Solvent-free synthesis of soluble, near-IR absorbing titanyl phthalocyanine derivatives

Article abstract of DOI:10.1021/jo1011637

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. This methodology eliminates the formation of the unmetalated phthalocyanine (H₂

Full text of DOI:10.1021/jo1011637

pubs.acs.org/joc
the formation of TiOPc and derivatives.3-5 Yao et al.
Solvent-Free Synthesis of Soluble, Near-IR
Absorbing Titanyl Phthalocyanine Derivatives
elucidated that the key steps in the macrocyclization leading
to TiOPc were (1) generation of ammonia in situ by reaction
between 1-octanol, the solvent, and urea at elevated tem-
perature by carbamate formation5 and (2) adduct formation
between ammonia and Ti(OR)4 followed by TiOPc forma-
tion. Interestingly, when aprotic solvents were used, poor
yields of TiOPc resulted along with H2Pc contamination.5
However, subsequent use of these or similar conditions (e.g.,
urea and 1-pentanol) to prepare TiOPc derivatives led to
significant amounts of H2Pc contamination.3,4 Yet we have
found here that when the reaction to form TiOPc derivatives
was performed in a urea melt, the formation of H2Pc was
completely eliminated. It is well-known that urea undergoes
decomposition in the melt to produce ammonia and biuret
via isocyanic acid formation.6,7
Mayank Mayukh, Clarissa M. Sema, Jessica M. Roberts,
and Dominic V. McGrath*
Department of Chemistry, University of Arizona, Tucson,
Arizona 85721, United States
mcgrath@u.arizona.edu
Received June 19, 2010
Interest in TiOPc stems from its high electrical polarizability
and condensed-phase organization8,9 that result in photophysi-
cal and optical properties such as photoconductivity,10 third-
order nonlinear susceptibility,11 and near-IR absorptivity.9,12
TiOPc and its derivatives therefore find application as xero-
graphic photoreceptors,10 gas sensors,13 optical limiting
agents,10 photodynamic therapy (PDT) sensitizers, and donor
materials in organic solar cells.12,14 Interest in soluble derivatives
of TiOPc stems from the insolubility of TiOPc in common
organic solvents1 inhibiting purification by all but nonideal
methods such as entrainer sublimation10 and acid pasting15
and necessitating expensive vapor deposition for processing.12
Soluble derivatives can be processed into thin films by reel-to-
reel wet coating,16 inkjet printing,17 or spin-coating.3-5,18-20
Solvent-free synthesis of a series of alkylthio-substituted
titanyl phthalocyanine (TiOPc) derivatives starting from
the corresponding phthalonitriles (Pn) is reported. This
methodology eliminates the formation of the unmeta-
lated phthalocyanine (H2Pc), a side product that makes
purification difficult. The alkylthio groups on the re-
ported derivatives enhance solubility in common organic
solvents and shift the absorption to the near-IR region.
(6) Meessen, J. H.; Petersen, H. Urea. In Ullmann’s Encyclopedia of
Industrial Chemistry; Wiley-VCH: Weinheim, 2002.
(7) Recently, Zhang et al. reported using quinoline as a solvent to avoid
the formation of H2Pc side product. However, because of the high reaction
temperature (ca. 190 °C), the TiOPc product decomposed as it formed during
the reaction: Zhang, X. F.; Wang, Y.; Niu, L. H. J. Photochem. Photobiol. A
Chem. 2010, 209, 232.
(8) Hiller, W.; Strahle, J.; Kobel, W.; Hanack, M. Z. Kristallogr. 1982,
159, 173–183.
(9) Mizuguchi, J.; Rihs, G.; Karfunkel, H. R. J. Phys. Chem. 1995, 99,
16217–16227.
(10) Law, K. Y. Chem. Rev. 1993, 93, 449–486.
(11) Nalwa, H. S.; Saito, T.; Kakuta, A.; Iwayanagi, T. J. Phys. Chem.
1993, 97, 10515–10517.
