The supramolecular assemblies of 7-amino-2,4-dimethylquinolinium salts and the effect of a variety of anions on their luminescent properties

Article abstract of DOI:10.1039/c2ce25883h

The 7-amino-2,4-dimethylquinolinium salts with a variety of anions (Cl ^-, HCOO^-, CH₃COO^-, PhCOO ^-, l-HOOCCH(OH)CH(OH)COO^-) have been synthesized and characterized. The crystal structures of these salts were determined by single-crystal X-ray diffraction. The structure analysis confirms that the nitrogen atoms in the quinoline rings are protonated in all salts. The two solvates have been obtained and thereby provide a useful complement to cocrystal screening. All the quinolinium salts display interesting three dimensional supramolecular networks. The hydrogen bonding interactions observed in all of the salts are N-H...O, O-H...O and N-H...Cl, together with weak C-H...O, C-H...N, C-H...Cl hydrogen bonds. The weak C/N-H...π contacts and π-π stacking interactions involving the quinoline moieties also exist in quinolinium salts. The observed noncovalent interactions become prominent in stabilizing their crystal packing. The 7-amino-2,4-dimethylquinolinium salts show strong luminescence in the solid state and solution in the range 422-534 nm. The solid-state emission spectra of the quinolinium salts are sensitive to the anion species, and highly dependent on the nature of the stacking interactions. This journal is

Full text of DOI:10.1039/c2ce25883h

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PAPER
The supramolecular assemblies of 7-amino-2,4-dimethylquinolinium salts and
the effect of a variety of anions on their luminescent properties{
Qing Su, Mina He, Qiaolin Wu,* Wei Gao, Hai Xu, Ling Ye and Ying Mu*
Received 13th February 2012, Accepted 20th July 2012
DOI: 10.1039/c2ce25883h
The 7-amino-2,4-dimethylquinolinium salts with a variety of anions (Cl2, HCOO2, CH3COO2,
PhCOO2, L-HOOCCH(OH)CH(OH)COO2) have been synthesized and characterized. The crystal
structures of these salts were determined by single-crystal X-ray diffraction. The structure analysis
confirms that the nitrogen atoms in the quinoline rings are protonated in all salts. The two solvates
have been obtained and thereby provide a useful complement to cocrystal screening. All the
quinolinium salts display interesting three dimensional supramolecular networks. The hydrogen
…
bonding interactions observed in all of the salts are N–H O, O–H O and N–H Cl, together with
…
…
…
…
…
…
weak C–H O, C–H N, C–H Cl hydrogen bonds. The weak C/N–H p contacts and p–p stacking
interactions involving the quinoline moieties also exist in quinolinium salts. The observed
noncovalent interactions become prominent in stabilizing their crystal packing. The 7-amino-2,4-
dimethylquinolinium salts show strong luminescence in the solid state and solution in the range 422–
534 nm. The solid-state emission spectra of the quinolinium salts are sensitive to the anion species,
and highly dependent on the nature of the stacking interactions.
strategy in the formation of supramolecular assemblies.
Introduction
Recently, the various hydrogen bonding patterns involving
Noncovalent interactions such as hydrogen bonding, ionic
interactions, metal coordination, and p–p interactions, as well
as other weak forces play crucial roles in many fields, such as
supramolecular chemistry, host–guest chemistry, biochemistry,
pharmaceutical chemistry, molecular recognition, and materials
science.1–3 In recent years, many efforts have been focused on
investigating these interactions and clarifying their relationship
to supramolecular structures.4 As an example of one of the most
sophisticated supramolecular systems, the double-helical DNA
structure5 is assembled through multiple Watson–Crick hydro-
gen bonding and p–p stacking interactions, offering significant
opportunities to mimic nature’s systems for fundamental studies
and numerous biochemical and biomedical applications.6 In the
case of active pharmaceutical ingredients (APIs), the different
solid forms such as solvates, hydrates, polymorphs, salts and co-
crystals with tailoring biopharmaceutical properties have been
explored systematically,7 which are relevant with supramolecular
synthesis and crystal engineering. Most of these investigations
indicate that the combination of hydrogen bonding and/or other
weak interactions has been used as a very powerful and versatile
pyridine–carboxylate interactions are of significance in crystal
8
engineering. Moreover, the N–H O/N and O–H O hydrogen
…
…
…
bonds, together with weak C–H O/N hydrogen bonds have
been used in the design of a number of supramolecular
nanoarchitectures, layers, rosettes, rods, tubes, tapes, ribbons,
sheets, and spheres aggregates.9 In addition, It is well known that
the hydrogen bonding interactions between carboxylate groups
and the pyrimidine moieties have been considered as the models
for protein–nucleic acid recognition and drug–receptor recogni-
tion. Supramolecular architectures based on molecular recogni-
tion between complementary molecular components and self-
assemblies of organic molecules with the assistance of non-
covalent forces are of current interest.10
We have previously reported a series of Schiff zinc(II)
complexes containing 7-amino-2,4-dimethylquinolinyl with a
variety of coordination geometries by modifications of the
ligand denticity, the ligand-to-metal ratio, and non-covalent
interactions.11 In our previous studies, an organic salt of
7-amino-2,4-dimethylquinoline with formic acid has also been
reported,12 and the result reveals that the nitrogen atom in the
pyridine ring is protonated when the carboxyl is deprotonated,
State Key Laboratory for Supramolecular Structure and Materials, School
of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012,
People’s Republic of China. E-mail: wuql@jlu.edu.cn; ymu@jlu.edu.cn;
Fax: (+86)-431-5193421; Tel: (+86)-431-5168376
{ Electronic Supplementary Information (ESI) available: CCDC refer-
ence numbers 294744, 866261–866264. Crystallographic data in CIF or
other electronic format. Synthetic route of the quinolinium salts in
Schemes S1 and S2. The photophysical data in Table ST-1. See DOI:
10.1039/c2ce25883h
…
and the crystal packing is stabilized by N–H O hydrogen bonds
and p–p stacking interactions. The adjacent chains are held
…
together by N–H O hydrogen bonds with a rectangular cavity.
