Synthesis, characterization and electrochemistry of the novel metalloporphyrazines annulated with tetrathiafulvalene having pentoxycarbonyl substituents

Article abstract of DOI:10.1142/S1088424610001787

Three novel tetrathiafulvalene-annulated metalloporphyrazines with electron-withdrawing pentoxycarbonyl groups at the periphery were synthesized via the cyclotetramerization of dipentyl 6,7-dicyanotetrathiafulvalen-2,3- dicarboxylate in the presence of corresponding metal salts (Zn(OAc) ₂·2H₂O, Cu(OAc)₂·2H₂O, and NiCl₂) and in pentanol. Molecular structures were fully characterized by ¹H NMR, FT-IR, UV-vis, MALDI-TOF mass spectra and elemental analysis. These newly synthesized macrocyclic dyes were sufficiently stable in air during the purification process and also in further experiments. Electron-withdrawing substituents reduced the ability of tetrathiafulvalene groups to form radical cations. Solution electrochemical data showed one reductive and three oxidative processes within a -2000 mV to +2200 mV potential window. The four couples observed were assigned to Pz^-2/Pz ^-3 (I), TTF^+?/TTF (II), TTF⁺²/TTF ^+? (III) and Pz^-1/Pz^-2 (IV).

Full text of DOI:10.1142/S1088424610001787

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2010; 14: 108–114
DOI: 10.1142/S1088424610001787
Published at http://www.worldscinet.com/jpp/
Synthesis, characterization and electrochemistry of the
novel metalloporphyrazines annulated with tetrathiafulvalene
having pentoxycarbonyl substituents
Fengshou Lenga, Ruibin Houa, Longyi Jina, Bingzhu Yin*a and Ren-Gen Xiong*b
a Key laboratory of Organism Functional Factors of Changbai Mountain, Yanbian University, Ministry of Education,
Yanji 133002, China
b Ordered Matter Science Research Center, College of Chemistry and Chemical Engineering, Southeast University,
Nanjing 210096, China
Received 13 April 2009
Accepted 24 June 2009
ABSTRACT:Three novel tetrathiafulvalene-annulated metalloporphyrazines with electron-withdrawing
pentoxycarbonyl groups at the periphery were synthesized via the cyclotetramerization of dipentyl 6,7-
dicyanotetrathiafulvalen-2,3-dicarboxylate in the presence of corresponding metal salts (Zn(OAc)2·2H2O,
Cu(OAc)2·2H2O, and NiCl2) and in pentanol. Molecular structures were fully characterized by 1H NMR,
FT-IR, UV-vis, MALDI-TOF mass spectra and elemental analysis. These newly synthesized macrocyclic
dyes were sufficiently stable in air during the purification process and also in further experiments.
Electron-withdrawing substituents reduced the ability of tetrathiafulvalene groups to form radical cations.
Solution electrochemical data showed one reductive and three oxidative processes within a -2000 mV to
+2200 mV potential window. The four couples observed were assigned to Pz-2/Pz-3 (I), TTF+•/TTF (II),
TTF+2/TTF+• (III) and Pz-1/Pz-2 (IV).
KEYWORDS: tetrathiafulvalenedinitrile, metalloporphyrazines, electrochemistry, tetramerization,
aggregation.
of a symmetrically-functionalized Pc with eight (TTF)
INTRODUCTION
units appeared in 1996 [7–19]. These compounds exhib-
Porphyrins and phthalocyanines (Pcs) represent a
ited interesting optical and electrical properties such as
major class of dyes and are applied extensively in bio-
photoinduced electron transfer followed by fluorescence.
logical systems and in material science because of their
This behavior results from the combination of Pc or por-
unique molecular assembly properties and excellent
phyrin units and TTF units into a single molecule. The
optical and electrical properties [1,2]. A lot of work has
unique redox properties of TTF is characterized by a
been done on the modification of the Pcs and porphyrins
sequential and reversible oxidation to a radical cation
so that they may be used for various applications [3–5].
