High-Pressure-Induced Polymorphic Transformation of Maleic

Article pubs.acs.org/JPCC

High-Pressure-Induced Polymorphic Transformation of Maleic Hydrazide Kai Wang,† Jing Liu,‡ Ke Yang,§ Bingbing Liu,† and Bo Zou*,† †

State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P. R. China Beijing Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, P. R. China § Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, P. R. China ‡

ABSTRACT: Maleic hydrazide, a unique example of polymorphic structures, was analyzed at pressure up to 5 GPa using in situ high-pressure Raman scattering and synchrotron X-ray diffraction techniques. Changes in the Raman spectra at 2 GPa indicate that a pressure-induced phase transition is occurring. The transition was further analyzed with angle dispersive X-ray diffraction, which demonstrated that maleic hydrazide underwent a polymorphic transformation from the form III to the form II. Moreover, the observed transformation was partially reversible when the system was brought back to ambient pressure. This work suggests that the high-pressure polymorphic transformation is caused by changes in the hydrogen-bonded ribbons which lead to supramolecular rearrangements in the crystal structure.

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INTRODUCTION A molecule that exists in two or more crystalline forms with different conformations and/or arrangements in the crystal lattice is defined as polymorphic,1 and this is applicable in several different research areas including electronics, explosives, and agrochemical and pharmaceutical industry. These polymorphisms in the different molecular arrangements can vary in melting point, stability, solubility, and density.2 Hydrogen bonding, a critical noncovalent interaction, plays a key role in the phenomenon of polymorphism due to its directionality, saturability, and reversibility.3 An ideal experimental system to study hydrogen-bonded in polymorphisms is high pressure since it can induce significant variations in molecular arrangements and hydrogen bonding.4 Besides, the balance between van der Waals interactions and hydrogen bonding can be changed easily by external pressure, which may potentially result in structural transitions.5 High external pressures may affect also photochemical behavior of crystals. For example, the photoswitching properties of azobenzene also were shown to depend on the applied external pressure.6 Investigating the hydrogen-bond network in polymorphic compounds utilizing high pressure can provide more information about the hydrogen bonding and also assist in the study of transformations between existing polymorphs as well as the generation of new polymorphs.7 Therefore, studying the structural stability of polymorphs under high pressure is an important feature in physics, chemistry, and pharmaceutics. Over the past 10 years, many known polymorphic systems were examined by high pressure, such as pharmaceuticals,8 amino acids,9 and energetic materials.10 For example, powdered © 2014 American Chemical Society

paracetamol is converted from form I into form II under pressure greater than 4 GPa.11 At 4 GPa of pressure, the γ form of pyrazinamide transitions to the β phase while the α and δ forms maintain the original crystal symmetry.12 When amino acids crystals that were formed under ambient pressure conditions are compressed by high pressure, several systems such as serine,13 alanine,14 glycine,15 and cysteine16 exhibit polymorphisms. Our group also has carried out a series studies on pressure-induced phase transition of hydrogen-bonded supramolecular structures in recent years.17−19 As is expected, high pressure has the unrivalled ability to modify crystal structures, and hydrogen bond rearrangements are essential in these polymorphic transformations. As a consequence, further studies are needed to unravel the regulatory mechanisms induced at high pressure in crystal structures and the intermolecular interactions in the polymorphic systems. It is of considerable interest to investigate the molecular and crystal structures of maleic hydrazide (3-hydroxypyridazin-6one, MH), 20 a well-known plant growth inhibitor in agriculture.21 There are many studies on the tautomerism of MH under various experimental conditions.20,22−24 All of these studies have conclude that the existence of MH exclusively as oxo−hydroxy tautomer. Cradwick suggested that MH molecules act like pyrimidine or purine analogue by base pair interactions with adenine or uracil and thymine.25 Katrusiak demonstrate that MH exists in three different polymorphic Received: January 20, 2014 Revised: March 21, 2014 Published: March 24, 2014 8122

