Preparation of octakis (methylthio)octaethylphthalocyaninato titanium (IV) benzenedichalcogenolates

Article abstract of DOI:10.1080/10426501003772144

Octakis(methylthio)octaethylphthalocyaninato titanium (IV) oxide (PcSMeTiO) was prepared from octakis(methylthio)octaethylphthalocyanine (PcSMe) upon treatment with titanium (IV) tetrabutoxide in DMF at 130°C. The reaction of PcSMeTiO with benzenedithiol

Full text of DOI:10.1080/10426501003772144

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Preparation of Octakis
(methylthio)octaethylphthalocyaninato
Titanium (IV) Benzenedichalcogenolates
Takeshi Kimura a , Arata Yamamoto a & Toshiharu Namauo a
a Center for Instrumental Analysis , Iwate University , Iwate, Japan
Published online: 27 May 2010.
To cite this article: Takeshi Kimura , Arata Yamamoto & Toshiharu Namauo (2010) Preparation of
Octakis (methylthio)octaethylphthalocyaninato Titanium (IV) Benzenedichalcogenolates, Phosphorus,
Sulfur, and Silicon and the Related Elements, 185:5-6, 1008-1013, DOI: 10.1080/10426501003772144
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Phosphorus, Sulfur, and Silicon, 185:1008–1013, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003772144
PREPARATION OF OCTAKIS
(METHYLTHIO)OCTAETHYLPHTHALOCYANINATO
TITANIUM (IV) BENZENEDICHALCOGENOLATES
Takeshi Kimura, Arata Yamamoto, and Toshiharu Namauo
Center for Instrumental Analysis, Iwate University, Iwate, Japan
Octakis(methylthio)octaethylphthalocyaninato titanium (IV) oxide (PcSMeTiO) was pre-
pared from octakis(methylthio)octaethylphthalocyanine (PcSMe) upon treatment with tita-
nium (IV) tetrabutoxide in DMF at 130◦C. The reaction of PcSMeTiO with benzenedithiol
or benzenediselenol produced octakis(methylthio)octaethylphthalocyaninato titanium (IV)
benzenedichalcogenolates (4a,b) bearing titanium–sulfur or titanium–selenium bonds.
Keywords Phthalocyanine; S ligand; Se ligand; titanium
INTRODUCTION
Tetraazaporphyrins and related compounds have a variety of actual and po-
tential applications in many fields such as dyes, pigments, catalysts, new functional
materials, and sensitizers for photodynamic therapy.1,2 Among the great number of
tetraazaporphyrins, phthalocyanines connecting one or two axial coordinating groups
on the central metal atom have attracted much attention because the molecules could
be applied to electrochromic displays, field-effect transistors, nonlinear optical ma-
terials, and dye-sensitized solar cells.3 Recently, Hanack and colleagues reported
phthalocyaninato titanium (IV) complexes as compounds that have axial coordinating
groups connected with titanium–oxygen or titanium–sulfur bonds,4 while Kobayashi
and colleagues synthesized a mutually perpendicular phthalocyanine pentamer and
related derivatives.5 These products were prepared by the ligand exchange reaction of
tetra-t-butylphthalocyaninato titanium (IV) oxide with o-catechols, o-benzenedithiol,
tetrahydroxy-p-benzoquinone, and octahydroxyphthalocyanine. In contrast, we reported
the double-decker phthalocyanine, which was obtained by the reaction of two molecules
of octakis(methylthio)octaethylphthalocyaninato titanium (IV) oxide (PcSMeTiO) with
benzene-1,2,4,5-tetrathiol.6 To construct a new type of phthalocyanines with an axial
ligand, PcSMeTiO was reacted with 3,6-diethyl-4,5-dibromobenzene-1,2-dithiol (3a) or
3,6-diethyl-4,5-dibromobenzene-1,2-diselenol (3b). This article reports the preparation
Received 26 November 2008; accepted 17 December 2008.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
Address correspondence to Takeshi Kimura, Center for Instrumental Analysis, Iwate University, Morioka,
Iwate 020-8551, Japan. E-mail: kimura@iwate-u.ac.jp
1008

