Axial functionalization of sterically hindered titanium phthalocyanines

Article abstract of DOI:10.1021/ic202749v

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc)have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc^#TiCl2] (5)has been prepared by re

Full text of DOI:10.1021/ic202749v

Article
pubs.acs.org/IC
Axial Functionalization of Sterically Hindered Titanium
Phthalocyanines
Elisabeth Seikel, Benjamin Oelkers, and Jorg Sundermeyer*
̈
Fachbereich Chemie, Philipps-Universitat Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany
̈
S
* Supporting Information
ABSTRACT: Several axially functionalized, weakly aggregating titanium
phthalocyanines (Pc) have been synthesized and characterized. Soluble
titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyra-
zine [Pc#TiCl2] (5) has been prepared by reductive cyclotetramerization
of the respective dinitrile precursor in the presence of TiCl4. 5 and the
analogous oxido compound [Pc#TiO] (1) are versatile starting materials
for the formation of other axially functionalized titanium phthalocyanines
such as organoimido (6, 7), alkoxido and aryloxido (8, 9), peroxido (10),
sulfido (12), disulfido (11), selenido (14) or diselenido (13) species.
Furthermore the deprotonated ligand salts [Pc#M2] (M = Li (2), Na (3),
K (4) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene
polymerization. The crystal structures of 5 and the free ligand Pc#H2 are reported. 5 crystallizes from dichloromethane in the
cubic space group Im3. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc#H crystallizes in the trigonal space
̅
2
group R3.
̅
metal template used in the reductive cyclotetramerization.
Typically, this method affords titanyl phthalocyanines
[PcRTiO], and relatively few synthetic protocols yielding
titanium chlorido or dichlorido phthalocyanines have been
described in the literature.28,29 The exchange of an axial ligand
in the macrocyclic complex was mostly described for soluble
titanyl phthalocyanines. Next to the parent titanyl phthalocya-
nines, other axially substituted PcTis reported in the literature
are chlorido,30 oxalato, catecholato, and dithiocatecholato
derivatives.23,31,32 Catecholates have been used as axial ligands
to build phthalocyanine dimers and oligomers which are useful
for the recognition of chiral catechols.33−36 [PcTi(S2)] has
been synthesized and characterized by X-ray diffraction,37 and
sulfido and selenido complexes have been mentioned in a
patent, but not characterized.38 Recently, we have reported the
synthesis of titanium imido and ureato phthalocyanines starting
from the titanyl complexes or the deprotonated Pc ligand.37,39
The large variety of transformations feasible for porphyrins and
other macrocyclic complexes has not yet been fully transferred
to phthalocyanine chemistry. To expand our studies on soluble,
isomerically pure, alkyl substituted phthalocyanines, we
synthesized [Pc#TiO] 1 (Figure 1).40 In this work we describe
the synthesis of titanium Pc# derivatives bearing different
substituents in the axial positions.
INTRODUCTION
■
Phthalocyanine complexes [PcM] are an important class of
red/near-IR (Q-band) absorbing chromophores used as dyes
and semiconductors in optoelectronic materials.1−4 They find
application in devices such as organic field effect transistors
(OFETs)5 or as sensitizers for wide band gap oxide
semiconductors in organic heterojunction dye sensitized solar
cells (DSSCs).6 The solar conversion efficiencies of [PcM]
appear to be dependent on the metal,7 on the Pc polarizability,8
on the degree of unfavorable Pc aggregation, and on the lack of
directionality of the excited state.9 To reduce the aggregation
and enhance the solubility, randomly tetra-tert-butyl substituted
Pcs, [PctBuZn] or [PctBuTiO], are commonly employed. This
material is a mixture of regio isomers, which leads to poorly
resolved NMR spectra and prevents the molecules from
forming ordered or even single crystalline phases. In the case
of the parent, ring-unsubstituted metal phthalocyanines, the
reactivity patterns have been much less studied than those of
related porphyrins and other N4-macrocycle supported
complexes because of the insolubility of [PcM]. The group of
Woo, for example, has developed a variety of synthetic
strategies leading to titanium porphyrins bearing imido,
amido, alkoxo,10 hydrazido,11 and chalcogenido12 function-
alities as well as subvalent Ti(II) porphyrins.13−15 Titanium
peroxido porphyrins have also been described.16 Similarly, the
group of Mountford synthesized a variety of axially substituted
titanium complexes coordinated by tetraaza macrocyclic
ligands.17−21
EXPERIMENTAL SECTION
■
General Procedures. 6,7-Dicyano-1,1,4,4-tetramethyltetraline was
prepared according to literature procedures41,42 and purified by
Until recently, the chemistry of titanium phthalocyanines was
mainly focused on variations of the equatorial Pc ligand
system.22−27 The axial functionality can be determined by the
Received: December 22, 2011
Published: February 8, 2012
© 2012 American Chemical Society
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Article
[Pc#Na2] (3). Fifty milligrams of Pc#H2 (0.05 mmol, 1.0 equiv) and
48 mg of NaHMDS (0.26 mmol, 5.0 equiv) in 5 mL of THF were
heated to 60 °C overnight. Volatiles were removed under reduced
pressure, and the resulting bluegreen solid was washed with toluene
and pentane. 1H NMR (300 MHz, CDCl3 + 1 drop THF-d8): δ = 9.11
(s, 8H), 1.98 (s, 16H), 1.74 (s, 48H) ppm. UV−vis (CH2Cl2): λ = 683
(s), 619 (sh), 340 (m) nm. MS (MALDI-TOF(+)): m/z = 1000.2
[M]+.
[Pc#K2] (4). Seventy milligrams of Pc#H2 (0.07 mmol, 1.0 equiv)
were suspended in 8 mL of THF and cooled to 0 °C. A solution of 24
mg of KBn (0.18 mmol, 2.5 equiv) in 1 mL of THF was added
dropwise. The mixture was stirred for 3 h and warmed to room
temperature. After filtration over Celite the volatiles were removed
Figure 1. [Pc#TiO] 1 and the free ligand Pc#H2.
1
under reduced pressure. H NMR (300 MHz, CDCl3): δ = 9.31 (s,
8H), 2.02 (s, 16H), 1.77 (s, 48H) ppm. UV−vis (CH2Cl2): λ = 681
(s), 616 (sh), 345 (m), 252 (s) nm. MS (MALDI-TOF(+)): m/z =
1033.2 [M]+. According to NMR spectroscopy, a mixture of 3 and
Pc#H2 was obtained.
column chromatography (silica gel, CH2Cl2) prior to use. Chlor-
onaphthalene was obtained from Acros as a mixture of 1-
chloronaphthalene (90%) and 2-chloronaphthalene (10%). Solvents
were dried according to standard methods and stored under inert gas
over molecular sieves. TiCl4 and Ti(OnBu)4 were obtained from Acros
and stored under inert gas. Preparations were carried out under dry
argon atmosphere using standard Schlenk or glovebox techniques.
