B. Cheng / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 239 (2020) 118537
3
response towards O2 is systematically explored. The correlation be-
tween ligand structure and Cu(N\\N)(P\\P) photophysical feature is
tentatively discussed as well.
2H), 9.21 (m, 4H), 8.45 (dd, 1H, J = 2.0, 9.0 Hz), 7.97 (m, 2H), 7.74
(m, 2H), 7.22 (m, 2H), 2.44 (s, 3H). MS m/z: [m]+, found 440.1.
2.3. Synthesis of [Cu(N\\N)(P\\P)]BF4 complexes (N-N=L1, L2, L3, P-
P=POP or (PPh3)2)
2. Experiment section
[Cu(N\\N)(P\\P)]BF4 complexes of this work were synthesized fol-
lowing a literature protocol [12]. A brief description is given as follows.
A CH2Cl2 solution (15 mL) containing [Cu(CH3CN)4]BF4 (10 mmol) and
P\\P ligand (POP 10 mmol or PPh3 20 mmol) was stirred at ambient
condition for 30 min. This solution was filtered before adding N\\N li-
gand (10 mmol) into it. Then this mixture was stirred for another
30 min, and ethanol (10 mL) was added. The final solution was filtered
again and allowed to vaporize naturally. Solid bulk was obtained.
2.1. General information
The synthetic route for these Cu(N\\N)(P\\P) complexes and their
oxygen sensing composites [Cu(N\\N)(P\\P)]BF4/MCM-41 is shown
in Scheme 1. Starting compounds were AR grade ones and used as re-
ceived, including Cu(CH3CN)4BF4, PPh3, bis[2-(diphenylphosphino)
phenyl] ether (POP), 1,10-phenanthroline (Phen), KBr, H2SO4, HNO3,
benzene-1,2-diamine, dipyrido[3,2-a:2′,3′-c]phenazine-11-carboxylic
acid, benzohydrazide, 4-methylbenzohydrazide and POCl3. Equipment
for sample characterization is listed as follows. NMR and MS data
were collected by a Bruker DMX 500 spectrometer and a Varian Prostar
spectrometer. Photophysical spectra were recorded using a Unico UV-
2600 spectrophotometer and a Shimadzu RF-5310PC spectrophotome-
ter. Excited state lifetime was determined via an Edberg FL920 spec-
trometer, excited by H lamp. Single crystal data were collected via a
Siemens P4 single-crystal X-ray diffractometer (Mo Kα radiation at
298 K). Powder XRD diffraction patterns were recorded using a Rigaku
X-ray diffractometer. Porous parameters were determined by a
Micromeritics ASAP2010N analyzer. Theoretical calculation was per-
formed using GAMESS at RB3LYP/SBKJC level, with single crystal struc-
ture as initial geometry.
2.3.1. [Cu(L1)(PPh3)2]BF4
1H NMR(CDCl3): δ 9.59 (d, 2H), 9.17 (d, 2H), 8.14 (d, 2H), 7.74 (d,
2H), 7.79 (m, 2H), 7.35 (t, 11H), 7.24 (m, 4H), 7.22 (m, 4H), 7.05 (m,
8H), 6.61 (m, 3H). MS m/z: [m]+, found 956.1.
2.3.2. [Cu(L2)(PPh3)2]BF4
1H NMR(CDCl3):δ 9.42 (m, 2H), 9.21 (m, 2H), 8.40 (m, 1H), 7.94 (m,
2H), 7.73 (m, 2H), 7.34 (t, 11H), 7.25 (m, 8H), 7.20 (m, 5H), 7.02 (m,
8H), 6.60 (m, 3H). MS m/z: [m]+, found 1100.2.
2.3.3. [Cu(L3)(PPh3)2]BF4
1H NMR(CDCl3):δ 9.46 (m, 2H), 9.23 (m, 4H), 8.44 (m, 1H), 7.96 (m,
2H), 7.75 (m, 2H), 7.34 (t, 11H), 7.25 (m, 4H), 7.21 (m, 6H), 7.04 (m,
8H), 6.62 (m, 2H), 2.45 (s, 3H). MS m/z: [m]+, found 1114.3.
2.2. Synthesis of ligands L1, L2 and L3
2.3.4. [Cu(L1)(POP)]BF4
1,10-phenanthroline-5,6-dione (Phen-O) was firstly synthesized
and used as a starting material in accordance with a classic method,
by treating Phen with HNO3 in the presence of concentrated H2SO4
and KBr [9]. Yellow needles were obtained. 1H NMR (CDCl3): δ 9.10
(2H, J = 5.0 Hz), 8.51 (2H, J = 8.0 Hz), 7.63 (2H, J = 5.0 Hz, 8.0 Hz).
