A small-molecule chemosensor for the selective detection of 2,4,6-trinitrophenol (TNP)

Article abstract of DOI:10.1039/c4ra07957d

A pyridine-based small-molecule receptor (L) for the specific recognition of TNP was synthesised and characterised by ¹H NMR, ¹³C NMR and FT-IR spectra, and the optical properties were studied by UV-Vis absorption and PL spectra. The

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Graphic abstract for:
A small-molecule chemosensor for the selective detection of
2,4,6-trinitrophenol (TNP)
Jianting Pana, Fang Tanga, Aixiang Dinga, Lin Konga*, Longmei Yanga, Xutang Taob,
Yupeng Tiana, Jiaxiang Yanga,b,
*
A pyridine-based small-molecule receptor (L) for specific recognition of TNP was synthesized
and characterized by 1H NMR, 13C NMR and FT-IR spectra, the optical properties were studied by
UV-Vis absorption and PL spectra. The results showed that the fluorescence of L was strongly
quenched by picric acid, accompanying with an obviously color change from transparent to yellow,
which indicated that receptor L can serve as a small-molecule sensor for TNP. The crystal
structure and theoretical calculation of corresponding host-guest complex L.TNP were also
performed.

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RSC AdvancesRSCPublishing
PAPER
A smallꢀmolecule chemosensor for the selective
cweizhiCite this: DOI: 10.1039/x0xx00000x
10 detection of 2,4,6ꢀtrinitrophenol (TNP)
Jianting Pana, Fang Tanga, Aixiang Dinga, Lin Konga*, Longmei
Yanga, Xutang Taob, Yupeng Tiana, Jiaxiang Yanga,b,
*
A pyridineꢀbased smallꢀmolecule receptor (L) for specific recognition of TNP was
1
synthesized and characterized by H NMR, 13C NMR and FTꢀIR spectra, the optical
Received 00thxxxxxxxx,
Accepted 00thxxxxxxxx
15 properties were studied by UVꢀVis absorption and PL spectra. The results showed that
the fluorescence of L was strongly quenched by picric acid, accompanying with an
obviously color change from transparent to yellow, which indicated that receptor L can
serve as a smallꢀmolecule sensor for TNP. The crystal structure and theoretical
calculation of corresponding hostꢀguest complex L.TNP were also performed.
5
DOI: 10.1039/x0xx00000x
www.rsc.org/
20
Rational design and synthesis of host molecules for the particular
guest molecules or ions are drawing more and more active
attention due to their vitally important applications in the fields of
biological and environmental sensing.1,2 The structure of
with the appearance of a new strong absorption band at 424 nm,
meanwhile, an apparent color change from transparent to yellow
was observed, accompanying with a fluorescence quenching at
440 nm and a new emission band appearing at 550 nm.
25 molecule possesses pyridine unit could be fascinating “acceptor”
for a variety of metal ions for their strong binding abilities.3,4
However, to our best knowledge, there still are rare reports
focused on the neutral molecules of nitrated explosives, using
trinitrophenol (TNP) as an example.5,6 Nitroꢀaromatic compounds
30 (NACs), such as 2, 4ꢀdinitrotoluene (DNT), trinitrotoluene (TNT),
TNP, to name a few, are widely used in manufacturing and
blasting industries. Because of the potential damage to respiratory
system and superior fierce explosive to that of TNT.7,8,9 Apart
from its highly explosive nature, TNP is also recognized as a
35 infamous threat to the human health and national security, which
can cause severe irritation, skin allergy, dizziness, nausea,
damage of liver, and kidney.10,11 Water contamination of TNP
may cause severe epidemic.12,13 As such, a large number of
molecular and modulated chemosensors had been developed.14ꢀ19
40 Some of them showed good selectivity and sensitivity to TNP, but
their structures are complicated and usually need a multiꢀstep and
inefficient synthetic procedure. Therefore, developing simple and
effective molecules for the specific recognition of TNP is urgent
and instructive.
55
Scheme 1. Synthesis routes of receptor L.
