Synthesis, crystal structures, and photoluminescent properties of bis(pyrazol-1-yl)methane derivative and Zn(II) halide complexes (ZnLX2, X=Cl, Br, I)

Article abstract of DOI:10.1080/15533174.2013.841230

A novel bis(pyrazol-1-yl)methane derivative 9-(4-(di(1H-pyrazol-1-yl) -methyl) phenyl)-9H-carbazole (L) and its zinc halide complexes (ZnLX₂, X = Cl (1), Br (2), and I (3)) were prepared and fully characterized. The structures of the ligand (L) and complexes 2 and 3 were also characterized by single-crystal X-ray diffraction analysis. The results reveal that the central zinc(II) atom in the complexes is coordinated by two nitrogen atoms from ligands (L) and two halide anion forming a distorted tetrahedron coordination geometry. And then the hydrogen bonding interactions between the molecules from 1D to 3D supramolecular structures were investigated. Furthermore, the photophysical properties of the complexes 1-3 and L were investigated both experimentally and theoretically. The experimental results are consistent with that of the theoretical calculation.

Full text of DOI:10.1080/15533174.2013.841230

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Synthesis, Crystal Structures, and Photoluminescent
Properties of Bis(pyrazol-1-yl)methane Derivative and
Zn(II) Halide Complexes (ZnLX2, X˭Cl, Br, I)
Shi-Chao Wanga, Yan-Can Zhanga, Feng Jina, Wan-Ding Liua, Hong-Ping Zhoua, Jie-Ying Wua &
Yu-Peng Tianab
a Department of Chemistry, Anhui University and Key Laboratory of Functional Inorganic
Materials Chemistry of Anhui Province, Hefei, P.R. China
b State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, P.R. China
Accepted author version posted online: 09 Oct 2014.Published online: 01 Dec 2014.
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To cite this article: Shi-Chao Wang, Yan-Can Zhang, Feng Jin, Wan-Ding Liu, Hong-Ping Zhou, Jie-Ying Wu & Yu-Peng Tian
(2015) Synthesis, Crystal Structures, and Photoluminescent Properties of Bis(pyrazol-1-yl)methane Derivative and Zn(II) Halide
Complexes (ZnLX2, X˭Cl, Br, I), Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 45:5, 639-647,
DOI: 10.1080/15533174.2013.841230
To link to this article: http://dx.doi.org/10.1080/15533174.2013.841230
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry (2015) 45, 639–647
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.841230
Synthesis, Crystal Structures, and Photoluminescent
Properties of Bis(pyrazol-1-yl)methane Derivative
and Zn(II) Halide Complexes (ZnLX2, XHCl, Br, I)
SHI-CHAO WANG1, YAN-YAN ZHANG1, FENG JIN1, WAN-DING LIU1, HONG-PING ZHOU1,
JIE-YING WU1, and YU-PENG TIAN1,2
1Department of Chemistry, Anhui University and Key Laboratory of Functional Inorganic Materials Chemistry of Anhui Province,
Hefei, P.R. China
2State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, P.R. China
Received 12 July 2013; accepted 1 September 2013
A novel bis(pyrazol-1-yl)methane derivative 9-(4-(di(1H-pyrazol-1-yl) -methyl) phenyl)-9H-carbazole (L) and its zinc halide
complexes (ZnLX2, X D Cl (1), Br (2), and I (3)) were prepared and fully characterized. The structures of the ligand (L) and
complexes 2 and 3 were also characterized by single-crystal X-ray diffraction analysis. The results reveal that the central zinc(II)
atom in the complexes is coordinated by two nitrogen atoms from ligands (L) and two halide anion forming a distorted tetrahedron
coordination geometry. And then the hydrogen bonding interactions between the molecules from 1D to 3D supramolecular
structures were investigated. Furthermore, the photophysical properties of the complexes 1–3 and L were investigated both
experimentally and theoretically. The experimental results are consistent with that of the theoretical calculation.
