Pressure-Induced Phase Transitions and Amorphization of 4

Subscriber access provided by RYERSON UNIVERSITY

Article

Pressure-Induced Phase Transitions and Amorphization of 4-Carboxybenzenesulfonyl Azide Junru Jiang, Huanpeng Bu, Peifen Zhu, Ran Liu, Bingbing Liu, Qiliang Cui, and Hongyang Zhu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b09508 • Publication Date (Web): 31 Oct 2016 Downloaded from http://pubs.acs.org on November 6, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Pressure-Induced Phase Transitions and Amorphization of 4-Carboxybenzenesulfonyl Azide

Junru Jiang,a Huanpeng Bu,a Peifen Zhu,b Ran Liu,a Bingbing Liu,a Qiliang Cuia and Hongyang Zhu*a

a

State Key Laboratory of Superhard Materials, Jilin University, Changchun, Jilin,

130012, China. b

Department of Physics and Engineering Physics, the University of Tulsa, Tulsa,

OK74104, USA

*Corresponding author: Tel: +8643185168881; fax: +8643185168881. E-mail address: [email protected]

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract The in situ high-pressure phase transition behaviors of energetic material 4-carboxybenzenesulfonyl azide (C7H5N3O4S, 4-CBSA) have been investigated by the measurements of Raman scattering, mid-IR absorption, and angle-dispersive X-ray diffraction (ADXRD) in diamond anvil cells, the highest pressure in our studies was up to ~ 14.6 GPa at room temperature. 4-CBSA transforms from phase I into phase II around 0.5-0.9 GPa, and then starts to going to phase III at about 2.5 GPa, phase II coexists with phase III till to about 5.5 GPa, the phase III of 4-CBSA finally begins to transform into amorphous state above 10.5 GPa. The first phase transition (phase I - II) of 4-CBSA is induced by the change of molecular conformation, and the second phase transition (phase II - III) is attributed to the distortion of benzene ring and the change of intermolecular O-H…O hydrogen bonds. The existence of sulfonyl group makes it much easier for the bent azide group to decompose under high pressure, which interpret that the amorphization pressure in 4-CBSA is much lower than that in benzyl azide. The unique behavior of azide group may be helpful to understand the electron orbit hybridization and the formation of polymeric nitrogen.


Page 2 of 31

Page 3 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction The importance of azides can be illustrated not only by their applications in industry and military as initial explosives, propellants, and combustibles,1, 2 but also for the preparation of superconductive materials.3 Azides, including inorganic azides and organic azides, have attracted considerable attention of scientists because the energetic nature of the azido moieties. As a new generation of high energy density materials (HEDMs), inorganic azides with azide ion are of particularly special use as precursors to form highly energetic polymeric nitrogen under high pressure and temperature.4-7 It has been reported that the azide ion in NaN3 can be converted to a nonmolecular nitrogen state with an amorphous-like structure at pressure above 120 GPa and then polymerized after laser heating.8 Moreover, theoretical results predict that the azide ion in LiN3, RbN3, and KN3 could be transformed into zigzag chain or benzene-like “N6” cluster, and then forming polymeric nitrogen at sufficiently high pressure.6,

9-11

The formation of polymeric nitrogen in inorganic azide requires

extreme high pressure because the linear azide ions keep linearly and the hybridization of electron orbit are hard to occur.12 Comparing to the inorganic azide, the organic azides are formed from the azide group which is asymmetrical and slightly bent. The electronic structure of azide group can be expressed with the resonance structures as shown in Figure 1.13,

14

The

existence of resonance structure II makes the electronic structure of azide group different from that of azide ion, which is related to different fundamental physical and chemical properties. In our recent studies, we have found that the benzyl azide with azide group transformed into amorphous-like nitrogen at much lower pressure (25.6 GPa) than that of NaN3 with azide ion (120 GPa).8, 15 It is believed that nonmolecular nitrogen or amorphous-like nitrogen play a vital role in the formation of



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 31

pressure-induced polymeric nitrogen network in organic azide.16-18 While the recent studies of organic azide are concentrated on the decomposition and organic synthesis.19-21 Few high pressure behavior studies of azide groups are reported. In order to understand the mechanism of polymerization and illustrate the unique high-pressure behavior of azide group, it is hence necessary to deep investigate the structure property of organic azides under high pressure. In this paper, we report the high-pressure

study

of

organic

4-carboxybenzenesulfonyl

azide

(4-CBSA,

C7H5N3O4S) by using Raman scattering, mid-IR absorption and ADXRD. The pressure-induced behavior of the bent azide group and the structural evolution of 4-CBSA might offer the comprehensive understanding for the hybridization of electron orbit and nitrogen polymerization.

