Syntheses, crystal structures, and photoluminescence properties of three bis-acylamide compounds

Article abstract of DOI:10.1002/zaac.201100233

Three bis-acylamide compounds, N¹,N⁴-bis(pyridin-4- yl)-cyclohexane-1, 4-dicarboxamide (L1), 1, 1′-(1, 3-phenylenedicarbonyl-) bis(1H-1, 2, 3-benzotriazole) (L2), and N¹,N⁴-bis(1H-1, 2, 4-triazole) phthalamide (L3) were synthesized. L1, L2, and a Cu^II complex based on L3 formulated as CuCl₂(L3)₂(en) ₂ (1) (en = ethylenediamine) were structurally characterized by single-crystal X-ray diffraction for the first time. L1, L2, and L3 exhibit different photoluminescence properties. Copyright

Full text of DOI:10.1002/zaac.201100233

ARTICLE
DOI: 10.1002/zaac.201100233
Syntheses, Crystal Structures, and Photoluminescence Properties of Three
Bis-acylamide Compounds
Tao Wu,[a] Yun Gong,*[a] Jianbo Qin,[a] Xiaoxia Wu,[a] and Rong Cao[b]
Keywords: Bis-acylamide; Synthesis; Crystal structure; Photoluminescence properties; Copper
Abstract. Three bis-acylamide compounds, N1,N4-bis(pyridin-4-yl)- on L3 formulated as CuCl2(L3)2(en)2 (1) (en = ethylenediamine) were
cyclohexane-1,4-dicarboxamide (L1), 1,1Ј-(1,3-phenylenedicarbonyl-) structurally characterized by single-crystal X-ray diffraction for the
bis(1H-1,2,3-benzotriazole) (L2), and N1,N4-bis(1H-1,2,4-triazole) first time. L1, L2, and L3 exhibit different photoluminescence proper-
phthalamide (L3) were synthesized. L1, L2, and a CuII complex based ties.
Introduction
One of the main goals of molecular electronics is the mas-
tery of intermolecular electron transfer over long distances.[1]
This requires the assembly of suitable molecular components
into an appropriate supramolecular structure.[2] Compounds
containing supramolecular functionalities such as acylamide
are useful in self-assembly because they usually give predicta-
ble patterns of hydrogen bonds, which can add extra dimen-
sionality.[3–10] Based on the situation, in an attempt to investi-
gate the relationship between the structure and photolumines-
cence property, herein we synthesized three bis-acylamide
compounds, N1,N4-bis(pyridin-4-yl)cyclohexane-1,4-dicarbox-
amide (L1), 1,1Ј-(1,3-phenylenedicarbonyl-)bis(1H-1,2,3-
benzotriazole) (L2), and N1,N4-bis(1H-1,2,4-triazole) phthala-
mide (L3). Among them, the syntheses of L1 and L3 were not
reported previously. As shown in Scheme 1, the three com-
pounds have different aromatic rings and different bridging
units, and all of them exhibit cis and trans conformations due
to the rotation of the flexible C–N single bonds in the struc-
tures. In the present work, L1, L2, and a CuII complex based
on L3 formulated as CuCl2(L3)2(en)2 (1) (en = ethylenedi-
amine) were structurally characterized by single-crystal X-ray
diffraction for the first time. The photoluminescence properties
of the three free compounds, L1, L2, and L3 were investi-
gated.
Scheme 1. The trans (above) and cis (below) conformations of L1 (a),
L2 (b), and L3 (c).
* Prof. Dr. Y. Gong
E-Mail: gongyun7211@cqu.edu.cn
[a] Department of Chemistry
College of Chemistry and Chemical Engineering
Chongqing University
Chongqing 400044, P. R. China
Results and Discussion
Crystal Structure and Photoluminescence Property of L1
[b] State Key Laboratory of Structural Chemistry
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
L1 crystallizes in the monoclinic space group P21/n with
half crystallographically independent L1 in the asymmetric
unit. As we know, 1,4-cyclohexanedicarboxylic acid (1,4-
H2chdc) has three kinds of conformations: e,a-cis, e,e-trans
Fuzhou, Fujian 350002, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201100233 or from the au-
thor.
