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Li S, Liu B, Chen Z, Ou X, Rong H, Lu M. Ritonavir Revisited: Melt Crystallization Can Easily Find the Late-Appearing Polymorph II and Unexpectedly Discover a New Polymorph III. Mol Pharm 2023; 20:3854-3863. [PMID: 37450774 DOI: 10.1021/acs.molpharmaceut.2c00994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
Identification of a thermodynamically stable polymorph is an important step in the early stage of drug development. Ritonavir (RIT) is a well-known case where the most stable polymorph II emerged after being marketed, leading to a loss of $250 million. Herein, we report the findings that routine melt crystallization can reveal the late-appearing polymorph II of RIT at small supercooling, but the probability of nucleation is very low. The addition of 30-50% polyethylene glycol (PEG) promotes the crystallization of Form II as the only phase at low supercooling, making it easier to detect in polymorphism screening. During the course of our research, a new polymorph, denoted Form III, was unexpectedly discovered, crystallizing as the major phase from neat RIT melts. Single crystals of Form III were grown from melt microdroplets. Benefiting from the ability of synchrotron radiation to detect weak diffraction signals that cannot be accessible by a laboratory diffractometer, a reasonable structure of Form III was solved with slight disorder relative to thiazole groups (P1 space group and Z' = 4). The thermodynamic stability ranking of the three true polymorphs is Form II > Form I > Form III, as opposed to the order of solubility. The capacity to efficiently reveal rich polymorphs, especially the kinetically hindered polymorph, and rapidly grow single crystals of a new phase for structure determination together highlights the necessity of incorporating melt crystallization into routine methods for pharmaceutical polymorphism screening.
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Affiliation(s)
- Shuting Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Binbin Liu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Ziqiao Chen
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Xiao Ou
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Haowei Rong
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Ming Lu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
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2
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3
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Wang Z, Cui X, Famulari A, Martí-Rujas J, Kariuki BM, Guo F. Solid-state stability of Z′ < 1 and Z′ = 2 polymorphs of N, N, N′, N′-tetrabenzylethylenediamine: a combined experimental and theoretical study. CrystEngComm 2022. [DOI: 10.1039/d2ce01174c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reported polymorphism in a highly flexible ligand gives a structure that is considered as a “crystal on the way” belonging to a metastable phase.
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Affiliation(s)
- Zhen Wang
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Xiaoxiao Cui
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Antonino Famulari
- Dipartimento di Chimica Materiali e Ingegneria Chimica. “Giulio Natta”, Politecnico di Milano, Via L. Mancinelli 7, 20131 Milan, Italy
- INSTM Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, 50121, Florence, Italy
| | - Javier Martí-Rujas
- Dipartimento di Chimica Materiali e Ingegneria Chimica. “Giulio Natta”, Politecnico di Milano, Via L. Mancinelli 7, 20131 Milan, Italy
- Center for Nano Science and Technology@Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
| | - Benson M. Kariuki
- School of chemistry, Cardiff University, Main Building, Park place, Cardiff CF10 3AT, Wales, UK
| | - Fang Guo
- College of Chemistry, Liaoning University, Shenyang 110036, China
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4
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Abstract
Sublimation is an effective and ‘green’ method to prepare and identify new polymorphs, cocrystals, ionic cocrystals and molecular salts.
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Affiliation(s)
- Patrick McArdle
- School of Chemistry, National University of Ireland, Galway, Ireland
| | - Andrea Erxleben
- School of Chemistry, National University of Ireland, Galway, Ireland
- Synthesis and Solid State Pharmaceutical Centre (SSPC), Limerick, Ireland
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5
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Saikia B, Pathak D, Sarma B. Variable stoichiometry cocrystals: occurrence and significance. CrystEngComm 2021. [DOI: 10.1039/d1ce00451d] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Stoichiometric variation in organic cocrystals, their synthesis, structure elucidation and properties are discussed. Accountable reasons for the occurrence of such cocrystals are emphasised.
