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Patyk-Kaźmierczak E, Izquierdo-Ruiz F, Lobato A, Kaźmierczak M, Moszczyńska I, Olejniczak A, Recio JM. The curious case of proton migration under pressure in the malonic acid and 4,4'-bipyridine cocrystal. IUCRJ 2024; 11:168-181. [PMID: 38275161 PMCID: PMC10916288 DOI: 10.1107/s2052252524000344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 01/09/2024] [Indexed: 01/27/2024]
Abstract
In the search for new active pharmaceutical ingredients, the precise control of the chemistry of cocrystals becomes essential. One crucial step within this chemistry is proton migration between cocrystal coformers to form a salt, usually anticipated by the empirical ΔpKa rule. Due to the effective role it plays in modifying intermolecular distances and interactions, pressure adds a new dimension to the ΔpKa rule. Still, this variable has been scarcely applied to induce proton-transfer reactions within these systems. In our study, high-pressure X-ray diffraction and Raman spectroscopy experiments, supported by DFT calculations, reveal modifications to the protonation states of the 4,4'-bipyridine (BIPY) and malonic acid (MA) cocrystal (BIPYMA) that allow the conversion of the cocrystal phase into ionic salt polymorphs. On compression, neutral BIPYMA and monoprotonated (BIPYH+MA-) species coexist up to 3.1 GPa, where a phase transition to a structure of P21/c symmetry occurs, induced by a double proton-transfer reaction forming BIPYH22+MA2-. The low-pressure C2/c phase is recovered at 2.4 GPa on decompression, leading to a 0.7 GPa hysteresis pressure range. This is one of a few studies on proton transfer in multicomponent crystals that shows how susceptible the interconversion between differently charged species is to even slight pressure changes, and how the proton transfer can be a triggering factor leading to changes in the crystal symmetry. These new data, coupled with information from previous reports on proton-transfer reactions between coformers, extend the applicability of the ΔpKa rule incorporating the pressure required to induce salt formation.
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Affiliation(s)
- Ewa Patyk-Kaźmierczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Fernando Izquierdo-Ruiz
- MALTA-Consolider Team and Departamento de Química Física, University Complutense of Madrid, Avda. de Séneca, 2 Ciudad Universitaria, Madrid 28040, Spain
| | - Alvaro Lobato
- MALTA-Consolider Team and Departamento de Química Física, University Complutense of Madrid, Avda. de Séneca, 2 Ciudad Universitaria, Madrid 28040, Spain
| | - Michał Kaźmierczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Ida Moszczyńska
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Anna Olejniczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - J. Manuel Recio
- MALTA-Consolider Team and Departamento de Química Física y Analítica, University of Oviedo, Julián Clavería n° 8, Oviedo 33006, Spain
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Malec LM, Brela MZ, Stadnicka KM. Ab Initio Study of H-Bond Dynamics in Three-Component Crystals Comprising (DABCOH + ) n Polycationic Chains. Chemphyschem 2023; 24:e202200517. [PMID: 36213982 DOI: 10.1002/cphc.202200517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/06/2022] [Indexed: 11/16/2022]
Abstract
In this work, the dynamic character of hydrogen-bond (H-bond) networks in two three-component crystals comprising polycationic chains was described. The first studied system was 1,4-diazabicyclo[2.2.2]octan-1-ium (DABCOH+ ) sulfamate monohydrate, known for its large negative linear compressibility. The second analyzed material was the newly obtained polar salt co-crystal: 1,4-diazabicyclo[2.2.2]octan-1-ium sulfamate urea. X-ray diffraction measurements enabled us to study the H-bond systems in both crystals using the graph set analysis. Obtained structures served as the initial models for Born-Oppenheimer molecular dynamics computations. A detailed study of intermolecular interactions and power spectra was conducted. The analysis of time and space correlations between the changes in H-bonds enabled the detection of proton transfer occurring in both systems at 300 K. Further study of those dynamic phenomena was done using the Energy Decomposition Analysis for selected trajectory fragments. Our work should improve the understanding of dielectric and ferroelectric properties of hybrid organic-inorganic materials.
