Synthesis, spectroscopic and electrochemical property of an unsymmetrical porphyrin and its Zn compound

Article abstract of DOI:10.1016/j.cclet.2010.03.037

In this article, a new 5-( p-maleicaminophenyl)-10,15,20-triphenylporphyrin (H₂P) and relative zinc compound (ZnP) were synthesized and characterized by means of elemental analyses, UV-vis, IR, MS and ¹H NMR spectroscopies. Furthermo

Full text of DOI:10.1016/j.cclet.2010.03.037

Available online at www.sciencedirect.com
Chinese Chemical Letters 21 (2010) 769–773
www.elsevier.com/locate/cclet
Synthesis, spectroscopic and electrochemical property
of an unsymmetrical porphyrin and its Zn compound
Chang Fu Zhuang, Yu Jing Zhang, Ai Qing Xia, Wen Hui Lian,
*
*
Yun Fang Wang, Ping Zhang , Tong Shun Shi
College of Chemistry, Jilin University, Changchun 130023, China
Received 29 September 2009
Abstract
In this article, a new 5-( p-maleicaminophenyl)-10,15,20-triphenylporphyrin (H2P) and relative zinc compound (ZnP) were
synthesized and characterized by means of elemental analyses, UV–vis, IR, MS and 1H NMR spectroscopies. Furthermore, we have
investigated the fluorescence spectroscopy of these compounds. The oxidation and reduction properties of the compounds were
studied by the cyclic voltammetry, the oxidation–reduction potentials were obtained.
# 2010 Tong Shun Shi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Synthesis; Porphyrin; Cyclic voltammetry; Fluorescence
In recent years, extensive effort has been devoted to designing and synthesizing various porphyrin compounds.
Especially, the diverse modification of porphyrins at the b-pyrrolic or/and meso-positions by a variety of functional
groups will bring about the exploration of new molecular devices, such as molecular wires, photovoltaic devices, light-
emitting diodes, molecular optoelectronic devices and nonlinear optical devices, etc [1–3]. Toward this goal, there
have been a number of reports on design a new class of zinc porphyrin–imide, in which an electron-donating ZnP
moiety is directly connected to an electron accepting imide moiety in the meso-position. People have recently
demonstrated that the combination of imide and porphyrin units leads to novel conjugates [4,5].
In this article, we have synthesized the H2P and ZnP. They have been characterized by elemental analyses, UV–vis
spectra, infrared spectra, mass spectra and 1H NMR spectra. Luminescence spectra and cyclic voltammetry have been
investigated.
1. Experimental
1H NMR spectra were recorded on a Varian MERCORY-300 (300 MHz) NMR spectrometer. Elemental
analyses were measured by a Perkin-Elmer 240 C auto elementary analyzer. UV–vis spectra were collected on a
Shimadzu UV-365 spectrometer. Infrared spectra were recorded on a Nicolet 5PC-FT-IR spectrometer in the region of
* Corresponding authors.
E-mail address: tsshi@email.jlu.edu.cn (T.S. Shi).
1001-8417/$ – see front matter # 2010 Tong Shun Shi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.03.037