438
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 638, (2), 438–442

Bis-acylamide Compounds
and a,a-trans, and the e,e-trans is the most stable conforma-
tion.[11] As described above, L1 is obtained by using H2chdc
as starting material. As shown in Figure 1a, the two substituent
groups of acylamide in the structure of L1 are in the stable
e,e-trans-positions. L1 exhibits a trans conformation (Fig-
ure 1a and Scheme 1a) and the two pyridyl rings of L1 are
parallel to each other. Strong intermolecular N–H···N hydrogen
bonds are observed in the structure of L1, and L1 shows a
three dimensional (3D) supramolecular architecture (Fig-
ure 1b). For example: H2–N2: 0.86 Å, H1···N1A: 2.161 Å,
N2···N1A: 2.979 Å, and N2–H2···N1A: 158.95° (Figure 1b)[12]
(atom with additional label A refers to the symmetry operation:
x–1/2, –y+3/2, z+1/2).
Figure 2. Solid-state emission spectra of L1, L2, L3 at room tempera-
ture.
Crystal Structure of L2
L2 crystallizes in the monoclinic space group P21/n, its
asymmetric unit contains one crystallographically independent
L2 molecule. As shown in Figure 3a, in the structure of L2
the phenyl ring and two benzotriazole rings are not coplanar.
The dihedral angles between the phenyl ring and two benzotri-
azole rings are 41.2 and 42.4°, respectively. The dihedral angle
between the two benzotriazole rings is 74.5°. L2 exhibits a
trans conformation (Figure 3a and Scheme 1b). Strong π···π
stacking interactions are observed in the structure of L2, for
example, plane 1 is constructed by C15, C16, C17, C18, C19,
C20, and plane 2 is constructed by C15B, C20B, N4B, N5B,
N6B (atom with additional label B refers to the symmetry op-
eration: B 2–x, 2–y, 1–z), the centroid-centroid and perpendicu-
lar distances between planes 1 and 2 are 3.821 and 3.485 Å,
respectively (Figure 3b). Different L2 molecules are linked by
π···π stacking interactions to form a 3D supramolecular archi-
tecture (Figure 3b).
The emission spectrum of L2 (slit width = 5 nm) is shown
in Figure 2. L2 exhibits an intense emission peak at 503 nm
and a shoulder peak at 453 nm (λex = 370 nm), which may be
attributable to the πǞπ* or nǞπ* electron transitions of
L2.[13] In the structure of L2, the phenyl ring and benzotriazole
rings are aromatic, and benzotriazole ring has more π-ex-
panded system than the pyridyl ring in the structure of L1, so
the emission of L2 is much stronger than that of L1 (Figure 2).
Figure 1. ORTEP view of L1 with the ellipsoids drawn at the 50%
probability (hydrogen atoms omitted for clarity) (a); Strong intermo-
lecular N–H···N hydrogen bonds indicated by dashed lines in the struc-
ture of L1 (b).
The photoluminescence property of L1 in the solid state at
room temperature was investigated. The emission spectrum of
L1 (slit width = 5 nm) is shown in Figure 2. L1 exhibits one
emission peak at 461 nm upon excitation at 360 nm, which
may be attributable to the intra-ligand electron transitions, such
as πǞπ*, nǞπ* transitions.[13]
Crystal Structure of CuCl2(L3)2(en)2 (1)
When the benzotriazole ring in the structure of L2 is re-
placed by the triazolyl ring, and the 1,3-substituted position of
As described above, in the structure of L1, the two pyridyl the bridged phenyl ring is changed to be a 1,4-position, we got
rings are bridged by the nonaromatic cyclohexane ring. If the compound L3. We fail to obtain the crystals of L3 for single-
nonaromatic cyclohexane ring is replaced by the aromatic crystal X-ray analysis, but a CuII complex based on L3 is ob-
phenyl ring, and the pyridyl ring is replaced by the benzotri- tained instead. Complex 1 crystallizes in the triclinic space
¯
azole ring, it is expected the emission intensity can be im- group P1, its asymmetric unit contains one L3, one en, half
proved. In order to prove the expectation, we synthesized com- CuII, and two half uncoordinated Cl–. As shown in Figure 4a,
pound L2.
