Structure of six anhydrous molecular salts assembled from noncovalent associations between carboxylic acids and bis-N-imidazoles

Article abstract of DOI:10.1016/j.molstruc.2012.04.082

Six crystalline organic acid-base adducts derived from bis(N-imidazolyl) and carboxylic acids (3,5-dinitrobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and phthalic acid) were prepared and characterized by X-ray diffraction analysis, IR,

Full text of DOI:10.1016/j.molstruc.2012.04.082

Journal of Molecular Structure 1022 (2012) 220–231
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structure of six anhydrous molecular salts assembled from noncovalent associations
between carboxylic acids and bis-N-imidazoles
b,
c
Shouwen Jin a, , Ming Guo , Daqi Wang
⇑
⇑
a Tianmu College of ZheJiang A & F University, Lin’An 311300, PR China
b Graduate School of ZheJiang A & F University, Lin’An 311300, PR China
c Department of Chemistry, Liaocheng University, Liaocheng 252059, PR China
h i g h l i g h t s
"
"
"
"
Six organic salts with 3D structure have been prepared and characterized.
The classical hydrogen bond between bis-imidazoles and acids have been discussed.
Other noncovalent associations are also discussed.
The classical hydrogen bond is the primary interaction in the structures built from OHꢀ ꢀ ꢀIm synthon.
a r t i c l e i n f o
a b s t r a c t
Article history:
Six crystalline organic acid–base adducts derived from bis(N-imidazolyl) and carboxylic acids (3,5-dini-
trobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and phthalic acid) were prepared and char-
acterized by X-ray diffraction analysis, IR, mp, and elemental analysis. The six compounds are all organic
salts. In salts 1, 2, 4, 5, and 6 the corresponding bis(imidazole) derivatives are diprotonated, while in 3,
the corresponding bis(imidazole) derivative is only monoprotonated.
Received 5 February 2012
Received in revised form 26 April 2012
Accepted 27 April 2012
Available online 9 May 2012
All supramolecular architectures of the salts 1–6 involve extensive NAHꢀ ꢀ ꢀO, OAHꢀ ꢀ ꢀO, CHꢀ ꢀ ꢀO, and
CH2ꢀ ꢀ ꢀO hydrogen bonds as well as other noncovalent interactions. The role of weak and strong nonco-
valent interactions in the crystal packing is ascertained. All the salts displayed 3D framework structures
under the cooperation of these weak interactions.
Keywords:
Crystal structure
3D framework
Hydrogen bonds
Carboxylic acid
Bis-imidazoles
The results presented herein indicate that the strength and directionality of the N+AHꢀ ꢀ ꢀOꢁ, OAHꢀ ꢀ ꢀO,
and NAHꢀ ꢀ ꢀN hydrogen bonds between carboxylic acids and ditopic imidazoles are sufficient to bring
about the formation of binary organic salts.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
Because of the predictable supramolecular properties and the
ability to form strong and directional hydrogen bonds, carboxylic
Multicomponent crystals and organic acid–base complexes have
received considerable attention over the past few years [1,2] not
only because of their intriguing structural motifs [3,4] but also for
their useful properties and promising applications as functional
materials [5,6]. The design and construction of multicomponent
supermolecules or supramolecular arrays utilizing noncovalent
bonding is a rapidly developing area in supramolecular synthesis.
Thus, the supramolecular synthesis successfully exploits hydro-
gen-bonding and other types of noncovalent interactions, in build-
ing supramolecular systems [7]. Of these interactions hydrogen
bond interactions are the most powerful organizing force for the
formation of supramolecules [8–11].
acids were frequently chosen as building blocks for crystal engi-
neering [12–14]. Numerous organic acid–base compounds from
carboxylic acids and a variety of N-containing basic building blocks
have been documented recently [15–19].
Imidazole and its derivatives are ubiquitous in biological and
biochemical structure and function, which attracted special
attention in the construction of some interesting metal–organic
frameworks in recent years [20–25]. And also, great efforts
have been devoted to the development of organic molecular crys-
tals containing
a variety of imidazole architectures [26–28].
Among these supramolecular architectures, however, only a very
few reports described the crystals composed of imidazoles [29–
33] (e.g., 1,4-bis[(imidazol-1-yl)methyl]-benzene [29,33], (bis(1-
methyl-imidazol-2-yl)methyl)-4-nitroimidazol-2-yl)methyl)amine
[31], etc.).
⇑
Corresponding authors. Tel./fax: +86 571 6374 6755.
E-mail addresses: Jinsw@zafu.edu.cn (S. Jin), guoming@zafu.edu.cn (M. Guo).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.04.082

S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
221
Following our previous works of acid–base adducts based on
bis(imidazole) and dicarboxylic acid [34,35], herein we report the
synthesis and crystal structure of six supramolecular compounds
assembled via hydrogen bonding interactions between carboxylic
acids and bis(imidazole). In this study, we got six organic com-
pounds composed of carboxylic acids and symmetric ditopic bis-
imidazol-1-yl compounds (Scheme 1), namely [(H2L12+)ꢀ(dnaꢁ)2]
(1) where L1 = 1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimid-
azole, dnaꢁ = 3,5-dinitrobenzoate, [(H2L2)2+ꢀ(5-nsaꢁ)2] (2) where
L2 = bis(N-imidazolyl)methane, 5-nsaꢁ = 5-nitrosalicylate, [(HL3)+ꢀ
(3,5-dnsꢁ)] (3) where L3 = 1,5-bis(1-benzimidazolyl)-3-oxapen-
tane, 3,5-dnsꢁ = 3,5-dinitrosalicylate, [(H2L2)2+ꢀ(3,5-dnsꢁ)2] (4),
[(H2L4)2+ꢀ(3,5-dnsꢁ)2] (5) where L4 = 1,4-bis(N-imidazolyl)butane,
and [(H2L2)2+ꢀ(Hptaꢁ)2] (6) where Hptaꢁ = hydrogen phthalate.
icylic acid (22.8 mg, 0.1 mmol) in 6 mL methanol. Colorless prisms
were afforded after several days of slow evaporation of the solvent,
yield: 35 mg, 65.48% based on L3. mp 191–192 °C. Elemental analy-
sis: Calc. for C25H22N6O8(534.49): C, 56.13; H, 4.11; N, 15.71. Found:
C, 56.06; H, 4.04; N, 15.63. Infrared spectrum (KBr disc, cmꢁ1): 3574s
(
m
(OH)), 3486s(multiple,
1996w, 1868w, 1783w, 1614 m, 1592s(
(NO2)), 1474w, 1406s(
s(COOꢁ)), 1358 m, 1314s(
m
as(NH)), 3338s(
m
s(NH)), 3054 m, 2972 m,
as(COOꢁ)), 1530s(mas
s(NO2)), 1240 m,
m
m
m
1120 m, 1013 m, 946 m, 868 m, 806 m, 757 m, 680 m, 638 m.
2.2.4. [(H2L2)2+ꢀ(3,5-dnsꢁ)2] (4)
Bis(N-imidazolyl)methane (15.0 mg, 0.1 mmol) was dissolved in
1 mL ethanol. To this solution was added 3,5-dinitrosalicylic acid
(22.8 mg, 0.1 mmol) in 6 mL methanol. Yellow prisms were afforded
after several days of slow evaporation of the solvent, yield: 35 mg,
57.91% (based on L2). mp 91–92 °C. Elemental analysis: Calc. for
2. Experimental section
C
21H16N8O14(604.42): C, 41.69; H, 2.65; N, 18.53. Found: C, 41.62;
H, 2.58; N, 18.48. Infrared spectrum (KBr disc, cmꢁ1): 3612s
(OH)), 3479s(multiple, as(NH)), 3356s( s(NH)), 3048 m, 2972
m, 1982w, 1884w, 1768w, 1697s( as(C@O)), 1624 m, 1525s
as(NO2)), 1486w, 1412 m, 1362 m, 1316s( s(NO2)), 1286s( s(CA
2.1. Materials and methods
(m
m
m
L1–L4 were prepared as described previously [36]. All other re-
agents were commercially available and used as received. The C, H,
and N micro-analysis were carried out with a Carlo Erba 1106 ele-
mental analyzer. The FT-IR spectra were recorded from KBr pellets
in range 4000–400 cmꢁ1 on a Mattson Alpha-Centauri spectrome-
ter. Melting points of new compounds were recorded on an XT-4
thermal apparatus without correction.
m
(m
m
m
O)), 1235 m, 1178 m, 1126 m, 1066 m, 992 m, 856 m, 802 m,
754 m, 688 m, 634 m, 605 m.