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both thermal stability and chemical reactivity.29,30 The most reactive MH3 undergoes two phase transitions between 90 and 300 K, while the MH1 and MH2 are stable in this temperature region. The high reactivity and low thermal stability of MH3 can be responsible for the hydrogen bond arrangement and supramolecular aggregation in its crystal structure. Under ambient conditions, MH3 crystals form a monoclinic structure in the P21/n space group. As depicted in Figure 1b, these molecules are inclined to the mean plane (100) of the hydrogen-bonded ribbons. Additionally, an extensive study exploring the vibrational spectra of hydrogen bonds in MH3 has been conducted.23 Therefore, it is critical to understand the structural stability and changes of hydrogen-bonded supramolecular aggregates of MH3 under high pressure. In this study, we explored the pressure-induced polymorphic transformation of MH3 with in situ synchrotron X-ray diffraction and high-pressure Raman spectroscopy. The highpressure structural data were obtained using angle dispersive Xray diffraction (ADXRD) patterns at high-intensity synchrotron radiation.31 To further analyze the differences in the molecular arrangements and the interactions of the hydrogen bonds, the powerful high-pressure Raman spectroscopy was utilized.32 In this study, we provide a more detailed understanding of intermolecular interactions and polymorphism phenomenon, which has practical advantages in crystal engineering and pharmacy industry.

forms: a triclinic MH1 form and two monoclinic forms MH2 and MH3.26−28 Interestingly, the three polymorphs have a similar pattern of hydrogen bonds in their crystal structures: an O−H···O motif, which links endless chains molecules and are connected into ribbons of double chains through N−H···O interactions (Figure 1a). However, these polymorphs differ in

Figure 1. Hydrogen-bonded double-chain ribbon (a) and crystal structure of MH3 (b) at ambient pressure. The hydrogen bonds are indicated by dashed lines.

Figure 2. Raman spectra of MH3 at elevated pressures in the spectral regions (a) 50−200, (b) 200−1100, (c) 1100−1750, and (d) 2950−3400 cm−1. The arrows denote the appearing of new peaks, and the stars highlight the splitting of original peaks. 8123

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EXPERIMENTAL SECTION

The sample used for this study was purchased from Alfa Aesar Co. [purity 97%] and was used without further purification. The level of MH3 polymorphic purity was validated through the powder pattern by X-ray diffraction. Experiments were conducted at high pressure in a symmetric diamond anvil cell (DAC) containing 0.4 mm diamond culets. The sample cavity was generated by preindenting a T301 stainless steel gasket with diamonds followed by drilling to create a 0.15 mm diameter cavity. The diamond anvil cell was loaded with the powder samples using an argon pressure-transmitting medium. The pressures in DAC were measured using the ruby fluorescence technique.33 To avoid the diamond’s first-order Raman peak, we used a sapphire anvil cell to acquire highpressure Raman spectra near 1333 cm−1. High-pressure Raman spectra were measured in the standard backscattering geometry with the Acton SpectraPro 2500 spectrograph (500 mm focal length) equipped with a CCD that was cooled with liquid nitrogen (PyLoN:100B). The excitation source was a DPSS laser at 532 nm with the output power at 10 mW. ADXRD measurements were collected at the 4W2 HighPressure Station at the Beijing Synchrotron Radiation Facility (BSRF). Portions of the ADXRD experiments were conducted using the beamline 15U1 at the Shanghai Synchrotron Radiation Facility (SSRF). The diffraction data were collected using a monochromatic radiation at 0.6199 Å wavelength. The FIT2D software was used to integrate the XRD patterns.34 The reflex module in Materials Studio program was utilized to index and refine the XRD patterns (Accelrys Inc.). High-pressure experiments were conducted at standard room temperature.

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Figure 3. Frequency shift of the Raman modes as a function of pressure. The vertical dashed line marks the onset of discontinuity.

