Crystal and molecular structure of four 1:1 adducts from 2-methylquinoline and different acidic components

Article abstract of DOI:10.1016/j.molstruc.2011.11.004

Four 2-methylquinoline derived supramolecular complexes [2-methylquinoline: (2,4,6-trinitrophenol) [(HL)⁺ · (pic^-), pic ^- = picrate, L = 2-methylquinoline] (1), 2-methylquinoline: (5-nitrosalicylic acid) [(HL)⁺

Full text of DOI:10.1016/j.molstruc.2011.11.004

Journal of Molecular Structure 1010 (2012) 17–25
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Crystal and molecular structure of four 1:1 adducts from 2-methylquinoline
and different acidic components
a
b
a
Shouwen Jin a, , XingHua Lu , Daqi Wang , Wei Chen
⇑
a Tianmu College of ZheJiang A & F University, Lin’An 311300, PR China
b Department of Chemistry, Liaocheng University, Liaocheng 252059, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 June 2011
Received in revised form 13 October 2011
Accepted 5 November 2011
Available online 3 December 2011
Four 2-methylquinoline derived supramolecular complexes [2-methylquinoline: (2,4,6-trinitrophenol)
[(HL)+ Á (picÀ), picÀ = picrate, L = 2-methylquinoline] (1), 2-methylquinoline: (5-nitrosalicylic acid)
[(HL)+ Á (5-nsaÀ), 5-nsaÀ = 5-nitrosalicylate] (2), 2-methylquinoline: (5-sulfosalicylic acid): H2O
[(HL)+ Á (5-ssaÀ). H2O, 5-ssaÀ = 5-sulfosalicylate] (3), and 2-methylquinoline: (trimesic acid) [(L)Á Á Á(Tma),
Tma = trimesic acid] (4) were synthesized and structurally characterized by X-ray crystallography.
All supramolecular architectures of 1–4 involve extensive classical hydrogen bonds as well as other
noncovalent interactions. The results presented herein indicate that the strength and directionality of
the NAHÁ Á ÁO, OAHÁ Á ÁN, and OAHÁ Á ÁO hydrogen bonds (ionic or neutral) between acidic components
and 2-methylquinoline are sufficient to bring about the formation of binary organic acid–base adducts.
The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak
interactions combined, the complexes 1–4 displayed 2D–3D framework structure.
Keywords:
Crystal structure
2-Methylquinoline
Acidic compounds
Hydrogen bonds
Nonconventional interactions
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
involving the organic acid–base adduct concerning the Lewis base
of 2-methylquinoline.
Hydrogen bonding plays a crucial role in chemical, catalytic,
and biochemical processes, chemical and crystal engineering, as
well as in supramolecular chemistry [1–3]. During the last few dec-
ades, new types of hydrogen bonding have been found and exten-
sively studied [4,5], with particular attention to their spectral [6],
and structural [7,8] features.
Because of the predictable supramolecular properties and the
ability to form strong hydrogen bonds, carboxylic acids were fre-
quently chosen as building blocks for crystal engineering [9–11].
Numerous heterodimers composed of carboxylic acids and a vari-
ety of N-containing basic building blocks have been documented
recently [12–16]. The hydrogen bonding between hydroxyl groups
of carboxylic acids and heterocyclic nitrogen atoms has been
proved to be a useful and powerful organizing force for the forma-
tion of supramolecules. It should be noted that these structures are
normally held together by hydrogen-bonding, and in this regard,
the most frequently used moieties with hydrogen bonding capabil-
ity are pyridyl and carboxyl. As a pyridyl derivative, besides the
Following our previous works of acid–base adducts based on
N-aromatic derivatives and carboxylic acids [17–19], herein we
report the synthesis and crystal structure of four supramolecular
complexes assembled through hydrogen bonding interactions
between acidic synthons and 2-methylquinoline. In this study, we
got four organic acid–base adducts composed of acidic units and
2-methylquinoline (Scheme 1), namely 2-methylquinoline:
(2,4,6-trinitrophenol) [(HL)+ Á (picÀ), picÀ = picrate, L = 2-methyl-
quinoline] (1), 2-methylquinoline: (5-nitrosalicylic acid) [(HL)+ Á
(5-nsaÀ), 5-nsaÀ = 5-nitrosalicylate] (2), 2-methylquinoline: (5-sul-
fosalicylic acid): H2O [(HL)+ Á (5-ssaÀ). H2O, 5-ssaÀ = 5-sulfosalicy-
late] (3), and 2-methylquinoline: (trimesic acid) [(L) Á (Tma),
Tma = trimesic acid] (4).
2. Experimental section
2.1. Materials and methods
methyl group, 2-methylquinoline bears more aromatic
p electrons,
All reagents were commercially available and used as received.
The C, H, and N microanalysis were carried out with a Carlo Erba
1106 elemental analyzer. The FT-IR spectra were recorded from
KBr pellets in range 4000–400 cmÀ1 on a Mattson Alpha-Centauri
spectrometer. Melting points of new compounds were recorded
on an XT-4 thermal apparatus without correction.
which can be a better group in creating aromatic stacking interac-
tions. To the best of our knowledge there are very few reports
⇑
Corresponding author. Tel./fax: +86 571 6374 6755.
