Five binary supramolecular organic salts constructed from 2-aminoheterocyclic compounds and carboxylic acid derivatives through strong and weak non-covalent interactions

Article abstract of DOI:10.1016/j.molstruc.2011.01.006

Studies concentrating on hydrogen bonding between the base of 2-aminoheterocyclic compounds 5,7-dimethyl-1,8-naphthyridine-2-amine, 4-phenylthiazol-2-amine, and carboxylic acid derivatives have led to an increased understanding of the role 2-aminoheterocy

Full text of DOI:10.1016/j.molstruc.2011.01.006

Journal of Molecular Structure 991 (2011) 1–11
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Five binary supramolecular organic salts constructed from 2-aminoheterocyclic
compounds and carboxylic acid derivatives through strong and weak non-covalent
interactions
b
a
c
a
a
a
Shouwen Jin a, , Wenbiao Zhang , Li Liu , Daqi Wang , Haidong He , Tao Shi , Feng Lin
⇑
a Faculty of Science ZheJiang A&F University, Lin’An 311300, PR China
b School of Engineering ZheJiang A&F University, Lin’An 311300, PR China
c 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:
Studies concentrating on hydrogen bonding between the base of 2-aminoheterocyclic compounds 5,7-
dimethyl-1,8-naphthyridine-2-amine, 4-phenylthiazol-2-amine, and carboxylic acid derivatives have
led to an increased understanding of the role 2-aminoheterocyclic compounds have in binding with car-
boxylic acid derivatives. Here anhydrous and hydrous multicomponent adducts of 2-aminoheterocyclic
compounds such as 5,7-dimethyl-1,8-naphthyridine-2-amine, and 4-phenylthiazol-2-amine have been
prepared with 2-chloronicotinic acid, p-hydroxy benzoic acid, maleic acid, and phthalic acid. The five
crystalline forms reported are organic salts of which the crystals and complexes were characterized by
X-ray diffraction analysis, IR, mp, and elemental analysis. All supramolecular architectures of salts 1–5
are stabilized by NAHꢀꢀꢀO hydrogen bonds as well as other non-covalent interactions. These weak inter-
actions combined, all the complexes displayed 3D structure.
Received 28 October 2010
Received in revised form 6 January 2011
Accepted 7 January 2011
Available online 22 January 2011
Keywords:
Crystal structure
Organic salts
Non-covalent interactions
2-Aminoheterocyclic compounds
Carboxylic acids
Ó 2011 Elsevier B.V. All rights reserved.
3D framework
1. Introduction
structures such as one-dimensional (1-D) tapes, two-dimensional
(2-D) sheets, and three-dimensional (3-D) networks which have
The design and construction of multicomponent supermole-
cules or supramolecular arrays utilizing non-covalent bonding is
a rapidly developing area in supramolecular synthesis. Thus, the
supramolecular synthesis successfully exploits hydrogen bonding
and other types of non-covalent interactions, in building supramo-
lecular systems [1]. In this regard, there is great interest in co-crys-
tals/organic salts in recent years [2–5].
Currently, H-bonding interactions have been widely developed
in the area of crystal engineering, supramolecular chemistry, mate-
rial science, and biological recognition [6–9]. The application of
intermolecular hydrogen bonds is a well known and efficient tool
in the field of organic crystal design because of its strength and
directional properties [9]. Through hydrogen bonds cocrystals and
organic salts can be generated. In pharmaceuticals, cocrystal/salt
formation has also arouses great interest. This is primarily because
cocrystals/salts have the potential to alter and optimize physical
properties such as crystalline form, solubility, and stability of an ac-
tive pharmaceutical ingredient (API) without detrimentally affect-
ing its activity [10]. There are many interesting topological
been constructed through hydrogen bonding interactions [11,12].
The carboxylic acid bears the important hydrogen bonding func-
tional group COOH for crystal engineering [13]. Carboxylic acids
aggregate in the solid state as dimer, catemer, and bridged motifs
[14]. Besides the COOH group, the functional groups such as halo-
gen and phenol OH groups are both good groups in forming organic
solid through non-covalent interactions [15], thus we select some
carboxylic acids bearing additional groups such as chloro and phe-
nol OH. It is interesting to exploit the robust and directional recog-
nition of carboxylic acids with nitrogen containing heterocyclic
compounds [16].
Recently 2-aminoheterocyclic compounds have been reported to
form supramolecular compounds with the carboxylic acid deriva-
tives under the multiple hydrogen bonding action [17,18]. As the
2-aminoheterocyclic compounds 5,7-dimethyl-1,8-naphthyridine-
2-amine, and 4-phenylthiazol-2-amine both may act as potentially
tridentate ligands (NNN and NSN). The binary organic salts of the
carboxylic acids and 2-aminoheterocyclic compounds may display
the different hydrogen-bonding patterns from the three different
donor atoms. As an extension of our study of weak interactions
(hydrogen bonding, p–pinteraction, and halogen bonding) concern-
⇑
ing aromatic N-containing derivatives [19], herein we report the
preparation and structures of five organic salts assembled from
Corresponding author. Tel./fax: +86 571 6374 0010.
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.2011.01.006

2
S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
Cl
O
HO
OH
O
N
OH
O
HO
O HO
2-chloronicotinic acid
p-hydroxy benzoic acid
maleic acid
OH
O
N
H2N
HO
H2N
N
N
S
O
phthalic acid
5,7-dimethyl-1,8-naphthyridin-2-amine
4-phenylthiazol-2-amine
Scheme 1. Hydrogen bond synthons discussed in this paper.
H2N
N
N
H3N
N
N
H2N
N
N
H2N
N
H
N
O
O
Cl
N
OH
O
O
1
2
H
N
O
O
O
H
N
H2N
H2N
N
N
H
S
H2N
O
S
0.5
O
O
O HO
O
O
O HO
3
4
5
Scheme 2. The five organic salts described in this paper, 1–5.
5,7-dimethyl-1,8-naphthyridine-2-amine (L), 4-phenylthiazol-2-
amine (L1) and the corresponding carboxylic compounds (Scheme
1), respectively. The five organic salts are (5,7-dimethyl-1,8-naph-
thyridine-2-amine)2: (2-chloronicotinic acid) (1) [HL+ ꢀ L ꢀ (cnicꢁ),
cnic = 2-chloronicotinate], (5,7-dimethyl-1,8-naphthyridine-2-amine)2:
(p-hydroxy benzoic acid): 2H2O (2) [HL+ ꢀ L ꢀ (hbcꢁ) ꢀ 2H2O,
hbc = p-hydroxy benzoate], (5,7-dimethyl-1,8-naphthyridine-2-
amine): (maleic acid) (3) [HL+ ꢀ (Hmalꢁ), Hmal = hydrogen maleate],
(4-phenylthiazol-2-amine): (maleic acid) (4) [(HL1)+ ꢀ (Hmalꢁ)], and
phenylthiazol-2-amine were prepared by the method described
in the literature [20,21]. The FT-IR spectra were recorded from
KBr pellets in range 4000–400 cmꢁ1 on a Mattson Alpha-Centauri
spectrometer. Microanalytical (C, H, N, S) data were obtained with
a Perkin–Elmer Model 2400II elemental analyzer. Melting points of
new complexes were recorded on an XT-4 thermal apparatus with-
out correction.
