Two hydration products of 3,4,5,6-tetra-chloro-N-(methyl-2-pyrid-yl) phthalmic acids

Article abstract of DOI:10.1107/S0108270111022384

In 2-amino-6-methyl-pyridin-1-ium 2-carb-oxy-3,4,5,6-tetra-chloro-benzoate, C₆H₉N₂ ⁺·C ₈HCl₄O₄ ^-, there are two perpendicular chains of hydrogen-bonded ions, one arisi

Full text of DOI:10.1107/S0108270111022384

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Interestingly, as 3,4,5,6-tetrachlorophthalic acid cocrystallizes
with 2-amino-3-methylpyridin-1-ium 3,4,5,6-tetrachlorophthal-
ate all the products of this reaction are represented stoichio-
metrically in the crystal structure.
ISSN 0108-2701
Two hydration products of 3,4,5,6-
tetrachloro-N-(methyl-2-pyridyl)-
phthalmic acids
Paul G. Waddell,a,b Jeremy O. S. Hulsea and Jacqueline M.
Colea,b
*
aCavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge
CB3 0HE, England, and bDepartment of Chemistry, University of New Brunswick,
Fredericton NB, E3B 5A3, Canada
Correspondence e-mail: jmc61@cam.ac.uk
Received 26 April 2011
Accepted 9 June 2011
Online 23 June 2011
In 2-amino-6-methylpyridin-1-ium 2-carboxy-3,4,5,6-tetra-
+
chlorobenzoate, C6H9N2 ꢀC8HCl4O4ꢁ, there are two perpendi-
cular chains of hydrogen-bonded ions, one arising from the
interaction between 2-carboxy-3,4,5,6-tetrachlorobenzoate ions
and the other from the interaction between the 2-amino-6-
methylpyridin-1-ium and 2-carboxy-3,4,5,6-tetrachlorobenzo-
ate ions. These chains combine to form a two-dimensional
network of hydrogen-bonded ions. Cocrystals of bis(2-amino-3-
methylpyridin-1-ium) 3,4,5,6-tetrachlorophthalate–3,4,5,6-
The molecular geometry of the 2-amino-6-methylpyridin-1-
ium cation in the structure of (I) (Table 1) can be compared
with that of the nonhalogenated 2-amino-6-methylpyridinium
+
tetrachlorophthalic acid (1/1), 2C6H9N2 ꢀC8Cl4O42ꢁꢀC8H2-
Cl4O4, form finite aggregates of hydrogen-bonded ions. ꢀ–ꢀ
interactions are observed between 2-amino-3-methylpyridin-
1-ium cations. Both structures exhibit the characteristic R22(8)
motif as a result of the hydrogen bonding between the
2-aminopyridinium and carboxylate units.
¨ ¨
2-formylbenzoate monohydrate (Buyukgungor & Odaba-
s¸oglu, 2006). This geometry is similar in both compounds, with
¨
¨
˘
the characteristic bond-length alternation within the pyridyl
ring, which demonstrates the imino resonance stabilizing the
positive charge (Fig. 3) (Zhi et al., 2002). The bond geometry
of the aromatic ring in the 2-carboxy-3,4,5,6-tetrachloro-
benzoate anion in (I) resembles more closely that of the
hemihydrate of 3,4,5,6-tetrachlorophthalic acid (Ito et al.,
1975) than that of the 2-carboxy-3,4,5,6-tetrachlorobenzoate
in a similar salt, 2-methyl-5-ethylpyridinium 3,4,5,6-tetra-
chlorophthalate (Galloy et al., 1976). This indicates a contri-
bution from the neutral canonical form, which is also observed
Comment
N-(3-Methyl-2-pyridyl)-3,4,5,6-tetrachlorophthalmic acid and
N-(6-methyl-2-pyridyl)-3,4,5,6-tetrachlorophthalmic acid are
known to be pharamacologically active having been shown to
exhibit a hypertensive effect in biological systems (Dolzhenko
et al., 2003). In the context of this study, these materials are of
interest for their potential as a UV-active dye for dye-sensi-
tized solar-cell applications. Heating these compounds to
333 K in hydrated methanol produces crystals of two salts,
namely 2-amino-6-methylpyridin-1-ium 2-carboxy-3,4,5,6-
tetrachlorobenzoate, (I) (Fig. 1), and bis(2-amino-3-methyl-
pyridin-1-ium) 3,4,5,6-tetrachlorophthalate–3,4,5,6-tetrachloro-
phthalic acid (1/1), (II) (Fig. 2). These salts are the result of the
reaction of the starting material with water present in the
methanol solution and the equilibrium that exists between
amides and water and the corresponding amines and carb-
oxylic acids. In (I) and (II), protonation of the pyridyl N atom
results in pyridinium salts stabilized by imino resonance.