Keywords: bis(pyrazol-1-yl)methanes, zinc (II) complex, crystal structure, optical properties
Introduction
More work has been focused on the weak noncovalent forces
in the design and synthesis of supramolecular structures.
The coordination chemistry of bis/poly[(pyrazolyl)methane] Here we report bis(pyrazol-1-yl)methanes derivatives 9-(4-(di
has made significant progress during the past few years[1–9] (1H-pyrazol-1-yl)-methyl)phenyl)-9H-carbazole (L) and its
not only because of their wide range of attractive applica- zinc(II) complexes: ZnLBr2 (2) and ZnLI2 (3). In the solid
tions, particular in catalysis and magnetism,[10–17] but also state, each compound shows extensive noncovalent interac-
because of their interesting structural diversity.[18–25] One of tions, including weak hydrogen bonds and C¢¢¢H¢¢¢p interac-
the current interesting topics is to rationally design and syn- tions that organize the molecules into 3D structure. We have
thesize supramolecular structures based on bis/poly[(pyra- found that these interactions are common not only in the
zolyl)methane] units, which are capable of multiple binding present compounds but also in a large number of known poly
modes and that also have the potential to participate in (pyrazolyl)borate and –methane compounds.[27,28,40]
important noncovalent interactions that direct their self-
assembly into remarkable architectures.[26–31]
Compared with coordination bonds, the non-covalent
forces are weaker, but they are common and play critical
Experimental
roles in forming the supramolecular structures due to their
Measurements and Methods
significant contribution to the self-assembly process.[32–39]
All chemicals used were of analytical grade. The solvents
were purified by conventional methods before use. 4-(9H-car-
bazol-9-yl)benzaldehyde was synthesized according to the lit-
erature.[41] Elemental analyses were performed with a Perkin
Elmer 240B instrument. Mass spectra were determined with
a Micro-mass GCT-MS (EI source). IR spectra were
recorded on NEXUS 870 (Nicolet) spectrophotometer in the
4000–400 cm¡1 region with samples prepared as KBr pellets.
1H and 13C NMR spectra were obtained on a Bruker Avance
400 MHz spectrometer (TMS as internal standard in NMR).
Address correspondence to Jie-Ying Wu, Department of Chem-
istry, Anhui University and Key Laboratory of Functional
Inorganic Materials Chemistry of Anhui Province, 230601 Hefei,
P.R. China. E-mail: jywu1957@163.com
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lsrt.

640
Wang et al.
Melting points were recorded with a Perkin–Elmer Pris-1 Crystal Structure Determination and Refinement
DMDA-V1 analyzer under N2 at a heating rate of
The crystallographic data for L and complexes (2, 3) was col-
5ꢀC¢min¡1
.
lected on a Bruker Smart 1000 CCD area detector diffrac-
ꢀ
UV–vis absorption spectra were recorded on UV-265 spec-
trophotometer. Fluorescence measurements were performed
using a Hitachi F-7000 fluorescence spectrophotometer.
tometer equipped with Mo Ka (λ D 0.71073 A) radiation
using v-scan mode. Empirical absorption correction was
applied to the data. Unit cell dimensions were obtained with
least-squares refinements, and all structures were solved by
direct methods with SHELXL–97. All non-hydrogen atoms
were located from the trial structure and then refined aniso-
tropically. All hydrogen atoms were generated in idealized
positions. All calculations were performed with SHELXL -97
programs.[43] Details of the crystal parameters, data collec-
tions and refinements are listed in Table 1, and selected bond
distances and angles are given in Table 2.
The fluorescence quantum yields (F)
The fluorescence quantum yields (F) were determined by
using fluorescein as the reference according to the literature
method.[42] Quantum yields were corrected as follows:
ꢀ
ꢁ
Arh2s Ds
Ash2r Dr
Fs D Fr
Computational Details
Where the s and r indices designate the sample and reference
samples, respectively; A is the absorbance at λexc; h is the
average refractive index of the appropriate solution; and D is
the integrated area under the corrected emission spectrum.