2.2. Preparation of the organic salts 1–5
(4-phenylthiazol-2-amine): (phthalic acid)0.5 (5) [(HL1)+ ꢀ (op2ꢁ
)
0.5
,
op2ꢁ = phthalate] (Scheme 2).
2.2.1. (5,7-Dimethyl-1,8-naphthyridine-2-amine)2: (2-chloronicotinic
acid) [HL+ ꢀ L ꢀ (cnicꢁ)] (1)
2. Experimental
To an ethanolic solution (8 ml) of 5,7-dimethyl-1,8-naphthyri-
dine-2-amine (34.8 mg, 0.2 mmol) was added 2-chloronicotinic
acid (31.4 mg, 0.2 mmol). The solution was stirred for a few min-
utes, then the solution was filtered into a test tube. The solution
was left standing at room temperature for several days, colorless
crystals were isolated after slow evaporation of the ethanolic solu-
tion in air. The crystals were collected and dried in air to give the
2.1. Materials and physical measurements
The chemicals and solvents used in this work are of analytical
grade and available commercially and were used without further
purification. 5,7-Dimethyl-1,8-naphthyridine-2-amine and 4-

S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
3
title compound [HL+ ꢀ L ꢀ (cnicꢁ)] (1). Yield: 39 mg, 77.38% (based
on L). m.p. 189–191 °C. Anal. Calcd. for C26H26ClN7O2 (503.99): C,
61.91; H, 5.16; N, 19.44. Found: C, 61.87; H, 5.11; N, 19.38. Infrared
ꢀ (Hmalꢁ)] (3), yield 45 mg, 77.78%. m.p. 197–198 °C. Elemental
analysis performed on crystals exposed to the atmosphere: Calc.
for C14H15N3O4(289.29) C, 58.07; H, 5.18; N, 14.52. Found: C,
58.02; H, 5.09; N, 14.46. Infrared spectrum (KBr disc, cmꢁ1):
spectrum (KBr disc, cmꢁ1): 3306s(
mas(NH)), 3144s(ms(NH)), 3070s,
2980s, 2920s, 2380m, 2320m, 2080w, 1760w, 1668w, 1620m,
3530s(
2988m, 2837m, 2722m, 2390w, 2196m, 1988w, 1773w,
1719s( (COOH)), 1658w, 1602s(
as(COOꢁ)), 1588m, 1536m,
1476m, 1436m, 1378s(
s(COOꢁ)), 1350s, 1310m, 1269m, 1172m,
m(OH)), 3410s(multiple, mas(NH)), 3316s(ms(NH)), 3130m,
1580s(
1380s(
m
m
as(COOꢁ)), 1540m, 1500m, 1487m, 1448m, 1400m,
s(COOꢁ)), 1295m, 1240m, 1200m, 1160m, 1080m, 1000m,
m
m
930m, 850m, 744m, 700m, 646m, 606m, 540m, 480m, 440m.
m
1134m, 1072m, 1026m, 927m, 848m, 780m, 740m, 674m,
630mm, 567m, 452m.
2.2.2. (5,7-Dimethyl-1,8-naphthyridine-2-amine)2: (p-hydroxy
benzoic acid): 2H2O [HL+ ꢀ L ꢀ (hbcꢁ) ꢀ 2H2O] (2)
To a methanolic solution (5 ml) of 5,7-dimethyl-1,8-naphthyri-
dine-2-amine (34.8 mg, 0.2 mmol) was added p-hydroxy benzoic
acid (27.6 mg, 0.2 mmol). The solution was stirred for three min-
utes, then the solution was filtered into a test tube. The solution
was left standing at room temperature for several days, colorless
crystals were isolated after slow evaporation of the methanolic
solution in air. The crystals were dried in air to give the title com-
pound [HL+ ꢀ L ꢀ (hbcꢁ) ꢀ 2H2O]. Yield: 42 mg, 80.67% (Based on L).
m.p. 206–208 °C. Elemental analysis performed on crystals exposed
to the atmosphere: Calcd. for C27H32N6O5(520.59): C, 62.24; H,
6.15; N, 16.14; Found: C, 62.18; H, 6.10; N, 16.06. Infrared spectrum
2.2.4. (4-Phenylthiazol-2-amine): (maleic acid) [(HL1)+ ꢀ (Hmalꢁ)] (4)
4-Phenylthiazol-2-amine (35.2 mg, 0.2 mmol) was dissolved in
5 mL of ethanol. To this solution was added maleic acid (23.2 mg,
0.2 mmol) in 5 mL ethanol. Colorless prisms were afforded after
several weeks of slow evaporation of the solvent. The crystals were
dried in air to give the title compound [(HL1)+ ꢀ (Hmalꢁ)] (4), yield
42 mg, 71.84%. m.p. 212–214 °C. Elemental analysis performed on
crystals exposed to the atmosphere: Calc. for
C13H12N2O4S
(292.31): C, 53.37; H, 4.10; N, 9.58; S, 10.95. Found: C, 53.29; H,
4.01; N, 9.56; S, 10.88. Infrared spectrum (KBr disc, cmꢁ1):
3456s(multiple,
2842m, 2718m, 2468w, 2374m, 2213m, 1976w, 1836w, 1783w,
1713s( (COOH)), 1662w, 1606s(
as(COOꢁ)), 1596m, 1530m,
1486w, 1374s(
s(COOꢁ)), 1333m, 1250m, 1195m, 1131m,
mas(NH)), 3323s(ms(NH)), 3112m, 3064m, 2960m,
(KBr disc, cmꢁ1): 3560s(
3320s( s(NH)), 3140m, 3060m, 2990m, 2920m, 2812m, 2720m,
2360m, 2190m, 1960w, 1840w, 1775w, 1730m, 1670w, 1628m,
1598s(
as(COOꢁ)), 1542m, 1488s, 1426s, 1382s( s(COOꢁ)), 1358m,
m(OH)), 3440s(multiple,
mas(NH)),
m
m
m
m
m
m
1079m, 952m, 903m, 853m, 806m, 757m, 726m, 680m, 637m,
1300m, 1240m, 1196m, 1130m, 1100m, 1060m, 1020m, 936m,
853m, 800m, 738m, 680m, 620m, 580m, 542m, 510m, 470m,
443m.
558m, 470m.