Very recently, we have focused our continuing efforts on the
construction of well-defined supramolecular structures of
7-amino-2,4-dimethylquinolinium salts, and understanding the
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anion effects on the supramolecular assemblies and luminescent
properties of 7-amino-2,4-dimethylquinolinium salts. The hydro-
gen chloride, formic acid, acetic acid, benzoic acid, and L-tartaric
acid were chosen for this study mainly because those Lewis acids
with different volumes of the anion are good for selective and
directional geometry-based crystal design to generate interesting
298 K): d 2.58 (s, 3H, CH3), 2.63 (s, 3H, CH3), 4.02 (s, 2H, NH2),
6.89 (s, 1H, 3-H), 6.93 (d, 1H, 6-H), 7.18 (s, 1H, 8-H), 7.75 (d,
1H, 5-H) ppm. 13C NMR (CDCl3, 125.75 MHz, 298 K): d 18.4
(CH3), 25.1 (CH3), 109.5, 117.1, 119.6, 120.2, 124.7, 143.9, 147.5,
149.5, 158.8 ppm. IR (KBr, cm21): 3370 (s), 3307 (m), 3180 (s),
3026 (m), 2949 (m), 2920 (m), 2855 (m), 2745 (w), 1885 (w), 1640
(s), 1597 (s), 1525 (s), 1421 (s), 1356 (m), 1291 (m), 1236 (m),
1151 (m), 1126 (w), 1068 (w), 1027 (w), 884 (w), 844 (m), 815 (m),
772 (w), 707 (w), 662 (m), 599 (m), 543 (w).
supramolecular architectures. Notably, the crystal packing
…
should be dominated by strong hydrogen bonding N–H
O
…
…
and much weaker C–H N, C–H p and p–p interactions.
Herein, we wish to report the supramolecular assemblies of a
series of 7-amino-2,4-dimethylquinolinium salts, as well as the
anion effects on both crystal packing and their luminescent
properties in the solid state and solution.
7-Amino-2,4-dimethylquinolinium formate (1?HCOOH)
To a solution of 7-amino-2,4-dimethylquinoline (0.31 g, 1.80
mmol) in 10 mL of ethanol was added 0.07 mL of formic acid
(1.80 mmol) at room temperature. After stirring for 0.5 h, the
volatile materials were removed in vacuo. The residue was
washed with ethyl ether and dried to give yellow-green solid.
Yield: 0.37 g, 95%. Anal. Calcd for C12H14N2O2 (218.25): C
66.04, H 6.47, N 12.84; Found: C 66.15, H 6.51, N 12.78. 1H
NMR (D2O, 300 MHz, 298 K): d 2.37 (s, 3H, CH3), 2.41 (s, 3H,
CH3), 6.26 (s, 1H), 6.76 (d, 1H), 6.84 (d, 1H), 7.46 (s, 1H), 8.24
(s, 1H, HCOO) ppm.
Experimental
Materials and general comments
Starting materials and solvents such as m-phenylenediamine,
acetylacetone, triethylamine, acetic acid, formic acid, concen-
trated hydrogen chloride, benzoic acid, L-tartaric acid, methy-
lene chloride, dimethyl sulphone (DMSO) and ethanol (95%)
were commercially obtained and used as received. The elemental
analyses were performed on a Perkin-Elmer 2400 analyzer. 1H
NMR spectra were recorded on a Varian Mercury 300 MHz or a
Bruker ACF 500 MHz spectrometer. IR spectra were recorded
on a Nicolet Impact 410 FTIR spectrometer using KBr pellets.
UV-vis spectra were obtained on a Perkin-Elmer Lambda 20
spectrometer. Luminescence spectra were measured on a Perkin-
Elmer LS55 Luminescence spectrometer at room temperature.
7-Amino-2,4-dimethylquinolinium acetate (1?CH3COOH)
1?CH3COOH was synthesized by the same conditions and
procedures as for 1?HCOOH with acetic acid as a starting
material. 1?CH3COOH was obtained as yellow-green solid.
Yield: 0.39 g, 94%. Anal. Calcd for C13H16N2O2 (232.28): C
67.22, H 6.94, N 12.06; Found: C 67.30, H 6.88, N 12.15. 1H
NMR (CDCl3, 300 MHz, 298 K): d 2.10 (s, 3H, CH3COO), 2.60
(s, 3H, CH3), 2.73 (s, 3H, CH3), 6.89 (s, 1H), 6.93 (d, 1H), 7.41 (s,
1H), 7.73 (d, 1H) ppm.
7-Amino-2,4-dimethylquinolinium chloride (1?HCl)
To a solution of m-phenylenediamine (5.30 g, 49.0 mmol) in
30 mL of ethanol was added a mixture of concentrated HCl
(4.0 mL, 49.0 mmol) and acetylacetone (5.0 mL, 49.0 mmol) in
30 mL of ethanol at room temperature. The mixture was stirred
until a large amount of yellow solid precipitated. The solid was
collected by filtration, washed with ethanol and dried. Yield:
7.98 g, 78.0%. Anal. Calcd for C11H13N2Cl (208.69): C, 63.31; H,
6.28, N, 13.42. Found: C, 63.37; H, 6.25; N, 13.49. 1H NMR
(D2O, 300 MHz, 298 K): d 2.34 (s, 3H, CH3), 2.41(s, 3H, CH3),
2.57 (m, DMSO in crystal), 6.10 (s, 1H, 8-H), 6.69 (d, 1H, 6-H),
6.81 (s, 1H, 3-H), 7.37 (d, 1H, 5-H) ppm. IR (KBr, cm21): 3371
(m), 3306 (m), 3202 (s), 2908 (m), 2848 (m), 2739 (m), 1931 (w),
1842 (w), 1770 (w), 1641 (vs), 1594 (s), 1475 (m), 1448 (m), 1387
(m), 1245 (w), 1290 (w), 1199 (m), 1155 (w), 1056 (w), 1033 (m),
930 (m), 848 (m), 791 (w), 721 (w), 664 (w), 593 (w), 542 (w).