Figure 1. Resonance structures of azide group in organic azide, the electronic structure of azide group is the superposition of structures I and II. 2. Experimental Details. 4-Carboxybenzenesulfonyl azide (4-CBSA) powder sample was purchased from Sigma-Aldrich (purity of 97%) and used without further purification. High-pressure experiments were performed in symmetric diamond anvil cells (DACs) with flat anvil of 400 or 500 µm in diameter. T301 stainless steel sheets were served as gaskets with sample chambers of 150 or 200 µm in diameter and 60 µm in thickness. A ruby ball was loaded into the sample chamber for in situ pressure calibration according to the fluorescence shift of the ruby R1 line. The methanol - ethanol mixture with volume


Page 5 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ratio of 4:1 was used as the pressure-transmitting medium in Raman and XRD experiments. The high-pressure Raman spectra were collected by an Acton SpectraPro500i spectrograph with a liquid-nitrogen-cooled CCD detector. Raman spectra were measured in a backscattering geometry with a 1800 gr/mm holographic grating. A solid-state, diode-pumped Nd: vanadate laser with wavelength 532 nm was used as the exciting source. The high-pressure mid-IR experiments were performed by a Bruker Vertex80V infrared spectrometer. For the mid-IR experiment, KBr was chosen as the pressure transmitting medium. The range of the mid-IR spectra was within 560-3600 cm-1, and the spectral resolution for all measurements was 2 cm-1. The acquisition time of each spectrum was 10 min. The in situ high-pressure synchrotron ADXRD experiments were conducted at B2 station of the Cornell High Energy Synchrotron Source (CHESS, Wilson Laboratory) at Cornell University with wavelength of 0.485946 Å. The diffraction patterns were collected using a MAR345 image plate detector. The diffraction images were integrated into plots of intensity versus 2θ using FIT2D software. 3. Results and Discussion The ambient pressure Raman and mid-IR spectra of 4-CBSA are presented in Figure 2. The Raman and mid-IR results of 4-CBSA are perfectly matched with that reported in chemistry database at ambient conditions.22, 23 The vibration groups have approximately similar characteristic frequencies in different chemical materials, so the assignments of the vibrational mode of 4-CBSA are based on the characteristic vibrations of benzoic acid, sulfonyl azide, and other organic azides.24-29 The Raman shifts of 4-CBSA in the frequency region of 50-330 cm-1 are designated into the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 31

lattice modes and intermolecular O-H…O hydrogen bonds. The in-plane bending (β), out-of-plane bending (γ), symmetric stretching (νs), and asymmetric stretching (νas) modes of azide group are related to the frequency region of 520-580 cm-1, 650-700 cm-1, 1250-1340 cm-1 and 2095-2162 cm-1, respectively.28, 30 The Raman peaks of 4-CBSA at 3080 and 3088 cm-1 are the C-H stretching modes of ring. The mid-IR peaks of 4-CBSA at 3140 and 3218 cm-1 are the O-H stretching modes of carboxy group. The assigned vibrational modes of azide group are in good agreement with the reported frequency range of 4-CBSA. The observed and reported bands of Raman and mid-IR corresponding to the assigned vibrational modes are listed in Table 1. Table 1. The vibrational mode assignments of 4-CBSA, the Raman and mid-IR bands from this work and the reported spectra are listed separately. Raman shifts (cm-1) Exp.

a

mid-IR wavenumbers (cm-1) b

Ref.

a

Exp.

Ref.

Assignments

c

78

Lattice mode (L)

88

H-bond vibration (H)

113

113


130

129

Lattice mode (L)

156

155

Lattice mode (L)

179

178

Lattice mode (L)

191

Lattice mode (L)

218

218


259

259

Lattice mode (L)

282

281

Lattice mode (L)

335

335

β OC=O

349

350

γ COOH

448

448

ω SO2

455

455

ω SO2

501

501

γ Ring


Page 7 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


γ O-H

524

524

551

552

546

554

β N3

583

583

585

581

β SO2

619

619

616

614

γ C=O

631

630

688

688

685

682

γ N3

705

703

715

713

γ C-H

773

773

766

761

ν C-C

804

803

820

820

823

γ C-H

842

842

840

γ C-H

866

866

863

858

ν C-C

942

941

γ C-H

988

1008

ν S-N

1013

1034

δ Ring

γ O-H

γ C-H

1085

1085

1084

1082

Ring breathing

1132

1132

1112

1106

νs SO2

1126

1124

ν C-N β C-H

1161

1160

1177

1176

1176

1167

β C-H

1287

1288

1293

1288

νs N3

1310

1310

1315

1310

νs N3

1377

1375

1376

1373

νas SO2

1406

1405

1403

1400

ν C-C

1452

1451

1426

1421

ν C-O

1492

1489

ν C-C

1575

1572

ν C-C

1603

1594

ν C-C

1601

1601

ν C-C

1627

1627

ν C=O



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 31

1637

1637

1696

1693

ν C=O

2143

2143

2148

2143

νas N3

3080

3080

ν C-H

3088

3087

ν C-H

a

This work.

b

Reference.23

c

Reference.22

3140

3102

ν O-H

3218

3251

ν O-H

ν, stretching; νas, asymmetric stretching; νs, symmetric stretching; β, in-plane bending; γ, out-of-plane bending; ω, wagging; δ, deformation.

