Synthesis and crystal structure of novel, soluble titanyl phthalocyanines

Article abstract of DOI:10.1016/j.ica.2011.01.099

Novel titanyl phthalocyanines titanyl-tetrakis-(1,1,4,4-tetramethyl-6,7- tetralino)-porphyrazine (1), titanyl-2,3,9,10,16,17,23,24-octakis(phenylethynyl) -phthalocyanine (2a), titanyl-2,3,9,10,16,17,23,24-octakis((4-tert-butylphenyl) ethynyl)-phthalocyani

Full text of DOI:10.1016/j.ica.2011.01.099

Inorganica Chimica Acta 374 (2011) 119–126
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Synthesis and crystal structure of novel, soluble titanyl phthalocyanines
⇑
Elisabeth Seikel, Michaela Grau, Ralf Käsmarker, Benjamin Oelkers, Jörg Sundermeyer
Fachbereich Chemie and Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 4 February 2011
Novel titanyl phthalocyanines titanyl-tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine (1), tita-
nyl-2,3,9,10,16,17,23,24-octakis(phenylethynyl)-phthalocyanine (2a), titanyl-2,3,9,10,16,17,23,24-octa-
kis((4-tert-butylphenyl)ethynyl)-phthalocyanine (3a), titanyl-(2,3,9,10,16,17,23,24-octakis(phenylethyl))-
phthalocyanine (2b) and titanyl-(2,3,9,10,16,17,23,24-octakis((4-tert-butylphenyl)ethyl)-phthalocyanine
(3b) were prepared by reductive cyclotetramerisation of the respective dinitrile precursors in the presence
of a titanium(IV) template. The spectroscopic properties were examined by UV–Vis and IR techniques. Sol-
uble compounds 1, 2b and 3b were characterized by 1H and 13C NMR spectroscopy and show good stability
towards thermal degradation. The molecular structure of 1 was determined, thus being one of the few
examples of soluble phthalocyanines with a low grade of aggregation characterized by single crystal
Dedicated to Professor Dr. Wolfgang Kaim
on the occasion of his 60th birthday.
Keywords:
Titanyl phthalocyanine
Crystal structure
UV–Vis spectroscopy
NMR spectroscopy
ꢀ
X-ray diffraction. Compound 1 crystallizes in the triclinic space group P1, and the molecules arrange in a
coplanar, slipped-stacked structure.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
application in many fields of light driven processes such as in the
manufacture of non-toxic organic photoconductors in electro-
Metal free phthalocyanine PcH2 is a porphyrinoid macrocycle
prepared by reductive tetramerization of four phthalonitrile units
[1–3]. The valence structure of phthalocyanine was first recognized
by Linstead et al. in 1934 [4]. Since then, metal phthalocyanines
graphic printing devices [10], in CD-R optical data storage [11],
and as optical limiting materials [12]. The evaluation of the solid
state structure of titanyl phthalocyanines is essential, as different
arrangement of these molecules in the lattice structure of polymor-
phic forms influences the optoelectronic properties of [PcTiO] [13–
15]. However, while the effect of equatorial n-alkyl substitution on
solubility, on UV–Vis characteristics and photostability has previ-
ously been reported by Hanack et al. [9,16–18], no crystal structure
of a soluble titanyl phthalocyanine has been published so far. With
respect to the large number of soluble phthalocyanines, surpris-
ingly little is known on their molecular and lattice structures in
general [19–22]. The presence of either isomeric mixtures and/or
disorder in long-chain alkyl substituents tends to prevent single
crystal XRD analyses. As an extension of our studies on partly sol-
uble parent titanium phthalocyanines with axial sulfido, imido,
phenylendiamido and ureato ligands [23–25] we became inter-
ested to design and fully characterize isomerically pure octasubsti-
tuted soluble titanyl phtalocyanines which are expected to be air
stable, suitable for spin coating of surfaces, and for derivatisation
of the axial oxo ligand.
