Structures, photoluminescence and theoretical studies of two Zn II complexes with substituted 2-(2-hydroxyphenyl)benzimidazoles

Article abstract of DOI:10.1002/ejic.200500174

Two new Zn^II complexes of 2-(2-hydroxyphenyl)benzimidazole (Hpbm), and 5-ammo-2-(1H-benzoimidazol-2-yl)phenol (Hapbm), namely [Zn(pbm) ₂] (1), and [Zn(apbm)₂]· C₂H ₅OH·H₂O (2), as well as t

Full text of DOI:10.1002/ejic.200500174

FULL PAPER
Structures, Photoluminescence and Theoretical Studies of Two ZnII Complexes
with Substituted 2-(2-Hydroxyphenyl)benzimidazoles
Yi-Ping Tong,[a,b] Shao-Liang Zheng,*[a] and Xiao-Ming Chen*[a]
Keywords: Density functional calculations / N,O ligands / Photoluminescence / Pi interactions / Zinc
Two new ZnII complexes of 2-(2-hydroxyphenyl)benzimid-
azole (Hpbm), and 5-amino-2-(1H-benzoimidazol-2-yl)phe- tronic transitions in the photoluminescent processes have
blue-light-emitting electroluminescent materials. The elec-
nol (Hapbm), namely [Zn(pbm)2] (1), and [Zn(apbm)2]·
C2H5OH·H2O (2), as well as the ligands themselves, have
been prepared and characterized by X-ray crystallography
and photoluminescence studies. Both 1 and 2 are neutral,
mononuclear molecules that display strong photolumines-
cence in the blue regionand thus may serve as candidates for
also been investigated by means of time-dependent density
functional theory (TDDFT) energy level and molecular orbit-
als analyses, which show that their absorption and lumines-
cent properties are ligand-based.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
portant candidates for EL emitters for their excellent emit-
ting properties[7] and low cost, in comparison with other
d10 metal (e.g. AuI) complexes.[10] We recently reported a
class of blue/green light luminescent d10 metal complexes
containing the new N,O-donor ligand Hophen (Hophen =
1H-[1,10]phenanthrolin-2-one) and the relation between
molecular structure and luminescence properties with the
help of X-ray single-crystal diffraction analyses and a DFT
study of the ground electronic states.[11]
In our continuing efforts to design and synthesize blue-
emitting materials, we now extend our focus to benzimida-
zole derivatives,[12] and report herein the syntheses, crystal
structures, and luminescence properties of two neutral, mo-
nomeric ZnII complexes, namely [Zn(pbm)2] (1) and
[Zn(apbm)2] (2) [Hpbm = 2-(2-hydroxyphenyl)benzimid-
azole; Hapbm = 5-amino-2-(1H-benzoimidazol-2-yl)phe-
nol] (Scheme 1). The electronic transitions in the photolu-
minescent process have also been studied by means of time-
dependent density functional theory (TDDFT) calculations.
Introduction
Since the first report of a double-layer green organic elec-
troluminescence (EL) device based on Alq3 (Hq = quinolin-
8-ol) in 1987,[1] metal chelate complexes of AlIII, BIII, and
ZnII have been extensively investigated for their electrolumi-
nescent properties.[2,3] Unfortunately, few systematic investi-
gations of the luminescence properties of these complexes
have been carried out as extensive structural information is
only now becoming available[4,5] and computational tech-
niques have only recently allowed reliable calculations of
larger molecules.[5,6] For example, [Zn(pbt)2]2 [Hpbt = 2-(2Ј-
hydroxyphenyl)benzothiazole] has been studied as an excel-
lent white EL material,[7] even though its molecular struc-
ture and electronic characteristics based on the density
functional theory (DFT) calculations have only recently
been reported.[5]
Although blue-light-luminescent coordination complexes
have been an active research field for two decades,[2,8–10]
stable and strong blue-emitting metal complexes are still
rare, unlike the other basic components of white emission
(red and green). It has been shown that some d10 metal
complexes with N,O-donor ligands may have the high glass
transition temperatures required for stable light-emitting di-
odes and demonstrate nice blue-emitting EL properties.[2,3,5]
Among them, ZnII complexes have been proved to be im-
Scheme 1. The structures of Hpbm (R = H) and Hapbm (R = NH2)
with atomic labels.