2.2.5. [(H2L4)2+ꢀ(3,5-dnsꢁ)2] (5)
1,4-Bis(N-imidazolyl)butane L4 (19.9 mg, 0.1 mmol) dissolved
in 2 mL of ethanol. To this solution was added 3,5-dinitrosalicylic
acid (22.8 mg, 0.1 mmol) in 6 mL methanol. Light yellow prisms
were afforded after several days of slow evaporation of the solvent,
yield: 36 mg, 55.68% (based on L4). mp 121–122 °C. Elemental anal-
ysis: Calc. for C24H22N8O14 (646.50): C, 44.55; H, 3.40; N, 17.32.
Found: C, 44.52; H, 3.32; N, 17.24. Infrared spectrum (KBr disc,
2.2. Preparation of the salts
2.2.1. [(H2L12+)ꢀ(dnaꢁ)2] (1)
1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazoleL1(27.6
mg, 0.1 mmol) was dissolved in 4 mL of methanol. To this solution
was added 3,5-dinitrobenzoic acid (21.2 mg, 0.1 mmol) in 4 mL
methanol. The solution was stirred for a few minutes, then the solu-
tion was filtered into a test tube. The solution was left standing at
room temperature for several days, light yellow block crystals were
isolated after slow evaporation of the solution in air. The crystals
were dried in air to give the title compound [(H2L12+)ꢀ(dnaꢁ)2] (1),
yield 36 mg, 51.38% (Based on L1). m. p. 186–187 °C. Elemental
analysis performed on crystals exposed to the atmosphere:
Calc. for C31H24N8O12 (700.58): C, 53.10; H, 3.42; N, 15.98. Found:
C, 53.02; H, 3.36; N, 15.89. Infrared spectrum (KBr disc, cmꢁ1):
cmꢁ1): 3654s (
3054 m, 2972 m, 1828w, 1714s(
(NO2)), 1478w, 1365 m, 1317s( s(NO2)), 1284s(
m
(OH)), 3446s(multiple,
as(C@O)), 1618 m, 1528s(mas
s(CAO)), 1248 m,
mas(NH)), 3329s(ms(NH)),
m
m
m
1192 m, 1016 m, 964 m, 916 m, 862 m, 796 m, 755 m, 684 m,
638 m, 602 m.
2.2.6. [(H2L2)2+ꢀ(Hptaꢁ)2] (6)
Bis(N-imidazolyl)methane (15.0 mg, 0.1 mmol) was dissolved in
1 mL methanol. To this solution was added phthalic acid (17 mg,
0.1 mmol) in 5 mL ethanol. Colorless block crystals were afforded
after several days by slow evaporation of the solvent (yield:
26.0 mg, 54.1%, based on L2). mp 132–133 °C. Elemental analysis:
Calc. for C23H20N4O8 (480.43): C, 57.45; H, 4.16; N, 11.66. Found:
C, 57.37; H, 4.11; N, 11.62. Infrared spectrum (KBr disc, cmꢁ1):
3465s(multiple,
1835w, 1782w, 1664w, 1602s(
as(NO2)), 1462w, 1384s( m
s(COOꢁ)), 1323s(
m
as(NH)), 3336s(
m
s(NH)), 3072 m, 2989 m, 1979w,
as(COOꢁ)), 1590 m, 1522s
s(NO2)), 1252 m,
m
(m
m
1194 m, 1128 m, 1064 m, 1011 m, 952 m, 903 m, 856 m, 802 m,
753 m, 726 m, 674 m, 626 m.
3665s(
2979 m, 2926 m, 1821w, 1771w, 1712s(
m, 1566s(
as(COOꢁ)), 1482 m, 1422 m, 1378s(
1288s( s(CAO)), 1239 m, 1189 m, 1128 m, 1072 m, 1028 m,
m
(OH)), 3462s(multiple,
m
as(NH)), 3376s(
as(C@O)), 1642 m, 1592
s(COOꢁ)), 1310 m,
ms(NH)), 3032 m,
2.2.2. [(H2L2)2+ꢀ(5-nsaꢁ)2] (2)
m
Bis(N-imidazolyl)methane (15.0 mg, 0.1 mmol) was dissolved in
1 mL methanol. To this solution was added 5-nitrosalicylic acid
(18.3 mg, 0.1 mmol) in 3 mL methanol. Colorless block crystals were
afforded after several days by slow evaporation of the solvent (yield:
27.0 mg, 52.5%, based on L2). mp 194–195 °C. Elemental analysis:
Calc. for C21H18N6O10 (514.41): C, 48.99; H, 3.50; N, 16.33. Found:
C, 48.95; H, 3.47; N, 16.26. Infrared spectrum (KBr disc, cmꢁ1):
m
m
m
936 m, 884 m, 818 m, 725 m, 662 m, 614 m.
2.3. X-ray crystallography
3684s(
2960 m, 1982w, 1836w, 1764w, 1598s(
as(NO2)), 1484w, 1392s( m
s(COOꢁ)), 1352 m, 1319s(
1246 m, 1193 m, 1135 m, 1084 m, 1028 m, 946 m, 852 m, 768 m,
708 m, 672 m, 637 m, 604 m.
m
(OH)), 3496s(multiple,
m
as(NH)), 3374s(
as(COOꢁ)), 1556 m, 1524s
s(NO2)),
ms(NH)), 3046 m,
Suitable crystals were performed on a Bruker SMART 1000 CCD
diffractometer using Mo Ka radiation (k = 0.71073 Å). Data collec-
m
(m
m
tions and reductions were performed using the SMART and SAINT
software [37,38]. 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
[39]. Hydrogen atom positions for the six structures were gener-
ated geometrically. Further details of the structural analysis are
summarized in Tables 1 and 2.
+
2.2.3. [(HL3) ꢀ(3,5-dnsꢁ)] (3)
1,5-Bis(1-benzimidazolyl)-3-oxapentane L3 (29 mg, 0.10 mmol)
dissolved in 3 mL ethanol. To this solution was added 3,5-dinitrosal-

222
S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
N
N
N
N
N
N
N
N
L2
L1
N
N
N
N
N
N
N
O
N
L4
L3
NO2
HO
HO
O
HO
NO2
NO2
O
3,5-dinitrobenzoic acid
5-nitrosalicylic acid
OH
O2N
O
O
HO
OH
O
O2N
OH
phthalic acid
3,5-dinitrosalicylic acid
Scheme 1. The building blocks discussed in this paper.
arise from OAH or NAH stretching frequencies. Aromatic and
imidazol ring stretching and bending are in the regions of
1500–1630 cmꢁ1 and 600–750 cmꢁ1, respectively. The compounds
1, 2, 3, and 6 show the characteristic bands for COOꢁ group. Com-
pounds 4, 5, and 6 display strong IR peaks for COOH groups. The
3. Results and discussion
3.1. Syntheses and general characterization
1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole, 1,5-bis
(1-benzimidazolyl)-3-oxapentane, bis(N-imidazolyl)methane, and
bis(N-imidazolyl)butane all have good solubility in common or-
ganic solvents, such as CH3OH, C2H5OH, CH3CN, CHCl3, and CH2Cl2.