(12) Placencia, D.; Wang, W. N.; Shallcross, R. C.; Nebesny, K. W.;
Brumbach, M.; Armstrong, N. R. Adv. Func. Mater. 2009, 19, 1913.
(13) (a) Liu, C. J.; Peng, C. H.; Ju, Y. H.; Hsieh, J. C. Sens. Actuators, B
1998, 52, 264–269. (b) Liu, C. J.; Wang, S. Y.; Hsieh, J. C.; Ju, Y. H. Sens.
Actuators, B 2000, 371–374.
(14) (a) Yanagi, H.; Chen, S. Y.; Lee, P. A.; Nebesny, K. W.; Armstrong,
N. R.; Fujishima, A. J. Phys. Chem. 1996, 100, 5447–5451. (b) Kim, Y. K.;
Kang, H. J.; Jang, Y. W.; Lee, S. B.; Lee, S. M.; Jung, K. S.; Lee, J. K.; Kim,
M. R. Int. J. Mol. Sci. 2008, 9, 2745–2756.
We report herein solvent-free conditions for the synthesis
of soluble, near-IR absorbing titanyl phthalocyanine
(TiOPc)1 derivatives. Solvent-free conditions are environ-
mentally friendly and industrially economical2 and in this
context effectively eliminate the formation of nonmetalated
phthalocyanine (H2Pc), a side product that interferes with
purification of TiOPcs. The usual route to the synthesis of
TiOPcs, which involves heating a solution of a phthalonitrile
(Pn) derivative and urea in a polar protic organic solvent
such as 1-pentanol, commonly leads to a mixture of H2Pc
and TiOPc. Urea is necessary as a source of ammonia during
(15) Weiss, D. S.; Abkowitz, M. Chem. Rev. 2010, 110, 479–526.
(16) Blankenburg, L.; Schultheis, K.; Schache, H.; Sensfuss, S.; Schrodner,
M. Sol. Energy Mater. Sol. Cells 2009, 93, 476–483.
(1) Taube, R. Z. Chem. 1963, 3, 194.
(2) Koichi, T. In Solvent-free Organic Synthesis; Wiley: New York, 2005;
pp i-viii.
(17) (a) Krebs, F. C. Sol. Energy Mater. Sol. Cells 2009, 93, 394–412. (b)
Krebs, F. C. Sol. Energy Mater. Sol. Cells 2009, 93, 1636–1641. (c) Krebs,
F. C. Org. Electron. 2009, 10, 761–768.
(18) Tau, P.; Nyokong, T. Dalton Trans. 2006, 4482–4490.
(19) Winter, G.; Heckmann, H.; Haisch, P.; Eberhardt, W.; Hanack, M.;
Luer, L.; Egelhaaf, H. J.; Oelkrug, D. J. Am. Chem. Soc. 1998, 120, 11663–
11673.
(3) Haisch, P.; Winter, G.; Hanack, M.; Luer, L.; Egelhaaf, H. J.;
Oelkrug, D. Adv. Mater. 1997, 9, 316.
(4) (a) Law, W. F.; Liu, R. C. W.; Jiang, J. H.; Ng, D. K. P. Inorg. Chim.
Acta 1997, 256, 147–150. (b) Law, W. F.; Lui, K. M.; Ng, D. K. P. J. Mater.
Chem. 1997, 7, 2063–2067.
(20) (a) Arslanoglu, Y.; Hamuryudan, E. Dyes Pigm. 2007, 75, 150–155.
€
(b) Arslanoglu, Y.; Sevim, A. M.; Hamuryudan, E.; Gul, A. Dyes Pigm. 2006,
68, 129–132.
(5) Yao, J. C.; Yonehara, H.; Pac, C. J. Bull. Chem. Soc. Jpn. 1995, 68,
1001–1005.
DOI: 10.1021/jo1011637
r
Published on Web 10/28/2010
J. Org. Chem. 2010, 75, 7893–7896 7893
2010 American Chemical Society

Mayukh et al.
JOCNote
SCHEME 1. Synthesis of Pn 1a-e and TiOPc 2a-e
FIGURE 1. (a) GPC in THF and (b) UV-vis in DCM (ca. 10-6 M)
for TiOPc 2a-e.