RESULTS AND DISCUSSION The observed MH3 Raman spectrum at ambient pressure observed by us agrees well with that reported by MorzykOciepa,23 so we made the assignments of Raman peaks on the basis of that result. In this work, the Raman spectra of MH3 were measured at pressure as great as 5 GPa. The MH3 Raman spectra at 50−200, 200−1100, 1100−1750, and 2950−3400 cm−1 at the various pressures are presented in Figures 2a−d, respectively. The simultaneous variations in many of the Raman modes demonstrate that at 2 GPa MH3 undergoes a structural transition. This new phase was stable and did not undergo any further changes at all higher pressures tested. The frequency shifts in the Raman modes demonstate the existence of the high-pressure phase and are shown in Figure 3. Around 2 GPa, several vibrational modes indicate a shift that is discontinuous while other modes suddenly have a change in their slopes. These observations are also accompanied by several new modes as well as existing modes starting to split. Although no crystal structure information can be determined from the highpressure Raman data, the observed spectra provide some insights into the structural features of high-pressure phase. It is well-known that the lattice modes of organic crystal are very sensitive to pressure-induced phase transition. The Raman spectrum of MH3 observed at ambient conditions consists of six lattice modes (61, 80, 96, 106, 113, and 145 cm−1). Figure 2a shows the evolution of these low-frequency modes at elevated pressures. At higher pressures, all lattice modes exhibit significant blue-shifts but at different rates. The lattice modes blue-shift is due to the reduction in the intermolecular distances, which results greater interaction among adjacent molecules.35,36 At 2 GPa, the spectrum shape changes abruptly,

which serves as evidence for the phase transition induced by increased pressure. Four new Raman peaks appear with gradually high intensity at 53, 74, 99, and 112 cm−1 (marked with arrows), and the intensity of the original peaks is distinctly reduced or disappears. Not only was there an increase in frequency in the new pattern of Raman peaks but also these peaks were preserved up to 5 GPa. The results from lattice modes provided strong evidence for the occurrence of pressureinduced phase transition at about 2 GPa. The changes of internal vibration modes of MH3 molecules also reveal the existence of this phase transition. We assigned these observed Raman peaks in the frequency range 200−3400 cm−1 to internal modes (Figures 2b−d). With increasing pressure, most of the internal modes started to gradually shift to higher frequencies. These frequencies are likely due to the reduction in the interatomic distances and the escalation of effective force constants.37,38 The most dramatic change in the spectrum was at 2 GPa, and several novel features were observed. The major changes occurred at 336 cm−1 with the split in the C−O in-plane bending mode, at 400 cm−1 with the ring torsion mode, at 986 cm−1 with the C−H out-of-plane bending mode, at 1146 cm−1 with the C−H in-plane bending mode, and finally at 1223 cm−1 with the O−H in-plane bending mode (marked with stars). These changes at 2 GPa are also accompanied by the emergence of five new modes at 209 420, 580, 722, and 3299 cm−1 (marked with arrows) along with the existing modes displaying discontinuity shifts. In addition, the intensity of some Raman peaks suddenly decreased at 2 GPa and even disappeared with increasing pressure. Compared with the vibrational frequencies of matrix-isolated MH,20 we can 8124

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conclude that the environment of molecules in MH3 crystal changed significantly after phase transition. In particular, there is a new peak at 3299 cm−1 observed at 2 GPa that is assigned to the N−H stretching mode. Since all N−H bonds are involved in hydrogen bond networks, the emerging of novel N−H modes suggests that there is a substantial rearrangement in the hydrogen bonds between the different chains. We notice that the stretching vibration at 3441 cm−1 of the N−H group in the MH monomers isolated from the Ar matrix.20 The appearance of the novel band at 3299 cm−1 could indicate the disruption in intermolecular N−H···O hydrogen-bond network at high pressures. The fact that this frequency does not exactly correspond to a free molecule indicates that some residual intermolecular hydrogen-bond interactions still exist in the structure of the new polymorph. Comparing the red-shift in the stretching frequency (142 cm−1) in the group of hydrogenbonded N−H with the stretching frequency of the group of free N−H, we can estimate39 at higher pressures that the strengths of these hydrogen bonds are weak. Moreover, with further increase of pressure, the new peak showed a continuous redshift up to 5 GPa. The pressure-induced red-shift agrees with generalized rules that pressure increases will decrease the weak and medium strength D−H···A bond stretching frequencies.40−44 In Figure 1, the crystal structure shows that the O−H and N−H groups of different molecules serve as proton donors and compete for the CO group of a third molecule as proton acceptor. Unlike other modes, the frequencies at 1386 cm−1 of the O−H in-plane bending mode is actually decreasing with increasing pressure. This red-shift at higher pressure is attributed to the strengthening of O−H···O hydrogen bond.40 That is to say, the hydrogen bond length of O−H···O and the distance between adjacent molecules along hydrogen-bonded chains decreased with increasing pressure. The strengthening of the O−H···O hydrogen bond implies that there is a reduction in the strength of the competing N−H···O bond. This is why at 1427 cm−1 the N−H bending mode exhibits blue-shift characteristics under high pressure. To further characterize this transition induced by increasing pressure, we performed high-pressure XRD measurement, which provides direct evidence of a phase transition. Figure 4 shows the X-ray diffraction patterns of MH3 with increasing pressures. With the increase in pressure, the diffraction peaks shift to greater angles, which is indicative of the unit cell volume becoming smaller. We noted that the largest shift is in the (200) diffraction peak, which is likely due to high levels a-axis compression. The anisotropic compression behavior is explained by the layered crystal packing. The planar hydrogen-bonded ribbons are arranged in layers parallel to the bcplane, while the majority of interactions among the various layers are predominately van der Waals interactions. With pressure increased to 2 GPa, the interlayer distance in the MH3 polymorph reduced from 3.20 to 2.98 Å. Therefore, as expected, the a-axis was the most compressed one. Around 2 GPa of pressure, significant changes in the XRD patterns indicate the start of a phase transition. As indicated by the arrows in Figure 4, the new XRD pattern appeared and greatly increased while the original XRD pattern decreased and disappeared completely around 2 GPa. The new pressureindcued phase is indexed to the monoclinic polymorphic form of MH2 with space group P21/c. The lattice constants from the indexing were a = 6.94(9) Å, b = 9.41(3) Å, c = 6.42(8) Å, and β = 102.6(7)°, with a unit cell volume V = 410.1(9) Å3. On further increase of pressure, the new MH2 phase remained

