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C.A. WIJeSInghe et al.
1
alumina column. H NMR (300 MHz; CDCl3): δH, ppm
while the MEP and frontier orbitals were generated using
GaussView program. The mass spectra of the newly syn-
thesized compounds were recorded on a Varian 1200L
Quadrupole MS using APCI mode in dry CH2Cl2.
-2.69 (2H, s (br), pyrrole-NH), 3.5 (3H, s, 5-OCH3), 3.9
(3H, s, 2-OCH3), 7.0–7.16 (12H, m, N-ph), 7.26–7.36
(2H, m, ph), 7.38–7.56 (24H, m, m-ph and N-ph), 7.61
(1H, m, ph), 8.1 (6H, m, o-ph), 8.80–9.0 (8H, m, pyr-
role-H). MS (ESI): m/z 1175.49 (calcd. 1176.41).
Flash-photolysis method was used to study time-
resolved absorption in microsecond time-scale. The
experiments were carried out with a modified Luzchem
laser flash system (mLFP111 prototype from Luzchem
Co.) using the third harmonic of Nd:YAG laser providing
30 ns pulses at 355 nm for excitation. Excitation power
density was roughly 6 mJcm-2. A continuous Xe-lamp
(Oriel Simplesity Arc Source) was used to provide moni-
toring light and the signal was recorded with a digitiz-
ing oscilloscope (Tektronix, TDS3032B, 300 MHz). The
system was controlled with a PC computer. The samples
were deoxygenated by nitrogen bubbling for 20 min prior
to the measurements and a nitrogen flow was maintained
on the surface of the solution during the measurements.
All measurements were carried out at room temperature.
Pump-probe technique for time-resolved absorp-
tion was used to detect the fast processes with a time
resolution shorter than 0.2 ps. The fundamental of the
Ti:sapphire laser (TiF-50, CDP Corp.) pumped by Nd-
YAG CW laser (Verdi-6, Coherent Inc.) was split in two:
A part of the beam went through a second harmonic
generator to obtain excitation at 410 nm (pump), and the
other part was passed through a cuvette filled with water
generating a white continuum for monitoring (probe) the
changes in absorption. Before focusing on the rotating
sample cuvette, the pump beam was passed through an
adjustable delay line, which was scanned to obtain tran-
sient absorption signals up to approximately 1 ns after
the excitation. A CCD camera was used to detect the dif-
ferential absorption spectra at different delay times, and
from these the transient absorption decay curves were
drawn at different wavelengths. Exponential fitting of the
absorption decay curves was done globally for the mea-
sured wavelength range for both pump-probe and flash-
photolysis results. The data analysis procedure has been
described in more detail earlier [27].
Up-conversion instrument (FOG-100, CDP Corp.) for
time-resolved fluorescence was used to detect the fast
processes with a time resolution of ~200 fs. The same
Ti:sapphire generator used for pump-probe was used
to excite (~410 nm) the sample solution in a rotating
cuvette [27]. Emission from the sample was collected to
a nonlinear crystal (NLC), where it was mixed with the
so-called gate pulse, which was the laser fundamental.
The signal was measured at a sum frequency of the gate
pulse and the selected emission maximum of the sam-
ple. The gate pulses were passed through a delay line
so that it arrived at NLC at a desired time after sample
excitation. Scanning through the delay line the emission
decay curve of the sample was detected. Exponential fit-
ting of the fluorescence decay curve was carried out in
a similar manner as for the transient absorption decay
curves [27].
5-[phenyl(2,5-dione)]-10,15,20-tri-N,N-diphenyl-
porphyrin. A 9 mL solution of BBr3 (1 M in CH2Cl2) was
drop wise added to a solution of 5-[2,2′-(2,5-dimethoxy)]-
10,15,20-tri-N,N-diphenylporphyrin (1.0 mmol) in CH2Cl2
at -78 °C. The solution was maintained at this temper-
ature until the addition was completed and stirred at
room temperature under oxygen for 12 h in dark. Then
the mixture was brought to below 5 °C and 100 mL of
cold water was added followed by addition of saturated
sodium bicarbonate. After stirring 1 h at room tempera-
ture the organic layer was separated using CH2Cl2 and
dried over anhydrous Na2SO4. The solvent was evapo-
rated and the crude product was purified on silica col-
umn. 1H NMR (300 MHz; CDCl3): δH, ppm -2.70 (2H, s
(br), pyrrole-NH), 7.26–7.31 (12H, m, N-ph), 7.39–7.48
(2H, m, ph), 7.48–7.55 (24H, m, m-ph and N-ph), 7.60
(1H, m, ph), 8.05–8.15 (6H, m, o-ph), 8.90–9.05 (8H, m,
pyrrole-H). MS (ESI): m/z 1145.44 (calcd. 1146.34).
Zinc 5-[phenyl(2,5-dione)]-10,15,20-tri-N,N-diphenyl-
porphyrin, 1. A 0.0125 mmol of free base porphyrin
was dissolved in 30 mL of CHCl3, and an excess of zinc
acetate (50 equiv.) in methanol was added. The course
of the reaction was monitored spectroscopically. At the
end of the reaction (1 h), the solvent was evaporated and
1
the product was purified on silica gel column. H NMR
(300 MHz; CDCl3): δH, ppm 7.26–7.31 (12H, m, N-ph),
7.39–7.48 (2H, m, ph), 7.48–7.55 (24H, m, m-ph and
N-ph), 7.60 (1H, m, ph), 8.05–8.15 (6H, m, o-ph), 8.90–
9.05 (8H, m, pyrrole-H). MS (ESI): m/z 1207.36 (calcd.
1209.73).
Instrumentation
The UV-visible spectral measurements were carried
out with a Shimadzu Model 1600 UV-visible spectropho-
tometer. The fluorescence emission was monitored by
using a Varian Eclipse spectrometer. A right angle detec-
tion method was used. The 1H NMR studies were carried
out on a Varian 400 MHz spectrometer. Tetramethylsi-
lane (TMS) was used as an internal standard. Differen-
tial pulse voltammetry was recorded on a EG&G model
263A Potentiostat/Galvanostat using a three electrode
system. A platinum button electrode was used as the
working electrode. A platinum wire served as the coun-
ter electrode and a Ag/AgCl electrode was used as the
reference electrode. Ferrocene/ferrocenium redox couple
was used as an internal standard. All the solutions were
purged prior to electrochemical and spectral measure-
ments using argon gas. The computational calculations
were performed by DFT B3LYP/3-21G(*) methods with
GAUSSIAN 03[22] software package on high speed PCs
Copyright © 2011 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2011; 15: 398–400