Synthesis, Crystal Structure, and Photophysical Properties of Nickel Complex from Triphenylamine Schiff Base Ligand

Article abstract of DOI:10.1080/15533174.2014.989611

A novel Schiff base ligand L and its mononuclear nickel complex Ni(L)₂(SCN)₂ were designed, synthesized and characterized by elemental analysis, IR spectra, MS, ¹H-NMR spectroscopy, and single-crystal X-ray diffraction analysis. The crystals of L and Ni(L)₂(SCN)₂ belong to orthorhombic crystal system with the space group of P2₁2₁2₁ for L and Pbcn for Ni(L)₂(SCN)₂, respectively. The center atom Ni(II) is coordinated with six nitrogen atoms in a distorted octahedron coordination environment. The four N atoms of them are from the two independent ligands and the other two nitrogen atoms from two SCN^-. Their photophysical properties of the ligand and its Ni(II) complex were investigated and interpreted on the basis of theoretical calculations (TD-DFT).

Full text of DOI:10.1080/15533174.2014.989611

Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry
ISSN: 1553-3174 (Print) 1553-3182 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt20
Synthesis, Crystal Structure, and Photophysical
Properties of Nickel Complex From Triphenylamine
Schiff Base Ligand
Jiang Chen, Hui Wang, Zhepeng Jin, Bingfei Gao, Jieying Wu & Yupeng Tian
To cite this article: Jiang Chen, Hui Wang, Zhepeng Jin, Bingfei Gao, Jieying Wu & Yupeng Tian
(2016) Synthesis, Crystal Structure, and Photophysical Properties of Nickel Complex From
Triphenylamine Schiff Base Ligand, Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry, 46:6, 896-901, DOI: 10.1080/15533174.2014.989611
To link to this article: http://dx.doi.org/10.1080/15533174.2014.989611
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Date: 07 March 2016, At: 19:03

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry (2016) 46, 896–901
Copyright © Taylor and Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2014.989611
Synthesis, Crystal Structure, and Photophysical Properties of
Nickel Complex From Triphenylamine Schiff Base Ligand
JIANG CHEN1,2, HUI WANG1, ZHEPENG JIN1, BINGFEI GAO1, JIEYING WU1, and YUPENG TIAN1
1Department of Chemistry, Key Laboratory of Functional Inorganic Materials Chemistry of Anhui Province, Anhui University, Hefei,
P. R. China
2Deparment of Chemistry, Bengbu Medical College Bengbu, P. R. China
Received 29 March 2014; accepted 4 November 2014
A novel Schiff base ligand L and its mononuclear nickel complex Ni(L)2(SCN)2 were designed, synthesized and characterized by
1
elemental analysis, IR spectra, MS, H-NMR spectroscopy, and single-crystal X-ray diffraction analysis. The crystals of L and Ni
(L)2(SCN)2 belong to orthorhombic crystal system with the space group of P212121 for L and Pbcn for Ni(L)2(SCN)2, respectively.
The center atom Ni(II) is coordinated with six nitrogen atoms in a distorted octahedron coordination environment. The four N
atoms of them are from the two independent ligands and the other two nitrogen atoms from two SCN¡. Their photophysical
properties of the ligand and its Ni(II) complex were investigated and interpreted on the basis of theoretical calculations (TD-DFT).
Keywords: triphenylamine, Schiff base, crystal structure, photophysical properties
Introduction
to construct the novel D-p-A model ligand[23,24]; (b) in
order to enhance the solubility and the electron delocaliz-
Triphenylamine and its derivatives have good solubility ability of the molecule, ethyl oxygen was attached to the
and easily film-formation, good electron-donating ability, triphenylamine moiety; (c) as a result of the nickel coordi-
low redox potential, high hole-transfer ability, strong fluo- nated by the ligand,[25] higher electron delocalization sys-
rescence properties, and light stability, which have dis- tem forms within the functional coordination compounds.
played promising properties in the development of light
At the present work, a novel Schiff base ligand L and
emission,[1,2] organic field-effect transistors (OFET), pho- its mononuclear nickel complex were synthesized. And
tovoltaic devices, and dye-sensitized solar cells.[3–6] There- then, their photophysical properties of them were system-
fore, triphenylamine as a functional group has extensively atically investigated both experimentally and theoretically.
been used to construct and prepare novel photoelectric The synthetic procedure of Schiff base derivates are shown
materials.[7] On the other hand, Schiff base derivatives not in Scheme 1.
only have novel structures, but also possess strong coordi-
nation ability as mono-, bi- and multidentate ligands,
Experimental
which can coordinate with various transition and rare
earth metal ions to form Schiff base complexes,[8–14] which
have important applications in photosensitive materials,
catalytic materials, semiconductor materials, and antibac-
terial and antitumor uses.[15–22]
Instruments and Reagents
Ni(SCN)2, 2-pyridine formaldehyde and the other reagents
are analytically pure, and all will be purified before using
according to the standard methods. IR spectra (4000–400
cm¡1) as KBr pellets while far-IR spectra (40–400 cm¡1) as
nujol mull, were recorded on a Nicolet FT-IR 870 SX spec-
trophotometer. The 1H NMR and 13C NMR spectra
recorded on at 25ꢀC using Bruker 400 Ultrashield spectrome-
ter were reported as parts per million (ppm) from TMS (d).
MALDI-TOF mass spectra were recorded using Bruker
Autoflex III Smartbeam. Elemental analyses were carried out
on a Perkin Elmer 240 analyzer. Melting point is measured
on METTLER TOLEDOFP-62 instruments. UV spectra
were recorded on a SHIMADZU UV-3600 spectrophotome-
ter. The concentration of sample solution was 1.0£10¡5
mol/L.
Relying on consideration previously, we designed and
synthesized a novel Schiff base ligand L and its nickel
complex Ni(L)2(SCN)2. The design strategy is based
on the following: (a) triphenylamine as donor group, the
C H N as the bridge and connecting with pyridine group
Address correspondence to Jieying Wu, Department of Chemis-
try, Key Laboratory of Functional Inorganic Materials Chemis-
try of Anhui Province, Anhui University, 230039 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.