Figure 1
The structure of the asymmetric unit of (I), with atomic displacement
ellipsoids drawn at the 50% probability level.
Acta Cryst. (2011). C67, o255–o258
doi:10.1107/S0108270111022384
# 2011 International Union of Crystallography o255

organic compounds
Figure 2
The structure of the asymmetric unit of (II), with atomic displacement
ellipsoids drawn at the 50% probability level.
Figure 4
View of the C(7) hydrogen-bonding motif in the [001] direction in (I). H
atoms not involved in hydrogen bonding (dashed lines) have been
omitted.
Figure 3
The resonance exhibited by (I).
in the carboxylate group, where O3—C8 is observed to be
shorter than O4—C8. The bond distances in the aromatic ring
of 2-carboxy-3,4,5,6-tetrachlorobenzoate in (I) range from
˚
1.374 (9) to 1.403 (9) A.
Compound (I) forms continuous sheets of hydrogen-
bonded ions parallel to (010) (Table 2). These sheets contain
the characteristic rings having graph set R22(8) (Etter, 1990;
Bernstein et al., 1995) with the amine and pyridinium N atoms
acting as donors and the two carboxylate O atoms acting as
acceptors (N1—H1Nꢀ ꢀ ꢀO4 and N2—H2Bꢀ ꢀ ꢀO3), as is well
documented in this type of compound (Quah et al., 2010;
Hemamalini & Fun, 2010). These rings are linked by chain
motifs to form the sheets. The 2-carboxy-3,4,5,6-tetrachloro-
benzoate anions form chains parallel to the [001] direction
through O1—H1ꢀ ꢀ ꢀO4ii interactions to give a graph-set motif
of C(7) (symmetry codes as in Table 2). The 2-amino-6-
methylpyridin-1-ium cations link via the anions forming chains
with the graph sets C22(9) (through N2—H2Bꢀ ꢀ ꢀO3 and N2—
H2Aꢀ ꢀ ꢀO2i) and C22(11) (through N1—H1Nꢀ ꢀ ꢀO4 and N2—
H2Aꢀ ꢀ ꢀO2i), giving an overall C22(9)C22(11)[R22(8)] chain of
rings parallel to the [100] direction (Fig. 5).
Figure 5
View of the C22(9)C22(11)[R22(8)] chain of rings along [100] in (I). H atoms
not involved in hydrogen bonding (dashed lines) have been omitted.
respectively, altogether more consistent than the bond
distances of the 2-carboxy-3,4,5,6-tetrachlorobenzoate anion
in (I) or the hemihydrate of 3,4,5,6-tetrachlorophthalic acid.