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Affiliation(s)
- Leszek M Malec
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - Mateusz Z Brela
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - Katarzyna M Stadnicka
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
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Budzianowski A, Petřiček V, Katrusiak A. Metal-free enantiomorphic perovskite [dabcoH 2] 2+[H 3O] +Br - 3 and its one-dimensional polar polymorph. IUCRJ 2022; 9:544-550. [PMID: 36071811 PMCID: PMC9438492 DOI: 10.1107/s2052252522006406] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 06/20/2022] [Indexed: 06/15/2023]
Abstract
The structure and stoichiometry of a new metal-free and ammonium-free compound [dabcoH2]2+H3O+Br- 3 (where [dabcoH2]2+ = 1,4-di-aza-bicyclo-[2.2.2]octane dication) correspond to the general formula ABX 3 characteristic of perovskites. In enantiomorphic trigonal polymorph α of [dabcoH2]2+H3O+Br- 3, the corner-sharing [H3O]Br6 octahedra combine into a 3D framework embedding [dabcoH2]2+ dications in pseudo-cubic cages. In the more dense polymorph β, the face-sharing [H3O]Br6 octahedra form 1D polyanionic columns separated by [dabcoH2]2+ dications. These different topologies correlate with different crystal fields around the cations and their different disorder types: orientational disorders of [dabcoH2]2+ dications and H3O+ cations in polymorph α and positional disorder of [H3O]+ cations in polymorph β. The orientational disorder increases the lengths of OH⋯Br hydrogen bonds in polymorph α, but NH⋯Br distances of ordered dabcoH2 dications are longer in polymorph β. The presence of polar [H3O]+ cations in [dabcoH2]2+H3O+Br- 3 polymorphs offers additional polarizability of the centres compared with analogous metal-free [dabcoH2]2+[NH4]+Br- 3 perovskite.
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Affiliation(s)
- Armand Budzianowski
- National Centre for Nuclear Research, Andrzeja Sołtana 7, Otwock, Świerk 05-400, Poland
| | - Vaclav Petřiček
- Institute of Physics; Department of Structure Analysis, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, Prague 6 16253, Czech Republic
| | - Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University in Poznań, Umultowska 89 b, Poznań 61-614, Poland
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Morita H, Tsunashima R, Nishihara S, Inoue K, Omura Y, Suzuki Y, Kawamata J, Hoshino N, Akutagawa T. Ferroelectric Behavior of a Hexamethylenetetramine‐Based Molecular Perovskite Structure. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Hagino Morita
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Ryo Tsunashima
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
- Chemistry CourseFaculty of ScienceYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Sadafumi Nishihara
- Graduate School of ScienceHiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima 739-8526 Japan
| | - Katsuya Inoue
- Graduate School of ScienceHiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima 739-8526 Japan
| | - Yuriko Omura
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Yasutaka Suzuki
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Jun Kawamata
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Norihisa Hoshino
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM)Tohoku University Sendai 980-8577 Japan
| | - Tomoyuki Akutagawa
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM)Tohoku University Sendai 980-8577 Japan
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Morita H, Tsunashima R, Nishihara S, Inoue K, Omura Y, Suzuki Y, Kawamata J, Hoshino N, Akutagawa T. Ferroelectric Behavior of a Hexamethylenetetramine‐Based Molecular Perovskite Structure. Angew Chem Int Ed Engl 2019; 58:9184-9187. [DOI: 10.1002/anie.201905087] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Indexed: 11/12/2022]
Affiliation(s)
- Hagino Morita
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Ryo Tsunashima
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
- Chemistry CourseFaculty of ScienceYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Sadafumi Nishihara
- Graduate School of ScienceHiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima 739-8526 Japan
| | - Katsuya Inoue
- Graduate School of ScienceHiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima 739-8526 Japan
| | - Yuriko Omura
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Yasutaka Suzuki
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Jun Kawamata
- Graduate School of Sciences and Technology for InnovationYamaguchi University Yoshida 1677-1 Yamaguchi 753-8512 Japan
| | - Norihisa Hoshino
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM)Tohoku University Sendai 980-8577 Japan
| | - Tomoyuki Akutagawa
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM)Tohoku University Sendai 980-8577 Japan
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6
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Han XB, Hu P, Shi C, Zhang W. Structural phase transitions and dielectric transitions in a 1,4-diazabicyclo[2.2.2]octane (dabco) based organic crystal. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2016.07.113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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7
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Han XB, Hu P, Shi C, Zhang W. 1,4-Diazabicyclo[2.2.2]octane-based disalts showing non-centrosymmetric structures and phase transition behaviors. CrystEngComm 2016. [DOI: 10.1039/c5ce02066b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Anioła M, Katrusiak A. Pressure-preferred symmetric reactions of 4,4′-bipyridine hydrobromide. CrystEngComm 2016. [DOI: 10.1039/c6ce00356g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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The structure and dielectric properties of ionic compounds with flexible ammonium moiety. CHINESE CHEM LETT 2015. [DOI: 10.1016/j.cclet.2014.10.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Ning WH, Zhai L, Ren XM. Two-step dielectric anomalies coupled with structural phase transitions in a co-crystal of 1,4-diazabicyclo[2.2.2]octane and 4,4′-biphenol. RSC Adv 2014. [DOI: 10.1039/c4ra03681f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Two-step dielectric anomalies appear in co-crystal of 1,4-diazabicyclo[2.2.2]octane (DABCO) and 4,4′-biphenol which are coupled with structural phase transitions related to the disorder–order transformation of DABCO molecules.