[PcM] have been described for most metals. The extended 18
p
electron aromatic system, its non-innocent ligand character
(Pc2ꢀ/1ꢀ) and last but not least the lattice-packing in the solid state
are responsible for physical characteristics, such as the intense col-
our and chemically, thermally or light induced semi-conducting
properties of these dyes. Due to p-stacking unsubstituted phthalo-
cyanines are insoluble in common organic solvents which limits
the processability, derivatisation and the characterization of this
class of compounds [1–3]. By introduction of bulky substituents
at the ligand periphery intermolecular interaction of the
p systems
can be reduced, phthalocyanines become soluble and 13C NMR
spectra are available in common organic solvents. As a conse-
quence, a variety of phthalodinitriles bearing alkyl, alkoxy and
other functional groups have been synthesized and employed in
cyclotetramerization reactions [2,5]. While template reactions of
mono-substituted dinitriles typically lead to mixtures of
regioisomers [R1PcM], bis-substituted dinitriles, depending on
the substitution pattern, can lead to uniform D4h symmetrical com-
pounds [1,4-R2PcM] or [2,3-R2PcM] (Fig. 1).
As synthetic strategy we decided to use alkynyl substituted
dinitriles 5a and 6a prepared via Sonogashira coupling [26] as
well as the reduced alkyl analogues 5b and 6b (Fig. 2). Com-
pounds 5a and 5b have been employed by Leznoff et al. to obtain
the corresponding metal free phthalocyanines [27] as well as
unsymmetrical push–pull-macrocycles [28]. As the synthesis of
5a, 5b, 6a and 6b involves metal-catalyzed reactions which are
difficult to handle in large scale, we decided to also employ
The parent titanyl phthalocyanine, [PcTiO] [6,7] and its ring-
substituted alkyl or alkoxy derivatives [RnPcTiO] [8,9] have found
⇑
Corresponding author. Tel.: +49 6421 28 25693.
E-mail address: jsu@staff.uni-marburg.de (J. Sundermeyer).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.01.099

120
E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
2.2. 4,5-Bis(phenylethyl)phthalodinitrile (5b)
Three hundred milligrams of 4,5-bis(phenylethynyl)phthalodi-
nitrile 5a (0.91 mmol, 1.00 equiv) was dissolved in 20 mL of ethyl
acetate. Ninety-one milligrams of Pd/C (10%) were added. The reac-
tion flask was purged with H2 and the mixture was stirred under
H2 atmosphere (1 bar) at room temperature for 48 h. The catalyst
was removed by filtration and the volatiles were removed under
reduced pressure. The resulting brown solid was washed with hex-
ane, recrystallized from methanol and dried under vacuum. Yield:
268 mg, 88%. 1H NMR (300 MHz, CDCl3) d = 7.41 (s, 2H), 7.13–7.25
3
(m, 6H), 7.00 (d, JHH = 6.7 Hz, 4H), 2.84–2.89 (m, 4H), 2.75–2.80
(m, 4H) ppm. 13C NMR (75 MHz, CDCl3) d = 146.3, 139.9, 134.4,
128.8, 128.4, 126.8, 115.7, 113.3, 36.5, 34.4 ppm. EI-HRMS+ m/z
(%) = 336.1639 (100) [M+], C24H20N2 requires 336.1626 (100).
Fig. 1. Substituted D4h symmetrical metal phthalocyanine.
2.3. 4,5-Bis(4-tert-butylphenylethyl)phthalodinitrile (6b)
6,7-dicyano-1,1,4,4-tetramethyltetraline (4) as starting material.
Luk’yanets et al. used 4 in the preparation of metal-free tetra-
(1,1,4,4-tetramethyl-6,7-tetralino)porphyrazine and correspond-
ing zinc, copper, vanadyl and cobalt complexes [29–31]. We
hoped that cyclic alkyl substituents are more rigid than non-
cyclic ones, which should facilitate crystallization and enhance
stability of these titanyl phthalocyanines.