Figure 4. Representative ADXRD patterns at elevated pressures. Indications for a phase transition are marked by arrows.

stable and the interlayer distance reduced from 3.21 to 3.07 Å at 5 GPa, which was the highest pressure used in the XRD experiments. Therefore, the X-ray experiments conducted with increasing pressure confirmed the results from Raman experiments, demonstrating that MH3 undergoes a phase transition with pressure around 2 GPa. After the return to ambient pressure, the XRD pattern reveals that this MH3 → MH2 polymorphic transformation is partially reversible and most of the sample recovered to the original MH3 structure. The Rietveld quantitative phase analysis result in Figure 5 shows that the crystalline phases in the quenched

Figure 5. Quantitative phase analysis based on the Rietveld fit of the diffraction patterns collected on the quenched sample.

sample containing 68.3 wt % MH3 and 31.7 wt % MH2. The coexistence of the two phases on complete release of pressure can be interpreted by the similar hydrogen-bonded aggregates28 and the proximity in the energy of these two polymorphic forms.45 The Raman and X-ray results in this study illustrate a pressure-induced polymorphic transformation of MH3 → MH2. A question remained: what changes occur in the hydrogen-bonded ribbons with high pressure? With the 8125

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The Journal of Physical Chemistry C knowledge of the crystal structures, we proposed a mechanism for this pressure-induced polymorphic transformation. The application of pressure in the low pressure range mostly reduces the interlayer distance. With further increasing pressure, the layers in the structure slowly become unstable due to the disruption of the close packing balance and intermolecular interaction. At pressures approaching 2 GPa, the layered molecular planes cannot support the intermolecular interaction because of the increased energy of the interactions. Therefore, the hydrogen bonds of the aggregates rearranged to reduce the free energy, which results in the phase transition. As shown in Figure 6, the planar structure of hydrogen-bonded

ACKNOWLEDGMENTS

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REFERENCES

We thank anonymous reviewers for comments which significantly improved this paper. This work is supported by NSFC (Nos. 91227202, and 11204101), RFDP (No. 20120061130006), National Basic Research Program of China (No. 2011CB808200), and China Postdoctoral Science Foundation (NO. 2012M511327). Angle-dispersive XRD measurement was performed at beamline 4W2 beamline, Beijing Synchrotron Radiation Facility (BSRF), which is supported by Chinese Academy of Sciences (No. KJCX2-SWN20, KJCX2-SW-N03). Portions of this work were performed at the 15U1 at the Shanghai Synchrotron Radiation Facility (SSRF).