E-mail address: Jinsw@zafu.edu.cn (S. Jin).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.11.004

18
S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
OH
NO2
O2N
HO
HO
NO2
N
NO2
2,4,6-trinitrophenol
O
5-nitrosalicylic acid
2-methylquinoline
O
OH
HO
HO
O
O
HO
S
O
OH
O
O
HO
5-sulfosalicylic acid
Trimesic acid
Scheme 1. Hydrogen bond synthons discussed in this paper.
2.2. Preparation of supramolecular complexes
6 mL ethanol. Colorless crystals were afforded after several days
of slow evaporation of the solvent, yield: 64 mg, 84.35%. mp
142–144 °C. Elemental analysis: Calc. for C17H17NO7S (379.38): C,
53.77; H, 4.48; N, 3.69; S, 8.43. Found: C, 53.72; H, 4.39; N, 3.64;
2.2.1. 2-Methylquinoline: (2,4,6-trinitrophenol) [(HL)+ Á (picÀ)] (1)
To a methanol solution (2 ml) of 2-methylquinoline (28.6 mg,
0.2 mmol) was added 2,4,6-trinitrophenol (46 mg, 0.2 mmol) in
10 mL methanol. The solution was stirred for 10 min, then the
solution was filtered into a test tube. The solution was left standing
at room temperature for several days, yellow block crystals were
isolated after slow evaporation of the solution in air. The crystals
were dried in air to give the title compound [(HL+) Á (pic)À] (1),
yield 64 mg, 85.95%. mp 168–169 °C. Elemental analysis performed
on crystals exposed to the atmosphere: Calc. for C16H12N4O7
(372.30): C, 51.57; H, 3.22; N, 15.04. Found: C, 51.52; H, 3.16; N,
S, 8.38. Infrared spectrum (KBr disc, cmÀ1): 3596s(
m
(OH)),
s(NH)), 3112 m, 3062 m,
2954 m, 2842 m, 2716 m, 2464w, 2368 m, 2216 m, 1972w,
1836w, 1786w, 1716s( as(C@O)), 1664w, 1532 m, 1476w,
1262s( s(CAO)), 1186 m, 1120 m, 1058 m, 956 m, 902 m, 855 m,
3468s(multiple,
mas(NH)), 3366s(m
m
m
806 m, 748 m, 678 m, 616 m.
2.2.4. 2-Methylquinoline: (trimesic acid) [L Á Tma] (4)
14.94. Infrared spectrum (KBr disc, cmÀ1): 3464s(
3234s( s(NH)), 3188s, 3112s, 2936 m, 2870 m, 2822 m, 2376 m,
2322 m, 1740 m, 1666s, 1604s, 1556s, 1523s( as(NO2)), 1474 m,
1438 m, 1354s, 1322s( s(NO2)), 1256s, 1202 m, 1148 m, 1082 m,
mas(NH)),
To a methanol solution (2 ml) of 2-methylquinoline (28.6 mg,
0.2 mmol) was added trimesic acid (42 mg, 0.2 mmol) in 8 mL eth-
anol. Colorless prisms were afforded after several days of slow
evaporation of the solvent, yield: 50 mg, 70.76%. mp 204–206 °C.
Elemental analysis: Calc. for C19H15NO6(353.32): C, 64.53; H,
4.24; N, 3.96. Found: C, 64.51; H, 4.22; N, 3.87. Infrared spectrum
m
m
m
1021 m, 974 m, 916 m, 876 m, 837 m, 786 m, 718 m, 676 m,
620 m.
(KBr disc, cmÀ1): 3576s(
3065 m, 2496w, 1898w, 1712s(
1615 m, 1586 m, 1557 m, 1264s(
m
(OH)), 3146 m, 3106 m, 3085 m,
as(C@O)), 1681 m, 1659 m,
s(CAO)), 1192 m, 1032 m,
2.2.2. 2-Methylquinoline: (5-nitrosalicylic acid) [(HL)+ Á (5-nsaÀ)] (2)
To a methanol solution (2 ml) of 2-methylquinoline (28.6 mg,
0.2 mmol) was added 5-nitrosalicylic acid (36.6 mg, 0.2 mmol) in
4 mL ethanol. Colorless prisms were afforded after several days
of slow evaporation of the solvent, yield: 57 mg, 87.34%. mp
192–193 °C. Elemental analysis: Calc. for C17H14N2O5 (326.30): C,
62.52; H, 4.29; N, 8.58. Found: C, 62.46; H, 4.22; N, 8.54. Infrared
m
m
986 m, 924 m, 872 m, 823 m, 786 m, 745 m, 707 m, 658 m, 618 m.