4,5-Bis((4-tert-butylphenyl)ethynyl)phthalodinitrile 6a (1.09 g,
2.47 mmol, 1.00 equiv) were dissolved in 30 mL of ethyl acetate.
One hundred and fifty milligrams of Pd/C (10%) were added. The
reaction flask was purged with H2 and the mixture was stirred un-
der H2 atmosphere (1 bar) at room temperature for 48 h. The cata-
lyst was removed by filtration and the volatiles were removed
under reduced pressure. The brown solid was washed with hexane,
recrystallized from methanol and dried under vacuum. Yield:
937 mg, 85%. 1H NMR (300 MHz, CDCl3) d = 7.48 (s, 2H), 7.32 (d,
2. Experimental
3
3JHH = 8.5 Hz, 4H), 7.02 (d, JHH = 8.5 Hz, 4H), 2.91–2.94 (m, 4H),
2.1. General procedures
2.79–2.85 (m, 4H), 1.31 (s, 18H) ppm. 13C NMR (75 MHz, CDCl3)
d = 149.9, 146.4, 136.8, 134.4, 128.2, 125.7, 115.8, 113.3, 36.0,
34.6, 34.5, 31.5 ppm. EI-HRMS+ m/z (%) = 448.2867 (87) [M+],
Dinitriles 4 [29,32,33], 5a [26,34] and 6a [26,34] were prepared
according to literature procedures. Compound 4 was purified by
column chromatography (silica gel, CH2Cl2) prior to use.
Chloronaphthalene was obtained from Acros as a mixture of 1-
chloronaphthalene (90%) and 2-chloronaphthalene (10%). Chloro-
naphthalene and 1-octane were dried with CaH2, distilled and
stored over molecular sieves (4 Å). TiCl4 and Ti(OnBu)4 were ob-
tained from Acros and stored under inert gas. Pd/C (10%) was ob-
tained from Merck. Preparations were carried out under dry
argon atmosphere using standard Schlenk or glove box techniques.
The electronic spectra were recorded on a Shimadzu UV-1601
PC spectrophotometer. IR spectra were recorded on a Bruker IFS
588 spectrometer. EI mass spectra were taken on a Finnigan
MAT95 spectrometer (E = 70 eV). APCI mass spectra were taken
on a Finnigan LTQ-FT spectrometer using dichloromethane as sol-
vent. MALDI-TOF mass spectra were taken on a Bruker Biflex III
using pyrene as matrix. Elemental analyses of C, H and N elements
was carried out using an Elementar Vario EL. 1H and 13C NMR spec-
tra were recorded on a Bruker AMX 500. Thermal gravimetric anal-
yses (TGA) were carried out using a TGA/SDTA 851, Mettler. The
heating range was from 25 to 800 °C with a heating rate of
C32H36N2 requires 448.2878 (100).
2.4. Titanyl-tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)porphyrazine
(1)
A mixture of 5.23 g of 4 (21.95 mmol, 4.15 equiv), 700 mg of
urea (11.66 mmol, 2.20 equiv) and 1.80 g of Ti(OnBu)4 (5.29 mmol,
1.00 equiv) in 4.5 mL of 1-octanol was stirred for 6 h in a pre-
heated oil bath at 150 °C. The reaction mixture turned dark green.
After cooling, 60 mL of methanol were added and the mixture was
stirred at 60 °C for 30 min. The resulting green powder was col-
lected by filtration and successively extracted with methanol and
hexane. The product was dried under vacuum at 150 °C. Yield:
1.70 g, 32%. Crystals suitable for X-ray diffraction were obtained
from a saturated solution in CHCl3 in the dark. Anal. Calc. for
C
64H72N8TiO (1017.18 g/mol): C, 75.35; H, 7.41; N, 10.98. Found:
C, 74.51; H, 7.21; N, 11.02%. 1H NMR (300 MHz, CDCl3) d = 9.62
(s, 8H), 2.08 (s, 16H), 1.89 (s, 24H), 1.81 (s, 24H) ppm. 13C NMR
(75 MHz, CDCl3) d = 152.2, 149.4, 135.0, 121.9, 36.1, 35.4, 33.0,
10 °C minꢀ1
.