7-Amino-2,4-dimethylquinolinium benzonate (1?PhCOOH)
1?PhCOOH was synthesized by the same conditions and
procedures as for 1?HCOOH with benzoic acid as starting
material. 1?PhCOOH was obtained as brown-yellow solid. Yield:
0.49 g, 93%. Anal. Calcd for C18H18N2O2 (294.35): C 73.45, H
1
6.16, N 9.52; Found: C 73.38, H 6.20, N 9.46. H NMR (D2O,
300 MHz, 298 K): d 2.28 (s, 3H, CH3), 2.36 (s, 3H, CH3), 6.10 (s,
1H), 6.67 (d, J = 9.3 Hz, 1H), 6.72 (s, 1H), 7.18 (t, J = 6.9 Hz,
2H), 7.25 (d, J = 6.0 Hz, 1H), 7.32 (d, J = 9.0 Hz, 1H), 7.68 (d, J
= 8.1 Hz, 2H) ppm.
7-Amino-2,4-dimethylquinolinium L-tartarate (1?L-tartaric acid)
To a solution of 7-amino-2,4-dimethylquinoline (0.31 g, 1.80
mmol) in 10.0 mL of ethanol was added a solution of L-tartaric
acid (0.27 g, 1.80 mmol) in 8.0 mL of ethanol at room
temperature. The mixture was stirred until a large amount of
yellow solid precipitated. The solid was collected by filtration,
washed with ethanol and dried. Pure 1?L-tartaric acid was
obtained as yellow solid after recrystallization from ethanol.
Yield: 0.53 g, 91%. Anal. Calcd for C15H28N2O6 (322.31): C
55.90, H 5.63, N 8.69; Found: C 55.95, H 5.60, N 8.62. 1H NMR
(D2O, 300 MHz, 298 K): d 2.41 (s, 3H, CH3), 2.43 (s, 3H, CH3),
4.36 (s, 2H, CHOH), 6.14 (s, 1H), 6.70 (d, J = 9.0 Hz, 1H), 6.81
(s, 1H), 7.40 (d, J = 9.3 Hz, 1H) ppm.
7-Amino-2,4-dimethylquinoline (1)
To a solution of 1?HCl (3.13 g, 15.0 mmol) in 40 mL of water
was added a mixture of 40 mL of CH2Cl2 and 3.0 mL of NEt3.
The mixture was stirred at room temperature for 2 h. The
organic layer was separated and the aqueous layer was further
extracted with CH2Cl2 (3 6 10 mL). The combined organic
layers were dried over anhydrous MgSO4, filtered, and
concentrated in vacuo. The yellowish solid was collected by
filtration, washed with ethyl ether and dried. Yield: 1.70 g, 66%.
Anal. Calcd for C11H12N2 (172.23): C, 76.71; H, 7.02, N, 16.27.
Found: C, 76.68; H, 7.07; N, 16.21. 1H NMR (CDCl3, 500 MHz,
7276 | CrystEngComm, 2012, 14, 7275–7286
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… …
N2–H102 Cl1 and N4–H104 Cl1, respectively. Meanwhile, there
Single-crystal X-ray diffraction
are only four hydrogen bonds around Cl2 atom, being C22–
…
The single crystal X-ray diffraction data for compounds 1?HCl,
1?HCl?DMSO, 1?HOAc, 1?PhCOOH, and 1?L-tartaric acid?2H2O
were collected on a Rigaku R-AXIS RAPID IP diffractometer
equipped with graphite-monochromated Mo-Ka radiation (l =
…
…
…
H22C Cl2, N2–H101 Cl2, N3–H103 Cl2, N4–H105 Cl2,
respectively. The molecule A forms a 1-D infinite chain through
…
…
N1–H100 Cl1 and N2–H102 Cl1 hydrogen bonds. There are also
1
weak C7–H7 Cl1 interactions, which form a graph-set motif R2 (6)
…
˚
0.71073 A), operating at 293 ¡ 2 K. The structures were solved by
…
together with N2–H102 Cl1 hydrogen bonds. The adjacent quino-
direct method13 and refined by full-matrix least squares based on F2
using the SHELXTL 5.1 software package.14 All non-hydrogen
atoms were refined anisotropically. Unless otherwise noted,
hydrogen atoms were included in idealized position and were
allowed to ride. The details of crystallographic collection and
refinement data are given in Table 1. The hydrogen bonding
parameters are given in Table 2 and Table 3.
line rings in the p-stacking interactions are antiparallel with the
˚
centroid–centroid distances of 3.35 to 3.49 A (3.35/3.42 A for the
˚
˚
rings of molecule A; 3.46/3.49 A for the rings of molecule B). The 1-D
…
infinite chains were linked through C10–H10C Cl1 interactions
and p–p interactions with the adjacent quinoline rings to form a 2-D
layer structure (Fig. 2b). The molecule B forms a dimer through N3–
…
…
H103 Cl2 and N4–H105 Cl2 hydrogen bonds with a graph-set
2
…
motif R4 (16). The dimers were connected through C22–H22C Cl2
and p–p interactions into a ladder structure (Fig. 2c). The 2-D layer
structure and ladder structure were further linked through N4–
Results and discussion
Synthesis and characterization
…
…
…
…
H104 Cl1, C18–H18 Cl1, C21–H21C Cl1 and N2–H101 Cl2
interactions to form 3-D network (Fig. 2a).