Figure 2. The experimental collected (a) Raman and (b) mid-IR spectra of 4-CBSA at ambient pressure. The assignments of all the vibrational modes are listed above each band. The shadow areas marked with “Diamond” are the spectral region that will be blocked by diamond after the usage of DAC to generate high pressure. The pink spectrum marked with “×5” in (a) means the magnification of 5 times for the blue one in the dash rectangle.


Page 9 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The in situ high-pressure Raman scattering of 4-CBSA have been performed from ambient conditions up to 14.6 GPa. The selected Raman spectra of 4-CBSA upon compression with corresponding vibrational modes as a function of pressure are shown in Figure 3. In Figure 3a, a new external mode emerged at 0.5 GPa, as marked by arrow, and other two new lattice modes labeled with arrows appeared at 0.9 GPa accompanied with the disappearance of lattice modes marked with asterisks, indicating the first transition from phase I to phase II. The changes of internal vibration modes are consistent with the proposed phase transition, as shown in Figure 3b at 0.9 GPa. The peak marked with asterisk vanished and new peak emerged at 555 cm-1, implying 4-CBSA undergoes the first phase transition.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3. The selected high-pressure Raman spectra of 4-CBSA in the spectra region of (a) 50-330 cm-1 (b) 330-1280 cm-1 (c) 1400-3200 cm-1 with the corresponding modes as a function of pressure in (d), (e) and (f), respectively. D0 represents the Raman spectrum of 4-CBSA decompressed to 0 GPa. The arrows and asterisks denote the new appearance and the disappearance of peaks, respectively. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexistence of phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. With further compression to 2.6 GPa, the new Raman peak of lattice mode showed up at 199 cm-1 (Figure 3a), and the other two new peaks of ring C-C stretching mode (ν C-C) appeared at 759 and 777 cm-1 (Figure 3b). It is suggested that 4-CBSA begins the transformation from phase II to phase III at 2.6 GPa. With increasing pressure, the relative intensity change dramatically for the lattice mode at


Page 10 of 31

Page 11 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


170 cm-1 and the C-H stretching mode (ν C-H) at 3106/3115 cm-1. Compressing the sample to 5.3 GPa, all the features of lattice and internal modes indicate the completing of second phase transition from phase II to phase III. When the pressure is further increased to 10.5 GPa, most of the Raman bands of 4-CBSA are shown in blue shift. Nevertheless, the asymmetric stretching modes of azide group (νas N3) and the C-H stretching mode (ν C-H) in Figure 3c became extremely weak and hard to detect. It may suggest the decomposition of azide group and the beginning of the amorphization in 4-CBSA at 10.5 GPa. As the pressure increased up to the highest pressure (14.6 GPa) of this work, all the Raman bands are broad and nearly disappeared, indicating 4-CBSA in the completely amorphous phase. The phase transitions of 4-CBSA can be directly perceived from the pressure dependence of all the vibrational modes plotted in Figure 3d, 3e and 3f. The vertical dash line at 0.5-0.9 GPa help the eye to discern the transition pressure of 4-CBSA from phase I to phase II. The shadow regions obvious distinguish the pressure range for the coexisted phase II and phase III, and the phase II starts to go into phase III at 2.6 GPa and completely transforms into phase III at 5.3 GPa. The disappearance of most Raman modes at 10.5 GPa shows the beginning of amorphization in 4-CBSA. The slope of internal modes as a function of pressure is smaller than that of lattice modes, which suggests the intermolecular interactions of 4-CBSA are more easily affected by pressure than intramolecular interactions.31 The high-pressure mid-IR absorption measurements are performed on 4-CBSA up to 14.3 GPa. The selected mid-IR spectra of 4-CBSA under different pressures are shown in Figure 4. Figure 4a shows that the in-plane C-H bending mode (β C-H) splits into two at 0.6 GPa, and the mid-IR band of N3 in-plane bending mode (β N3) emerged at 0.9 GPa, indicating the transformation from phase I to phase II in 4-CBSA.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The phase II begins to tranform into phase III at 2.6 GPa, which is observed from the splitting of C-H out-of-plane bending mode (γ C-H) at 980 cm-1 and the new appeared mid-IR band of C=O out-of-plane bending mode at 635 cm-1. The phase II coexists with phase III till to 5.5 GPa. Continuing to increase pressure to 10.7 GPa, phase III becomes into amorphous, which is signified by the mid-IR broad bands and the indiscernible O-H stretching mode (ν O-H) in Figure 4b.