2.2.5. (4-Phenylthiazol-2-amine): (phthalic acid)0.5 [(HL1)+ ꢀ (op2ꢁ
) ]
0.5
(5)
2.2.3. (5,7-Dimethyl-1,8-naphthyridine-2-amine): (maleic acid) [(HL)+
ꢀ (Hmalꢁ)] (3)
4-Phenylthiazol-2-amine (35.2 mg, 0.2 mmol) was dissolved in
5 mL of ethanol. To this solution was added phthalic acid (34 mg,
0.2 mmol) in 5 mL ethanol. Colorless prisms were afforded after
several weeks of slow evaporation of the solvent. The crystals were
5,7-Dimethyl-1,8-naphthyridine-2-amine (34.8 mg, 0.2 mmol)
was dissolved in 5 mL of ethanol. To this solution was added maleic
acid (23.2 mg, 0.2 mmol) in 3 mL ethanol. Colorless prisms were
afforded after 1 week of slow evaporation of the solvent. The crys-
tals were collected and dried in air to give the title compound [HL+
dried in air to give the title compound [H(L1)+ ꢀ (op2ꢁ
)0.5] (5),
yield 42 mg, 80.98%. m.p. 240–241 °C. Elemental analysis
performed on crystals exposed to the atmosphere: Calc. for
Table 1
Summary of X-ray crystallographic data for complexes 1, 2, 3, 4, and 5.
1
2
3
4
5
Formula
Fw
C
26H26ClN7O2
C27H32N6O5
520.59
C14H15N3O4
289.29
C13H12N2O4S
292.31
C13H11N2O2S
259.30
503.99
T, K
298(2)
298(2)
298(2)
298(2)
298(2)
Wavelength, Å
Crystal system
Space group
a, Å
b, Å
c, Å
0.71073
Monoclinic
P2(1)
7.4939(8)
22.9214(19)
7.7690(9)
90
114.214(2)
90
1217.1(2)
2
1.375
0.196
528
0.18 ꢂ 0.16 ꢂ 0.10
1.78–25.01
ꢁ8 ꢃ h ꢃ 8
ꢁ27 ꢃ k ꢃ 17
ꢁ9 ꢃ l ꢃ 9
6459
0.71073
Triclinic
P-1
8.597(2)
12.554(3)
12.762(3)
96.008(2)
107.332(2)
91.396(2)
1305.4(5)
2
1.324
0.094
552
0.42 ꢂ 0.39 ꢂ 0.17
1.68–25.01
ꢁ9 ꢃ h ꢃ 10
ꢁ14 ꢃ k ꢃ 14
ꢁ15 ꢃ l ꢃ 9
6424
0.71073
Monoclinic
C2/c
17.1529(16)
7.3086(8)
23.442(2)
90
104.722(2)
90
2842.3(5)
8
1.352
0.101
1216
0.42 ꢂ 0.39 ꢂ 0.20
2.46–25.01
ꢁ12 ꢃ h ꢃ 20
ꢁ8 ꢃ k ꢃ 8
ꢁ27 ꢃ l ꢃ 27
7063
0.71073
Orthorhombic
Pbca
12.7241(14)
7.3388(6)
29.109(2)
90
90
90
2718.2(4)
8
1.429
0.71073
Tetragonal
P4(3)2(1)2
9.3377(11)
9.3377(11)
27.079(2)
90
90
90
2361.1(4)
8
1.459
a
, °
b, °
c
, °
V, Å3
Z
Dcalcd, Mg/m3
Absorption coefficient, mmꢁ1
F(0 0 0)
0.253
1216
0.269
1080
Crystal size, mm3
h range, °
0.42 ꢂ 0.39 ꢂ 0.38
2.13–25.02
ꢁ15 ꢃ h ꢃ 14
ꢁ4 ꢃ k ꢃ 8
ꢁ34 ꢃ l ꢃ 34
10,403
0.49 ꢂ 0.45 ꢂ 0.29
2.31–25.01
ꢁ11 ꢃ h ꢃ 11
ꢁ7 ꢃ k ꢃ 11
ꢁ32 ꢃ l ꢃ 21
10,117
Limiting indices
Reflections collected
Reflections independent (Rint
)
3071 (0.0794)
0.946
4353 (0.2638)
0.815
2502 (0.0583)
1.032
2398 (0.0477)
1.026
2079 (0.0377)
1.058
Goodness-of-fit on F2
R indices [I > 2
r
I]
0.0583, 0.1474
0.1095, 0.1756
0.172, ꢁ0.198
0.0948, 0.1631
0.2543, 0.2266
0.282, ꢁ0.294
0.0552, 0.1356
0.1279, 0.1769
0.223, ꢁ0.194
0.0403, 0.0895
0.0808, 0.1137
0.183, ꢁ0.204
0.0344, 0.0772
0.0480, 0.0859
0.166, ꢁ0.198
R indices (all data)
Largest diff. peak and hole, e Åꢁ3

4
S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
C13H11N2O2S(259.30): C, 60.16; H, 4.24; N, 10.79; S, 12.34. Found:
C, 60.06; H, 4.12; N, 10.71; S, 12.32. Infrared spectrum (KBr disc,
were performed using the SMART and SAINT software [22]. The
structures were solved by direct methods, and the non-hydrogen
atoms were subjected to anisotropic refinement by full-matrix
least squares on F2 using SHELXTL package [23].
Hydrogen atom positions for all of the structures were located
in a difference map and refined independently. Further details of
the structural analysis are summarized in Table 1. Selected bond
lengths and angles for the salts 1, 2, 3, 4, and 5 are listed in Table
2, the relevant hydrogen bond parameters are provided in Table 3.
cmꢁ1): 3454s(multiple,
m
as(NH)), 3332s(
2979m, 2926m, 2842m, 2724m, 2580w, 2356m, 2179m, 1998w,
1812w, 1769w, 1721m, 1676w, 1638m, 1586m, 1551s(
as(COOꢁ)),
1470m, 1426m, 1368s(
s(COOꢁ)), 1304m, 1232m, 1196m, 1126m,
ms(NH)), 3140m, 3032m,
m
m
1073m, 1020m, 930m, 888m, 802m, 716m, 656m, 614m, 574m,
510m, 464m.
2.3. X-ray crystallography and data collection
3. Results and discussion
Suitable crystals were mounted on a glass fiber on a Bruker
SMART 1000 CCD diffractometer operating at 50 kV and 40 mA
3.1. Preparation and general characterization
using Mo Ka radiation (0.71073 Å). Data collection and reduction
5,7-Dimethyl-1,8-naphthyridine-2-amine and 4-phenylthiazol-
2-amine both have good solubility in common organic solvents,
such as CH3COCH3, CH3OH, C2H5OH, CH2Cl2, CHCl3, and CH3CN.
The crystals were grown by slow evaporation of the corresponding
polar hydroalcoholic solution at room temperature.
The preparation of compounds 1–5 were carried out with
2-aminoheterocyclic compounds and the corresponding carboxylic
acid derivatives in 1:1 ratio. In all of the structures the base mole-
cules are protonated therefore the structures can be classified as
salts. The five salts are not hygroscopic, and they all crystallized
with no solvent molecules accompanied except salt 2. The molec-
Table 2
Selected bond lengths (Å) and angles (°) for compounds 1, 2, 3, 4, and 5.
