172
Y. Zhao et al. / Journal of Molecular Structure 1181 (2019) 171e178
hindrance, as depicted in Scheme 1. Promising emissive perfor-
mance is anticipated from this Cu(I) complex, [Cu(FPO) (PPh ]BF
considering its bulky and electron-pulling ligands. [Cu(FPO)
PPh ]BF is then doped into poly (vinylpyrrolidone) (PVP) host
through electrospinning method. A systematical comparison be-
tween solution sample, solid state sample and electrospinning
samples is commenced, so that polymer immobilization effect on
MLCT structural relaxation could be proved.
6 5 5
C H N , 147.0; found, 147.4.
A mixture of TP (10 mmol), 4-fluorobenzoyl chloride (11 mmol)
and pyridine (30 mL) was heated at 120 C for 2 days under N
protection. Crushed water ice was then added. Crude product was
purified on a silica gel column (n-hexane:CH
3
)
2
4
,
ꢀ
2
(
3
)
2
4
1
2
Cl
2
¼ 30:1). HNMR
(300 MHz, CDCl ): 7.51 (1H, m), 7.62 (2H, m), 8.05 (1H, m), 8.29
3
d
(1H, t), 8.36 (1H, t), 8.42 (1H, d, J ¼ 6.0), 8.89 (1H, d, J ¼ 3.5). MS m/z:
þ
[m] calc. for C13
H
8
N
3
OF, 241.1; found, 241.6.
2
. Experimental details
3 2 4
2.3. Synthesis of [Cu(FPO) (PPh ) ]BF
2
.1. General information
By refluxing Cu(BF
Cu(CH CN) ]BF was synthesized and used as a starting chemical
[19]. Then a mixture of [Cu(CH CN) ]BF (1 mmol), PPh (2 mmol)
and CH Cl (10 mL) was stirred at ambient condition for half an
4 2
) and Cu powder in MeCN solution,
[
3
4
4
Scheme 1 shows molecular structure of [Cu(FPO) (PPh
3
)
2
]BF
4
3
4
4
3
and preparation route for its composite fibers [Cu(FPO) (PPh
3
)
2
]
2
2
4
BF @PVP. Chemicals for organic synthesis were bought from
hour. FPO (1 mmol) was added. This resulting solution was stirred
Douxun Chemical Co. (China) and used with no further purifica-
tions, including Cu powder, 4-fluorobenzoyl chloride, picolinoni-
for another 1 h and then filtered off. Natural evaporation of solvent
1
gave [Cu(FPO) (PPh
3
)
2
]BF
4
bulk crystals. HNMR:
d
7.29 (18H, m),
trile, ZnCl
PPh ). Solvents were bought from Dashun Chemical Co. (China)
and redistilled before usage, including CH
thylformamide (DMF), pyridine, MeCN and water.
2
, NaN
3
, Cu(BF
4
)
2
, PVP (K30) and triphenylphosphane
7.34 (4H, m), 7.44 (8H, m), 7.61, (1H, t), 7.93 (2H, d, J ¼ 6.0), 8.08 (1H,
þ
(
3
t), 8.19 (1H, d), 8.39 (1H, t), 8.46 (1H, m), 8.91 (1H, m). MS m/z: [m]
0
Cl
2
,
N,N -dime-
calc. for C49
5 3 2
H38BCuF N OP , 915.2; found, 915.6.
2
Samples were characterized on below equipments. For NMR and
mass spectra, a Varian INOVA 300 spectrometer and an Agilent
2.4. Construction of composite fibers [Cu(FPO) (PPh ) ]BF @PVP
3 2 4
1
100 MS spectrometer (COMPACT) were adopted. UVeVis absorp-
Composite fibers [Cu(FPO) (PPh
through electrospinning method by doping [Cu(FPO) (PPh
3
)
2
]BF
4
@PVP were constructed
]BF
tion and emission spectra were measured with a HP 8453
UVeViseNIR diode array spectrophotometer and a Hitachi F-7000
fluorescence spectrophotometer, respectively. Emissive decay life-
times were measured by a two-channel TEKTRONIX TDS-3052
oscilloscope, using pulsed YAG laser (355 nm) as excitation
source. Sample morphology was obtained by a Hitachi S-4800
microscope and a Nikon TE2000-U fluorescence microscopy. Single
crystal structure was analyzed on a Siemens P4 single-crystal X-ray
diffractometer and a Smart CCD-1000 detector, using graphite-
3
)
2
4
into PVP host with various doping levels. A typical run is described
as follows. PVP was dissolved into DMF to form a transparent so-
lution (5 mL, 20 wt%). Then dopant was carefully weighted and
added. After being well mixed, this solution was poured into a glass
syringe equipped with a plastic needle (inner diameter ¼ 0.6 mm).