The particular TiOPc derivatives we report are octakis(alkylthio)
derivatives,20,21 substitutent moieties that serve to render the
TiOPc soluble in a wide range of organic solvents while bath-
ochromically shifting the Q-band relative to the parent chro-
mophore. They are also responsible for secondary sulfur-
sulfur noncovalent interactions that can strongly influence
condensed-phase organization.22
were higher than reported for a similar TiOPc prepared using
the method reported by Yao.4a,5 Purification of 2a-e was
accomplished by a combination of precipitation and flash
chromatography. The deviation from the purple color of
parent unmodified TiOPc chromophore is believed to be due
the bathochromic effect of the alkylthio substituents at the
peripheral positions.20b
We chose to prepare alkylthio-substituted TiOPc deriva-
tives because of the possibility of optimized condensed-phase
organization and near-IR absorbance for use in organic solar
cells. Pn derivatives 1a-e were synthesized via nucleophilic
aromatic substitution of dichlorophthalonitrile with alkyl
thiols under basic conditions (Scheme 1). Intensely colored
impurities were removed upon treatment with activated
charcoal, and Pns 1a-e were obtained as colorless solids in
good yields after purification by flash chromotography.
We were prompted to attempt the solvent-free conditions
described herein upon observing a trend toward lower amounts
of H2Pc formed during the cyclization reaction with lower
concentrations of 1-pentanol used in the reaction. The intense
green color of H2Pc masks the dark, nearly black color of the
TiOPc (a near-IR absorber) when they form as a mixture, and
the presence of H2Pc is discerned by TLC or mass spectrometry
(see the Supporting Information). Attempts to separate the
mixtures of H2Pc and TiOPc failed due to coelution.
Macrocyclization of 1a-e to the corresponding Pc com-
pounds was accomplished by heating the Pn to its melting
point and subsequently adding urea and Ti(iOPr)4 to the
molten Pn. The reaction mixture was then maintained at
150 °C for 24 h. We found no evidence of H2Pc by TLC or mass
spectrometry when the reaction was performed in a urea melt
(see the Supporting Information). Presumably, the higher
concentration of reactants under solvent-free conditions
favorably affects the reaction kinetics leading only to the
metalated product. TiOPc compounds 2a-e were obtained
as intensely colored, nearly black solids in moderate yields of
34-42%, except for 2a, which consistently was obtained in a
much lower yield of 16%. In the case of 2b-e, these yields
All compounds were characterized by gel permeation
chromatography (GPC), mass spectrometry, UV-vis spec-
troscopy, NMR, and thermal and elemental analysis (see the
Supporting Information). Elemental analysis results are all
in close agreement with the expected values. The GPC traces
of octakis(alkylthio) Pc compounds 2a-e were indicative of
monodisperse materials, and a hydrodynamic size increase
was observed commensurate with the increase in molecular
weight on proceeding from 2a f 2e (Figure 1a). Because of
1
solution aggregation only H NMR could be obtained for
2a-e.
The appearance of the UV-vis spectra was similar for
2a-e, consistent with the identical nature of the central Pc
chromophore in all five compounds (Figure 1b). Metalation
of the macrocycle was confirmed by the collapsed Q-band at
736 nm for all Pcs, with associated vibronic bands at 661 and
700 nm. The absorptivities at the λmax of the Q-bands of were
all ca. 2 ꢀ 105 M-1 cm-1 as determined by Beer’s law analysis
(see the Supporting Information). The observed bathochro-
mic shift of the Q-band, about 36 nm relative to the unsub-
stituted TiOPc,9 arising from the mixing of 3p orbital on
sulfur with π-orbitals of the phthalocyanine core,23 is typical
of a Pc substituted with alkylthio groups at the peripheral
positions.24
The octakis(alkylthio) TiOPcs 2a-e reported here exhibit
appreciable solubility in both CHCl3 and THF, freely soluble at
least up to the 10-2 M concentration range, in contrast to
unmodified TiOPc which is poorly soluble in organic solvents
such as CHCl3 (ca. 8 ꢀ 10-5 M) and THF (ca. 2 ꢀ 10-5 M). In
addition, 2a-e showed no signs of aggregation in CHCl3 in the
micromolar range (e10-5 M), as evident from a lack of
broadening of the Q-band maxima at 739 nm in the UV-vis
spectra as well as a linear response in the corresponding Beer’s
€
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(21) (a) Dundar, D.; Can, H.; Atilla, D.; Gurek, A. G.; Ozturk, Z. Z.;
Ahsen, V. Polyhedron 2008, 27, 3383. (b) Kimura, T.; Kumasaka, J.;
Namauo, T. Eur. J. Org. Chem. 2008, 5079. (c) Santiago, J.; Sugino, T.;
Shimizu, Y. Chem. Lett. 1998, 661. (d) Tau, P.; Nyokong, T. J. Porphyrins
Phthalocyanines 2006, 10, 1040.