The electronic spectra were recorded on an Avantes AvaSpec-2048
spectrometer in a glovebox. IR spectra were recorded on a Bruker
Alpha FT-IR spectrometer with an ATR measurement setup (diamond
cell) in a glovebox using neat samples. APCI mass spectra were taken
on a Finnigan LTQ-FT spectrometer using dichloromethane as
solvent. MALDI−TOF mass spectra were taken on a Bruker Biflex III
using pyrene as matrix. Elemental analyses of C, H, N, and S were
carried out using an Elementar vario MICRO cube. 1H and 13C NMR
spectra were recorded on a Bruker Avance 300 or Bruker DRX 400.
X-ray diffraction (XRD) analyses were performed on a Stoe IPDS 2
area detector system using Mo Kα radiation (λ = 71.073 pm) at 100 K.
Stoe IPDS software43 was used for integration and data reduction;
structure solution and refinement was done with the WinGX
program44 suite using SIR200445 and SHELX-97.46 Molecular graphics
were produced with Diamond 3.2 g.47
cis-[Pc#TiCl2] (5). A 1.00 g portion of 6,7-dicyano-1,1,4,4-
tetramethyl-tetraline (4.20 mmol, 4.4 equiv) and 179 mg of TiCl4
(0.95 mmol, 1.0 equiv) in 6 mL of 1-chloronaphthalene were placed in
an oil bath preheated to 160 °C and stirred overnight. After 1 h an
intensely geen mixture was obtained. After cooling the product was
precipitated by addition of 40 mL of hexane. The violet microcrystal-
line solid was collected by centrifugation, extracted with 3 × 40 mL of
THF, washed with pentane, and dried under vacuum. Suitable crystals
for X-ray diffraction were obtained from a saturated CH2Cl2 solution
1
at 4 °C. Yield: 512 mg of violet microcrystals, 0.48 mmol, 50%. H
NMR (300 MHz, CDCl3): δ = 9.67 (s, 8H), 2.08 (s, 16H), 1.88 (s,
24H), 1.81 (s, 24H) ppm. IR: υ = 2956 (s), 2922 (s), 2859 (s), 1615
(w), 1492 (m), 1455 (m), 1431 (m), 1385 (w), 1305 (s), 1257 (m),
1187 (w), 1087 (s), 1066 (s), 974 (m), 868 (m), 789 (s), 706 (m)
cm−1. UV−vis (CH2Cl2): λ = 713 (s), 640 (sh), 348 (m), 235 (s) nm.
MS (APCI-HR(+)): m/z = 1031.5543 [M-2Cl+OMe]+, C65H75N8OTi
requires 1031.5541 (methanolysis occurs upon ionization in the
presence of methanol).
[Pc#Ti(NtBu)] (6). Seven milligrams of tert-butylamine (0.10 mmol,
2.1 equiv) in 5 mL of toluene were deprotonated with 0.06 mL of a 1.6
M n-BuLi solution in hexane (0.10 mmol, 2.1 equiv). This mixture was
added dropwise to a suspension of 50 mg of 5 (0.05 mmol, 1.0 equiv)
in 5 mL of toluene. It was stirred overnight at room temperature, and a
green solution and a white precipitate were obtained. After filtration
over Celite the volatiles were removed under reduced pressure. The
resulting green solid was dried under vacuum. Yield: 10 mg green
In two cases, heavily disordered dichloromethane molecules could
not be modeled adequately. The SQUEEZE routine of the PLATON
program package48 was used in these cases to remove the
corresponding delocalized electron density from the data sets.
Pc#H2. This compound was prepared by a modification of the
method described by Mikhalenko et al.:42 176 mg of lithium (25
mmol, 5.0 equiv) were dissolved in 10 mL of 1-octanol. To complete
the dissolution the suspension was stirred at 60 °C for 30 min. After
cooling 1.2 g of 6,7-dicyano-1,1,4,4-tetramethyltetraline (5 mmol, 1.0
equiv) were added, and the mixture was stirred at 130 °C for 24 h. The
dark blue mixture was cooled, and the product was precipitated by
adding 60 mL of methanol and 1 mL of 85% H3PO4. The turquoise
solid was filtered off and extracted with 3 × 60 mL of hot methanol,
washed with diethylether, and dried under vacuum. Suitable crystals
for X-ray diffraction were obtained from a saturated, degassed toluene
solution layered with pentane in the dark. Yield: 733 mg, 0.77 mmol,
1
powder, 0.01 mmol, 21%. H NMR (300 MHz, CDCl3): δ = 9.55 (s,
8H), 2.07 (s, 16H), 1.88 (s, 24H), 1.78 (s, 24H), −1.36 (s, 9H) ppm.
13C NMR (75 MHz, CDCl3): δ = 151.2, 148.3, 120.8, 35.1, 34.3, 32.0,
31.8 ppm (not all quaternary carbon atoms were detected). IR: υ =
2957 (m), 2920 (m), 2858 (m), 1614 (w), 1454 (m), 1308 (s), 1011
(s), 765 (m), 684 (m), 454 (w) cm−1. UV−vis (CH2Cl2): λ = 710 (s),
645 (sh), 344 (m), 240 (s) nm. MS (MALDI-TOF(+)): m/z = 1073.5
[M]+, 1058.6 [M-Me]+, 1018.5 [M-tBu]+, 1002.4 [M-NtBu]+. MS
(APCI-HR(+)): m/z = 1072.6183 [M+H]+, C68H82N9Ti requires
1072.6167.
1
73%. H NMR (300 MHz, CDCl3): δ = 9.48 (s, 8H), 2.06 (s, 16H),
1.81 (s, 48H), −0.03 (s, 2H, N-H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 148.4, 134.7, 121.3, 36.1, 35.6, 33.0 (not all quaternary carbon
atoms were detected). IR: υ = 2956 (s), 2920 (s), 2853 (s), 1619 (m),
1575 (m), 1455 (s), 1360 (m), 1303 (m), 1258 (m), 1184 (w), 1072
(m), 1006 (s), 946 (m), 845 (m), 753 (s) cm−1. UV−vis (CH2Cl2): λ
= 710 (s), 676 (s), 650 (sh), 342 (s) nm. MS (APCI-HR(+)): m/z =
955.6115 [M+H]+, C64H75N8 requires 955.6109.