Page 12 of 31

Page 13 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. The selected high-pressure mid-IR spectra of 4-CBSA in the spectral region of (a) 520-2270 cm-1 and (b) 3000-3600 cm-1, respectively. The corresponding vibrational modes as a function of pressure are shown in (c), (d) and (e), respectively. The arrows in (a) denote the appearance of new peaks, the peak (β C-H) marked with pound splits into two. D0 represents the mid-IR spectrum of 4-CBSA decompressed to 0 GPa. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexisted phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. The mid-IR wavenumber of 4-CBSA as a function of pressure is exhibited in Figure 4c, d and e. It is suggested that the first phase transition from phase I to phase II is around 0.6-0.9GPa, and the beginning of phase II to phase III at 2.6 GPa is obviously observed from the discontinued shift of N3 in-plane bending mode (β N3)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

and O-H stretching mode (ν O-H). The shadow areas from 2.6 to 5.5 GPa clearly show the pressure region for the coexsited phase II and phase III. The disappearence of most of the mid-IR bands define the amorphization of 4-CBSA which starts at 10.7 GPa. 4-CBSA possesses several different conformations which are easily affected by pressure.32 This pressure-induced conformational change is accompanied with the bending of the azide group, resulting in the decrease of the N1-N2-N3 valence angle.15 The azide group in 4-CBSA is bent and asymmetric with different bond length between N1-N2 and N2-N3, differing from the linear and symmetric azide ion in inorganic azide. The new appeared mid-IR peak of N3 in-plane bending mode (β N3) around 0.6-0.9 GPa suggests that the bent azide group may lead the first phase transition (I - II) in 4-CBSA. The probable molecular conformation of phase I and phase II for 4-CBSA is shown in Figure 5.

Figure 5. The probable molecular conformation of 4-CBSA in phase I, phase II and phase III. The blue, white, green, yellow, and red spheres denote C, H, N, S, and O atoms, respectively. It is suggested that pressure has an effect on the structure stability and flexibility of ring in cyclic compounds. For benzene, pressure enhances the interactions among nearest-neighbor carbon molecules and distorts the benzene ring resulting in the lost of aromatic characters.33 The change of ring C-C stretching mode (ν C-C) and C-H stretching mode (ν C-H) suggest the distortion of benzene ring. The distortion change


Page 14 of 31

Page 15 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of ring in cyclic compound further leads to the conformational transformation under high pressure.15, 34 Analogously, it is perfect presented that the second phase transition (II - III) in 4-CBSA is just indicated by the change of Raman mode ν C-C and ν C-H. The possible molecular conformation of phase III 4-CBSA is exhibited in Figure 5. The intermolecular O-H…O hydrogen bonds are included in 4-CBSA, the evolution of hydrogen bond can be illustrated from the change of O-H stretching modes in the mid-IR spectra. It has been shown that hydrogen bonds significantly affect the behavior of azides under high pressure.35, 36 The O-H stretching mode (ν O-H) of 4-CBSA at 3140 cm-1 firstly shows red shift and then suddenly turns into blue shift at 2.6 GPa. It is obviously that the second phase transition (II - III) highly depend on the change of hydrogen bond, the turning from red shift to blue shift of the O-H stretching mode (ν O-H) can be interpreted as the different strength of hydrogen bonds.37 The mid-IR absorption of O-H stretching modes significantly depleted at 10.7 GPa, demonstrating the disruption of the hydrogen bonds in the amorphous of 4-CBSA. In addition, the O-H stretching modes are unrecovered when decompression to 0 GPa, signifying the disruption of O-H bond is an irreversible chemical transformation. To confirm the pressure-induced phase transitions of 4-CBSA, the high-pressure synchrotron ADXRD measurements are performed on it and carried out to 14.3 GPa. The evolution of the selected XRD patterns is depicted in Figure 6. The new diffraction peaks marked by arrows appeared at 0.6 and 0.9 GPa, respectively, and the intensity of these two new peaks are progressively increasing with the increased pressure, which indicates the occurrence of the first phase transition from phase I to phase II. In phase II, two peaks labeled with asterisks vanished completely that the pressure range of the changes observed in XRD patterns is consistent with the Raman



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

and mid-IR results.38 At 2.4 GPa, the other three new diffraction peaks appear and are marked with arrows, implying 4-CBSA begins the second phase transition from phase II to phase III under this pressure. When the pressure is increased to 5.7 GPa, all the diffraction peaks belong to phase III. Moreover, the diffraction patterns of phase II and phase III exhibit different characteristics in peak positions and intensity distribution, suggesting the significant change of unit cell under pressure which is consistent with different molecular conformation deduced from Raman and mid-IR. With increasing pressure, all the diffraction peaks shift to higher two theta angles as a result of the expected contraction of lattice volume. At 10.2 GPa, 4-CBSA starts to transform into amorphous state as can be seen from the broad band of XRD.

