X. Zhou et al. / Journal of Photochemistry and Photobiology A: Chemistry 274 (2014) 57–63
59
inductive effects of N,Nꢀ substituents relayed via the imide nitrogen
potentials.
Table 1
Half-wave redox potentials (V vs SCE), HOMO (eV) and LUMO for synthesized por-
phyrin and perylene compounds in dichloromethane.
−/2−
0/−
+/0
2+/+
Compound
E1/2
E1/2
E1/2
E1/2
HOMO
LUMO
When HTPP and PDI were linked by a triazine group, the redox
potentials of the resulted dyad HTPP–PDI exhibit only a little
change in comparison with porphyrin and perylene derivatives. As
shown in Fig. 1, the dyad shows four reversible reduction waves
(−1.71, −1.35, −0.92 and −0.69 V vs SCE in CH2Cl2), of which the
first two reduction potentials agree with those of perylene deriva-
tives and another two correspond to those of porphyrin derivatives,
together with two reversible oxidation waves (0.94 and 1.27 V
vs SCE in CH2Cl2), which are in consistence with the oxidation
potentials of porphyrin derivatives. These data suggests that the
porphyrin and perylene continue to behave as discrete units, indi-
state absorption spectra.
Table 1. Both HOMO and LUMO levels of porphyrin derivatives are
higher than those of perylene derivatives, indicating a possible elec-
tron transfer from porphyrins to perylenes. This is in consistence
with the literatures [12–20,28–30]. For the dyad HTPP–PDI, the
HOMO locates on the porphyrin moiety while the LUMO locates on
the perylene moiety, which is not overly surprising considering the
orbital energies of the two moieties.
HTPP
−1.69
−1.70
−2.03
−0.99
−0.93
−0.92
−1.32
−1.35
−1.45
−0.69
−0.69
−0.69
0.96
–
1.01
1.71
–
1.34
–
1.42
–
–
1.27
−5.70
–
−5.75
−6.45
–
−3.42
−3.39
−3.29
−4.05
−4.05
−4.05
HTPPa
HTPPt
PDI
PDIa
HTPP–PDI
0.94
−5.68
2.2.3. 5-(4-(3,5-Dichloro triazine)
aminophenyl)-10,15,20-triphenylporphyrin hydrochloride
(HTPPt)
HTPPa (25 mg, 0.04 mmol) dissolved in THF (1.0 mL) was added
into solution of cyanuric chloride (7.3 mg, 0.04 mmol) and triethyl-
amine (TEA) (4.8 mg, 0.048 mmol) in THF (2.0 mL) at 0 ◦C. After
stirring at 0 ◦C for 10 min, the solution was warmed to and then kept
at room temperature. After the reaction completed by monitoring
with thin layer chromatography (TLC), the solvent was removed
by rotary evaporation. The residue was purified by column chro-
matography on silica gel. A blue violet solid (29 mg) yielded (90.6%).
1H NMR (CDCl3, ppm), ı: 8.92–8.91 (d, J = 4.8 Hz, 2H, C4H5N -H),
8.88–8.86 (d, J = 6.0 Hz, 6H, C4H5N -H), 8.24–8.19 (m, 8H, C6H5),
8.01–7.99 (d, J = 8.0 Hz, 2H, C6H5), 7.79–7.74 (m, 10H, C6H5,
NH·HCl), 7.45 (s, 1H, NH), −2.72 (s, 2H, NH); ESI-MS (m/z): 814.4
(M+HCl)+, 777.4 (M+H)+.
3.2. Steady-state absorption properties
2.2.4. 5-{4-[3-Chloro-5-(N-(1-hexylheptyl)-Nꢀ-(4-amino)phenyl
perylene-3,4,9,10-tetracarboxylbis-imide)triazine]
The steady-state absorption spectra of the dyad along
with HTPPt, PDI, and their 1:1 mixture (HTPPt + PDI) in
dichloromethane are shown in Fig. 2. Compound HTPPt shows
a 2 nm blue-shift of the absorption spectrum together with a
little increase in the absorbance as comparing with compound
HTPP due to the induction and steric effect of 4,6-dichloro-1,3,5-
triazineamine group. This is in accordance with the increased
HOMO–LUMO energy gap from HTPP (2.28 eV) to HTPPt (2.46 eV).
So HTPPt was used to discuss the interaction between both units.
The band at about 420 nm is the Soret band of the porphyrin moiety,
ond excited state S2 generated by →* transition [31]. The Q-band
of porphyrin moiety overlaps with the absorption band of perylene
moiety in the region of 450–560 nm, leading to three absorption
maxima at 460, 493 and 529 nm [32]. The weak absorption maxima
at 594 nm and 651 nm are the rest of Q band of the porphyrin moiety
aminophenyl}-10,15,20-triphenyl porphyrin (HTPP–PDI)
To a suspension of PDI (60 mg, 0.09 mmol) in dry DMF (15 mL)
was added NaH (2.1 mg, 0.09 mmol) at 0 ◦C. As the mixture reached
room temperature, HTPPt was added. Then the mixture was heated
to and kept stirring at 80 ◦C under nitrogen for 4 h. The solvent was
removed under reduced pressure and the residue was purified by
column chromatography on silica gel. Yield of product HTPP–PDI
was 40 mg (33%). 1H NMR (CDCl3, ppm), ı: 8.89–8.56 (m, 12H),
8.19–7.47 (m, 23H), 7.25–7.27 (m, 4H), 5.14 (s, 1H), 2.20 (s, 4H),
1.97 (s, 4H), 1.59 (s, 4H), 1.27 (s, 8H), 0.86 (s, 6H), −3.53 (s, 2H, NH);
MALDI-TOF-MS (m/z): 1404.409 (M+H)+.
3. Results and discussion
3.1. Electrochemical properties
The electrochemical data for synthesized porphyrin and pery-
lene derivatives are summarized in Table 1. HTPP shows two
reversible oxidation waves (0.96 and 1.34 V vs SCE in CH2Cl2)
and two reversible reduction waves (−1.32 and −1.69 V vs SCE
in CH2Cl2). The first oxidation potential is in consistence with
the reported data (0.99 V vs SCE in CH2Cl2) [25]. HTPPa only
exhibits two reversible reduction waves due to the instability of
amino group, which gives little effect on the reduction potentials
of HTPP. However, 4,6-dichloro-1,3,5-triazineamine group in com-
pound HTPPt can obviously increase the oxidation potentials and
decrease the reduction potentials due to its electron withdrawing
and steric effects. PDI shows one reversible oxidation wave (1.71 V
vs SCE in CH2Cl2) and two reversible reduction waves (-0.99 and
−0.69 V vs SCE in CH2Cl2). The first redox potentials, which were
calculated as −1.14 and 1.26 V vs Fc/Fc+, are consistent with the
reported values of N,Nꢀ-dialkyl or diaryl perylene derivatives (at ca.
−0.98 and 1.21 V vs Fc/Fc+ in CH2Cl2) [26], indicating little effect of
the N,Nꢀ substituents on the redox potentials even in asymmetric
perylene derivatives. This is due to the location of the LUMO (and
HOMO) on the core [26], the orbital energies being modified by
20
-1.71
-1.35
10
-0.92
0
-0.69
0.94
1.27
-10
-20
-2
-1
0
1
Potential (V)
Fig. 1. Cyclic voltammetry curve of dyad HTPP–PDI in CH2Cl2 (vs SCE).