All calculations, including optimizations and TD-density
functional theory (TD-DFT) calculations were conducted
based on Gauss03 program.[44] Optimizations were carried
out with BP86[6–31G(d)] without any symmetry restraints,
and the TD-DFT calculations were performed on the opti-
mized structure. Quantum chemical calculations of L based
Fluorescence lifetime
For time-resolved fluorescence measurements, the fluores- on density functional theory[45] was performed at the BP86/
cence signals were collimated and focused onto the entrance 6–31G(d) level and calculations of complex 1–3 was carried
slit of a monochromator with the output plane equipped with out with BP86/6–31G(d) for C H N Cl Br I atoms and the
a photomultiplier tube (HORIBA HuoroMax-4P). The LAN12DZ basis set for the Zn atoms, which were
decays were analyzed by ‘least-squares’. The quality of the downloaded from the EMSL basis set library. In the calcula-
exponential fits was evaluated by the goodness of fit (x2).
tion of the absorption spectrum, the 25 lowest spin-allowed
Table 1. Crystal data and structure refinement for L and complexes 2–3
Compound
L
2
3
Empirical formula
Formula weight
C
25 H19 N5
389.45
C25H19Br2N5Zn
614.64
C25 H19 I2 N5 Zn
708.62
Temperature[K]
298(2)
298(2)
298(2)
ꢀ
Wavelength[A]
Crystal system
0.71069
Monoclinic
P21
0.71069
Triclinic
P ı
0.71069
Triclinic
P ı
space group
ꢀ
a [A]
7.026(5)
7.939(5)
35.471(5)
90.000(5)
91.133(5)
90.000(5)
1978.2(19)
4
7.870(5)
12.741(5)
14.582(5)
64.308(5)
76.560(5)
74.928(5)
1260.2(10)
2
8.107(5)
12.538(5)
14.424(5)
66.244(5)
76.952(5)
72.981(5)
1273.4(10)
2
ꢀ
b [A]
ꢀ
c [A]
a [ꢀ]
b [ꢀ]
g [ꢀ]
ꢀ
Volume [A 3]
Z
DCalcd [g/cm3]
F(000)
1.308
816
1.620
608
1.848
680
Crystal size [mm]
Reflections collected
Unique reflections
parameters
0.10 £ 0.10 £ 0.10
0.30 £ 0.20 £ 0.20
0.30 £ 0.20 £ 0.20
13929
8950
9076
6572
541
1.018
0.0456
4397
298
1.063
0.0399
4429
298
0.930
0.0301
GOF on F2
R1 a [I > 2s (I)]
wR2 b [I > 2s (I)]
0.1309
0.1352
0.1090
ꢀ
Drmin/ max [e.A¡3
]
0.135/–0.209
1.426/–0.991
1.385/–1.030
aR1 D SkFoj - jFck/SjFoj; b wR2 D [Sw(Fo2 – Fc2)2/Sw(Fo2)2]1/2
.

Synthesis, Crystal Structures, and Photoluminescent Properties of Bis(pyrazol-1-yl)methane Derivative
641
ꢀ
Table 2. Selected bond distances (A) and angles (ꢀ) for L and
complexes 2–3
L
Bond lengths
C(16)-C(19)
N(4)-C(19)
1.523(3)
1.451(3)
N(2)-C(19)
1.455(3)
Bond angles
N(2)-C(19)-C(16)
N(4)-C(19)-N(2)
112.1(2) N(4)-C(19)-C(16) 111.9(2)
110.7(2)
Complex 2
Bond lengths
Zn(1)-N(3)
Zn(1)-Br(1)
2.071(4)
2.364(9)
Zn(1)-N(5)
Zn(1)-Br(2)
2.064(3)
2.353(10)
Sch. 1. Synthetic route for ligand L and its complexes 1–3.
