The crystal and molecular structures of Cs⁺ complexes of tetranactin and nonactin

Abstract

The structure of the Cs+-tetranactin complex [space group P2~/n, Z = 4, a = 16.022 (6)

A solid-state 133Cs nuclear magnetic resonance and X-ray crystallographic study of cesium complexes with macrocyclic ligands

“…The 133 Cs CSA for the Cs + -nonactin complex is also small. This is consistent with the crystal structure of CsSCN/nonactin where the Cs + ion is located approximately at the center of a cube whose eight corners are formed by oxygen donor atoms from the nonactin molecule (18). The stationary 133 Cs NMR spectrum of Cs(DB18C6) 2 SCN exhibits a complex line shape due to the presence of two Cs sites.…”

High-resolution solid-state carbon-13 NMR study of free and metal-complexed macrocyclic antibiotic ionophores valinomycin, nonactin, and tetranctin: conformational elucidation in solid and solution by conformation-dependent carbon-13 chemical shifts

“…This observation shows that the local conformations of the ligand molecules in the six kinds of metal complexes (K+, Na+, and Cs+ ions complexed with nonactin and tetranactin) are effectively identical, as viewed from the conformation-dependent 13C chemical shifts. In good agreement with this prediction by the ,3C NMR data, the molecular conformations of these metal complexes by X-ray diffraction turned out to take approximate S4 symmetry, and differences of the torsion angles between the pairs of enantiomers are less than 10°, as observed for K+-, Na+-, and Cs+-complexed nonactin and Cs+-tetranactin (Dobler, 1969;Dobler & Phizackerley, 1974;Sakamaki et al, 1977). Further, these torsion angles are in good agreement (<30°) among the six kinds of complexes (Dobler, 1969;Dobler & Phizackerley, 1974;Sakamaki et al, 1976Sakamaki et al, , 1977 (Figure 6B).…”

“…In good agreement with this prediction by the ,3C NMR data, the molecular conformations of these metal complexes by X-ray diffraction turned out to take approximate S4 symmetry, and differences of the torsion angles between the pairs of enantiomers are less than 10°, as observed for K+-, Na+-, and Cs+-complexed nonactin and Cs+-tetranactin (Dobler, 1969;Dobler & Phizackerley, 1974;Sakamaki et al, 1977). Further, these torsion angles are in good agreement (<30°) among the six kinds of complexes (Dobler, 1969;Dobler & Phizackerley, 1974;Sakamaki et al, 1976Sakamaki et al, , 1977 (Figure 6B). It is now clear that the conformation-dependent 13C chemical shifts can be conveniently utilized to clarify the conformations of uncomplexed and metal-complexed nactins (nonactin, monactin, dinactin, and tetranactin) in the solid state.…”

“…Obviously, the spectral features of the 13C NMR spectra of metal-complexed nonactin and tetranactin are significantly varied as compared to those of free molecules (Figures 3 and 4). This is unequivocally caused by a drastic conformational change of the ligand molecules by complex formations (Dobler, 1972;Dobler et al, 1969;Dobler & Phizackerley, 1974;Iitaka et al, 1972;Nawata et al, 1974;Sakamaki et al, 1976Sakamaki et al, , 1977.…”

Pseudomerohedrally twinned monoclinic structure of unfolded `free' nonactin: comparative analysis of its large conformational change upon encapsulation of alkali metal ions

“…The conformation of 'free' nonactin was compared with that observed in the previously reported nonactin complexes with Na + (Dobler & Phizackerley, 1974), K + (Kilbourn et al, 1967), Cs + (Sakamaki et al, 1977), Ca 2+ (Vishwanath et al, 1983) and NH 4 + (Neupert-Laves & Dobler, 1976) using a new subroutine WBOX developed specifically for this project in the program OLEX2 (Dolomanov et al, 2009) to compute the dimensions of the smallest parallelepiped superscribing each of the nonactin complexes (Fig. 4).…”