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Affiliation(s)
- Basanta Saikia
- Department of Chemical Sciences
- Tezpur University
- Tezpur 784028
- India
- Max Planck Institute for Dynamics of Complex Technical Systems
| | - Debabrat Pathak
- Department of Chemical Sciences
- Tezpur University
- Tezpur 784028
- India
| | - Bipul Sarma
- Department of Chemical Sciences
- Tezpur University
- Tezpur 784028
- India
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6
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Chen J, Chen F, Han J, Su M, Liu K, Li Y, Wu Q. Crystallization and Purification of 4,4′‐Diaminodiphenyl Ether. Chem Eng Technol 2020. [DOI: 10.1002/ceat.201900519] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jianxin Chen
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
- Hebei University of TechnologyNational-Local Joint Engineering Laboratory for Energy Conservation of Chemical Process Integration and Resources Utilization 300130 Tianjin China
| | - Fengjiang Chen
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
| | - Jian Han
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
| | - Min Su
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
| | - Kaili Liu
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
| | - Yinhui Li
- Hebei University of TechnologySchool of Chemical Engineering and Technology 300130 Tianjin China
| | - Qing Wu
- Hebei University of TechnologySchool of Artificial Intelligence 300130 Tianjin China
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Bora P, Saikia B, Sarma B. Oriented Crystallization on Organic Monolayers to Control Concomitant Polymorphism. Chemistry 2019; 26:699-710. [PMID: 31651064 DOI: 10.1002/chem.201903938] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 09/24/2019] [Indexed: 11/06/2022]
Abstract
Nucleation events and crystal growth can be guided by molecular recognition at interfaces through intermolecular interactions. The short-acting antimicrobial sulfa drug sulfathiazole is known for its concomitant crystallization, which has five known polymorphs, due to conformational flexibility and hydrogen-bond synthon variation. In its development stage of a drug the issue of concomitant crystallization needs to be addressed with respect to patent litigation, including legal actions to protect patents against infringement. A functional self-assembled monolayer (SAM) of organic thiol on a gold surface has been employed as an efficient approach to control concomitant nucleation of such flexible drugs. The crystallization on a SAM surface is mostly kinetically driven and often leads to the nucleation of novel metastable forms. Spectroscopic, thermal analysis and X-ray diffraction studies reveal that a previously unknown, sixth form of the drug nucleates on the designed SAM surface.
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Affiliation(s)
- Pranita Bora
- Department of Chemical Sciences, Tezpur University, Tezpur, 784028, Assam, India
| | - Basanta Saikia
- Department of Chemical Sciences, Tezpur University, Tezpur, 784028, Assam, India
| | - Bipul Sarma
- Department of Chemical Sciences, Tezpur University, Tezpur, 784028, Assam, India
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8
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Tarai A, Baruah JB. Separation or combination of non-covalently linked partners provides polymorphs of N-(aryl)-2-(propan-2-ylidene)hydrazine carbothioamides. CrystEngComm 2019. [DOI: 10.1039/c8ce02000k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Polymorphs of N-(2-methoxyphenyl)-2-(propan-2ylidene)hydrazine carbothioamide and N-(4-nitrophenyl)-2-(propan-2-ylidene)hydrazine carbothioamide differing in homomeric assemblies are described.
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Affiliation(s)
- Arup Tarai
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati -781 039
- India
| | - Jubaraj Bikash Baruah
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati -781 039
- India
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9
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Bhandary S, Panini P, Chopra D. Evaluating the importance of fractional Z′ polymorphs in a trifluoromethylated N, N′-diphenyloxalamide derivative. CrystEngComm 2019. [DOI: 10.1039/c8ce02163e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A curious case of crystal dimorphism reveals an adjusted fractional number of molecules in their respective crystallographic asymmetric units.
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Affiliation(s)
- Subhrajyoti Bhandary
- Crystallography and Crystal Chemistry Laboratory
- Department of Chemistry
- Indian Institute of Science Education and Research Bhopal
- Bhopal-462066
- India
| | - Piyush Panini
- Crystallography and Crystal Chemistry Laboratory
- Department of Chemistry
- Indian Institute of Science Education and Research Bhopal
- Bhopal-462066
- India
| | - Deepak Chopra
- Crystallography and Crystal Chemistry Laboratory
- Department of Chemistry
- Indian Institute of Science Education and Research Bhopal
- Bhopal-462066
- India
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10
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Samie A, Salimi A. Conformational variation of ligands in mercury halide complexes; high and low Z′ structures. CrystEngComm 2019. [DOI: 10.1039/c9ce00185a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Small changes in the ligand resulted in a conformational variation of LPy to LPz which led to high and low Z′ structures in the corresponding metal complexes.