[Pc#Ti(NMes)] (7). Sixty-five milligrams of mesitylamine (0.48
mmol, 2.1 equiv) in a mixture of 5 mL of toluene and 0.5 mL of THF
were deprotonated with 0.3 mL of a 1.6 M n-BuLi solution in hexane
(0.48 mmol, 2.1 equiv). The suspension was added dropwise to 250
mg of 5 (0.23 mmol, 1.0 equiv) in 20 mL of toluene. The mixture was
stirred overnight at room temperature yielding a green solution and a
white precipitate. The mixture was filtered over Celite, washed with
THF, and the filtrate was evaporated to dryness. The blue solid was
washed with acetonitrile and pentane and dried under vacuum. Yield:
198 mg blue solid, 0.18 mmol, 75%. 1H NMR (300 MHz, CDCl3): δ =
9.55 (s, 8H), 5.44 (s, 2H), 2.07 (s, 16H), 1.88 (s, 24H), 1.79 (s, 24H),
[Pc#Li2] (2). Fifty milligrams of Pc#H2 (0.05 mmol, 1.0 equiv) and
40 mg of LiHMDS (0.24 mmol, 4.8 equiv) were stirred overnight in 3
mL of tetrahydrofuran (THF) at 60 °C. A blue solid was separated,
1
washed with pentane, and dried under vacuum. H NMR (300 MHz,
1
CDCl3): δ = 9.29 (s, 8H), 2.03 (s, 16H), 1.86 (s, 48H) ppm. UV−vis
(CH2Cl2): λ = 680 (s), 611 (sh), 343 (m) nm. MS (MALDI-
TOF(+)): m/z = 967.8 [M]+, 961.7 [Pc#HLi]. According to NMR
spectroscopy and mass spectrometry, a mixture of 2, Pc#HLi and
Pc#H2 was obtained.
1.45, (s, 3H), −0.18 (s, 6H) ppm. H NMR (300 MHz, C6D6): δ =
10.03 (s, 8H), 5.30 (s, 2H), 1.78 (s, 16H), 1.56 (s, 24H), 1.52 (s,
24H), 1.28, (s, 3H), 0.11 (s, 6H) ppm. 13C NMR (75 MHz, C6D6): δ
= 152.4, 149.1, 136.5, 132.3, 129.3, 126.6, 122.3, 35.9, 35.7, 32.7, 32.6,
20.2, 16.9 ppm (not all quaternary carbon atoms were detected). IR: υ
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= 2956 (m), 2921 (m), 2857 (m), 1467 (m), 1306 (s), 1187 (m),
1068 (s), 850 (m), 707 (m), 543 (w) cm−1. UV−vis (CH2Cl2): λ =
710 (s), 640 (sh), 343 (s), 238 (s) nm. MS (APCI-HR(+)): m/z =
1134.6300 [M+H]+, C73H84N9Ti requires 1134.6324.
UV−vis spectroscopy. Volatiles were removed, and the green solid was
extracted with 3 × 10 mL of hexane, 2 × 10 mL of acetonitrile, and
1
dried under vacuum. Yield: 8 mg green solid, 0.01 mmol, 41%. H
NMR (300 MHz, CDCl3): δ = 9.66 (s, 8H), 2.07 (s, 16H), 1.88 (s,
24H), 1.81 (s, 24H) ppm. 13C NMR (75 MHz, CDCl3): δ = 151.9,
149.6, 134.7, 122.0, 36.2, 35.4, 33.0, 32.9 ppm. IR: υ = 2959 (m), 2923
(m), 2861 (m), 1617 (w), 1457 (m), 1307 (s), 1188 (m), 1068 (s),
1022 (m), 870 (m), 753 (w), 664 (m), 572 (w), 450 (w) cm−1. UV−
vis (CH2Cl2): λ = 726 (s), 651 (sh), 360 (s), 300 (s), 256 (s) nm. MS
(APCI-HR(+)): m/z = 1033.5133 [M+H]+, C64H73N8STi requires
1033.5160.
trans-[Pc#Ti(OtBu)2] (8). Fifty milligrams of 5 (0.05 mmol, 1.0
equiv) and 11 mg of KOtBu (0.10 mmol, 2.1 equiv) were stirred at
room temperature in a mixture of 3 mL of toluene and 1 mL of THF
for 3 h. The mixture was filtered over Celite, washed with THF, and
the filtrate was evaporated to dryness. The green solid was washed
with hexane and dried under vacuum. Yield: 9 mg green powder, 0.01
1
mmol, 17%. H NMR (300 MHz, C6D6): δ = 10.01 (s, 8H), 1.75 (s,
16H), 1.50 (s, 48H), −1.91 (s, 18H) ppm. IR: υ = 2958 (s), 2922 (s),
2859 (s), 1616 (w), 1471 (m), 1319 (s), 1305 (s), 1216 (w), 1183
(m), 1063 (s), 999 (s), 871 (m), 859 (s), 789 (m), 707 (m), 567 (m)
cm−1. UV−vis (CH2Cl2): λ = 712 (s), 639 (sh), 340 (s) nm. MS
(APCI-HR(+)): m/z = 1147.6754 [M+H]+, C72H90N8O2Ti requires:
1147.6748.
[Pc#Ti(Se2)] (13). Fifty milligrams of 5 (0.05 mmol, 1.0 equiv), 31
mg of C8K (0.23 mmol, 5.0 equiv), and 29 mg of Se8 (0.05 mmol, 1.0
equiv) in 20 mL of THF were stirred overnight at room temperature.
The resulting green solution was filtered, evaporated to dryness and
taken up in CH2Cl2. The mixture was filtered over silica to remove
residual Se8, evaporated, washed with hexane, and dried under vacuum.