For the preparation of 1–6, the acids were mixed directly with the
base in methanol and/or ethanol solvents in 1:1 ratio, which was
allowed to evaporate at ambient conditions to give the final crys-
talline products. The elemental analyses for the six compounds
are in good agreement with their compositions. The infrared spec-
tra of 1–6 are consistent with their chemical formulas determined
by elemental analysis and further confirmed by X-ray diffraction
analysis. The very strong and broad features at 3700–3300 cmꢁ1
bands at ca. 1530 and 1320 cmꢁ1 were attributed to the
and s(NO2), respectively [40].
mas(NO2)
m
3.1.1. X-ray structure of [(H2L12+)ꢀ(dnaꢁ)2] (1)
Salt 1 crystallizes as monoclinic pale yellow crystals in the cen-
trosymmetric space group C2/c. The asymmetric unit of 1 consists
of half a dication of 1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benz-
imidazole, and one anion of 3,5-dinitrobenzoate, as shown in Fig. 1.
This is a salt where the COOH groups of 3,5-dinitrobenzoic acids
are ionized by proton transfer to the nitrogen atoms of the 1-(3-
(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole moieties, which

S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
223
Table 1
Summary of X-ray crystallographic data for complexes 1–3.
1
2
3
Formula
Fw
C
31H24N8O12
C21H18N6O10
514.41
C25H22N6O8
534.49
700.58
T, K
298(2)
298(2)
298(2)
Wavelength, Å
Crystal system
space group
a, Å
b, Å
c, Å
0.71073
Monoclinic
C2/c
9.9370(10)
10.9609(12)
28.540(3)
90
93.6900(10)
90
3102.1(5)
4
1.500
0.118
1448
0.46 ꢂ 0.33 ꢂ 0.12
2.77–25.01
ꢁ11 6 h 6 11
ꢁ12 6 k 6 12
ꢁ33 6 l 6 20
7147
0.71073
Monoclinic
P2/c
8.6670(8)
11.0959(12)
23.328(2)
90
98.4150(10)
90
2219.3(4)
4
1.540
0.125
1064
0.40 ꢂ 0.33 ꢂ 0.32
2.55–25.02
ꢁ8 6 h 6 10
ꢁ11 6 k 6 13
ꢁ25 6 l 6 27
10923
0.71073
Triclinic
P-1
13.5757(12)
13.6543(13)
13.7485(14)
97.9990(10)
106.217(2)
91.0000(10)
2419.0(4)
4
a
, deg.
b, deg.
c
, deg.
V, Å3
Z
Dcalcd, Mg/m3
Absorption coefficient, mmꢁ1
F(0 0 0)
1.468
0.112
1112
Crystal size, mm3
h range, deg
Limiting indices
0.48 ꢂ 0.43 ꢂ 0.32
2.33–25.02
ꢁ8 6 h 6 16
ꢁ16 6 k 6 15
ꢁ16 6 l 6 16
12219
Reflections collected
Reflections independent (Rint
)
2622 (0.0890)
1.219
3915 (0.0463)
1.025
8412 (0.0299)
1.039
Goodness-of-fit on F2
R indices [I > 2
r
I]
0.1519, 0.3651
0.2123, 0.3974
0.611, ꢁ0.582
0.0523, 0.1303
0.1486, 0.1711
0.221, ꢁ0.154
0.0713, 0.1961
0.1613, 0.2615
1.059, ꢁ0.482
R indices (all data)
Largest diff. peak and hole, e Åꢁ3
Table 2
Summary of X-ray crystallographic data for complexes 4–6.
4
5
6
Formula
Fw
C
21H16N8O14
C24H22N8O14
646.50
C23H20N4O8
480.43
604.42
T, K
298(2)
298(2)
298(2)
Wavelength, Å
Crystal system
space group
a, Å
b, Å
c, Å
0.71073
Triclinic
P-1
9.554(3)
11.113(3)
12.707(4)
81.436(4)
74.756(4)
67.871(4)
1203.9(6)
2
1.667
0.143
620
0.48 ꢂ 0.40 ꢂ 0.32
2.49–28.25
ꢁ12 6 h 6 11
ꢁ14 6 k 6 9
ꢁ16 6 l 6 15
7625
0.71073
Triclinic
P-1
0.71073
Monoclinic
C2/m
15.0468(12)
18.6291(16)
8.116(10)
90
105.6730(10)
90
2190(3)
4
1.457
0.112
4.6129(4)
12.9249(13)
12.9980(13)
115.592(2)
96.4670(10)
95.0350(10)
686.39(11)
1
1.564
0.131
334
0.28 ꢂ 0.21 ꢂ 0.12
3.00–25.01
ꢁ5 6 h 6 5
ꢁ15 6 k 6 12
ꢁ14 6 l 6 15
3507
a
, deg.
b, deg.
c
, deg.
V, Å3
Z
Dcalcd, Mg/m3
Absorption coefficient, mmꢁ1
F(0 0 0)
1000
Crystal size, mm3
h range, deg
Limiting indices
0.47 ꢂ 0.38 ꢂ 0.36
2.61–25.02
ꢁ13 6 h 6 17
ꢁ22 6 k 6 22
ꢁ9 6 l 6 9
5478
Reflections collected
Reflections independent (Rint
)
5647 (0.0200)
1.035
2396 (0.0297)
0.996
2003 (0.0253)
1.037
Goodness-of-fit on F2
R indices [I > 2
r
I]
0.0503, 0.1405
0.0848, 0.1638
0.336, ꢁ0.307
0.1364, 0.3267
0.2048, 0.3626
0.763, ꢁ0.363
0.0434, 0.0990
0.0811, 0.1243
0.262, ꢁ0.234
R indices (all data)
Largest diff. peak and hole, e Åꢁ3
is also confirmed by the bond distances of O(1)AC(10) (1.221(8) Å)
and O(2)AC(10) (1.277(9) Å) for the carboxylates (Table 3). The dif-
cations display trans conformation in which the inversion center
is located at C(9).
ference (
D
is 0.056 Å) in bond distances between O(1)AC(10)
In the compound, there is one ion pair without solvent mole-
cules, which is well agreement with the micro-analysis results. In
compound 1, there exist strong electrostatic interactions between
charged cation units of NH+ and the anion of 3,5-dinitrobenzoate.
One cation and two anions generate a tricomponent adduct via
the ionic N+AHꢀ ꢀ ꢀOꢁ hydrogen bond between the NH+ cation and
(1.221(8) Å) and O(2)AC(10) (1.277(9) Å) in the carboxylate group
in compound 1 is caused by the fact that O(2) is involved in form-
ing more hydrogen bonds than that of O(1) (Table 4). L1 is doubly
protonated and the cation with the NH+ groups on the imidazole
rings in 1 resembles 4,40-H2bipy cations [41]. The protonated L1

224
S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
Fig. 1. The structure of 1, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
the carboxylate with NAO distance of 2.541(8) Å. Such kind of tri-
component adducts were linked together by the CHꢀ ꢀ ꢀO interac-
tion between the benzene CH of the cation and the nitro group
with Cꢀ ꢀ ꢀO distance of 3.404 Å, and CH2ꢀ ꢀ ꢀO association between
the propyl linker and the other O atom of the same nitro group
that is involved in CHꢀ ꢀ ꢀO interaction with Cꢀ ꢀ ꢀO distance of
3.544 Å to form a 1D chain running along the a axis direction.
Two neighboring chains were linked together by the CHꢀ ꢀ ꢀO
interaction to form a double chain, in this case, the two chains
are parallel to each other, however the corresponding cations
and anions in the two chains were antiparallelly arranged.