This similarity in bond geometry between the dianion and the
neutral acid in (II) strengthens the argument for the contri-
bution of the neutral canonical forms in these compounds. As
The aromatic rings in the 2-amino-3-methylpyridin-1-ium
cations of compound (II) exhibit similar geometry to those in
(I) with regard to the bond distances (Table 3). The distances
in the benzene rings of the 3,4,5,6-tetrachlorophthalate
dianion and the 3,4,5,6-tetrachlorophthalic acid molecule are
˚
in the ranges 1.387 (3)–1.403 (2) and 1.389 (3)–1.399 (3) A,
+
ꢁ
+
o256 Waddell et al. C6H9N2 ꢀC8HCl4O4 and 2C6H9N2 ꢀC8Cl4O42ꢁꢀC8H2Cl4O4
Acta Cryst. (2011). C67, o255–o258
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organic compounds
Compound (I)
Crystal data
+
ꢁ
3
˚
V = 1623 (4) A
Z = 4
C6H9N2 ꢀC8HCl4O4
Mr = 412.04
Orthorhombic, Pca21
˚
a = 9.441 (14) A
b = 12.56 (2) A
˚
c = 13.69 (2) A
Mo Kꢁ radiation
ꢂ = 0.75 mmꢁ1
T = 120 K
0.33 ꢄ 0.16 ꢄ 0.06 mm
˚
Data collection
Rigaku Saturn724+ (2 ꢄ 2 bin
5083 measured reflections
2495 independent reflections
2302 reflections with I > 2ꢃ(I)
Rint = 0.048
mode) diffractometer
Absorption correction: multi-scan
(ABSCOR; Higashi, 1995)
Tmin = 0.866, Tmax = 0.956
Figure 6
Stereoview of the finite hydrogen-bonding network in the structure of
(II). H atoms not involved in hydrogen bonding (dashed lines) have been
omitted.
Refinement
R[F2 > 2ꢃ(F2)] = 0.057
wR(F2) = 0.127
S = 1.10
2495 reflections
218 parameters
1 restraint
H-atom parameteꢁrs3 constrained
˚
is observed in similar structures (Ni et al., 2007; Zhi et al.,
2002), there are ꢀ–ꢀ interactions between 2-amino-3-methyl-
pyridin-1-ium cations; the dihedral angle between the two
pyridinium rings in the selected asymmetric unit is only
3.8 (2)ꢃ and the corresponding centroid–centroid separation is
Áꢄmax = 0.44 e A
ꢁ3
˚
Áꢄmin = ꢁ0.50 e A
Absolute structure: Flack (1983)
Flack parameter: ꢁ0.31 (13)
˚
3.834 (2) A.
Compound (II)
Unlike the two-dimensional network observed in (I), the
hydrogen-bonded system in (II) consists of a finite array of
four 2-amino-3-methylpyridin-1-ium cations, two 3,4,5,6-
tetrachlorophthalate dianions and two molecules of 3,4,5,6-
tetrachlorophthalic acid (Fig. 6 and Table 4). The R22(8) ring
motifs formed between the pyridinium and phthalate ions are
once again present, with each phthalate dianion forming two
such rings parallel to each other because of the ꢀ–ꢀ inter-
actions between the pyridinium cations, i.e. through N2—
H2Aꢀ ꢀ ꢀO1 and N1—H1Nꢀ ꢀ ꢀO2 for one ring, and N4—H4Aꢀ ꢀ ꢀ
O3 and N3—H3Nꢀ ꢀ ꢀO4 for the other. In addition to this, each
of these rings is connected to an adjacent R22(8) ring through
N2—H2Bꢀ ꢀ ꢀO3i and N4—H4Bꢀ ꢀ ꢀO1i forming an [R22(8)-
R24(8)R22(8)] motif within an outer R44(16) ring (symmetry code
is as in Table 4). Further motifs are observed when considering
that there are two parallel [R22(8)R42(8)R22(8)] motifs linked by
the phthalate dianions; this gives rise to rings with graph sets
R44(18) and R44(22).