Bond angles
N(5)-Zn(1)-N(3)
N(3)-Zn(1)-Br(2)
N(3)-Zn(1)-Br(1)
N(4)-C(19)-N(2)
89.29(14) N(5)-Zn(1)-Br(2) 114.0(9)
120.4(10) N(5)-Zn(1)-Br(1) 108.0(10)
109.6(10) Br(2)-Zn(1)-Br(1) 112.9(4)
110.6(3)
SOCl2 (2.91 g, 24.00 mmol) was added dropwise at room
temperature, there was some pale-yellow suspension
(Scheme 1).
4-(9H-carbazol-9-yl)benzaldehyde
(1.30 g,
4.80 mmol) and CoCl2 anhydrous (0.24 g, 1.85 mmol) were
then added. After the reaction mixture was refluxed for about
15 h, then cooled to room temperature and diluted with
water (60 mL). The mixture was extracted with CH2Cl2 (4 £
80 mL) and dried over MgSO4. The solvent CH2Cl2 was
removed under reduced pressure to give a yellow solid. The
crude product was purified by column chromatography on
silica gel with petroleum ether/ethyl acetate (15:1) as eluent
to give pale yellow powder (1.08 g, 58%). Mp: 181ꢀC. IR
(KBr, cm¡1): 3104(w), 3044(w), 1600(s), 1513(s), 1450(s),
1225(s), 1089(m), 1045(m), 967(w), 797(m), 753(s), 725(m),
615(w). 1H NMR (400 MHz, (CD3)2SO): d ppm: 8.26 (s,
Complex 3
Bond lengths
Zn(1)¡N(3)
Zn(1)¡I(1)
Bond angles
2.057(3)
2.550(9)
Zn(1)¡N(5)
Zn(1)¡I(2)
2.050(4)
2.533(9)
N(5) ¡Zn(1)¡N(3) 88.74(14) N(5)¡Zn(1)¡I(2) 120.7(11)
N(3)¡Zn(1)¡I(2)
N(3)¡Zn(1)¡I(1)
115.1(10) N(5)¡Zn(1)¡I(1) 109.1(11)
108.3(11) I(1)¡Zn(1)¡I(2) 112.3(4)
N(4)¡C(19)¡N(2) 110.2(3)
singlet–singlet transitions, up to energy of about 5 eV, were 2H), 8.24 (s, 1H), 8.00–7.99 (d, J D 0.4 Hz, 2H), 7.70–7.67
taken into account (Table 3).
(m, 4H), 7.44–7.42 (m, 4H), 7.35–7.28 (m, 4H, ArH), 6.43 (s,
2H); 13C NMR (125 MHz, (CD3)2SO): d (ppm) D 140.3,
139.8, 137.3, 136.0, 130.6，128.8, 126.6, 126.3, 122.8, 120.5,
120.2, 109.7, 106.4, 75.8; MS (ESI): m/z, 412.15 ([MCNa]C),
801.32 ([2MCNa]C).
Preparation of L and Their Complexes
Synthesis of 9-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-9H-
carbazole (L) [41]
Under nitrogen atmosphere, a solution of NaH (1.15 g,
48.00 mmol) in THF (80 mL) was stirred, and subsequently
pyrazole (3.27 g, 48.00 mmol) in THF (20 mL) was added
dropwise. The mixture was stirred for 30 min at 0ꢀC. Then
Synthesis of complexes 1, 2, and 3
L (0.39 g, 1 mmol) and ZnCl2 (0.14 g, 1 mmol) were dis-
solved in diethyl ether (30 mL). The mixture was stirred
under reflux for 3 h, then white precipitation produced. The
solution was filtered to afford the targeting complex as white
powder (0.40 g, 77%). Mp > 300ꢀC. Anal. Calcd. for
C25H19Cl2N5Zn: C, 57.11; H, 3.64; Cl, 13.49; N, 13.32; Zn,
12.44%; Found: C, 57.23; H, 3.63; N, 13.38%; IR (KBr,
cm¡1): 3120(w), 2970(w), 1602(m), 1517(s), 1452(s), 1407(m),
1293(m), 1231(m), 1068(m), 994(w), 753(s), 724(m), 609(w).