7-Amino-2,4-dimethylquinoline hydrochloride (1?HCl) was
obtained by the reaction of m-phenylenediamine (MPD) with
acetylacetone (acac) in the presence of conc. HCl at room
temperature (see Scheme S1, ESI{). It has proved to be an
efficient and simple method for the high-yielding and large-scale
synthesis of 1?HCl. The alcoholic filtrate could be distilled and
recycled. The reaction for the preparation of 1?HCl was also
tested in DMF or methanol, but it was found that the yield is
lower than the one in ethanol. The reaction was also examined
with different molar ratios of acac/MPD/conc. HCl and 1?HCl
was always obtained when the molar ratio is 1 : 1 : 1, 2 : 1 : 1 or
1 : 2 : 1 in EtOH at room temperature. Compound 1 was
feasibly synthesized in higher yield by treatment of 1?HCl with
triethylamine in methylene chloride/water, which is a new
efficient method for the preparation of Compound 1.15
1?HCOOH, 1?CH3COOH, 1?PhCOOH and 1?L-tartaric acid
were obtained by the reaction of 7-amino-2,4-dimethylquinoline
with the corresponding acid in similar yields at room tempera-
In addition to 1?HCl, the 1?HCl solvates have been obtained in
the cocrystallization experiments. Moreover, the structure of the
1 : 1 solvate has revealed the interesting changes in the hydrogen
bonding patterns, resulting in the different three-dimensional
network. In the asymmetric unit of 1?HCl?DMSO, there is one
1?HCl molecule and one solvent DMSO molecule. In the packing
…
of the 1?HCl?DMSO (Fig. 3), there are N2–H2B Cl1 and
1
C8–H8 Cl1 interactions with the graph-set motif R2 (6). The
…
…
adjacent molecules were linked by the N1–H1 Cl1 hydrogen
bonds to form 1-D S-shape chain (Fig. 3b). The adjacent chains
formed the layer structure via the intermolecular p–p interaction
between adjacent quinoline rings with the separation distance of
2
3.32 A. The neighbouring DMSO molecules form cyclic R2 (8)
˚
…
dimer through C–H O hydrogen bonds, and the dimers were
…
further linked through C–H O hydrogen bonds to form 1-D
S-shape chain (Fig. 3c). The layer structure and the 1-D S-shape
chain formed by DMSO molecules were further linked into the
…
ture (see Scheme S2, ESI{). Compound 1 and 1?HCl,
1?HCOOH, 1?CH3COOH, 1?PhCOOH and 1?L-tartaric acid
1
were characterized by elemental analysis and H NMR.
final 3-D network through N2–H2A O1 hydrogen bonds.
The 1 : 1 organic salt of 7-amino-2,4-dimethylquinoline and
formic acid has been reported by our group12. A clearer packing
diagram is shown in Fig. 4. In the packing of 1?HCOOH, there exist
Structures of quinolinium compounds 1?HCl, 1?HCl?DMSO,
1?CH3COOH, 1?PhCOOH, 1?L-tartaric acid?2H2O
…
not only strong N–H O hydrogen bonds but also weak C–H
…
O
interactions. The quinolinium cations and formate anions form
…
The crystals of compounds 1?HCl?DMSO, 1?PhCOOH and 1?L-
tartaric acid?2H2O suitable for X-ray crystal structure determi-
nation were slowly grown from DMSO at room temperature.
The crystals of 1?HCl and 1?CH3COOH suitable for X-ray
crystal structure determination were slowly grown from EtOH at
room temperature. The structures of 1?HCl, 1?HCl?DMSO,
1?CH3COOH, 1?PhCOOH and 1?L-tartaric acid were deter-
mined by single crystal X-ray diffraction analysis. The ORTEP
drawings of molecule structures are shown in Fig. 1.
…
O
chains through strong N–H O hydrogen bonds and C–H
1
interactions with the graph-set motifs R2 (6) and R2 (8). Two other
2
…
N–H O hydrogen bonds link adjacent chains into a grid with a
4
rectangular cavity and a graph-set motif R4 (20) to form a 2-D
…
sheet. The adjacent sheets were linked through C11–H11C O2,
…
C11–H11B O1 and p–p interactions to form 3-D network.