The double chains were stacked along the b axis direction via
Because of the presence of the intramolecular hydrogen bond be-
tween the carboxylate group and the phenol group (O(3)AH(3)ꢀ ꢀ ꢀ
O(2), 2.436(17) Å, and O(8)AH(8)ꢀ ꢀ ꢀO(7), 2.466(13) Å) (Table 4), it
is generally expected and found that the carboxylate group is nearly
coplanar with the benzene ring [torsion angle C18AC17AC16AO6,
163°, C11AC10AC9AO1, 164.79°]. There exists a hydrogen bonded
S11(6) ring in the anion. This feature is similar to that found in
salicylic acid [43], and in the previously reported structure of pro-
ton-transfer compound based on 5-nsaꢁ [44]. As expected the
OAO separation is in the lower limit of the documented data
[2.489–2.509 Å] [44], 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 C20AC21AN6AO10, 160.93°;
C13AC14AN5AO5, 172.91°] compared with the reported torsion
angle (175.4–180°) within this set of compounds [44].
Two anions were bonded to the cation through the NAHꢀ ꢀ ꢀO
hydrogen bond between the NH+ cation and the carboxylate group
with NAO distances of 2.682(7)–3.053(9) Å, and CHꢀ ꢀ ꢀO interaction
between 4-CH of the imidazole moiety and the carboxylate with
Cꢀ ꢀ ꢀO distance of 3.054 Å to form a tricomponent heteroadduct.
Here every NH+ formed two NAHꢀ ꢀ ꢀO hydrogen bonds with the
COOꢁ group in bifurcate mode. Such heteroadducts were con-
nected together via the CHꢀ ꢀ ꢀO interactions (between the 5-CH of
one imidazole and one O atom of the nitro group with Cꢀ ꢀ ꢀO dis-
tance of 3.257 Å, and between NACHAN of another imidazole in
the same cation and the other O atom of the same nitro group with
Cꢀ ꢀ ꢀO distance of 3.110 Å to form a 1D chain running along the a
axis direction. Such adjacent parallel chains were joined together
the
p–p interaction between the aromatic ring of the cation
and the benzene ring of the anion with CgACg distance of
3.388 Å, and CHꢀ ꢀ ꢀO interactions (between the NACHAN of the
cation at one chain and the O atom of the carboxylate at the
neighboring chain with Cꢀ ꢀ ꢀO distance of 3.137 Å, and between
the benzene CH of the cation and the nitro group with Cꢀ ꢀ ꢀO dis-
tance of 3.335 Å) to form a 2D sheet parallel to the ab plane
(Fig. 2). Such kind of sheets were further stacked along the c axis
direction via the CHꢀ ꢀ ꢀO association between the benzene CH of
the cation and the nitro group with Cꢀ ꢀ ꢀO distances of 3.335–
3.448 Å to form 3D network structure.
3.1.2. X-ray structure of [(H2L2)2+ꢀ(5-nsaꢁ)2] (2)
Salt 2 crystallizes as monoclinic pale yellow crystals in the cen-
trosymmetric space group P2/c. The asymmetric unit of 2 consists
of two halves of the dications of H2L2, and two 5-nitrosalicylate
anions, as shown in Fig. 3. The C18–C21, and O8 atoms were all
disordered over two positions with occupancy factor of 0.5 respec-
tively. The atoms C11–C14, and O3 were all disordered over two
positions with occupancy factor of 0.5 respectively, also. Compound
2 is also a salt where the COOH groups of 5-nitrosalicylic acids are
deprotonated, which is also confirmed by the pairs of bond
distances of O(1)AC(9) (1.260(9) Å) and O(2)AC(9) (1.249(9) Å);
O(6)AC(16) (1.252(9) Å), and O(7)AC(16) (1.255(8) Å) for the car-
boxylate (Table 3). The protonated L2 cations display trans configu-
ration in which the inversion centers are located at C(4), and C(8),
respectively.
by p–p interaction (between the anion benzene rings and the imid-
azole rings with CgACg distance of 3.275 Å), CH2ꢀ ꢀ ꢀO interaction
(between the methylene spacer of the cation and the carboxylate
group with Cꢀ ꢀ ꢀO distance of 3.221 Å), and CHꢀ ꢀ ꢀO interaction (be-
tween the NACHAN of the cation and the carboxylate with Cꢀ ꢀ ꢀO
distance of 3.210 Å) to form a 2D sheet extending along the ab
plane (Fig. 4). In the sheet there existed CHꢀ ꢀ ꢀO interactions be-
tween 5-CH of the imidazole at the fourth chain and the nitro
group at the first chain with Cꢀ ꢀ ꢀO distance of 3.230 Å, and between
the other O atom of the 5-nitro unit at the first chain and the
NACHAN of the cation at the fourth chain with Cꢀ ꢀ ꢀO distance of
3.116 Å. Such kind of sheets were further stacked along the c axis
direction via the intersheet CHꢀ ꢀ ꢀO interaction between the phenol
group of the anion and 4-CH of the imidazole of the cation with
Cꢀ ꢀ ꢀO distances of 3.239–3.243 Å to form 3D network structure.
In the solid state, there is consistently hydrogen bond formed
between the NH+ group, and the 5-nitrosalicylate ion, which is to
be expected [42]. There also exist strong coulombic interactions
between charged cation units of NH+ and the 5-nitrosalicylate
anions.

S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
225
Table 3
Table 3 (continued)
Selected bond lengths (Å) and angles (°) for 1–6.
N(3)AC(7)AN(1)
O(8)AC(15)AO(9)
109.68(17)
O(1)AC(8)AO(2)
121.8(2)
1
121.5(2)
N(1)AC(1)
N(1)AC(8)
N(2)AC(2)
N(4)AC(15)
1.337(10)
1.471(9)
1.354(10)
1.446(11)
1.277(9)
127.7(7)
106.3(7)
124.5(7)
N(1)AC(3)
N(2)AC(1)
N(3)AC(13)
O(1)AC(10)
C(1)AN(1)AC(3)
C(3)AN(1)AC(8)
N(2)AC(1)AN(1)
1.375(9)
1.288(10)
1.457(10)
1.221(8)
105.4(6)
126.2(7)
113.6(8)
5
N(1)AC(1)
N(1)AC(4)
N(2)AC(2)
N(4)AC(11)
O(2)AC(6)
C(1)AN(1)AC(3)
C(3)AN(1)AC(4)
N(2)AC(1)AN(1)
1.333(8)
1.475(8)
1.364(8)
1.459(8)
1.320(8)
108.0(5)
125.0(5)
109.1(6)
N(1)AC(3)
N(2)AC(1)
N(3)AC(9)
O(1)AC(6)
1.389(8)
1.305(8)
1.456(8)
1.214(9)
1.296(8)
126.9(6)
109.4(5)
120.8(7)
O(2)AC(10)
C(1)AN(1)AC(8)
C(1)AN(2)AC(2)
O(1)AC(10)AO(2)
O(3)AC(8)
C(1)AN(1)AC(4)
C(1)AN(2)AC(2)
O(1)AC(6)AO(2)
2
N(1)AC(1)
N(1)AC(4)
N(2)AC(3)
N(3)AC(7)
N(4)AC(5)
N(5)AO(5)
N(5)AC(14)
N(6)AO(10)
N(6)AC(21)
O(1)AC(9)
O(3)AC(11)
O(7)AC(16)
O(30)AC(110)
C(1)AN(1)AC(2)
C(2)AN(1)AC(4)
C(5)AN(3)AC(7)
C(7)AN(3)AC(8)
N(2)AC(1)AN(1)
N(4)AC(5)AN(3)
O(2)AC(9)AO(1)
1.344(8)
1.456(7)
1.360(9)
1.370(10)
1.305(9)
1.214(10)
1.4(2)
1.213(10)
1.4(3)
1.260(9)
1.36(8)
1.255(8)
1.33(10)
107.5(7)
125.7(6)
107.7(6)
125.5(6)
108.0(8)
108.8(8)
124.6(8)
N(1)AC(2)
N(2)AC(1)
N(3)AC(5)
N(3)AC(8)
1.366(10)
1.298(9)
1.335(8)
1.452(8)
1.346(9)
1.225(8)
1.5(3)
1.228(9)
1.5(3)
1.249(9)
1.252(9)
1.36(2)
6
N(1)AC(1)
N(1)AC(4)
N(2)AC(2)
O(2)AC(5)
1.329(3)
1.455(3)
1.365(3)
1.239(3)
1.271(3)
125.78(19)
109.2(2)
111.2(2)
120.4(2)
N(1)AC(3)
N(2)AC(1)
O(1)AC(5)
O(3)AC(9)
C(1)AN(1)AC(3)
C(3)AN(1)AC(4)
N(2)AC(1)AN(1)
O(2)AC(5)AO(1)
1.360(3)
1.303(3)
1.267(3)
1.227(3)
108.2(2)
125.99(17)
108.4(2)
119.7(2)
N(4)AC(6)
N(5)AO(4)
O(4)AC(9)
N(5)AC(140)
N(6)AO(9)
C(1)AN(1)AC(4)
C(1)AN(2)AC(2)
N(1)#1AC(4)AN(1)
O(3)AC(9)AO(4)
N(6)AC(210)
O(2)AC(9)
O(6)AC(16)
O(8)AC(18)
Symmetry transformations used to generate equivalent atoms for 2: #1 ꢁx + 1, y,
O(80)AC(180)
C(1)AN(1)AC(4)
C(1)AN(2)AC(3)
C(5)AN(3)AC(8)
C(5)AN(4)AC(6)
N(1)#1AC(4)AN(1)
N(3)AC(8)AN(3)#2
O(6)AC(16)AO(7)
1.31(2)
ꢁz + 1/2; #2 ꢁx, y, ꢁz + 1/2.