(23) Guo, L.; Ellis, D. E.; Hoffman, B. M.; Ishikawa, Y. Inorg. Chem.
1996, 35, 5304.
(24) Kobayashi, N.; Ogata, H.; Nonaka, N.; Luk’yanets, E. A. Chem.;
Eur. J. 2003, 9, 5123.
(22) Minch, B. A.; Xia, W.; Donley, C. L.; Hernandez, R. M.; Carter, C.;
Carducci, M. D.; Dawson, A.; O’Brien, D. F.; Armstrong, N. R. Chem.
Mater. 2005, 17, 1618.
7894 J. Org. Chem. Vol. 75, No. 22, 2010

Mayukh et al.
JOCNote
from cyclization of the corresponding phthalonitriles in
molten urea. We are currently investigating effect of alkylthio
chain length on the behavior of TiOPcs in the condensed phase
with the possibility of retaining the near-IR absorption of the
unmodified TiOPc.
Experimental Section
4,5-Bis(hexylthio)phthalonitrile (1a). A mixture of hexane-1-
thiol (6.0 g, 50.7 mmol), K2CO3 (14.0 g, 101.3 mmol), and
DMSO (200 mL) was stirred at ambient temperature for 30 min.
Dichlorophthalonitrile (4.0 g, 20.3 mmol) was added, and the
reaction mixture was maintained at 80 °C for 12 h. The reaction
mixture was allowed to cool to ambient temperature, quenched
with brine (100 mL), extracted into ether (2ꢀ100 mL), and washed
with water (2 ꢀ 100 mL), and the solvent was removed under
reduced pressure to obtain a yellow solid. Activated carbon was
used to decolorize the compound, when necessary. Further
purification using flash chromatography (SiO2, 10:90 ethyl
acetate/hexanes) afforded 1a (5.17 g, 70%) as a colorless solid:
mp 70-72 °C (lit.29 mp 71 °C); 1H NMR (500 MHz, CDCl3) δ
7.38 (s, 2H), 3.00-2.97 (t, J = 15 Hz, 4H), 1.75-1.69 (p, J =
30 Hz, 4H), 1.50-1.44 (m, 4H), 1.32-1.29 (m, 8H), 0.90-0.87
(m, 6H); 13C NMR (125 MHz, CDCl3) δ 144.2, 128.1, 115.6,
111.0, 32.7, 31.2, 28.5, 28.0, 22.4, 13.9; MS (EI) m/z 360.1 [M]þ,
C20H28N2S2 requires 360.1. Anal. Calcd for C20H28N2S2: C,
66.62; H, 7.83; N, 7.77. Found: C, 66.74; H, 8.06; N, 8.02.
