Investigation of the Complexation between 4-Aminoazobenzene and Cucurbit7uril through a Combined Spectroscopic, Nuclear Magnetic Resonance, and Molecular Simulation Studies
S Sarraute and AS Biesse-Martin and J Devemy and A Dequidt and C Bonal and P Malfreyt, ACS OMEGA, 7, 25013-25021 (2022).
Cucurbiturils are well known for their ability to form supramolecular systems with ultrahigh affinities binding. Inclusion complex between 4-aminoazobenzene and cucurbit7uril has been investigated in aqueous solution by ultraviolet (UV)-spectroscopy, H-1 NMR, and molecular simulations. 4-aminoazobenzene shows high affinity in acidic solutions while no association was detected in neutral solutions. The thermodynamic properties of complex formation are investigated using both UV spectroscopy and nudear magnetic resonance (NMR) measurements. Our results highlight that the high binding constant between CB7 and 4AA (log K = 4.9) is the result of a large negative change in Delta H-r(o) (-19 kJ/mol) and a small positive change in T Delta S-r(o) (9 kJ/mol). The analysis of the experimental data lead to hypothesis on the structure of the complex. We have used molecular dynamics simulation to interpret experiments. Interestingly, the cis-trans isomerization of aminoazobenzene is considered. All the results are discussed and compared with those previously obtained with other host molecules.
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