(TTF+•) and a dication (TTF+2) [20–22]. Interestingly,
For example, substituted Pcs containing hydrocarbon
a tetra(thiafulvalene-crown-ether) phthalocyanine was
chains and/or crown ether (CE) units self-assembled
found to self-assemble into helical tapes (nanometers in
into highly organized columnar aggregates are used for
width and micrometers in length) and showed potentially
one-dimensional charge and ion transport [6].
novel electronic and structural properties [23]. Although
Various tetrathiafulvalene (TTF)-modified Pcs and
TTF annulated macrocycles have received less atten-
porphyrins have been developed since the first report
tion, they are believed to be more attractive candidates
for various applications than ensembles of TTF and
Pcs or porphyrins linked by spacers because they can
self-assemble into various organized aggregates [24–29].
Normally, Pcs or porphyrins that are directly annulated
*Correspondence to: Bingzhu Yin, email: zqcong@ybu.edu.
cn, tel: +86 433-2732298, fax: +86 433-2732456 and Ren-gen
Xiong, email: xiongrg@seu.edu.cn
Copyright © 2010 World Scientific Publishing Company

NOVEL METALLOPORPHYRAZINES ANNULATED WITH TETRATHIAFULVALENE HAVING PENTOXYCARBONYL
109
NC
S
O
CO2CH3
CO2CH3
CO2R
CO2R
CO2R
CO2R
NC
NC
S
S
S
S
S
S
S
S
S
ROH
NC
S
S
K2CO3
P(OEt)3
toluene/reflux
2a R = butyl
2b R = pentyl
3a R = butyl
3b R = pentyl
1
RO2C
CO2R
S
S
S
S
N
N
N
M
N
RO2C
RO2C
CO2R
S
S
M(OAc)2
S
S
S
S
S
S
3b
N
N
PeOH/reflux
CO2R
N
N
R = pentyl
S
S
S
S
4
5
6
M = Zn
M = Cu
M = Ni
RO2C
CO2R
Scheme 1. Synthetic route for tetrathiafulvalene-annulated metalloporphyrazines (4–6)
with four TTF units do not show luminescence because
of the presence of fused electron-donating TTF units.
Their fluorescent forms can, however, be achieved
if the TTF units are oxidized using various chemi-
cal oxidants or an electrochemical method. Hence
they could be regarded as electro-switchable fluores-
cent molecules. Electro-switched luminescence has
been observed in a mono TTF-annulated porphyrin
and tetrakis-TTF-Pc molecules [25–26, 30]. The syn-
thesis of tetrakis-TTF-porphyrin resulted in a mixture
of the neutral porphyrin and its corresponding radi-
cal cation. We have recently also reported the synthe-
sis of novel porphyrazines (Pzs) annulated with four
TTF units that also contain electron-donating alkyl-
thio groups. These molecules spontaneously form TTF
group radical cations during the separation process
[31]. This hindered an accurate assessment of their
photophysical and electrochemical properties.
13C), and chemical shifts were referenced relative to tetra-
methylsilane (δH/δC = 0). The UV-vis spectra were recorded
on a Hitachi U-3010 spectrophotometer in CHCl3 (c =
2 × 10-5 M). Mass spectrometry was performed on a Hewl-
ett Packard 1100-HPLC/MSD instrument (APCI mode).
HRMS data were obtained by a JEOL JMS SX 102A appa-
ratus. MALDI-TOF-MS data were obtained by a Shimadzu
AXIMA-CFRTM plus mass spectrometry, using a 1,8,9-
anthracenetriol (DITH) matrix. Cyclic voltammetry was
carried out on a Potentiostat/Galvanostat 273A instrument
in CH3CN-CH2Cl2 with 0.1 M Bu4PF6 as supporting electro-
lyte and the scan rate was 100 mV.s-1. Counter and working
electrodes were made of Pt and Glass-Carbon, respectively,
and the reference electrode was calomel electrode (SCE).
IR spectra were recorded on a Shimadu FT-IR 1730 instru-
ment (KBr pressed disc method). Mass spectrometry was
performed on a Hewlett Packard 1100-HPLC/MSD instru-
ment. The ESR spectra were recorded using a FA200GEOL
spectrometer at 25 °C. Crystal data were measured on a
Rigaku SCXmini diffractometer with Mo Kα radiation
(λ = 0.71073 Å) by ω scan mode at 293(2) K.
To investigate the effect of peripheral substituents
on the stability of TTF annulated Pzs we introduced
electron-withdrawing pentoxycarbonyl groups onto TTF
annulated Pzs. Three novel TTF-annulated Pz dyes, as
shown in Scheme 1, were thus synthesized and we evalu-
ated their photophysical and electrochemical properties.