4,5-Bis(heptylthio)phthalonitrile (1b)29. Following the proce-
dure for 1a, heptane-1-thiol (4.7 g, 35.5 mmol), K2CO3 (7.0 g,
50.7 mmol), and dichlorophthalonitrile (2.0 g, 10.1 mmol), after
flash chromatography (SiO2, 10:90 ethyl acetate/hexanes), af-
forded 1b (3.3 g, 84%) as a colorless solid: mp 72-74 °C (lit.29
mp 61 °C); 1H NMR (500 MHz, CDCl3) δ 7.39 (s, 2H),
3.00-2.98 (t, J = 10 Hz, 4H), 1.76-1.70 (p, J = 30 Hz, 4H),
1.48-1.44 (p, J = 20 Hz, 4H), 1.34-1.26 (m, 12H), 0.88 (m, 6H);
13C NMR (500 MHz, CDCl3) δ 144.2, 128.1, 115.6, 111.0, 32.7,
31.6, 28.8, 28.7, 28.1, 22.5, 14.0; MS (EI) m/z 388.2 [M]þ,
C22H32N2S2 requires 388.2. Anal. Calcd. for C22H32N2S2: C,
67.99; H, 8.30; N, 7.21. Found: C, 67.67; H, 8.10; N, 7.21.
4,5-Bis(octylthio)phthalonitrile (1c)30. Following the proce-
dure for 1a, octane-1-thiol (2.3 g, 15.6 mmol), K2CO3 (8.6 g, 62.4
mmol), and dichlorophthalonitrile (1.2 g, 6.2 mmol), after flash
chromatography (SiO2, 10:90 ethyl acetate/hexanes), afforded
1c (2.2 g, 86%) as a colorless solid: mp 56-58 °C (lit.30 mp 62 °C);
1H NMR (500 MHz, CDCl3) δ 7.42 (s, 2H), 3.04-3.01 (t, J =
14.5 Hz, 4H), 1.79-1.73 (p, J = 29.5 Hz, 4H), 1.53-1.47 (m,
4H), 1.33-1.29 (m, 16H), 0.91-0.88 (m, 6H); 13C NMR (500
MHz, CDCl3) δ 144.6, 128.5, 116.0, 111.4, 33.2, 32.2, 29.55,
29.52, 29.3, 28.5, 23.1, 14.5; MS (EI) m/z 416.2 [M]þ,
C24H36N2S2 requires 416.2. Anal. Calcd. for C24H36N2S2: C,
69.18; H, 8.71; N, 6.72. Found: C, 69.17; H, 8.90; N, 6.57.
4,5-Bis(nonylthio)phthalonitrile (1d). Following the procedure
for 1a, nonane-1-thiol (4.2 g, 26.6 mmol), K2CO3 (5.3 g, 38.0
mmol), and dichlorophthalonitrile (1.5 g, 7.0 mmol), after flash
chromatography (SiO2, 3:97 ethyl actetate/hexanes), afforded
1d (2.6 g, 78%) as a colorless solid: mp 74-76 °C; 1H NMR (500
MHz, CDCl3) δ 7.38 (s, 2H), 3.00-2.98 (t, J = 10 Hz, 4H),
1.74-1.71 (p, J = 15 Hz, 4H), 1.48-1.45 (p, J = 15 Hz, 4H),
1.34-1.27 (m, 20H), 0.88-0.86 (t, J = 10 Hz, 6H); 13C NMR
(500 MHz, CDCl3) δ 144.2, 128.1, 115.6, 111.0, 32.8, 31.9, 29.4,
29.2, 29.1, 28.9, 28.1, 22.7, 14.1; MS (EI) m/z 444.2 [M]þ,
FIGURE 2. MALDI-TOF mass spectometry data for 2d in (a)
DTH and (b) HABA.
law plots. Aggregation of 2a-e was evident at even lower
concentrations in THF, with an aggregate band, apart from
the Q-band maxima at 731 nm, at 815 nm in the UV-vis
spectra. Despite the tendency to aggregate in solution, no liquid
crystalline behavior was evident from the differential scanning
calorimetry (DSC) traces (see the Supporting Information).