PHTHALOCYANINATO TI (IV) BENZENEDICHALCOGENOLATES
1009
and electrochemical property of octakis(methylthio)octaethylphthalocyaninato titanium
(IV) diethyldibromobenzenedichalcogenolates (4a,b).
RESULTS AND DISCUSSION
5,6-Dibromo-4,7-diethylbenzotrichalcogenoles (1a,b) were converted into 1,2-
bis(2-cyanoethylchalcogeno)-4,5-dibromo-3,6-diethylbenzenes (2a,b) in 96% and 70%
yields, respectively, upon treatment with NaBH4 and then 2-cyanoethyl bromide
(Scheme 1).7
Et
Et
Et
Br
Br
Br
Br
Br
Br
X
X
XH
XH
X
X
(i) (ii)
(iii), (iv)
CN
CN
X
a:
b:
X = S,
X = Se,
96%
70%
Et
Et
Et
3a,b
1a,b
2a,b
Scheme 1 (i) NaBH4, K2CO3, THF/MeOH; (ii) BrCH2CH2CN; (iii) CsOH, THF/MeOH; (iv) HCl
The treatment of octakis(methylthio)octaethylphthalocyanine (PcSMe) with titanium
(IV) tetrabutoxide by the procedure reported previously produced PcSMeTiO.6 To prepare
benzenedithiol (3a) as a bidentate sulfur ligand, 2a was reacted with CsOH in THF/MeOH
under Ar (Scheme 1).8,9 The reaction mixture was acidified with concentrated HCl to
generate 3a. The prepared solution was transferred to the reactor containing PcSMeTiO,
and the reaction mixture was stirred for 24 h (Scheme 2). After workup and purification with
silica gel column chromatography and Bio-beads column chromatography, phthalocyanine
(4a) with benzenedithiolate as the axial ligand was obtained in 51% yield.
Br
Br
SMe
SMe
MeS
MeS
Et
Et
Et
Et
Et
N
O
Ti
SMe
SMe
MeS
MeS
Et
X
X
Et
(v)
N
N
N
N
Et
Et
N
N
N
Ti
N
a: X = S, 51%
b: X = Se,
Et
Et
MeS
MeS
Et
N
N
N
N
33%
N
N
N
SMe
SMe
Et
MeS
MeS
Et
Et
Et
SMe
SMe
Et
Et
PcSMeTiO
4a,b
Scheme 2 (v) 3a or 3b, THF/MeOH.
In the 1H NMR spectrum, 4a showed the signals of the ethyl and methylthio groups
connected to the phthalocyanine core at δ = 1.60 (t), 2.72 (s), and 4.68–5.00 (m) ppm.
These chemical shifts are slightly upper field compared with those of PcSMeTiO: δ = 1.74
(t), 2.78 (s), 4.94 and 5.02 (dq) ppm. The signals for the ethyl group of benzenedithiolate
were observed at δ = 0.23 (t) and 1.81 (q) ppm, which are higher magnetic field than those
of 2a: δ = 1.29 (t) and 3.28 (q) ppm. These results could show that the benzene ring lies
on the phthalocyanine plane and is strongly affected in the magnetic shielding range of the
macrocycle. When 13C NMR of 4a was measured, the four signals for the phthalocyanine