The 3,4,5,6-tetrachlorophthalic acid molecules and 3,4,5,6-
tetrachlorophthalate dianions are also connected by hydrogen
bonds with the acid protons donating to carboxylate O-atom
acceptors through O5—H5Oꢀ ꢀ ꢀO2 and O7—H7Oꢀ ꢀ ꢀO4 to
create R22(14) motifs. Though there is no direct hydrogen
bonding between the acid molecules and the pyridinium
cations, rings with the graph set R68(34) are formed between
acid molecules through the [R22(8)R42(8)R22(8)] motif.
Crystal data
+
2C6H9N2 ꢀC8Cl4O42ꢁꢀC8H2Cl4O4
ꢆ = 72.618 (1)ꢃ
V = 1621.7 (6) A
Z = 2
Mo Kꢁ radiation
ꢂ = 0.75 mmꢁ1
T = 120 K
3
˚
Mr = 824.08
Triclinic, P1
a = 8.6972 (17) A
˚
˚
˚
b = 13.762 (3) A
c = 15.381 (3) A
ꢁ = 69.388 (9)ꢃ
ꢅ = 75.342 (10)ꢃ
0.41 ꢄ 0.14 ꢄ 0.12 mm
Data collection
Rigaku Saturn724+ (2 ꢄ 2 bin
9810 measured reflections
5964 independent reflections
5551 reflections with I > 2ꢃ(I)
Rint = 0.033
mode) diffractometer
Absorption correction: multi-scan
(ABSCOR; Higashi, 1995)
Tmin = 0.881, Tmax = 0.914
Table 1
Selected geometric parameters (A, ) for (I).
ꢃ
˚
C7—O2
C7—O1
C8—O3
C8—O4
1.205 (7)
1.413 (8)
1.248 (8)
1.344 (8)
C9—N1
C9—N2
C13—N1
1.361 (9)
1.402 (10)
1.427 (10)
O2—C7—O1
O3—C8—O4
127.0 (6)
134.0 (5)
N1—C9—N2
C9—N1—C13
124.9 (6)
129.2 (5)
Table 2
Hydrogen-bond geometry (A, ) for (I).
Experimental
ꢃ
˚
N-(3-Methyl-2-pyridyl)-3,4,5,6-tetrachlorophthalmic acid (10 mg,
0.026 mmol) and N-(6-methyl-2-pyridyl)-3,4,5,6-tetrachlorophthal-
mic acid (10 mg, 0.026 mmol) were heated to 333 K in hydrated
methanol (5 ml) until a clear solution was obtained. Colourless plate-
like crystals of (I) were grown upon cooling to room temperature and
colourless prism-like crystals of (II) grew after the solution was
allowed to stand for one week.
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
N2—H2Bꢀ ꢀ ꢀO3
N2—H2Aꢀ ꢀ ꢀO2i
N1—H1Nꢀ ꢀ ꢀO4
O1—H1Oꢀ ꢀ ꢀO4ii
0.86
0.86
0.86
0.82
1.81
2.11
1.71
1.83
2.666 (8)
2.931 (8)
2.559 (7)
2.604 (7)
173
159
171
158
1
2
1
2
1
2
Symmetry codes: (i) x ꢁ ; ꢁy þ 1; z; (ii) ꢁx þ ; y; z þ .
+
ꢁ
+
C6H9N2 ꢀC8HCl4O4 and 2C6H9N2 ꢀC8Cl4O42ꢁꢀC8H2Cl4O4 o257
ꢂ
Acta Cryst. (2011). C67, o255–o258
Waddell et al.

organic compounds
Table 3
Selected geometric parameters (A, ) for (II).
by the ‘hole-in-one’ method and of x = 1.34 (13) using TWIN/BASF,
giving us confidence that we have presented the correct absolute
structure with respect to the polar-axis direction. These checks were
particularly important given that the precision of the Flack x para-
meter is poor owing to a low Friedel coverage of 60%. Refinement for
(II) was limited to those reflections with ꢇ < 25.68ꢃ reducing the
number of missing data; however, a number of missing data remain
(201 reflections between ꢇmin and sinꢇ/ꢈ = 0.600). Analysis of reci-
procal-space plots reveal that these missing portions are fairly
randomly dispersed which gives us confidence that this is not a
systematic error. Moreover, the missing data were comprised of high-
angle reflections that were just outside the reach of the data collec-
tion strategy.