2.3. X-ray crystallography
spectrum (KBr disc, cmÀ1): 3646s
as(NH)), 3348s( s(NH)), 3122 m, 3056 m, 2942 m, 2854 m,
2726 m, 2464w, 2366 m, 2224 m, 1982w, 1834w, 1782w,
1584s( as(NO2)), 1486w, 1392s(
as(COOÀ)), 1524s( s(COOÀ)),
1364 m, 1318s( s(NO2)), 1268 m, 1189 m, 1121 m, 1068 m,
(m(OH)), 3466s(multiple,
Suitable crystals were performed on a Bruker SMART 1000 CCD
diffractometer using Mo Ka radiation (k = 0.71073 Å). Data collec-
m
m
tions and reductions were performed using the SMART and SAINT
software [20,21]. The structures were solved by direct methods,
and the non-hydrogen atoms were subjected to anisotropic refine-
ment by full-matrix least squares on F2 using SHELXTL package
[22]. Hydrogen atom positions for the four structures were gener-
ated geometrically. Further details of the structural analysis are
summarized in Table 1. Selected bond lengths and angles for com-
plexes1–4 are listed in Table 2, the relevant hydrogen bond param-
eters are provided in Table 3.
m
m
m
m
972 m, 904 m, 856 m, 808 m, 762 m, 694 m, 626 m.
2.2.3. 2-Methylquinoline: (5-sulfosalicylic acid): H2O [(HL)+
Á
(5-ssaÀ) Á H2O] (3)
To a methanol solution (2 ml) of 2-methylquinoline (28.6 mg,
0.2 mmol) was added 5-sulfosalicylic acid (43.6 mg, 0.2 mmol) in

S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
19
Table 1
Summary of X-ray crystallographic data for complexes 1–4.
1
2
3
4
Formula
Fw
C
16H12N4O7
C17H14N2O5
326.30
C17H17NO7S
379.38
C19H15NO6
353.32
372.30
T, K
298(2)
298(2)
298(2)
298(2)
Wavelength, Å
Crystal system
Space group
a, Å
b, Å
c, Å
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
0.71073
Monoclinic
P2(1)/c
8.8164(6)
14.3480(16)
14.0002(13)
90
104.4390(10)
90
1715.1(3)
4
1.469
0.230
792
0.47 Â 0.40 Â 0.25
2.39–25.02
À8 6 h 6 10
À17 6 k 6 15
À16 6 l 6 16
8351
0.71073
Triclinic
P-1
8.1184(9)
9.2331(11)
11.7013(16)
71.0570(10)
76.0760(10)
84.359(2)
805.03(17)
2
1.536
0.124
384
0.42 Â 0.35 Â 0.13
1.89–25.02
À9 6 h 6 9
À10 6 k 6 5
À13 6 l 6 12
4229
7.1158(6)
9.5738(8)
11.7604(12)
80.3870(10)
72.9660(10)
87.811(2)
755.23(12)
2
1.435
0.108
340
0.49 Â 0.48 Â 0.45
2.60–25.02
À6 6 h 6 8
À11 6 k 6 11
À13 6 l 6 12
3951
9.1239(8)
13.4631(12)
14.5106(16)
73.3720(10)
76.6220(10)
88.549(2)
1659.9(3)
4
1.414
0.107
736
0.47 Â 0.32 Â 0.21
1.51–25.02
À5 6 h 6 10
À15 6 k 6 16
À17 6 l 6 17
8675
a
, deg.
b, deg.
c
, deg.
V, Å3
Z
Dcalcd, Mg/m3
Absorption coefficient, mmÀ1
F(000)
Crystal size, mm3
h range, deg
Limiting indices
Reflections collected
Reflections independent (Rint
)
2795 (0.0286)
1.006
2642 (0.0214)
1.016
3025 (0.0350)
1.023
5751 (0.0264)
0.993
Goodness-of-fit on F2
R indices [I > 2
r
I]
0.0517, 0.1122
0.1309, 0.1469
0.201, À0.191
0.0451, 0.1049
0.0884, 0.1362
0.203, À0.153
0.0428, 0.0998
0.0690, 0.1185
0.338, À0.301
0.0506, 0.1201
0.1101, 0.1596
0.265, À0.275
R indices (all data)
Largest diff. peak and hole, e.ÅÀ3
Table 2
solvents in 1:1 ratio, which was allowed to evaporate at ambient
conditions to give the final crystalline products. The molecular
structures and their atom labelling schemes for the four structures
are shown in Figs. 1, 3, 5, and 7, respectively.
Selected bond lengths [Å] and angles [°] for 1–4.