7-Amino-2,4-dimethylquinolinium acetate crystallizes in the
orthorhombic space group Pbca. The asymmetric unit contains
one acetate and one 7-amino-2,4-dimethylquinolinium. In the
crystal packing diagram (Fig. 5), two acetate and two 7-amino-
2,4-dimethylquinolinium form a staircase-like dimmer through
7-Amino-2,4-dimethylquinolinium chloride crystallizes in the
¯
triclinic space group P1. The asymmetric unit of 1?HCl contains
two independent molecules A and B, and molecule A is shown in
…
…
four N–H O hydrogen bonds. The dimmer was further
…
Fig. 1. In the packing of 1?HCl (Fig. 2), there are N1–H Cl
…
stabilized by weak C–H
O interactions. Meanwhile, the
…
hydrogen bonds and weak C–H Cl hydrogen bonds. The Cl1 and
dimmers were linked by other N–H O hydrogen bonds and
…
Cl2 atoms have different hydrogen bonding environments. There are
…
C–H O interactions to form 3-D network. There also exist p–p
seven hydrogen bonds around Cl1 atom, being C7–H7 Cl1, C10–
…
…
…
…
H10C Cl1, C18–H18 Cl1, C21–H21C Cl1, N1–H100 Cl1,
interactions between the adjacent quinoline rings with the
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Table 2 Hydrogen-Bond Geometries for 1?HCl, 1?HCl?DMSO, 1?HCOOH and 1?CH3COOH
…
…
d(H A) (A)
…
d(D A) (A)
˚
d(D–H) (A)
˚
˚
Structure
D–H
A
,(DHA) (u)
1?HCla
C(7)–H(7) Cl(1)#1
C(10)–H(10C) Cl(1)#2
0.93
0.96
0.93
0.96
2.77
3.00
2.79
2.78
3.627(2)
3.943(3)
3.581(2)
3.691(3)
3.857(2)
3.0916(17)
3.402(3)
3.648(2)
3.142(2)
3.373(2)
3.514(2)
3.1007(19)
2.832(3)
3.267(3)
3.773(2)
3.463(4)
3.692(4)
2.660(2)
2.954(3)
2.908(2)
3.484(3)
3.343(3)
3.593(3)
3.622(3)
2.992(2)
2.930(2)
3.236(2)
2.607(2)
3.507(2)
3.334(2)
3.295(3)
3.527(3)
154.4
168.9
143.7
159.7
175.6
176(2)
166(2)
166(3)
176(2)
162(2)
151.5(19)
179(3)
176(3)
174(2)
140.4(17)
146.5
…
…
…
C(18)–H(18) Cl(1)#3
…
C(21)–H(21C) Cl(1)
…
C(22)–H(22C) Cl(2)#4
…
0.96
2.90
N(1)–H(100) Cl(1)#5
…
0.96(2)
0.90(3)
0.81(3)
0.89(3)
0.97(2)
0.90(3)
0.91(3)
0.91(3)
0.76(3)
0.92(2)
0.96
2.13(3)
2.52(3)
2.85(3)
2.25(3)
2.43(3)
2.70(3)
2.19(3)
1.92(3)
2.51(3)
3.01(2)
2.62
N(2)–H(101) Cl(2)#5
…
N(2)–H(102) Cl(1)#1
…
N(3)–H(103) Cl(2)#6
…
…
N(4)–H(104) Cl(1)#3
N(4)–H(105) Cl(2)#3
1?HCl?DMSOb
N(1)–H(1) Cl(1)#1
…
…
N(2)–H(2A) O(1)#1
…
…
N(2)–H(2B) Cl(1)
C(8)–H(8) Cl(1)
…
C(12)–H(12C) O(1)#2
…
…
C(13)–H(13C) O(1)#3
0.96
2.87
144.6
1?HCOOHc
N(1)–H(1) O(2)#1
0.99(3)
0.86
0.86
0.93
0.96
1.69(3)
2.13
2.08
2.56
2.64
167(2)
159.8
162.6
169.8
130.8
…
N(2)–H(2B) O(1)#2
…
N(2)–H(2A) O(1)#3
…
C(8)–H(8) O(2)#2
…
C(11)–H(11A) O(2)#1
…
…
C(11)–H(11C) O(2)#4
0.96
0.96
2.64
2.78
173.1
146.9
C(11)–H(11B) O(1)#5
1?CH3COOHd
N(2)–H(101) O(2)#1
0.93(3)
0.87(3)
1.04(2)
1.04(2)
0.93
0.93
0.96
0.96
2.14(3)
2.06(3)
2.58(2)
1.57(2)
2.74
2.69
2.61
2.63
152(2)
172(2)
120.7(15)
173(2)
140.4
127.4
128.5
155.5
…
…
N(2)–H(100) O(1)#2
…
N(1)–H(1) O(1)#3
…
N(1)–H(1) O(2)#3
…
C(2)–H(2) O(1)#4
…
…
C(8)–H(8) O(2)#3
C(10)–H(10C) O(1)#3
…
C(10)–H(10B) O(1)#4
a
b
#1 x, y + 1, z + 1; #2 2x, 2y, 2z + 1; #3 2x + 1, 2y, 2z + 1; #4 2x + 1, 2y + 1, 2z + 1; #5 x, y, z + 1; #6 x, y 2 1, z. #1 2x + 1/2, y +
c
1/2, 2z + 1/2; #2 2x + 1, 2y, 2z + 1 ; #3 2x, 2y, 2z + 1. #1 x, y, z 2 1 ; #2 x, y + 1, z 2 1 ; #3 2x, 2y + 2, 2z; #4 2x + 1, 2y + 1, 2z +
d
1; #5 2x, 2y + 1, 2z + 1. #1 2x + 1, 2y, 2z + 1; #2 x 2 1, 2y + 1/2, z + 1/2; #3 x 2 1, y, z.