Synthesis
All reagents and solvents were of commercial qual-
ity and distilled or dried when necessary using standard
procedures. All reactions were carried out under argon
atmosphere. Starting materials 1 [32], 4,5-dicyano-1,3-
dithiol-2-one [33] and 2a [34] were prepared according
to methods described in referenced literature.
EXPERIMENTAL
General
Dipentyl 2-thioxo-1,3-dithiole-4,5-dicarboxylate (2b).
A mixture of 1 (1000 mg, 4 mmol) and K2CO3 (100 mg,
NMR spectra were recorded in CDCl3 with a Bruker
AV-300 Spetrometer (300 MHz for H and 75 MHz for
1
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 109–114

110
F. LENG ET AL.
0.15 mmol) in 10 mL pentanol was stirred for 72 h at room
temperature. Methanol produced was removed uninter-
ruptedly under reduced pressure. The reaction mixture was
concentrated in vacuum to yield yellow oil, which was puri-
fied by column chromatography (silica gel, CH2Cl2/P.E. =
1:1, Rf = 0.74) to give pure 2b as yellow oil. Yield 1160
mg (80.3%).1H NMR (300 MHz; CDCl3; Me4Si): δH, ppm
0.94 (3H, s, -CH2-CH3), 1.37 (4H, s,-CH2-CH2-CH3), 1.73
(2H, t, J = 6.6 Hz, -CH2-CH2-), 4.30 (2H, t, J = 6.6 Hz,
-O-CH2-). 13C NMR (75 MHz; CDCl3; Me4Si): δC, ppm
13.92 (-CH2-CH3), 22.23 (-CH2--CH3), 27.87 (-CH2-CH2-
CH2-), 27.96 (-CH2-CH2-), 67.44 (O-CH2-), 138.36 (C=C),
157.56 (C=O), 207.44 (C=S). MS (APCI): m/z 362.0448
(calcd. for [M + H]+ 363.53).
(Zn(OAc)2·2H2O for 4, Cu(OAc)2·2H2O for 5, anhydrous
NiCl2 for 6) was heated in 10 mL n-pentanol at 145 °C
for 4 h. The color of reaction solution changed from dark
red to black. The solvent was concentrated in vacuum
to give 4 as black powder. The solid obtained was puri-
fied on silica gel column chromatography (gradient of
CH2Cl2/MeOH = 1/0 → 50:1, v/v) to give 4. Compound
4: reprecipitation from CH2Cl2-MeOH gave 4 as dark
blue powder. Yield 56 mg (56%), mp 260 °C (decom-
posed). Anal. calcd. for C80H88N8O16S16Zn: C, 48.14;
1
H, 4.44; N, 5.61. Found: C, 48.32; H, 4.23; N, 5.80. H
NMR (300 MHz; CDCl3; Me4Si): δH, ppm 0.95 (24H, br,
-CH2-CH3), 1.39 (32H, br, -CH2-CH2-CH3), 1.68 (16H,
br, -CH2-CH2-), 4.22 (16H, br, -CH2-COO-). 13C NMR
(75 MHz; CDCl3; Me4Si): δC, ppm 13.97 (-CH2-CH3),
22.39 (-CH2-CH3), 27.97 (-CH2-CH2-), 66.66 (COO-
CH2-CH2-), 130–134 (br), 157-160 (br). IR (KBr pellets):
Dialkyl
2,3-dicyanotetrathiafulvalenes-6,7-di-
carboxylate (3a-3b). According to literature procedure
[34], an equimolar mixture of 4,5-dicyano-1,3-dithiol-2-
one (2 mmol) and 2 (2 mmol) in 60 mL toluene was added
dropwise to a refluxing mixture of 10 mL P(OEt)3 and 20 mL
toluene. The mixture was refluxed for 1 h. After cooling
to room temperature, the solvent was removed in vacuum
and the red oily residue obtained was chromatographed on
a silica gel column (CH2Cl2/P.E. = 1/1, v/v) to afford dark
red solid 3. Compound 3a: recrystallization from petro-
leum ether gave 3a as dark red needles. Yield 122 mg
(13.6%), mp 66–67 °C. Anal. calcd. for C18H18N2O4S4: C,
47.56; H, 3.99; N, 6.16. Found: C, 47.55; H, 3.71; N, 6.00.