1
N(1)AC(2)
O(1)AC(11)
1.325(4)
1.243(3)
N(1)AC(6)
C(2)AN(1)AC(6)
1.368(4)
124.1(3)
The elemental analyses for the four compounds are in good
agreement with their compositions. The infrared spectra of 1–4
are consistent with their chemical formulas determined by ele-
mental analysis and further confirmed by X-ray diffraction analy-
sis. The very strong and broad features at 3700–3200 cmÀ1 arise
from OAH or NAH stretching frequencies. Aromatic and quinoline
ring stretching and bending are in the regions of 1500–1630 cmÀ1
and 600–750 cmÀ1, respectively. The intense peak at ca. 1710 cmÀ1
was derived from the existence of the C@O stretches, and the band
at ca. 1260 cmÀ1 exhibited the presence of the CAO stretches of the
COOH moieties. The presence of two broad bands at ca. 2500 cmÀ1
and 1900 cmÀ1 in compound 4, characteristic of a neutral OAHÁ Á ÁN
hydrogen-bond interaction, was viewed as evidence for co-crystal
formation [23]. Except for the above bands, for 1, and 2, the bands
2
N(1)AC(2)
N(2)AO(5)
N(2)AC(16)
O(2)AC(11)
C(2)AN(1)AC(6)
O(2)AC(11)AO(1)
1.324(3)
1.218(3)
1.459(3)
1.224(3)
123.9(2)
124.2(2)
N(1)AC(6)
N(2)AO(4)
O(1)AC(11)
O(3)AC(13)
O(5)AN(2)AO(4)
1.371(3)
1.228(3)
1.290(3)
1.341(3)
122.6(2)
3
S(1)AO(6)
S(1)AO(4)
N(1)AC(1)
O(1)AC(11)
O(3)AC(13)
O(6)AS(1)AO(4)
C(1)AN(1)AC(5)
1.4354(18)
1.4672(18)
1.321(4)
1.218(3)
1.345(3)
S(1)AO(5)
S(1)AC(16)
N(1)AC(5)
O(2)AC(11)
O(6)AS(1)AO(5)
O(5)AS(1)AO(4)
O(1)AC(11)AO(2)
1.4450(19)
1.759(3)
1.370(4)
1.311(3)
113.62(12)
110.89(11)
123.2(2)
112.63(12)
124.3(2)
4
at ca. 1520 and 1320 cmÀ1 were attributed to the
s(NO2), respectively [24].
IR spectroscopy has also proven to be useful for the recognition
mas(NO2) and
N(1)AC(1)
1.314(4)
1.320(4)
1.260(3)
1.264(3)
1.202(3)
1.261(3)
1.261(3)
1.294(3)
119.7(3)
123.9(2)
125.4(3)
123.9(3)
N(1)AC(9)
N(2)AC(19)
O(2)AC(21)
O(4)AC(22)
O(6)AC(23)
O(8)AC(30)
O(10)AC(31)
O(12)AC(32)
C(11)AN(2)AC(19)
O(4)AC(22)AO(3)
O(7)AC(30)AO(8)
O(12)AC(32)AO(11)
1.377(4)
1.374(4)
1.261(3)
1.263(3)
1.305(3)
1.270(3)
1.264(3)
1.203(3)
120.1(3)
123.9(3)
123.0(3)
125.3(3)
m
N(2)AC(11)
O(1)AC(21)
O(3)AC(22)
O(5)AC(23)
O(7)AC(30)
O(9)AC(31)
O(11)AC(32)
C(1)AN(1)AC(9)
O(1)AC(21)AO(2)
O(5)AC(23)AO(6)
O(9)AC(31)AO(10)
of proton transfer compounds [25]. The most distinct feature in the
IR spectrum of proton transfer compounds is the presence of strong
asymmetrical and symmetrical carboxylate stretching frequencies
at 1550–1610 cmÀ1 and 1300–1420 cmÀ1 in compound 2 [26].
3.2. X-ray structure of 2-methylquinoline: (2,4,6-trinitrophenol) (1)
Salt 1 was prepared by reacting of a methanol solution of 2,4,6-
trinitrophenol and 2-methylquinoline in 1:1 ratio, which crystal-
lizes as triclinic pale yellow crystals in the centrosymmetric space
group P-1. The asymmetric unit of 1 consists of one cation of
2-methylquinolinium and one anion of picrate, as shown in
Fig. 1. In the compound, there is one pair of ion pair with no
included solvent molecules, which is well agreement with the
micro-analysis results.
3. Results and discussion
3.1. Syntheses and general characterization
For the preparation of 1–4, the acidic derivatives were mixed
directly with 2-methylquinoline in methanol and/or ethanol

20
S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
Table 3
Hydrogen bond distances and angles in studied structures 1–4.
DAHÁ Á ÁA
d(DAH) [Å]
d(HÁ Á ÁA) [Å]
d(DÁ Á ÁA) [Å]
<(DHA) [°]
1
N(1)AH(1)Á Á ÁO(2)#1
0.86
0.86
2.29
1.93
2.857(3)
2.749(3)
123.5
158.2
N(1)AH(1)Á Á ÁO(1)#1
2
O(3)AH(3)Á Á ÁO(1)
0.82
0.86
1.76
1.81
2.494(2)
2.666(3)
148.7
173.6
N(1)AH(1)Á Á ÁO(1)#1
3
O(7)AH(7D)Á Á ÁS(1)
O(7)AH(7D)Á Á ÁO(5)
O(7)AH(7C)Á Á ÁS(1)#1
O(7)AH(7C)Á Á ÁO(4)#1
O(3)AH(3)Á Á ÁO(1)
O(2)AH(2)Á Á ÁO(4)#2
N(1)AH(1)Á Á ÁO(7)
0.85
0.85
0.85
0.85
0.82
0.82
0.86
2.80
1.91
3.00
1.89
1.87
1.83
1.82
3.492(2)
2.751(3)
3.754(2)
2.729(3)
2.596(3)
2.629(2)
2.667(3)
139.8
168.3
148.5
168.2
146.3
163.9
168.0
4
O(11)AH(11)Á Á ÁN(1)#1
O(10)AH(10)Á Á ÁO(3)#2
O(7)AH(7)Á Á ÁO(2)
O(6)AH(6)Á Á ÁN(2)#3
O(4)AH(4)Á Á ÁO(9)#4
O(1)AH(1A)Á Á ÁO(8)
0.82
0.82
0.82
0.82
0.82
0.82
1.82
1.85
1.78
1.84
1.79
1.83
2.572(3)
2.650(3)
2.588(3)
2.602(3)
2.593(3)
2.636(3)
151.3
166.3
166.0
153.4
167.4
167.5
Symmetry transformations used to generate equivalent atoms for 1: #1 x, y À 1, z. Symmetry transformations used to generate equivalent atoms for 2: #1 x, y + 1, z.