Experimental section
Chemical and instruments
The commercially available chemicals were used without
60 further purification. All of the solvents used were purified by
conventional methods before use. Synthetic routes were shown in
scheme 1 and the characterizations were described. 1H NMR and
13C NMR spectra were recorded on Bruker Avance 400 MHz
NMR spectrometer, using DMSOꢀd6 as solvent and calibrated
65 using tetramethylsilane (TMS) as an internal reference. Data were
reported as follows: chemical shifts (δ) in ppm, multiplicity (s =
singlet, d = doublet, t = triplet, m = multiplet), coupling constants
J (Hz), integration, and interpretation. The UVꢀVis absorption
spectra were recorded on the UVꢀ265 spectrophotometer with a
70 quartz cuvette (path length, 1 cm). The oneꢀphoton excited
fluorescence (OPEF) spectra measurements were performed
using the Hitachi Fꢀ7000 fluorescence spectrophotometer. Highꢀ
resolution mass spectra (HRꢀMS) were taken on a Thermo Fisher
45
Herein, in our present paper, a novel simple pyridineꢀbased
compound, (E)ꢀ4ꢀ(2ꢀ(pyridinꢀ4ꢀyl)vinyl)aniline (L), was designed,
synthesized and characterized, which was expected to form “hostꢀ
guest” complex with TNP, giving entirely different UVꢀVis
absorption and fluorescence responsive. The absorption of
50 compound L with TNP at 350 nm obviously increased, together
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 |1

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LTQꢀOrbitrap XL mass Spectrometer using an electrospray ion 40 into compound L effected the absorption comparing with other
source (ESI). FTꢀIR spectra were obtained in KBr discs on a
Nicolet 380 FTꢀIR spectrometer in the 4000ꢀ400 cmꢀ1 region.
Photo images were obtained using a digital camera (Nikon
D7000). Silica gel 60 (60ꢀ120 mesh) was used for column
chromatography.
Caution! TNP, TNT, DNT, and other nitroaromatics (a~h, Fig.
1(c)) should be used with extreme care using the best safety
precautions owing to their highly explosive character. They
NACs. The absorption of compound L with TNP at 350 nm
evidently increased, accompanying the appearance of a new
strong absorption band at 424 nm, which indicated there may be a
formation of the complex between compound L and TNP with
45 totally different electronic properties from that of compound L.
Thanks to this, an obviously color change from transparent to
yellow was observed after addition of TNP into compound L,
allowing colorimetric detection of TNP by the naked eye (Fig. 1,
insets).
5
10 should be handled only in small quantities.
50
Furthermore, fluorescence studies of the compound L with
different NACs were shown in Fig. 1(b). The free L displayed an
intensive emission at 440 nm in THF solution. The fluorescent
influences of the NACs aginst L were also investigated in THF
solution. It could be found that emission intensity of the
Preparation of the target compound L
Compound L was prepared according to the method reported
in the literature.20 FTꢀIR (KBr, cmꢀ1) selected bands: 3390 (m),
3317 (m), 3032 (w), 2923 (w), 2849 (w), 1584 (s), 1515 (s), 1415
15 (s), 832 (s). 1H NMR (DMSOꢀd6, 400 MHz, ppm) δ: 5.45 (s, 2H),
6.55 (d, J = 5.6 Hz, 2H), 6.83 (d, J = 5.4 Hz, 1H), 7.31 (m, 3H),
7.41 (d, J = 4.0 Hz, 2H), 8.42 (d, J = 4.0 Hz, 2H).
13C NMR (DMSOꢀd6, 100 MHz, ppm) δ:116.87, 122.91, 123.27,
126.17, 131.59, 132.87, 136.85, 148.35, 152.88. HRꢀMS (ESIꢀ
20 MS): m/z = 197.1107, calcd for [C13H13N2]+ = 197.1000
([M+H]+).
55 compound L at 440 nm decreased dramatically (about 87%
quenching) with a new emission wavelength at 550 nm when 5
equiv. TNP was added, however, negligible changes in the
fluorescent spectra were monitored upon addition of other NACs.
The above mentioned UVꢀVis absorption studies and the
60 fluorescent studies here demonstrated that compound L could
bind with TNP effectively and serve as specific recognizer of TNP.
