S. Jagadeeswari et al. / Journal of Photochemistry and Photobiology A: Chemistry 276 (2013) 104–112
105
OH
OH
mirrors were used to separate the third harmonic from the sec-
ond harmonic and the fundamental output of the Nd–YAG laser.
The monitoring source was a 150 W pulsed xenon lamp which was
H
3
CO
OCH
3
3
H CO
◦
focused on the sample at 90 to the incident laser beam. The beam
OCH
3
H
3
CO
OCH
OH
OCH
3
N
N
N
N
emerging through the sample was focused onto a Czerny–Turner
monochromator using a pair of lenses. The detection was carried
out using a Hamamatsu R-928 photomultiplier tube. The transient
signals were captured with an Agilent infiniium digital storage
oscilloscope interfaced to a computer.
N
N
N
N
M
OH
M
HO
HO
3
H CO
H
3
CO
3
OCH
3
H
3
CO
OCH
3
OH
OH
OH
2
.3. General synthesis of free base porphyrins and
Pn2 , ZnPn2
Pn1 , ZnPn1
metalloporphyrins
Corresponding aldehyde precursors (5.4 mmol) was dissolved
in propionic acid (54.65) and the solution was heated to 140 C. A
N
N
N
N
◦
HO
M
OH
freshly distilled pyrrole (5.4 mmol) was slowly added and refluxed
for 1 h. Under hot condition 55 ml of anhydrous alcohol was added
and the solution was transferred into beaker cooled to room tem-
◦
perature and kept 1 h at −5 C. Filtered the solution to obtain blue
powder and dried. A solution of Zn(OAc) ·2H O (2 mol) in ethanol
OH
2
2
(
1 ml) was added to the solution of free base porphyrins (1 mol) in
Pn3, ZnPn3
CHCl3 and stirred overnight at room temperatureunder N2 in the
dark. This was monitored by TLC and the mixture was washed with
water and evaporated to dryness to get desired compound.
M = 2H (Pn1, Pn2, Pn3)
Zn2+ (ZnPn1, ZnPn2, ZnPn3)
Scheme 1. Structures of porphyrins and metalloporphyrins.
2.3.1. Meso-tetrakis (4-hydroxy-3,5-dimethoxy phenyl)
porphyrin (Pn1)
obtained from Merck chemicals. Double distilled water was used for
preparing solutions. All measurements were performed at ambient
temperature. CdTe quantum dots were synthesized by using the
following method as reported earlier [20]. The quantum yield of
prepared QDs was 15%, calculated using rhodamine B as the refer-
ence.
Yield – 4.23%, color: glittering purple color, 1H NMR (400 MHz,
DMSO): ı (ppm), 8.92 (s, 8H,  pyrrole), 7.45 (s, 8H, 2,6-phenyl),
3.88 (s, 24H, OCH3), −2.47 (s, 2H, NH-pyrrole), 8.86 (s, 4H, OH).
13
C NMR (400 MHz, DMSO): 146.35, 135.61, 131.37, 120.86, 112.86,
−
1
56.27. IR (KBr, cm ): 3464, 2929, 1603, 1509, 1453, 1411, 1341,
−
1
921, 800, 730 cm . MS (MALDI) m/z calculated for C52H46N4O12
M+H): 918.31, Found: 919.23.
(
2.2. Instrumentation
2
(
.3.2. Meso-tetrakis (4-hydroxy-3-methoxy phenyl) porphyrin
Pn2)
Yield – 8.1%, color: purple powder, 1H NMR (400 MHz, DMSO):
Absorption measurements were recorded using JASCO V630
UV–visible spectrophotometer. Photoluminescence (PL) measure-
ments were carried out using Perkin Elmer LS 55 spectrofluori-
meter. The excitation and emission wavelength of TA-CdTe QDs
were 500 and 595 nm, respectively. Silt width (10 nm) and scan
rate (200 nm/min) were kept constant for all measurements.
