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Open AccessArticle

Investigating Differences and Similarities between Betaxolol Polymorphs

Department of Industrial Engineering, University of Florence, via Santa Marta 3, 50139 Florence, Italy
Centro di Cristallografia Strutturale, University of Florence, via della Lastruccia 3, Sesto, 50019 Florence, Italy
Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti OrganoMetallici (CNR-ICCOM), via Madonna del Piano 10, Sesto, 50019 Florence, Italy
Department of Chemistry “U. Schiff”, University of Florence, via della Lastruccia 3, Sesto, 50019 Florence, Italy
Author to whom correspondence should be addressed.
Crystals 2019, 9(10), 509;
Received: 29 August 2019 / Revised: 13 September 2019 / Accepted: 19 September 2019 / Published: 29 September 2019
Betaxolol belongs to the class of β1-adrenergic blocking agent. Several polymorphs of racemic betaxolol have been reported in the literature, but only one of them (BE_I) had the crystal structure determined from single-crystal X-ray diffraction. Here, we present a new crystalline phase of betaxolol (BE_IV). Its solid-state structure has been obtained from single-crystal X-ray diffraction data. The molecular and crystal arrangements of betaxolol in BE_IV have been further investigated by molecular modelling, by Cambridge Structural Database (CSD) surveys and by Hirshfeld surface analysis. A comparison with the solid-state structure of BE_I have been carried out. In the two polymorphs the 2-hydroxy-3-(isopropylamino)-propoxy chain, which is common to other β-blocker drugs, adopts a different conformation. In addition, the rotational isomer found in BE_IV is different with respect to the four already observed in the solid-state structure of analogous compounds. In both the polymorphs, the most significant interaction is due to the H-bonds involving the OH group as donor and the NH as acceptor, while the interaction where OH works as acceptor (NH acts as donor) is definitely less important. The resulting H-bond patterns are however different: Alternate R2,2(10) a > a (OH donors) and R2,2(10) b > b (OH acceptors) in BE_I vs. alternate R4,4 (8) a > b > a > b (OH donors) and R2,2 (10) b > b (OH acceptor) in BE_IV. View Full-Text
Keywords: betaxolol; polymorph; crystal structure; β1 blockers betaxolol; polymorph; crystal structure; β1 blockers
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MDPI and ACS Style

Rossi, P.; Paoli, P.; Milazzo, S.; Chelazzi, L.; Ienco, A.; Conti, L. Investigating Differences and Similarities between Betaxolol Polymorphs. Crystals 2019, 9, 509.

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