Results and discussion
UV-Vis absorption and fluorescence spectra
Fig. 2. Change in the fluorescence of the compound L (10 ꢀM) in THF
65 upon the addition of TNP (0ꢀ20 equiv.), λex = 350 nm. Inset: the
fluorescent quenching percentage as a function of TNP concentration,
concentration = 10 ꢁM.
In order to get a further investigation to the photoꢀphysical
response of the compound L with TNP, corresponding UVꢀVis
70 titration experiment (Figure S1, ESI†) and fluorescent titration
experiment were conducted. As shown in Fig. 2, upon addition of
incremental amounts of 10 ꢁM of TNP to the solution of L in
THF, the quenching in fluorescence emission at 440 nm was
observed at concentration as low as 20 equivalents. Meanwhile, a
75 new emission at 550 nm rose up. Then we measured fluorescence
lifetime of derivative L for different concentrations of TNP (0,
0.5, 1.0 equiv.). The fluorescence lifetime of compound L was
found to be invariant (< 0.1 ns) at different concentration of TNP
(Figure S2, ESI†). Thus, indicating that the quenching at 440 nm
80 is static and ground state complex is formed between compound
L and TNP. These results implied that there are strong interaction
between L and TNP. We proposed that three “NO2” groups in
TNP may act as strong electronꢀwithdrawing group protonating
the pyridine ring to further affect the intramolecular electron
85 density distribution when they formed hydrogen bond interaction
25
Fig. 1. (a) UVꢀVis absorption of L (10 ꢀM) in THF upon addition of 5
equiv. selected NACs. Inset: the degree of change in absorbance of 350
nm. A0 is the absorbance of the receptor L, A is the absorbance after
adding aꢀh. The photo shows that L appeared an obvious selectivity of
30 TNP. (b) Responses of the L (10 ꢀM) toward different NACs (5 equiv.) in
THF. Inset: the degree of change in intensity of 440 nm. I0 is the intensity
of the receptor L, I is the intensity of L after adding a~h. (c) Structures of
the NACs used in the present study (a~h).
Initially, the molecular recognition behaviors of the compound
35 L toward the selected NACs were investigated by UVꢀVis and
fluorescence spectroscopy. As shown in Fig. 1(a), the free L in
THF showed a maximum absorption wavelength at 350 nm. The
influences of the selected NACs on its absorption were studied
with the method as used before.21 The addition of 5 equiv. TNP
2

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by each other. The redistribution of the electron density
Limiting indices
ꢀ9 ≤ h ≤7
ꢀ14 ≤ k ≤14
ꢀ23 ≤ l ≤23
9806/3417
3417/1/280
influenced the intramolecular charge transfer (ICT) that
subsequently induced an absorption and fluorescence response to
TNP. Job’s plot analysis was conducted to corroborate 1:1 ratio
between L and TNP (Figure S3, ESI†).22 A linear SternꢀVolmer
plot was obtained from fluorescence quenching titration (Figure
S4, ESI†) with KSV = 4.106 × 105 M−1.9 The detection limit was
also found to be 400 ppb for TNP (Figure S5, ESI†).23 The
interference experiment of other nitro aromatics towards the
Reflections collected
Data / restraints / parameters
Goodnessꢀofꢀfit on F2
1.032
5
Final R indices [I>2sigma(I)]
R indices (all data)
R1 = 0.0802, wR2 = 0.1862
R1 = 0.1211, wR2 = 0.2164
40
The crystal structure showed that the nitrogen of the pyridine
group of L is protonated to form as a cation while picric acid is
deprotonated to form as a anion, where the pyridine group was
changed from a hydrogen bond acceptor to the hydrogen bond
donor (Fig. 3a).26 The “L cations” and “TNP anions” were selfꢀ
10 interaction of TNP with L in THF was conducted (Figure S6,
ESI†), it was found that the fluorescence emission intensity of the
L
was almost unaffected. Considering an environmental
application, an optimized aqueous solution (THF : H2O = 9 : 1,
v/v) was then selected as a testing system to investigate the
15 spectral response of the probe L to TNP at room temperature. As
shown in Figure S7 (ESI†), both the absorption and fluorescence
spectra in aqueous solution gave a similar response to those
observed in pure THF, proving that L can detect TNP in aqueous
solution. The ideal experimental results here amplified the
20 practical applicability of the probe toward TNP sensing. Further,
we did the fluorescence titration experiments of the probe L to
TNP (0ꢀ20 equiv.) at various excitation wavelengths. No obvious
change in quenching efficiency of TNP was observed (Figure S8,
ESI†).