Quartz cells (4 × 1 × 1 cm) with high vacuum Teflon stopcocks
were used for measurements. Samples for absorption and pho-
toluminescence measurements were prepared by adding various
ı (ppm), 9.51 (s, 4H, OH), 8.9 (s, 8H,  pyrrole), 7.76 (s, 4H, 2-
phenyl), 7.58-7.57 (d, 4H, 6-phenyl), 7.1-7.2 (d, 4H, 5-phenyl), 3.89
13
(
s, 12H, OCH3) −2.88 (s, 2H, NH-pyrrole).). C NMR (400 MHz,
DMSO): 146.63, 146.01, 132.34, 127.48, 120.03, 118.89, 114.03,
−1
5
1
5.85. FT-IR (KBr, cm ): 3492, 3427, 2929, 1603, 1509, 1463, 1416,
−1
341, 1229, 1262, 1117, 1033, 916, 865, 730 cm . MS (MALDI) m/z
calculated for C48H38N O (M+H): 798.27, Found: 799.02.
4
8
−5
concentration [0–5 × 10 M] of porphyrins to the test tubes con-
−6
taining QDs [1 × 10 M] and then kept as such for 1 h and
used for further experiments. Cyclic voltammogram was acquired
with Princeton EG and G-PARC model potentiostat using Glassy
carbon working electrode, Ag/AgCl reference electrode and plat-
inum wire counter electrode. Tetrabutyl ammonium hexafluoro
phosphate (0.1 M) was used as supporting electrolyte for por-
phyrins/metalloporphyrins in DMF solvent. All samples were
deaerated by bubbling with nitrogen gas for ca.5 min at room tem-
2.3.3. Meso-tetrakis (4-hydroxy phenyl) porphyrin (Pn3)
Yield – 3.1%, color: glittering green color, 1H NMR (400 MHz,
DMSO): ı (ppm), 9.96 (s, 4H, OH), 8.86 (s, 8H,  pyrrole), 7.9-
(d, 8H, 2,6-phenyl), 7.1-7.2 (d, 8H, 3,5-phenyl), −2.89 (s, 2H,
8
13
NH-pyrrole). C NMR (400 MHz, DMSO): 157.37, 135.49, 131.90,
1
1
19.97, 113.90. IR (KBr, cm 1): 3412, 3220, 1509, 1603, 1478,
−
−
1
379, 1279, 1171, 1112, 846 cm . MS (MALDI) m/z calculated for
1
13
C44H30N4O4(M+H): 678.23, Found: 679.016.
perature. H NMR and C NMR spectrum were obtained using a
Bruker spectrometer (400 MHz). FT-IR spectra were obtained by
using Perkin–Elmer Spectrum RXI FT-IR Spectrometer at room tem-
2.3.4. Zn(II)-[meso-tetrakis (4-hydroxy-3,5-dimethoxy phenyl)
porphyrin] (ZnPn1)
−1
perature in the range of 4000–400 cm
.
PL lifetime measurements were carried out in a picosecond time
correlated single photon counting (TCSPC) spectrometer. The exci-
tation source was the tunable Ti-sapphire laser (TSUNAMI, Spectra
Physics, USA). The data analysis was carried out by the software pro-
vided by IBH (DAS-6). For Laser Flash Photolysis measurements, the
Nd–YAG laser source produces nanosecond pulses (8 ns) of 532 nm
light and energy of the laser pulse was around 150 mJ. Dichroic
Yield – 68%, color: blue solid, 1H NMR (400 MHz, DMSO): ı
(ppm), 8.92 (s, 8H,  pyrrole), 7.45 (s, 8H, 2,6-phenyl), 3.88 (s, 24H,
OCH3), 8.86 (s, 4H, OH).). 13C NMR (400 MHz, DMSO): 149.53,
146.07, 135.22, 132.95, 131.49, 120.39, 112.82, 56.25. IR (KBr,
−
1
cm ): 3464, 2929, 2845, 1607, 1509, 1453, 1411, 1341, 1206, 1114,
940, 795 cm . MS (MALDI) m/z calculated for C52H44N O12Zn
(M ): 980.22, Found: 979.85.
−
1
4
+