1H NMR (300 MHz; CDCl3; Me4Si): δH, ppm 0.96 (3H,
t, J = 7.2 Hz, -CH2-CH3), 1.34–1.47 (2H, m, -CH2-CH3),
1.64–1.73 (2H, m, -CH2-CH2-), 4.26 (2H, t, J = 6.6 Hz,
-O-CH2-CH2-). 13C NMR (75 MHz; CDCl3; Me4Si): δC,
ppm 13.62 (-CH2-CH3), 18.99 (-CH2-CH3), 30.27 (-CH2-
CH2-), 67.07 (COO-CH2-CH2-), 101.94 (C-CN), 108.85
(NC-C=C-CN), 118.71 (-S-C=C-S-), 121.10 (S-C=C-S),
131.76 (OOC-C=C-COO-), 158.64 (-C-COO-). IR (KBr
pellets): νmax, cm-1 2959 (C-H), 2870 (C-H), 2216 (CαN),
1734 (C=O), 1705 (C=O), 1579, 1294, 1252, 1026. MS
(APCI): m/z 477.0 (calcd. for [M + Na]+ 477.61). Com-
pound 3b: recrystallization from petroleum ether gave 3b
as a dark red needles.Yield 214 mg (22.2%), mp 64.7 °C.
Anal. calcd. for C20H22N2O4S4: C, 49.77; H, 4.59; N, 5.80.
Found: C, 49.55; H, 4.73; N, 5.57. 1H NMR (300 MHz;
CDCl3; Me4Si): δH, ppm 0.92 (3H, t, J = 3.0 Hz ,-CH2-
CH3), 1.35 (4H, br, -CH2-CH2-CH3), 1.70 (2H, br, -CH2-
CH2-), 4.25 (2H, t, J = 6.6 Hz, -CH2-COO-). 13C NMR (75
MHz; CDCl3; Me4Si): δC, ppm 13.95 (-CH2-CH3), 22.23
(-CH2-CH3), 27.84 (-CH2-CH2-), 28.81 (-CH2-CH2-),
67.36 (COO-CH2-CH2-), 101.97 (C-CN), 108.88 (NC-
C=C-CN), 118.72 (-S-C=C-S-), 120.93 (-S-C=C-S-),
131.79 (OOC-C=C-COO-), 158.64 (-C-COO-). IR (KBr
pellets): νmax, cm-1 2954 (C-H), 2860 (C-H), 2210 (CαN),
1740 (C=O), 1701 (C=O), 1290, 1224. MS (APCI): m/z
483.0 (calcd. for [M + H]+ 483.66).
ν
max, cm-1 2955–2856 (C-H), 1730 (C=O), 1575, 1462,
1250, 1094. UV-vis (CHCl3): λmax, nm (log ε) 291 (4.53),
358 (4.52), 605 (4.35). MS (MALDI-TOF): m/z 1996.81
(calcd. for [M + H]+ 1997.05). Compound 5: reprecipita-
tion from CH2Cl2-MeOH gave 5 as dark purple powder.
Yield 52 mg (52.4%), mp 250 °C (decomposed). Anal.
calcd. for C80H88CuN8O16S16: C, 48.18; H, 4.45; N, 5.62.