(1) Purohit, R.; Venugopalan, P. Polymorphism: An Overview. Resonance 2009, 14, 882−893. (2) Brog, J.-P.; Chanez, C.-L.; Crochet, A.; Fromm, K. M. Polymorphism, What It Is and How to Identify It: a Systematic Review. RSC Adv. 2013, 3, 16905−16931. (3) Steiner, T. The Hydrogen Bond in the Solid State. Angew. Chem., Int. Ed. 2002, 41, 49−76. (4) Sikka, S. K.; Sharma, S. M. The Hydrogen Bond under Pressure. Phase Transitions 2008, 81, 907−934. (5) Boldyreva, E. V. High-Pressure Studies of the Hydrogen Bond Networks in Molecular Crystals. J. Mol. Struct. 2004, 700, 151−155. (6) Singleton, T. A.; Ramsay, K. S.; Barsan, M. M.; Butler, I. S.; Barrett, C. J. Azobenzene Photoisomerization under High External Pressures: Testing the Strength of a Light-Activated Molecular Muscle. J. Phys. Chem. B 2012, 116, 9860−9865. (7) Fabbiani, F. P. A.; Allan, D. R.; David, W. I. F.; Moggach, S. A.; Parsons, S.; Pulham, C. R. High-Pressure Recrystallisationa Route to New Polymorphs and Solvates. CrystEngComm 2004, 6, 504−511. (8) Masson, P.; Tonello, C. Potential Applications of High Pressures in Pharmaceutical Science and Medicine. High Pressure Res. 2000, 19, 613−621. (9) Moggach, S.; Parsons, S.; Wood, P. High-Pressure Polymorphism in Amino Acids. Crystallogr. Rev. 2008, 14, 143−184. (10) Fabbiani, F. P. A.; Pulham, C. R. High-Pressure Studies of Pharmaceutical Compounds and Energetic Materials. Chem. Soc. Rev. 2006, 35, 932−942. (11) Boldyreva, E. V.; Shakhtshneider, T. P.; Ahsbahs, H.; Sowa, H.; Uchtmann, H. Effect of High Pressure on the Polymorphs of Paracetamol. J. Therm. Anal. Calorim. 2002, 68, 437−452. (12) Tan, X.; Wang, K.; Li, S. R.; Yuan, H. S.; Yan, T. T.; Liu, J.; Yang, K.; Liu, B. B.; Zou, G. T.; Zou, B. Exploration of the Pyrazinamide Polymorphism at High Pressure. J. Phys. Chem. B 2012, 116, 14441−14450. (13) Boldyreva, E. V.; Sowa, H.; Seryotkin, Y. V.; Drebushchak, T. N.; Ahsbahs, H.; Chernyshev, V.; Dmitriev, V. Pressure-Induced Phase Transitions in Crystalline l-Serine Studied by Single-Crystal and HighResolution Powder X-Ray Diffraction. Chem. Phys. Lett. 2006, 429, 474−478. (14) Staun Olsen, J.; Gerward, L.; Souza Filho, A. G.; Freire, P. T. C.; Mendes Filho, J.; Melo, F. E. A. High-Pressure X-Ray Diffraction of LALANINE Crystal. High Pressure Res. 2006, 26, 433−437. (15) Dawson, A.; Allan, D. R.; Belmonte, S. A.; Clark, S. J.; David, W. I. F.; McGregor, P. A.; Parsons, S.; Pulham, C. R.; Sawyer, L. Effect of High Pressure on the Crystal Structures of Polymorphs of Glycine. Cryst. Growth Des. 2005, 5, 1415−1427. (16) Moggach, S. A.; Allan, D. R.; Clark, S. J.; Gutmann, M. J.; Parsons, S.; Pulham, C. R.; Sawyer, L. High-Pressure Polymorphism in l-Cysteine: the Crystal Structures of l-Cysteine-III and l-Cysteine-IV. Acta Crystallogr., Sect. B 2006, 62, 296−309. (17) Yan, T. T.; Li, S. R.; Wang, K.; Tan, X.; Jiang, Z. M.; Yang, K.; Liu, B. B.; Zou, G. T.; Zou, B. Pressure-Induced Phase Transition in

