Zwitterion formation and subsequent carboxylate-pyridinium NH synthon generation through isomerization of 2-anilinonicotinic acid

Article abstract of DOI:10.1039/c8ce01255e

Through structural modification of 2-anilinonicotinic acid by isomerization, the ΔpK_a between the carboxylic acid and pyridinium NH increased dramatically over the threshold to form zwitterions in the newly designed 4-anilinonicotinic acids. Th

Full text of DOI:10.1039/c8ce01255e

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Zwitterion formation and subsequent carboxylate–
pyridinium NH synthon generation through
isomerization of 2-anilinonicotinic acid†
Cite this: DOI: 10.1039/c8ce01255e
Received 28th July 2018,
Accepted 11th September 2018
Pengyun Yue,‡a Caiqiao Dong,‡b Mingtao Zhang, b Danrui Xu,a Sean Parkin,c
e
a
a
*
*
DOI: 10.1039/c8ce01255e
Tonglei Li, d Conggang Li,
Faquan Yu and Sihui Long
rsc.li/crystengcomm
Through structural modification of 2-anilinonicotinic acid by
isomerization, the ΔpKa between the carboxylic acid and
pyridinium NH increased dramatically over the threshold to form
zwitterions in the newly designed 4-anilinonicotinic acids. This in
turn led to the formation of a hydrogen bond between carboxylate
and pyridinium NH, and the absence of two commonly observed
synthons, i.e., the acid–acid homosynthon and acid–pyridine
heterosynthon. The new synthon has a stronger hydrogen bond
than the acid–acid homosynthon and the acid–pyridine
heterosynthon, as suggested by theoretical calculations. This,
together with the much larger ΔpKa, explains its formation.
dine N gives 2-ANAs the ability to form different synthons, in-
cluding an acid–acid homosynthon and an acid–pyridine
heterosynthon with the latter being energetically and statisti-
cally favored.6,12–16 However, structural modification, such as
the introduction of electronegative or sterically bulky func-
tional groups on 2-ANAs can change the result of the tug-of-
war between the two synthons, as demonstrated by a series
of studies performed by our group.5,17,18 Recently, structural
isomerization was found to exert a great influence on the
synthon formation of 6-anilinonicotinic acids, which are
structural isomers of 2-ANAs, leading to a new synthon, i.e.,
an acid–aminopyridine synthon in the solid state (Fig. 1).19
In this study, we further probe the impact of structural
isomerization on synthon formation of a new series of
compounds, 4-anilinonicotinic acids (4-ANAs). 4-ANAs are
also structural isomers of 2-ANAs, with the anilines at the
4-position of the nicotinic acid ring. Some 4-ANAs have been
found to show anti-inflammatory properties.20 With the ani-
line group at the ortho position relative to the carboxylic acid,
an intramolecular hydrogen bond between NH and the CO
of the COOH is expected, which eliminates the possibility of
the acid–aminopyridine hydrogen bond observed in 6-ANAs.
This paper addresses the question of what synthon will be
observed: the acid–acid homosynthon, the acid–pyridine
heterosynthon, or some new species due to possible intramo-
lecular proton transfer?
The feasibility of intramolecular proton transfer depends
on the pKa difference (ΔpKa) between pyridinium NH and
COOH. In 2-ANAs, most of the time, the intramolecular pro-
ton transfer was not observed with only a few exceptions,21,22
and in the six 6-ANAs studied, no intramolecular proton
transfer was found.23,24 The general rule-of-thumb for intra-
molecular proton transfer is that the ΔpKa must be greater
than 4.25,26 The calculated ΔpKa for two 2-ANAs, clonixin
(CLX) and 2-(p-tolylamino) nicotinic acid (TNA), is 3.63.27,28
For 6-ANAs, ΔpKa is expected to be smaller due to the steric
hindrance between pyridinium NH and either sp2C–H or the
bridging NH, which makes the protonation of pyridine N less
Material properties are directly correlated with structure. In
materials science and medicinal chemistry, subtle structural
modifications can produce dramatic variations in physical
properties. In compounds of pharmacological importance,
these can affect efficacy by altering bioactivities,
bioavailability, etc.1–4 In crystal engineering, molecular
structure variations are utilized to create new supramolecular
synthons in the solid state, and thus new properties/
applications for the entity.5–8
2-Anilinonicotinic acids (2-ANAs) are multifunctional com-
pounds with potential as nonsteroidal anti-inflammatory
drugs (NSAIDs). Clonixin and flunixin are two representative
NSAIDs.9–11 The presence of both carboxylic acid and pyri-
a Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key
Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical
Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan, Hubei, China.