Found: C, 48.27; H, 4.36; N, 5.54. 1H NMR (300 MHz;
CDCl3; Me4Si): δH, ppm 0.92 (24H, br, -CH2-CH3), 1.35
(32H, br, -CH2-CH2-CH3), 1.68 (16H, br, -CH2-CH2-),
4.32 (16H, br, -CH2-COO-). 13C NMR (75 MHz; CDCl3;
Me4Si): δC, ppm 13.92 (-CH2-CH3), 22.26 (-CH2-CH3),
27.88 (-CH2-CH2-), 28.07 (-CH2-CH2-), 66.73 (COO-
CH2-CH2-), 130-133 (br), 157-160 (br). IR (KBr pellets):
ν
max, cm-1 2955-2862 (C-H), 1726 (C=O), 1576, 1460,
1246, 1088. UV-vis (CHCl3): λmax, nm (log ε) 290 (4.78),
317 (4.76), 567 (4.33), 601 (4.31). MS (MALDI-TOF):
m/z 1994.44 (calcd. for [M + H]+ 1995.18). Compound 6:
reprecipitation from CH2Cl2-MeOH gave 6 as dark pur-
ple powder. Yield 24.5 mg (24.6%), mp 250 °C (decom-
posed). Anal. calcd. for C80H88N8NiO16S16: C, 48.30;
1
H, 4.46; N, 5.63. Found: C, 48.19; H, 4.45; N, 5.44. H
NMR (300 MHz; CDCl3; Me4Si): δH, ppm 1.05 (24H, br,
-CH2-CH3), 1.48 (32H, br, -CH2-CH2-CH3), 1.80 (16H,
br, -CH2-CH2-), 4.25 (16H, br, -CH2-COO-). 13C NMR
(75 MHz; CDCl3; Me4Si): δC, ppm 14.13 (-CH2-CH3),
22.47 (-CH2-CH3), 28.08 (-CH2-CH2-), 29.69 (-CH2-
CH2-), 66.56 (COO-CH2-CH2-). IR (KBr pellets): νmax
,
cm-1 2955–2862 (C-H), 1730 (C=O), 1578, 1642, 1230,
1113. UV-vis (CHCl3): λmax, nm (log ε) 291 (4.78), 325
(4.79), 557 (4.55), 593 (4.40). MS (MALDI-TOF): m/z
1988.49 (calcd. for [M + H]+ 1989.48).
RESULTS AND DISCUSSION
{2,3,7,8,12,13,17,18-tetrakis[6,7-bis(alkyl-
oxycarbonyl)tetrathiafulvalene]porphyrazines} M(II)
(M = Zn for 4, Cu for 5 and Ni for 6). A mixture of 97 mg
3b (0.2 mmol) and the appropriate metal salt (0.1 mmol)
Synthesis and characterization
The synthesis of target compounds 4–6 is shown in
Scheme 1. The first step in the synthetic procedure is the
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NOVEL METALLOPORPHYRAZINES ANNULATED WITH TETRATHIAFULVALENE HAVING PENTOXYCARBONYL
111
Fig. 1. ORTEP plot of the molecule of 3a
synthesis of dicyanotetrathiafulvalene 3 that contains
Fig. 2. Absorption spectra of 4–6 in CHCl3 (2 × 10–5 M)
electron-withdrawing ester groups. The cross-coupling
reaction of 4,5-dicyano-1,3-dithiol-2-one and dialkyl
1,3-dithiol-2-thione-4,5-dicarboxylate (2a–b) in a mix-
Photophysical properties
ture of triethyl phosphite and toluene at reflux and under
argon leads to key intermediates 2,3-dicyano-6,7-bis-
(pentyloxycarbonyl) TTF (3a–b) in 14% and 22% yields,
respectively.
UV-vis spectra of TTF annulated Pzs 4–6 in CH2Cl2
are shown in Fig. 2. Compounds 4–6 show typical Pz
electronic spectra, consisting of two strong absorption
regions. Broadening of the Q and B bands is attributed
to n-π* transitions of non-bonding electrons, that are
associated with peripheral S and N atoms [36], and also
attributed to aggregation of the macrocyclic system. The
B band (or Soret band) of metallo-Pz rings in the ultra-
violet region for compound 4 arises from deep π LUMO
transitions (between a2u and eg orbitals). TTF absorption
in this region thus leads to superimposed bands. In the
visible region, 4 had an intense Q band at 605 nm with a
shoulder at around 574 nm and this corresponds to mono-
meric and aggregated Pz in chloroform, respectively. The
indistinct shoulder band at about 574 nm, arising from the
dimer, is attributed to a π→π* transition from the HOMO
to the LUMO of the Pz2- ring. For 5 the Q band of the
dimer at higher energy was centered at 566 nm and the
Q band arising from the monomer was at a lower energy
and centered at 601 nm as a weak shoulder band. The
absorption bands of 6 are similar to those of 5 except that
the sharper component of the Q band at higher energy
is less intense in 5 and the monomer shoulder band is
stronger in 5. This indicates that there is a higher degree
of face-to-face interaction in 6 compared with the inter-
actions in 4 and 5 and this is typical of metallated sym-
metrically substituted Pzs with D4h symmetry [37].