32.8 ppm. IR m = 2959(s), 2922(s), 2860(m), 1616(w), 1493(m),
Fig. 2. Dinitriles investigated in this study.

E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
121
1320(s), 1306(s), 1188(w), 1113(w), 1071(s), 977(m,
m
Ti@O),
454(w) cmꢀ1. UV–Vis (chloronaphthalene) k = 751(m), 678(w),
388(s) nm. MALDI-TOF-MS+ m/z = 1377 [M+].
870(m), 763(w), 753(w), 708(m) cmꢀ1
.
UV–Vis (CH2Cl2) k =
713(s), 683(sh), 641(w), 348(m), 237(m) nm. MALDI-TOF-MS+
m/z = 1017 [M+], APCI-HRMS+ m/z = 1071.5380 [M++H], C64H73
-
N8TiO requires 1017.5383.
2.6. Titanyl-2,3,9,10,16,17,23,24-octakis((4-tert-butylphenyl)-
ethynyl)-phthalocyanine (3a)
2.5. Titanyl-2,3,9,10,16,17,23,24-octakis(phenylethynyl)-
phthalocyanine (2a)
A mixture of 400 mg of 6a (0.91 mmol, 4.00 equiv), 28 mg of
urea (0.46 mmol, 2.00 equiv) and 79 mg of Ti(OnBu)4 (0.23 mmol,
1.00 equiv) in 5 mL of 1-octanol was stirred overnight in a pre-
heated oil bath at 180 °C. The reaction mixture turned dark green.
The green solid was precipitated by adding 60 mL of hexane and
successively extracted with methanol, acetonitrile, hexane and
diethyl ether. The product was dried under vacuum. Yield:
200 mg, 48%. Anal. Calc. for C128H112N8OTi (1826.18 g/mol): C,
84.19; H, 6.18; N, 6.14. Found: C, 82.73; H, 6.70; N, 5.80%. IR
A mixture of 600 mg of 5a (1.83 mmol, 4.00 equiv), 55 mg of
urea (0.92 mmol, 2.00 equiv) and 171 mg of Ti(OnBu)4 (0.50 mmol,
1.00 equiv) in 5 mL of 1-octanol was stirred for 5 h in a pre-heated
oil bath at 150 °C and then at 100 °C overnight. The reaction mix-
ture turned dark green. The green solid was precipitated by adding
60 mL of methanol and successively extracted with methanol, ace-
tonitrile, hexane and diethyl ether. The product was dried under
vacuum. Yield: 500 mg, 72%. Anal. Calc. for
(1377.33 g/mol): C, 83.71; H, 3.51; N, 8.14. Found: C, 80.09; H,
3.70; N, 7.60%. IR = 1596(w), 1544(w), 1492(m), 1442(w),
1401(w), 1317(w), 1276(w), 1205(w), 1147(w), 1072(s), 969 (w,
Ti@O), 897(w), 881(w), 827(w), 750(s), 686(s), 530(w), 483(w),
C
96H48N8OTi
m = 2956(s), 2904(m), 2866(m), 2207(m), 1772(m), 1709(s),
1604(m), 1504(m), 1363(m), 1310(m), 1265(m), 1074(s),
1014(m), 828(s), 741(m), 560(m) cmꢀ1. UV–Vis (chloronaphtha-
lene) k = 759(s), 682(m), 642(m) nm. MALDI-TOF-MS+ m/z = 1827
[M+].
m
m
Scheme 1. Reduction of dinitriles 5a and 6a.
Scheme 2. Synthesis of 1, 2a and 3a (method i), and 2b and 3b (method ii).