Nickel Complex
897
Fig. 1. Single molecular crystal structure of L.
catalyst (0.40 g) was added. Then slowly added 4 mL hydra-
zine hydrate (diluted with 2 mL ethanol). After 30 min, white
solid appeared, and was filtered. The above solid (3.48 g, 10
mmol) and 2-pyridine formaldehyde (1.61 g, 15 mmol) were
dissolved in ethanol and reflux. After 2 h, red solid precipita-
tion appeared. Under cooling to room temperature, red crystal
were separated by filtration and washed with ethanol. Yield:
91%. M. P. 147.8ꢀC. IR (KBr, cm¡1): 3035, 2978, 2907, 2866,
1626, 1565, 1504, 1479, 1335, 1245, 1046, 829. 1H-NMR
(400MHz, DMSO-d6) d: 1.308–1.342 (t, 6H), 3.984–4.035 (q,
4H), 6.787–6.807 (d, 2H), 6.907–6.928 (d, 4H), 7.034–7.055
(d, 4H), 7.291–7.312 (t, 2H), 7.465–7.495 (t, 1H), 7.899–7.937
(d, 1H), 8.108–8.127 (d, 1H), 8.613 (1H), 8.678–8.689 (d, 1H).
13C-NMR (100MHz, CDCl3) : 156.9, 155.4, 155.0, 149.5,
148.3, 142.8, 140.6, 136.6, 126.7, 124.6, 122.4, 121.6, 120.6,
115.3, 63.7, 14.9. Anal. Calcd. For C28H27N3O2: C, 76.85; H,
6.17; N, 9.607; Found: C, 76.68; H, 6.17; N, 9.58. MS: m/z:
438.58([M C]).
Sch. 1. Synthetic of the ligand L.
Synthesis
Synthesis of 4-ethoxy-N-(4-ethoxyphenyl)-N-(4-nitrophenyl)
benzenamine (2). Added iodine benzene ether (3.72 g, 15
mmol), paranitroaniline (0.69 g, 5 mmol), anhydrous potas-
sium carbonate (2.76 g, 20 mmol), L-proline (0.12 g), and
cuprous iodide (0.10 g) were dissolved in DMSO solution
and stirred for 48 h at 90ꢀC under nitrogen. Under cooling to
room temperature, the mixture solution was poured into
water, and then extracted by ethyl acetate, the organic phase
was dried by anhydrous magnesium sulfate, extraction filtra-
tion, the product was purified by column chromatography
(silica gel, 10:1 petroleum ether/ethyl acetate) to give a solid.
1
Yield: 64%. H-NMR (400 MHz, d6-CDCl3): 1.408–1.443
(t, 6H), 4.006–4.058 (q, 4H), 6.736–6.759 (d, 2H), 6.880–
6.901 (d, 4H), 7.107–7.128 (d, 4H), 7.978–8.001 (d, 2H).
Synthesis of Ni(L)2(SCN)2. The ligand L (0.44 g, 1
mmol) was dissolved in methanol and stirred until clear
Synthesis of (E) -N1- benzylidene-N4,N4- bis(4-ethoxyphenyl) solution appeared, and then Ni(SCN)2 (0.087 g, 0.5
benzene-1,4- diamine. 4-ethoxy-N-(4-ethoxyphenyl)-N-(4- mmol) was added, the mixture solution was refluxed for 4
nitrophenyl) benzenamine (1.00 g, 2.6 mmol) was dissolved in h. Under cooling to room temperature, the precipitate
8 mL ethanol solution, and refluxed, then carbon palladium was washed with distilled water and methanol. The
Fig. 2. 1-D chain structure of L.

