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

Abstract

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 1H 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 (Δ­(δδδδ)­Λ­(λλλλ) form) and a racemic mixture of Δ­(δδδδ)­Δ­(δδδδ) and Λ­(λλλλ)­Λ­(λλλλ) forms were formed, respectively. The dynamic 1H NMR studies suggest the following: (i) the activation entropies (ΔS ⧧) 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 ΔS ⧧ values of the Ag+ complexes with L b were negative only when the side arms of both cyclens rotated simultaneously, and the ΔS ⧧ values for the 1:1 and 1:2 complexes were positive when one cyclen side arm was rotated. These values of ΔS ⧧ indicate that the biphenyl side arms between the two cyclens are not long enough to rotate the ring freely.

Regioselective Coordination toward Silver(I) Ions by Bis- and Tris(Tetra-Armed Cyclen)s via Differential Electron Density of Aromatic Side Arms

“…Single crystals of 1:3 (= tris­(tetra-armed cyclen):Ag + ) complexes with 3 MFM ([ 3 MFM ·(Ag) 3 ]­(OTf) 3 ), 3 FMF ([ 3 MFM ·(Ag) 3 ]­(OTf) 2 Cl, [ 3 FMF ·(Ag) 3 ]­(BF 4 ) 3 ), and 4 MFM ([ 4 MFM ·(Ag) 3 ]­(OTf) 3 ) were obtained, and X-ray crystal structure analysis was performed (Figures and S62–S65). As a result, each Ag + is coordinated by four N atoms in the cyclen ring and covered by four aromatic side arms, similar to the previously reported tetra-armed cyclen/Ag + complexes . The conformations of the side arms (Δ or Λ) and cyclen rings ( δδδδ or λλλλ ) in each cyclen moiety were the Δ­( δδδδ )­Δ­( δδδδ )­Δ­( δδδδ )-form or the Λ­( λλλλ )­Λ­( λλλλ )­Λ­( λλλλ )-form and existed as a racemic mixture.…”

“…Their conformations are the same as those of the bis(tetra-armed cyclen) bridged by a 4,4′-dimethyl-1,1′biphenyl group, which we reported previously. 12 Interestingly, when the complex of 3 FMF with AgOTf was prepared in a mixture of chloroform and methanol, a complex [3 FMF • (Ag) 3 ](OTf) 2 Cl was obtained, which included two OTf − and one Cl − as the counteranions. However, the structure of the [3 FMF •(Ag) 3 ] 3+ moiety was the same as that of the different counteranions.…”

“…As a result, each Ag + is coordinated by four N atoms in the cyclen ring and covered by four aromatic side arms, similar to the previously reported tetra-armed cyclen/Ag + complexes. 12 The conformations of the side arms (Δ or Λ) and cyclen rings (δδδδ or λλλλ) in each cyclen moiety were the Δ(δδδδ)Δ(δδδδ)Δ(δδδδ)-form or the Λ(λλλλ)Λ(λλλλ)Λ(λλλλ)-form and existed as a racemic mixture. Their conformations are the same as those of the bis(tetra-armed cyclen) bridged by a 4,4′-dimethyl-1,1′biphenyl group, which we reported previously.…”

“…Recently, we have reported several argentivorous molecules with aromatic side arms. − As shown in Figure a, when tetra-armed cyclen ( 1 H ) with benzyl groups as aromatic side arms forms a complex with Ag + , the Ag + is incorporated into the cyclen cavity. The complexation is facilitated by Ag + –π interactions between Ag + and the aromatic side arms, which involve interactions between the 5s orbital of Ag + and the π electrons of the aromatic ring.…”

14- and 17-Membered Macrocycles Containing Amide, Amino, and Carbamate Groups in The Monocyclic Skeleton: An Accidental Byproduct Obtained from a Residue after Separation

“…However, we could not obtain analyzable good 2D NMR spectra even though we recorded for a long time at 333 K. The activation parameters of 5 and 3 were estimated using VT-NMR (Figures S26 and S27). The activation energy ΔG ‡ is higher than that of the ring inversion energies of triarmed cyclen 17 and Ag(I) complexes with biscyclen derivatives 32 previously reported biscyclen derivatives. The reaction of 5 with triethylenetetramine gave the 17membered macrocycle (7) (Figures S28 and S29).…”