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E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
2.7. Titanyl-2,3,9,10,16,17,23,24-octakis(phenylethyl)phthalocyanine
2.8. Titanyl-2,3,9,10,16,17,23,24-octakis((4-tert-butylphenyl)ethyl)-
(2b)
phthalocyanine (3b)
Four hundred and forty-one milligrams of 5b (1.31 mmol,
3.00 equiv) were dissolved in 5 mL of chloronaphthalene at room
temperature. Eighty-three milligrams of TiCl4 (0.44 mmol,
1.00 equiv) were added and the mixture was stirred for 4 h in a
pre-heated oil bath at 180 °C and then at 100 °C overnight. The
reaction mixture turned dark green. A green solid was precipitated
with 30 mL of hexane and successively extracted with methanol,
acetonitrile, hexane and diethyl ether. The product was dried un-
der vacuum. Yield: 380 mg, 61%. Anal. Calc. for C96H80N8OTi
(1409.58 g/mol): C, 78.73; H, 5.51; N, 7.65. Found: C, 75.66; H,
5.81; N, 7.34%. 1H NMR (300 MHz, CD2Cl2) d = 9.06 (s, 8H), 7.35
One hundred milligrams of 6b (0.22 mmol, 3.00 equiv) were
dissolved in 2 mL of chloronaphthalene at room temperature. Four-
teen milligrams of TiCl4 (0.07 mmol, 1.00 equiv) were added and
the mixture was stirred for 4 h in a pre-heated oil bath at 180 °C.
The reaction mixture turned dark green. A green solid was precip-
itated and successively extracted with methanol, acetonitrile, hex-
ane and diethyl ether. The product was dried under vacuum. Yield:
60 mg, 44%. Anal. Calc. for C96H80N8OTi (1858.43 g/mol): C, 80.35;
H, 7.59; N, 5.86. Found: C, 78.29; H, 7.23; N, 5.51%. 1H NMR
(300 MHz, CD2Cl2) d = 8.75 (s, 8H), 7.21–7.29 (m, 32H), 3.05–3.24
(br, 32H), 1.24 (s, 72H) ppm. 13C NMR (75 MHz, THF-d8)
d = 150.6, 148.1, 143.1, 138.5, 135.0, 127.6, 124.8, 122.5, 36.7,
(br, 40H), 3.27–3.42 (br, 32H) ppm. IR
2497(m), 1475(m), 1444(m), 1397(m), 1362(m), 1329(m),
1267(w), 1172(w), 1078(s), 1036(s), 972(w, Ti@O), 818(m), 748
(w), 557 (m) cmꢀ1
UV–Vis (chloronaphthalene) k = 712(s),
677(w), 643(w) nm. MALDI-TOF-MS+ m/z = 1410 [M+].
m = 2950(m), 2603(m),
35.6, 33.7, 30.6 ppm. IR
m = 2602(w), 2497(w), 1600(w), 1493(m),
m
1449(m), 1398(m), 1326(s), 1078(s), 965(m, mTi@O), 747(m),
.
727(m), 694 (s) cmꢀ1. UV–Vis (chloronaphthalene) k = 710(s),
682(w), 642(m) nm. MALDI-TOF-MS+ m/z = 1859 [M+].
Fig. 3. Prepared titanyl phthalocyanines.

E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
123
and 3b are soluble in organic solvents such as dichloromethane,
chloroform, benzene or THF. Compound 2b shows moderate solu-
bility in dichloromethane and THF. Complexes of the rigid planar
ligands 2a and 3a are insoluble in common organic solvents.
3.2. Spectroscopy and TGA
The insolubility of 2a and 3a does not allow characterization via
NMR spectroscopy. In 2b the flexible ethanediyl linkers enhance
the solubility, so that 1H NMR spectra could be recorded in CD2Cl2.
