X. Yang, Y. Li / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 153 (2016) 746–753
747
2
. Experimental details
3
2.2. Synthesis of Re(I) complex Re(CO) (POP)Br
2
.1. General information for reagents and apparatus
Synthetic route for our diamine ligand, its Re(I) complex and the
Re(I) complex Re(CO)
procedure. POP (1 mmol), Re(CO)
were mixed together under N protection, heated to reflux and kept
3
(POP)Br was synthesized following below
5
Br (1 mmol) and toluene (20 mL)
2
final composites is shown in Scheme 1. Starting compound 2-(2H-
tetrazol-5-yl)-pyridine (TP) was synthesized following a literature pro-
cedure [17]. Other reagents, such as benzoyl chloride, sodium azide,
MCM-41, zinc bromide, and Re(CO) Br, were obtained from Yunzi
5
Chemical Co. (Hangzhou) and used without further purifications. Or-
ganic solvents were purified with standard procedures.
for 6 h. After cooling, solvent was extracted by rotary evaporation. The
resulting crude product was collected and purified on a silica gel col-
umn. 1H NMR (300 MHz, CDCl
): δ 7.52 (1H, m), 7.67 (3H, m), 7.85
(1H, m), 8.24 (1H, t), 8.29 (1H, t), 8.37 (1H, d, J = 6.0), 8.87 (1H, d,
J = 4.0). Anal. Calcd. for C16 BrN Re: C, 33.52, H, 1.58, N, 7.33.
9 3 4
Found: C, 33.64, H, 1.67, N, 7.22. MS m/z: [m] calc. for C16H BrN O ,
3
H
9
3 4
O
+
NMR, MS, UV–vis absorption, and emission spectra were recorded
by a Varian INOVA 300 spectrometer, a Agilent 1100 MS series/AXIMA
CFR MALDI/TOF MS spectrometer, a Shimadzu UV-3101PC spectropho-
tometer and a Hitachi F-4500 fluorescence spectrophotometer, respec-
tively. Elemental analysis was finished on a Vario Element Analyzer.
Excited state decay dynamics were recorded by a two-channel
TEKTRONIX TDS-3052 oscilloscope, using pulsed Nd:YAG laser as exci-
tation source (λ = 355 nm). Scanning electron microscopy (SEM)
image was obtained by a Hitachi S-4800 microscope. Small-angle X-
ray diffraction (SAXRD) patterns were recorded by a Rigaku-Dmax
572.9; found, 573.0. Its identity was further confirmed by single crystal
XRD analysis (CCDC 1086734).
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2.3. Construction of composites Re(CO) (POP)Br doped MCM-41
Our sensing composites were constructed by doping various
amounts of Re(CO) (POP)Br into molecular sieve MCM-41 [17,18]. A
typical run is described as follows. Dopant Re(CO) (POP)Br was careful-
ly weighed and dissolved into CH Cl (5 mL) under stirring. When solu-
3
3
2
2
tion became clear, MCM-41 (1 g) was added into the solution and
stirred for 30 min. Then solid product was collected and washed with
CH Cl (10 mL × 3), giving Re(CO) (POP)Br doped MCM-41 as pale or-
2 2 3
2
500 diffractometer (λ = 0.154 nm, scanning step = 0.02°). Single
crystal was analyzed on a Siemens P4 single-crystal X-ray diffractome-
ter equipped with Smart CCD-1000 detector and graphite-
a
ange powder.
monochromated Mo Kα radiation (50 kV, 30 A, 298 K). All hydrogen
atoms were calculated. Density functional theory calculation was per-
formed on this single crystal by GAMESS at RB3LYP1/SBKJC level. Graph-
ical presentation for frontier molecular orbitals was generated by
wxMacMolPlt with contour value of 0.025.
3. Results and discussion
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3.1. Molecular structure of probe Re(CO) (POP)Br
Aiming at a better understanding on probe, we are giving a brief ex-
planation on its molecular structure. For a typical transition metal com-
plex, it has been found that electrons of its first excited state are
localized on diamine ligand π*, which makes them vulnerable to energy
acceptors [15–17]. As shown in Scheme 1, there is a large conjugation
plane in POP ligand. With its wide ligand π*, excited electrons may be
2
.1. Synthesis of diamine ligand POP
Diamine ligand POP was synthesized following below procedure. TP
(
(
20 mmol), benzoyl chloride (22 mmol) and anhydrous pyridine
25 mL) were mixed together under N protection, heated to reflux
2
and kept for 60 h. After cooling, cold water (200 mL) was added. The
2
readily attacked by O molecules. In addition, this large conjugation
resulting crude product was collected and purified on a silica gel col-
plane may depress non-radiative decay probability and thus improve
emission performance [13–16]. Small ligands of CO and Br are positive
umn. 1H NMR (300 MHz, CDCl
): δ 7.38 (1H, m), 7.51 (3H, m), 7.87
1H, m), 8.14 (1H, t), 8.21 (1H, t), 8.28 (1H, d, J = 6.0), 8.69 (1H, d,
J = 3.5). Anal. Calcd. for C13 O: C, 69.95; H, 4.06; N, 18.82. Found:
3
(
to decrease steric hindrance when being attacked by O
These factors make Re(CO) (POP)Br a promising oxygen sensing probe.
Above hypothesis is firstly confirmed by the single crystal structure
of Re(CO) (POP)Br shown in Fig. 1. Its key structural parameters are
2
molecules.
H N
9 3
3
+
C, 69.88; H, 4.21; N, 18.67. MS m/z: [m] calc. for C13
found, 223.0.
9 3
H N O, 223.1;
3
3 3
Scheme 1. Synthetic route for ligand POP, corresponding Re(I) complex Re(CO) (POP)Br and Re(CO) (POP)Br doped MCM-41.