E-mail: fyuwucn@gmail.com, sihuilong@wit.edu.cn, longsihui@yahoo.com;
Tel: +(027) 87194980, +(86) 15549487318
b Department of Chemistry, Nankai University, Tianjin, China
c Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
d Department of Industrial and Physical Pharmacy, Purdue University, West
Lafayette, Indiana, USA
e Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences,
Wuhan, Hubei, China
† Electronic supplementary information (ESI) available. CCDC 1856977–1856980.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c8ce01255e
‡ These authors contributed equally to this work.
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Fig. 1 Acid–acid and acid–pyridine synthons observed in 2-ANAs and acid–aminopyridine in 6-ANAs.
(Scheme 1).29 The pure compounds were subjected to crystal
growth from a variety of solvents.
A preliminary polymorph screening was carried out for
each compound. These compounds are not particularly solu-
ble in most common solvents used for crystal growth. Good
quality single crystals were only obtained for two of the
compounds (compounds 1 and 4). For compound 1, three
crystal forms including two polymorphs (forms 1-I and 1-II)
and one solvate (1-S) were harvested. For the other four
compounds, they were either not soluble in the solvents
used or the crystals were too thin for structure determina-
tion with single-crystal X-ray diffraction. All the crystals
formed were colorless, and showed various morphologies.
The two polymorphs of 1 crystallize in the monoclinic,
space group P21/c, while the solvate gave orthorhombic crys-
tals crystallize in the space group Pbca. The crystals of 4
crystallize in the monoclinic, space group C2/c. Crystallo-
graphic data are given in Table 1. For complete CIF files,
see the ESI.† All the crystals have only one molecule per
asymmetric unit (Z′ = 1) except for that of 1-II, which has
two independent molecules (Z′ = 2). All the molecules adopt
the E configuration. The molecules are nonplanar with
Fig. 2 Steric hindrance in both 2-ANAs and 6-ANAs.
likely (Fig. 2). With the anilino group at the 4-position, the
above steric interaction is no longer a concern, which should
make the pKa of pyridinium NH increase significantly com-
pared with that of both 2-ANAs and 6-ANAs, thus leading to a
higher ΔpKa for 4-ANAs, which should enable ready proton
transfer. With the proton now on the pyridine N, the acid–
acid homosynthon is prohibited, leaving the formation of a
carboxylate and pyridinium NH hydrogen bond the only pos-
sibility (Fig. 3).
To investigate the synthon formation in 4-ANAs, we syn-
thesized six 4-ANA derivatives and examined their solid-state
properties following the same general scheme as for 2-ANAs
Fig. 3 Possible synthons in 4-ANAs.
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Fig.
4
Superposition of all four molecular conformations in the
asymmetric units of the three forms of 1.
structures. Instead, an intermolecular hydrogen bond be-
tween the carboxylate of one molecule and the pyridinium
NH of another was formed due to intramolecular proton
transfer from the carboxylic acid to the pyridine N.
In form 1-I, the asymmetric unit contains one zwitterionic
molecule (Z′ = 1).30,31 It has a twisted conformation, with a
dihedral angle between the two aromatic rings of 42.24IJ5)°.
