First X-ray crystallographic study of a meso-substituted tetrabenzotriazaporphyrin: Structural effect of a meso-aryl unit on 27-(2-methylphenyl)tetrabenzotriazaporphyrinato zinc example in comparison with zinc phthalocyaninate

Article abstract of DOI:10.1016/j.dyepig.2014.02.012

A recently developed synthetic procedure afforded meso-aryl substituted tetrabenzotriazaporphyrin complex, namely 27-(2-methylphenyl)tetrabenzo[b,g,l,q] [5,10,15]triazaporphyrinato zinc (^2-MePhTBTAPZn, 1). The reaction also produced zinc phthalocyanine (PcZn, 2) as a byproduct. The complexes were characterized by the UV-Vis, NMR spectroscopy as well as MALDI-TOF mass spectrometry. Furthermore, they form supramolecular structures [1·DMSO]·2(DMSO) (I) and [2·DMSO]·0.65(DMSO) ·0.5(CH₃OH) (II) determined by single-crystal X-ray diffraction analysis. To the best of our knowledge, I represents the first X-ray defined structure of a meso-substituted TBTAP derivative. Both structures were shown to be composed of centrosymmetric dimers, which are stabilized by the axial π-stacking intermolecular interactions. Comparison of the data for I and II indicates that the presence of the meso-aryl substituent in the TBTAP molecule results in considerable and even unexpected structural effects.

Full text of DOI:10.1016/j.dyepig.2014.02.012

Dyes and Pigments 105 (2014) 216e222
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
First X-ray crystallographic study of a meso-substituted
tetrabenzotriazaporphyrin: Structural effect of a meso-aryl unit on
27-(2-methylphenyl)tetrabenzotriazaporphyrinato zinc example in
comparison with zinc phthalocyaninate
,
b
,
c
a,b
Valery V. Kalashnikov a, Victor E. Pushkarev a , Zoya A. Starikova , Larisa G. Tomilova
*
a Institute of Physiologically Active Compounds, Russian Academy of Sciences, 1 Severny Proezd, 142432 Chernogolovka, Moscow Region, Russian
Federation1
b Department of Chemistry, M.V. Lomonosov Moscow State University, 1 Leninskie Gory, 119991 Moscow, Russian Federation2
c A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova Street, 119991 Moscow, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
A
recently developed synthetic procedure afforded meso-aryl substituted tetrabenzotri-
azaporphyrin complex, namely 27-(2-methylphenyl)tetrabenzo[b,g,l,q][5,10,15]triazaporphyrinato zinc
2ꢀMePhTBTAPZn, 1). The reaction also produced zinc phthalocyanine (PcZn, 2) as a byproduct. The
Received 19 December 2013
Received in revised form
23 January 2014
Accepted 11 February 2014
Available online 19 February 2014
(
complexes were characterized by the UVeVis, NMR spectroscopy as well as MALDI-TOF mass spec-
trometry. Furthermore, they form supramolecular structures [1$DMSO]$2(DMSO) (I) and [2$DMSO]$
0.65(DMSO)$0.5(CH3OH) (II) determined by single-crystal X-ray diffraction analysis. To the best of our
knowledge, I represents the first X-ray defined structure of a meso-substituted TBTAP derivative. Both
structures were shown to be composed of centrosymmetric dimers, which are stabilized by the axial
Keywords:
Tetrabenzotriazaporphyrins
Phthalocyanines
p
-stacking intermolecular interactions. Comparison of the data for I and II indicates that the presence
of the meso-aryl substituent in the TBTAP molecule results in considerable and even unexpected
XRD crystallography
structural effects.