Figure 6. The representative XRD patterns of 4-CBSA under high pressures. The arrows represent the new diffraction peaks. The asterisks mean the disappearance of


Page 16 of 31

Page 17 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the diffraction peaks. The peak marked with diamond in (b) is weak and overlapped with nearby strong peak at ambient pressure, and it separates from the strong one at 1.8 GPa. The dash rectangular areas in (a) are magnified separately and showed in (b) and (c). The superposition of two resonance structures reflects that the properties of 4-CBSA are dramatically rely on the electronic structure of azide group. It has been reported that the azide ions in inorganic azide rotate and occupy equivalent crystal sites with increasing pressure by Raman studies.39 However, the azide groups in 4-CBSA rotate and occupy nonequivalent crystallographic positions in the unit cell of high pressure phases, deduced from the new N3 asymmetric stretching mode (νas N3) at 3.7 GPa.7, 12, 35 The different electronic structure between azide group and azide ion may be related to the lower amorphous transition pressure in 4-CBSA than that in inorganic azide. The azide group in 4-CBSA is bonded to the stable sulfonyl group, and the azide group is bonded to methylene group in benzyl azide. The comparison of molecular structures of 4-CBSA and benzyl azide at ambient pressure is depicted in Figure 7. The behavior of azide group under high pressure will be severely influenced by the different substitute groups which are connected to azide group. The azide group of benzyl azide rotates first under high pressure and then results in the rotation of methylene group. The amorphous pressure for benzyl azide is 25.6 GPa with the decomposition of azide group. While for 4-CBSA, the bent azide group of 4-CBSA undergoes a bending process before rotating in high pressure compression. This might because the function of hydrogen bond increases the binding force and causes the bending of azide group firstly. The bent azide group makes it much easier for the azide group to decompose, so the amorphization pressure of 4-CBSA is much lower than that of benzyl azide.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 7. The comparison of molecular structures of 4-CBSA and benzyl azide at ambient pressure. The bent azide groups are crucial for triggering the electron orbit hybridization and nitrogen polymerization in compression.12 The lower amorphization pressure of azide groups probably decreases the pressure for the formation of polymeric nitrogen, furthermore, the amorphization of azide groups play a significant role in the synthesis of nitrogen polymerization. In this repect, the unique behavior of the bending azide group chain of 4-CBSA may provide a potential method for preparation of polymeric nitrogen at a relatively low pressure. 4. Conclusion In summary, Raman scattering, mid-IR absorption spectroscopy and ADXRD techniques have been performed on energetic material 4-CBSA to study the structural phase changes under high pressure up to 14.6, 14.3, and 14.3 GPa, respectively. All the Raman and mid-IR vibrational modes of 4-CBSA at ambient pressure are assigned for the first time. Upon compression, the first phase transitions from phase I to phase II is observed at 0.5-0.9 GPa. Phase II and phase III coexist with each other in the pressure range of 2.6-5.5 GPa. With the pressure increased to about 10.5 GPa, phase III starts to transform into an amorphous state. The analysis of vibrational modes and structure information reveal that the change of molecular conformation makes contribution to the first phase transition. The distortion of benzene ring and evolution


Page 18 of 31

Page 19 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of intermolecular O-H…O hydrogen bonds are attributed to the second phase transition from phase II to phase III. The unique properties of the bent azide groups support the evidence of lower amorphization pressure in 4-CBSA than that in benzyl azide. The studies help to deep the understanding of the properties of azide group as well as the influence of hydrogen bond in organic azide under high-pressure conditions. Acknowledgements We thank Chunli Ma for proofreading the manuscript. This work is supported by the National Natural Science Foundation of China (11304111, 11304139). ADXRD measurements have been performed at B2 station of the Cornell High Energy Synchrotron Source (CHESS, Wilson Laboratory) at Cornell University, which is supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR-1332208. References 1. Aduev, B. P.; Aluker, E. D.; Belokurov, G. M.; Zakharov, Y. A.; Krechetov, A. G. Explosive Decomposition of Heavy-metal Azides. J. Exp. Theor. Phys. 1999, 89, 906-915. 2. Evans, B. L.; Yoffe, A. D.; Gray, P. Physics and Chemistry of the Inorganic Azides. Chem. Rev. 1959, 59, 515-568. 3. Tokumoto, M.; Tanaka, Y.; Kinoshita, N.; Kinoshita, T.;

Ishibashi, S.; Ihara, H.