…
Table 3 Hydrogen-Bond Geometries for 1?PhCOOH and 1?L-tartaric acid, together with C–H p interaction parameters for 1?PhCOOH
…
…
d(H A ) (A)
…
d(D A) (A)
˚
d(D–H) (A)
˚
˚
Structure
D–H
A
,(DHA) (u)
1?PhCOOHa
N(1)–H(100) O(2)#1
1.11(3)
0.94(2)
0.92(3)
0.86(3)
0.929
0.929
0.86(4)
0.93
0.97(3)
0.86(6)
0.76(4)
0.76(4)
1.15(3)
0.95(7)
0.82
0.82
0.93
0.96
0.96
0.96
0.98
0.94(6)
0.94(6)
0.93
1.56(3)
1.74(2)
2.01(3)
2.09(3)
2.828
2.829
3.24(3)
2.56
1.84(3)
2.00(6)
2.31(4)
2.22(4)
1.98(3)
2.31(7)
2.07
1.94
2.62
2.60
2.71
2.86
2.60
1.55(6)
2.63(5)
2.81
2.628(2)
2.657(2)
2.927(3)
2.940(3)
3.7452(31)
3.7464(26)
3.97(4)
161(2)
165(2)
177(3)
169(3)
169.342(181)
169.660(157)
146.171(251)
94.0
153(3)
165(5)
140(3)
148(4)
139(2)
130(6)
119.4
176.7
165.5
156.3
129.5
109.4
156.9
161(5)
130(4)
165.8
…
…
N(3)–H(101) O(4)
…
N(2)–H(103) O(1)#2
…
N(4)–H(105) O(3)#3
…
C(2)–H(2) Cg(1)
…
C(13)–H(13) Cg(2)#4
…
N(4)–H(105) Cg(1)#5
1?L-tartaric acidb
O(8)–H(106) O(4)
…
2.788(3)
2.743(4)
2.832(3)
2.930(3)
2.886(3)
2.943(6)
3.006(4)
2.576(3)
2.756(3)
3.533(4)
3.499(5)
3.405(4)
3.303(4)
3.526(4)
2.457(2)
3.307(3)
3.714(5)
3.338(6)
…
O(7)–H(104) O(8)#1
…
O(7)–H(103) O(1)#2
…
N(1)–H(102) O(3)#3
…
N(1)–H(102) O(1)#3
…
N(2)–H(101) O(7)#4
…
N(2)–H(100) O(5)#4
…
O(4)–H(4) O(6)
…
O(3)–H(3) O(7)
…
C(2)–H(2) O(2)#5
…
C(10)–H(10C) O(8)#2
…
C(10)–H(10B) O(4)
…
C(10)–H(10B) O(6)
…
…
C(13)–H(13) N(2)#6
O(2)–H(107) O(5)#7
…
O(2)–H(107) O(6)#7
…
C(7)–H(7) O(8)#8
…
C(11)–H(11C) O(6)#9
0.96
2.91
108.2
a
#1 2x + 1, y + 1/2, 2z + 1/2; #2 2x + 1, 2y, 2z + 1; #3 x, 2y + 3/2, z + 1/2 #4 x 2 1, y, z ; #5 2x + 1, 2y + 1, 2z + 1; Cg1 and Cg2 are
the centroids of the phenyl rings C23/C24/C25/C26/C27/C28 and C30/C31/C32/C33/C34/C35, respectively. #1 2x + 1, y 2 1/2, 2z + 1/2; #2 x 2
b
1, y, z; #3 2x + 1, y + 1/2, 2z + 1/2; #4 x, y + 1, z; #5 x 2 1/2, 2y + 1/2, 2z; #6 x, y 21, z ; #7 x + 1, y, z ; #8 x 2 1/2, 2y + 3/2, 2z; #9 2x
+ 1/2, 2y + 1, z 2 1/2.
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Fig. 1 Molecular structures of 1?HCl, 1?HCl?DMSO, 1?CH3COOH, 1?PhCOOH, 1?L-tartaric acid?2H2O; The thermal ellipsoids are drawn at 30%
probability levels.
Fig. 2 (a) Perspective view of crystal packing of 1?HCl; (b) the 2D layer structure formed by molecule A; (c) the ladder structure formed by molecule
B. The asymmetric unit contains two independent molecules A and B; the hydrogen bonds are indicated in yellow dashed lines.
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…
…
Fig. 3 (a) Perspective view of crystal packing of 1?HCl?DMSO; b) 1-D S-shape chain formed by N–H Cl and C–H Cl interactions; (c) the infinite
1-D chain formed by DMSO molecules. The hydrogen bonds are indicated in yellow dashed lines.
˚
separation distance of 3.24 and 3.68 A. The quinoline rings are
dimethylquinolinium benzoate in molecule B form an infinite
…
almost parallel with the dihedral angle of 2.8u.
1-D chain through N–H O hydrogen bonds. For molecular A,
…
the dimer units assemble to 3-D network through other N–H
O
7-Amino-2,4-dimethylquinolinium benzoate crystallizes in the
monoclinic space group P21/c. The asymmetric unit contains two
independent molecules A and B, shown in Fig. 1 (molecular A),
and Fig. S1, ESI,{ (molecular B). The dihedral angles between
the quinolinium ring and the corresponding phenyl ring of the
benzoate anion are 109.8u (molecule A) and 84.6u (molecule B),
hydrogen bonds. In the case of molecular B, the adjacent 1-D
…
chains further assemble into 3-D network through C–H
p
interactions (Fig. 6c). There also exist p–p interactions between
˚
two quinoline rings with the separation distance of 3.42 A
˚
(molecule A) and 3.39 A (molecule B), respectively. There exist
…
very weak N–H p interactions between the two 3-D networks
…
respectively. In molecule A, there are C–H p interactions
formed by molecules A and B, resulting in more complex
supramolecular networks.
between the C–H bond of quinolinium ring and the centroid of
the phenyl ring. Meanwhile, in molecule B, there are N3–
…
H101 O4 hydrogen bonds. In the packing of 1?PhCOOH
7-Amino-2,4-dimethylquinolinium tartarate dihydrate crystal-
lizes in the orthorhombic space group P212121, with one L-
tartarate anion, one 7-amino-2,4-dimethylquinolinium and two
water molecules in a crystallographically asymmetric unit. More
(Fig. 6), two adjacent 7-amino-2,4-dimethylquinolinium benzo-
…
ate in molecule A form a dimer through C–H p interactions
…
and N–H O hydrogen bonds (Fig. 6b), while 7-amino-2,4-
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…
Fig. 4 Perspective view of crystal packing of 1?HCOOH. (a) The 3-D network formed by 2-D sheets through intermolecular C11–H11C O2, C11–
…
H11B O1 and p–p interactions; (b) the 2-D sheet with intermolecular C–H O interactions and intermolecular N–H O hydrogen bonds. The
…
…
hydrogen bonds are indicated in yellow dashed lines.