Red crystals that were suitable for X-ray diffraction
analysis of intermediate 3a was obtained by the slow
evaporation of a petroleum ether (30–60 °C) solution of
3a at room temperature. Compound 3a crystallizes in a
monoclinic space group (P21/c) and the 1, 3-dithiole-4,5-
dicarbonitrile unit is almost coplanar with the ester sub-
stituent dithiole ring [dihedral angle = 2.9(2)°] (Fig. 1).
In the crystal structure, intermolecular S…O interactions
[S3...O2 = 3.013 Å] create dimers between neighboring
molecules in the ac plane. In addition, a weak π···π stack-
ing interaction exists between adjacent dithiole rings,
with centroid-centroid distances of 4.075 Å, and chains
formed along the b axis (Figs S1–S2, see Supporting
information section).
Using the building block 3b, we synthesized TTF
annulated metallo-Pzs (4–6) by a metal templated
tetramerization in 1-pentanol and obtained yields of 56%
for Zn-TTF-Pz 4, 52% for Cu-TTF-Pz 5 and 15% for Ni-
TTF-Pz 6, respectively. As expected, the TTF annulated
Pz dyes were sufficiently stable for purification and for
further experiments. The compounds are soluble in com-
mon organic solvents such as hexane, benzene, toluene,
CHCl3, CH2Cl2, DMF, acetone and THF. The compounds
are insoluble in alcohols and DMSO. We were unable
to demetallate the metallo-Pzs 4–6 using acidic reaction
conditions because the ester groups decomposed [35].
1H NMR spectra of 4–6 in CDCl3 displayed four very
broad signals which could be explained by considering
that slow tumbling results from aggregation in concen-
trated solutions (Fig. S2) [24, 33]. The MALDI-TOF
mass spectra of 4–6 showed peaks at m/z = 1996.81 (M+ =
1996.05) for 4, 1994.44 (M+ = 1994.18) for 5 (Fig. S3)
and 1988.49 (M+ = 1988.48) for 6. Results from ele-
mental analysis confirmed the proposed structures of
compounds 4–6.
In order to address the donor properties of target com-
pounds, 4 was selected and dope with TCNQ in CH2Cl2.
However no CT band was observed at 600–1000 nm
region. This might be attributed to the presence of eight
strongly electron-withdrawing pentoxycarbonyl groups
onto TTF annulated Pzs. Whereas, doping of F4TCNQ to
a CH2Cl2 solution of 4 (2 × 10-5 M) resulted in the appear-
ance of two new CT absorption bands, centered on λmax
=
756 nm and λmax = 863 nm in the UV-vis spectrum (Fig.
3). These new bands corresponds to the SOMO-LUMO
transition of the cation radical species of the TTF moieties
[23]. The formation of F4TCNQ-•/TTF+• charge-transfer
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F. LENG ET AL.
g = 2.007 and 2.002, which are in the region characteris-
tic of both a TTF radical cation [39] and a F4TCNQ radi-
cal anion [38]. These results show that in solution some
CT takes place between the TTF unit(s) and F4TCNQ
(Fig. S4).
Cyclic voltammetric (CV) studies were performed
on compounds 4–6 and their intermediates 3a–b in a
mixture of CH3CN-CH2Cl2. The data are collected in
Table 1. As seen in Table 1, the cyclic voltammograms of
3a–b reveal that all redox processes are quasi-reversible.