898
Chen et al.
ꢀ
Table 2. Selected bond lengths (A) and angles (ꢀ) of L
N(1)-C(17)
N(1)-C(6)
N(1)-C(14)
O(1)-C(1)
C(3)-O(1)
C(20)-N(3)
N(3)-C(24)
C(24)-C(25)
1.388(5)
1.432(5)
1.442(5)
1.423(6)
1.355(5)
1.440(6)
1.369(3)
1.453(6)
C(3)-O(1)-C(1)
C(17)-N(1)-C(6)
C(17)-N(1)-C(14)
C(6)-N(1)-C(14)
N(3)-C(24)-C(25)
C(24)-N(3)-C(20)
C(25)-N(2)-C(29)
C(25)-N(2)
118.9(3)
120.9(3)
121.7(3)
116.8(3)
118.5(3)
114.6(3)
116.2(6)
1.327(7)
X-Ray Crystallography
The X-ray diffraction measurements were performed on a
Bruker SMART CCD area detector using ꢀgraphite mono-
chromated Mo-Ka radiation (λ D 0.71069 A) at 298 (2) K.
Intensity data were collected in the variable v-scan mode.
The structures were solved by direct methods and difference
Fourier syntheses. The non-hydrogen atoms were refined
anisotropically and hydrogen atoms were introduced geomet-
rically. Calculations were performed with SHELXTL-97 pro-
gram package.[26]
Fig. 3. (Top) Single molecular crystal structure of Ni(L)2(SCN)2
(The solvent molecule H2O was omitted) and (bottom) coordina-
tion environment of Ni with atom numbering scheme.
crystals were obtained by slow evaporation from acetone.
Yield: 86%. M. P. >300ꢀC. IR (KBr, cm¡1): 3035, 2978,
2907, 2866, 2084, 1596, 1566, 1502, 1475, 1320, 1245,
10465, 829. FT-IR: 524, 417, 321. C58H54N8O4S2Ni:
Anal. Calcd. C, 66.34%; H, 5.15%; N, 10.68%. Found: C,
66.09%; H, 5.14%; N, 10.63%.
Computational Details
Optimizations were carried out with B3LYP [LANL2DZ]
without any symmetry restraints, and the TD-DFT {B3LYP
[LANL2DZ]} calculations were performed on the optimized
structure. All calculations, including optimizations and TD-
DFT, were performed with the G03 software.[27] Geometry
optimization of the singlet ground state and the TD-DFT cal-
culation of the lowest 25 singlet-singlet excitation energies
were calculated with a basis set composed of 6-31G for C, H,
N, and O atoms and the Lanl2dz basis set for the Ni atom
was download from the EMSL basis set library. The lowest
25-spin allowed singlet-singlet transitions, up to energy of
about 5 eV, were taken into account in the calculation of the
absorption spectra.
Table 1. Crystal data and structure refinement for the ligand and
the complex
L
[Ni(L)2(SCN)2]ꢁH2O
Chemical formula
Formula weight
Crystal system
Space group
a (nm)
C
437.53
28 H27 N3 O2
C116H110N16Ni2O9 S4
2117.86
Orthorhombic
Pbcn
2.4128(5)
1.5869(5)
2.9819(5)
11.417(5)
4
1.232
0.465
4440
1.37–25.10
52253
Orthorhombic
P212121
0.98761(15)
1.27433(19)
1.9430(3)
2.4454(6)
4
1.188
0.076
928
1.91–24.99
11515
Results and Discussion
b (nm)
Structural Studies
c (nm)
The molecular structure of L and Ni(L)2(SCN)2 are shown in
Figures 1–4, respectively. Selected bond lengths and angles
are summarized in Tables 1–3, respectively.
V (nm3)
Z
Dc (g¢cm¡3
)
m (mm¡1
F(000)
)
ꢀ
Table 3. Selected bond lengths (A) and angles (ꢀ) of Ni
(L)2(SCN)2
u rang (ꢀ)
Reflections collected
Reflections unique
N(2)-Ni(1)
N(4)-Ni(1)
N(7)-Ni(1)
C(26)-N(2)
C(25)-C(26)
C(25)-N(4)
2.113(5)
2.136(4)
2.005(6)
1.320(7)
1.462(8)
1.256(6)
N(7)-Ni(1)-N(2)
N(2)-Ni(1)-N(4)
N(7)-Ni(1)-N(4)
C(26)-N(2)-Ni(1)
C(25)-N(4)-Ni(1)
N(2)-C(26)-C(25)
91.6(2)
78.0(2)
168.1(2)
113.9(4)
111.7(4)
114.7(6)
4204
10170
Parameters
307
673
ꢀ
Max, min Dr (e A¡3
R1, wR2 [I ꢀ2s (I)]
R1, wR2 [all data]
GOF
)
0.513, –0.364
0.0690, 0.1863
0.1096, 0.2251
1.033
0.629, –0.472
0.0748, 0.1553
0.2171, 0.1887
1.077