The MALDI-TOF mass spectrometry characterization of
2a-e revealed evidence of adduct formation between the
analyte compounds and the matrix material. With two
different matrices, dithranol (DTH) and 2-(4-hydroxy-
phenylazo)benzoic acid (HABA), we observed that the base
or otherwise significant peak in the mass spectra of 2a-e
corresponded to an adduct of the matrix material and the
respective TiOPc derivative with loss of OH (Figure 2). A
likely possibility is in situ chemical reaction between 2a-e
and the MALDI matrices. Indeed, the axial substitution of
TiOPcs with catechols and related diols is well established4a,25
and has even been used for the recognition of chiral
catechols.26 Axial substitution of TiOPc to form 5- and
7-membered chelate rings with diols such as catechol and
2,20-biphenol, respectively, has been reported.27 However,
reaction between DTH and TiOPcs, which leads to the
formation of a 6-membered chelate, is unprecedented. We
attempted to prepare the DTH-TiOPc adduct (2a-DTH) in
refluxing CHCl3 but obtained only insoluble product that
resisted characterization. An attempt to produce an isolable
HABA-2a adduct was similarly unsuccessful. However, a
hetrocylic complex has been reported that supports the
proposed structure of the HABA-TiOPc adduct (see Sup-
porting Information).28
In summary, we have reported a solvent-free route to
soluble TiOPc derivatives that eliminates the formation of
H2Pc side product. With this method, we have prepared a
series of octakis(alkylthio)-substituted TiOPc derivatives
(25) (a) Goedken, V. L.; Dessy, G.; Ercolani, C.; Fares, V.; Gastaldi, I.
Inorg. Chem. 1985, 24, 991. (c) Barthel, M.; Dini, D.; Vagin, S.; Hanack, M.
Eur. J. Org. Chem. 2002, 3756. (d) Barthel, M.; Dini, D.; Vagin, S.; Hanack,
M. Eur. J. Org. Chem. 2008, 3209.
(26) (a) Muranaka, A.; Yoshida, K.; Shoji, T.; Moriichi, N.; Masumoto,
S.; Kanda, T.; Ohtake, Y.; Kobayashi, N. Org. Lett. 2006, 8, 2447. (b)
Muranaka, A.; Okuda, M.; Kobayashi, N.; Somers, K.; Ceulemans, A.
J. Am. Chem. Soc. 2004, 126, 4596.
(27) (a) Kobayashi, N.; Muranaka, A.; Ishii, K. Inorg. Chem. 2000, 39,
2256. (b) Kobayashi, N.; Muranaka, A. Chem. Commun. 2000, 19, 1855.
(28) Sherif, O. E.; Abd El-Fattah, H. M.; El-Ajily, M. M. J. Thermal Anal.
Calorimetry 2003, 74, 181.
(29) Ahmida, M.; Larocque, R.; Ahmed, M. S.; Vacaru, A.; Donnio, B.;
Guillon, D.; Eichhorn, S. H. J. Mater. Chem. 2010, 20, 1292.
(30) del Rey, B.; Keller, U.; Torres, T.; Rojo, G.; Agullo-Lopez, F.;
Nonell, S.; Marti, C.; Brasselet, S.; Ledoux, I.; Zyss, J. J. Am. Chem. Soc.
1998, 120, 12808.
J. Org. Chem. Vol. 75, No. 22, 2010 7895

Mayukh et al.
JOCNote
C26H40N2S2 requires 444.2. Anal. Calcd for C26H40N2S2: C,
70.22; H, 9.07; N, 6.30. Found: C, 69.92; H, 9.12; N, 6.39.
4,5-Bis(decylthio)phthalonitrile (1e). Following the procedure
for 1a, decane-1-thiol (2.7 g, 15.6 mmol), K2CO3 (8.6 g, 62.4
mmol), dichlorophthalonitrile (1.2 g, 6.2 mmol), and DMSO
(50 mL), after flash chromatography (SiO2, 10:90 ethyl acetate/
hexanes), afforded 1e (2.25 g, 76%) as a colorless solid:
mp 54-56 °C; 1H NMR δ (500 MHz, CDCl3) 7.38 (s, 2H),
3.00-2.97 (t, J = 14.5 Hz, 4H), 1.75-1.69 (p, J = 30 Hz, 4H),
1.47-1.43 (m, 4H), 1.33-1.25 (m, 24H), 0.87-0.84 (m, 6H): mp.