[a] State Key Laboratory of Optoelectronic Materials and Technol-
ogies, School of Chemistry and Chemical Engineering, Sun Yat-
Sen University,
Guangzhou 510275, China
Results and Discussion
Fax: +86-20-8411-2245
E-mail: cescxm@zsu.edu.cn
Synthesis and Characterization
[b] Department of Chemistry, Hanshan Normal College,
Chaozhou 521041, China
For practical applications, neutral coordination com-
pounds are usually required since they may possess impor-
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500174
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Two ZnII Complexes with Substituted 2-(2-Hydroxyphenyl)benzimidazoles
FULL PAPER
tant characteristics for the performance of their EL proper- meric supramolecular structure in 1 (Figure 2, a). Such
ties, such as a relatively high glass transition temperature supramolecular dimers are stacked by edge-to-face C–H···π
and thermal stability, easy sublimation, and an ability to interactions (H···π ca. 2.75 Å) (Figure 2, b) between benz-
form thin films under vacuum.[2,3] Therefore, neutral, mo- imidazole and phenolate rings of adjacent molecules, giving
nonuclear metal complexes should be expected to be excel- rise to a three-dimensional supramolecular array, while the
lent candidates for EL materials. Similar to the other com- π–π stacking interactions are in a nonparallel mode be-
plexes that can easily form thin films under vacuum,[3] both tween the ligand planes of adjacent molecules, with face-to-
1 and 2 can be prepared by mixing solutions of zinc acetate face distances of 3.35–3.60 Å in 2 (Figure 2, c).
and the corresponding ligand in a 1:2 ratio in ethanol. Un-
fortunately, single crystals for X-ray diffraction were hard
to grow, thus different methods, including conventional
evaporation, diffusion, and hydrothermal methods were
employed. In contrast, many solid EL metal complex mate-
rials have, in fact, only been identified by their chemical
compositions rather than their structures. Some of their
molecular structures may be much more complicated than
their empirical formulae, since they may actually be charac-
terized to be dimeric or multinuclear structures in the solid,
such as the cases of [Znq2]4,[13] [Zn(pbt)2]2,[5] and [Zn(oz)2]2
[Hoz
=
2-(2Ј-hydroxyphenyl)-2-oxazoline].[9] This fact
shows that in the absence of X-ray structures, some conclu-
sions about their luminescence properties may be controver-
sial.[3] Fortunately, both 1 and 2 were found to be neutral,
mononuclear molecules by X-ray crystallography, thus sys-
tematic investigations of their luminescence properties can
be carried out. Our trials also imply that the crystallization
conditions are important.
Thermogravimetric analyses (TGA and DTG) of 1 and
2 show their high thermal stability, with decomposition
temperatures of 396 and 472 °C, respectively (Figure S1 in
the Supporting Information), which are similar to other EL
metal-organic materials.[5,12] Preliminary trials also proved
that both readily form films under vacuum.
Crystal Structures
Single-crystal X-ray diffraction analyses revealed that
both 1 and 2 are neutral, mononuclear molecules with the
ZnII ion being tetrahedrally coordinated by two deproton-
ated pbm or apbm ligands (Figure 1). The dihedral angles
between two ligand planes of about 89° and 88°, respec-
Figure 1. ORTEP views (at the 50% probability level) of 1 (a) and
2 (b).