770
C.F. Zhuang et al. / Chinese Chemical Letters 21 (2010) 769–773
Scheme 1. Synthetic route of the H2P and ZnP.
4000–400 cmꢀ1. Redox potentials were determined at room temperature by cyclic voltammetry with a CHI 660A
electrochemical analyzer. Fluorescence spectra were recorded with a SPEX Fluorolog-2T2 spectrofluorometer.
All reagents and solvents were of the commercial reagent grade and were used without further purification except
˚
DMF was predried over activated 4 A molecular sieve and vacuum distilled from calcium hydride (CaH2) prior to use.
The synthetic route of the target compound is depicted as shown in Scheme 1.
MATPP was synthesized according to the published procedure [6].
MATPP (210 mg) and maleic anhydride (30 mg) were dissolved in 18 mL anhydrous dimethylformamide. The
mixture solution was stirred and refluxed for 13 h under nitrogen atmosphere. After being cooled to room temperature,
the mixture was diluted with chloroform and washed with the deionized water (3ꢁ 150 mL). After the organic solution
was dried by sodium sulfate, the filtered solution was reduced to a smaller volume on a rotary evaporator. The product
was purified by means of chromatography on silica gel column with chloroform as the eluent. The porphyrin H2P was
obtained in about 38.5% yield. 1H NMR (CDCl3): d 8.823–8.893 (m, 8H, b-pyrrole), 8.307–8.346 (m, 2H, o-phenyl),
8.187–8.248 (m, 6H, o-triphenyl), 7.718–7.799 (m, 9H + 2H, p/m-triphenyl + m-phenyl), 7.005 (s, 2H, –CH CH–),
ꢀ2.783 (s, 2H, pyrrole N–H). MS: m/z 709.7[M]+; Elemental analyses: C48H31N5O2 (709.81), Calcd. C: 81.22, H:
4.40, N: 9.87; found: C: 81.16, H: 4.62, N: 9.74.
ZnP was prepared by the reaction of the H2P (0.20 g) and Zn (Ac)2 (2.00 g) in the mixture solution of CHCl3
(20 mL) and MeOH (10 mL) at 70 8C under nitrogen atmosphere for about 0.5 h. The extent of the reaction was
monitored by measuring the UV–vis spectrum of the reaction solution. The reaction mixture then was
chromatographed on silica gel column with chloroform as the eluent giving the ZnP as a purple red solid (yield
81.0%). Elemental analyses: C48H29N5O2 Zn, Calcd. C: 74.57, H: 3.78, N: 9.06; found: C: 74.15, H: 3.82, N: 8.94.
2. Results and discussion
1
1
From the H NMR spectra of the H2P, the H NMR chemical shift values in deuterium CDCl3 for ligand are at
8.823–8.893 (m, 8H, b-pyrrole), 8.307–8.346 (m, 2H, o-phenyl), 8.187–8.248 (m, 6H, o-triphenyl), 7.718–7.799 (m,
9H + 2H, p/m-triphenyl + m-phenyl), 7.005 (s, 2H, –CH CH–), ꢀ2.783 (s, 2H, pyrrole N–H). The characteristic inner
NH of the basic porphyrin hole and b-pyrrole chemical shifts are found at ꢀ2.783 and 8.823–8.893 ppm, respectively.
In the ZnP, the signal peak at ꢀ2.783 (2H, pyrrole N–H) disappears, because the hydrogen atom in the N–H bond is
replaced by zinc ion. Other peaks of the ZnP are similar to the H2P.
In the mass spectra (Fig. 1), the molecular ion peak of the H2P is 709.7.
Fig. 2a shows the UV–vis spectra of the H2P and ZnP at room temperature in CHCl3. The UV–vis absorption bands
of the porphyrin are due to the electronic transitions from the ground state (S0) to the two lowest singlet excited states
S1 (Q state) and S2 (B state) [7]. The S0 ! S1 transition gives rise to the weak Q bands in visible region while S0 ! S2
transition produces the strong Soret band in near UV region. In this work, the absorption bands of the H2P appear at
420, 520, 555, 595 and 650 nm. The ZnP has an intense Soret band at 420 nm; with Q bands appear at 510, 550 and
595 nm. Compared with the H2P, the number of the absorption bands of the ZnP decrease, which attributed to
symmetry increase of the ZnP [8].
The IR spectra of H2P and ZnP show in Fig. 2b. They display characteristic IR absorptions which are helpful to
identify the functional groups, the IR bands at 3315, 966 cmꢀ1 of the H2P are due to the N–H stretching and bending
vibration of the porphyrin core, but they disappear in ZnP because the hydrogen atom in the N–H bonding is replaced
by zinc ion to form Zn–N bond [9]. Compared with the H2P, a new band appears at about 1003 cmꢀ1 in the IR spectrum
of the ZnP. In addition, the intense bands at 1717 cmꢀ1 of the H2P and 1705 cmꢀ1 of the ZnP assign to symmetric C O
stretching vibrations from imido groups.

C.F. Zhuang et al. / Chinese Chemical Letters 21 (2010) 769–773
771
Fig. 1. Mass spectra of H2P.
Fig. 2. UVꢀvis (a) and IR (b) spectra of H2P and ZnP.
Fig. 3a shows the excitation spectra of H2P and ZnP at room temperature in CHCl3 and the excitation wavelength is
650 nm. In the 400–700 nm regions, the excitation spectra of H2P and ZnP follow the absorption spectra well,
indicating that they are corresponding to similar electron transition process.
Fig. 3b shows the emission spectra of H2P and ZnP in CHCl3 and the excitation wavelength is 420 nm. The
fluorescence of the B band is attributed to the transition from the second excited singlet state S2 to the ground state S0,
S2 ! S0, which is much weaker than that of the S1 ! S0 transition of the Q band emission [10]. Fluorescence of S1
consists of two bands, Q (0–1) bands are at 649 and 594 nm and Q (0–2) are at 716 and 646 nm of H2P and ZnP,
respectively. These spectra are approximately mirror symmetric to the absorption spectra.
Quantum yields of the Q bands depend on the relative rates of radiative process S1
processes S1 S0 and S1 Tn. According to the known result, the fluorescence quantum yields of the porphyrin
complexes are low [11]. The fluorescence quantum yields of H2P and ZnP are 0.096 and 0.089, respectively. In our
experiment, because the spin forbidden process S1 Tn plays a predominant role in radiation absent deactivation
of S1 in porphyrin complexes, the fluorescence quantum yields of complexes are much less than 0.21 [11].
S0 and two radiationless