Characterization of Superconducting Alkali and Alkaline-earth Fullerides Prepared by Thermal Decomposition of Azides. J. Phys. Chem. Sol. 1994, 54, 1667-1673. 4. Hou, D.; Zhang, F.; Ji, C.; Hannon, T.; Zhu, H.; Wu, J.; Ma, Y. Series of Phase Transitions in Cesium Azide under High Pressure Studied by in situ X-ray Diffraction. Phys. Rev. B 2011, 84, 064127. 5. Zhu, H.; Zhang, F.; Ji, C.; Hou, D.; Wu, J.; Hannon, T.; Ma, Y. Pressure-Induced Series of Phase Transitions in Sodium Azide. J. Appl. Phys. 2013, 113, 033511. 6. Wang, X.; Li, J.; Xu, N.; Zhu, H.; Hu, Z.; Chen, L. Layered Polymeric Nitrogen in RbN3 at High Pressures. Sci. Rep. 2015, 5, 16677.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

7. Li, D.; Li, F.; Li, Y.; Wu, X.; Fu, G.; Liu, Z.; Wang, X.; Cui, Q.; Zhu, H. High-Pressure Studies of Rubidium Azide by Raman and Infrared Spectroscopies. J. Phys. Chem. C 2015, 119, 16870-16878. 8. Eremets, M. I.; Popov, M. Y.; Trojan, I. A.; Denisov, V. N.; Boehler, R.; Hemley, R. J. Polymerization of Nitrogen in Sodium Azide. J. Chem. Phys. 2004, 120, 10618-10623. 9. Li, J.; Wang, X.; Xu, N.; Li, D.; Wang, D.; Chen, L. Pressure-Induced Polymerization of Nitrogen in Potassium Azides. EPL 2013, 104, 16005. 10. Wang, X.; Li, J.; Botana, J.; Zhang, M.; Zhu, H.; Chen, L.; Liu, H.; Cui, T.; Miao, M. Polymerization of Nitrogen in Lithium Azide. J. Chem. Phys. 2013, 139, 164710. 11. Zhang, M.; Yan, H.; Wei, Q; Wang, H.; Wu, Z. Novel High-Pressure Phase with Pseudo-Benzene “N6” Molecule of LiN3. EPL 2013, 101, 26004. 12. Zhu, H.; Han, X.; Zhu, P.; Wu, X.; Chen, Y.; Li, M.; Li, X.; Cui, Q. Pressure-Induced Amorphization of Strontium Azide. J. Phys. Chem. C 2016, 120, 12423-12428. 13. Frevel, L. K. The Configuration of the Azide Ion. J. Am. Chem. Soc. 1936, 58, 779-782. 14. Zeng, X.; Gerken, M.; Beckers, H.; Willner, H. Anomeric Effects in Sulfonyl Compounds: An Experimental and Computational Study of Fluorosulfonyl Azide, FSO2N3, and Trifluoromethylsulfonyl Azide, CF3SO2N3. J. Phys. Chem. A 114, 7624-7630. 15. Jiang, J.; Wu, X.; Li, D.; Ma, B.; Liu, R.; Wang, X.; Zhang, J.; Zhu, H.; Cui, Q. High Pressure Raman Scattering and Synchrotron X-ray Diffraction Studies of Benzyl Azide. J. Phys. Chem. B 2015, 119, 513-518. 16. Goncharov, A. F.; Gregoryanz, E.; Mao, H.; Liu, Z.; Hemley, R. J. Optical Evidence for a Nonmolecular Phase of Nitrogen above 150 GPa. Phys. Rev. Lett. 2000, 85, 1262-1265. 17. Eremets, M. I.; Gavriliuk, A. G.; Serebryanaya, N. R.; Trojan, I. A.; Dzivenko, D. A.; Boehler, R.; Mao, H. K.; Hemley, R. J. Structural Transformation of Molecular Nitrogen to a Single-Bonded Atomic State at High Pressures. J. Chem. Phys. 2004, 121, 11296-11300. 18. Eremets, M. I.; Gavriliuk, A. G.; Trojan, I. A.; Dzivenko, D. A.; Boehler, R. Single-Bonded Cubic Form of Nitrogen. Nat. Mater. 2004, 3, 558-563. 19. Liu, Z.; Liao, P.; Bi, X. General Silver-Catalyzed Hydroazidation of Terminal Alkynes by Combining TMS-N3 and H2O: Synthesis of Vinyl Azides. Org. Lett. 2014, 16, 3668-3671. 20. Cantillo, D.; Gutmann, B.; Kappe, C. O. Mechanistic Insights on Azide-Nitrile Cycloadditions: on the Dialkyltin Oxide-Trimethylsilyl Azide Route and a New Vilsmeier-Haack-Type Organocatalyst. J. Am. Chem. Soc 2011, 133, 4465-4475. 21. Wu, Z.; Li, H.; Zhu, B.; Zeng, X.; Hayes, S. A.; Mitzel, N. W.; Beckers, H.; Berger, R. J. Conformational Composition, Molecular Structure and Decomposition of Difluorophosphoryl Azide in the Gas Phase. Phys. Chem. Chem. Phys. 2015, 17, 8784-8791. 22. Chemistry Database. www.organchem.csdb.cn. (accessed 1978). 23. Sigma-Aldrich. www.sigmaaldrich.com. (accessed Jul 12, 2007).