45 assembled to form a supramolecular structure via multiple
hydrogen bond and πꢀπ interactions. As shown in Fig. 3b and c,
each picrate acted as a hydrogen bond acceptor to connect six
ligands and one picrate via 8 hydrogenꢀbonds, and each L acted
as hydrogen bond donor and acceptor to connect seven picrates
50 and one other ligand via 8 hydrogen bonds in which the DꢀA
distances vary from 2.763 to 3.591 Å and the corresponding Dꢀ
H…A angles were in the range 118.53ꢀ171.29 o (Table S1, ESI†).
The intermolecular πꢀπ stacking interaction between the picrate
ring and phenylamine ring of L, presented a πꢀπ distance of 3.859
55 Å and a dihedral angle of 15.8 o. It was noteworthy that the two
hydrogen bonds between N4 of the pyridine group bonding to the
O7 of the hydroxyl group and the O5 of the nitro group in the
picrate respectively were very strong owing to their short
distance.27 These results implied that the pyridine group of L was
60 the key site for specific interaction with TNP.
25 Single crystal analysis
Next, we grew the single crystal of L.TNP and investigated the
interactions between the L and TNP to explain the emission band
changing. When 5 mL of TNP (2.6 × 10ꢀ2 M) solution was added
to 5 mL of L (2 × 10ꢀ2 M) solution in THF/ethanol (2:1). After a
30 few days, vermilion block crystals were obtained by slow
evaporation of the solvent at room temperature (Fig. 3a). A
singleꢀcrystal Xꢀray diffraction analysis revealed that a 1:1 hostꢀ
guest complex L.TNP was formed (Fig. 3a) by L and TNP as in
solution. The relevant crystal data and structural parameters were
35 listed. (Table 1) All calculations and graphical works have been
done using WinGX24 and PLATON25 programs.
Table 1 Summary of crystallographic data and structure
refinement details for L·TNP
Identification code
Empirical formula
Formula mass
L·TNP
C19H15N5O7
425.36
Crystal system, Space group
Unit cell dimensions
Monoclinic, P2(1)/c
a = 7.917(5) Å
Fig. 3. (a) Photos of L and L.TNP and the Xꢀray structure of the hostꢀ
guest complex L.TNP; (b) The hydrogen bond interactions around TNP in
65 the complex; (c) The hydrogen bond interactions and πꢀπ interactions
around L in the complex (the hydrogen bond interactions and πꢀπ
interactions are indicated with dashed turquoise and bright green lines,
respectively. Some hydrogen atoms are omitted for clarity).
α
= 90.000(5) °
b = 12.258(5) Å
= 96.658(5) °
c = 20.049(5) Å
β
γ
= 90.000(5) °
Volume
Z, Calculated density
Temperature
1932.6(15) Å3
4, 1.462 Mg·mꢀ3
298(2) K
1H NMR titration
Crystal size
Absorption coefficient
F(000)
0.30 × 0.20 × 0.20 mm
70
The interaction between the probe L and TNP in solution was
further studied by the method of H NMR titration experiment
(Fig. 4). The signals of the hydrogens located on the aromatic
0.115 mmꢀ1
1
880
Theta range for data collection
1.95 ° to 25.00 °
3

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rings were generally downfield shifted upon addition of 2.0 equiv. 45 compound L.TNP is stable.