There are also intermolecular hydrogen-bonding interac-
tively, indicate a slight distortion from an ideal tetrahedral tions in 1 and 2. In 1, the intermolecular hydrogen bonds
geometry for 1 and 2. The N–Zn–N and O–Zn–O angles [N(7)···O(2) = 2.796(2) Å; N(2)···O(3) = 2.822(2) Å] exist
[122.7(2)° and 110.1(1)° for 1; 116.2(1)° and 114.0(1)° for 2] between the benzimidazole N–H groups and the deproton-
are typical for a tetrahedral geometry. The Zn–O bond ated phenolate oxygen atom, furnishing a supramolecular
lengths of 1.932(1) and 1.931(2) Å in 1 and 1.932(3) and dimer (Figure 2, a). However, the hydrogen-bonding inter-
1.944(3) Å in 2 are slightly shorter than those documented actions are more complicated in 2 owing to the existence of
in the literature, whereas the Zn–N bond lengths of 1.951(2) lattice water and ethanol molecules. The lattice water mole-
and 1.953(2) Å in 1 and 1.958(3) and 1.975(3) Å in 2 are cule forms two hydrogen bonds to two ethanol molecules
also slightly shorter than the literature values.[5,13,14] The [O(1w)···O(1) = 2.803(6) Å and O(1w)···O(2) = 2.944(6) Å],
two crystallographically unique ligands have dihedral and accepts one hydrogen bond from a benzimidazole N–
angles (ca. 7.2° and 7.3° for 1; 9.9° and 20.7° for 2) between H group [N(1)···O(1w) = 2.855(6) Å] (Figure 3, a). More-
the benzimidazole and phenolate moieties which indicate over, the ethanol molecule forms a hydrogen bond to the
that the ligands are only slightly non-coplanar in 1, al- phenolate oxygen atom [O(1)···O(4) = 2.720(4) Å], and
though one ligand is significantly non-coplanar in 2. Head- there are also intermolecular hydrogen-bonding interac-
to-tail π–π stacking interactions (interligand distance of ca. tions between the benzimidazole N–H groups and phenol-
3.60 Å) exist between two molecules and give rise to a di- ate oxygen atoms [N(2)···O(6) = 2.791(4) Å; Figure 3, b].
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Figure 3. Perspective views of hydrogen-bonding interactions in 2.
Figure 2. Perspective views of packing patterns in 1 (a, b) and 2
(c).
Neutral Hpbm and Hapbm were also crystallographi-
cally characterized. The dihedral angles (ca. 2.2° and 4.2°)
between the phenolate and benzimidazole moieties for
Hpbm and Hapbm indicate that both are basically copla-
nar. In the crystal structures of Hpbm and Hapbm, there is
an intramolecular hydrogen bond between the phenolic and
the imidazole groups [O(1)···N(1) = 2.554(2) Å for Hpbm
and 2.563(2) Å for Hapbm] and intermolecular hydrogen
bonds between the imidazole N–H groups and phenolic
group oxygen atoms [N(2A)···O(1) = 2.821(3) for Hpbm
and 2.826(2) Å for Hapbm] (Figure 4). These intermo-
Figure 4. Perspective views of hydrogen-bonding interactions in
lecular hydrogen bonding and π–π interactions extend adja- Hpbm (a) and Hapbm (b).
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Two ZnII Complexes with Substituted 2-(2-Hydroxyphenyl)benzimidazoles
FULL PAPER
cent molecules into helical chains, where each pair of adja- to be observed experimentally. According to our TDDFT
cent molecules exhibit offset π–π stacking interactions with calculations (Table 1), the lowest-energy absorption max-
face-to-face distances of around 3.43 Å in Hpbm and ima (S0–S1 transition) are at 313 and 314 nm, with oscil-
around 3.41 Å in Hapbm (Figure 5).
lator strengths of 0.44 and 0.78 for Hpbm and Hapbm,
respectively. However, the lowest-energy absorption maxi-
mum for 1 should be attributed to the S0–S3 transition
(wavelength: 364 nm; oscillator strength: 0.24), as the oscil-
lator strength of the S0–S1 transition (wavelength: 370 nm)
is only 0.04. Similarly, the lowest-energy absorption maxi-
mum for 2 can be attributed to the S0–S4 transition (wave-
length: 344 nm; oscillator strength: 0.34), while its discerni-
ble shoulder is the S0–S1 transition (wavelength: 354 nm,
oscillator strength: 0.16). The excited state–ground state
(ES-GS) separations derived from the TDDFT calculations
are in agreement with those observed experimentally.