Page 20 of 31

Page 21 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


24. Stepanian, S.G.; Reva, I.D.; Radchenko,E.D.; Sheina, G.G. Infrared Spectra of Benzoic Acid Monomers and Dimers in Argon Matrix. 1996, 11, 123-133. 25. Klsusberger, G.; Furic, K.; Colombo, L. Vibrational Spectra and Normal Mode Calculations of Benzoic Acid Single Crystal. J. Raman. Spectrosc 1977, 6, 277-281. 26. Dabbagh, H. A.; Teimouri, A.; Chermahini, A. N.; Shiasi, R. DFT and Ab Initio Calculations of the Vibrational Frequencies and Visible Spectra of Triazenes Derived From Cyclic Amines. Spectrochim Acta A: Mol Biomol Spectrosc 2007, 67, 437-443. 27. Teimouri, A.; Chermahini, A. N.; Emamic, M. Synthesis, Spectroscopic Characterization and DFT Calculations on [4-(Sulfonylazide)phenyl]-1-Azide. Arkivoc, 2008, 12, 172-187. 28. Durig, D. T.; Durig, M. S.; Durig, J. R. On the Vibrational Spectra and Structural Parameters of Methyl, Silyl, and Germyl Azide from Theoretical Predictions and Experimental Data. Spectrochim Acta A: Mol Biomol Spectrosc 2005, 61, 1287-1306. 29. Stankovsky, S.; Kovao, S. Infrared Spectra of Heterocumulenes. IV. The Influence of Substituents on the vas(NNN) Bands of Some Substituted Phenyl Azides. Chem. Zvesti 1973, 28, 243-246. 30. Thomas, M. K.; Burkhard, K.; Richard, M. Synthetic and Structural Studies on Methyl-, tert-Butyl- and Phenylmercury(II) Azide. Z. Anorg. Allg. Chem. 2011, 637, 507-514. 31. Yan, T.; Wang, K.; Tan, X.; Yang, K.; Liu, B.; Zou, B. Pressure-Induced Phase Transition in N–H···O Hydrogen-Bonded Molecular Crystal Biurea: Combined Raman Scattering and X-ray Diffraction Study. J. Phys. Chem. C 2014, 118, 15162-15168. 32. Zeng, X.; Gerken, M.; Beckers,H.; Willner, H. Anomeric Effects in Sulfonyl Compounds: An Experimental and Computational Study of Fluorosulfonyl Azide, FSO2N3, and Trifluoromethylsulfonyl Azide, CF3SO2N3. J. Phys. Chem. A 2010, 114, 7624–7630. 33. Lucia, C.; Mario, S.; Roberto, B.; Vincenzo, S. High Pressure Reactivity of Solid Benzene Probed by Infrared Spectroscopy. J. Chem. Phys. 2002, 116, 2928. 34. Jiang, J.; Zhang, J.; Zhu, P.; Li, J.; Wang, X.; Liu, B.; Cui, Q.; Zhu, H. High Pressure Studies of Ni3[(C2H5N5)6(H2O)6](NO3)6·1.5H2O by Raman Scattering, IR Absorption, and Synchrotron X-ray Diffraction. RSC Adv. 2016, 6, 65031-65037. 35. Wu, X.; Cui, H.; Zhang, J.; Cong, R.; Zhu, H.; Cui, Q. High Pressure Synchrotron X-ray Diffraction and Raman Scattering Studies of Ammonium Azide. App. Phys. Lett. 2013, 102, 121902. 36. Wu, X.; Ma, F.; Ma, C.; Cui, H.; Liu, Z.; Zhu, H.; Wang, X.; Cui, Q. Pressure-Driven Variations of Hydrogen Bonding Energy in Ammonium Azide (NH4N3): IR Absorption and Raman Scattering Studies. J. Chem. Phys. 2014, 141, 024703. 37. Yan, T.; Wang, K.; Tan, X.; Liu, J.; Liu, B.; Zou, B. Exploration of the Hydrogen-Bonded Energetic Material Carbohydrazide at High Pressures. J. Phys. Chem. C 2014, 118, 22960-22967.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