Yield: 18 mg green solid, 0.02 mmol, 33%. 1H NMR (300 MHz,
CDCl3): δ = 9.52 (s, 8H), 2.06 (s, 16H), 1.85 (s, 24H), 1.78 (s, 24H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 152.1, 149.4, 134.3, 121.6,
36.1, 35.3, 33.0. 32.8 ppm. IR: υ = 2952 (m), 2923 (m), 2859 (m),
1454 (m), 1305 (s), 1186 (w), 1067 (s), 1021 (m), 897 (m), 865 (m),
751 (w), 706 (w), 543 (w) cm−1. UV−vis (CH2Cl2): λ = 716 (s), 648
(sh), 354 (s), 290 (s), 242 (s) nm. MS (APCI-HR(+)): m/z =
1161.3771 [M+H]+, C64H73N8Se2Ti requires 1161.3781.
cis-[Pc#Ti(OMes)2] (9). Fifty milligrams of 5 (0.05 mmol, 1.0
equiv) and 11 mg of LiOMes (0.10 mmol, 2.1 equiv) were suspended
in a mixture of 3 mL of toluene and 1 mL of THF and stirred at 50 °C
overnight. The mixture was filtered over Celite, washed with THF, and
the volatiles were removed under reduced pressure. The blue solid was
washed with hexane and dried under vacuum. Yield: 20 mg green
1
powder, 0.02 mmol, 34%. H NMR (300 MHz, C6D6): δ = 9.92 (s,
8H), 5.46 (s, 4H), 1.76 (s, 16H), 1.56 (s, 24H), 1.49 (s, 24H), 1.37 (s,
6H), 0.38 (s, 12H) ppm. 13C NMR (75 MHz, C6D6): δ = 154.2, 149.2,
135.3, 130.8, 129.5, 129.1, 123.2, 122.9, 122.0, 36.0, 35.6, 32.8, 32.7,
20.5, 15.8 ppm. IR: υ = 2956 (s), 2921 (s), 2858 (s), 1615 (w), 1456
(s), 1432 (m), 1363 (w), 1305 (s), 1239 (m), 1187 (m), 1066 (s),
1022 (s), 986 (m), 896 (m), 859 (s), 759 (m), 664 (m), 546 (m)
cm−1. UV−vis (CH2Cl2): λ = 717 (s), 643 (sh), 337 (s) nm. MS
(APCI-HR(+)): m/z = 1031.5543 [M-2OMes+OMe]+, C65H75N8OTi
requires: 1031.5541 (methanolysis occurs upon ionization in the
presence of methanol).
[Pc#TiSe] (14). Fifty milligrams of 13 (0.04 mmol, 1.0 equiv) and
20 mg of PPh3 (0.08 mmol, 1.8 equiv) in 15 mL of CH2Cl2 were
stirred for 1 h at room temperature. The immediate formation of
[Pc#TiSe] and Ph3PSe (δ(31P) = 35.2 ppm) was monitored via 1H, 31
P
NMR, and UV−vis spectroscopy. Volatiles were removed, and the
green solid was extracted with 2 × 20 mL of acetonitrile, 3 × 20 mL of
hexane, and dried under vacuum. Yield: 39 mg green solid, 0.03 mmol,
1
84%. H NMR (300 MHz, CDCl3): δ = 9.67 (s, 8H), 2.09 (s, 16H),
1.91 (s, 24H), 1.84 (s, 24H) ppm. 13C NMR (75 MHz, CDCl3) δ =
152.0, 149.7, 134.7, 122.1, 36.2, 35.4, 33.0, 32.9 ppm. IR: υ = 2957
(m), 2922 (m), 2858 (m), 1616 (w), 1455 (w), 1306 (m), 1258 (s),
1187 (w), 1063 (s), 1015 (2), 897 (w), 868 (m), 792 (s), 706 (w), 543
(w) cm−1. UV−vis (CH2Cl2): λ = 732 (s), 658 (sh), 371 (s), 334 (s),
256 (s) nm. MS (APCI-HR(+)): m/z = 1081.4611 [M+H]+,
C64H73N8SeTi requires 1081.4597.
[Pc#Ti(O2)] (10). During the preparation and workup light was kept
from the product by wrapping all flasks in aluminum foil. Fifty
milligrams of [Pc#TiO] 140 (0.05 mmol, 1.0 equiv) in 10 mL of
dichloromethane and 9 μL of H2O2 (30% in water, 0.07 mmol, 1.5
equiv) were vigorously stirred for 2 h. The mixture was extracted with
water until no more peroxide could be detected (KIaq). The organic
layer was dried over MgSO4, filtered, and the solvent was evaporated.
[Pc#TiO→(Al(iBu)3)] (15). Method a. Sixty-five milligrams of
1 (0.06 mmol, 1.0 equiv) were dissolved in 10 mL of toluene.
0.38 mL (0.12 mmol, 2.0 equiv) of a 10% solution of
(iBu)2AlOAl(iBu)2 in toluene were added at room temperature.
After 2 h the volatiles were removed, and the blue solid was
washed with hexane.
Method b. Fifty milligrams of 1 (0.05 mmol, 1.0 equiv) were
dissolved in 10 mL of toluene. 0.07 mL (0.05 mmol, 1.0 equiv) of a
0.15 g/mL solution of Al(iBu)3 in toluene were added at room
temperature. After 2 h the volatiles were removed, and the blue solid
was washed with hexane.
1
Yield: 12 mg green powder, 0.01 mmol, 24%. H NMR (300 MHz,
CDCl3): δ = 9.58 (s, 8H), 2.07 (s, 16H), 1.86 (s, 24H), 1.80 (s, 24H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 152.2, 149.6, 134.3, 122.3,
35.3, 34.4, 31.8, 31.7 ppm. IR: υ = 2959 (m), 2922 (m), 2860 (m),
1616 (w), 1499 (m), 1456 (m), 1433 (w), 1386 (w), 1306 (s), 1260
(m), 1188 (m), 1090 (s), 1071 (s), 1018 (s), 895 (m, νO−O), 867 (m),
792 (s), 707 (m), 642 (w, νTi−O sym), 609 (m, νTi−O asym) cm−1. UV−vis
(CH2Cl2): λ = 714 (s), 644 (sh), 348 (m), 281 (s) nm. MS (APCI-HR
(+)): m/z = 1017.5376 [M-O+H]+, C64H73N8OTi requires 1017.5387.
MS (MALDI-TOF(+)): m/z = 1035.1 [M]+.
[Pc#Ti(S2)] (11). Fifty milligrams of 5 (0.05 mmol, 1.0 equiv), 31
mg of C8K (0.23 mmol, 5.0 equiv), and 12 mg of S8 (0.05 mmol, 1.0
equiv) in 20 mL of THF were stirred overnight at room temperature.
The resulting green solution was filtered over Celite, evaporated to
dryness, and washed with hexane. Yield: 20 mg green solid, 0.02 mmol,
40%. To remove traces of elemental sulfur and obtain analytically pure
11, the product was taken up in dichloromethane and filtered over a
1H NMR (300 MHz, C6D6): δ = 10.06 (s, 8H), 1.75 (s, 16H), 1.53
(s, 24H), 1.50 (s, 24H), 0.50 (m, 3H), 0.16 (d, 3JHH = 6.41 Hz, 18H),
−1.59 (d, 3JHH = 7.04 Hz, 6H) ppm. 13C NMR (75 MHz, C6D6): δ =
152.8, 150.9, 135.0, 123.1, 36.2, 35.5, 32.6, 32.6 (Pc#), 28.0, 26.4, 23.8
(AliBu3) ppm. IR: υ = 2928 (m), 2856 (m), 1618 (w), 1456 (m), 1434
(m), 1306 (s), 1187 (m), 1088 (m), 1059 (s), 985 (w), 932 (m), 867
(m), 750 (m), 663 (m), 496 (w) cm−1. UV−vis (toluene): λ = 733 (s),
660 (sh), 359 (s), 285 (s) nm.