The molecules form one-dimensional chains sustained on
the hydrogen bond between carboxylate O and pyridinium
NH (C(6) by graph set annotation).32–34 The intermolecular
hydrogen bond has a bond distance and bond angle of
2.607(2) Å and 175.5IJ2)° for N1–H1⋯O9. In addition to the
intermolecular hydrogen bond, an intramolecular hydrogen
bond links the carboxylic acid carbonyl O and the NH bridg-
ing the two aromatic rings (S(6)32–34), with a bond distance of
2.612(2) Å and a bond angle of 138.0IJ1)°. Thus O9 forms
Scheme 1 Synthesis of 4-ANAs.
varying dihedral angles (1-I: 42.24IJ5)°; 1-IIA: 50.71IJ4)°, 1-IIB:
55.42IJ4)°; 1-S: 31.24IJ5)°; 4: 81.06IJ4)°).
Conformational variability in the forms of compound 1 is
readily apparent in a superposition of all four experimental
conformations (Fig. 4).
None of the conventional acid–acid homosynthon, the
acid–pyridine heterosynthon, and the newly discovered acid–
aminopyridine heterosynthon was observed in the crystal
Table 1 Crystallographic data of polymorphs and solvate of 1 (1-I, 1-II, and 1-S) and 4
1-I
1-II
1-S
4
Formula
Formula weight
C12H10N2O2
214.22
C12H10N2O2
214.22
C12H10N2O2,CO
246.26
C13H13N2O2Cl
262.5
Crystal size (mm)
Crystal system
Space group
0.36 × 0.12 ×0.10
Monoclinic
P21/c
0.40 × 0.20 × 0.05
Monoclinic
P21/c
0.20 × 0.20 × 0.05
Orthorhombic
Pbca
0.40 × 0.20 × 0.10
Monoclinic
C2/c
a/Å
b/Å
c/Å
α/°
10.8415(2)
13.7771(4)
6.9369(2)
90.00
13.8180(2)
11.3050(2)
13.5600(3)
90.00
11.5260(2)
7.2220(2)
26.9490(7)
90.00
12.2170(2)
10.6890(2)
18.2180(5)
90.00
β/°
γ/°
102.685(1)
90.00
107.6860IJ9)
90.00
90.00
90.00
90.039(1)
90.00 0
Z, Z′
1
2
8
16
V/Å3
1010.84(5)
1.408
90.0(2)
0.098
448
2018.12(6)
1.410
90.0(2)
0.098
896
2243.26(9)
1.458
90.0(2)
0.105
1040
2379.04(9)
1.394
90.0(2)
0.311
992
Dcal g−1 × cm−3
T/K
Abs coeff (mm−1
FIJ000)
)
q range (deg)
Limiting indices
1.00–27.48
−14 ≤ h ≤ 14
−17 ≤ k ≤ 17
−9 ≤ l ≤ 9
100%
1.55–27.49
−17 ≤ h ≤ 17
−14 ≤ k ≤ 14
−17 ≤ l ≤ 17
100%
3.024–27.499
−13 ≤ h ≤ 14
−9 ≤ k ≤ 9
−34 ≤ l ≤ 35
99.7%
2.24–27.49
−15 ≤ h ≤ 15
−13 ≤ k ≤ 7
−23 ≤ l ≤ 23
99.8%
Completeness to 2θ
Unique reflections
R1[I > 2σ(I)]
1596
0.0477
3503
0.0416
1811
0.0384
2335
0.0359
wR2 (all data)
0.1417
0.1191
0.1173
0.0934
CCDC accession code
1856977
1856978
1856979
1856980
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Fig. 5 Crystal packing of 1-I, 1-II, and 1-S. For clarity, only the hydrogens participating in hydrogen bonds are shown.
bifurcated hydrogen bonds with two hydrogen bond donors,
one being the bridging NH, and the other the pyridinium
NH35,36 (Fig. 5).
N10AH10A–O9A, and 2.614(1) Å and 136.9IJ1)° for N10BH10B–
O9B.