Compounds 1 and 3b show the best solubility, so that even well re-
solved 13C NMR spectra could be obtained (see Supporting infor-
mation). In all 1H NMR spectra, the characteristic downfield shift
of the Pc protons is observed, as they appear as singlets between
8.75 and 9.62 ppm. This is due to the strong ring current effect in
the aromatic macrocycles [26,37]. Due to the symmetry of 1, the
1H NMR spectrum in CDCl3 shows only four singlets (see Support-
ing information). The signal observed at 9.62 ppm refers to the
eight aromatic protons. The aliphatic protons are observed be-
tween 1.81 and 2.08 ppm. The methyl groups appear as a set of
two singlets which is not observed in compounds without axial
ligands such as the free ligand tetrakis-(1,1,4,4-tetramethyl-6,7-
tetralino)porphyrazine. This effect can be explained by the lower-
ing of the molecular symmetry imposed by the axial Ti@O group.
The upper and lower hemisphere of the macrocycle become
inequivalent and the methyl groups pointing towards the titanyl
moiety (endo) and those pointing away (exo) are located in differ-
ent chemical environments. This is also supported by the molecu-
lar structure of 1.
The UV–Vis spectrum of 1 in dichloromethane shows the typical
Q- and B-band absorptions for metal phthalocyanines (see Sup-
porting information). The relative absorption maxima (713, 348
and 237 nm) compare well with the values reported by Luk’yanets
et al. for the analogous C4v symmetric vanadyl-tetrakis-(1,1,
4,4-tetramethyl-6,7-tetralino)porphyrazine (716 and 353 nm)
[29,31]. The Q-band is shifted bathochromically compared to the
D4h symmetric zinc, copper and cobalt compounds (691, 691 and
682 nm, respectively) and the C2v symmetric protonated ligand
(712 and 678 nm).
Fig. 4. Comparison of UV–Vis spectra of 2a and 2b in chloronaphthalene.
3. Results and discussion
3.1. Preparation
The dinitriles 4 [29,31], 5a and 5b [26] were prepared according
to the literature procedures. The reduced dinitriles 5b and 6b were
prepared from 5a and 6a in an analogous manner to the prepara-
tion of 3,6-dialkyl substituted dinitriles reported by Hanack et al.
[35]. The reaction of the alkynyl substituted dinitriles with 1 atm
H2 and Pd/C in ethyl acetate afforded the desired products in 85–
88% yield (Scheme 1).
Unsubstituted titanyl phthalocyanine [PcTiO] can be synthe-
sized by reaction of phthalonitrile with TiCl3 [6], TiCl4 [7] or Ti(On-
Bu)4 [36] in high-boiling solvents. Analogously, 1, 2a and 3a were
prepared by the reaction of 4.00–4.15 equiv of the respective dinit-
rile, 1.00 equiv Ti(OnBu)4 and 2.00–2.20 equiv urea in 1-octanol at
150 °C (Scheme 2) and subsequent methanolysis. In the case of al-
kyl substituted dinitriles 5b and 6b, this strategy did not afford the
desired macrocycles. Therefore, the preparations of 2b and 3b were
carried out in chloronaphthalene at 180 °C using TiCl4 as metal
template. The products were obtained in 32–72% yield, and the
yields decrease as the solubility of the resulting phthalocyanines
increases (Fig. 3). The intensely green products were characterized
by MS, elemental analysis and spectral properties. Compounds 1
A comparison of the UV–Vis spectra of 2a and 2b shows the ef-
fect of solubility and the nature of peripheral substituents on the
spectroscopic properties (Fig. 4). Due to the poor solubility of 2a
the Q-band is much broader than in 1 or 2b. Also, the extinction
maximum is shifted bathochromically because of the conjugation
Fig. 5. Molecular structure of 1. Ellipsoids are shown at 50% probability. H atoms, disorder of the Ti@O moiety and solvent molecules are omitted for clarity.

124
E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
Table 1
was found to causes a shift of the Q-band maximum of about 70–
90 nm. In our case, the exchange of an ethanediyl for an ethynediyl
linker causes a bathochromic shift of about 40 nm.