For Hpbm and Hapbm, the S0–S1 transitions are mainly
associated with transitions from the corresponding
HOMOs to the LUMOs, as the coefficients in the configu-
ration interaction wave functions are up to 0.63. As shown
in Figure 6, the HOMOs are the π-bonding orbitals, while
the LUMOs are the π*-antibonding orbitals, thus S0–S1
transitions can be assigned to be πǞπ* in nature.
Figure 6. Contour plots of the relevant HOMOs and LUMOs of
Hpbm (a) and Hapbm (b).
Figure 5. Perspective views of one-dimensional supramolecular ar-
rays packed by hydrogen bonds and π–π stacking interactions in
Hpbm (a) and Hapbm (b).
Similar to the corresponding ligands, the S0–S1 transi-
tions of the ZnII complexes are also mainly associated with
transitions from the corresponding HOMOs to the LUMOs
(Table S1 in the Supporting Information). As shown in Fig-
ure 7, the HOMOs are mainly the π-bonding orbitals of one
deprotonated ligand, while the LUMOs are the π*-anti-
UV/Vis and Luminescent Spectra
The lowest-energy absorption bands of Hpbm and bonding orbitals of another deprotonated ligand, thus the
Hapbm in dichloromethane at 298 K occur at 323 and S0–S1 transitions can be assigned to be ligand-centered
325 nm, respectively, while those of their ZnII complexes in πǞπ* in nature (LCCT).
dichloromethane are red-shifted slightly to 331 nm for 1
However, the S0–S3 transition (lowest-energy absorption
and 327 nm for 2, with discernible shoulders at 343 and maximum) of 1 is in fact mainly associated with the transi-
340 nm, respectively (see Figure S2 in the Supporting Infor- tions from the corresponding HOMO–1 to LUMO and
mation).
HOMO to LUMO+1, while the S0–S4 transition of 2 is
The lowest-energy absorption maxima in UV spectra mainly associated with the transitions from the correspond-
may correspond to S0–Sn transitions with n Ն 1, as the S0– ing HOMO–1 to LUMO+1 and HOMO to LUMO+1
S1 transition may have a lower oscillator strength,[15–17] (Table S1 in the Supporting Information), although such
which are fully or partly transition-forbidden and too weak transitions are also assigned to be πǞπ* in nature.
Table 1. The calculated and experimental absorption wavelengths [nm] and their transition nature for 1, 2, Hpbm, and Hapbm, together
with oscillator strengths.
Transition
nature
Wavelength
Oscillator
strength
Calcd.
Exp. in CH2Cl2
Exp. in solid
Hpbm
Hapbm
1
2
πǞπ*
πǞπ*
πǞπ*
πǞπ*
313
314
364
344
323
325
331
327
342
348
377
368
0.44
0.78
0.24
0.34
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Y.-P. Tong, S.-L. Zheng, X.-M. Chen
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Scheme 2. The electronic transitions in the photoluminescent pro-
cess of 1 or 2 (a) and Hpbm or Hapbm (b).
Figure 7. Contour plots of the relevant molecular orbitals (from
HOMO–1 to LUMO+1) of 1 (a) and 2 (b).
