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

Bis-argentivorous molecules (L-a and L-b), which have phenyl and 4,4'-biphenyl groups as linkers, have been prepared. The structures of Ag+ complexes with the new ligands (L-a and L-b) were investigated in solution and the solid state. The CSI-MS and H-1 NMR titration of L-a and L-b with Ag+ show 1:1 and 1:2 complexes depending on the [Ag+]:[L] ratios. In the solid-state structures, single crystals of L-a and L-b with 2 equiv of Ag+ were prepared. X-ray crystallography of the silver(I) complexes with L-a and L-b showed that an intramolecular racemic structure (Delta(delta delta delta delta)Lambda(lambda lambda lambda lambda) form) and a racemic mixture of Delta(delta delta delta delta)Delta-(delta delta delta delta) and Lambda(lambda lambda lambda lambda)Lambda(lambda lambda lambda lambda) forms were formed, respectively. The dynamic H-1 NMR studies suggest the following: (i) the activation entropies (Delta S double dagger) of the side arm rotations in the Ag+ complex with L-a were all negative, indicating restricted rotation of the side arms due to their shortness, and (ii) the Delta S double dagger values of the Ag+ complexes with L-b were negative only when the side arms of both cyclens rotated simultaneously, and the Delta S double dagger values for the 1:1 and 1:2 complexes were positive when one cyclen side arm was rotated. These values of Delta S double dagger indicate that the biphenyl side arms between the two cyclens are not long enough to rotate the ring freely.

Automated summary

Bis-argentivorous molecules containing phenyl and 4,4'-biphenyl groups as linkers were prepared to form complexes with Ag+ in different ratios. X-ray crystallography revealed the formation of intramolecular racemic structures in the silver(I) complexes. Dynamic H-1 NMR studies indicated restricted rotation of the side arms due to their shortness.