Each oxidation wave of the precursor compounds 3a
and 3b is assigned to a one-electron process. By com-
parison to tetrathiafulvalene [40], both oxidation peaks
were shifted significantly to higher oxidation potentials
(1.034 and 1.275 V for 3a and 1.035 and 1.278 V for
3b, respectively) because of the electron-withdrawing
effect of the cyano and alkoxycarbonyl groups. For the
electrochemical characterization of compounds 4–6,
the cyclic voltammograms were indistinct because of
aggregation in solution. This behavior has previously
been reported in the literature [26, 41]. Differential pulse
voltammetry (DPV) provided more detailed informa-
tion. Figure 4 shows cyclic (a) and differential pulse vol-
tammograms (b) of 4 within a -2000 mV to +2200 mV
potential window. Compound 4 shows redox processes
Fig. 3. Absorption spectra of 4 (2 × 10-5 M) in the CH2Cl2 after
addition of different equiv. F4TCNQ
complex in the mixture F4TCNQ-4 (4:1) in CH2Cl2 was
also confirmed by the FT-IR and ESR spectra. A FT-IR
spectrum showed the nitrile stretch of the F4TCNQ radi-
cal anion at 2212 cm-1 [38] compared to the neutral state
of 2222 cm-1. In addition, an electron paramagnetic
resonance (ESR) spectrum of 4 was centered around
Table 1. Cyclic voltammetric data for M-TTF-Pzs 4–6 and intermediates 3a–b in a mixture of CH2Cl2 and
CH3CN (4:1, v/v)
Compound
E11/2(∆E)/V
E21/2(∆E)/V
E31/2(∆E)/V
E4pa/V
TTF[40]
0.36
0.77
3a
3b
4
1.034 (0.073)
1.035 (0.077)
0.914 (0.088)
0.972 (0.106)
0.998 (0.102)
1.275 (0.089)
1.278 (0.087)
1.308 (0.150)
1.304 (0.137)
1.313 (0.106)
-0.813 (0.273)
-0.802 (0.283)
-0.836 (0.283)
1.786
1.784
1.784
5
6
Fig. 4. Cyclic (a) and differential pulse voltammogram (b) of compound 4 in CH3CN-CH2Cl2 (1:4, v/v) containing 0.1 M Bu4PF6.
Scan rate was 100 mV.s-1
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113
at E1/2 = -0.813 (I), 0.914 V (II), 1.308 V (III) and 1.786 V
(IV) vs the SCE and all processes are not completely
reversible in terms of ∆E, the shift of Ep at different
scanning rates and the ratio of anodic to cathodic peak
currents (ipa/ipc) [42]. Process I which is assigned to a
reduction of the porphyrazine ring system (Pz-2/Pz-3) is
irreversible because of the excessive anodic to cathodic
peak separation (∆E > 200 mV) and the difference of
anodic to cathodic peak currents. Processes II and III are
quasi-reversible because the anodic to cathodic peak cur-
rents are near unity while ∆E for II and III are 88 mV
and 150 mV, respectively. These processes represent the
two four-electron oxidation processes of the TTF moi-
eties. Interestingly, 4 shows similar behavior to its phtha-
locyanine analog [25] with negative shifts in oxidation
potentials for the radical cations of TTF (0.12 V). The
splitting of the first oxidation wave (process II) arises
from the molecular system where the donor moieties
interact through conjugation and/or through space. On
the other hand, compound 4 is distinct from its phthalo-
cyanine analogs and an irreversible one-electron wave is
observed at 1.786 V (IV), which is assigned to oxidation
of the Pz ring system (Pz-1/Pz-2). The redox processes of
compounds 5 and 6 are similar to 4 except that their first
oxidation waves are not split.
In summary, we developed an efficient synthetic
route to the novel porphyrazines that are annulated with
tetrathiafulvalene having pentoxycarbonyl substitu-
ents. Efficient modulation of macrocycle stability was
achieved by the introduction of electron-withdrawing
pentoxycarbonyls. Ability of 4 to function as a donor
for F4TCNQ was established and the formation of TTF+/
F4TCNQ- charge-transfer complex was confirmed by the
UV-vis, FT-IR and ESR spectral. Compounds 5 and 6
showed similar cyclic voltammetric behavior with one
reduction process and three oxidation processes. These
were assigned to Pz-2/Pz-3 (I), TTF+•/TTF (II), TTF+2/
TTF+• (III) and Pz-1/Pz-2 (IV). The synthesis, self-as-
sembly and film forming properties of TTF-annulated
Pzs with longer alkyls and containing oxyethylenes are
under investigation.
material. This material is available free of charge via the
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Acknowledgements
This work was supported by National Science Foun-
dation of China (Grant No. 20662010), the Specialized
Research Fund for the Doctoral Program of Higher Edu-
cation (Grant no. 20060184001) and the open project of
State Key Laboratory of Supramolecular Structure and
Materials, Jilin University. Ren-Gen Xiong only contrib-
utes the X-ray determination.
Supporting information
Crystal data and structure of 3a, 1HNMR and MALDI-
TOF-MS spectra of 5, and ESR spectrum of 4
(Figs S1–S4, Table S1) are given in the supplementary
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