Moreover, the weakly electron-donating amino group
can increase the electron density of the aromatic group and
hence reduce the ES-GS separations slightly, consistent with
the S0–S1 energy separations found in either the TDDFT
energy levels or experimental absorption spectra of the
planar Hpbm and Hapbm. On the other hand, in the ab-
sence of intramolecular hydrogen-bonding interactions (O–
H···N), the 5-amino substitution may further twist the de-
protonated ligand plane, as indicated by the experimental
dihedral angle variation between the phenolate and benzim-
idazole rings of 2, resulting in the reduction of the electron
delocalization energy. Such a decrease of the delocalization
energy is not favored for a π–π* transition as it may increase
the energy separation. Compared with the weak electron-
donating effect, the non-coplanar effect may be much
stronger in 2. In the current case, this hypothesis can be
verified theoretically, as the higher ES-GS separations of 2
can be found in the TDDFT energy levels. Thus, compared
to that of 1, a significant blue shift (up to 15 nm) is ob-
served in the luminescence of 2. Similarly, compared to that
of Hpbm, the higher emission energy of Hapbm in the non-
coplanar ESIPT state is expected, although its S0–S1 energy
separation is slightly reduced.
As has been noted,[11,18–20] the deprotonation and coor-
dination of organic ligands to d10 metal ions can signifi-
cantly reduce the energy gaps between the HOMOs and
LUMOs. The TDDFT energy levels and experimental ab-
sorption spectra show that the S0–S1 energy separations of
both ZnII complexes become smaller than those of the cor-
responding ligands. According to the energy-gap law for ra-
diationless deactivation,[17,21,22] the luminescence of the
ZnII complexes should be red-shifted compared with that
of corresponding ligands. However, for the crystalline solid
samples, Hpbm and Hapbm emit blue light with a maxi-
mum at 444 nm (λex = 352 nm) and 426 nm (λex = 365 nm)
at 298 K, respectively, while 1 and 2 emit at 434 nm (λex
=
384 nm) and 419 nm (λex = 379 nm), respectively (Figure 8).
The violation of blue shifts can be ascribed to the excited
state intramolecular proton transfer (ESIPT) of such or-
ganic compounds, which produces a strongly Stokes-shifted
low-energy tautomeric fluorescence (Scheme 2).[12,23–25]
To the best of our knowledge, ZnII complexes with aro-
matic heterocyclic ligands usually exhibit an emission tran-
sition that is an intraligand charge-transfer (ILCT). This is
in good agreement with the assignment of the πǞπ* nature
of the S0–S1 transitions for 1 and 2. Similar to those of
common ZnII complexes,[18,19] the lifetimes of solid 1 and 2
are around 1.90(2) and 1.21(1) ns at room temperature.
Conclusions
Figure 8. The excitation (left) and emission (right) spectra of 1, 2,
Hpbm, and Hapbm in the solid state at 298 K. The corresponding
excitation wavelengths, λex, are 384, 379, 352, and 365 nm, respec-
tively.
Two neutral, mononuclear ZnII complexes and their li-
gands have been prepared as possible candidates for blue-
light-emitting EL materials. Systematic investigations of
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Two ZnII Complexes with Substituted 2-(2-Hydroxyphenyl)benzimidazoles
FULL PAPER
for about one week. C13H10N2O (210.2): calcd. C 74.27, H 4.79, N
13.33; found C 74.02, H 4.81, N 13.49. H NMR (500 MHz, [D6]-
DMSO): δ = 13.13 (s, 1 H), 13.12 (s, 1 H), 8.04 (dd, J = 1.50,
8.00 Hz, 1 H), 7.71 (d, J = 8.00 Hz, 1 H), 7.60 (d, J = 7.50 Hz, 1
H), 7.38 (m, 1 H), 7.28 (m, 2 H), 7.03 (m, 2 H) ppm. FTIR (KBr):
electronic transitions in the photoluminescent process of all
compounds have been carried out based on the X-ray struc-
tural information, as well as the TDDFT energy level and
molecular orbitals analyses, and these show that their ab-
sorption and luminescent properties are ligand-based. The
photophysical studies further explain the spectral variation
along with the effect of complexation with ZnII cations and/
or amino substitution.
1
ν = 3326 (vs), 1585 (s), 1492 (s), 1417 (s), 1320 (m), 1282 (m), 1262
˜
(s), 1133 (m), 1037 (w), 911 (w), 840 (w), 798 (w), 727 (s), 591 (w),
522 (w), 464 (w) cm–1.