The IR spectra of all compounds display absorptions represent-
ing the organic ligand and the band characteristic for the mTi@O
stretching mode at around 970 cmꢀ1 [26].
Crystal data and structure refinement for 1.
Empirical formula
Formula weight (g/mol)
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C67H75Cl9N8OTi
1375.30
100(2)
triclinic
ꢀ
P1
The group of Hanack found that long chain n-alkyl and n-alkoxy
substituted titanyl phthalocyanines cannot be sublimed in high
vacuum without thermal degradation [9]. For this reason, these
compounds could not be applied in physical vapour deposition
experiments which are used to prepare ordered mono- or multilay-
ers of metal Pc’s. Therefore we conducted TGA measurements to
investigate the thermal robustness of our compounds (see Sup-
porting information). Thermal degradation (1% weight loss) starts
at temperatures higher than 400 °C for both, the fully conjugated
alkynyl 2a and the cyclic alkyl derivatives and 1, whereas non-
cyclic alkyls 2b and 3b start to decompose above 300 °C. This
thermal stability of 1 and 2a in combination with a low grade of
aggregation of 1 in particular makes the latter an interesting target
for physical vapour deposition experiments. We attribute this
stability to the fact that incorporation of long and thermally labile
n-alkyl chains into the complex has been avoided without loosing
the substituents’ property to inhibit aggregation.
12.4678(15)
12.4707(16)
12.9692(18)
112.400(10)
109.897(10)
99.122(10)
1653.9(4)
b (Å)
c (Å)
a
(°)
b, (°)
c
(°)
V (Å3)
k (Å)
Mo Ka, 0.71073
Z
1
DCalc. (mg/m3)
1.381
0.542
l
(mmꢀ1
)
Crystal size (mm)
2h Range (°)
0.33 ꢁ 0.15 ꢁ 0.09
1.84–27.29
Reflections collected
Data/restraints/parameters
35 525
35 525/63/452
0.824
0.0976, 0.2501
0.2084, 0.2912
Goodness-of-fit on F2
R1a, wR2 [I > 2
r
(I)]
b
R1a, wR2 (all data)
b
a
R1 = [
wR2 ¼ f½
R
(||Fo| ꢀ |Fc||)/
R|Fo|].
2
1=2
b
R
ðwðF2o ꢀ F2c Þ Þ=
R
ðwF4oÞꢂ g.
3.3. Crystal structure of 1
Table 2
Selected bond distances (Å) and angles (°) of 1.
Crystals for X-ray diffraction were obtained from a saturated
chloroform solution. Solutions of alkyl substituted titanyl phthalo-
cyanines often slowly decompose when exposed to light and
oxygen, resulting in an orange solution and a white precipitate
[9]. Thus, the complexes have to be kept from light and air
Ti1–O1
Ti1–N1
1.619(8)
2.139(9)
Ti1–N3
2.112(1)
111.0(5)
138.4(4)
112.3(5)
82.7(3)
N1–Ti–O1
N1–Ti1–N10
N3–Ti1–O1
N1–Ti1–N3
N3–Ti1–N30
during crystallization. 1 crystallizes in the triclinic space group
ꢀ
P1 (a = 12.4678(15) Å, b = 12.4707(16) Å, c = 12.9692(18) Å,
a =
112.400(10)°, b = 109.897(10)°,
c = 99.122(10)°) with one molecule
138.3(3)
in the unit cell. Crystal data and refinement parameters for 1 are
given in Table 1. Fig. 5 shows the molecular structure of the mole-
cule possessing a crystallographic inversion centre. The titanyl
moiety is disordered within the ligand pocket with an equal occu-
pancy of both positions. It creates a dome over the isoindoline N
of the macrocyclic core and the ethynyl linkers. A similar batho-
chromic shift is observed for naphthalocyanines compared to anal-
ogous phthalocyanines [38]. The extension of the aromatic system
Fig. 6. Molecular packing of 1, view along the Pc layers. Both orientations of the disordered Ti@O moiety are displayed. H atoms and three disordered molecules of chloroform
per 1 are omitted for clarity.