1
short silica column. H NMR (300 MHz, CDCl3): δ = 9.54 (s, 8H),
2.06 (s, 16H), 1.85 (s, 24H), 1.79 (s, 24H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 152.5, 149.6, 134.2, 121.8, 36.1, 35.3, 33.0, 32.8 ppm. IR:
υ = 2950 (m), 2926 (m), 2860 (m), 1616 (w), 1454 (m), 1307 (s),
1186 (m), 1067 (s), 1021 (m), 987 (m), 897 (m), 755 (m), 664 (m),
553 (m) cm−1. UV−vis (CH2Cl2): λ = 717 (s), 648 (sh), 343 (s), 295
(s) nm. MS (APCI-HR(+)): m/z = 1065.4855 [M+H]+,
C64H73N8S2Ti requires 1065.4880.
Polymerization of Ethene. Ten μmol of the precatalyst (1, 5 or
Eurecen 5031) were activated with 1000 equiv of MAO in 5 mL of
chlorobenzene. Ethene was bubbled through 45 mL of chlorobenzene
at 50 °C for 15 min. The solution of the activated precatalyst was
added quickly, and the mixture was stirred under continuing ethene
flow at 50 °C for 1 h. The mixture was quenched with HCl (1% in
MeOH) and poured into 200 mL of methanol. The precipitated
polymer was filtered, washed with methanol, dichloromethane, and
ether and dried under vacuum at 60 °C.
[Pc#TiS] (12). Twenty milligrams of 11 (0.02 mmol, 1.0 equiv) and
20 mg of PPh3 (0.08 mmol, 4.0 equiv) were dissolved in 1 mL of
CDCl3 at room temperature. The immediate formation of [Pc#TiS]
and Ph3PS (δ(31P) = 42.5 ppm) was monitored via 1H, 31P NMR and
Reactivity of 7 toward p-Cl-benzaldehyde. An NMR tube was
charged with 10 mg of 7 (8.8 μmol, 1.0 equiv), 1.2 mg of p-Cl-
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benzaldehyde (8.8 μmol, 1.0 equiv), and 0.6 mL of C6D6. The reaction
progress was monitored via 1H NMR spectroscopy. After 24 h at room
temperature, a 7:1 ratio of 70%:30% was determined by integration of
the aromatic Pc# protons. Unambiguous assignment of resonances of
p-chlorobenzylidene mesitylamine was not possible because of the
presence of different species. MS (ESI-HRMS(+)): m/z = 258.1050
[p-chlorobenzylidene mesitylamine+H]+. C16H17ClN requires
258.1044.
Scheme 2. Preparation of 5
Reactivity of 7 toward Nitrosobenzene. An NMR tube was
charged with 20 mg of 7 (17.6 μmol, 1.0 equiv), 1.9 mg of
nitrosobenzene (17.6 μmol, 1.0 equiv), and 0.6 mL of C6D6. The
1
reaction progress was monitored via H NMR spectroscopy. After 5
min at room temperature, all starting material was consumed, and 1
and mesityl phenyl diazene were formed. 1H NMR (300 MHz, C6D6):
δ = 7.58 (m, 1H), 6.96−6.79 (m, 4H), 6.48 (s, 2H), 2.20 (s, 3H), 1.86
(s, 6H) ppm. MS (ESI-HR(+)): m/z = 225.1388 [mesityl phenyl
diazene+H]+. C15H17N2 requires 225.1386.
Reactivity of 7 toward Styrene Oxide. An NMR tube was
charged with 17 mg of 7 (15.8 μmol, 1.0 equiv), 1.7 μL of styrene
oxide (15.8 μmol, 1.0 equiv), and 0.6 mL of C6D6. No conversion was
observed after 24 h.
Reactivity of 7 toward Triphenylphosphine Oxide. An NMR
tube was charged with 20 mg of 7 (17.6 μmol, 1.0 equiv), 5 mg of
Ph3PO (17.6 μmol, 1.0 equiv), and 0.6 mL of C6D6. No conversion
was observed after 24 h.
and [Pc#Ti(NMes)] 7 under mild conditions. Similarly, salt
elimination reactions with lithium or potassium alkoxides
produces the bisalkoxo complexes trans-[Pc#Ti(OtBu)2] 8 and
cis-[Pc#Ti(OMes)2] 9 (Scheme 3). The cis and trans isomers
Scheme 3. Preparation of Axially Functionalized Titanium
a
Phthalocyanines 6−9 via Salt Elimination
RESULTS AND DISCUSSION
■
Preparation. Organoimido, Alkoido, and Aryloxido
Complexes. Axially functionalized titanium phthalocyanines
could be prepared by reaction of PcK2 with titanium imido
precursors or by reaction of [PcTiO] with aryl isocyanates.39
However, the reactions of different alkali metal salts 2−4 of the
soluble ligand Pc#H2 with titanium imido precursors were
unselective (Scheme 1). Pc#Na2 did not react with [Ti(NR)-
a
The ellipse represents the macrocyclic ligand.
1
can be distinguished by H NMR spectroscopy (see Spectros-
copy section). According to NMR spectroscopy 8 decomposes
rapidly in solution to form oxido complex 1, which is attributed
to the elimination of isobutene forming unstable [Pc#Ti(OH)-
(OtBu)] or [Pc#Ti(OH)2], which readily eliminate tBuOH or
water. Both alkoxo compounds are extremely labile toward
hydrolysis. Attempts to synthesize bisalkyl or bisamido
complexes by the reaction of [Pc#TiCl2] with lithium alkyls
or secondary lithium amides were unsuccessful because of the
side reaction of ortho-directed deprotonation of the phthalo-
cyanine backbone.50,51
Oxido, Sulfido, and Selenido Derivatives. To study the
higher homologues of the parent titanium oxo and peroxo Pc#,
we were particularly interested in the synthesis of mono- and
dichalcogenido compounds [Pc#TiE] (E = O (1), S (12), Se
(14)) and [Pc#Ti(E2)] (E = O (10), S (11), Se (13)).