126.4(6)
110.0(7)
126.5(6)
108.7(7)
112.4(8)
112.8(9)
124.0(8)
Symmetry transformations used to generate equivalent atoms for 6: #1 ꢁx, y,
ꢁz + 2.
3.1.3. X-ray structure of [(HL3)+ꢀ(3,5-dnsꢁ)] (3)
Crystallization of 1,5-bis(1-benzimidazolyl)-3-oxapentane and
3,5-dinitrosalicylic acid in a 1:1 ratio from the mixed solvent of
methanol and ethanol gave single crystals suitable for X-ray
diffraction. Structure determination (Table 1) revealed that 1,5-
bis(1-benzimidazolyl)-3-oxapentane and 3,5-dinitrosalicylic acid
are present in a 1:1 ratio in the molecular complex 3. The crystal
structure of 3 consists of two halves of monoprotonated L3, and
two halves of monoanion of 3,5-dinitrosalicylic acid in
the asymmetric unit (Fig. 5). Different from the salts 1–2, here
the bis-N-imidazole is monoprotonated. The reason may be that
this molecule(L3) may be too flexible introducing factors that re-
sult more important than the small difference between the donors
to decide the preferred molecular interactions. In 3 the COOH
groups of 3,5-dinitrosalicylic acids are ionized by proton transfer
to the nitrogen atoms of the benzimidazole moieties, and the phe-
nol OH group remains protonized.
3
N(1)AC(1)
N(1)AC(15)
N(2)AC(2)
N(3)AC(10)
N(4)AC(8)
N(5)AC(19)
N(5)AC(33)
N(6)AC(20)
N(7)AC(28)
N(8)AC(26)
N(9)AC(40)
N(11)AC(47)
O(1)AC(17)
1.341(5)
1.470(5)
1.383(5)
1.377(5)
1.327(5)
1.335(5)
1.457(5)
1.384(6)
1.361(7)
1.309(6)
1.458(6)
1.502(7)
1.416(5)
1.417(6)
1.276(6)
1.243(8)
1.263(7)
125.7(4)
106.9(4)
127.5(4)
104.9(4)
124.6(4)
107.4(4)
127.6(5)
105.4(4)
112.9(4)
113.8(5)
124.2(4)
N(1)AC(3)
N(2)AC(1)
N(3)AC(8)
N(3)AC(18)
N(4)AC(9)
N(5)AC(21)
N(6)AC(19)
N(7)AC(26)
N(7)AC(36)
N(8)AC(27)
N(10)AC(42)
O(1)AC(16)
O(2)AC(35)
O(3)AC(37)
O(5)AC(39)
O(11)AC(44)
C(1)AN(1)AC(3)
C(3)AN(1)AC(15)
C(8)AN(3)AC(10)
C(10)AN(3)AC(18)
C(19)AN(5)AC(21)
C(21)AN(5)AC(33)
C(26)AN(7)AC(28)
C(28)AN(7)AC(36)
N(2)AC(1)AN(1)
N(6)AC(19)AN(5)
O(3)AC(37)AO(4)
O(11)AC(44)AO(10)
1.393(5)
1.295(5)
1.341(5)
1.464(5)
1.391(5)
1.391(5)
1.318(5)
1.348(6)
1.469(6)
1.379(6)
1.454(6)
1.402(5)
1.402(6)
1.234(6)
1.267(5)
1.243(7)
106.8(3)
127.5(3)
107.1(3)
125.4(3)
107.6(4)
127.7(4)
105.8(4)
126.6(4)
112.5(4)
111.6(4)
123.1(5)
120.7(7)
O(2)AC(34)
O(4)AC(37)
O(10)AC(44)
O(12)AC(46)
C(1)AN(1)AC(15)
C(1)AN(2)AC(2)
C(8)AN(3)AC(18)
C(8)AN(4)AC(9)
C(19)AN(5)AC(33)
C(19)AN(6)AC(20)
C(26)AN(7)AC(36)
C(26)AN(8)AC(27)
N(4)AC(8)AN(3)
N(8)AC(26)AN(7)
O(5)AC(39)AC(40)
The CAO distances in the carboxylate O(10)AC(44)AO(10) are
almost equal with each other within the experimental error, indi-
cating that the negative charge was distributed equally on both O
atoms. While for the COOꢁ group O(3)AC(37)AO(4), two CAO bond
lengths (The CAO distances of COOꢁ of the 3,5-dinitrosalicylate are
ranging from 1.234(6) (O(3)AC(37)) to 1.276(6) Å (O(4)AC(37)
with
D = 0.042 Å) are basically not equal with an average value
of 1.255(6) Å (Table 3). The significantly difference between the
two bonds is attributed to the fact that O4 atom is involved in
forming more hydrogen bonds than that of O3 (Table 4).
All the benzimidazole rings are essentially planar with the larg-
est deviation from the mean plane of 0.0199 Å. The HL3 adopts cis
configuration with the planes of the two benzimidazole rings in the
same cation inclined by 6.4° (for the cation bearing N3, and N4
atoms), and 15.7° (for the cation bearing N7, and N8 atoms) for
the two independent cations, respectively. The benzimidazole
rings formed dihedral angles of 65 ° (for the ring bearing N1, and
N2 atoms), 71.1° (for the ring bearing N3, and N4 atoms), 64.6°
(for the ring bearing N5, and N6 atoms), and 72.1° (for the ring
bearing N7, and N8 atoms) with the plane defined by the oxapen-
tane spacer.