E. Seikel et al. / Inorganica Chimica Acta 374 (2011) 119–126
125
pounds have been characterized by NMR and UV–Vis spectroscopy
and they show enhanced thermal stability compared to n-alkyl
substituted Pc’s. Therefore the benefits of solubility and thermal
robustness are combined in compounds 1, 2b and 3b. The molecu-
lar structure of 1 reveals that the titanyl group creates a dome over
the macrocycle. As a consequence two sets of endo and exo methyl
groups are observed in 1H and 13C NMR spectra. Face-to-face dimer
formation is hindered by this bulky ligand. To the best of our
knowledge, this is the first crystal structure reported for a soluble
non-aggregated titanyl phthalocyanine. Our next goals are investi-
gations of collective optophysical properties and of the reactivity of
these new titanyl phthalocyanines. Special focus will lie on physi-
cal vapour deposition experiments and the physical investigation
of ordered mono- and multilayers of 1.
Appendix A. Supplementary material
Fig. 7. Molecular packing of 1, view along the Ti@O bond. Ligand periphery, H
atoms and molecules of chloroform are omitted for clarity.
Selected NMR and UV–Vis spectra are given in the supporting
information. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.ica.2011.01.099.
atoms. The distance between the titanium atom and the plane de-
fined by N1, N10, N3 and N30 is 0.748(3) Å. The macrocycle slightly
deviates from planarity, adapting a ‘saddle’ conformation [19]. In
[PcTiO], a ‘saucer’ conformation is present [15]. The difference in
the chemical environment of the endo and exo methyl groups is
represented by the different distances O1–C18 (8.67(1) Å) and
O1–C17 (9.03(0) Å). The bond distances Ti1–O1 (1.619(8) Å), Ti1–
N1 (2.139(9) Å) and Ti1–N3 (2.112(1) Å) as well as the angles
N1–Ti1–O1 (111.0(5)°) and N3–Ti1–O1 (112.3(5)°) are comparable
to those reported for the unsubstituted complex [PcTiO] [15]. Se-
lected bond distances and angles are summarized in Table 2.
The lattice structure of 1 is shown in Figs. 6 and 7. Three disor-
dered molecules of chloroform are located between the macrocycle
layers and are omitted for clarity. The orientation of the titanyl
moiety is disordered due to the steric bulk induced by the periph-
eral methyl groups, since no disorder occurs in unsubstituted
[PcTiO]. The macrocycles are oriented essentially coplanar in a
slipped-stacked manner [19]. The distances between the titanium
atoms of two neighbouring macrocyles are 12.471(4) Å and
12.468(4) Å, respectively. This distance is significantly longer than
in unsubstituted [PcTiO] (daverage = 6.701 and 9.720 Å for the two
polymorphs) [15]. The distances between the ligand layers (plane
through N1, N10, N3 and N30) are 9.800 and 9.652 Å and lie be-
tween the values for the two polymorphs reported by Hiller et al.
(daverage = 4.879 and 12.281 Å, respectively). The aromatic systems
of neighbouring macrocycles overlap partially (Fig. 7), but the
overlapping area is much smaller than in the crystal phases 1
and 2 of [PcTiO] [13]. This should be a crucial factor regarding
the semiconducting and photophysical properties of 1. It is known
from fluorescence spectroscopy that the excited state lifetime of
phthalocyanines decreases with an increase of aggregation be-
tween the molecules, as non-radiative excited state quenching oc-
curs [39–43]. This has hampered the application of Pc’s in dye
sensitized solar cells [39,40]. The structure of 1 shows that by
introduction of the annellated cyclohexene moiety the aggregation
in solid state could be minimized, and hence less intermolecular
fluorescence quenching can be expected.
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