Peroxido compound [Pc#Ti(O2)] 10 could be successfully
synthesized by treatment of a dichloromethane solution of
[Pc#TiO] with H2O2 in the dark (Scheme 4). The identity of
Scheme 1. Preparation of Titanium Imido Compounds
Starting from Pc#H2
Cl2Pyn] (n = 2, 3). For Pc#Li2 and Pc#K2, the resulting imido
compounds [Pc#Ti(NR)] were contaminated with the free
ligand Pc#H2 which resulted from incomplete deprotonation.
These mixtures could not be separated by extraction or
recrystallization because of their similar solubilities.
For the soluble [Pc#TiO], metathesis with aryl isocyanates at
high temperatures gave mixtures of [Pc#TiO], imido com-
pounds [Pc#Ti(NAr)], and ureato compounds [Pc#Ti(ArN-
(CO)N′Ar)]. Because of their hydrolytic sensitivity these
mixtures could not be separated by column chromatography.49
Thus, the established strategies for the preparation of axially
functionalized titanium phthalocyanines with the unsubstituted
macrocyclic ligand Pc could not be properly transferred to the
chemistry of soluble Pc# complexes.
Scheme 4. Preparation of [Pc#Ti(O2)] 10
Since, for example, imido functionalized Pc# compounds
were not accessible in pure form starting from 1, we developed
a different synthetic protocol starting from the dichlorido
species [Pc#TiCl2] 5.
5 could be obtained by reductive cyclotetramerization of 6,7-
dicyano-1,1,4,4-tetramethyltetraline in the presence of TiCl4 in
chloronaphthalene (Scheme 2). 5 is a versatile precursor for the
preparation of axially functionalized, soluble phthalocyanines.
The reaction with 2 equiv of primary lithium amides leads to
the respective alkyl or aryl imido complexes [Pc#Ti(NtBu)] 6
the product was confirmed by UV−vis, NMR, and IR
spectroscopy. The characteristic υTiO = 977 cm−1 disappears,
and three absorptions for the peroxo group are observed (υO−O
= 895 cm−1, υTi−O sym = 642 cm−1, and υTi−O asym = 609 cm−1).
The product readily decomposes when exposed to light, leading
to decomposition of the macrocyclic ligand. This is also the
case for related titanium peroxo porphyrins.16
In the case of the porphyrin analogues, subvalent Ti(II)
species could be oxidized by elemental sulfur or selenium,
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yielding the dichalcogenido compounds. Analogously, oxidation
by R3PE gave the monochalcogenido compounds.12 [Pc#TiCl2]
could not be reduced to a subvalent Ti(II) species by reaction
with LAH or LiHBEt3 like the corresponding porphyrins.12,15
These reactions were unselective. We attribute this to the
nucleophilic character of these reducing agents which can attack
the imine bridge between the isoindoline units. Thus, we had to
develop a different synthetic approach. The dichalcogenido
compounds 11 and 13 could be obtained by an in situ protocol
employing 5, C8K and S8 and Se8, respectively (Scheme 5). It
results from the symmetry lowering imposed by the axial
ligands.40 For dichlorido compound 5 and bisaryloxido
compounds 9, this suggests a cis arrangement of the functional
groups. In the case bisalkoxido compound 8 a single resonance
for the methyl groups is observed, indicating a D4h symmetric
trans arrangement of the bulky OtBu-groups. This is in
accordance with [PcTi(OSiPh3)2],37 were the bulky substitu-
ents are also arranged in a trans fashion. All resonances of axial
ligands are shifted upfield because of the strong ring current in
the macrocyclic ligand.31
UV−vis Spectra. UV−vis spectra of all substances were
measured in dry CH2Cl2 or toluene. The electronic spectrum of
the free ligand [Pc#H2] shows a split Q-band with maxima at
710 and 676 nm which is characteristic for D2h symmetric
phthalocyanines.54 The deprotonated species 2−4 show a
single Q-band at 680−683 nm which is in accordance with the
assumed D4h symmetry of the molecules. The electronic spectra
of the axially functionalized titanium phthalocyanines 1, 5−11,
and 13 all show the characteristic Q-band absorption maximum
between 710 and 717 nm. No significant changes are observed
upon exchange of the axial functionality. This is because the
absorption spectra are mainly determined by the macrocyclic
ligand system.23,31,32,39 Representative for all prepared com-
pounds, the spectra of [Pc#H2], [Pc#K2] and [Pc#TiCl2] are
displayed in Figure 2.
Scheme 5. Preparation of Dichalcogenido and Chalcogenido
Compounds 11−14
cannot be ruled out that under these conditions the reduction
of E8 to K2Ex is a parallel reaction to the reduction of the metal
phthalocyanine, but both possible pathways lead to the same
products. A selective synthesis of the monochalcogenido
species 12 and 14 was possible by reduction of the
dichalcogenido compounds 11 and 13 with an excess of
Ph3P. The reaction progress could be followed by 31P NMR or
UV−vis spectroscopy, and complete conversion was achieved
after 5 min.
Lewis Acid Adducts. A different class of axially substituted
titanium phthalocyanines are Lewis acid adducts of [Pc#TiO].
Similar experiments have been described by the group of
Hanack for rhenium nitrido Pcs and various group 3 Lewis
acids.52 In our case, a Lewis acid adduct can be readily obtained
by adding triisobutylaluminium or tetraisobutyldialumoxane to
toluene solutions of 1 (Scheme 6). The instantaneous
Scheme 6. Preparation of Lewis Acid Adduct 15
Figure 2. UV−vis spectra of Pc#H2, [Pc#K2], and [Pc#TiCl2] in
CH2Cl2.
We were particularly interested in the effect that the heavier
axial ligands S2− and Se2− have on the photophysical properties
of the complexes. The reactions of 11 and 13 with PPh3 were
therefore monitored via UV−vis spectroscopy. In fact,
pronounced changes in the electronic spectra are observed as
the Q-band maxima are shifted bathochromically from 717 nm
(11) to 726 nm (12) and from 716 (13) to 736 nm (14),
respectively. The reactions are complete after a few minutes
(for spectra see Supporting Information). This may be
attributed to the higher polarizability of the large, soft axial
ligand.
Upon addition of Al(iBu3) to a toluene solution of 1 the
formation of Lewis acid adduct 15 can be detected by UV−vis
spectroscopy within 30 s. The Q-band maximum is shifted to
731 nm and decreases in intensity. A similar behavior was
described for Lewis acid adducts of [R8PcReN].52 Addition of
traces of protic solvent (MeOH) results in the immediate
dissociation of the adduct, and the stating material is recovered
(for spectra see Supporting Information).
formation of the product can be monitored via NMR and
UV−vis spectroscopy. In both cases, the same product of the
constitution [Pc#TiO→Al(iBu)3] (15) is obtained. This is due
to ligand redistribution in the case of (iBu)2AlOAl(iBu)2
leading to the in situ formation of Al(iBu)3 and formally
“AlO(iBu)n”. A new set of Pc# resonances is observed in the 1H
NMR spectrum together with the upfield shifted resonances of
the axially coordinated Lewis acid. Also, the Q-band maximum
in the electronic spectra is shifted, and the characteristic νTiO
at 977 cm−1 is shifted to lower wavenumbers, which is in
accordance with a reduction of the Ti−O bond strength.