Hapbm was similarly synthesized by reaction of o-phenylenediam-
ine (0.108 g, 1 mmol) with 4-aminosalicylic acid (0.153 g, 1 mmol).
X-ray quality crystals were grown by very slow evaporation of a
solution of DMF over about one month. The yield was ca. 10%.
C13H11N3O (225.2): calcd. C 69.32, H 4.92, N 18.66; found C
69.07, H 4.81, N 18.72. 1H NMR (500 MHz, [D6]DMSO): δ =
12.96 (s, 1 H), 12.68 (s, 1 H), 7.65 (d, J = 8.10 Hz, 1 H), 7.51 (s, 2
H), 7.17 (dd, J = 3.00, 7.16 Hz, 2 H Hz,), 6.21 (dd, J = 2.10,
8.40 Hz, 1 H), 6.14 (d, J = 1.50 Hz, 1 H), 5.68 (s, 2 H) ppm. FTIR
Experimental Section
General Remarks: All the reagents and solvents employed are com-
mercially available and were used as received without further purifi-
cation. The C, H, and N microanalyses were carried out with an
1
Elementar Vario El elemental analyzer. H NMR spectra were re-
corded with a Varian INOVA500NB spectrometer. FTIR spectra
were recorded with a Bruker Vector22 spectrometer in KBr pellets
in the range 4000–400 cm–1. The UV/Vis spectra were recorded
with a Varian Cary-100 spectrometer. The steady-state fluorescent
and fluorescence lifetimes were determined with an Edinburgh In-
strument FLS920 fluorescence spectrophotometer. Thermogravi-
metric data (TG and DTG) were collected with a Perkin–Elmer
TGS-2 analyser in flowing dinitrogen atmosphere at a heating rate
of 10 °Cmin–1 by heating the microcrystals.
(KBr): ν = 3471 (m), 3381 (s), 3221 (s), 1631 (s), 1589 (s), 1553
˜
(m), 1424 (s), 1363 (m), 1268 (s), 1198 (m), 1153 (m), 961 (w), 806
(m), 737 (s), 681 (w), 538 (w), 522 (w) cm–1.
Synthesis of [Zn(pbm)2] (1): A mixture of zinc acetate dihydrate
(0.110 g, 0.5 mmol), Hpbm (0.210 g, 1.0 mmol), and water (10 mL)
was heated in a 23-mL, Teflon-lined stainless-steel container at
110 °C for 4 d. After cooling to room temperature at a rate of 5 K
per hour, the colorless crystals of 1 were isolated (yield ca. 0.17 g,
70%). C26H18N4O2Zn (483.8): calcd. C 64.54, H 3.75, N 11.58;
found C 64.32, H 3.84, N 11.72. 1H NMR (500 MHz, [D6]DMSO):
δ = 13.34 (s, 2 H), 7.98 (d, J = 7.00 Hz, 2 H), 7.58 (d, J = 8.00 Hz,
2 H), 7.25 (d, J = 8.00 Hz, 4 H), 7.05 (q, J = 7.00 Hz, 4 H), 6.80
Synthesis of Hpbm and Hapbm: They were synthesized following
methods similar to those reported in the literature.[26] Salicylic acid
(0.138 g, 1 mmol) and o-phenylenediamine (0.108 g, 1 mmol) were
mixed and stirred in syrupy phosphoric acid (3 mL) at a tempera-
ture of ca. 520 K for 5 h to give white analytically pure Hpbm after (d, J = 7.50 Hz, 2 H), 6.68 (t, J = 7.00 Hz, 2 H) ppm. FTIR (KBr):
recrystallization of the crude product (ca. 10% yield). X-ray quality
crystals were grown by slow evaporation of a solution in CHCl3
ν = 3428 (m), 1798 (w), 1567 (s), 1478 (m), 1444 (m), 1407 (m),
˜
1311 (w), 1251 (w), 1140 (w), 876 (w), 738 (w), 654 (w) cm–1.