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Affiliation(s)
- Wei-Hua Ning
- State Key Laboratory of Materials-Oriented Chemical Engineering and College of Science
- Nanjing University of Technology
- Nanjing 210009, China
- College of Materials Science and Engineering
- Nanjing University of Technology
| | - Lu Zhai
- State Key Laboratory of Materials-Oriented Chemical Engineering and College of Science
- Nanjing University of Technology
- Nanjing 210009, China
- College of Materials Science and Engineering
- Nanjing University of Technology
| | - Xiao-Ming Ren
- State Key Laboratory of Materials-Oriented Chemical Engineering and College of Science
- Nanjing University of Technology
- Nanjing 210009, China
- College of Materials Science and Engineering
- Nanjing University of Technology
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11
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Barczyński P, Dega-Szafran Z, Katrusiak A, Szafran M. Hydrogen bonds and electrostatic interactions in the 1:1 complex of DABCO di-betaine with squaric acid: Crystallographic, theoretical and spectroscopic studies. J Mol Struct 2012. [DOI: 10.1016/j.molstruc.2011.11.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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12
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Nowicki W, Olejniczak A, Andrzejewski M, Katrusiak A. Reverse sequence of transitions in prototypic relaxor 1,4-diazabicyclo[2.2.2]octane. CrystEngComm 2012. [DOI: 10.1039/c2ce25359c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Andrzejewski M, Olejniczak A, Katrusiak A. Remote halogen switch of amine hydrophilicity. CrystEngComm 2012. [DOI: 10.1039/c2ce25401h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Barczyński P, Dega-Szafran Z, Katrusiak A, Szafran M. The 1:2:1 adduct of DABCO dication, hydrogen squarate and water molecules studied by X-ray diffraction and FTIR spectroscopy. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.05.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Barczyński P, Dega-Szafran Z, Katrusiak A, Szafran M. Unusual molecular structure of the 1:2.5:2 complex of DABCO di-betaine (1,4-diacetate-1,4-diazoniumbicyclo[2.2.2]octane) with p-hydroxybenzoic acid and water. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.03.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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16
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Szafrański M. Bias-Field and Pressure Effects on the One-Dimensional Dielectric Response in N−H+···N Hydrogen-Bonded 1,4-Diazabicyclo[2.2.2]octane Hydrobromide Crystal. J Phys Chem B 2009; 113:9479-88. [DOI: 10.1021/jp900602p] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marek Szafrański
- Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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17
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Au RHW, Jennings MC, Puddephatt RJ. Binuclear Platinum(IV) Complexes with Bridging Amidoalkyl Groups and Their Self-Assembly through Hydrogen Bonding. Organometallics 2009. [DOI: 10.1021/om9001878] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Richard H. W. Au
- Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7
| | - Michael C. Jennings
- Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7
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18
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Au RHW, Jennings MC, Puddephatt RJ. Organoplatinum(IV) Complexes with Amide Groups: Supramolecular Structure as a Function of Ligand Flexibility. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200900030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Richard H. W. Au
- Department of Chemistry, University of Western Ontario, London, N6A 5B7, Canada, Fax: +1‐519‐661‐3022
| | - Michael C. Jennings
- Department of Chemistry, University of Western Ontario, London, N6A 5B7, Canada, Fax: +1‐519‐661‐3022
| | - Richard J. Puddephatt
- Department of Chemistry, University of Western Ontario, London, N6A 5B7, Canada, Fax: +1‐519‐661‐3022
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19
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Spectroscopic studies, crystal structures and antimicrobial activities of a new lasalocid 1-naphthylmethyl ester. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2008.04.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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Podsiadło M, Katrusiak A. Competing Patterns of Weak Directional Forces in Pressure-Frozen CH2ClI and CH2I2. J Phys Chem B 2008; 112:5355-62. [DOI: 10.1021/jp8006574] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marcin Podsiadło
- Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
| | - Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
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21
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Katrusiak A. High-pressure crystallography. Acta Crystallogr A 2007; 64:135-48. [PMID: 18156679 DOI: 10.1107/s0108767307061181] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 11/20/2007] [Indexed: 11/10/2022] Open
Abstract
Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure-property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined.