Cu(1) exhibits a slightly distorted octahedral coordination ar-
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Z. Anorg. Allg. Chem. 2012, 438–442

T. Wu, Y. Gong, J. Qin, X. Wu, R. Cao
ARTICLE
Figure 4. ORTEP view of 1 with the ellipsoids drawn at the 50%
probability (hydrogen atoms omitted for clarity) (a); 3D supramolec-
ular architecture of 1 with the strong hydrogen bond interactions indi-
cated by dashed lines (b).
corded as KBr pellets with a PerkinElmer spectrometer. C, H, N ele-
mental analyses were performed with an Elementar Vario MICRO E
III analyzer. Solid-state photoluminescence spectra of all the com-
pounds were measured at room temperature with an Edinburgh
FLS920 fluorescence spectrometer. The instrument is equipped with
an Edinburgh Xe900 xenon arc lamp as the exciting light source.
Figure 3. ORTEP view of L2 with the ellipsoids drawn at the 50%
probability (a); Strong intermolecular π···π stacking interaction indi-
cated by dashed line in the structure of L2 (b).
rangement, defined by two nitrogen atoms from two triazolyl
of two L3 in the apical positions and four nitrogen atoms from
two en in the equatorial positions [Cu–N 2.011(2)–2.561(3) Å] Synthesis of L1: The synthetic routine for L1 is shown in Scheme 2a.
A mixture of cyclohexane-1,4-dicarboxylic acid (0.04 mol, 6.88 g) and
thionyl chloride (150 mL) was heated under reflux for 3 h. After com-
pletion of the reaction, the excess thionyl chloride was removed under
reduced pressure. The yellow residue was washed with benzene
(3ϫ15 mL), followed by the addition of CH2Cl2 (250 mL), pyridin-
4-amine (0.04 mol, 3.76 g), and pyridine (4.9 mL). The mixture was
stirred overnight at room temperature, and heated at 50 °C for 5 h.
After removing the solvent under reduced pressure, the residue was
washed with CH2Cl2 (2ϫ10 mL), H2O (5ϫ10 mL), NaHCO3
(3ϫ10 mL, 1%), and H2O (3ϫ10 mL) and finally dried at 80°C in
(Figure 4a and Table S1, Supporting Information). L3 exhibits
a cis conformation in the structure of complex 1 (Figure 4a
and Scheme 1c). Strong hydrogen bond interactions are ob-
served in complex 1 and it exhibits a 3D supramolecular archi-
tecture (Figure 4b and Table 1).
As for the free L3 ligand, it exhibits one intense emission
peak at 474 nm (λex = 360 nm, slit width = 5 nm), which may
be attributable to the πǞπ*, nǞπ* electron transitions of
L3.[13] The emission is stronger than that of L1 due to the
aromatic phenyl ring and triazolyl ring in the structure of L3. vacuo to give L1 as a white solid. Yield ca. 44% based on cicyclohex-
ane-1,4-dicarboxylic acid. Colorless strip crystals of L1 were obtained
when recrystallized from N,N-dimethylacetamide (DMA). Elemental
data for C18H20N4O2: calcd. C 66.65; H 6.21; N 17.27%; found: C
66.71; H 6.18; N 17.23%. IR (KBr): ν˜ = 1699 (s), 1598 (s), 1516 (s),
1454 (w), 1419 (w), 1383 (m), 1343 (m), 1298 (m), 1167 (s), 997 (m),
935 (m), 907 (w), 833 s), 586 (m), 539 (m) cm–1.