Figure 6. Hydrogen bond geometries in MH3 and MH2. (a) Planar hydrogen bonds in MH3. (b) Distorted N−H···O hydrogen bonds in MH2 viewed along chain direction. (c) Planar O−H···O hydrogen bond and distorted N−H···O hydrogen bonds in MH2 viewed perpendicular to the molecular chain.

chains in MH3 is preserved while the initial N−H···O hydrogen bonds in the planar double-chain ribbons are converted into a zigzag arrangement after phase transition. That is to say, the hydrogen bonds between different chains were severely distorted and the geometry hydrogen bond parameters of N− H···O were significantly changed at transition point. The above vibrational analysis also indicated appearance of partially free N−H groups, suggested by emergence of vibrational frequencies of the stretching of the N−H and N−H out-ofplane modes similar to those observed in monomeric MH.20

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CONCLUSION We utilized Raman spectroscopy and synchrotron X-ray diffraction to study changes in MH3 crystal at high pressure. The dramatic changes in the Raman spectroscopy experiments indicate a significant phase transition at 2 GPa. This transition phase is stable up to 5 GPa, the highest pressure we investigated. The XRD experiments at high pressure confirmed the transition in MH3 and identified it a transformation from MH3 to MH2. This variation is likely attributed to the hydrogen bond distortion in N−H···O between the molecular chains. After decompression to ambient pressure, the quenched sample contained 68.3 wt % MH3 and 31.7 wt % MH2. The data presented in this study provide further insights into the rearrangements of hydrogen bonds and polymorphic transformations that occur at high pressure.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (B.Z.). Notes

The authors declare no competing financial interest. 8126

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N-H...O Hydrogen-Bonded Molecular Crystal Oxamide. J. Phys. Chem. B 2012, 116, 9796−9802. (18) Wang, K.; Duan, D.; Wang, R.; Liu, D.; Tang, L.; Cui, T.; Liu, B.; Cui, Q.; Liu, J.; Zou, B.; Zou, G. Pressure-Induced Phase Transition in Hydrogen-Bonded Supramolecular Adduct Formed by Cyanuric Acid and Melamine. J. Phys. Chem. B 2009, 113, 14719− 14724. (19) Wang, R.; Li, S.; Wang, K.; Duan, D.; Tang, L.; Cui, T.; Liu, B.; Cui, Q.; Liu, J.; Zou, B.; Zou, G. Pressure-Induced Phase Transition in Hydrogen-Bonded Supramolecular Structure: Guanidinium Nitrate. J. Phys. Chem. B 2010, 114, 6765−6769. (20) Reva, I.; Almeida, B. J. A. N.; Lapinski, L.; Fausto, R. UVInduced Photoisomerization of Maleic Hydrazide. J. Mol. Struct. 2012, 1025, 74−83. (21) Schoene, D. L.; Hoffmann, O. L. Maleic Hydrazide, a Unique Growth Regulant. Science 1949, 109, 588−590. (22) Miller, D. M.; White, R. W. The Structure of Maleic Hydrazide as Inferred from the Ultraviolet Spectra of Its Methyl Derivatives. Can. J. Chem. 1956, 34, 1510−1512. (23) Morzyk-Ociepa, B. X-Ray Crystal Structure and Vibrational Spectra of Hydrazides and Their Metal Complexes. Part I. Catenapoly[di-μ-aqua-(μ-maleic hydrazidato-O)sodium] Hydrate. J. Mol. Struct. 2007, 833, 121−132. (24) Ohashi, O.; Mashima, M.; Kubo, M. Proton Magnetic Resonance and the Structure of Maleic Hydrazide. Can. J. Chem. 1964, 42, 970−973. (25) Cradwick, P. D. Is Maleic Hydrazide a Pyrimidine or Purine Analogue? Nature 1975, 258, 774−774. (26) Cradwick, P. D. Crystal Structure of the Growth Inhibitor, ‘Maleic Hydrazide’ (1,2-dihydropyridazine-3,6-dione). J. Chem. Soc., Perkin Trans. 2 1976, 1386−1389. (27) Katrusiak, A. A New Polymorph of Maleic Hydrazide. Acta Crystallogr., Sect. C 1993, 49, 36−39. (28) Katrusiak, A. Polymorphism of Maleic Hydrazide. I. Acta Crystallogr., Sect. B 2001, 57, 697−704. (29) Katrusiak, A.; Katrusiak, A. Polymorphism and Phase Transitions in Maleic Hydrazide. Acta Crystallogr., Sect. A 2004, 60, s303−s303. (30) Katrusiak, A.; Katrusiak, A. Polymorph-Specific Chlorination of Maleic-Hydrazide. J. Mol. Struct. 2003, 647, 203−210. (31) Shen, G.; Chow, P.; Xiao, Y.; Sinogeikin, S.; Meng, Y.; Yang, W.; Liermann, H.-P.; Shebanova, O.; Rod, E.; Bommannavar, A.; Mao, H.K. HPCAT: an Integrated High-Pressure Synchrotron Facility at the Advanced Photon Source. High Pressure Res. 2008, 28, 145−162. (32) Goncharov, A. F.; Crowhurst, J. C. Raman Spectroscopy under Extreme Conditions. J. Low Temp. Phys. 2005, 139, 727−737. (33) Mao, H. K.; Bell, P. M.; Shaner, J. W.; Steinberg, D. J. Specific Volume Measurements of Cu, Mo, Pd, and Ag and Calibration of the Ruby R1 Fluorescence Pressure Gauge from 0.06 to 1 Mbar. J. Appl. Phys. 1978, 49, 3276−3283. (34) Hammersley, A. P.; Svensson, S. O.; Hanfland, M.; Fitch, A. N.; Hausermann, D. Two-Dimensional Detector Software: From Real Detector to Idealised Image or Two-Theta Scan. High Pressure Res. 1996, 14, 235−248. (35) Ciezak, J. A.; Jenkins, T. A.; Liu, Z.; Hemley, R. J. High-Pressure Vibrational Spectroscopy of Energetic Materials: Hexahydro-1,3,5trinitro-1,3,5-triazine. J. Phys. Chem. A 2007, 111, 59−63. (36) Park, T. R.; Dreger, Z. A.; Gupta, Y. M. Raman Spectroscopy of Pentaerythritol Single Crystals under High Pressures. J. Phys. Chem. B 2004, 108, 3174−3184. (37) Pravica, M.; Bai, L.; Liu, Y. Hydrazine at High Pressure. Chem. Phys. Lett. 2013, 555, 115−118. (38) Torabi, A.; Song, Y.; Staroverov, V. N. Pressure-Induced Polymorphic Transitions in Crystalline Diborane Deduced by Comparison of Simulated and Experimental Vibrational Spectra. J. Phys. Chem. C 2013, 117, 2210−2215. (39) Rozenberg, M.; Shoham, G.; Reva, I.; Fausto, R. A Correlation between the Proton Stretching Vibration Red-Shift and the Hydrogen