54-56 °C; 13C NMR (125 MHz, CDCl3) δ 144.6, 128.5, 116.0,
111.5, 33.2, 32.3, 29.9, 29.8, 29.7, 29.5, 29.3, 28.5, 23.1, 14.5; MS
(EI) m/z 472.2 [M]þ, C28H44N2S2 requires 472.2. Anal. Calcd for
C28H44N2S2: C, 71.13; H, 9.38; N, 5.93. Found: C, 70.81; H,
9.46; N, 6.10.
[(MHABA) - OH]þ, C101H137N10O3S8Ti requires 1841.8. Anal.
Calcd for C88H128N8OS8Ti: C, 65.31; H, 7.97; N, 6.92. Found: C,
64.86; H, 7.95; N, 7.02.
2,3,9,10,16,17,23,24-Octakis(octylthio)phthalocyaninatooxotita-
nium(IV) (2c). Following the procedure for 2a, Pn 3 (0.88 g, 2.1
mmol), urea (0.06 g, 1.0 mmol), and Ti(iOPr)4 (0.31 g, 1.1 mmol)
after flash chromatography afforded 2c (0.31 g, 34%) as a black
solid: UV (λmax, nm) 736; 1HNMRδ(500 MHz, CDCl3) 8.73-8.70
(br s, 8H), 3.47 (br s, 16H), 2.04 (br s, 16H), 1.93-1.90 (br s, 16H),
1.53-1.24 (br m, 64H), 0.90 (m, 24H); MS (MALDI) m/z 1730.8
[M þ H]þ, C96H145N8OS8Ti requires 1730.8; 1938.9 [(MDTH) -
OH]þ, C110H153N8O3S8Ti requires 1938.9; 1953.1 [(MHABA) -
OH]þ C109H153N10O3S8Ti requires 1953.9. Anal. Calcd for C96H145
-
N8OS8Ti: C, 66.63; H, 8.39; N, 6.47. Found: C, 66.23; H, 8.46; N,
6.61
2,3,9,10,16,17,23,24-Octakis(hexylthio)phthalocyaninatooxotita-
nium(IV) (2a)20. A mixture of Pn 1a (4.1 g, 11.4 mmol) and urea
(0.3 g, 5.7 mmol) was heated under argon to the melting point of the
Pn (70 °C). Ti(iOPr)4 (1.62 g, 5.70 mmol) was then added via
syringe to the melt, and the temperature was raised and maintained
at 150 °C for 24 h. The reaction mixture was allowed to cool to
room temperature, precipitated in methanol (100 mL), and cen-
trifuged. The precipitate was dispersed and centrifuged in water
(40 mL) and methanol (40 mL), sequentially. Finally, the brown-
black precipitate was dispersed in acetone, filtered, and washed
copiously with acetone until the filtrate was colorless. The pre-
cipitate was air-dried to obtain a black powder, which was then
redissolved in a minimum amount of DCM and mixed with silica
gel (30 g). Solvent was removed from the silica slurry on the
rotovap, and then it was further dried under high vacuum to obtain
a free-flowing powder, which was subjected to flash chromatogra-
phy (SiO2, 0:100 to 50:50 ethyl acetate/hexanes). After concentra-
tion of the eluted product, it was dispersed in acetone and then
centrifuged. The precipitate was dried at 35-40 °C for 24 h under
vacuum to obtain 2a (0.73 g, 16%) as a black solid: UV (λmax, nm)
736; 1HNMRδ(500 MHz, CDCl3) 8.82-8.78 (br s, 8H), 3.56-3.45
(br s, 16H), 2.07 (br s, 16H), 1.75-1.68 (br s, 16H), 1.64-1.47 (br s,
2,3,9,10,16,17,23,24-Octakis(nonylthio)phthalocyaninatooxotita-
nium(IV) (2d). Following the procedure for 2a, Pn 1d (0.80 g, 1.50
mmol), urea (0.05 g, 0.8 mmol), and Ti(iOPr)4 (0.37 g, 1.3 mmol)
after flash chromatography afforded 2d (0.35 g, 42%) as a black
1
solid: UV (λmax, nm) 736; H NMR δ (500 MHz, CDCl3) 8.73
(br s, 8H), 3.50 (br s, 16H), 2.06 (br s, 16H), 1.95 (br s, 16H),
1.75-1.24 (br m, 80H), 0.87-0.85 (m, 24H); MS (MALDI)
m/z 1842.9 [M þ H]þ, C104H161N8OS8Ti requires 1843.0; 2051.1
[(MDTH) - OH]þ, C118H169N8O3S8Ti requires 2051.1; 2066.2
[(MHABA) - OH]þ, C117H169N10O3S8Ti requires 2066.1. Anal.