Spectroscopy. NMR Spectra. All proton NMR spectra
show the characteristic downfield shift for the phthalocyanine
protons (9.29−10.06 ppm).31,53 Since no other signals occur in
this region, the singlet observed for the eight Pc# ring protons is
a suitable NMR probe for the selectivity of a reaction. The free
ligand and its dialkali salts 2−4 show a single resonance for the
methyl groups, indicating the D2h and D4h symmetry of the
substances, respectively. The C4v symmetric titanium complexes
(1, 5−7, 9−15) show two signals for the methyl group, which
Reactivity. The group of Woo investigated the reactivity of
titanium imido porphyrins toward different subtrates.11
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a
Compare these results with the reactivity of the corresponding
phthalocyanines we carried out nitrene transfer reactions using
7, p-chlorobenzaldehyde, nitrosobenze, triphenylphosphine
oxide, and styrene oxide as substrates (Scheme 7). The
Table 1. Polymerization of Ethene
activity/
precatalyst
t/h p/bar mpolymer/g Tm/°C
g mol−1 h−1 bar−1
b
[Pc#TiCl2]
1
1
0.27
0.01
1.00
1.782
137
134
27
1
b
[Pc#TiO]
1
1
Scheme 7. Nitrene Transfer Reaction of 7
c
[NPcVO]
4
48
1
0.5
356
b
Eurecen 5031
0.5
133
a
b
Reaction conditions. ncat = 10 μmol, nMAO = 10 mmol, 1000 equiv,
c
in 50 mL of chlorobenzene, 50 °C. Ref 59; ncat = 10 μmol, nMAO = 1
mmol, 100 equiv, in 10 mL of chlorobenzene in a 120 mL glass lined
autoclave, 50 °C.
Crystal Structures of Pc#H2, 1 and 5. In addition to the
crystal structure of [Pc#TiO] 1·3CHCl3 reported previously,40
we were able to obtain slightly different structures by
crystallization from dichloromethane and benzene (see
Supporting Information). In all cases, a coplanar arrangement
of the macrocycles is present independently of the incorporated
solvent. We do not observe face-to-face dimers which are
typically found in highly aggregating derivatives of unsub-
stituted chromophore complexes [PcTiO].2,39,60 No significant
changes of bond lengths and angles within the molecules are
found. The different solvent molecules incorporated in the
lattice cause minor differences in the packing and the
intermolecular distances.
progress of the reactions was monitored via NMR spectrosco-
py, and the identity of the products was confirmed by
electrospray ionization (ESI) HRMS spectrometry. No reaction
was observed with triphenylphosphine oxide and styrene oxide.
In the case of p-chlorobenzaldehyde, the imido group transfer
was incomplete after 24 h at room temperature. According to
1H NMR spectroscopy, a mixture of 70% [Pc#Ti(NMes)] and
30% [Pc#TiO] was present and no further reaction occurred.
Still, the formation of p-chlorobenzylidene mesitylamine was
unambiguously confirmed by ESI HRMS. This compares well
with the result for corresponding porphyrins where complete
nitrene transfer to p-chlorobenzaldehyde only occurred after 4
weeks or in the presence of excess substrate.11 Upon addition
of nitrosobenzene to a solution of 7 in C6D6, complete
consumption of the starting materials and synchronous
formation of mesityl phenyl diazene occurred within 5 min.
These results show that the reactivity of titanium imido
phthalocyanines toward nitrene transfer is comparable to
corresponding titanium imido porphyrins.
The free ligand Pc#H2 was crystallized by layering a toluene
solution with pentane in the absence of air, moisture, and
light.61 Pc#H crystallizes in the trigonal space group R3 with
̅
2
three molecules per unit cell. The molecular structure is
displayed in Figure 3. Toluene and disordered molecules of
Some examples of phthalocyanines used in polymerization
catalysis have been described in the literature.55−58 For
example, it has been reported that soluble vanadyl and nickel
naphthalocyanines can polymerize ethene at high pressure.59
Because of the cis arrangement of the chlorido ligands, 5
seemed a suitable precatalyst for olefin polymerization (Scheme
8). We therefore tested the activity of dichlorido compound 5
Scheme 8. Poymerization of Ethene Using 5
Figure 3. Molecular structure of Pc#H2. Ellipsoids are shown at 30%
probability. H atoms (except NH) are omitted for clarity. Symmetry
operation used to generate equivalent atoms: a = −x+1/3,−y+2/3,−z
+2/3.
pentane are included in the molecular packing. The molecule
possesses an inversion center. The aromatic heterocycle is
essentially planar, and the annulated cyclohexene rings adopt a
twist-boat conformation. Because of intramolecular hydrogen
bonds, the NH protons do not lie on the N3−N3a axis but are
oriented toward N1. The bond lengths and angles of the Pc
core compare well to the values reported for unsubstituted
PcH2.62−64 Selected bond lengths and angles are summarized in
Table 2. Crystallographic data are summarized in Table 3.
The molecular packing of Pc#H2 is shown in Figure 4. The
three molecules present in the unit cell are oriented almost
perpendicular with respect to each other (angle between N4
planes = 88.3(1)°). This kind of arrangement has not been
described for any of the polymorphs of PcH2, where either two
or four orientations of the macrocycles are present.62−64
and titanyl Pc 1 in the polymerization of ethene at atmospheric
pressure using 1000 equiv of MAO as cocatalyst. For
comparison we also employed Eurecen 5031
[ZrIV(nBuC5H4)2Cl2] as precatalyst under the same conditions.
The results of the polymerization experiments are summarized
in Table 1. Taking into account that the experiments were
conducted at atmospheric pressure, these results show that the
catalytic activity of the dichlorido compound is significantly
higher than for the titanyl and vanadyl species.59 Yet, the
activities are much lower than for well established ethene
polymerization catalysts such as Eurecen 5031. Still, these
results show that the reactivity of the central titanium atom in
soluble phthalocyanine complexes is in principle comparable to
that in other titanium complexes.