A similar procedure was also adopted for complex 2 and
complex 3. Complex 2: Mp > 300ꢀC. Anal. Calcd. for
C25H19Br2N5Zn: C, 48.85; H, 3.12; Br, 26.00; N, 11.39; Zn,
10.64%; Found: C, 48.93; H, 3.13; N, 11.35%; IR (KBr,
cm¡1): 3120(w), 2970(w), 1603(w), 1517(s), 1452(s), 1406(s),
1232(m), 1068(s), 800(m), 778(s), 754(s), 724(m), 608(w).
Complex 3: Mp > 300ꢀC. Anal. Calcd. for C25H19I2N5Zn :
C, 42.37; H, 2.70; I, 35.82; N, 9.88; Zn, 9.23%; Found: C,
42.45; H, 2.68; N, 9.92%. IR (KBr, cm¡1): 3197(w), 2968(w),
1602(m), 1516(s), 1451(s), 1406(s), 1291(m), 1231(m), 1102
(m), 1068(s), 993(w), 800(s), 774(s), 753(s), 724(m), 607(w).
Table 3. Experimental wavelengths (λexp), calculated wave-
lengths (λcal) and major contribution for complexes 1–3 and L
f
λexp(nm)
λcal (nm)
Composition
L
289
324
336
289
323
336
290
322
336
291
322
336
294
315
337
285
316
340
289
321
337
288
325
336
HOMO-1!LUMO
HOMO-1!LUMOC1
HOMO!LUMOC1
HOMO-2!LUMO
HOMO!LUMOC4
HOMO!LUMOC1
HOMO-2!LUMOC1
HOMO-1!LUMOC4
HOMO!LUMOC3
HOMO-1!LUMOC2
HOMO-1!LUMOC3
HOMO!LUMOC2
1
2
3

642
Wang et al.
Single crystals of L and complex 2 and 3 were obtained by the pyrazole rings. It is adverse to p-electron delocalization in
evaporating slowly in ethanol.
their respective planes. The two molecules are linked by inter-
molecular weak interactions C(8)¡H(8)¢¢¢p and C(5)¡H
ꢀ
ꢀ
(5)¢¢¢p (d(H(8)¢¢¢p) D 3.279 A, d(H(5)¢¢¢p) D 3.263 A)
between two carbazole rings.
Results and Discussion
The adjacent molecules are stacked through C–H. . .p
interactions. The ꢀ distance of H(20)¢¢¢p and H(48)¢¢¢p are
2.858 and 2.889 A, respectively, which generate an infinite
1D chain structure along b axis as shown in Figure 1b. 2D
structure is generated via hydrogen bonds along the c axis as
Crystal Structures
Crystal structure of ligand
Ligand L crystallizes in the monoclinic space group P21,
selected bond distances and angles are listed in Table 2. In
the asymmetric unit, there are two molecules with slightly dif-
ferent structures (Figure 1a). The dihedral angles between
carbazole ring and the central phenyl unit are 45.6ꢀ in mole-
cule I and 46.4ꢀ in molecule II. In molecule I, the dihedral
angles of the central phenyl unit and pyrazole rings (P1, P2)
are 71.4ꢀ and 80.4ꢀ, respectively. The dihedral angle of two
pyrazole rings (P1, P2) is 54.9ꢀ. In molecule (II), the dihedral
angles of the central phenyl unit and pyrazole ring (P3, P4)
seen from Figure 1c. The distance of hydrogen bond H(22)¢¢¢
ꢀ
N(3) and H(50)¢¢¢N(10) are 2.628 and 2.614 A, respectively.
The adjacent layers are linked by C(20)–H(20)¢¢¢p and C
(48)–H(48)¢¢¢p interactions to form 3D supramolecular struc-
ture, as shown in Figure 1d, indicating that hydrogen bonds
and C–H¢¢¢p bonds are very important to form a three-
dimensional supramolecular structure (Figure 1d).