Table 2. Crystal data and structure refinement for 1, 2, Hpbm, and Hapbm.
Complex
1
2
Hpbm
Hapbm
Empirical formula
Formula mass
Temperature [K]
Crystal system
Space group
a [Å]
C26H18N4O2Zn
483.81
293(2)
monoclinic
P21/n
10.188(1)
10.010(1)
21.323(1)
94.029(1)
2169.2(3)
4
C28H28N6O4Zn
577.93
293(2)
orthorhombic
Pbcn
28.900(2)
9.1250(5)
20.062(1)
90
5290.4(5)
8
1.451
0.975
2400
C13H10N2O
210.23
293(2)
orthorhombic
Pna21
18.236(16)
4.8061(17)
11.990(11)
90
1050.8(14)
4
1.329
0.087
440
C13H11N3O
225.25
293(2)
orthorhombic
Pbca
12.932(1)
8.5641(7)
19.7343(16)
90
2185.5(3)
8
1.369
0.091
944
b [Å]
c [Å]
β [°]
V [Å3]
Z
ρcalcd. [mgm3]
Abs. coefficient [mm–1]
F(000)
1.481
1.164
992
Crystal size [mm]
Absorption correction
Index ranges
0.26×0.13×0.11
multi-scan
–13 Յ h Յ 10
–12 Յ k Յ 12
–27 Յ l Յ 27
13051
0.46×0.24×0.08
multi-scan
–37 Յ h Յ 36
–11 Յ k Յ 11
–26 Յ l Յ 19
29997
0.52×0.36×0.33
multi-scan
–23 Յ h Յ 10
–4 Յ k Յ 6
–15 Յ l Յ 14
4138
0.37×0.23×0.11
multi-scan
–16 Յ h Յ 15
–9 Յ k Յ 11
–25 Յ l Յ 20
12220
Reflections collected
Unique reflections
Parameters
4884
298
6054
359
2138
146
2494
154
Rint
0.0241
1.050
0.0361
0.0599
1.047
0.0612
0.0163
1.041
0.0425
0.0296
1.072
0.0566
Goodness-of-fit
R1 [I Ͼ 2σ(I)]
wR2 [I Ͼ 2σ(I)]
R1 (all data)
0.0914
0.0454
0.0967
0.403/–0.321
0.1524
0.1015
0.1784
0.783/–0.425
0.1023
0.0484
0.1057
0.152/–0.190
0.1247
0.0761
0.1336
0.182/–0.157
wR2 (all data)
Largest diff. peak and hole [eÅ–3]
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Y.-P. Tong, S.-L. Zheng, X.-M. Chen
Synthesis of [Zn(apbm)2]·C2H5OH·H2O (2): A filtered solution of Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
FULL PAPER
Hapbm (0.45 g, 2 mmol) and potassium hydroxide (0.112 g,
2 mmol) in ethanol (80 mL) was added to a solution of zinc acetate
dihydrate (0.22 g, 1 mmol) in ethanol (40 mL) at a temperature of
60 °C. The mixture was kept for 4 h at this temperature, and al-
lowed to stand overnight at room temperature. The white precipi-
tate was filtered, washed with ethanol, and dried under reduced
atmosphere over silica gel at room temperature for 3 h to give 2 as
pale-yellow microcrystals. X-ray quality crystals were obtained by
very slow evaporation of a solution in ethanol over about 60 days
(ca. 0.29 g, 50% yield based on Zn). C28H28N6O4Zn (579.0): calcd.
C 58.19, H 4.88, N 14.54; found C 58.33, H 4.58, N 14.42. 1H
NMR (500 MHz, [D6]DMSO): δ = 7.62 (d, J = 8.70 Hz, 2 H), 7.42
(d, J = 7.50 Hz, 2 H), 7.11 (t, J = 7.50 Hz, 2 H), 6.96 (t, J =
7.80 Hz, 2 H), 6.86 (d, J = 7.80 Hz, 2 H), 6.01 (dd, J = 2.10,
8.70 Hz, 2 H), 5.91 (d, J = 2.10 Hz, 2 H), 5.39 (s, 4 H). FTIR
data_request/cif.