1
Cl(1)AC(2)
N(1)AC(6)
N(2)AC(11)
N(3)AC(11)
N(5)AC(21)
N(6)AC(21)
N(7)AC(17)
O(2)AC(1)
C(2)AN(1)AC(6)
C(12)AN(3)AC(11)
C(21)AN(6)AC(22)
O(1)AC(1)AO(2)
1.725(4)
1.334(6)
1.387(14)
1.352(16)
1.357(14)
1.337(15)
1.353(17)
1.293(18)
116.0(4)
N(1)AC(2)
N(2)AC(7)
N(3)AC(12)
N(4)AC(7)
N(5)AC(17)
N(6)AC(22)
O(1)AC(1)
O(20)AC(1)
C(7)AN(2)AC(11)
C(21)AN(5)AC(17)
O(1)AC(1)AO(20)
O(20)AC(1)AO(2)
1.330(5)
1.314(16)
1.322(16)
1.271(16)
1.371(16)
1.348(15)
1.176(16)
1.199(17)
121.1(10)
120.0(10)
113.9(11)
50.3(10)
114.4(10)
120.4(10)
125.1(5)
Table 3
2
Hydrogen bond distances and angles in studied structures of 1, 2, 3, 4, and 5.
N(1)AC(8)
N(2)AC(9)
N(3)AC(9)
N(4)AC(18)
N(5)AC(18)
O(1)AC(1)
O(3)AC(5)
C(2)AC(7)
1.334(7)
1.330(7)
1.327(7)
1.372(7)
1.361(7)
1.255(7)
1.356(6)
1.379(8)
1.382(7)
117.8(5)
118.5(5)
122.6(6)
117.8(6)
123.4(6)
121.3(6)
122.7(6)
114.6(5)
114.0(5)
N(1)AC(15)
N(2)AC(8)
N(4)AC(25)
N(5)AC(19)
N(6)AC(19)
O(2)AC(1)
C(1)AC(2)
C(2)AC(3)
1.341(7)
1.411(7)
1.332(7)
1.330(7)
1.340(7)
1.275(8)
1.493(8)
1.393(8)
1.381(8)
121.1(5)
117.3(5)
119.6(7)
116.8(6)
119.8(6)
118.4(7)
118.9(6)
119.1(5)
118.5(5)
DAHꢀꢀꢀA
d(DAH) (Å) d(HꢀꢀꢀA) (Å) d(DꢀꢀꢀA) (Å) <(DHA) (°)
1
N(7)AH(7B)ꢀꢀꢀO(1)#1
N(7)AH(7A)ꢀꢀꢀN(3)
N(4)AH(4B)ꢀꢀꢀO(2)#2
0.86
0.86
0.86
1.89
1.98
2.03
1.93
2.06
2.11
2.722(16)
2.838(13)
2.878(17)
2.757(19)
2.915(14)
2.971(5)
164.0
172.4
167.9
159.9
174.2
176.6
N(4)AH(4B)ꢀꢀꢀO(20)#2 0.86
N(4)AH(4A)ꢀꢀꢀN(6)
N(2)AH(2)ꢀꢀꢀN(5)
0.86
0.86
C(3)AC(4)
C(4)AC(5)
C(8)AN(1)AC(15)
C(25)AN(4)AC(18)
O(1)AC(1)AO(2)
O(2)AC(1)AC(2)
C(7)AC(2)AC(1)
C(4)AC(3)AC(2)
O(3)AC(5)AC(6)
N(1)AC(8)AN(2)
N(5)AC(18)AN(4)
C(9)AN(2)AC(8)
C(19)AN(5)AC(18)
O(1)AC(1)AC(2)
C(7)AC(2)AC(3)
C(3)AC(2)AC(1)
O(3)AC(5)AC(4)
C(4)AC(5)AC(6)
N(3)AC(9)AN(2)
N(5)AC(19)AN(6)
2
O(5)AH(31)ꢀꢀꢀO(1)#1
O(5)AH(30)ꢀꢀꢀO(1)#2
O(4)AH(29)ꢀꢀꢀO(5)#3
O(4)AH(28)ꢀꢀꢀO(2)#4
O(3)AH(3)ꢀꢀꢀO(4)
0.85
0.85
0.85
0.85
0.82
0.89
0.89
0.86
0.86
1.97
1.82
1.91
1.90
1.83
2.41
2.10
1.95
2.02
2.813(6)
2.671(6)
2.728(6)
2.712(6)
2.645(6)
2.894(7)
2.961(6)
2.799(7)
2.868(6)
168.7
176.1
162.0
159.6
170.1
114.8
164.0
170.1
168.1
N(6)AH(6C)ꢀꢀꢀO(5)#5
N(6)AH(6A)ꢀꢀꢀN(1)#6
N(3)AH(3B)ꢀꢀꢀO(2)#7
N(3)AH(3A)ꢀꢀꢀN(4)#8
3
N(1)AC(5)
N(2)AC(10)
N(3)AC(5)
O(2)AC(1)
O(4)AC(4)
C(10)AN(2)AC(9)
O(4)AC(4)AO(3)
N(1)AC(9)AN(2)
1.333(4)
1.341(4)
1.320(4)
1.241(4)
1.206(4)
123.5(3)
121.4(4)
115.8(3)
N(1)AC(9)
N(2)AC(9)
O(1)AC(1)
O(3)AC(4)
C(5)AN(1)AC(9)
O(2)AC(1)AO(1)
N(3)AC(5)AN(1)
1.339(4)
1.369(4)
1.268(4)
1.281(5)
117.1(3)
123.4(3)
118.7(3)
3
O(3)AH(3)ꢀꢀꢀO(1)
N(3)AH(3B)ꢀꢀꢀO(1)
N(3)AH(3A)ꢀꢀꢀO(4)#1
N(2)AH(2)ꢀꢀꢀO(2)#2
0.82
0.86
0.86
0.86
1.62
2.01
2.15
1.92
2.437(3)
2.859(4)
2.936(4)
2.766(3)
177.8
168.3
152.6
168.5
4
O(2)AH(2)ꢀꢀꢀO(3)
N(2)AH(2B)ꢀꢀꢀO(1)#1
N(2)AH(2B)ꢀꢀꢀO(2)#1
N(2)AH(2A)ꢀꢀꢀO(3)#2
N(1)AH(1)ꢀꢀꢀO(4)#2
0.82
0.86
0.86
0.86
0.86
1.61
2.40
2.17
1.96
1.89
2.429(3)
3.181(3)
2.956(3)
2.815(3)
2.742(3)
179.0
151.8
151.2
174.1
172.9
4
N(1)AC(1)
N(2)AC(1)
1.333(3)
1.310(3)
1.295(3)
1.238(3)
1.720(3)
89.68(14)
125.0(2)
120.1(3)
N(1)AC(2)
O(1)AC(10)
O(3)AC(13)
S(1)AC(1)
C(1)AN(1)AC(2)
N(2)AC(1)AN(1)
N(1)AC(1)AS(1)
O(4)AC(13)AO(3)
1.389(3)
1.214(3)
1.273(3)
1.719(3)
114.8(2)
123.7(3)
111.2(2)
123.7(3)
O(2)AC(10)
O(4)AC(13)
S(1)AC(3)
C(1)AS(1)AC(3)
N(2)AC(1)AS(1)
O(1)AC(10)AO(2)
5
N(2)AH(2B)ꢀꢀꢀO(2)#2
N(2)AH(2A)ꢀꢀꢀO(2)#1
N(1)AH(1)ꢀꢀꢀO(1)#1
0.86
0.86
0.86
2.01
2.07
1.81
2.810(3)
2.828(3)
2.654(2)
154.8
147.1
167.6
Symmetry transformations used to generate equivalent atoms for 1: #1 ꢁx + 1,
y + 1/2, ꢁz; #2 x, y, z + 1. Symmetry transformations used to generate equivalent
atoms for 2: #1 ꢁx + 1, ꢁy + 1, ꢁz + 1; #2 x, y ꢁ 1, z + 1; #3 x, y, z ꢁ 1; #4 ꢁx, ꢁy + 1,
ꢁz; #5 x + 1, y, z; #6 x + 1, y ꢁ 1, z; #7 ꢁx, ꢁy + 2, ꢁz; #8 x ꢁ 1, y + 1, z. Symmetry
transformations used to generate equivalent atoms for 3: #1 ꢁx + 1, y, ꢁz + 3/2; #2
x + 1/2, y ꢁ 1/2, z. Symmetry transformations used to generate equivalent atoms for
4: #1 x ꢁ 1/2, ꢁy + 3/2, ꢁz + 1; #2 x ꢁ 1, y + 1, z. Symmetry transformations used to
generate equivalent atoms for 5: #1 y, x, ꢁz + 2; #2 y ꢁ 1/2, ꢁx + 3/2, z + 1/4.
