5,6-BENZO-4,7,13,16,21,24-HEXAOXA-1,10-DIAZABICYCLO[8.8.8]HEXACOS-5-ENE

The Uses of 5,6-BENZO-4,7,13,16,21,24-HEXAOXA-1,10-DIAZABICYCLO[8.8.8]HEXACOS-5-ENE

5,6-Benzo-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacos-5-ene can be used as a model ligand:

• In the metal-ligand complex formation studies to predict ligand coordination with metal ions (Eu & Gd) using magnetic resonance imaging (MRI) technique.
• In the study of coordination environment as well as redox and electronic properties of its Yb^II complexes.

Reactions

[Eu(2.2.2B)Cl][BPh4]·2CH3OH. (2.2.2B = C22H36N2O6): In an argon atmosphere glovebox, 14.0 mg of EuCl2 was dissolved in 1.5 mL of distilled methanol in a 20 mL scintillation vial. Separately, 50.0 mg of [NBu4][BPh4] was dissolved in THF dropwise in a 6 mL scintillation vial. The [NBu4][BPh4] was carefully pipetted into the methanolic solution containing EuCl2 with stirring. 222 μL of a 0.1 M solution of 2.2.2B cryptand in THF was added to the reaction mixture which was briefly stirred before being allowed to sit overnight undisturbed. Colorless block crystals of [Eu(2.2.2B)Cl][BPh4]·2CH3OH formed overnight (Yield: 67.7%). Crystals were isolated via pipet and stored under immersion oil until single-crystal X-ray diffraction analysis could be performed. 1H NMR (CD3CN-d3): 7.30 (s, CH, 2H), 7.02 (s, CH, 2H), 6.87 (s, CH, 1H), 6.32 (s, broad), 3.67 (m, CH2O), 3.30 (s, CH3), 2.18 (s, OH, 1H), 1.83 (s, CH2) (Figure S3). PXRD analysis appears in the Supporting Information (SI) (Figure S5).
[Eu(2.2.2B)(CH3OH)][BPh4]2·CH3OH. Synthesis of [Eu(2.2.2B)(CH3OH)][BPh4]2·CH3OH was achieved as described for [Eu(2.2.2B)Cl][BPh4]·2CH3OH with the exception of the dissolution of the [NBu4][BPh4] solid in acetonitrile rather than THF. Combination of the two colorless solutions produced a yellow solution. Addition of 222 μL of 0.1 M 2.2.2B cryptand in THF yielded no distinguishable change, but colorless block crystals of [Eu(2.2.2B)(CH3OH)][BPh4]2·CH3OH formed overnight (Yield: 74.2%). These crystals were isolated and stored in the same fashion as [Eu(2.2.2B)Cl][BPh4]·2CH3OH. 1H NMR (CD3CN-d3): 7.30 (s, CH, 2H), 7.01 (s, CH, 2H), 6.86 (s, CH, 1H), 6.21 (s, broad), 3.66 (s, CH2O), 3.28 (s, CH3), 2.27 (s, OH, broad), 1.82 (s, CH2) (Figure S4). PXRD analysis appears in the SI (Figure S6).
A solution of 5,6-benzo-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacos-5-ene (2.2.2B cryptand, 50% wt in toluene, Sigma-Aldrich) was prepared by first isolating the ligand in vacuo, and a 0.1 M stock solution of 2.2.2B cryptand in THF was prepared.
[1] TODD N. POE. Understanding the Stabilization and Tunability of Divalent Europium 2.2.2B Cryptates[J]. Inorganic Chemistry, 2021, 60 11: 7815-7826. DOI:10.1021/acs.inorgchem.1c00300.

Structure and conformation

Figure S3. 1H NMR spectrum of [Eu(2.2.2B)Cl][BPh4] ? 2CH3OH. Major peaks that did not experience significant broadening are labelled.

Figure S4. 1H NMR spectrum of [Eu(2.2.2B)(CH3OH)][BPh4]2 ? CH3OH. The significant broadening of the methanol signal at 2.27 ppm is attributed to the coordination of methanol to the cryptate complex, unlike in [Eu(2.2.2B)Cl][BPh4] ? 2CH3OH.