Bond Length in Polycrystalline Amino Acids and Peptides. Phys. Chem. Chem. Phys. 2005, 7, 2376−2383. (40) Hamann, S. D.; Linton, M. The Influence of Pressure on the Infrared Spectra of Hydrogen-Bonded Solids. III. Compounds with NH...X Bonds. Aust. J. Chem. 1976, 29, 1641−1647. (41) Pravica, M.; Yulga, B.; Liu, Z.; Tschauner, O. Infrared Study of 1,3,5-Triamino-2,4,6-trinitrobenzene under High Pressure. Phys. Rev. B 2007, 76, 064102. (42) Mishra, A. K.; Murli, C.; Sharma, S. M. High Pressure Raman Spectroscopic Study of Deuterated γ-Glycine. J. Phys. Chem. B 2008, 112, 15867−15874. (43) Lin, Y.; Ma, H. W.; Matthews, C. W.; Kolb, B.; Sinogeikin, S.; Thonhauser, T.; Mao, W. L. Experimental and Theoretical Studies on a High Pressure Monoclinic Phase of Ammonia Borane. J. Phys. Chem. C 2012, 116, 2172−2178. (44) Sharma, B. B.; Murli, C.; Sharma, S. M. Hydrogen Bonds and Polymerization in Acrylamide under Pressure. J. Raman Spectrosc. 2013, 44, 785−790. (45) Hall, D.; Headford, C. E. L. An Analysis of the Molecular Packing of Maleic Hydrazide. J. Comput. Chem. 1980, 1, 261−265.

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