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Affiliation(s)
- Ali Samie
- Department of Chemistry
- Faculty of Science
- Ferdowsi University of Mashhad
- Mashhad
- Iran
| | - Alireza Salimi
- Department of Chemistry
- Faculty of Science
- Ferdowsi University of Mashhad
- Mashhad
- Iran
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11
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Liu Y, Jia L, Wu S, Xu S, Zhang X, Jiang S, Gong J. Polymorphism and molecular conformations of nicosulfuron: structure, properties and desolvation process. CrystEngComm 2019. [DOI: 10.1039/c8ce02074d] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nine solid forms of nicosulfuron were found for the first time and their structures and properties were studied in detail.
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Affiliation(s)
- Yu Liu
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Lina Jia
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Songgu Wu
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Shijie Xu
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Xu Zhang
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Shuang Jiang
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
| | - Junbo Gong
- State Key Laboratory of Chemical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- P. R. China
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12
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Boeré RT, Hill NDD. High Z′ structures of 1,2,3,5-dithiadiazolyls and of 1,2,3,5-diselenadiazolyls containing the first structurally characterized monomeric diselenadiazolyls. CrystEngComm 2017. [DOI: 10.1039/c7ce00863e] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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13
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Yang F, Yan CX, Yang X, Zhou DG, Zhou PP. Fenamic acid crystal with two asymmetric units (Z′ = 2): why Z′ = 2 rather than Z′ = 1. CrystEngComm 2017. [DOI: 10.1039/c6ce02646j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Steed KM, Steed JW. Packing problems: high Z' crystal structures and their relationship to cocrystals, inclusion compounds, and polymorphism. Chem Rev 2015; 115:2895-933. [PMID: 25675105 DOI: 10.1021/cr500564z] [Citation(s) in RCA: 247] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Kirsty M Steed
- †SAgE Faculty, Newcastle University, Devonshire Building, Newcastle upon Tyne NE1 7RU, United Kingdom
| | - Jonathan W Steed
- ‡Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
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15
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Sridhar B, Nanubolu JB, Ravikumar K. The first polymorph in the family of nucleobases: a second form of cytosine. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2015; 71:128-35. [DOI: 10.1107/s2053229615000492] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 01/09/2015] [Indexed: 11/11/2022]
Abstract
A new polymorph of cytosine, C4H5N3O, is reported half a century after the report of its first known crystal structure [Barker & Marsh (1964).Acta Cryst.17, 1581–1587]. Cytosine thus provides the first polymorphic example in the category of parent nucleobases. The new form, denoted (Ib), was observed unexpectedly during an attempt to cocrystallize cytosine with catechol. Form (Ib) crystallizes in the orthorhombic centrosymmetric space groupPccnwith two molecules in the asymmetric unit. The previously known form, denoted (Ia), crystallizes in the orthorhombic noncentrosymmetric space groupP212121. The cytosine molecule is planar in both forms. Hydrogen-bonding interactions are also similar for both forms. Infinite one-dimensional ribbons composed of cytosine base-pair dimers inR22(8) arrangements are observed in both (Ia) and (Ib). However, the way that the ribbons are packed differs in (Ia) and (Ib). This appears to guide the centrosymmetricversusnoncentrosymmetric space-group selection through the formation of an inversion-related motif in polymorph (Ib) and a helical propagation in polymorph (Ia). A few selected polymorphic systems have been gathered from the Cambridge Structural Database to understand possible structural features responsible for achiral molecules adopting centro- and noncentrosymmetric space groups.
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16
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Mir NA, Dubey R, Tothadi S, Desiraju GR. Combinatorial crystal synthesis of ternary solids based on 2-methylresorcinol. CrystEngComm 2015. [DOI: 10.1039/c5ce01280e] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cocrystallization experiments of 2-methylresorcinol with several N-bases were performed to identify selective and preferred crystallization routes in relevant structural landscapes.