TNP. Due to the decrease in electron density of the pyridine ring
moiety, Hb, Hc and Hf were shifted obviously, and the chemical
shifts (ꢂδ) for L were 0.690, 0.577, 0.532. These results
suggested that the nitrogen atom of the pyridine ring moiety of L
was the only reasonable sites for protonation by TNP. To further
gain insight into the recognition mechanism, the interaction
between the probe L and another analogous strong organic acid,
pH effect
In order to understand the selectivity of receptor L toward TNP
and/or other NACs, pH effect has been investigated in water. In
this case, we selected DNP (pKa = 3.96) as a represent, whose
50 structure is more close to TNP (pKa = 0.71).28 So the acidity of
TNP is stronger than DNP. In other words, TNP would make
receptor L more easily being protonated. This initial protonation
caused an electrostatic association between the picrate anions and
the protonated pyridine ends. To confirm this, the effect of pH
55 influence on the UVꢀVis response of receptor L was examined
(Fig. 6a).29,30 When pH was in the range of 6 to 14, the absorption
band centered at 336 nm was unchanged. A decrease of pH from
2 to 1 engendered a blueꢀshift in the maximum absorption
wavelength from 336 nm to 327 nm; this 9 nm shift was due to
60 protonation of the pyridine ring and the amine group to form Aꢀπꢀ
A structure. However when pH values changed from 3 to 5, the
main absorption peak engendered a redꢀshift to 396 nm; which
was due to protonation of the pyridine ring only, thus enhances
the electronꢀwithdrawing effect of the pyridine ring. The effect of
65 pH influence on the fluorescence response of receptor L was also
examined (Fig. 6b). The receptor L was fluorescent on account of
the ICT that occurs from the amine group to pyridine ring group.
However, when pH range is 1 to 6, the fluorescent intensity
reduces significantiy due to the arrest of the ICT process, because
70 of the protonation of either the pyridine ring or the amine group.
These results further confirmed that the spectra response of L to
TNP was attributed to the protonation of pyridine ring group by
the acidic behaviour of TNP. And that TNP also had an electronꢀ
deficient property which was the main reason that TNP could
75 quench the fluorescence.31,32
5
such as trifluoroacetic acid (TFA) in solution was also researched
1
10 by the method of H NMR titration (Figure S9, ESI†). The
signals of the hydrogens were downfield shifted, especially, Hb
and Hc were shifted obviously. These results further confirmed
that the ratiometric spectra response of L to TNP was attributed
to the protonation of the pyridine ring moiety by the acidic
15 behavior of TNP, but not the intermolecular electron or energy
transfer. In comparison with TFA, that has acidic character, TNP
also has an electronꢀdeficient property, which can protonate the
pyridine ring group more easily.
20
25
1
30 Fig. 4. The whole H NMR titration spectra (400 MHz) of the probe L
with TNP (0, 0.5, 1.0, 2.0 equiv.) in DMSOꢀd6.
Theoretical calculation
As shown in Fig. 5, the results revealed that the energy of the
highest occupied molecular orbital (HOMO) of the receptor L
35 was ꢀ5.03 eV and the energy of the lowest occupied molecular
orbital (LUMO) of L was ꢀ1.15 eV, while the energies of HOMO
Fig. 6. Effect of pH on the UVꢀVis response of L in water (a) on the
fluorescence response of L in water (b) and a scheme of the molecular
level interactions involved (c).
80 Conclusions
Fig. 5. HOMO and LUMO orbital of receptor L and L.TNP
calculated by B3LYP method with the 6ꢀ31G* basis set.
40
In conclusion, we have reported a simple and effective
pyridineꢀbased sensor (L) for the specific recognition of TNP.
The crystal structure of its TNP complex (L.TNP) was
successfully established by Xꢀray crystallography. In the complex
85 (L.TNP), picric acid exists as picrate ion upon deprotonation,
which leads to quenching of fluorescence of L.
and LUMO of the newly formed compound L.TNP were ꢀ6.09
eV and ꢀ2.99 eV, respectively, which indicated the charge transfer
from picrate to the sensor L. Meanwhile, the energies of the
newly formed compound L.TNP are minimum, which indicated
4

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25. A.L. Spek, PLATON, Acta Cryst. A, 1990, A46, C34.
26. Y.Q. Zhang, Y. Guo and Y.H. Joo, Chem. Eur. J., 2010, 16, 10778.
Acknowledgments
27. H.L. Liu, X.L. Hou and L. Pu, Angew. Chem. Int. Ed., 2009, 48, 382.
28. N. Dey, S.K. Samanta and S. Bhattacharya, Appl. Mater. Interfaces,
2013, 5, 8394.
This work was supported by the National Natural Science
Foundation of China (21101001, 50873001 and 61107014), the
Educational Commission of Anhui Province of China (no.