Symmetry transformations used to generate equivalent atoms for 3: #1 x, Ày + 1/2, z À 1/2; #2 x+ 1, y, z. Symmetry transformations used to generate equivalent atoms for 4:
#1 Àx + 1, Ày + 1, Àz + 1; #2 x À 1, y À 1, z; #3 x À 1, y, z + 1; #4 x+ 1, y + 1, z.
The mean value of CAC and NAC bond lengths are 1.379 (4) and
1.346 (4) Å respectively, which are between that of a single bond
and a double bond and agree with those values in the literature
[29]. The CANAC angles of pyridine are very sensitive to proton-
ation [30,31]. A pyridinium cation always possesses an expanded
angle of CANAC in comparison with the parent pyridine. The angle
of C(2)AN(1)AC(6) [124.1(3)] is consistent with a type of pyridini-
um cation. The hydrogen atom H(N1), which is deprived from its
parent, attaches the nitrogen atom.
One 2-methylquinolinium cation and one 2,4,6-trinitropheno-
late anion form a heterodimer through hydrogen bonding interac-
tions. The NH+ group formed bifurcate N+AHÁ Á ÁO hydrogen bonds
with the picrate. One is the ionic N+AHÁ Á ÁOÀ hydrogen bond pro-
duced between the NH+ cation of 2-methylquinolinium and the
oxygen atom of the 2,4,6-trinitrophenolate ions with NAO distance
of 2.749 Å, and HÁ Á ÁO distance of 1.93 Å. The N+AHÁ Á ÁOÀ bond angle
Fig. 1. The structure of 1, showing the atom-numbering scheme. Displacement
ellipsoids were drawn at the 30% probability level.
(158.2°), the NÁ Á ÁO and HÁ Á ÁO bond lengths are consistent with val-
ues reported from a study of N+AHÁ Á ÁOÀ hydrogen bonding in
organic salts [32]. The other NAH+Á Á ÁO hydrogen bond is produced
This is a salt where the OH groups of 2,4,6-trinitrophenol are
ionized by proton transfer to the nitrogen atom (N(1)) of the
2-methylquinoline moieties, which is also confirmed by the bond
distance of O(1)–C(11) (1.243(3) Å) for phenolate (1.24 0.01 Å)
[27].
between the NH+ group and the NO2 group with NAO distance of
2.857 Å, and HÁ Á ÁO distance of 2.29 Å. Compared with the above
ionic N+AHÁ Á ÁOÀ hydrogen bond, this hydrogen bond is more
weaker. These two hydrogen bonding interactions generate a
R21(6) ring motif according to Bernstein et al. [33]. There was also
a CH3AO interaction between the methyl group of the cation and
the oxygen atom of the 2,4,6-trinitrophenolate anion in the same
heterodimer with CAO distance of 3.443 Å. In compound 1, there
also exist strong electrostatic interactions between charged cation
units of NH+ and the picrate anions.
Examination of the cationic moiety shows that the atoms
C2–C10, and N1 of the quinolinium ring of the title compound have
a good coplanarity and they form a conjugated plane with average
deviation of 0.0152 Å. The benzene ring of the picrate is almost pla-
nar with r.m.s. deviation of 0.0066 Å. The dihedral angle between
the aromatic ring of the cation and the benzene ring of the picrate
is 95.9°, indicating an almost perpendicular arrangement of both
rings. The ortho-nitro groups (N2AO2AO3, and N4AO6AO7) devi-
ate from the benzene plane and have dihedral angles of 10.4 (2)°,
and 115.4° respectively with the benzene ring of the anion, and
the two ortho-nitro groups intersect at an angle of 116.4 (2)°.
While the para-nitro group lies in the benzene plane [with dihedral
angle of 0.9 (1)° between N3AO4AO5 group and the benzene ring
of the picrate], which is similar to the organic salt concerning
picrates [28].
