Argentivorous molecules with two kinds of aromatic side-arms: intramolecular competition between side-arms

Abstract

Three tetra-armed cyclens with two kinds of side-arms, 3',5'-difluorobenzyl/4'-methylbenzyl, 3',5'-difluorobenzyl/1'-naphthylmethyl, and 3',5'-difluorobenzyl/9'-anthrylmethyl groups, were prepared by reductive amination of 1,7-bis(3',5'-difluorobenzyl)-1,4,7,10-tetraazacyclododecane and the corresponding aromatic aldehydes in the presence of NaBH(OAc)3. The X-ray structures of the Ag(+) complexes and Ag(+)-ion-induced (1)H NMR spectral changes suggest that (i) the chemical shift changes of the protons at the 2'- and 6'-positions in the 3',5'-difluorobenzyl/4'-methylbenzyl side-arms are dependent on the electron density on the adjacent substituted benzenes, and (ii) in the tetra-armed cyclens with 3',5'-difluorobenzyl/1'-naphthylmethyl and 3',5'-difluorobenzyl/9'-anthrylmethyl groups as side-arms, electron-rich aromatic rings preferentially cover the Ag(+) ions incorporated into the ligand cavities, and 3',5'-difluorobenzyl groups do not participate in the Ag(+) interactions. The log K values were estimated using Ag(+)-ion-induced UV-vis spectral changes.

Exciplex Formation and Aggregation Induced Emission in Di‐(N‐benzyl)cyclen and Its Complexes – Selective Fluorescence with Lead(II), and as the Cadmium(II) Complex, with the Chloride Ion

“…The formation of the peak centered on 353 nm in the Zn II DB‐cyclen complex alone is of particular interest. One should stress that all attempts at model building based on structures of DB‐cyclen complexes like those reported here for the Pb II , Cu II , Ag I , or Cd II DB‐cyclen complexes, or for other similar complexes reported by Habata et al, indicate that formation of intramolecular exciplexes is rendered sterically impossible for N ‐benzyl groups placed on opposite nitrogen atoms of a cyclen type ligand. This is due to blocking of any such required π stacked structures required for the formation of an exciplex by ligands such as water or simple anions coordinated to the metal ion, and by the metal ion itself.…”

“…It is quite possible that one sees an intermolecular π contact here in the solid state, but that in solution, because of the much greater dilution, there may be intramolecular π contacts. A pattern of π contact formation by cyclen‐based ligands with attached aromatic groups is suggested by the work of Habata et al Where there are four N ‐benzyl or other similar aromatic groups, intramolecular π contacts may be present. Thus, the TB‐cyclen complex of Ag I forms four π contacts with the four N ‐benzyl groups of the ligand.…”

“…These authors did not observe any unusual metal ion sensing selectivity for DA‐cyclen, nor investigate the effect of added anions on the fluorescence properties of DA‐cyclen complexes. Cyclen based ligands with N ‐benzyl, N ‐anthracenyl, and a number of other N ‐aryl‐methyl substituents have been investigated by Habata et al The interest in these ligands was the generation of Ag I selectivity by virtue of the formation of Ag ··· C π contacts, which were shown to be present crystallographically. These authors showed that Ag I in its DA‐cyclen complex forms two short π contacts to the two anthracenyl groups present, while in its TB‐cyclen complex four Ag ··· C π contacts are present.…”

Pentacyclic Nano‐Trefoil

“…Cyclen is a 12‐membered cyclic polyamine that forms stable complexes with several metal ions [11–22] . Tripier et al.…”

“…In these armed cyclens, the side arms wrap around Ag + to incorporate it in the cyclen via Ag + ‐π interactions between Ag + and the side arms and CH‐π interactions among the side arms. We call these complexes argentivorous molecules, which means silver (argentum) eating (vorous) [17–22] …”