Crystal structure of ZnBr2L (2)
are 71.8ꢀ and 80.0ꢀ, respectively. The dihedral angle of two In the molecular structure of complex 2, Zn(II) ion is four
pyrazole rings (P3, P4) is 55.5ꢀ. So the results indicate that no coordinated by two nitrogen atoms of the pyrazolyl groups
extended conjugation among the carbazole, the phenyl and (L) and two bromine ions to form a distorted tetrahedral
Fig. 1. (a) The molecular structure of L; H atoms are omitted for clarity. (b) The 1D linear chain of ligand L along the b-axis; H
atoms are omitted for clarity. (c) The 2D network of ligand L showing the weak hydrogen-bonding; H atoms are omitted for clarity.
(d) The 3D supramolecular structure of ligand L; H atoms are omitted for clarity.

Synthesis, Crystal Structures, and Photoluminescent Properties of Bis(pyrazol-1-yl)methane Derivative
643
Fig. 2. (a) The molecular structure of complex 2; H atoms are omitted for clarity. (b) 1D chain structure of complex 2 showing
CÀÀH¢¢¢Br interactions along the a-axis; H atoms are omitted for clarity. (c) 2D layer motif of complex 2 showing the weak
CÀÀH¢¢¢p interactions along the c-axis; H atoms are omitted for clarity. (d) 3D supramolecular structure of complex 2 showing the
weak CÀÀH¢¢¢p interactions along the b-axis; H atoms are omitted for clarity.
geometry (Figure 2a). The two pyrazole groups linked to structure along the a-axis. The adjacent moleculars are
Zn(II) lead to changes in the structure of ligand. The dihedral bridged by intermolecular C(19)¡H(19)¢¢¢Br(2) and C(25)¡
angles (between the carbazole ring and the phenyl unit, H(25)¢¢¢Br(1) hydrogen bonding interactions as shown in
between the phenyl unit and pyrazole rings, between the two Figure 2b. The distances of H(19)¢¢¢Br(2) and H(25)¢¢¢Br(1)
ꢀ
pyrazole rings) are 56.9, 73.3, 80.7, and 49.7ꢀ, respectively. are 2.825 and 2.914 A, respectively. The neighboring chains
The dihedral angles between the carbazole ring and the phe- are parallelly linked by C(2)¡H(2)¢¢¢p weak interactions to
nyl unit, or between the phenyl unit and pyrazole rings, are aggregate a 2D plane (Figure 2c). The distance of H(2)¢¢¢p is
ꢀ
larger than those of the free ligand. However, the dihedral 3.550 A. It is the C(22)¡H(22)¢¢¢p, as well as C(24)¡H
angle of the two pyrazole rings is smaller than that observed (24)¢¢¢p interactions that link the adjacent layers to form 3D
for the free ligand, indicating that the planarity of ligand in supramolecular structure, as shown in Figure 2d. The distan-
ꢀ
complex 2 is worse than that for free ligand. TheꢀZn¡N3 and ces of H(22)¢¢¢p and H(24)¢¢¢p are 3.006 and 3.760 A,
Zn–N5 bond lengths are 2.071(4) and 2.064(3) A, which are respectively.
within the normal range.[46–49] The bond distances of Zn–Br1
ꢀ
ꢀ
and Zn–Br2 are 2.3639(9) A and 2.3532(10) A, respectively.
Crystal structure of ZnI2L (3)
The bond angles around Zn2C are in the range of 89.3–
120.4ꢀ, which shows that bond angle for N3-Zn-N5 is much In the molecular structure of complex 3, Zn(II) ion is four
smaller than that of Br1–Zn–Br2. This is a common struc- coordinated by two nitrogen atoms of the pyrazolyl groups
tural feature for ZnX2L model complexes (X D Cl, Br, I).[50]
(L) and two iodide ions to form a distorted tetrahedral geom-
In the crystal structure, the hydrogen bonding C¡H¢¢¢p etry (Figure 3a). In complex 3, the changes in the structure of
interactions play important roles in the formation of the 3D ligand are similar to that of complex 2. The planarity of

644
Wang et al.