772
C.F. Zhuang et al. / Chinese Chemical Letters 21 (2010) 769–773
Fig. 3. Excitation (a) and emission (b) spectra of H2P and ZnP in 10–5 mol/L CHCl3. (a. lem = 650 nm and b. lex = 420 nm).
Fig. 4. Cyclic voltammetric of H2P and ZnP.
Cyclic voltammograms of the H2P in DMF containing 0.1 mol dmꢀ3 TBAP as supporting electrolyte is shown in
Fig. 4. The redox potentials for MATPP and H2P are summarized in Table 1.
The H2P undergoes one reversible oxidation at Ep = 0.72 Vand two reversible reductions at E1/2 = ꢀ1.47 Vand E1/
2 = ꢀ1.92 V. The redox half wave potentials corresponding to the porphyrin ring reaction of the ZnP is located at E1/
2 = 0.66, 0.43, ꢀ1.78, ꢀ2.23 V. The difference of H2P and ZnP in E1/2’s between the first ring oxidation yielding p
cation radicals and the first ring reduction yielding p anion radicals is 2.19 and 2.21 V, and the difference between the
ox
red
first and second ring reduction is 0.45 and 0.45 V, which are in good agreement with E ð1Þ ꢀ E ð1Þ ¼
1=2
1=2
red
1=2
red
1=2
2:25 ꢂ 0:15 V; E ð1Þ ꢀ E ð1Þ ¼ 0:42 ꢂ 0:05 V [12].
Table 1
The redox potentials of MATPP, H2P and ZnP (V).
Compound
Ring oxidation
Ring reduction
1st
1st
2nd
MATPP [13]
H2P
0.70
0.72
0.43
ꢀ1.49
ꢀ1.47
ꢀ1.78
ꢀ2.00
ꢀ1.92
ꢀ2.23
ZnP

C.F. Zhuang et al. / Chinese Chemical Letters 21 (2010) 769–773
773
Comparing the redox potentials of H2P with MATPP, all the values of the former are shifted obviously toward
positive potentials. The reason for this is that the formation of maleimide onto tetraphenylporphyrin instead of
electron-donating group, amido, decreases the electron density of the p-ring system and the energy of both the HOMO
and the LUMO, which makes them more difficult to oxidize and easier to reduce than the corresponding monomeric
species.
Acknowledgment
This project was supported by the National Science Foundation of China (No. 20801022).
References
[1] R.A. Marcus, N. Sutin, Biochem. Biophys. Acta 811 (1995) 265.
[2] S. Kawano, S. Tamaru, N. Fujita, et al. Chem. Eur. J. 10 (2004) 343.
[3] M.W. Lan, S. d’Vries, P.M. Loccoz, et al. Chem. Rev. 102 (2002) 1201.
[4] N.P. Redmore, I.V. Rubtsov, M.J. Therien, Inorg. Chem. 41 (3) (2002) 566.
[5] N. Mataga, S. Taniguchi, H. Chosrowjan, Chem. Phys. 295 (2003) 215.
[6] N. Yoshida, T. Ishizuka, K. Yofu, Chem. Eur. J. 9 (2003) 2854.
[7] M.H. Qi, G.F. Liu, Solid State Sci. 6 (2004) 287.
[8] W.D. Horrocks Jr., C.P. Wong, J. Am. Chem. Soc. [J] 98 (1976) 7157.
[9] W. Liu, Y.H. Shi, T.S. Shi, Chem. J. Chin. Univ. 24 (2003) 200.
[10] L.A. Martarano, C.P. Wong, W.D. Horrocks, J. Phys. Chem. 80 (1976) 2399.
[11] D.J. Quimby, F.R. Longo, J. Am. Chem. Soc. 97 (1975) 5111.
[12] K.M. Kadish, E.V. Caemelbecke, J. Solid State Electrochem. 7 (2003) 254.