MS m/z: [m]+, found 210.1.
1H NMR(CDCl3): δ 9.57 (d, 2H), 9.19 (d, 2H), 8.15 (d, 2H), 7.73 (d,
2H), 7.78 (m, 2H), 7.35 (t, 11H), 7.26 (m, 4H), 7.22 (m, 2H), 7.07 (m,
8H), 6.62 (m, 3H). MS m/z: [m]+, found 970.2.
2.3.5. [Cu(L2)(POP)]BF4
1H NMR(CDCl3): δ 9.41 (m, 2H), 9.21 (m, 2H), 8.43 (m, 1H), 7.95 (m,
2H), 7.73 (m, 2H), 7.35 (t, 11H), 7.23 (m, 8H), 7.22 (m, 5H), 7.02 (m,
6H), 6.61 (m, 3H). MS m/z: [m]+, found 1114.2.
2.2.1. L1
Dipyrido[3,2-a:2′,3′-c]phenazine (L1) was synthesized with Phen-O
and benzene-1,2-diamine as starting chemicals [9]. Their mixture was
heated in ethanol for 10 h. Crude product was purified in hot ethanol
to give light brown needles. 1H NMR (CDCl3): δ 9.64 (2H, J = 8.0 Hz),
9.24 (2H, J = 8.0 Hz), 8.35 (2H, J = 6.5 Hz), 7.95 (2H, J = 6.5 Hz),
7.88 (2H, J = 8.0 Hz). MS m/z: [m]+, found 282.0.
2.3.6. [Cu(L3)(POP)]BF4
1H NMR(CDCl3): δ 9.44 (m, 2H), 9.25 (m, 4H), 8.43 (m, 1H), 7.94 (m,
2H), 7.72 (m, 2H), 7.31 (t, 11H), 7.27 (m, 6H), 7.21 (m, 4H), 7.02 (m,
6H), 6.64 (m, 3H), 2.45 (s, 3H). MS m/z: [m]+, found 1128.2.
2.2.2. Phen-COOH
2.4. Synthesis of [Cu(N\\N)(P\\P)]BF4/MCM-41 (N-N = L1, L2, L3, P-
Dipyrido[3,2-a:2′,3′-c]phenazine-11-carboxylic acid (Phen-COOH)
was synthesized following a similar protocol to that for L1 [9]. However,
benzene-1,2-diamine was replaced by 3,4-diaminobenzoic acid in this
run. 1H NMR (CDCl3): δ, 9.61 (d, 2H, J = 8.0 Hz), 9.25 (d, 2H, J =
8.0 Hz), 8.22 (m, 1H), 7.94 (d, 2H, J = 6.5 Hz), 7.80 (m, 2H). MS m/z:
[m]+, found 326.1.
P=POP or (PPh3)2)
The final oxygen sensing samples, denoted as [Cu(N\\N)(P\\P)]BF4/
MCM-41, were synthesized following a literature protocol [12]. A brief
explanation is given as follows. First, [Cu(N\\N)(P\\P)]BF4 transparent
solution in CH2Cl2 (5 mL) was prepared and stirred at room tempera-
ture. Then MCM-41 spheres (1 g) were added and stirred gently for an-
other 120 min. The resulting powder sample was collected and washed
with ethanol to remove surface residue, and dried in vacuum at room
temperature.
2.2.3. L2
2-(dipyrido[3,2-a:2′,3′-c]phenazin-11-yl)-5-phenyl-1,3,4-
oxadiazole (L2) was synthesized by treating Phen-COOH and
benzohydrazide with POCl3 solution [10]. 1H NMR (CDCl3): δ, 9.45 (m,
2H), 9.24 (m, 4H), 8.43 (dd, 1H, J = 2.0, 9.0 Hz), 7.95 (m, 2H), 7.77
(m, 2H), 7.24 (m, 2H), 7.21 (m, 1H). MS m/z: [m]+, found 426.1.
2.5. Oxygen sensing operation
Each [Cu(N\\N)(P\\P)]BF4/MCM-41 powder sample was sealed in a
quartz chamber, equipped with a one-way valve. Pure N2 and pure O2
streams were controlled by gas meters and then mixed together before
injecting into this quartz chamber. Then this quartz chamber was placed
into a fluorescence spectrometer to record its emission spectra. Oxygen
sensing performance was evaluated based on steady emission spectra.
2.2.4. L3
2-(dipyrido[3,2-a:2′,3′-c]phenazin-11-yl)-5-(p-tolyl)-1,3,4-
oxadiazole (L3) was synthesized following a similar protocol to that for
L2, except that benzohydrazide was replaced by 4-
methylbenzohydrazide in this run [10]. 1H NMR (CDCl3): δ, 9.43 (m,