4
N(1)AC(1)
N(1)AC(7)
N(2)AC(2)
N(3)AC(6)
1.327(3)
1.464(3)
1.352(4)
1.376(3)
1.307(3)
1.441(3)
1.456(3)
1.236(3)
1.279(3)
1.299(3)
108.1(2)
126.43(19)
108.3(2)
126.15(19)
109.0(2)
N(1)AC(3)
N(2)AC(1)
N(3)AC(4)
N(3)AC(7)
N(4)AC(5)
N(6)AC(11)
N(8)AC(20)
O(2)AC(8)
O(8)AC(15)
O(10)AC(17)
C(1)AN(1)AC(7)
C(1)AN(2)AC(2)
C(4)AN(3)AC(7)
C(4)AN(4)AC(5)
N(4)AC(4)AN(3)
1.372(3)
1.309(3)
1.327(3)
1.451(3)
1.363(3)
1.452(3)
1.448(3)
1.291(3)
1.233(3)
1.277(2)
125.5(2)
108.8(2)
125.3(2)
109.2(2)
108.7(2)
N(4)AC(4)
N(5)AC(13)
N(7)AC(18)
O(1)AC(8)
O(3)AC(10)
O(9)AC(15)
C(1)AN(1)AC(3)
C(3)AN(1)AC(7)
C(4)AN(3)AC(6)
C(6)AN(3)AC(7)
N(2)AC(1)AN(1)
The torsion angles O8AN10AC42AC43, and O6AN9AC40AC41
are 178.14°, and 178.63°, respectively. In this regard, both nitro

226
S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
Table 4
(for the O15AN12AO16 group) respectively from the phenyl ring
plane of the anion. Herein the 3-nitro unit (the O13AN11AO14
group) is essentially coplanar with the phenyl ring of the anion,
while the 5-nitro group (O15AN12AO16 group) is rotated out of
the plane.
Hydrogen bond distances and angles in studied structures 1–6.
DAHꢀ ꢀ ꢀA
d(DAH)
(Å)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
<(DHA)
(°)
(Å)
(Å)
1
N(2)AH(2)ꢀ ꢀ ꢀO(2)#2
2
0.86
1.74
2.541(8)
154.0
Since the potentially hydrogen bonding hydroxyl group is pres-
ent in the ortho position to the carboxyl group in the anion, it forms
the more facile intramolecular hydrogen bonding. Thus the usual
intramolecular hydrogen bond is found between the phenol OH
group and a carboxylate O atom (O(5)AH(5A)ꢀ ꢀ ꢀO(4), 2.436(5) Å,
151.9° O(12)AH(12)ꢀ ꢀ ꢀO(11), 2.512(9) Å, 149.8°) which is similar
to the corresponding value (2.409 Å) in proton-transfer compound
of [(hmt)+ [(dnsa)ꢁ] [46,47]. Yet the value is as expected generally
smaller than the distance found for the parent dnsa acid monohy-
drate [2.566(3) Å] [48], and in the neutral species found in the ad-
duct compound. For the presence of the intramolecular hydrogen
bond, there also exists hydrogen bonded motif with graphical
descriptor of S11(6).
N(2)AH(2)ꢀ ꢀ ꢀO(6)#3
N(2)AH(2)ꢀ ꢀ ꢀO(7)#3
N(4)AH(4)ꢀ ꢀ ꢀO(1)#1
N(4)AH(4)ꢀ ꢀ ꢀO(2)#1
O(3)AH(3)ꢀ ꢀ ꢀO(2)
O(8)AH(8)ꢀ ꢀ ꢀO(7)
O(30)AH(30)ꢀ ꢀ ꢀO(2)
O(80)AH(80)ꢀ ꢀ ꢀO(7)
0.86
0.86
0.86
0.86
0.82
0.82
0.82
0.82
1.83
2.56
1.83
2.53
1.71
1.72
1.79
1.73
2.684(7)
3.053(9)
2.682(7)
3.027(9)
2.436(17)
2.466(13)
2.521(15)
2.450(15)
169.5
117.3
171.8
117.3
146.1
149.9
146.9
144.8
3
O(12)AH(12)ꢀ ꢀ ꢀO(11)
O(4)AH(4A)ꢀ ꢀ ꢀO(5)
N(6)AH(6)ꢀ ꢀ ꢀN(8)#1
N(2)AH(2)ꢀ ꢀ ꢀN(4)#2
0.82
0.82
0.86
0.86
1.77
1.68
1.81
1.81
2.512(9)
2.436(5)
2.665(5)
2.671(5)
149.8
151.9
176.7
175.6
Two monoprotonated cations were linked together in head to
tail fashion via the NAHꢀ ꢀ ꢀN hydrogen bond with NAN separation
of 2.671 Å to form a dimer. In the dimer the two cations were
inversionally related and formed a 24-membered ring. The cation
dimers were connected together by a pair of antiparallelly ar-
ranged anions through the CHꢀ ꢀ ꢀO associations to form a 1D chain
running along the c axis direction. In this regard one kind of CHꢀ ꢀ ꢀO
interaction is produced between the benzene CH of the cation and
the 5-nitro group of the anion with Cꢀ ꢀ ꢀO distance of 3.502 Å, the
other kind of CHꢀ ꢀ ꢀO interaction is made between the phenol group
of the anion and the benzene CH of the cation with Cꢀ ꢀ ꢀO distance
of 3.445 Å. Such kind of 1D parallel chains were joined together by
CH2ꢀ ꢀ ꢀO interaction between the CH2 unit of the oxapentane spacer
4
O(9)AH(9)ꢀ ꢀ ꢀO(6)#1
0.82
0.82
2.64
1.72
2.64
1.71
1.91
1.88
3.037(3)
2.477(2)
3.072(3)
2.469(2)
2.723(3)
2.718(3)
111.5
153.7
114.8
154.2
157.4
165.1
O(9)AH(9)ꢀ ꢀ ꢀO(10)
O(2)AH(2A)...O(13)#2 0.82
O(2)AH(2A)ꢀ ꢀ ꢀO(3)
N(4)AH(4)ꢀ ꢀ ꢀO(8)
N(2)AH(2)ꢀ ꢀ ꢀO(1)#3
0.82
0.86
0.86
5
O(2)AH(2A)ꢀ ꢀ ꢀO(3)
N(2)AH(2)ꢀ ꢀ ꢀO(4)#2
N(2)AH(2)ꢀ ꢀ ꢀO(3)#2
0.82
0.86
0.86
1.76
2.29
1.92
2.523(6)
2.890(8)
2.715(7)
153.1
126.7
154.1
6
O(4)AAH(4)ꢀ ꢀ ꢀO(4)#3 0.82
1.54
1.55
2.50
1.84
2.362(4)
2.371(3)
3.093(3)
2.695(4)
175.2
177.1
127.1
174.9
O(1)AH(1)ꢀ ꢀ ꢀO(1)#2
N(2)AH(2) ꢀ ꢀ ꢀO(1)#4
N(2)AH(2) ꢀ ꢀ ꢀO(2)#4
0.82
0.86
0.86
and the 5-nitro group with Cꢀ ꢀ ꢀO distance of 3.586 Å, CH2–
action between the CH2 of the oxapentane spacer and the aromatic
ring of the cation with CACg distance of 3.549 Å, and interac-
p inter-
Symmetry transformations used to generate equivalent atoms for 1: #2 x + 1, y, z.
Symmetry transformations used to generate equivalent atoms for 2: #1 ꢁx + 1, y,
ꢁz + 1/2; #3 x ꢁ 1, y + 1, z.
p–p
tions between the benzimidazole rings of the cation with CgACg
distance of 3.313 Å to form 2D sheet structure extending in the
direction that made an angle of ca 45° with the bc plane (Fig. 6).