pep interactions
Crystal packing
UVeVis spectroscopy
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
photostability characteristic for the Pc molecules. Presence of
methine bridges at meso-positions allows subsequent functionali-
Tetrabenzotriazaporphyrins (TBTAPs) belong to a family of low
symmetry compounds related to both phthalocyanine (Pc) and
tetrabenzoporphyrin (TBP) ring systems [1], where Pc core is
modified by replacement of one of the four aza bridges by methine
group. The key feature of such hybrid molecules is that they can
combine useful properties of Pcs and TBPs to extend own applica-
bility. For instance, Borisov and coworkers [2] recently showed that
metal complexes of monoaza- and cis-diazatetrabenzoporphyrins
similarly to TBPs possess strong room temperature NIR phospho-
rescence, which is successfully combined with excellent
zation, which generally leads to the improvement of solubility and
facilitates coupling with molecules and surfaces [1b]. Furthermore,
introduction of meso-substituents to the molecules of TBTAP
derivatives can favorably promote self-assembly [3], which is
crucial for fabrication of well-organized LangmuireBlodgett
monolayer films [3a], creation of stable mesophases [3b], as well as
for crystal growth and design. However, with all this, single-crystal
X-Ray diffraction (XRD) data for TBTAP or any other partially
aza-substituted TBP derivatives, which bear substituents at meso
positions, are still missing in literature. To the best of our knowl-
edge, XRD structure determination for TBTAPs was performed so
far in the case of unsubstituted free-base ligand [4], its copper
derivative [5], and a while ago reported 1,4,8,11,15,18,22,25-
octahexyl-29H,31H-TBTAP [6a], as well as corresponding magne-
sium complex [6b].
* Corresponding author. Institute of Physiologically Active Compounds, Russian
Academy of Sciences, 1 Severny Proezd, 142432 Chernogolovka, Moscow Region,
Russian Federation. Fax: þ7 496 524 9508.
E-mail
addresses:
kalashn2000@mail.ru
(V.V.
Kalashnikov),
pushkarev
@org.chem.msu.ru, np.ruff@gmail.com (V.E. Pushkarev), tom@org.chem.msu.ru
(L.G. Tomilova).
Recently we improved synthetic techniques for meso-aryl-
substituted planar TBTAPs [7a,b] and obtained first sandwich
complexes based on TBTAP derivatives [7c]. Herein we report the
1
Fax: þ7 496 524 9508.
2
Fax: þ7 495 939 0290.
http://dx.doi.org/10.1016/j.dyepig.2014.02.012
0143-7208/Ó 2014 Elsevier Ltd. All rights reserved.

V.V. Kalashnikov et al. / Dyes and Pigments 105 (2014) 216e222
217
Table 1
first XRD crystallographic characterization of a meso-substituted
Main crystallographic data and structure refinement for I and II.
TBTAP molecule, namely, 27-(2-methylphenyl)tetrabenzo[b,g,l,q]
[5,10,15] triazaporphyrinato zinc (2ꢀMePhTBTAPZn, 1). Moreover, in
order to identify and estimate the structural effect of meso-substi-
tution we also carried out XRD investigation of zinc phthalocyani-
nate (PcZn, 2), which was crystallized under conditions identical to
1. It is also helpful and noteworthy that the XRD data set collected
for zinc Pcs is quite representative and reveals several structural
patterns with single crystals formed both in solution [8] and sub-
limed phases [9].