Calculation Details: Based on the optimized geometries (selected
optimized bond lengths and bond angles are listed in Table S2 in
the Supporting Information), time-dependent density functional
(TDDFT) calculations were performed at the B3LYP level with a
6-31G** basis set for C, H, N, and O atoms, and effective core
potentials basis set LanL2DZ for Zn atoms, employing the
Gaussian03 suite of programs.[29] The electron density diagrams of
molecular orbitals were obtained with the Gaussview graphics pro-
gram.
Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (grant no. 20131020) and the Scientific and Techno-
logical Project of Guangdong Province (nos. 2003C103004, 036601,
and 04205405).
(KBr): ν = 3375 (s), 3334 (s), 3211 (m), 1624 (s), 1534 (s), 1478 (s),
˜
1463 (s), 1447 (s), 1396 (w), 1348 (w), 1327 (w), 1296 (w), 1253 (m),
1213 (m), 1157 (m), 980 (w), 848 (w), 811 (w), 751 (m), 602 (w),
539 (w), 508 (w) cm–1.
X-ray Crystallographic Study: Diffraction intensities for 1 and 2, as
well as Hpbm and Hapbm, were collected at 293 K on a Bruker
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Experimental details of the X-ray analyses are provided in Table 2,
with selected bond lengths and angles listed in Table 3.
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CCDC-258466 to -258468 (for 1, 2, and Hapbm, respectively) and
-240084 (Hpbm) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
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Table 3. Selected bond lengths [Å] and angles [°] for 1, 2, Hpbm,
and Hapbm.
1
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Zn(1)–O(2)
Zn(1)–O(1)
O(2)–Zn(1)–O(1) 110.1(1)
O(2)–Zn(1)–N(1) 121.0(1)
O(1)–Zn(1)–N(1) 95.7(1)
1.931(2)
1.932(1)
Zn(1)–N(1)
Zn(1)–N(3)
O(2)–Zn(1)–N(3) 95.3(1)
O(1)–Zn(1)–N(3) 112.6(1)
N(1)–Zn(1)–N(3) 122.7(1)
1.951(2)
1.953(2)
2
Zn(1)–O(1)
Zn(1)–O(2)
O(1)–Zn(1)–O(2) 114.0(1)
O(1)–Zn(1)–N(2) 94.7(1)
O(2)–Zn(1)–N(2) 110.7(1)
1.932(3)
1.944(3)
Zn(1)–N(2)
Zn(1)–N(5)
O(1)–Zn(1)–N(5) 126.7(1)
O(2)–Zn(1)–N(5) 95.1(1)
N(2)–Zn(1)–N(5) 116.2(1)
1.958(3)
1.975(3)
Hpbm
N(2)–C(8)
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N(1)–C(7)
N(1)–C(13)
N(2)–C(7)
O(1)–C(1)–C(6)
N(2)–C(7)–C(6)
1.322(3)
1.389(3)
1.359(3)
121.4(2)
124.9(2)
1.372(3)
1.355(3)
1.457(3)
123.4(2)
O(1)–C(1)
C(6)–C(7)
N(1)–C(7)–C(6)
Hapbm
O(1)–C(1)
N(1)–C(7)
N(1)–C(8)
O(1)–C(1)–C(6)
N(1)–C(7)–C(6)
1.356(2)
1.327(2)
1.389(2)
121.4(2)
123.4(2)
N(2)–C(7)
N(2)–C(13)
1.354(2)
1.382(2)
N(2)–C(7)–C(6)
N(3)–C(3)–C(4)
124.7(2)
121.0(2)
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Two ZnII Complexes with Substituted 2-(2-Hydroxyphenyl)benzimidazoles
FULL PAPER
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Received: February 27, 2005
Published Online: August 11, 2005
Eur. J. Inorg. Chem. 2005, 3734–3741
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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