H-Bonded anion-anion complexes in fentanyl citrate polymorphs and solvates
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Published on: March 29, 2024
Rafael Barbas1, Rafel Prohens2, Antonio Bauzá3
1Unitat de Polimorfisme i Calorimetria, Centres Científics i Tecnològics, Universitat de Barcelona, Baldiri Reixac 10, 08028 Barcelona, Spain. rafel@ccit.ub.edu.
Abstract:
Herein we report the experimental observation (X-ray characterization) of two different binding modes in H-bonded anion-anion complexes (anion = citrate) in N-(1-(2-phenylethyl)-4-piperidinylium)-N-phenyl-propanamide-citrate (fentanyl citrate). High level DFT calculations indicate that both types of anion-anion complexes (one with two and the other with four H-bonds) are thermodynamically unstable but kinetically stable with respect to the isolated anions with activation barriers as high as 14 kcal mol-1.
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