1010
T. KIMURA ET AL.
skeleton, the five signals for the ethyl and the methylthio groups, and three signals for the
coordinating benzene ring appeared in the following spectrum: δ = 11.5, 16.4, 22.7, 25.4,
30.0, 124.9, 132.9, 136.4, 146.7, 146.8, 147.9, 151.4 ppm. Since the signals for PcSMeTiO
were observed at δ = 16.8, 22.3, 25.2, 134.0, 146.8, 147.1, 151.8 ppm, the signals for 4a
at 11.5, 30.0, 124.9, 136.4, 147.9 ppm might be the carbon of benzenedithiolate. It appears
that the phthalocyanine skeleton of 4a is a C4 symmetric structure in the NMR time scale at
25◦C, though benzenedithiolate coordinates to the central titanium atom. Furthermore, the
FABMS spectrum of 4a showed the corresponding molecular ion peak at m/z = 1504.13
[M+].
The similar treatment of PcSMeTiO with 3b produced phthalocyanine (4b) with
benzenediselenolate in 33% yield. The 1H NMR and 13C NMR spectra of 4b were similar
to those of 4a. The 77Se NMR spectrum showed the signal at δ = 448.5 ppm, which is
a much higher magnetic field than that of the bis(cyclopentadienyl)benzodiselenatitanole
derivatives.10 The FABMS spectrum of 4b exhibited the molecular ion peak at m/z =
1600.13 [M+].
In the UV-vis spectra measured in CHCl3, the Q band absorptions of 4a and 4b were
observed at λmax = 763.5 and 765.5 nm, respectively, which were wider bandwidth and
slightly longer wavelengths than that of PcSMeTiO (λmax = 760 nm). The bandwidth of the
Q band absorption of the free-base phthalocyanine, PcSMe, is more enlarged than that of
PcSMeTiO because of the proton alternation between the central pyrrolic nitrogen atoms.
Although the phthalocyanine skeleton of 4a and 4b is the C4 symmetry, the coordination
of benzenedichalcogenolate to the central titanium atom in the axial direction could have
made the symmetry of the π-electronic system decrease from C4 to C2, which resulted in
the broadening of the Q band absorption of 4a and 4b compared with that of PcSMeTiO.
The electrochemical properties of 4a and 4b were examined by cyclic voltammetry
using Ag/AgNO3 as a reference electrode (measured in CH2Cl2, scan rate: 100 mV/s).
The cyclic voltammogram of 4a contained one irreversible oxidation (Ep = 0.87 V) and
three quasi-reversible reduction potentials (E1/2 = –1.73, –1.06, and –0.76 V). Compound
(4b) showed the irreversible oxidation potential at Ep = 0.85 V while the quasi-reversible
reduction potentials were observed at E1/2 = –1.78, –1.04, and –0.75 V. As shown in Table I,
it appeared that the oxidation and reduction potentials of 4a and 4b are higher than those
of PcSMe and PcSMeTiO.
Table I Redox potentials (vs. Ag/AgNO3)
E1/2 [V]
Compounds
3rd reduction
2nd reduction
1st reduction
1st oxidation
2nd oxidation
ꢀE (V)
PcSMea
PcSMeTiOa
4ab
—
—
–1.41
–1.14
–1.06d
–1.04d
–1.08
–0.80
–0.76d
–0.75d
0.52
0.68
0.87c
0.85c
0.91
1.13c
—
1.60
1.48
1.63
1.60
−1.73d
4bb
−1.78d
—
aScan rate: 200 mV/s.
bScan rate: 100 mV/s.
cIrreversible (Ep /V).
dQuasi reversible.
ꢀE is the difference between the first oxidation potential and the first reduction potential.