I
II
Formula
C46H41N7O3S3Zn
C35.80H27.90N8O2.15
S1.65Zn
Mol. weight
Crystal system
Space group
901.41
Triclinic
P-1
722.83
Triclinic
P-1
ꢀ
a, [A]
11.9543(5)
12.5664(5)
14.9683(6)
79.829(2)
82.674(3)
65.908(2)
2016.6(1)
2
12.2784(10)
16.5745(14)
17.5752(15)
85.743(2)
81.299(2)
71.697(2)
3355.3(5)
4
ꢀ
b, [A]
ꢀ
c, [A]
a
b
g
, [ꢁ]
, [ꢁ]
, [ꢁ]
2. Experimental
3
ꢀ
Volume, V, [A ]
Z
2.1. Chemicals and instruments
Calc. density, Dc, [g cmꢀ3
]
1.485
1.431
Cryst. size, [mm3]
0.55 ꢂ 0.42 ꢂ 0.10
Dark green plates
1.54178
2.726
0.55 ꢂ 0.42 ꢂ 0.27
Purple-red plates
0.71073
Column chromatography was carried out on Lancaster Silica Gel
60 (0.060e0.200 mm), Merck Silica Gel 40 (0.063e0.200 mm),
MachereyeNagel Aluminum oxide 90 neutral, MachereyeNagel
Silica Gel 60 (0.040e0.063 mm) with mixtures of hexane/THF and
toluene/dioxane as eluents. TLC was performed on flexible plates
Merck Silica Gel 60 and Merck Silica Gel 60 F254 with above
mentioned eluents. All other reagents and solvents were obtained
or distilled according to standard procedures. The reaction was
monitored by TLC and UVeVis spectroscopy and continued until
complete disappearance of starting reagents was observed.
Cryst. color and shape
ꢀ
l
, [A]
Abs. coeff.,
m
, [mmꢀ1
]
0.881
Absorption correction
SADABS
0.2742/0.3529
52.50
SADABS
0.0043/0.0253
52.00
Tmin/Tmax
2
qmax, [ꢁ]
Total refls
17986
32061
Independent refls (Rint
Completeness, [%]
)
4351 (0.0502)
98.5
0.044 (4351)
0.105 (4537)
553
13026 (0.0583)
98.7
0.069 (7302)
0.136 (13061)
936
R1 on F for refls with [I > 2
s
(I)]a
wR2 on F2 for all refined reflsb
Total refined parameters
Goodness of fit
UVeVis electronic absorption spectra were recorded with a Ther-
moSpectronic Helios-a spectrophotometer by using 0.5 cm quartz
0.999
1.159
F(000)
936
1489
cells with samples dissolved in THF. MALDI-TOF mass spectra were
taken with a VISION-2000 mass spectrometer with 2-[(2E)-3-(4-tert-
butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) as
matrix. 1H NMR spectra were recorded with a Bruker AVANCE 400
spectrometer (400.13 NHz) with samples dissolved in DMSO-d6 at
Residual electron density, Drmax
,
þ0.886
þ2.775
ꢀꢀ3
Drmin, [e A
]
ꢀ0.563
ꢀ0.727
CCDC
932023
932024
P
P
a
R1
¼
jjFoj ꢀ jFcjj/ jFoj.
P
P
b
½
wR2
¼
{
[w(F2o
ꢀ
F2c)2]/ wF4o}
;
wꢀ1
¼
s
2(F2o)
þ
(aP)2
þ
bP, where
P ¼ (F2o þ 2F2c)/3. The a parameter is 0.0392 for I and 0.0256 for II; the b parameter is
6.5820 for I and 4.9540 for II.
20 ꢁC. Chemical shifts
d are given in ppm relative to SiMe4.
2.2. Synthesis and characterization
(MALDI-TOF), m/z: calcd. for C32H16N8Zn [M]þ 576.08; found
576.26.
The dark-green single crystals of [1$DMSO]$2(DMSO) (I) and
purple-red crystals of [2$DMSO]$0.65(DMSO)$0.5(CH3OH) (II)
suitable for X-ray analysis were obtained by slow evaporation of the
air-exposed DMSO solutions at room temperature.
2.2.1. Preparation of 2ꢀMePhTBTAPZn (1) and PcZn (2)
A mixture of phthalonitrile (0.64 g, 5.0 mmol), (2-methylbenzyl)
triphenyl-phosphonium chloride (0.40 g, 1 mmol) and zinc powder
(0.20 g, 3 mmol) was heated under argon to 200 ꢁC. The resulting
yellow-orange melt soon became blue-green with following
transformation into dark-blue crystalline solid. Then the tempera-
ture was raised to 300 ꢁC, and the mixture was held for 6 h. The
mixture was cooled to room temperature, and the resulting dark
blue crystalline product was then dissolved in hot THF. The insol-
uble admixture of PcZn was filtered off, the solution concentrated
and then subjected to column chromatography (silica gel, eluent e
hexane/THF, 5/2), from which a blue-green band containing target
1 was collected. This band was chromatographed again (silica gel,
eluent e toluene/dioxane, 10/1) followed by recrystallization from
THF/CH3OH, giving blue-violet crystals, which were finally dried in
vacuo at 140 ꢁC to yield 72 mg of 1 (11%). Collected PcZn was
repeatedly washed with boiling CH3OH (4 ꢂ 20 mL) and dried in
vacuo at 140 ꢁC to yield 72 mg of 2 (25%).