A piece of copper wire was connected to the anode terminal of a
high-voltage generator with driving voltage of 18 kV. The other end
of this copper wire was soaked into the glass syringe. A sheet of Al
foil was placed beneath this glass syringe with tip-to-target dis-
tance of 25 cm, serving as a collecting board.
monochromated Mo Ka radiation at 298 K. H atoms were calcu-
lated. Theoretical analysis was performed on this single crystal with
GAMESS at RB3LYP/SBKJC level in vacuum. Its FMO graphical pre-
sentation was plotted with wxMacmolplt software package under
contour value of 0.025.
3. Results and discussion
3.1. Single crystal structure of [Cu(FPO) (PPh
3
)
2
]BF
4
2.2. Synthesis of diamine ligand FPO
The successful synthesis of [Cu(FPO) (PPh
3
)
2
4
]BF is confirmed by
Firstly, 2-(2H-tetrazol-5-yl)-pyridine was prepared following
its single crystal structure shown in Fig.1A. Its Cu center is localized
at the center of a typical tetrahedral coordination environment,
surrounded by two N atoms from a FPO ligand and two P atoms
below procedure [15]. Below reagents were mixed together and
stirred at room temperature for 60 min, including NaN (10 mmol),
picolinonitrile (5 mmol) and DMF (25 mL). ZnCl (1 g) was carefully
added during this time period. This resulting solution was allowed
3
3
from two PPh ligands. The s bonds connect pyridine ring, oxa-
2
diazole ring and 4-fluorobenzoyl ring and form a large conjugation
plane in FPO ligand. Its electron-pulling oxadiazole and fluorine
groups may slow down non-radiative decay of MLCT excited state,
improving emissive performance. FPO conjugation plane shows its
ꢀ
to react at room temperature for 1 h and then at 95 C for another
0 h under N protection. Crushed water ice was then added. Crude
product was purified on silica gel column (n-hex-
1
2
a
1
ane:CH
2
Cl
2
¼ 50:1). H NMR (300 MHz, CDCl
3
):
d
7.70 (1H, m), 8.03
face-to-face
p
-
p
attraction with a phenyl ring of PPh
3
ligand, with
þ
ꢀ
(
1H, m), 8.21 (1H, d, J ¼ 6.0), 8.71 (1H, m). MS m/z: [m] calc. for
face-to-face distance of ~3.4 Å and intersection angle of only 0.9 ,
respectively. In this case, each [Cu(FPO) (PPh
regular geometry. Similar observation has been reported in other
Cu(NeN) (PeP)] complexes with large conjugation planes in their
NeN and PeP ligands [20]. There is still inter-molecular
stacking in [Cu(FPO) (PPh ] crystal, as shown in Fig. 1B. Every two
FPO planes from neighboring [Cu(FPO) (PPh ] molecules align
3 2
) ] molecule takes a
[
p-p
3 2
)
3 2
)
exactly parallel to each other, with face-to-face distance of 3.346 Å
ꢀ
and intersection angle of 0 , respectively. Such stacking increases
rigidity of [Cu(FPO) (PPh
MLCT excited state [19].
3
)
2
] and shall limit structural relaxation of
3 2
Key structural parameters of [Cu(FPO) (PPh )
] are listed in
Table 1. It is observed that this coordination field is obviously dis-
torted by its heterogeneous ligands, which are N-based FPO and P-
Scheme 1. Molecular structure of [Cu(FPO) (PPh
Cu(FPO) (PPh ]BF @PVP.
3 2 4
) ]BF and preparation route for
[
3
)
2
4