Calcd. for C104H160N8OS8Ti: C, 67.78; H, 8.75; N, 6.08. Found: C,
67.39; H, 8.84; N, 6.12
2,3,9,10,16,17,23,24-Octakis(decylthio)phthalocyaninatooxotita-
nium(IV) (2e). Following the procedure for 2a, Pn 1e (1.23 g, 2.60
mmol), urea (0.08 g, 1.3 mmol), and Ti(iOPr)4 (0.37 g, 1.3 mmol)
after flash chromatography afforded 2e (0.45 g, 35%) as a black
solid: UV (λmax, nm) 736.5; 1H NMR δ (500 MHz, CDCl3) 8.73 (br
s, 8H), 3.50 (br s, 16H), 2.06 (br s, 16H), 1.95 (br s, 16H), 1.75-1.24
(br m, 96H), 0.87-0.85 (m, 24H); MS (MALDI) m/z 1955.3 [M þ
H]þ, C112H177N8OS8Ti requires 1954.1; [(MDTH) - OH]þ 2163.3,
C
C
126H185N8O3S8Ti requires 2163.2; 2178.4 [(MHABA) - OH]þ,
125H185N10O3S8Ti requires 2178.1. Anal. Calcd for C112H176N8-
32H), 0.98 (m, 24H); MS (MALDI) m/z 1505.7 [M þ H]þ, C80H113
-
OS8Ti: C, 68.81; H, 9.07; N, 5.73. Found: C, 68.44; H, 8.93; N, 5.82.
N8OS8Ti requires 1505.6; 1714.9 [(MDTH)-OH]þ, C94H121N8O3-
S8Ti requires 1714.7; 1730.0 [(MHABA)-OH]þ, C93H121N10O3S8Ti
requires 1730.6. Anal. Calcd for C80H112N8OS8Ti: C, 63.79; H, 7.50;
N, 7.44. Found: C, 63.42; H, 7.54; N, 7.50.
2,3,9,10,16,17,23,24-Octakis(heptylthio)phthalocyaninatooxotita-
nium(IV) (2b). Following the procedure for 2a, Pn 1b (1.00 g, 2.57
mmol), urea (0.08 g, 1.3 mmol), and Ti(iOPr)4 (0.37 g, 1.3 mmol)
after flash chromatography afforded 2b (0.44 g, 42%) as a black
solid: UV (λmax, nm) 736; 1HNMRδ(500 MHz, CDCl3) 8.82-8.81
(br s, 8H), 3.61-3.35 (br s, 16H), 2.15 (br s, 16H), 1.71-1.70 (br s,
16H), 1.49-1.16 (br m, 48H), 0.92 (m, 24H); MS (MALDI) m/z
1618.8 [M þ H]þ, C88H129N8OS8Ti requires 1618.7; 1826.7
[(MDTH) - OH]þ, C102H137N8O3S8Ti requires 1826.8; 1841.9
Acknowledgment. We acknowledge financial support
from the National Science Foundation (CHE-0719437) for
personnel (M.M.) and the Center for Interface Science: Solar
Electric Materials (CIS:SEM), an Energy Frontier Research
Center funded by the U.S. Department of Energy, Office of
Science, Office of Basic Energy Sciences, under Award No.
DE-SC0001084 for materials.
Supporting Information Available: Experimental details
and characterization data for all new compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
7896 J. Org. Chem. Vol. 75, No. 22, 2010