KJ20142D02).
60
29. H.P. Zhou, J.Q. Wang and Y.X. Chen, Dyes Pigm, 2013, 98, 1.
30. S.P. Wu, K.J. Du and Y.M. Sung, Dalton Trans, 2010, 39, 4363.
31. K.K. Kartha, S.S. Babu, S. Srinivasan and A. Ajayaghosh, J. Am.
Chem. Soc., 2012, 134, 4834.
5
References
a
Department of Chemistry, Key Laboratory of Functional Inorganic
65 32. V. Bhalla, S. Pramanik and M. Kumar, Chem. Commun., 2013, 49,
Materials of Anhui Province, Anhui University, Hefei 230039, P. R.
China.
895.
10 b State Key Laboratory Materials, Shandong University, Jinan 502100, P.
R. China.
CCDC: 987872
China.Tel: +86ꢀ551ꢀ63861279;
Eꢀmail:jxyang@ahu.edu.cn
kongꢀlin2009@126.com
15 † Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/b000000x/
1. B.W. Xu, X.F. Wu and H.B. Li, Macromolecules, 2011, 44, 5089.
2. F. Zhang, L. Luo and Y. Sun, Tetrahedron, 2013, 69, 9886.
20 3. E.B. Coropceanu, L. Croitor and A.V. Siminel, Polyhedron, 2014, 75,
73.
4. B.K. Dey, J. Dutta and M.G.B. Drew, J. Organomet. Chem., 2014, 750,
176.
5. M. Kumar, S.I. Reja and V. Bhalla, Org. Lett., 2012, 14, 6084.
25 6. a) V. Bhalla, A. Gupta and M. Kumar, Appl. Mater. Interfaces, 2013, 5,
672; b) Y. Salinas, R. MartínezꢀMáñez and M.D. Marcos, Chem. Soc.
Rev., 2012, 41, 1261.
7. a) Y.H. Lee, H.G. Liu and J.Y. Lee, Chem. Eur. J., 2010, 16, 5895; b)
W.S. Zou, F.H. Zou and Q. Shao, J. Photoch. Photobio. A, 2014, 278,
30
35
40
45
50
82.
8. K. Zhang, H.B. Zhou and Q.S. Mei, J. Am. Chem. Soc., 2011, 133,
8424.
9. G. He, N. Yan and J.Y. Yang, Macromolecules, 2011, 44, 4759.
10. V. Pimienta, R. Etchenique and T. Buhse, J. Phys. Chem. A, 2001, 105,
10037.
11. J.Y. Shen, J.F. Zhang and Y. Zuo, J. Hazard. Mater., 2009, 163, 1199.
12. J.F. Wyman, M.P. Serve and D.W. Hobson, J. Toxicol. Environ.
Health. Part A, 1992, 37, 313.
13. G. Anderson, J.D. Lamar and P.T Charles, Environ. Sci. Technol.,
2007, 41, 2888.
14. X.G. Hou, Y. Wu and H.T. Cao, Chem. Commun., 2014, 50, 6031.
15. J. Li, J.Z. Liu and B.Z. Tang, RSC Adv., 2013, 3, 8193.
16. V. Bhalla, S. Kaur and V. Vij, Inorg. Chem., 2013, 52, 4860.
17. N. Venkatramaiah, S. Kumar and S. Patil, Chem. Commun., 2012, 48,
5007.
18. G. Sivaraman, B. Vidya and D. Chellappa, RSC Adv., 2014, 4, 30828.
19. L. Hong, Q.S. Mei and L. Yang, Analytica Chimica Acta, 2013, 802,
89.
20. M. Jahan, Q.L. Bao and K.P. Loh, J. Am. Chem. Soc., 2012, 134,
6707.
21. V. Sathish, A. Ramdass and Z.Z. Lu, J. Phys. Chem. B, 2013, 117,
14358.
22. S. Kumar, P. Singh and A. Mahajan, Org. Lett., 2013, 15, 3400.
23. V. Bhalla, A. Gupta and M. Kumar, Org. Lett., 2012, 14, 3112.
55 24. L.J. Farrugia, J. Appl. Cryst., 1999, 32, 837.
5

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