The adjacent heterodimers were connected together through
the CHAO association between the CH of one anion and the NO2
of its adjacent anion with CAO distance of 3.339 Å to form a chain
running along the a axis direction. Adjacent chains were joined
together through CHAO association between the 3-CH of the cation
and the o-NO2 group of the anion with CAO distance of 3.344 Å to
form a 2D grid extending on the ac plane as shown in Fig. 2. In the
grid the cations were protruded from the plane determined by the
anion chain. In the grid there are 26-membered rings composed of
three picrates and two cations and 13-membered rings composed

S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
21
Fig. 2. 2D grid structure of 1 viewed down the b axis.
of two picrates and one cation. Two adjacent grids were connected
together along the b axis direction through the CHAO interaction
between the 8-CH of the cation at one grid and the o-NO2 group
compound based on 5-nsaÀ [35]. As expected the OAO separation
is essentially in the range of the documented data [2.489–2.509 Å]
[35] because of the planarity of the hydrogen bonded carboxylate
unit, but it is slightly contracted compared with the nonproton
transfer examples (2.547–2.604 Å, mean: 2.588 Å), as a result of
deprotonation. The 5-nitro group also varies little conformationally
[torsion angle C15AC16AN2AO5, 178.4°] compared with the
reported data within this set of compounds (175.4–180°) [35].
The rms deviation of the quinoline ring excluding the CH3 group
is 0.0181 Å. The rms deviation of the benzene ring of the anion is
0.0094 Å. They make dihedral angle of 73.1° with each other.
One cation and one anion were held together by N+AHÁ Á ÁOÀ
hydrogen bond between one O atom of the carboxylate group
and the NH+ group to form a heterosynthon, the heterosynthons
were joined together by CHAO interaction between the other O
atom of the same carboxylate group and 5-CH of the cation with
CAO distance of 3.301 Å to form a dimer. In this dimer the cations
were antiparallelly arranged. And the two anions were inversional-
ly located around the cations. There are no aromatic stacking inter-
actions between the two antiparallelly arranged cations. The
dimers were further joined together by the CHAO interaction
between the 8-CH of the cation and the nitro group with CAO dis-
tance of 3.201 Å to form a 1D chain running along the diagonal
direction of the bc plane. The adjacent 1D chains were linked to-
of its neighboring grid with CAO distance of 3.168 Å, and O–
p
interactions between the o-nitro group and the aromatic ring of
the cation with OACg distance of 3.131 Å to form a double layer
structure. In the double layer structure the cations of the second
grid were located just in the center of the 26-membered ring of
the first grid. And the corresponding anions and cations of adjacent
grids were antiparallelly arranged respectively. Such double grids
were stacked along the b axis direction through the intergrid
CH3AO interaction between the 2-CH3 of the cation and the
p-NO2 group of the anion with CAO distance of 3.627 Å to form a
3D layer network structure.
3.3. X-ray structure of 2-methylquinoline: (5-nitrosalicylic acid) [(HL)+
Á Á Á(5-nsaÀ)] (2)
The crystal structure of 2 consists of one monoanion of 5-nitro-
salicylic acid, and one cation of 2-methylquinolinium in the asym-
metric unit (Fig. 3). The proton of the COOH group has transferred
to the ring N atom of the quinoline moiety. The assignment of 2 as
a salt is based on successful refinement of the relevant H atoms
using X-ray data also. This is confirmed by the CAO distances
gether by CH3–p interactions between the CH3 of the cation and
(O(1)AC(11), 1.290(3) Å), O(2)AC(11), 1.224(3) Å with
D =
the benzene ring of the anion with CACg distance of 3.642 Å to
form a 2D sheet extending on the bc plane (Fig. 4). These sheets
were further stacked along the a axis direction to form a 3D net-
work structure through CH3AO interactions between the CH3 of
the cation and the carboxylate O atom with CAO distance of
3.426 Å, and CHAO interactions between the 3-CH of the cation
and the NO2 group with CAO distance of 3.301 Å. Here the adjacent
sheets were slipped some distance from each other along the b, and
c axis directions, respectively.
0.066 Å] in the carboxylate group, which is in the range for the
OAC distances concerning the deprotonated carboxyl groups. In
the compound, there is one ion pair without solvent molecules,
which fits well with the micro-analysis results.
In the cation, the angle C(6)AN(1)AC(2) [123.9(2)°] is almost
the same as that in 1 (124.1(3)°). Because of the presence of the
intramolecular hydrogen bond between the carboxylate group
and the phenol group (O(3)AH(3)Á Á ÁO(1), 2.494(2) Å), it is gener-
ally expected and found that the carboxylate group is essentially
coplanar with the benzene ring [torsion angle C13AC12AC11AO2,
172.64°]. This feature is similar to that found in salicylic acid [34],
and in the previously reported structure of proton-transfer
3.4. X-ray structure of 2-methylquinoline: (5-sulfosalicylic acid): H2O
[(HL)+Á Á Á(5-ssaÀ)Á Á ÁH2O] (3)
Similar to compound 2, the compound 3 is also an organic salt.