The benzotriazole ring in the structure of L2 has more ex-
panded π system than the triazolyl ring in the structure of L3,
as a result, the emission of L3 is weaker than that of L2.
Conclusions
Synthesis of L2: The synthetic routine for L2 is shown in
Three bis-acylamide compounds, L1, L2, and L3 were syn-
thesized. L1, L2, and a CuII complex based on L3 were struc-
turally characterized by single-crystal X-ray diffraction for the
first time. L1, L2, and L3 exhibit different photoluminescence
properties due to different aromatic rings and bridging units in
the structures.
Scheme 2b.[14]
A mixture of isophthaloyl dichloride (0.05 mol,
10.15 g) and 1H-1,2,3-benzotriazole (0.1 mol,11.9 g) in pyridine
(50 mL) was heated at 120 °C for 10 h. After cooling to room tempera-
ture, the white precipitate was filtered off, and washed with CH2Cl2
(50 mL) and water (3ϫ50 mL) to yield crude L2. Yield ca. 57% based
on 1H-1,2,3-benzotriazole. Colorless prismatic crystals were obtained
when recrystallized from acetonitrile/acetone solution (1:1 v/v). Ele-
mental data for C20H12N6O2: calcd. C 65.21; H 3.28; N 22.82%;
found: C 65.27; H 3.24; N 22.77%. IR (KBr): ν˜ = 3375 (w), 3083
(m), 1697 (s), 1603 (s), 1486 (m), 1451 (m), 1374 (s), 1211 (s), 1047
(s), 973 (s), 878 (m), 758 (s), 635 (m), 590 (w), 472 (w) cm–1.
Experimental Section
Material Required and Instrumentation: All chemicals were of rea-
gent grade and used without further purication. IR spectra were re-
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 438–442

Bis-acylamide Compounds
Table 1. Distances /Å and angles /° involving selected hydrogen bonds for complex 1.
A
H
B
B–H distance
A···B distance
H···A distance
B–H···A
Cl(1A)
O(1B)
O(2C)
Cl(2C)
N(3)
H(8)
H(4)
N(8)
N(4)
N(9)
N(9)
N(10)
N(10)
N(10)
0.86
0.86
0.90
0.90
0.90
0.90
0.90
2.928
2.753
2.945
3.066
3.134
3.277
3.103
2.169
1.963
2.227
2.236
2.439
2.634
2.327
147.01
152.20
136.40
153.20
134.23
129.14
144.41
H(92)
H(91)
H(101)
H(101)
H(102)
N(5A)
Cl(2B)
Symmetry transformations used to generate equivalent atoms: A –x, –y+1, –z+1; B x+1, y, z; C –x+1, –y+1, –z.
4H-1,2,4-triazol-4-amine (0.2 mol, 16.8 g) in pyridine (100 mL) was
heated at 120 °C for 10 h. After cooling to room temperature, the white
precipitate was filtered off, washed with CH2Cl2 (3ϫ30 mL), CH3OH
(2ϫ25 mL), H2O (3ϫ10 mL) and finally dried at 80 °C in vacuo to
give L3. Yield ca. 44% based on terephthaloyl dichloride. Elemental
data for C12H10N8O2: calcd. C 48.32; H 3.38; N 37.57%; found: C
48.43; H 3.41; N 37.52%. IR (KBr): ν˜ = 3381 (w), 3168 (m), 3111
(m), 3077 (m), 3026 (w), 2928 (s), 2814 (s), 1694 (s), 1569 (s), 1524
(w), 1463 (m), 1384 (s), 1323 (s), 1278 (s), 1201 (s), 1211 (w), 1107
(s), 1073 (s), 1020 (w), 978 (m), 948 (m), 888 (s), 859 (w), 736 (m),
681 (w), 649 (m), 617 (s), 544 (w) cm–1.
