a permuted C–A–B–D connectivity. Here we study the details of the replication elongation process in the non-canonical RdRP of the Thosea asigna virus (TaV), an insect virus from the Permutatetraviridae family. We report the X-ray structures of three replicative complexes of the TaV polymerase obtained with an RNA template-primer in the absence and in the presence of incoming rNTPs. The structures captured different replication events and allowed to define the critical interactions involved in: (i) the positioning of the acceptor base of the template strand, (ii) the positioning of the 3’-OH group of the primer nucleotide during RNA replication and (iii) the recognition and positioning of the incoming nucleotide. Structural comparisons unveiled a closure of the active site on the RNA template-primer binding, before rNTP entry. This conformational rearrangement that also includes the repositioning of the motif A aspartate for the catalytic reaction to take place is maintained on rNTP and metal ion binding and after nucleotide incorporation, before translocation.

Structural Systematics of Rare Earth Complexes. VII. Crystal Structure of Bis(2,2'/6',2␛-Terpyridinium) Octaaquaterbium(III) Heptachloride Hydrate

1994 ◽  
Vol 47 (2) ◽  
pp. 391 ◽  
Author(s):  
CJ Kepert ◽  
BW Skeleton ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Single Crystal ◽  
Structural Characterization ◽  
Title Compound ◽  
Room Temperature ◽  
Chloride Ions ◽  
Full Matrix ◽  
X Ray

The room-temperature single-crystal X-ray structural characterization of the title compound (tpyH2)2[Tb(OH2)8]Cl7.~2⅓H2O is recorded. Crystals are triclinic, Pī , a 17.063(5), b 16.243(3), c 7.878(3) Ǻ, α 84.78(2), β 84.39(3), γ 87.81(2)°, Z = 2 formula units; 3167 'observed' diffractometer reflections were refined by full-matrix least-squares procedures to a residual of 0.057. Notable features of interest of the compound are the 'chelation' of chloride ions by the terpyridinium cations , and the existence of a free [Tb(OH2)8]2+ cation in the presence of an abundance of chloride ions.

Structural Characterization of a Cage Ligand Fragmentation Reaction

1994 ◽  
Vol 47 (1) ◽  
pp. 181 ◽  
Author(s):  
JM Harrowfield ◽  
AM Sargeson ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Structural Characterization ◽  
Room Temperature ◽  
Fragmentation Reaction ◽  
X Ray ◽  
Nitrogen Donor ◽  
Crystal Structural

The room temperature X-ray single-crystal structural characterization of a protonated copper(II) complex of a ligand artefact, L′, of L = N-Me6sar (described in an accompanying paper) is recorded, the new ligand L′ being generated formally by elimination of a CH2CH2 bridge between a pair of nitrogen donor atoms of L. The complex, [ ClCu (H2L′) (ClO4)3.2H2O, is orthorhombic, Pccn , a 22.528(7), b 10.544(3), c 13.748(6) Ǻ, Z = 4 formula units, R being 0.053 for 1133 independent 'observed' [I > 3σ(I)] reflections. The cation, containing five-coordinate square-pyramidal ClCuN4 copper, is disposed with the Cu- Cl bond [2.458(3)Ǻ] lying on a crystallographic 2 axis; Cu-N distances are 2.094(8) and 2.093(8)Ǻ.

Synthesis and structural characterization of anion complexes with azacalix[2]dipyrrolylmethane: effect of anion charge on the conformation of the macrocycle

2016 ◽  
Vol 45 (29) ◽  
pp. 11781-11790 ◽  
Author(s):  
Tapas Guchhait ◽  
Ganesan Mani ◽  
Carola Schulzke
Keyword(s):  
Single Crystal ◽  
Structural Characterization ◽  
X Ray ◽  
Partial Cone ◽  
Anion Complexes

Azacalix[2]dipyrrolylmethane is flexible changing its 1,3-alternate conformation to the 1,2-alternate, partial cone or cone conformations with respect to the charge on the anion, as shown by a series of single crystal X-ray structures of inorganic mono- and dianionic complexes.

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