Fig. 3. (a) The molecular structure of complex 3; H atoms are omitted for clarity. (b) 1D structure of complex 3 showing the weak
CÀÀH¢¢¢I interactions along the a-axis; H atoms are omitted for clarity. (c) 2D layer motif of complex 3 showing the weak CÀÀH¢¢¢p
interactions along the c-axis; H atoms are omitted for clarity. (d) 3D supramolecular structure of complex 3 showing the CÀÀH¢¢¢p
interactions along the b-axis; H atoms are omitted for clarity.
ꢀ
coordinated ligand is also worse than that of the free ligand. range. The bond distances for Zn¡I are 2.5504(9) A and
ꢀ
The dihedral angles for complexes 2 and 3 are listed in 2.5327(9) A for Zn¡I1 and Zn¡I2, respectively. The bond
Table 3. The Zn¡N3 and Zn¡N5 bond lengths are 2.057(3) angles for I1¡Zn¡I2 and N3¡Zn¡N5 are 112.34(4) and
ꢀ
and 2.050(4) A, respectively, which are within the normal 88.74 (14)ꢀ, respectively.
Fig. 4. (a) UV-vis (c D 1 £ 10¡5 mol L¡1) spectra of complexes 1–3 and L in DMF. (b) The one-photon induced fluorescence (c D 1 £
10¡5 mol L¡1) spectra of complexes 1–3 and L in DMF.

Synthesis, Crystal Structures, and Photoluminescent Properties of Bis(pyrazol-1-yl)methane Derivative
645
In the crystal, the neighboring molecules of 3 are linked by Absorption and Single-Photon Exited Fluorescence (SPEF)
intermolecular C(19)¡H(19)¢¢¢I(2) and C(23)¡H(23)¢¢¢I(1)
Linear absorption properties and TD-DFT studies
hydrogen bonding interactions to form a one-dimensional
The linear absorption of complexes 1–3 and L are shown in
structure as shown in Figure 3b. The distances of H(19)¢¢¢I(2)
ꢀ
ꢀ
Figure 4a, from which it can be seen that their absorption
spectra exhibit triple bands in the range of 270–400 nm in
DMF. The absorption spectra of the investigated compounds
show similar features. The high-energy band at about
288 nm was tentatively assigned to the p!p* transition of
the carbazole moiety, while the two low-energy bands at
about 322 and 335 nm were attributed to intraligand charge
and H(23)¢¢¢I(1) are 3.050 A and 3.141 A, respectively. The
1D chain structures are interconnected by C(5)¡H(5)¢¢¢p
weak interactions to aggregate a 2D sheet structure
ꢀ
(Figure 3c). The distance of H(5)¢¢¢p is 3.560 A. The adjacent
layers are linked by C(22)¡H(22)¢¢¢p interaction with H
ꢀ
(22)¢¢¢centroid distance of 3.209 A to form 3D supramolecu-
lar structure, as shown in Figure 3d.
Fig. 5. (a) Molecular orbital energy diagram for L (TD-DFT/BP86). (b) Molecular orbital energy diagram for complex 1 (TD-DFT/
BP86). (c) Molecular orbital energy diagram for complex 2 (TD-DFT/BP86). (d) Molecular orbital energy diagram for complex 3
(TD-DFT/BP86).

646
Wang et al.
td (ps)
Table 4. Single-photon-related photophysical properties of L, 1, 2, and 3 in DMF
Compound
λex (nm)a/e
λem (nm)b
Kc
L
1
2
3
289(5.31) 324(0.94) 336(1.01)
289(5.79) 323(1.08) 336(1.14)
290(5.61) 322(1.01) 336(1.09)
291(7.07) 322(1.28) 336(1.20)
349, 363
349, 362
349, 364
349, 363
5.28%
4.78%
5.49%
3.90%
6.22
105
338
105
aPeak position of the largest absorption band in nm; bPeak position of SPEF, exited at the absorption maximum; cQuantum yields determined by using fluo-
rescein as standard; dThe fitted fluorescence lifetime.