In 3 the asymmetric unit is occupied by one monoanion of 5-sulfo-
salicylic acid, one cation of 2-methylquinolinium (HL)+, and one
water molecule (Fig. 5). Here only one proton of the 5-sulfosalicylic
acid has transferred to the N atom of L. In this case it is the proton
of the SO3H group not other protons such as the phenol H and the
carboxyl H that have been deprotonated. The reason could be that
a sulfonic acid is a stronger acid than a carboxylic acid.
The SAO distances in SOÀ3 are ranging from 1.4354(18) to
1.4672(18) Å (
D is 0.0318 Å) which is in the range of the monode-
protonated 5-saaÀ anion (1.435 (2)–1.4599 (17) Å) [36]. The CAO
bond distance (O(3)AC(13) 1.345(3) Å) is in the range of the
neutral CAO bond distance in the phenol derivatives (1.344 (3)–
1.357 (3) Å) [36]. In the COOH group, two CAO bond lengths are
Fig. 3. The structure of 2, showing the atom-numbering scheme. Displacement
ellipsoids were drawn at the 30% probability level.

22
S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
Fig. 4. 2D sheet structure of 2 extending on the bc plane.
with CACg distance of ca. 3.330 Å and CHAO interactions between
the SOÀ3 group and 3-CH of the anion with CAO distance of 3.333 Å
to form a double chain structure. Unlike the anions in the same
chain, here the anions in these two chains were antiparallelly
arranged. The cations were bound to the anion chain through three
CHAO contacts, of which two are formed between the same sulfo-
nyl O atom and 4-CH, and 5-CH of the same cation to produce a
R22(6) ring motif with CAO distances of 3.328 and 3.470 Å respec-
tively, the other is produced between OH of the carboxyl group
and 3-CH of the cation with CAO distance of 3.392 Å.
The lattice water molecules (acceptor) were bound to the cat-
ions through N+AHÁ Á ÁO hydrogen bond with NAO distance of
2.667(3) Å, thus there are no direct classical hydrogen bond inter-
actions between the cations and the anions (the water molecule
blocked the donor position of the cation so that the NH+ groups
have no classical hydrogen bonding interaction with the anion).
Besides as acceptors, the water molecules also formed two hydro-
gen bonds in bifurcate mode via the same OH group (donor), one is
the OAHÁ Á ÁO hydrogen bond formed between the OH group of the
water and the sulfonyl group of the neighboring anion chain at the
c axis direction with OAO distance of 2.751(3) Å, the other is the
OAHÁ Á ÁS interaction formed between the same OH unit and the S
atom of the sulfonyl group of the neighboring anion chain at the
c axis direction with OAS distance of 3.492(2) Å. Under these inter-
actions, the water molecules linked the double anion chains and
the cations together to give a 2D double layer sheet structure
(Fig. 6). The double layer sheets were further stacked along the c
Fig. 5. The structure of 3, showing the atom-numbering scheme. Displacement
ellipsoids were drawn at the 30% probability level.
obviously different between O(1)AC(11) (1.218(3) Å) and
O(2)AC(11) (1.311(3) Å) (
D is 0.093 Å) bearing the characteristic
CAO bonds for the COOH groups, which are also confirming the
reliability of adding H atoms experimentally by different electron
density onto O atoms as mentioned above.
The angle [124.3(2)°] around the protonated N atom (N1) is
similar to the corresponding angle in compound 1 [124.1(3)], 2
[123.9(2)°], and the saccharate salt of 2-methylquinoline
(123.7(3)°) [37].
axis direction through the
p–p stacking interactions between the
cation aromatic ring and the anion benzene ring with the
centroid–centroid separation of 3.313 Å to form a 3D layer network
structure. Like 2, the usual intramolecular hydrogen bond is
found between the phenol OH group and a carboxyl O atom
[O(3)AH(3)Á Á ÁO(1); OAO@2.596(3) Å], essentially giving coplana-
rity of the carboxylic acid group and the benzene ring [torsion
angle O(2)AC(11)AC(12)AC(13); À177.48(3)°]. For the presence
of this hydrogen bond, compound 3 also bears the S11(6) loop
motif. This hydrogen bond geometries were similar to the docu-
mented data [36], and the data in compound 2 also.
The rms deviation of the cation excluding the methyl group
is 0.0055 Å. The rms deviation of the benzene ring of the anion is
0.0024 Å. Both planes make dihedral angle of 22.9(3)°, which
is smaller than the corresponding value in 2.
The 5-ssaÀ anions formed a 1D chain along the a axis direction
through OAHÁ Á ÁO hydrogen bonding interactions between the OH
group of the COOH and the SOÀ3 with OAO distance of 2.629(2) Å. In
the chain the 5-ssaÀ anions were parallel to each other and
arranged in head to tail fashion. Adjacent chains were linked
3.5. X-ray structure of 2-methylquinoline: (trimesic acid) (4)
Cocrystallization of 2-methylquinoline and trimesic acid in a
1:1 ratio from methanol gave single crystals suitable for X-ray
together along the c axis direction by C(carbonyl)–
p interaction

S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
23
Fig. 6. 2D double layer sheet structure of 3.
diffraction. Structure determination (Table 1) revealed that
2-methylquinoline and trimesic acid are present in a 1:1 ratio in
the molecular complex 4, and the asymmetric unit is shown in
Fig. 7. Unlike the salts 1–3, no protons from the trimesic acid have
been deprotonated and transferred to the ring N atoms of the
2-methylquinoline. Thus 3 is a cocrystal instead of a salt, it is
the same as the adduct of trimesic acid tris(pyridine) solvate [38].