Such kind of sheets were further stacked along the direction that
is perpendicular with its extending direction via the CH2ꢀ ꢀ ꢀO asso-
ciation (between the CH2 of the oxapentane spacer and the carbox-
ylate with Cꢀ ꢀ ꢀO distance of 3.362 Å, and between the CH2 of the
oxapentane spacer and the 5-nitro group with Cꢀ ꢀ ꢀO distance of
3.502 Å), and CHꢀ ꢀ ꢀO interactions (between the benzene CH of
the cation and the 5-nitro group of the anion with Cꢀ ꢀ ꢀO distance
of 3.437 Å, and between the NACHAN of the imidazole moiety
and the nitro and the carboxylate units belonging to two different
anions respectively with Cꢀ ꢀ ꢀO distances of 3.231–3.121 Å) to form
3D layer network structure.
Symmetry transformations used to generate equivalent atoms for 3: #1 ꢁx + 2,
ꢁy + 1, ꢁz; #2 ꢁx + 2, ꢁy + 2, ꢁz.
Symmetry transformations used to generate equivalent atoms for 4: #1 ꢁx + 1,
ꢁy + 2, ꢁz + 1; #2 ꢁx + 2, ꢁy + 2, ꢁz + 2; #3 x ꢁ 1, y, z ꢁ 1.
Symmetry transformations used to generate equivalent atoms for 5: #2 ꢁx, ꢁy + 1,
ꢁz + 2.
Symmetry transformations used to generate equivalent atoms for 6: #2 x, ꢁy + 2, z;
#3 x, ꢁy + 1, z; #4 x, y ꢁ 1, z + 1.
groups are nearly in the same plane as the benzene ring of the
anion, yet the 3-nitro (O6AN9AO7) deviates somewhat less from
the plane than the 5-nitro (O8AN10AO9) group, which is different
from the published results [45]. While the nitro groups in the other
anion deviate 178.37° (for the O13AN11AO14 group), and 166.79 °
Fig. 2. 2D sheet structure of 1 running parallel to the ab plane.

S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
227
Fig. 3. The structure of 2, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
Fig. 4. 2D sheet structure of 2 extending along the ab plane.
3.1.4. X-ray structure of [(H2L2)2+ꢀ(3,5-dnsꢁ)2] (4)
NACHAN of the cation and the 3-nitro group with Cꢀ ꢀ ꢀO distances
of 3.118–3.204 Å to form a double chain. Such kind of double
chains were further stacked along the a axis direction by the
The compound 4 crystallizes as Triclinic block crystals in the
space group P-1. The asymmetric unit of 4 consists of one cation
of bis(N-imidazolylium)methane, and two independent monoa-
nions of 3,5-dinitrosalicylate, as shown in Fig. 7. Similar to 3, com-
pound 4 is also an organic salt. However in this case it is the phenol
H that has been deprotonated which is different from 3. The CAO
distances 1.279(3) Å (O(3)AC(10)), and 1.277(2) Å (O(10)AC(17))
concerning the phenolate are similar to the proton transfer com-
pound bearing the 3,5-dnsꢁ in which only the phenol group has
been deprotonated [49]. The CAO distances O(1)AC(8), 1.236(3),
O(2)AC(8), 1.291(3); O(8)AC(15), 1.233(3) Å, O(9)AC(15),
1.299(3) Å in the COOH show characteristic C@O, and CAO dis-
tances which are also confirming the reliability of adding H atoms
experimentally by different electron density onto O atoms as men-
tioned above (Table 3).
p–p interactions between the benzene ring of the anion with
CgACg distance of 3.388 Å and CHꢀ ꢀ ꢀO interaction between 4-CH
of the imidazole of one double chain and the carbonyl of its adja-
cent double chain with Cꢀ ꢀ ꢀO distance of 3.300 Å to form a sheet
extending parallel to the ac plane (Fig. 8). The thickness of the
sheet is ca. 15.638 Å. Such kind of sheets were stacked along the
b axis direction by the intersheet CHꢀ ꢀ ꢀO (between 4-CH of the cat-
ion at one sheet and the carbonyl unit of its neighboring sheet
with Cꢀ ꢀ ꢀO distance of 3.480 Å), and CH2ꢀ ꢀ ꢀO interactions to form
3D ABAB layer network structure. Herein every H of the CH2
spacer in the cation made a bifurcate CH2ꢀ ꢀ ꢀO association with
the phenolate and the 3-nitro groups in the same anion to gener-
ate a R12(6) ring in which the Cꢀ ꢀ ꢀO distances are ranged from
The anions were linked together via the OAHꢀ ꢀ ꢀO hydrogen
bond between the COOH moiety and the 5-nitro group with
OAO distances of 3.037(3)–3.072(3) Å to form a 1D chain running
along the c axis direction. Herein the adjacent anions are in the
same plane and rotate about 45° from each other, while the third
anion is parallel to the first anion in the chain, so does the second
anion and the fourth anion. Two neighboring chains were com-
bined together by the cations via the NAHꢀ ꢀ ꢀO association be-
tween the NH+ cation and the carbonyl group of the anion with
NAO distance of 2.723(3) Å and CHꢀ ꢀ ꢀO association between the
3.226 Å to 3214 Å. There also found intersheet O–p interaction be-
tween the O atom of the 5-nitro group and the imidazole ring with
OACg distance of 2.931 Å. The OACg distance in 4 is significantly
shorter than that found in the archived data (3.12 Å) [50]. In this
regard the corresponding anions and the cations between two
adjacent layers were antiparallelly arranged. The anions at the first
layer were parallel to the anions at the third layer, and the cations
at the first layer were also parallel to the cations at the third layer,
so did the corresponding anions and cations at the second layer
and the fourth layer.

228
S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
has ionized, while the COOH remains protonized. The CAO dis-
tances of the COOH of 3,5-dinitrosalicylate are ranging from
1.214(9) Å (O(1)AC(6)) to 1.320(8) Å (O(2)AC(6)) with the value
D
of 0.106 Å, which suggests that the carboxyl group is protonated. In
the cation, protonation at atom N2 leads to an increase in the
C(1)AN(2)AC(2) [109.4(5)°] angle compared to that observed in
the neutral L4 (104.15(4)°), and this angle is almost equal to the
corresponding angle on its hydrochloride salt (109.08(3)°) [51]. It
was found that protonation of the imidazole ring nitrogen atoms
causes no significant change in conformation of the (H2L4)2+ dica-
tion in 5 in comparison to the corresponding neutral molecule
1-(4-(1H-imidazol-1-yl)butyl)-1H-imidazole (L4) [51]. The imidaz-
ole rings in 5 have trans-(ap) position in respect to C4AC5 bond
(angle C4AC5AC4AAC5A, 180°), which is different from the corre-
sponding 1,10-(1,4-butanediyl)bis(imidazolium) dihydrochloride
[51]. The two imidazole rings in the same cation were antiparallel-
ly arranged.
The nitro groups N3AO4AO5, and N4AO6AO7 deviate by 6°,
and 6.3° from the mean plane of the phenyl ring of the anion.
The carboxyl group deviated by only 3° from the phenyl ring plane
of the 3,5-dinitrosalicylate.
At each cation there are bonded two anions via the bifurcated
NAHꢀ ꢀ ꢀO association between the NH+ cation and the phenolate
and the 3-nitro group respectively with NAO distances of
2.715(7)–2.890(8) Å to generate a bicomponent adduct. For the
presence of these two hydrogen bonds, there are hydrogen bonded
R12(6) ring in the bicomponent heteroadduct. There also exists
intramolecular OAHꢀ ꢀ ꢀO hydrogen bond with graph set of S11(6)
between the COOH unit and the phenolate with OAO separation
of 2.523 Å. Such kind of bicomponent heteroadducts were linked
together via the CH2ꢀ ꢀ ꢀO association between the CH2 group of
the butane spacer and the 5-nitro unit with Cꢀ ꢀ ꢀO distance of
3.117 Å to form a 1D chain running along the c axis direction
(Fig. 10). Such kind of chains were combined together via the
Fig. 5. The structure of 3, showing the component of the title compound (for the
crowdedness of the structure the atom-numbering was not labeled). Displacement
ellipsoids were drawn at the 30% probability level.