…
Fig. 5 Perspective view of crystal packing of 1?CH3COOH. (a) The 3-D network formed by dimmers through intermolecular C–H O interactions,
…
intermolecular N–H O hydrogen bonds and p–p interactions; (b) the dimmer with intermolecular C–H O interactions and intermolecular N–H O
…
…
hydrogen bonds. The hydrogen bonds are indicated in yellow dashed lines.
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Fig. 6 Perspective view of crystal packing of 1?PhCOOH. (a) The complex 3-D structure formed by molecule A and molecule B; (b) the 3-D network
…
formed by molecule A through intermolecular C–H Cg1 interactions, intermolecular N–H O hydrogen bonds and p–p interactions; (c) the 3-D
…
…
network formed by molecule B through intermolecular N–H O hydrogen bonds, C–H Cg2 interactions and p–p interactions. The asymmetric unit
…
…
contains two independent molecules A and B. The hydrogen bonds and C–H p interactions are indicated in yellow dashed lines. The weak N–H
…
p
interactions are indicated in purple dashed lines. Cg1 and Cg2 are the centroids of the phenyl rings C23/C24/C25/C26/C27/C28 and C30/C31/C32/C33/
C34/C35, respectively and indicated in green ball.
recently, the intermolecular interactions of (L)-tartaric acid with
heteroaromatic amines have been observed in construction of
supramolecular architectures16 and in the use of non-linear
optical materials,17 where the crystal structures of a number of
1 : 1 salts have been determined, allowing a full comparison with
7-amino-2,4-dimethylquinolinium salt. The L-tartarate anion
forms a self-association of S(5) motif through an intramolecular
with other tartarate hydroxyl groups, as well as with the water
molecules has been described in the tartarate analogue.16 There
exist p–p interactions between the adjacent quinoline rings with
˚
the centroid–centroid distance of 3.53 and 3.59 A, stacking into a
column structure along a axis direction. The quinoline rings are
almost antiparallel to each other, with the dihedral angle of 2.2u.
The 3-D network and the column substructure of p-stacked
quinolinium cations were further linked together through
…
…
O4–H4 O6 hydrogen bond. The intermolecular O2–H107 O5
…
…
N–H O, C–H O and C–H N hydrogen bonds.
…
…
and O2–H107 O6 hydrogen bonds link the L-tartarate anions
in a head-to-tail fashion to an infinite chain along a-axis. The
adjacent chains were linked together with two water molecules
…
A comparison of the structures of quinolinium salts indicates
that the interesting supramolecular networks were dominated by
…
through O–H O hydrogen bonds to form 3-D honeycomb
the strong hydrogen bonding N–H O/Cl and much weaker
…
…
network (Fig. 7). A different three-dimensional hydrogen-
bonded honeycomb framework through carboxylate interactions
C–H N/Cl, C–H p and p–p assembling interactions, each
playing an important role in controlling their crystal packing.
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Fig. 7 Perspective view of crystal packing of 1?L-tartaric acid?2H2O. (a) the 3-D structure formed by quinoliniums, L-tartarate and water molecules
…
through N–H O, C–H O, C–H N, O–H O hydrogen bonds and p–p interactions (left: the 3-D structure; right: the column structure formed by
…
…
…
…
quinolinium through p–p interactions). (b) the 3-D network formed by L-tartarate and water molecules through O–H O hydrogen bonds (left: the 3-D
…
network; right: the infinite chain formed by the L-tartarate through the intermolecular O–H O hydrogen bonds). The hydrogen bonds are indicated in
yellow dashed lines.
Notably, the different packing structures are a result of the effect
of the anions. In 1?HCl, the Cl1 atom forms seven hydrogen
bonds to four C atoms and three N atoms, but Cl2 atom forms
four hydrogen bonds to a C atom and three N atoms. In
1?HCl?DMSO, the Cl atom forms three hydrogen bonds to two
N atoms and a C atom. For both chloride salts, the weak
interaction. In the L-HOOCCH(OH)CH(OH)COO2 salt, each
L-HOOCCH(OH)CH(OH)COO2 anion is located among three
quinolinium cations and form five hydrogen bonds, including two
…
…
…
N–H O, two C–H O and a C–H N contacts with the graph-set
motifs R21(6) and R22(7). Specifically, 1?HCl and 1?HCl?DMSO exhibit
…
1-D chain based on the interlinked quinolinium molecules by N–H Cl
…
…
C–H Cl interactions together with two N–H Cl hydrogen
1
hydrogen bonds. In the packing arrangement, the adjacent chain was
held together by p–p interactions between adjacent quinoline rings to
form the layer structure. In 1?HCl, the adjacent dimers with ring motif
bonds form rings of a graph-set motif R2 (6). In the HCOO2 and
CH3COO2 salts, each HCOO2 and CH3COO2 anions are
2
…
R4 (16) are further held together by C–H Cl and p–p interactions,
located among three quinolinium cations and form five hydrogen
…
…
bonds, including three N–H O and two C–H O contacts with
leading to formation of a ladder structure. Thus, the layer structure and
1
2
4
the graph-set motifs R2 (6), R2 (8), and R4 (20) for 1?HCOOH
…
…
ladder structure were interlinked through N–H Cl, C–H Cl
interactions to form the extending 3-D network structure. In the case
of 1?HCl?DMSO, the layer structure together with the 1-D S-shape
chain formed by DMSO molecules were further linked through
and motifs R2 (6) and R4 (12) for 1?CH3COOH. In the PhCOO2
1
2
salt, each PhCOO2 anion is located among three quinolinium cations
…
and form two hydrogen bonds being N–H O and a C–H
…
p
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…
N–H O hydrogen bonds to form the final 3-D network. In the
packing of 1?HCOOH, the adjacent sheets were linked together
…
through C–H O and p–p interactions to form 3-D network. In
…
1?CH3COOH, the dimmers were linked together through N–H O, C–
…
H
O and p–p interactions to form 3-D network. In the PhCOO2 salt,
…
the adjacent chains were held together by C–H p interactions to
assemble into 3-D network, and the dimmer units were linked together
…
through N–H O hydrogen bonds to form another 3-D network.