ꢃ
˚
C7—O1
C7—O2
C8—O3
C8—O4
C15—O6
C15—O5
C16—O8
1.235 (3)
1.272 (3)
1.245 (3)
1.258 (3)
1.211 (3)
1.303 (3)
1.218 (3)
C16—O7
C17—N2
C17—N1
C21—N1
C23—N4
C23—N3
C27—N3
1.301 (3)
1.330 (3)
1.346 (3)
1.358 (3)
1.333 (3)
1.349 (3)
1.363 (3)
O1—C7—O2
O3—C8—O4
O6—C15—O5
O8—C16—O7
125.39 (19)
124.88 (19)
126.7 (2)
N2—C17—N1
C17—N1—C21
N4—C23—N3
C23—N3—C27
118.96 (19)
123.66 (18)
118.35 (18)
122.89 (18)
126.1 (2)
For both compounds, data collection: CrystalClear (Rigaku, 2008);
cell refinement: CrystalClear; data reduction: CrystalClear;
program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);
program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);
molecular graphics: SHELXTL (Sheldrick, 2008); software used to
prepare material for publication: WinGX (Farrugia, 1999).
Table 4
Hydrogen-bond geometry (A, ) for (II).
ꢃ
˚
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
O5—H5Oꢀ ꢀ ꢀO2
O7—H7Oꢀ ꢀ ꢀO4
N1—H1Nꢀ ꢀ ꢀO2
N2—H2Aꢀ ꢀ ꢀO1
N3—H3Nꢀ ꢀ ꢀO4
N4—H4Aꢀ ꢀ ꢀO3
N2—H2Bꢀ ꢀ ꢀO3i
N4—H4Bꢀ ꢀ ꢀO1i
0.84
0.84
0.88
0.88
0.88
0.88
0.88
0.88
1.80
1.83
1.83
2.07
2.01
1.93
1.99
2.07
2.558 (2)
2.593 (2)
2.708 (2)
2.943 (2)
2.891 (2)
2.805 (2)
2.823 (2)
2.892 (2)
149
151
173
171
175
175
157
156
JMC thanks the Royal Society for a University Research
Fellowship, the University of New Brunswick for the UNB
Vice-Chancellor’s Research Chair (JMC), and NSERC for
Discovery Grant No. 355708 (for PGW).
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GD3389). Services for accessing these data are
described at the back of the journal.
Symmetry code: (i) ꢁx þ 1; ꢁy þ 1; ꢁz þ 1.
Refinement
References
R[F2 > 2ꢃ(F2)] = 0.036
wR(F2) = 0.090
S = 1.07
435 parameters
H-atom parameteꢁrs3 constrained
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˚
Áꢄmax = 0.43 e A
¨
¨
¨
¨
˘
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ꢁ3
˚
5964 reflections
Áꢄmin = ꢁ0.34 e A
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˚
their parent atoms, with C—H = 0.95 A and Uiso(H) = 1.2Ueq(C), and
˚
N—H = 0.88 A and Uiso(H) = 1.2Ueq(N). Hydroxy and methyl H
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˚
atoms were modelled in a similar fashion, with O—H = 0.84 A and
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˚
Uiso(H) = 1.5Ueq(C), and C—H = 0.98 A and Uiso(H) = 1.5Ueq(N).
The most disagreeable reflections were omitted and those exhibiting
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from (II). The refinement was further improved by restricting the
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+
ꢁ
+
o258 Waddell et al. C6H9N2 ꢀC8HCl4O4 and 2C6H9N2 ꢀC8Cl4O42ꢁꢀC8H2Cl4O4
Acta Cryst. (2011). C67, o255–o258
ꢂ