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Affiliation(s)
- Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland.
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22
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Boldyreva EV. High-pressure diffraction studies of molecular organic solids. A personal view. Acta Crystallogr A 2007; 64:218-31. [DOI: 10.1107/s0108767307065786] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 12/05/2007] [Indexed: 11/10/2022] Open
Abstract
This paper discusses the trends in the experimental studies of molecular organic solids at high pressures by diffraction techniques. Crystallization of liquids, crystallization from solutions and solid-state transformations are considered. Special attention is paid to the high-pressure studies of pharmaceuticals and of biomimetics.
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Katrusiak A, Szafrański M. Disproportionation of Pyrazine in NH+···N Hydrogen-Bonded Complexes: New Materials of Exceptional Dielectric Response. J Am Chem Soc 2006; 128:15775-85. [PMID: 17147387 DOI: 10.1021/ja0650192] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Centrosymmetric pyrazinium NH+...N bonded complexes allow their dielectric properties to be analyzed separately from the bulk ferroelectric polarization observed in the noncentrosymmetric DABCO monosalts. The method of dielectric permittivity measurements has been employed for monitoring polarization fluctuations generated by proton transfers in the NH+...N bonded linear polycations. The revealed dielectric response of [C4H5N2]+BF4- and [C4H5N2]+ClO4- cannot be reconciled with the centrosymmetric symmetry of their structures, but suggests formation of polar defects or nanoregions. Unique transformations of the pyrazine [C4H5N2]+BF4- complex between linear NH+...N hydrogen-bonded polycationic aggregates antiparallel in phase gamma, perpendicular chains in phase beta, and with NH+...N bonds broken in phase alpha have been observed. The [C4H5N2]+ClO4- and [C4H5N2]+BF4- complexes as grown at 290 K are isostructural in orthorhombic phase , space group Pbcm, with linear polycationic chains arranged antiparallel. On heating, the tetrafluoroborate and perchlorate salts each undergoes two first-order phase transitions at similar temperatures about 340-360 K, while on cooling only one phase transition has been observed. An extremely unique sequence of two phase transitions subsequently lowering the symmetry of the [C4H5N2]+BF4- crystal when temperature is increased has been evidenced: the orthorhombic phase heated above 343 K transforms into the monoclinic C2/c-symmetric phase beta, in which the NH+...N bonded linear chains assume perpendicular arrangement; and at about 353-357 K the anions and cations adopt a typical ionic-crystal packing without homonuclear NH+...N hydrogen bonds in a still lower-symmetry monoclinic P21/n-symmetric structure. The exceptional perpendicular arrangement of the linear NH+...N bonded chains in phase beta constitutes a unique system where polarization of small regions can assume various orientations within a plane, depending on the H+ sites. No phase transitions or anomalous dielectric response were observed in the NH+...O bonded [C4H5N2]+NO3- complex. The unprecedented structure-property relations of the pyrazinium complexes fully confirm the role of the NH+...N bond transformations for the dielectric response of analogous DABCO ferroelectrics.
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Affiliation(s)
- Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland.
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