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Affiliation(s)
- Niyaz A. Mir
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560 012, India
| | - Ritesh Dubey
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560 012, India
| | - Srinu Tothadi
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560 012, India
| | - Gautam R. Desiraju
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560 012, India
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17
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Conformational and crystal energetics of a polymorphic cyclized product of Napafenac: The Z′ and crystal stability correlation. J Mol Struct 2014. [DOI: 10.1016/j.molstruc.2013.10.061] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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18
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Krasnopolski M, Seidel RW, Goddard R, Breidung J, Winter MV, Devi A, Fischer RA. A Z′=6 crystal structure of (E)-N,N′-dicyclohexylacetamidine. J Mol Struct 2013. [DOI: 10.1016/j.molstruc.2012.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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19
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Nath B, Baruah JB. Polymorphism and porosity in 4-[(4-hydroxy-3,5-dimethylphenyl)(5-methyl-1H-imidazol-4-yl)methyl]-2,6-dimethylphenol. CrystEngComm 2013. [DOI: 10.1039/c3ce40407b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Bajpai A, Natarajan P, Venugopalan P, Moorthy JN. Crystal Engineering: Lattice Inclusion Based on O–H···O Hydrogen-Bonded Self-Assembly and Guest-Induced Structural Mimicry. J Org Chem 2012; 77:7858-65. [DOI: 10.1021/jo3010292] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alankriti Bajpai
- Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
| | - Palani Natarajan
- Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
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Lemmerer A, Fernandes MA. Adventures in co-crystal land: high Z′, stoichiometric variations, polymorphism and phase transitions in the co-crystals of four liquid and solid cyclic carboxylic acids with the supramolecular reagent isonicotinamide. NEW J CHEM 2012. [DOI: 10.1039/c2nj40186j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Sanphui P, Sarma B, Nangia A. Phase Transformation in Conformational Polymorphs of Nimesulide. J Pharm Sci 2011; 100:2287-99. [DOI: 10.1002/jps.22464] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 09/10/2010] [Accepted: 12/01/2010] [Indexed: 11/06/2022]
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24
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Das D, Jacobs T, Pietraszko A, Barbour LJ. Anomalous thermal expansion of an organic crystal--implications for elucidating the mechanism of an enantiotropic phase transformation. Chem Commun (Camb) 2011; 47:6009-11. [PMID: 21468434 DOI: 10.1039/c1cc10716j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two enantiotropic polymorphs of a dumbbell shaped molecule possess similar packing arrangements, in principle, but one of the polymorphs shows anomalously anisotropic thermal expansion while the other does not.
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Affiliation(s)
- Dinabandhu Das
- Department of Chemistry, University of Stellenbosch Private bag XI, Stellenbosch, South Africa
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25
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Thakuria R, Sarma B, Nangia A. Supramolecular networks of a H-shaped aromatic phenolhost. NEW J CHEM 2010. [DOI: 10.1039/b9nj00234k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Kalita D, Sarma R, Baruah JB. Formation of symmetry non-equivalent molecules in urea and carbamate derivatives: the role of anion. CrystEngComm 2009. [DOI: 10.1039/b815962a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Das D, Barbour LJ. Polymorphism of a Hexa-host: Isolation of Four Different Single-Crystal Phases by Melt Crystallization. J Am Chem Soc 2008; 130:14032-3. [DOI: 10.1021/ja804940v] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dinabandhu Das
- Department of Chemistry, University of Stellenbosch, Stellenbosch, 7600 South Africa
| | - Leonard J. Barbour
- Department of Chemistry, University of Stellenbosch, Stellenbosch, 7600 South Africa
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28
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Abstract