In the solvate 1-S, the solvent molecule was not strongly
hydrogen-bonded with the host molecule; thus it was not well
modeled. Still, molecules of 1 are connected with each other
through the carboxylate O and pyridinium NH hydrogen
bond (bond parameters: 2.598(2) Å, 176.0IJ3)°) in a way simi-
lar to that of form 1-II, forming one-dimensional chains
(C(6)). Meanwhile, the solvent molecule is associated with
Form 1-II consists of two zwitterionic molecules (A and B)
in the asymmetric unit (Z′ = 2), both of which have twisted
conformations, as shown by the dihedral angles between the
aromatic rings (50.71IJ4)° and 55.42IJ4)° for the A and B mole-
cules). The molecules self-associate into one-dimensional
chains by means of a hydrogen bond between carboxylate O
(O8) and pyridinium HN (C(6)), yet in a different way from
that of form 1-I, since the hydrogen bond acceptor is O8 in 1-
II rather than O9, and thus no bifurcated hydrogen bonds
are observed. The intermolecular hydrogen bond distances
and angles are: 2.645(1) Å and 173.4IJ2)° for N1AH1A–O8A,
and 2.673(1) Å and 164.5IJ2)° for N1BH1B–O8B. An intramo-
lecular hydrogen bond is formed between the carbonyl O
(O9) of the carboxylate and the anilino NH, with a bond dis-
tance of 2.614(1) Å and a bond angle of 137.9IJ1)° for
the host molecule through a OH⋯O hydrogen bond (dD-A
:
2.835 Å). An intramolecular S(6) hydrogen bond between NH
and carbonyl O (parameters of 2.648(2) Å and 140.1IJ1)°) is
also observed.
For compound 4, the two aromatic rings of the compound
are almost perpendicular to each other (dihedral angle:
81.06IJ4)°) (Fig. 6), likely due to the steric hindrance caused
by the methyl group at the ortho position of the aniline. Pro-
ton transfer again leads to a zwitterion. The hydrogen bond
is similar to that in form 1-II (parameters of 2.698(2) Å and
168.1IJ2)°), leading to one-dimensional chains. The intramo-
lecular hydrogen bond has parameters of 2.617(2) Å and
140.6IJ2)° (Table 2).
Table 2 Hydrogen bond parameters of NH⋯O (intermolecular) and
NH⋯O (intramolecular) in the four 4-ANA crystals
1-I
1-II
1-S
4
NH⋯O bond length (Å)
(intermolecular)
2.607(2) 2.645(1) 2.598(2) 2.698(2)
2.673(1)
NH⋯O bond angle (°)
175.5(2) 173.4(2) 176.0
164.5(2)
168.1(2)
(intermolecular)
NH⋯O bond length (Å)
(intramolecular)
2.612(2) 2.614(1) 2.648(2) 2.617(2)
2.614(1)
138.0(1) 137.9(1) 140.1(1) 140.6(2)
136.9(1)
Fig. 6 Single molecule of compound 4 with near orthogonal aromatic
rings (a), and one-dimensional hydrogen bond chain sustained on the
carboxylate O and pyridinium NH (b).
NH⋯O bond angle (°)
(intramolecular)
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Table 3 Calculated pKaIJs)
Quantum calculateda
Marvin calculatedb
pKa of acid
pKa of protonated base
ΔpKa
pKa of acid
pKa of protonated base
ΔpKa
2-ANA
4-ANA
6-ANA
2.97(2.22)
2.85(2.10)
4.60(3.85)
3.41(2.60)
6.43(5.62)
2.75(1.94)
0.44(0.38)
3.57(3.52)
−1.86IJ−1.94)
3.64
3.77
3.81
3.66
6.35
3.77
0.02
2.58
−0.04
a
Benzoic acid was selected as the reference for the acids, and pyridine for the bases. Values in the parentheses are based on the reference of
niacin. b Micromode was selected.