PHTHALOCYANINATO TI (IV) BENZENEDICHALCOGENOLATES
1011
EXPERIMENTAL
NMR spectra were measured with a Bruker AC-400 spectrometer at 25◦C. Mass
spectra were obtained using a JEOL JMS-700 mass spectrometer. UV-vis spectra were
recorded with a JASCO Ubest V-570 spectrometer. A Hokuto Denko Co. Model HAB-
151 apparatus was employed for measuring oxidation potentials. Elemental analysis was
performed using a Yanako MT-5 analyzer. Bio-beads (SX-1) for column chromatography
were purchased from Nippon Bio-Rad Laboratories.
Oxidation Potentials
All measurements were performed by cyclic voltammetry, using Ag/AgNO3 (0.01
mol/l) as a reference electrode (scan rate: 100 mV/s or 200 mV/s). A solution of n-Bu4NClO4
in CH2Cl2 (0.1 mol/l) was used as an electrolyte. The oxidation potential of ferrocene was
observed at E1/2 = 0.09 V by the apparatus without any correction.
Materials
Compounds (1a), (1b), (2a), PcSMe, and PcSMeTiO were prepared using a method
described previously.6,7
1,2-Bis(2-cyanoethylseleno)-4,5-dibromodiethylbenzene (2b)
To a solution of 1b (1.604 g, 3 mmol) and K2CO3 (831 mg, 6 mmol) in THF (20
ml)/MeOH (10 ml), NaBH4 (347 mg, 9.1 mmol) was added under Ar, and the solution was
stirred for 30 min. 3-Bromopropionitrile (0.97 ml, 12 mmol) was added to the solution.
After stirring for 6 h and acidification with HCl, the solvent was evaporated, and the product
was extracted with CHCl3. The solvent was evaporated, and the residue was purified by
column chromatography (Wakogel C-400, n-hexane:CHCl3 = 1:1) to produce 2b in 70%
yield (1.182 g); colorless crystals; mp 83–86◦C; 1H NMR (400 MHz, CDCl3) δ = 1.18 (t, J
= 7.4 Hz, 6H), 2.71 (t, J = 7.2 Hz, 4H), 3.20 (t, J = 7.2 Hz, 4H), 3.43 (q, J = 7.4 Hz, 4H)
ppm; 13C NMR (101 MHz, CDCl3) δ = 14.3, 18.7, 26.2, 36.2, 118.3, 130.3, 137.7, 149.5
ppm; 77Se NMR (76 MHz, CDCl3) δ = 325.2 ppm; HRMS Calcd for C16H1879Br2N280Se2,
555.8167. Found (m/z) 555.8167 (M+).
Generation of 3,6-Diethyl-4,5-dibromobenzene-1,2-dithiol (3a)
Compound (2a) (156.5 mg, 0.342 mmol) and CsOH (517.6 mg, 3.45 mmol) were
placed in a glass reactor under Ar. THF (5 mL) and MeOH (5 mL) were added to the
reactor, and the solution was stirred for 2 h. Concentrated HCl (0.29 mL) was added to the
solution to generate the corresponding dithiol (3a).
Generation of 3,6-Diethyl-4,5-dibromobenzene-1,2-diselenol (3b)
Compound (2b) (98.4 mg, 0.177 mmol) and CsOH (263.8 mg, 1.76 mmol) were
placed in a glass reactor under Ar. THF (5 mL) and MeOH (5 mL) were added to the
reactor, and the solution was stirred for 2 h. Concentrated HCl (0.14 mL) in methanol (6.9
mL) was added to the solution to generate the corresponding diselenol (3b).

1012
T. KIMURA ET AL.
Octakis(methylthio)octaethylphthalocyaninato Titanium (IV)
Benzenedithiolate (4a)
The solution of 3a, prepared as described above, was transferred by syringe to
the reactor containing PcSMeTiO (97.4 mg, 0.0845 mmol) under Ar. The solution was
stirred for 24 h, and the solvent was evaporated. The residue was purified by column
chromatography (Wakogel C-300HG, n-hexane:CHCl3 = 1:1 and CHCl3) and (Bio-beads,
CHCl3) to produce 4a in 51% yield (65.2 mg); dark green powder, mp > 300◦C; 1H NMR
(400 MHz, CDCl3) δ = 0.23 (t, J = 7.2 Hz, 6H, CH3), 1.60 (t, J = 7.2 Hz, 24H, CH3), 1.81
(q, 4H, CH2), 2.72 (s, 24H, SCH3), 4.68–5.00 (m, 16H, CH2) ppm; 13C NMR (101 MHz,
CDCl3) δ = 11.5, 16.4, 22.7, 25.4, 30.0, 124.9, 132.9, 136.4, 146.7, 146.8, 147.9, 151.4
ppm; UV-vis (CHCl3) λmax = 763.5 nm; FAB MS (m/z) 1504.13 [M+]; Anal. Calcd for
C66H74Br2N8S10Ti: C, 52.58; H, 4.95; N, 7.43. Found: C, 52.36; H, 5.09; N, 6.53.
Octakis(methylthio)octaethylphthalocyaninato Titanium (IV)
Benzenediselenoolate (4b)
Compound (4b) was prepared in 33% yield by the procedure as described above;
dark green powder, mp 225◦C; 1H NMR (400 MHz, CDCl3) δ = 0.29 (t, J = 7.4 Hz, 6H,
CH3), 1.59 (t, J = 7.2 Hz, 24H, CH3), 1.93 (q, 4H, CH2), 2.74 (s, 24H, SCH3), 4.60–4.99
(m, 16H, CH2) ppm; 13C NMR (101 MHz, CDCl3) δ = 11.7, 16.4, 22.7, 25.4, 29.7, 125.2,
132.9, 139.5, 146.6, 146.8, 148.5, 151.2 ppm; 77Se NMR (76 MHz, CDCl3) δ = 448.5 ppm;
UV-vis (CHCl3) λmax = 765.5 nm; FAB MS (m/z) 1600.13 [M+].
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