Furthermore, the two 3-D networks are linked together by weak
…
N–H p interactions to form more complex supramolecular networks.
In the L-HOOCCH(OH)CH(OH)COO2 salt, the infinite chains were
…
formed by O–H O hydrogen bonds between adjacent L-tartarate
anions in a head-to-tail fashion, which further linked together with two
…
water molecules through O–H O hydrogen bonds to form 3-D
honeycomb network. The 3-D network and the column substructure of
p-stacked quinolinium cations were further interlinked together through
…
…
…
N–H O, C–H O and C–H N hydrogen bonds, resulting in a novel
3-D network.
Fig. 9 Emission spectra of 1, 1?HCl, 1?HCOOH, 1?CH3COOH,
1?PhCOOH and 1?L-tartaric acid in EtOH solution.
Luminescent properties of compounds 1, 1?HCl, 1?HCOOH,
1?CH3COOH, 1?PhCOOH and 1?L-tartaric acid
and the quinolinium cations, in accordance with the other related
studies in the literature.18 A significant red shift of the emission
bands had been investigated in the phenanthrolinium salts in
comparison with those of 1,10-phenanthroline.19 Moreover, it
was revealed by the density functional theory (DFT) calculations
that the red shift emission is attributed to a decreased energy gap
between the highest occupied molecular orbital (HOMO) and
lowest unoccupied molecular orbital (LUMO) involved in the
CT transition.20 Interestingly, the solid-state emission spectra of
the quinolinium compounds are sensitive to the noncovalent
interactions.21 The hydrogen bonding N–H–O/Cl are involved in
interaction of quinolinium cation with anions, and further affect
energy levels of the excited states. It has also been reported that
the intermolecular hydrogen bonding can significantly tune the
energy levels and further influence the spectral properties of
hydrogen bond-mediated complexes.22 In this respect, the
hydrogen bond-mediated complexation of tartaric acid with
quinoline based receptors results in monomer emission quench-
ing followed by intramolecular excimer emission.23 In addition,
crystal structure analysis of quinolinium compounds showed
that the quinolinium moieties are involved in p–p stacking and
C–H–p interactions and they are also expected to induce the red-
shifted emission.20b,24
The photophysical properties of the quinoline compound 1 and
the corresponding salts 1?HCl, 1?HCOOH, 1?CH3COOH,
1?PhCOOH, and 1?L-tartaric acid were investigated by UV/vis
and photoluminescence (PL) spectroscopy in solutions and in the
solid state at room temperature. The obtained spectral data are
summarized in Supporting Information Table ST-1, ESI.{
The emission spectra of the quinolinium compounds in the
solid state are shown in Fig. 8, with strongly broadened
asymmetric emission bands compared to the observed emission
for the compound 1. All compounds produce bright fluorescence
in the solid state with emission maxima of 422, 534, 506, 484, 519
and 524 nm, respectively, with the red shift of about 62–112 nm
compared with the emission maximum of compound 1. The
fluorescent emissions of the quinolinium compounds can mainly
be assigned to the p–p* transitions of the aminoquinolinium
moieties and the charge-transfer (CT) transitions between anions
The typical emission spectra of the quinolinium compounds in
EtOH are also shown in Fig. 9. The solution photoluminescence
spectral maxima of the quinolinium salts are blue-shifted
compared with their solid-state emission spectra, similar to that
seen in previous observations.25 The red shift of the emission
maxima from solution to solid state is due to p–p stacking
interactions between the quinolinium aromatic rings in solid
state.
Conclusions
A
number of 7-amino-2,4-dimethylquinolinium salts with
different anions have been synthesized and characterized. The
structure analysis confirms that the nitrogen atoms in the
quinoline rings are protonated in all salts. The two solvates have
been obtained and thereby provide a useful complement to
Fig. 8 Emission spectra of 1, 1?HCl, 1?HCOOH, 1?CH3COOH,
1?PhCOOH and 1?L-tartaric acid in the solid state.
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Chemistry and Biology , Oxford University Press: Oxford, 1999.
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Nature, 2000, 407, 720; (b) N. Stanley, V. Sethuraman, P. T.
Muthiah, P. Luger and M. Weber, Cryst. Growth Des., 2002, 2, 631;
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13 G. M. Sheldrick, SHELXTL; PC Siemens Analytical X-ray
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cocrystal screening. All the quinolinium salts display interesting
three dimension supramolecular networks. The strong hydrogen
…
…
bonding N/O–H O and N–H Cl, together with weak C–
…
H
O/N/Cl hydrogen bonds become prominent in the construc-
tion of the observed supramolecular networks. Their crystal
…
packing is also stabilized by C/N–H p contacts and p–p
stacking interactions. The 7-amino-2,4-dimethylquinolinium
salts show strong luminescence in the solid state and organic
solution in the range 422–534 nm. The emission wavelength of
the salts can be tuned by changing the anion species. The solid-
state emission spectra of the quinolinium salts are highly
dependent on the nature of the stacking interactions. The results
also demonstrated that a family of quinolinium salts should be
considered as the promising candidates for potential solid-state
photofunctional materials.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Nos. 21004026 and 21074043). We are
also grateful for support by the Frontiers of Science and
Interdisciplinary Innovation Project of Jilin University (Nos.
450060445023 and 450060445027).
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