Intuitively, the aforementioned steric hindrance in 2- and
6-ANAs is eliminated in 4-ANAs due to the isomerization,
which results in 4-ANAs having a larger ΔpKa between
pyridinium NH and COOH. Still, we are keen to know as to
what degree the isomerization impacts the ΔpKa. Also as is
known, the proton transfer prohibits the formation of an
acid–acid homodimer, but it is intriguing to know if the for-
mation of the carboxylate–pyridinium NH hydrogen bond
could provide additional stability to the system, i.e., what is
the strength of the carboxylate–NH interaction, compared
with the conventional acid–acid and acid–pyridine dimers?
Two methods were used to calculate the ΔpKa (s) of 2/4/6-
ANA. The quantum method gave ΔpKa values of 0.44, 3.57
and −1.86 for 2/4/6-ANA, respectively. In contrast, the Marvin
approach generated ΔpKa values of 0.02, 2.58, and −0.04, re-
spectively (Table 3). Although the exact values given by the
two methods are different, the trend is obvious and consis-
tent, i.e., 4-ANA has a significantly higher ΔpKa than either
2-ANA or 6-ANA. Also, 2-ANA has a higher ΔpKa than 6-ANA.
As mentioned before, the ΔpKa values of 2-ANAs are at the
borderline of the higher end of the ΔpKa rule, a drastically
higher ΔpKa of 4-ANAs makes proton transfer from COOH to
pyridine N happen readily. This is in agreement with the ob-
servation made in the study. In addition, it also echoes the
fact that no proton transfer was observed in 6-ANAs.
To answer these questions, we performed
calculations.
a series of
All the structures discussed here were optimized from var-
ious initial conformations at the M06-2X/6-311G+(d,p)37–39
level of theory to identify the most stable conformations
using Gaussian16.40 The solvent effect of water was taken
into account by applying a SCRF (self-consistent reaction
field) through the SMD model.41 Frequency analysis of each
compound was performed at the same level to achieve the
optimized minimal/zero imaginary frequency, so that zero
point energies (ZPE) and Gibbs free energies (at 298.15 K and
1 atm) could be obtained. Intermolecular interactions were
calculated with the basis set superposition error (BSSE) con-
sidered by the counterpoise method.42 Dispersion energies
were evaluated using Grimme's DFT-D3 corrections.43 The
principle of pKa calculations can be found in the reference of
Shields and Zuilhof.44,45 In our calculations, benzoic acid
(pKa = 4.20) was selected as the reference for the acids, and
pyridine (pKa = 5.23) was selected as the reference for the ba-
ses because of its well-described pKa value. Niacin was also
The relative Gibbs free energies of zwitterionic 4-ANA and
five possible dimeric associations (acid–acid dimer, acid–pyri-
dine dimer 1, acid–pyridine dimer 2, carboxylate–pyridinium
NH dimer 1, and carboxylate–pyridinium NH dimer 2) (Fig. 7
and 8) in reference to the neutral single 4-ANA molecule were
calculated in water to be −3.49, 1.77, 0.12, 0.86, −5.39, and
−5.31 kcal mol−1 (Table 4). It is inferred that the zwitterion is
significantly more stable than the neutral species, and both
carboxylate–pyridinium NH dimers are much lower in energy
than the conventional acid–acid dimer and acid–pyridine di-
mers. This echoes the observation of both carboxylate–
pyridinium NH dimers in the crystal structures. It is likely
that both the higher ΔpKa of 4-ANAs and stronger inter-
molecular interactions contribute to the proton transfer in
the crystal formation.
2-/4-/6-Anilinonicotinic acids are potential NSAIDs with
both acidic and basic groups (i.e., ampholytes). They may be
able to exist in the zwitterionic state which could possess
both excellent stability and solubility, thus rendering them
desirable in the pharmaceutical industry.31 In this study, we
achieved the exclusive formation of zwitterions and
selected as a reference (pKa1 = 2.00 for the acid, and pKa2
=
4.82 for the protonated base) due to its similar structure to
these ANAs. A micromodel was selected while the pKa was
predicted by the protonation plugin of Marvin.46
Table 4 Relative Gibbs free energies
ΔG (kcal mol−1
)
4-ANA (monomer)
0
AA (acid–acid dimer)
1.77
0.12
0.86
−3.49
−5.39
−5.31
AP1 (acid–pyridine dimer)
AP2 (acid–pyridine dimer)
ZT (zwitterion)
CP1 (carboxylate–pyridinium dimer)
CP2 (carboxylate–pyridinium dimer)
Fig. 7 The optimized conformation of 4-ANA and its zwitterion.