The OAC bond distances of the carboxyl group were ranging
from 1.202(3) to 1.305(3). The pair of OAC bond distances in the
four carboxyl groups concerning the C(21), C(22), C(30), and
C(31) atoms are almost equal to each other, suggesting that there
of both rings. The rms deviation of the ring with the N2 atom is
0.0044 Å, the dihedral angles between this ring and the above
two benzene rings of the trimesic acids are 3.1°, and 2.3° respec-
tively. The rms deviation of the ring with the N1 atom is
0.0038 Å, the dihedral angle between the two quinoline rings is
2.7°. The quinoline ring with the N1 atom makes dihedral angles
of 5°, and 3.8° with the above two aromatic rings of the trimesic
acid moieties respectively.
Every 2-methylquinoline is bonded to one trimesic acid through
one neutral OAHÁ Á ÁN (between the OH group of one COOH and the
ring
N atom of 2-methylquinoline with NAO distance of
are strong p–
p
conjugated effect between the O atom of the OH
2.602(3) Å), one CH3AO (between the 2-CH3 of the 2-methylquin-
oline molecule and the OH group with CAO distance of 3.105 Å),
and one CHAO (between 8-CH of the 2-methylquinoline and the
C@O group with CAO distance of 3.496 Å) associations to form a
bicomponent heteroadduct. In the heteroadduct there are R22(8)
and R22(6) ring motifs according to Bernstein et al. [33], and this
two kinds of ring motifs were fused together by the neutral
OAHÁ Á ÁN hydrogen bond. The adjacent heteroadducts were con-
nected together via two CHAO associations to form a 1D chain run-
ning along the direction that formed an angle of ca. 60° with the bc
plane. Of the two CHAO associations, one is between the 5-CH of
unit and the carbonyl group. The CANAC angles at the neutral
2-methylquinoline are 119.7(3)°, and 120.1(3)° respectively. Com-
pared with the above protonated 2-methylquinoline, these angles
are significantly smaller than the corresponding angles in the
above salts 1–3, which also confirms our correct assignment of 4
as a cocrystal.
The rms deviation of the ring containing atoms
C30AC38AO7AO12 is 0.0205 Å, the rms deviation of the ring bear-
ing the atoms C21AC29AO1AO6 is 0.0434 Å, the dihedral angle
between the two rings is 1.2° indicating the parallel arrangement
Fig. 7. The structure of 4, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.

24
S. Jin et al. / Journal of Molecular Structure 1010 (2012) 17–25
Fig. 8. 2D sheet structure of 4.
the 2-methylquinoline and the C@O group of the second COOH
group with CAO distance of 3.594 Å and the other is between
6-CH of the 2-methylquinoline and the C@O group of the third
COOH group with CAO distance of 3.622 Å. In the same chain the
heteroadducts formed between 2-methylquinoline and trimesic
acid were parallel to each other, while the heteroadducts at the
neighboring chains were antiparallel to each other. The corre-
sponding heteroadducts at the third chain have the same projects
as the heteroadducts at the first chain when viewed from the c axis
direction, so do the heteroadducts at the second chain and the
heteroadducts at the fourth chain. Adjacent such chains were
joined together through the homomeric carboxylic acid-carboxylic
acid R22(8) synthon (cyclic hydrogen bonded carboxylic acid ring
motif R22(8)). And there are also CHAO interactions between the
3-CH of 2-methylquinoline in one chain and the C@O of the COOH
unit of its adjacent chain with CAO distance of 3.448 Å, in this case
the OH group in this COOH unit is involved in OAHÁ Á ÁN interaction.
Under these interactions the complex 4 displays a 2D sheet struc-
ture extending along the direction that formed an angle of ca. 60°
with the bc plane, which is shown in Fig. 8. Such 2D sheets were
The results presented herein indicate that the strength and
directionality of the N+AHÁ Á ÁOÀ, OAHÁ Á ÁO, and OAHÁ Á ÁN hydrogen
bonds (ionic or neutral) between acidic units and 2-methylquino-
line are sufficient to bring about the formation of binary organic
salts or cocrystals.
5. Supporting information
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic data center, CCDC
Nos. 765311 for 1, 809893 for 2, 809677 for 3, and 792910 for 4.
Copies of this information may be obtained free of charge from
the +44(1223)336-033 or Email: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk.
Acknowledgements
We gratefully acknowledge the financial support of the
Education Office Foundation of Zhejiang Province (Project No.
Y201017321) and the financial support of the Zhejiang A & F Uni-
versity Science Foundation (Project No. 2009FK63).
further stacked along the a axis direction through p–p interactions
between the trimesic acids with centroid–centroid separation of
3.348 Å to form a double sheet structure. Here the aromatic rings
of the 2-methylquinoline units are not involved in this kind of
interactions.
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