5
N(1)AC(1)
O(1)AC(10)
S(1)AC(1)
N(2)AC(1)
C(1)AS(1)AC(3)
N(2)AC(1)AS(1)
1.329(3)
1.252(3)
1.723(3)
1.313(3)
89.82(12)
123.97(19)
N(1)AC(2)
O(2)AC(10)
S(1)AC(3)
C(1)AN(1)AC(2)
N(2)AC(1)AN(1)
N(1)AC(1)AS(1)
1.395(3)
1.256(3)
1.724(3)
114.6(2)
124.6(2)
111.46(19)

S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
5
Fig. 1. Molecular structure of 1 showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
ular structures and their atom labelling schemes for the five struc-
tures are illustrated in Figs. 1, 3, 5, 7 and 9, respectively. In the
preparation of the organic salts 1, 2, 3, 4, and 5 the carboxylic acids
were mixed directly with the base in the corresponding solution,
which was allowed to evaporate at ambient conditions to give
the final crystalline products. The elemental analysis data for the
five compounds are in good agreement with their compositions.
The infrared spectra of the five compounds are consistent with
their chemical formulas determined by elemental analysis and fur-
ther confirmed by X-ray diffraction analysis. H atoms connected to
O or N atoms were well found from the difference electron density
map, which also indirectly confirms the proton transfer.
another carboxylic acid group remains protonized, thus 3 and 4
form 1:1 salts. In 5, both protons of the phthalic acid have trans-
ferred to two 4-phenylthiazol-2-amine molecules to form 1:2 ad-
duct, thus the acid in 5 presents a valence number of ꢁ2.
The very strong and broad features at approximately 3600–
3100 cmꢁ1 in the IR spectra of the five compounds arise from
OAH or NAH stretching frequencies. Aromatic, naphthyridic, and
phenylthiazolic ring stretching and bending are attributed to the
medium intensity bands in the regions of 1500–1630 cmꢁ1 and
600–750 cmꢁ1, respectively. All of the five salts show the charac-
teristic bands for COOꢁ, and compounds 3, and 4 display strong
IR peaks for COOH groups. IR spectroscopy has also proven to be
useful for the recognition of proton transfer compounds [24]. The
most distinct feature in the IR spectrum of proton transfer com-
pounds are the presence of strong asymmetrical and symmetrical
In 1 and 2, the protons of each monoacids have transferred to
the 5,7-dimethyl-1,8-naphthyridine-2-amine molecules. In 3 and
4, one proton of the maleic acid has transferred to the base, while
Fig. 2. 2D sheet structure of 1 which is viewed along the a axis.

6
S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
carboxylate stretching frequencies at 1550–1610 cmꢁ1 and 1300–
As expected, the naphthyridine rings are planar (the r.m.s devi-
ations of the naphthyridine ring atoms from the mean plane of the
ring are 0.0176 and 0.0153 Å within the HL+ cation and L molecule
respectively). And the dihedral angle between the two naphthyri-
dine rings in the same dimer is 0.9°, indicating that they are
roughly coplanar. The r.m.s deviation of the pyridine ring atoms
of the anion in 1 from the mean plane of the ring is 0.0103 Å. While
the dihedral angles between the anion and the pair of naphthyri-
dine rings of the naphthyridine dimer are both 112.6°.
1420 cmꢁ1 in compounds 1, 2, 3, 4, and 5, respectively [25].
4. Structural descriptions
4.1. X-ray structure of (5,7-dimethyl-1,8-naphthyridine-2-amine)2:
(2-chloronicotinic acid) [HL+ ꢀ L ꢀ (cnicꢁ)] (1)
The anions formed 1D chain structure along the c axis direction
through CAHꢀꢀꢀCl hydrogen bonds with the CACl distance of
3.654 Å which is in the upper limit of the reported CAHꢀꢀꢀCl bonds
[26]. The cationic naphthyridine dimers were suspended between
the two chains through NAHꢀꢀꢀO (between the amine group of
the naphthyridine dimer and the O atom of 2-chloronicotinate
chains with NAO distance in the range of 2.722–2.877 Å) and
CH3AO (between 5-CH3 of the naphthyridine dimer and the car-
boxylate O with the CAO distance of 3.387, and 3.150 Å) hydrogen
bonds to form one-dimensional grid structure. The grids extended
in the bc plane to form 2D sheet which is shown in Fig. 2. And the
2D sheets were further stacked along the a axis direction through
The compound 1 of the composition [HL+ ꢀ L ꢀ (cnic)ꢁ] was pre-
pared by reaction equal mol of 5,7-dimethyl-1,8-naphthyridine-2-
amine and 2-chloronicotinic acid, in which the proton of 2-chlo-
ronicotinic acid was transferred to the N atom adjacent to the
NH2 group on the naphthyridine ring. This structure is not a sol-
vate. In the asymmetric unit of 1 there existed one molecule of
5,7-dimethyl-1,8-naphthyridine-2-amine, one cation of 5,7-di-
methyl-1,8-naphthyridinium-2-amine, and an anion of 2-chloro-
nicotinate, as shown in Fig. 1. The oxygen atom O(2) was
disordered over two positions both with occupancies of 0.5.