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Fig. 8 Five possible dimeric associations of 4-ANA molecules.
subsequent carboxylate–pyridinium NH interaction for
4-ANAs through structural isomerization based on the ΔpKa
rule. This study attests to the general principle that the prop-
erties can be designed through a rational crystal engineering
approach.
5 S. Long, P. Zhou, S. Parkin and T. Li, Cryst. Growth Des.,
2014, 14, 27.
6 G. R. Desiraju, Angew. Chem., Int. Ed. Engl., 1995, 34, 2311.
7 A. I. Kitaigorodskii, Molecular Crystals and Molecules,
Academic Press New York, 1973.
8 D. Braga, F. Grepioni and G. R. Desiraju, Chem. Rev.,
1998, 98, 1375.
9 J. Berdahl, W. F. Wile and D. E. Saadeh, Pharmaceutical
Conflicts of interest
There are no conflicts to declare.
compositions
and
methods
for
anesthesiological
applications, U. S. Pat., US 20180177797, 2018.
10 M. H. Sherlock, U.S. Pat., US 3891761 A, 1975.
11 M. Takasuka, H. Nakai and M. Shiro, J. Chem. Soc., Perkin
Trans. 2, 1982, 2, 1061.
12 S. Long and T. Li, Cryst. Growth Des., 2009, 9, 4993.
13 M. Hemamalini, W. S. Loh, C. K. Quah and H. K. Fun,
Chem. Cent. J., 2014, 8, 31.
Acknowledgements
PY and SL thank the Natural Science Foundation of Hubei
Province (2014CFB787) for financial support. SP thanks the
National Science Foundation (NSF) MRI program, grants
CHE0319176 and CHE1625732.
14 R. Santra and K. Biradha, Cryst. Growth Des., 2009, 9,
4969.
References
1 E. Rutkowska, K. Pajak and K. Jóźwiak, Acta Pol. Pharm.,
2013, 70, 3.
2 C. Galdeano and A. Ciulli, Future Med. Chem., 2016, 8, 1655.
3 K. Szczepaniak, J. Ludwiczak, A. Winski and S. Dunin-
Horkawicz, J. Struct. Biol., 2018, 07, 002.
15 T. R. Shattock, K. K. Arora, P. Vishweshwar and M. J.
Zaworotko, Cryst. Growth Des., 2008, 8, 4533.
16 P. Vishweshwar, A. Nangia and V. M. Lynch, Cryst. Growth
Des., 2003, 3, 783.
17 S. Long and T. Li, Cryst. Growth Des., 2010, 10, 2465.
18 P. Chen, Z. Zhang, S. Parkin, P. Zhou, K. Cheng, F. Li, F. Yu
and S. Long, RSC Adv., 2016, 6, 81101.
4 M. Tang, W. Liu and X. Zhao, C. N. Pat., CN 108276608 A,
2018.
CrystEngComm
This journal is © The Royal Society of Chemistry 2018

View Article Online
CrystEngComm
Communication
19 S. Peng, F. Yu, D. Xu, C. Li, S. R. Parkin, T. Li, M. Zhang and S.
Long, Cryst. Growth Des., 2018, 18, 4849.
37 Y. Zhao and D. G. Truhlar, Theor. Chem. Acc., 2008, 120, 215.
38 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.
20 L. Navidpour, H. Shafaroodi, G. Saeedi-Motahar and A.
Shafiee, Med. Chem. Res., 2014, 23, 2793.