Synthesis of CuCl2(L3)2(en)2 (1): CuCl2·2H2O (0.1 mmol, 0.017g)
and ethylenediamine (0.3 mmol, 0.02 mL) were dissolved in H2O
(8 mL), afterwards the mixture was carefully layered on a aqueous
solution (2 mL) of L3 (0.1 mmol, 0.030 g) and NH3·H2O (0.5 mmol,
0.02 mL). Upon slow evaporation at room temperature for several
days, blue prismatic crystals of complex 1 were filtered off and washed
with water. Elemental data for C28H28Cl2CuN20O4: calcd. C 39.85; H
3.32; N 33.21%; found: C 39.90; H 3.35; N 33.30%.
X-ray Crystallography: Single-crystal X-ray data for L1, L2, and
complex 1 were collected with an Oxford XCalibur Eos diffractometer
using graphite monochromated Mo-Kα (λ = 0.71073 Å) radiation at
room temperature. Empirical absorption correction was applied. The
Scheme 2. The synthetic routines for compounds L1–L3.
Synthesis of L3: The synthetic routine for L3 is shown in Scheme 2c. structures were solved by direct methods and refined by the full-matrix
4H-1,2,4-triazol-4-amine was prepared according to the literature least-squares methods on F2 using the SHELXTL-97 software.[16] All
method.[15] A mixture of terephthaloyl dichloride (0.1 mol, 20.3 g) and non-hydrogen atoms were refined anisotropically. Hydrogen atoms of
Table 2. Crystal data and structure refinements for L1, L2, and complex 1.
L1
L2
1
Empirical formula
M
Crystal system
Space group
C18H20N4O2
324.38
monoclinic
P21/n
C20H12N6O2
368.36
monoclinic
P21/n
C28H36Cl2CuN20O4
851.22
triclinic
¯
P1
a /Å
b /Å
c /Å
α /°
5.7275(5)
16.0459(1)
8.8893(8)
90
102.238(9)
90
798.39(2)
2
1.349
3102
1412
344
1.036
7.561(4)
29.585(2)
8.467(5)
90
114.750(5)
90
1720.0(2)
4
1.422
3014
2675
760
1.274
7.882(3)
9.131(4)
13.732(6)
84.721(1)
77.358(1)
75.745(1)
933.9(7)
1
1.514
5970
3138
439
β /°
γ /°
V /Å3
Z
Dcalcd /g·cm–3
No. of unique reflcns
reflections used [I Ͼ 2σ(I)]
F(000)
Goodness-of-fit on F2
R1
1.054
0.0437
0.1143
a)
0.0409
0.0722
0.0735
0.1425
a)
wR2
2
2 2
2 2 1/2.
a) R1 = Σ||F0|–|Fc||/Σ|F0|; wR2 = Σ[w(F0 –Fc ) ]/Σ[w(Fo ) ]
Z. Anorg. Allg. Chem. 2012, 438–442
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
441

T. Wu, Y. Gong, J. Qin, X. Wu, R. Cao
ARTICLE
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L2 were located in the Fourier difference maps. All of the other hydro-
gen atoms were placed in the calculated positions. The crystal data
and structure refinements for L1, L2, and complex 1 are summarized
in Table 2. Selected bond lengths and angles for the ligands and the
complex are listed in Table S1 (Supporting Information).
Crystallographic data (excluding structure factors) for the structures
in this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-822077 (L1), CCDC-822078 (L2), and CCDC-767851
(1) (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk)
Supporting Information (see footnote on the first page of this article):
Selected bond lengths /Å and angles /° for L1, L2, and 1.
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Acknowledgement
Financial support from the Chongqing University Postgraduate Science
(No. CDJXS10221143 and No. 200911A1B0010317), the sharing fund
of Chongqing University’s large-scale equipment (No. 2011063001),
Natural Science Foundation Project of Chongqing (No. CSTC
2011jjA50017) and the Fundamental Research Funds for the Central
Universities (No. CDJZR10 22 00 09) are gratefully acknowledged.
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Received: May 21, 2011
Published Online: December 19, 2011
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Z. Anorg. Allg. Chem. 2012, 438–442