38. Thiéry, M. M.; Léger, J. M. High Pressure Solid Phases of Benzene. I. Raman and X-ray Studies of C6H6 at 294 K up to 25 GPa. J. Chem. Phys. 1988, 89, 4255. 39. Medvedev, S. A.; Eremets, M. I.; Evers, J.; Klapötke, T. M.; Palasyuk, T.; Trojan, I. A. Pressure Induced Polymorphism in Ammonium Azide (NH4N3). Chem. Phys. 2011, 386, 41-44.

TOC:


Page 22 of 31

Page 23 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Resonance structures of azide group in organic azide, the electronic structure of azide group is the superposition of structures I and II. 151x42mm (72 x 72 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2. The experimental collected (a) Raman and (b) mid-IR spectra of 4-CBSA at ambient pressure. The assignments of all the vibrational modes are listed above each band. The shadow areas marked with “Diamond” are the spectral region that will be blocked by diamond after the usage of DAC to generate high pressure. The pink spectrum marked with “×5” in (a) means the magnification of 5 times for the blue one in the dash rectangle. 287x152mm (300 x 300 DPI)


Page 24 of 31

Page 25 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. The selected high-pressure Raman spectra of 4-CBSA in the spectra region of (a) 50-330 cm-1 (b) 330-1280 cm-1 (c) 1400-3200 cm-1 with the corresponding modes as a function of pressure in (d), (e) and (f), respectively. D0 represents the Raman spectrum of 4-CBSA decompressed to 0 GPa. The arrows and asterisks denote the new appearance and the disappearance of peaks, respectively. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexistence of phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. 355x201mm (300 x 300 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3. The selected high-pressure Raman spectra of 4-CBSA in the spectra region of (a) 50-330 cm-1 (b) 330-1280 cm-1 (c) 1400-3200 cm-1 with the corresponding modes as a function of pressure in (d), (e) and (f), respectively. D0 represents the Raman spectrum of 4-CBSA decompressed to 0 GPa. The arrows and asterisks denote the new appearance and the disappearance of peaks, respectively. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexistence of phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. 254x201mm (300 x 300 DPI)


Page 26 of 31

Page 27 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. The selected high-pressure mid-IR spectra of 4-CBSA in the spectral region of (a) 520-2270 cm-1 and (b) 3000-3600 cm-1, respectively. The corresponding vibrational modes as a function of pressure are shown in (c), (d) and (e), respectively. The arrows in (a) denote the appearance of new peaks, the peak (β C-H) marked with pound splits into two. D0 represents the mid-IR spectrum of 4-CBSA decompressed to 0 GPa. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexisted phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. 279x202mm (300 x 300 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4. The selected high-pressure mid-IR spectra of 4-CBSA in the spectral region of (a) 520-2270 cm-1 and (b) 3000-3600 cm-1, respectively. The corresponding vibrational modes as a function of pressure are shown in (c), (d) and (e), respectively. The arrows in (a) denote the appearance of new peaks, the peak (β C-H) marked with pound splits into two. D0 represents the mid-IR spectrum of 4-CBSA decompressed to 0 GPa. The vertical dash lines indicate the first phase transition pressure from phase I into phase II, the shadow areas exhibit the pressure region for the coexisted phase II and phase III. The red vertical dash lines mean the amorphization pressure of 4-CBSA. 279x201mm (300 x 300 DPI)


Page 28 of 31

Page 29 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. The probable molecular conformation of 4-CBSA in phase I, phase II and phase III. The blue, white, green, yellow, and red spheres denote C, H, N, S, and O atoms, respectively. 699x157mm (72 x 72 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6. The representative XRD patterns of 4-CBSA under high pressures. The arrows represent the new diffraction peaks. The asterisks mean the disappearance of the diffraction peaks. The peak marked with diamond in (b) is weak and overlapped with nearby strong peak at ambient pressure, and it separates from the strong one at 1.8 GPa. The dash rectangular areas in (a) are magnified separately and showed in (b) and (c). 190x201mm (300 x 300 DPI)


Page 30 of 31

Page 31 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. The comparison of molecular structures of 4-CBSA and benzyl azide at ambient pressure. 221x67mm (72 x 72 DPI)


Pressure-Induced Phase Transitions and Amorphization of 4

Recommend Documents