The CAO distances of COOꢁ of the 2-chloronicotinate are rang-
ing from 1.176(16) to 1.293(18) Å. The significant difference (
D is
CH3–p interaction to form 3D layer network structure.
0.117 Å) in bond distances between O(1)AC(1) (1.176(16) Å) and
O(2)AC(1) (1.293(18) Å) in the carboxylate group in compound 1
is caused by the fact that O(2) is involved in forming more strong
hydrogen bonds than that of O(1).
The NAHꢀꢀꢀO hydrogen bond is formed between the oxygen
atom of the carboxylate and the amine group (N(7)AH(7B)ꢀꢀꢀ
O(1)#1, 2.722(16) Å; N(4)AH(4B)ꢀꢀꢀO(2)#2, 2.878(17) Å;
N(4)AH(4B)ꢀꢀꢀO(20)#2, 2.757(19) Å), there does not exist ionic
N+AHꢀꢀꢀOꢁ hydrogen bonds.
4.2. X-ray structure of (5,7-dimethyl-1,8-naphthyridine-2-amine)2:
(p-hydroxy benzoic acid): 2H2O [HL+ ꢀ L ꢀ (hbcꢁ) ꢀ 2H2O] (2)
The compound 2 was also prepared by reaction of 5,7-dimethyl-
1,8-naphthyridine-2-amine with p-hydroxybenzoic acid in 1:1 ra-
tio, which crystallizes as triclinic block crystals in the centrosym-
metric space group P-1.
Two naphthyridines formed dimers through intermolecular
hydrogen bonding (NAHꢀꢀꢀN) interaction of the type DDA–AAD (D
represents the donor group NH, and A represents the acceptor
group N respectively) between HL+ and L. Two naphthyridinium di-
mers and two 2-chloronicotinate anions self-assembled via
NAHꢀꢀꢀO hydrogen bonds to form bis-2-chloronicotinate termi-
nated moiety, in which the two terminal 2-chloronicotinates exist
in trans conformation. When viewed along the a axis, the corre-
sponding 2-chloronicotinate ions in the adjacent bis-2-chloronico-
tinate terminated moieties are parallel to each other. Adjacent
naphthyridine dimers are extended along the c axis direction
The compound consists of one 5,7-dimethyl-1,8-naphthyridine-
2-amine molecule, one 5,7-dimethyl-1,8-naphthyridinium-2-
amine cation, one p-hydroxybenzoate anion, and two water mole-
cules (Fig. 3). The compound is also an organic salt. The present
investigation clearly shows that the positive charge (coming from
the carboxylate H of p-hydroxybenzoic acid) in the title compound
is on the amino group not on the ring nitrogen atom, forming an
ion pair, which is different from that of the compound 2-aminopy-
ridinium salicylate [27] and also different from compound 1. As
shown in Table 2, all the bond angles and bond distances are in
the normal range. The OAC bond distances of the carboxylate
group are 1.255(7), and 1.275(8) Å respectively. The difference be-
tween the two CAO bonds is 0.020 Å which is in the range of the
through CH3–p interaction in which the CACg distance is ca.
3.409 Å to exhibit 1D ladder structure.
Fig. 3. The structure of 2, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level. The water molecules were omitted.

S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
7
reported
D
value for organic salts formed between the carboxylic
p (between the 5-CH3 of the naphthyridine and the anion ring with
acid and the N-containing base [28], which is also expected for io-
nic CAO bond distances.
CACg distance of ca. 3.583 Å) and CH3AO interaction (between the
phenol OH of the anions and the 7-CH3 of the naphthyridine with
CAO distance of 3.329 Å) between the cation chain and the anion
sheet. The anionic sheet and the cationic chains were stacked alter-
natively along the c axis direction to form 3D ABAB layer structure,
as shown in Fig. 4.
The C19AN5 bond length is 1.330(7) Å, and is approximately
equal to a C@N double-bond length [29], indicating that atom N6
of the amino group must also be sp3 hybridized. This is also sup-
ported by the angles around C(19), (N(5)AC(19)AC(20),
123.5(6)°), and also verified by the bond angles concerning N(6)
i.e. C(19)AN(6)AH(6A), C(19)AN(6)AH(6B), H(6A)AN(6)AH(6B),
C(19)AN(6)AH(6C), H(6A)AN(6)AH(6C), and H(6B)AN(6)AH(6C)
are all 109.5°.
4.3. X-ray structure of (5,7-dimethyl-1,8-naphthyridine-2-amine):
(maleic acid) [HL+ ꢀ (Hmalꢁ)] (3)
The r.m.s deviation of the protonated naphthyridine ring atoms
from the mean plane of the ring is 0.0162 Å, the r.m.s deviation of
the neutral naphthyridine ring atoms from the mean plane of the
ring is 0.0169 Å. The dihedral angle between these two naphthyri-
dine rings is 3.6° indicating the coplanarity of both rings. The an-
ions are also planar with a r.m.s deviation of 0.017 Å. The anions
form dihedral angles of 104°, and 102° with the protonated L cation
and neutral L molecule respectively.
The asymmetric unit of 3 consists of one cation of 5,7-dimethyl-
1,8-naphthyridin-1-ium-2-amine, and an anion of hydrogen male-
ate, as shown in Fig. 5. In this case the less basic nitrogen atom
close to the methyl group is protonated which is similar to the
published result [31], but it is different from the compounds 1
and 2. There exist two NAHꢀꢀꢀO hydrogen bonds between the oxy-
gen atom of the carboxylate and the amine group (N(3)ꢀꢀꢀO(1),
2.859(4) Å, and N(3)ꢀꢀꢀO(4)#1, 2.936(4) Å), there also exists one
strong ionic N+AHꢀꢀꢀOꢁ hydrogen bond of N(2)AH(2)ꢀꢀꢀO(2)#2 with
the N(2)ꢀꢀꢀO(2)#2 distance of 2.766(3) Å. Unlike 1, and 2, there does
not exist NAHꢀꢀꢀN hydrogen bond so in 3 there are no naphthyri-
dine dimers. The singly deprotonated maleic acid has intramolecu-
lar hydrogen bonded structure through strong hydrogen bond
S11(7) O(3)AH(3)ꢀꢀꢀO(1) interaction, which is similar to the monoan-
ion of maleic acid in forming intramolecular hydrogen bonds [32].
The maleates were bonded to the naphthyridine core through
hydrogen bonds of NAHꢀꢀꢀO (between the amine protons of the
NH2 group and the carboxylate O atom with NAO distance of
2.859 Å) and CAHꢀꢀꢀO (between 3-CH of the naphthyridine ring
and the carboxylate O atom with CAO distance of 3.583 Å) to exhi-
bit a R22(8) ring motif which agrees well with the published results
of Bernstein [33].
In the compound, there is consistently a hydrogen bond
(N(3)AH(3B)ꢀꢀꢀO(2)#7, 2.799(7) Å, 170.1°) formed between the
amine group NH2 and the COꢁ anions, which is to be expected [30].