transfer (ICT) transition. The results will be further corrobo- double bonds contributes to a decrease in lifetime.[51] It is
rated by calculations as follows.
suggested that any restriction of the rotation, such as place-
TD-DFT computational studies were performed to ment of the fluorophores into a rigid environment, lowering
elucidate the electronic structures of the ground state of the temperature, or rigidification of the feeble parts of the
the complexes 1–3 and L. The schematic representation of molecules would marginalize the role of the nonradiative
the molecular orbitals of complexes 1–3 and L was exhibited pathway and lead to the subsequent increase fluorescence life-
in Figures 5a–5d, and experimental wavelengths (λexp), cal- time. Herein, the zinc ion in the complexes rigidify the two
culated wavelengths (λcal), and compositions of some fron- pyrazole ring of ligand L, benefiting to prolong their lifetime.
tier orbitals are listed in Table 3. Figure 5a shows the
calculated frontier orbitals of (L). The band calculated is at
337 nm, which mainly originates from transitions of
HOMO to LUMOC1. At shorter wavelengths, a broad
Conclusions
band found at 324 nm around may be related to the calcu-
In summary, a novel bis(pyrazol-1-yl)methanes derivatives 9-
lated intense band at 315 nm, corresponding to the HOMO-
(di(1H-pyrazol-1-yl)-methyl)-9H- carbazole and its zinc halide
1 to LUMOC1. At shortest wavelengths, the band calcu-
complexes were presented. The single crystal X-ray diffraction
lated is at 294 nm, which mainly originates from transitions
analysis display 1D, 2D, and 3D structure of the ligand (L)
of HOMO-1 to LUMO. Figure 5b shows the calculated
and the complexes 2 and 3. Various weak interactions, includ-
frontier orbitals of complex 1. The lowest energy band cal-
ing hydrogen bonds (NÀÀH¢¢¢N and CÀÀH¢¢¢Br /I) and
culated is at 340 nm. This band mainly originates from tran-
CÀÀH¢¢¢p contacts play significant roles in the final supermo-
sitions of HOMO to LUMOC1. At shorter wavelengths, a
lecular structures. We also studied correlations between the
band found at 323 nm approximately may be related to the
structure and photophysical properties of L and complexes 1–
calculated intense band at 316 nm, corresponding to the
3, which have been verified by TD-DFT calculations.
transition from the HOMO to LUMOC4. At shortest wave-
lengths, the band calculated is at 285 nm, which mainly
originates from transitions of HOMO-2 to LUMO. In sum-
mary, these initial DFT and TD-DFT calculations on com-
plexes 1–3 and L provide reasonable explanations for their
absorption spectra. The results from theoretical calculation
are consistent with that of the previous experiments.
Funding
This work was supported by a grant for the National Natural
Science Foundation of China (21271004, 21071001,
21271003, 51142011), the Natural Science Foundation of
Anhui Province (1208085MB22). Focus on returned overseas
scholar. Program for New Century Excellent Talents in Uni-
versity (China), Doctoral Program Foundation of Ministry
of Education of China (20113401110004).
Single-photon exited fluorescence (SPEF)
Single-photon-related photophysical data of L, 1, 2, and 3 in
DMF are collected in Table 4, including fluorescence quan-
tum yields and lifetimes. The SPEF spectra were measured at
the same concentration as that of the linear absorption spec-
tra. Figure 4b is the single-photon excited fluorescence spec-
tra of the four compounds in DMF. The two fluorescence
peaks of complexes 1–3 and L around 349 and 363 nm are
clearly shown in Figure 4b. Their single-photon fluorescence
spectra are also similar because of their structural compara-
bility. Two bands are corresponding to typical p-p* transi-
tion of carbazole unit, delocalized over the whole conjugated
p electronic system. In addition, all the compounds exhibit
low fluorescence quantum yields, which is related to the struc-
ture of the compounds. Compared with L, fluorescence life-
time of complexes 1–3 increased, due to rotation around
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