39 R. Krishnan, J. S. Binkley, R. Seeger and J. A. Pople, J. Chem.
Phys., 1980, 72, 650.
21 A. Maliakal, G. Lem, N. J. Turro, R. Ravichandran, J. C.
Suhadolnik, A. D. DeBellis, M. G. Wood and J. Lau, J. Phys.
Chem. C, 2002, 106, 7680.
22 N. Kanlayakan, K. Kerdpol, C. Prommin, R. Salaeh, W.
Chansen, C. Sattayanoon and N. Kungwan, New J. Chem.,
2017, 41, 8761.
23 C. Hoffmann, U.S. Pat., US 36661073 A, 1973.
24 S. Haim, Israeli. Pat., IL 1974-44328, 1978.
25 S. M. Pratik and A. Datta, J. Phys. Chem. B, 2016, 120, 7606.
26 A. J. Cruz-Cabeza, CrystEngComm, 2012, 14, 6362.
27 S. Long, T. Mao, P. Chen, M. Liu, S. Parkin, M. Zhang, T. Li,
P. Zhou and F. Yu, ChemistrySelect, 2017, 2, 4942.
28 A. Alvarez-Lueje, J. C. Sturm, L. J. Nunez-Vergara, J. Carbajo
and J. A. Squella, Anal. Lett., 2000, 33, 53.
40 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A.
Petersson, H. Nakatsuji, X. Li, M. Caricato, A. V. Marenich, J.
Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P.
Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D.
Williams-Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B.
Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G.
Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada,
M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K.
Throssell, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro,
M. J. Bearpark, J. J. Heyd, E. N. Brothers, K. N. Kudin, V. N.
Staroverov, T. A. Keith, R. Kobayashi, J. Normand, K.
Raghavachari, A. P. Rendell, J. C. Burant, S. S. Iyengar, J.
Tomasi, M. Cossi, J. M. Millam, M. Klene, C. Adamo, R.
Cammi, J. W. Ochterski, R. L. Martin, K. Morokuma, O.
Farkas, J. B. Foresman and D. J. Fox, Gaussian 16, Revision
A.03, Gaussian, Inc.: Wallingford, CT, 2016.
29 S. Long, S. Parkin, M. A. Siegler, A. Cammers and T. Li,
Cryst. Growth Des., 2008, 8, 4006.
30 S. S. Kumar and A. Nangia, Cryst. Growth Des., 2014, 14,
1865.
31 P. A. Williams, C. E. Hughes, G. K. Lim, B. M. Kariuki and
K. D. M. Harris, Cryst. Growth Des., 2012, 12, 3104.
32 J. Bernstein, R. E. Davis, L. Shimoni and N. L. Chang, Angew.
Chem., 1995, 107, 1689.
33 M. C. Etter, J. C. Macdonald and J. Bernstein, Acta
Crystallogr., Sect. B: Struct. Sci., 1990, 46, 256.
34 M. C. Etter, Acc. Chem. Res., 1990, 23, 120.
35 J. W. Meisel, C. T. Hu and A. D. Hamilton, Org. Lett.,
2018, 20, 3879.
41 A. V. Marenich, C. J. Cramer and D. G. Truhlar, J. Phys.
Chem. B, 2009, 113, 6378.
42 S. F. Boys and F. Bernardi, Mol. Phys., 1970, 19, 553.
43 S. Grimme, J. Antony, S. Ehrlich and H. Krieg, J. Chem.
Phys., 2010, 132, 154014.
44 M. D. Liptak, K. C. Gross, P. G. Seybold, S. Feldgus and G. C.
Shields, J. Am. Chem. Soc., 2002, 124, 6421.
45 S. Gangarapu, A. T. M. Marcelis and H. Zuilhof,
ChemPhysChem, 2013, 14, 990.
36 M. Arefian, M. Mirzaei and H. Eshtiaghhosseini, J. Mol.
Struct., 2018, 1156, 550.
46 http://www.chemaxon.com (accessed Marvin 18.15.0, 2018,
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