Polymorphs are different crystalline modifications of the same chemical substance. When different conformers of the same molecule occur in different crystal forms, the phenomenon is termed conformational polymorphism. Occasionally, more than one conformer is present in the same crystal structure. The influence of molecular conformation changes on the formation and stability of polymorphs is the focus of this Account. X-ray crystal structures of conformational polymorphs were analyzed to understand the interplay of intramolecular (conformer) and intermolecular (lattice) energy in the crystallization and stability of polymorphs. Polymorphic structures stabilized by strong O-H...O/N-H...O hydrogen bonds, weak C-H...O interactions, and close packing were considered. 4,4-Diphenyl-2,5-cyclohexadienone (1) and bis(p-tolyl) ketone p-tosylhydrazone (3) are prototypes of C-H...O and N-H...O hydrogen-bonded structures. Distance-angle scatter plots of O-H...O and C-H...O hydrogen bonds extracted from the Cambridge Structural Database indicate that polymorphs with a larger number of symmetry-independent molecules (high Z') generally have better interactions when compared with the polymorphs with lower Z' values, with the implication that these symmetry-independent molecules have different conformations. Since molecular conformer (E(conf)) and crystal lattice (U(latt)) energy differences are of the same magnitude in organic crystals (typically <5 kcal mol(-1)), situations wherein these two factors compensate or cancel one another are illustrative. Calculation of conformer and lattice energies using Gaussian 03 and Cerius(2) in 23 recently published polymorph sets shows that a strained conformer (higher E(conf)) is stabilized by stronger interactions or better crystal packing (lower U(latt)) in two-thirds of the cases, whereas there is no energy balance in the remaining structures. Organic molecules with flexible torsions and low-energy conformers have a greater likelihood of exhibiting polymorphism because (1) different conformations lead to new hydrogen-bonding and close-packing modes and (2) the tradeoff reduces the total energy difference between alternative crystal structures. As a test case, polymorph promiscuity in fuchsones (6) is related to the conformational diversity at the exo-methylene phenyl rings and the small energy difference computed for dimethyl fuchsone polymorphs. These ideas find application in the design of putative pharmaceutical polymorphs and crystal structure prediction.
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Affiliation(s)
- Ashwini Nangia
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
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29
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Reddy LS, Bhatt PM, Banerjee R, Nangia A, Kruger GJ. Variable-Temperature Powder X-ray Diffraction of Aromatic Carboxylic Acid and Carboxamide Cocrystals. Chem Asian J 2007; 2:505-13. [PMID: 17441188 DOI: 10.1002/asia.200600359] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effect of temperature on the cocrystallization of benzoic acid (BA), pentafluorobenzoic acid (FBA), benzamide (BAm), and pentafluorobenzamide (FBAm) is examined in the solid state. BA and FBA formed a 1:1 complex 1 at ambient temperature by grinding with a mortar and pestle. Grinding FBA and BAm together resulted in partial conversion into the 1:1 adduct 2 at 28 degrees C and complete transformation into the product cocrystal at 78 degrees C. Further heating (80-100 degrees C) and then cooling to room temperature gave a different powder pattern from that of 2. BAm and FBAm hardly reacted at ambient temperature, but they afforded the 1:1 cocrystal 3 by melt cocrystallization at 110-115 degrees C. Both BA+FBAm (4) and BA+BAm (5) reacted to give new crystalline phases upon heating, but the structures of these products could not be determined owing to a lack of diffraction-quality single crystals. The stronger COOH and CONH2 hydrogen-bonding groups of FBA and FBAm yielded the equimolar cocrystal 6 at room temperature, and heating of these solids to 90-100 degrees C gave a new crystalline phase. The X-ray crystal structures of 1, 2, 3, and 6 are sustained by the acid-acid/amide-amide homosynthons or acid-amide heterosynthon, with additional stabilization from phenyl-perfluorophenyl stacking in 1 and 3. The temperature required for complete transformation into the cocrystal was monitored by in situ variable-temperature powder X-ray diffraction (VT-PXRD), and formation of the cocrystal was confirmed by matching the experimental peak profile with the simulated diffraction pattern. The reactivity of H-bonding groups and the temperature for cocrystallization are in good agreement with the donor and acceptor strengths of the COOH and CONH2 groups. It was necessary to determine the exact temperature range for quantitative cocrystallization in each case because excessive heating caused undesirable phase transitions.
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Affiliation(s)
- L Sreenivas Reddy
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
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