2
The two water molecules formed water dimers through
OAHꢀꢀꢀO (O(4)AH(29)ꢀꢀꢀO(5)#3, 2.728(6) Å) hydrogen bonds. The
water dimers connect the p-hydroxybenzoate anions in head to tail
fashion along the b axis direction to form a 1D chain structure. Two
adjacent chains were connected by two OAHꢀꢀꢀO hydrogen bonds
between the water molecules in one chain and the carboxylate
group in another chain to form 1D ladder structure. Adjacent lad-
ders were further connected through OAHꢀꢀꢀO hydrogen bonds (be-
tween the water molecules and the carboxylate group) along the a
axis direction to form 2D corrugated sheet structure. Two naph-
thyridines formed dimers through two NAHꢀꢀꢀN hydrogen bonds
of the type DA-AD between HL+ and L, adjacent dimers were con-
In the COOH group, two CAO bond lengths are obviously differ-
ent between O(3)AC(4) (1.281(5) Å) and O(4)AC(4) (1.206(4) Å)
nected by NAHꢀꢀꢀ
naphthyridine rings to form naphthyridine tetramers. The tetra-
mers were further connected by CH3– interaction (between the
p
interactions between the NHþ3 cations and the
with the
D value of 0.075 Å. The relatively larger D value which
p
is expected for neutral CAO and C@O bond distances [34] are also
confirming the reliability of adding H atoms experimentally by dif-
ferent electron density onto O atoms as mentioned above. But for
the COOꢁ group, two CAO bond lengths (The CAO distances of
COOꢁ of the hydrogen maleate are ranging from 1.241(4) to
1.268(4) Å) are basically not equal with an average value of
1.254 Å, which is shorter than that of the single bond of
O(3)AC(4) (1.281(5) Å) but longer than that of the double bond
7-CH3 of the naphthyridine of one tetramer and the naphthyridine
ring of the adjacent tetramer with the CACg distance of 3.839 Å) to
form one-dimensional cationic chain extending along the b axis
direction. Such chains were sandwiched between two anionic
sheets through NAHꢀꢀꢀO hydrogen bonds between the NHþ3 cation
and the O atom of carboxylate and the water molecules with
NAO distance in the range of 2.799–2.893 Å. There are also CH3–
Fig. 4. 3D ABAB layer structure of 2 viewed along the c axis direction.

8
S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
Fig. 5. The structure of 3, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
of O(4)AC(4) (1.206(4) Å) in the carboxylic group of hydrogen
maleate. This also supports our correct assignment of the hydrogen
maleate anion. It is clear that the difference in bond lengths of CAO
within the carboxylic acid group (0.075 Å) is larger than the one
found in the hydrogen maleate anion (0.027 Å), which also con-
firms the deprotonation of one carboxylic H.
The CAO distances of COOꢁ of the hydrogen maleate are rang-
ing from 1.238(3) to 1.273(3) is 0.035 Å). The angle
Å
(D
C3AS1AC1 (89.68(14)°) is larger than the corresponding angle in
the neutral molecule (88.7 (2)°) [35], yet it is smaller than that in
compound 2-amino-4-phenylthiazole hydrobromide monohydrate
(90.17°) [36]. This may be due to the difference of the hydrogen
bonding strength in the corresponding compound. The dihedral
angle between the planes of the phenyl and thiazole rings in the
same cation of 4 is 18.4 (3)°, which is also smaller than the value
(19.23°) in 2-amino-4-phenylthiazole hydrobromine monohy-
drate. But compound 4 is less planar than the neutral L1 in which
the dihedral angle between the phenyl ring and the thiazole ring is
(6.2(3)°). The planarity of 4 is further verified by the shorter
C(2)AC(4) bond distance [1.476(4) Å] in 4 compared with the value
of 1.506 Å found in 2-amino-4-phenylthiazole hydrobromine
monohydrate [35].
The carboxylate and the naphthyridine units connect alterna-
tively through NAHꢀꢀꢀO and CAHꢀꢀꢀN (between the olefinic CH of
the maleate and the ring N atom with CAN distance of 3.525 Å)
interactions along the direction that slipped by ca. 30° from the
bc plane to form one-dimensional chain structure. There are also
one-dimensional chain formed by the carboxylate and the naph-
thyridine which extended along the direction that forms angle of
ca. 30° with the ac plane. Such crossed chains were connected by
NAHꢀꢀꢀO and CAHꢀꢀꢀO bonds to form 3D network structure which
is shown in Fig. 6. There are also p–p and CH3–p interactions be-
tween adjacent parallel chains with the centroid separation and
CACg distance of 3.385 Å, and 3.564 Å respectively. Obviously,
the three-dimensional structure is stabilized by these weak
interactions.
Three NAHꢀꢀꢀO hydrogen bonds are formed between the oxygen
atom of the carboxylate and the amine group (N(2)ꢀꢀꢀO(1)#1,
3.181(3) Å, N(2)ꢀꢀꢀO(2)#1, 2.956(3) Å, and N(2)ꢀꢀꢀO(3)#2, 2.815(3)
Å). There is also one ionic N+AHꢀꢀꢀOꢁ hydrogen bond
(N(1)AH(1)ꢀꢀꢀO(4)#2) with the N(1)ꢀꢀꢀO(4)#2 distance of 2.742(3)
Å.
4.4. X-ray structure of (4-phenylthiazol-2-amine): (maleic acid)
[(HL1)+ ꢀ (Hmalꢁ)] (4)
In the COOH group, two CAO bond lengths are obviously differ-
ent between O(1)AC(10) (1.214(3) Å) and O(2)AC(10) (1.295(3) Å)
(
D is 0.081 Å) which are also confirming the reliability of adding H
Similar to compound 3, in 4 the asymmetric unit is occupied by
one monoanion of maleic acid and one cation of 4-phenylthiazol-1-
ium-2-amine (HL1)+ (Fig. 7). Here only one proton of the maleic
acid has transferred to the N atom of the thiazole ring. The same
as that in the compound 3, the monoanion of maleic acid also
forms intramolecular hydrogen bonded structure through strong
hydrogen bond S11(7) O(3)AH(3)ꢀꢀꢀO(2) interaction, which agrees
well with the reported results [32].
atoms experimentally by different electron density onto O atoms
as mentioned above. But for the COOꢁ group, two CAO bond
lengths are basically not equal with an average value of 1.255 Å,
which is shorter than that of the single bond of O(2)AC(10)
(1.295(3) Å) but longer than that of the double bond of
O(1)AC(10) (1.214(3) Å) in the maleic acid. This supports our
assignment of the maleate anion. It is clear that the
D value in
Fig. 6. 3D network structure of 3.

S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
9
Fig. 7. The structure of 4, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
bond lengths of CAO within the carboxylic acid group (0.081 Å) is
larger than the one found in the maleate anion (0.035 Å), which
also confirms the monoionization of the dicarboxylic acid.