Nickel Complex
899
Fig. 4. 1-D chain structure of Ni(L)2(SCN)2.
Fig. 5. Linear absorption spectra of the ligand L and the complex Ni(L)2(SCN)2 (c D 1.0 £ 10¡5mol/L).
Structure of L. As shown in Figure 1, the pyridine ring and and the benzene ring is 51.17o, which is larger than that of L.
the benzene ring display an almost co-planar configuration The one-dimensional chain structure forms from the interac-
with dihedral angle of ꢀ6.44ꢀ. The bond lengths of L, such as tions of Ni(L)2(SCN)2 molecules, as shown in Figure 4. As
ꢀ
C(20)-N(3) (1.440 (6)ꢀA), N(3) D C(24) (1.369 (3) A), and C shown that the adjacent molecules are stacked through C(2)-
(24)-C(25) (1.453 (6) A), revealed that there is a highly p-elec- H(2). . .S(1) (symmetry codes: x – 1/2, Cy – 1/2, –z C 1/2
ꢀ
tron delocalized system within the ligand molecule. The one- C1) (H. . .S is 2.965 A and the angle is 130.23ꢀ) hydrogen
dimensional chain structure of L is shown in Figure 2, it can bond interactions.
be seen that the adjacent molecules are stacked through C(2)-
ꢀ
H(2A). . .O(2) (H. . .O is 2.6635 A and the angle is 165.62o)
(symmetry codes: x, Cy-1, Cz) hydrogen bond interactions.
Structure of Ni(L)2(SCN)2. In the asymmetric unit of the
molecular structure (shown in Figure 3) contains two inde-
pendent molecules. The bond lengths and angles in the two
Schiff base ligands are similar for each other. It can be seen
that the nickel atom is in a distorted octahedral coordination,
and the nickel was coordinated by two Schiff base ligands
and two SCN¡ ions. The bond distance Ni(1)-N(2) (2.113 (5)
ꢀ
ꢀ
ꢀ
A), Ni(1)-N(4) (2.136 (4) A), and Ni(1)-N(7) (2.005 (6) A) are
very similar. This distorted octahedral coordination geometry
is fairly regular with the six bond angles close to 90ꢀ around
the metal center. The bond lengths of Ni(L)2(SCN)ꢀ2, such as
ꢀ
C(22)-N(4) (1.414 (6)ꢀA), N(4) D C(25) (1.256 (6) A), and C
(25)-C(26) (1.462 (8) A), revealed that there is a highly p-elec-
tron delocalized within the molecule compared with L. On
Fig. 6. Molecular orbital energy diagram for L and Ni
the other hand, the dihedral angle between the pyridine ring (L)2(SCN)2.

900
Chen et al.
suggested that the high-energy transitions were mainly
Table 4. Calculated leaner absorption properties (nm), excitation
energy (eV), oscillator strengths, and major contribution for L ptriphenylamine!p*
transition, while the low-
energy transition was attributed to p!p* transition for L
triphenylamine
and Ni(L)2(SCN)2
and LMCT transition for Ni(L)2(SCN)2.
Oscillator
Compound DE1 λ (nm)bb strengths
Nature of
aa
the transition
L
2.996
4.209
2.703
4.223
413
294
458
293
0.785
0.063
0.014
0.002
116(HOMO)!
Funding
117(LUMO)(0.65)
116(HOMO)!
This work was supported by a grant for the National Natural
Science Foundation of China (51372003, 21271003,
21271004), the Natural Science Foundation of Anhui Prov-
ince (1208085MB22).
121(LUMOC5)(0.60)
264(HOMO-6)!
271(LUMO)(0.54)
269(HOMO-1)!
277(LUMOC6)(0.52)
Ni(L)2
(SCN)2
aThe energy gap of the single-photon absorption band.
bPeak position of the linear absorption band.
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tion at 410 nm, which originates from p!p* transition or
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294 nm correspond to the HOMO!LUMOC5 for L, which
can be assigned to ptriphenylamine!p*
transition.
triphenylamine
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(L)2(SCN)2. This band mainly originates from transitions of
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A novel ligand L and its mononuclear nickel complex Ni
(L)2(SCN)2 have been synthesized and confirmed by a single-
crystal X-ray diffraction analysis. The photophysical proper-
ties of them were investigated and interpreted on the basis of
theoretical calculations (TD-DFT). TD-DFT calculations

Nickel Complex
901
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