3.1.5. X-ray structure of [(H2L4)2+ꢀ(3,5-dnsꢁ)2] (5)
Similar to the salt 4, the asymmetric unit of 5 consists of half a
dication of N,N/-butylenebis(imidazole), and one monoanion of
3,5-dnsꢁ, as shown in Fig. 9. Here it is also the phenol group that
Fig. 6. 2D sheet structure of 3 which is extending in the direction that made an angle of ca 45° with the bc plane.
Fig. 7. The structure of 4, showing the atom-numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.

S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
229
Fig. 8. 2D sheet structure of 4 built from double chains via p–p, and CHAO interactions, which is extending parallel to the ac plane.
Fig. 9. The structure of 5, showing the atom-numbering scheme. Displacement
ellipsoids were drawn at the 30% probability level.
Fig. 11. The structure of 6, showing the atom-numbering scheme. Displacement
ellipsoids were drawn at the 30% probability level.
CHꢀ ꢀ ꢀO interactions (between 4-CH of the anion and 5-nitro of the
anion belonging to different chains with Cꢀ ꢀ ꢀO distance of 3.424 Å,
between NACHAN of the cation and the carbonyl group of the an-
ion with Cꢀ ꢀ ꢀO distance of 3.202 Å, and between 5-CH of the imid-
azole and 3-nitro group of the anion with Cꢀ ꢀ ꢀO distance of
3.211 Å) to form 3D network structure.
axis direction, yet there are not any interactions between such
neighboring chains. In this case the anions at two adjacent chains
were antiparallelly arranged and slipped some distance from each
other along the c axis direction. The third anion chain has the same
projection on the bc plane as the first anion chain, so does the sec-
ond anion chain and the fourth anion chain. Such discrete anion
chains also extend parallelly in the bc plane, the anions at the third
chain in the bc plane were parallel to the anions at the first chain,
but the anions at the neighboring chains were antiparallel to each
other. Two adjacent anionic chains were combined together along
the a axis direction by the cations via the NAHꢀ ꢀ ꢀO, and CHꢀ ꢀ ꢀO
associations to form 1D flat pipelike structure in which the width
of the flat pipe is ca. half the length of the b axis. Here the NH+
group functioned as bifurcate donor forming two NAHꢀ ꢀ ꢀO hydro-
gen bonds with the same carboxylate group with NAO distances in
the range of 2.696–3.093 Å. The CHꢀ ꢀ ꢀO interactions are found be-
tween NACHAN of the cation and the carboxylate with Cꢀ ꢀ ꢀO dis-
tance of 3.242 Å. There are also anion chains that are not bonded
with the cations through the NAHꢀ ꢀ ꢀO hydrogen bonds. The flat
pipelike structure and the anion chains not bonded with the cat-
ions are arranged alternatively on the bc plane, and they are joined
3.1.6. X-ray structure of [(H2L2)2+ꢀ(Hptaꢁ)2] (6)
The asymmetric unit of 6 consists of half a dication of bis(N-
imidazolyl)methane, and two halves of monoanion of phthalic
acid, which is shown in Fig. 11. Here the acidic Hs at the hydrogen
phthalate were disordered over the COOꢁ and COOH groups each
with occupancy factor of 0.5, respectively. The cation also displays
trans conformation. Similar with the reported adduct of phthalate
[52], the carboxylates in the anion are almost in the same plane
as the phenyl ring.
The anions formed a 1D chain along the c axis direction via the
CHꢀ ꢀ ꢀO interactions between the benzene CH of one anion and the
carboxylate group of its neighboring anion with Cꢀ ꢀ ꢀO distances of
3.369–3.410 Å. In the chain the anions were arranged in head to
tail fashion. Such parallel anionic chains were packed along the a
Fig. 10. 1D chain structure of 5 which is running along the c axis direction.

230
S. Jin et al. / Journal of Molecular Structure 1022 (2012) 220–231
Fig. 12. 2D sheet structure of 6 when viewed from the a axis direction.
together via the CH2ꢀ ꢀ ꢀO interaction (between the methylene
bridge of the cation and one O atom of the carboxylate with
Cꢀ ꢀ ꢀO distance of 3.138 Å), CHꢀ ꢀ ꢀO interaction (between the
NACHAN of the imidazole and the other O of the same carboxylate
also
were found in 6, while 3 possesses CH2–
the O– interaction.
p
–
p
associations in compounds 1–4. The CH–
p interactions
p
interaction. Salt 4 bears
p
In conclusion, we have shown that 3D structures can be con-
structed by synergistic effect of the various noncovalent interac-
tions such as strong directional hydrogen bond (N+AHꢀ ꢀ ꢀOꢁ,
with Cꢀ ꢀ ꢀO distance of 3.107 Å), and CH–p interaction (between the
benzene CH of the anion and the imidazole ring of the cation with
CACg distance of 3.652 Å) to form 2D sheet structure (Fig. 12).
Such kind of 2D sheets were further stacked along the a axis direc-
tion via the intersheet CHꢀ ꢀ ꢀO interactions between 4-CH of the
imidazole moiety and the carboxylate with Cꢀ ꢀ ꢀO distance of
3.165 Å to form 3D ABAB layer network structure. In this regard
the second sheet was slipped about half the b axis length along
the b axis direction, while the third sheet has the same projection
on the bc plane as the first sheet, so does the fourth sheet and the
second sheet.
OAHꢀ ꢀ ꢀO, and NAHꢀ ꢀ ꢀN), CHAO/CH2AO,
p–p, CH–p, CH2–p, and
O–p interactions between discrete components.
Supporting information
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic data center, CCDC
Nos. 851526 for 1, 858644 for 2, 858645 for 3, 851525 for 4,
851524 for 5, and 835839 for 6. 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.
4. Conclusion
Acknowledgements
Six organic acid–base salts with 3D frameworks have been pre-
pared and structurally characterized. The different hydrogen bond
interaction modes of the carboxylic acid and the bis(imidazole)
lead to a wide range of different structures such as 3D network
structure, 3D layer network structure, and 3D ABAB layer structure.
Of the six salts five examples (1, 2, 4, 5, and 6) involve proton
transfer from the carboxylic acids to both N atoms of the bis(imid-
azole) molecules to form a dication, while in salt 3, the bis(imidaz-
ole) molecule of L3 is only monoprotonated to exhibit a valence
number of + 1.
We gratefully acknowledge the financial support of the Educa-
tion Office Foundation of Zhejiang Province
Y201017321), the financial support of the Xinmiao project of the
Education Office Foundation of Zhejiang Province, and the Zhejiang
Provincial Natural Science Foundation (Y5090179).
(Project No.
Appendix A. Supplementary material
This study has demonstrated that the NAHꢀ ꢀ ꢀO/OAHꢀ ꢀ ꢀO hydro-
gen bonds are the primary intermolecular force in a family of struc-
tures containing the OHꢀ ꢀ ꢀim synthons. Except the classical
hydrogen bonding interactions, the secondary propagating interac-
tions also made significant contribution to the structure extension.
All salts possess weak CAHꢀ ꢀ ꢀO/CH2ꢀ ꢀ ꢀO associations. Two types of
secondary CAHꢀ ꢀ ꢀO/CH2ꢀ ꢀ ꢀO interactions were observed based
upon their geometric preferences, intra- and interchain interac-
tions. Based upon an analysis of the metrics displayed by each
set of interactions, it seems that intra- and interchain CAHꢀ ꢀ ꢀO/
CH2ꢀ ꢀ ꢀO interactions are of equal structural importance. There are
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.molstruc.
2012.04.082.
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