¹H NMR Study of a Chiral Argentivorous Molecule/Ag⁺ Complex: Assignment of Proton Signals of Four Aromatic Rings with Slightly Different Environments

Abstract

The proton signals at the 2′- and 6′-positions of the aromatic side arms of a silver­(I) complex with a chiral tetra-armed cyclen ((S)-L2) are assigned by comparison with 1H NMR spectra and X-ray structure of Ag+ complexes with three analogues of (S)-L2: (S)-L2 3D having one benzyl group and three deuterium-substituted benzyl groups, (S)-L2 2D having two benzyl groups and two deuterium-substituted benzyl groups, and (S)-L2 F having three benzyl groups and one 4′-fluorobenzyl group. An interaction factor is defined by using the X-ray structures. The chemical shift values of the proton signals in the aromatic side arms can be explained by using the interaction factors that are defined by the dihedral angles, the angles between two mean planes, and the CH···π distances from the X-ray data of the (S)-L2/Ag+ complex.

Bis-Argentivorous Molecules Bridged by Phenyl and 4,4′-Biphenyl Groups: Structural and Dynamic Behavior of Silver Complexes

“…Maier et al reported that the strength of the intermolecular Ag + –π interaction in solution was −1.34 to −2.63 kcal/mol . In addition, the structures of tetra-armed cyclen/Ag + complexes in the data previously reported showed only two types of conformers: Δ­( δδδδ ) and Λ­( λλλλ ) forms. − ,,,,− Therefore, we performed DFT calculations (B3LYP/6-31G*) of the Λ­( λλλλ ) form and its side arm rotated isomer, Δ­( λλλλ ) form, to investigate whether the silver­(I) complex with 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane forms not only stable Δ­( δδδδ ) and Λ­( λλλλ ) but also Δ­( λλλλ ) and Λ­( δδδδ ) forms (Figure S17). As a result, the energy difference between Λ­( λλλλ ) and Δ­( λλλλ ) forms was about 8.6 kJ/mol, and the relative amounts of each isomer would be 2.1 × 10 6 :1 (=Λ­( λλλλ ):Δ­( λλλλ )) (Table S1).…”

Argentivorous Molecules with Oxyethylene Chains in Side-Arms: Silver Ion-Induced Selectivity Changes toward Alkali Metal Ions

“…In connection with argentivorous molecules, − we have developed new functional molecules using cyclen with aromatic side-arms. − In this study, we designed a new type of argentivorous molecule that introduced an oxyethylene chain at the 4-position of the aromatic side-arms as a secondary recognition site. We expected that the complexation of the cyclen moiety with silver ions would change the aromatic side-arms’ conformation and that the four oxyethylene chains would be arranged to surround the second metal cation.…”