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Table 2. Selected Bond Lengths (Å) and Angles (deg) for
Pc#H2
C1−N1
N1−C2
C2−N2
N2−C3
C3−N3
N3−C4
1.369(6)
1.383(6)
1.339(6)
1.320(6)
1.392(7)
1.353(6)
N3−H1N
C4−N4
N4−C1a
C3−N3−H1N
C4−N3−H1N
0.95(5)
1.326(6)
1.347(6)
112(4)
136(4)
Table 3. Crystal Data and Structure Refinement for Pc#H2
and 5
Figure 5. Molecular structure of 5. Ellipsoids are shown at 30%
probability. Disorder of the cyclohexene rings and H atoms are
omitted for clarity. Symmetry operations used to generate equivalent
atoms: a: x, −y+1, z; b: −x, −y+1, z; c: −x, y, z.
Pc#H2
5
formula
fw
C239H282N24
3490.89
C135H158Cl18N16Ti2
2738.62
crystal system
space group
a, Å
trigonal
cubic
disordered. The two chlorido atoms are located on the same
side of the macrocycle in a cis arrangement, which is also
present in [PcTiCl2]. The chlorido ligands lie on the N3−Ti−
N3b plane. The Ti1−Cl1 bond length is 2.328(2) Å and is
slightly longer than in [PcTiCl2] (2.309(6) and 2.324(5) Å).
The titanium atom is displaced from the N1-plane toward the
chlorido ligands about 0.834 Å. Thus, the displacement is
comparable to the structure of [PcTiCl2] (0.84 Å)30 and larger
than in [Pc#TiO] (0.748 Å).40 The coordination around the
titanium atom is trigonal prismatic. Selected bond lengths and
angles are summarized in Table 4. The values compare well
R3
̅
Im3
̅
32.4964(18)
32.4964(18)
16.3282(10)
90
28.953(4)
28.953(4)
28.953(4)
90
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
90
90
120
90
14932.7(15)
3
24270(6)
6
Z
D
calcd, g/cm3
1.165
1.124
μ, cm−1
0.068
0.442
F(000)
5652
8580
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 5
and [PcTiCl2]
crystal size, mm3
reflns collected
independent reflns
Rint
0.21·× 0.21·× 0.03
18941
0.24·× 0.21·× 0.03
4563
a
7016
4563
5
[PcTiCl2]
2.324(5), 2.309(6)
0.0960
0.0000
Ti1−Cl1
Ti1−N1
2.328(2)
2.086(3)
81.7(1)
83.5(1)
135.9(1)
78.8(2)
a
R indices [I > 2σ(I)]
R1 = 0.0586
wR2 = 0.1043
R1 = 0.3209
wR2 = 0.1782
R1 = 0.0613
wR2 = 0.1399
R1 = 0.1472
2.090(13), 2.095(9), 2.060(10), 2.106(10)
82.41(19)
Cl1−Ti1−Cl1a
N1−Ti1−Cl1
N1a−Ti1-Cl1
N1−Ti1−N1a
N1−Ti1−N1b
R indices (all data)
88.0(3), 79.4(3), 80.8(4), 87.4(4)
127.0(4), 127.8(3), 145.1(3), 143.7(4)
78.7(4), 79.1(4)
wR2 = 0.1601
a
R1 = [∑||Fo| − |Fc||/∑|Fo|]; wR2 = {[∑w(Fo2 − Fc2)2/∑w(Fo )]1/2}.
4
132.9 (2) 135.7(5), 129.6(5)
a
The values refer to the corresponding bond lengths and angles.
with those found for the unsubstituted phthalocyanine complex
[PcTiCl2]. The macrocyle deviates slightly from planarity,
adapting a “saucer” type structure.2
Figure 6 shows the molecular arrangement within the unit
cell. The macrocycles are arranged as face-to-face dimers, and
neighboring dimers are aligned essentially perpendicular to
each other. In contrast to this, in the structures of the related
compounds [PcTiCl2]30 and [Pc#TiO]40 layered arrangements
are present, where all the macrocycles lie essentially parallel. It
has been found that only the polymorphs exhibiting the
colinear arrangement can be applied in semiconducting
devices.65 Therefore, 5 is not expected to show good
semiconducting properties in the presented crystal phase.
Solid state fluorescence spectroscopy could show whether the
dimeric arrangement leads to fluorescence quenching, and
comparison of the fluorescence properties of [Pc#TiCl2] and
[Pc#TiO] in solid state are therefore of interest.
Figure 4. Molecular packing of Pc#H2. Solvent molecules and H atoms
are omitted for clarity.
5 crystallizes from a saturated dichloromethane solution in
the cubic space group Im3. The crystal structure of 5 is
̅
displayed in Figure 5. Crystallographic data are summarized in
Table 3. Because of the symmetry of the molecule, only one
isoindoline moiety is present in the asymmetric unit. Also, the
twist-boat conformation of the annellated cyclohexene rings is
CONCLUSIONS
■
In this work we describe the synthesis of various soluble, axially
substituted titanium phthalocyanines under mild conditions.
Oxido compound 1 could be converted into peroxido species
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Figure 6. Molecular packing of [Pc#TiCl2] 5. Disorder of the
cyclohexene rings, 3.5 disordered molecules of dichloromethane per 5,
and H atoms are omitted for clarity.
10 and Lewis acid adduct 15. [Pc#TiCl2] 5 is a versatile
precursor for the introduction of various functionalities, such as
imido (6, 7), alkoxido and aryloxido (8, 9), sulfido 12, disulfido
11, selenido 14, and diselenido 13. In most cases the
photophysical properties of the prepared compounds are very
similar, and the nature of the axial ligand has no significant
effect on the Q-band maximum. In contrast to this, the Q-band
maxima are shifted bathochromically in the cases of the higher
homologues of [Pc#TiO] 1, [Pc#TiS] 12, and [Pc#TiSe] 14,
respectively. The reactivity of selected functionalized Pcs in
atom group transfer reactions and ethene polymerization has
been demonstrated. The crystal structures of the free ligand
Pc#H2, 1, and 5 reveal different arrangements of the
macrocyclic systems (coplanar, three-dimensional, and dimer-
ic), which should affect the photophysical properties of the dyes
in solid state. Our next goal is to investigate how the different
axial functionalities may be employed to anchor these
nonaggregating phthalocyanine chromophores to different
wide band gap metal oxide semiconductor surfaces and thus
prepare optoelectronic devices.
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ASSOCIATED CONTENT
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available free of charge via the Internet at http://pubs.acs.org.
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(27) Zhang, X.-F.; Wang, Y.; Niu, L. J. Photochem. Photobiol. A 2010,
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Corresponding Author
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Phone: +49 (0)6421 28-25693.
Notes
The authors declare no competing financial interest.
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