One hydrogen maleate anion is bound to one 4-phenylthiazol-
4.5. X-ray structure of (4-phenylthiazol-2-amine): (phthalic acid)0.5
[(HL1)+ ꢀ (op2ꢁ
)0.5] (5)
The crystal structure of 5 consists of half a di-anion of phthalic
acid, and one cation of 4-phenylthiazol-1-ium-2-amine in the
asymmetric unit (Fig. 9). Both protons of the phthalic acid have
transferred to the ring N atom of two equivalent thiazole mole-
cules. The assignment of 5 as a salt is based on successful refine-
ment of the relevant H atoms using X-ray data. This is also
supported by equivalence of the CAO distances in the carboxylate
group, and a relatively low energy C@O stretch in the IR band. In
the compound, there is one ion pair without solvent molecules,
which is well agreement with the micro-analysis results.
1-ium-2-amine cation to form the adduct unit of [(HL1)+
ꢀ
(Hmalꢁ)]. In the adduct unit one hydrogen atom of the amine
group forms two neutral NAHꢀꢀꢀO hydrogen bonds with the oxygen
atom of COOH of the maleate in bifurcate mode. The adduct units
were connected by CAHꢀꢀꢀ
p hydrogen bond between olefinic CH of
the maleate and the phenyl ring of the (HL1)+ cation to form 1D
corrugated chain along the c axis direction. Adjacent corrugated
chains were further connected by NAHꢀꢀꢀO hydrogen bonds. There
are also two kinds of CAHꢀꢀꢀO interactions between the neighbor-
ing corrugated chains, one is between the phenyl CH of (HL1)+
and the carboxylate group of the maleate with CAO distance of
3.271 Å, the other is between the 4-CH on the thiazole ring and
the COOH of the anion with CAO distance of 3.163 Å. For the above
weak interactions every carboxylate of the maleate formed R22(7)
and R22(8) motifs with the 4-phenylthiazol-1-ium-2-amine cation,
in which the two kinds of hydrogen bonding motifs were fused to-
gether. Under these weak interactions the chains were connected
together to form two-dimensional corrugated sheet structure
along the ac plane which is shown in Fig. 8. The 2D sheets were fur-
ther stacked along the b axis direction to form 3D layer structure.
The CAO distances of COOꢁ of the phthalate are roughly equal
with each other (which are ranging from 1.252(3) to 1.256(3) Å),
indicating that the carboxylic groups are completely deprotonated.
And the ring N atom of 4-phenylthiazol-1-ium-2-amine is also
completely protonated. There are NAHꢀꢀꢀO hydrogen bonds arising
from the oxygen atom of the carboxylate and the amine group
(N(2)ꢀꢀꢀO(2)#2, 2.810(3) Å; N(2)ꢀꢀꢀO(2)#1, 2.828(3) Å). There is also
strong ionic N+AHꢀꢀꢀOꢁ hydrogen bond (N(1)AH(1)ꢀꢀꢀO(1)#1) with
0
N(1)ꢀꢀꢀO(1) distance of 2.654(2) ÅA, which is considerably less than
0
the sum of the van der Waals radii for N and O (3.07 ÅA) [37]. Thus
in the solid state, there is consistently ionic hydrogen bond formed
Fig. 8. 2D corrugated sheet structure of 4 viewed along the a axis.

10
S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
Fig. 9. The structure of 5, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
between the thiazole NH+ and the phthalate ion, which is to be ex-
pected [38]. In compound 5, there also exist strong electrostatic
interactions between charged cation units of NH+ and the di-anion
phthalates.
bonds. Every carboxylate O atom forms five hydrogen bonds in
which one oxygen atom forms two NAHꢀꢀꢀO hydrogen bonds
with the amine group of two L1 in bifurcate mode with NAO
0
distances ranged from 2.810 to 2.829 ÅA. While another O atom
The angle C3AS1AC1 (89.82(12)°) is similar to that in com-
pound 4 (89.68(14)°), and it is larger than the corresponding angle
in the neutral molecule (88.7 (2)°) [35]. But it is smaller than that
in compound 2-amino-4-phenylthiazole hydrobromide monohy-
drate (90.17°) [36]. This may be due to the difference of the hydro-
gen bonding strength also. The dihedral angle between the planes
of the phenyl and thiazole rings in 5 is 3.3 (3)°, so 5 is more planar
than both neutral L1(6.2(3)°) and ionic compounds such as com-
pound 4 (18.4 (3)°) and 2-amino-4-phenylthiazole hydrobromine
monohydrate (19.23°).
formed 0 two CAHꢀꢀꢀO hydrogen bonds (the CAO distances are
0
3.196 ÅA, and 3.306 ÅA respectively) and one ionic N+AHꢀꢀꢀOꢁ
0
hydrogen bond (with NAO distance of 2.654 ÅA) in trifurcate
fashion. For the above weak interactions every carboxylate of
the phthalate formed R22(7) and R22(8) motifs with the 4-phen-
ylthiazol-1-ium-2-amine cation. The same as the compound 4
the two kinds of hydrogen bonding motifs were also fused to-
gether. The r.m.s deviation of the ring atoms of the cation in 5
from the mean plane of the ring is 0.0291 Å, the phthalate
excluding the two carboxylate groups is also plane with the
r.m.s deviation of 0.1625 Å. The dihedral angle between the cat-
ion and the phthalate ring excluding the two carboxylate groups
is 161.6°. However the carboxylate [O(1)AC(10)AO(2)] deviates
by 48.5ꢀfrom the phenyl ring plane of the phthalate which is dif-
ferent from the reported adduct of phthalate in which the car-
boxylates are almost coplanar with the phenyl ring [41]. All of
the interactions combined, the compound displays 3D network
structure, as shown in Fig. 10.
In the whole structure there exist strong intermolecular S–
p
interactions between the S atom at the thiazole ring and the phenyl
0
ring of the cation with the closest S–C contact of ca. 3.414 ÅA, which
is similar to the previously published literature data [39]. But the
S–C contact is in the lower limit of the recently reported S–C con-
tact values [3.390–3.888 Å] [40].
Each phthalate is hydrogen bonded with six 4-phenylthiazol-
1-ium-2-amine cations through NAHꢀꢀꢀO and CAHꢀꢀꢀO hydrogen
Fig. 10. 3D network structure of organic salt 5 when viewed down the b axis.

S. Jin et al. / Journal of Molecular Structure 991 (2011) 1–11
11
5. Conclusions
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Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic data center, CCDC
Nos. 765440 for 1, 673181 for 2, 765438 for 3, 766264 for 4, and
765309 for 5. Copies of this information may be obtained free of
charge from the +44 (1223)336 033 or Email: deposit@ccdc.cam.a-
c.uk or www: http://www.ccdc.cam.ac.uk.
Acknowledgments
We gratefully acknowledge the financial support of the Educa-
tion Office Foundation of Zhejiang Province (Project No.
Y201017321) and the financial support of the Zhejiang A & F Uni-
versity Science Foundation (Project No. 2009FK63).