2.2.1.1. X-ray crystallography. Crystallographic data were collected
on a Bruker APEX II CCD area detector at 100 K (lCu-Ka radiation,
ꢀ
l
¼ 1.54178 A, 2qmax ¼ 52.5ꢁ for I; graphite monochromated
lMo-
ꢀ
K
a
radiation,
l
¼ 0.71073 A, 2qmax ¼ 52.0ꢁ for II).
Single crystal of I was twinned. The obtained set of reflections
was indexed by the CELL_NOW software [10], the reflection in-
tensities agree with superposition of the two single-crystal com-
ponents connected by approximately 9.3ꢁ rotation around direction
[0 ꢀ1 2]. However, the contribution of both components cannot be
taken into account exactly. Definitive refinement was satisfied by
the reflections corresponding to the first component (HKLF 4) in
the format TWIN/BASF (BASF ¼ 0.19). Single crystal of II was also
twinned; however extraction of primary part was unsuccessful. In
Data for 1: 1H NMR (DMSO-d6):
H), 7.65e8.27 (m, 12H, -H, (2-tolyl)-H), 7.03 (d, 2H,
d
¼ 9.30e9.57 (m, 6H,
a -
1-H, a2
b
a
3-H), 1.98 (s,
3H, methyl-H). UVeVis [THF, lmax/nm (I/Imax)]: 380 (0.379), 442
(0.115), 592 (0.157), 608 (0.154), 616 (0.157), 646 (0.665), 670
(1.000). UVeVis [DMSO, lmax/nm (I/Imax)]: 384 (0.314), 445 (0.109),
598 (0.143), 612 (0.154), 619 (0.154), 652 (0.571), 677 (1.000). MS
(MALDI-TOF), m/z: calcd. for C40H23N7Zn [M]þ 665.13; found
665.06.
Data for 2: UVeVis [THF, lmax/nm (I/Imax)]: 344 (0.326), 603
(0.172), 640 sh (0.162), 667 (1.000). UVeVis [DMSO, lmax/nm
(I/Imax)]: 346 (0.358), 607 (0.216), 645 sh (0.199), 673 (1.000). MS
Scheme 1. Synthesis of zinc TBTAP (1) and Pc (2) complexes.

218
V.V. Kalashnikov et al. / Dyes and Pigments 105 (2014) 216e222
Fig. 3. UVeVis spectra of 1 (ca. 1.5 ꢂ 10ꢀ5 M) in DMSO (a) and 80% aqueous DMSO (b)
indicating a tendency to predominant formation of aggregates close to H-type.
addition, all DMSO and CH3OH molecules are highly disordered,
and it is impossible to find correct way to resolve this disorder.
The structures were solved by direct methods; non-hydrogen
atoms were localized in difference electron-density syntheses and
refined on F2
in anisotropic approximation. Hydrogen atoms
hkl
were included in geometrically calculated positions and refined in
isotropic approximation by riding model with U(H) ¼ 1.2 U(C),
where U(C) is the equivalent thermal factor of the C atom, to which
corresponding H atom is bonded. All calculations were performed
on an IBM PC/AT using the SHELXTL software [11].
Crystallographic parameters of structural determination and
refinement are given in Table 1. Atomic coordinates, bond lengths
and angles, thermal parameters are deposited in the Cambridge
Crystallographic Data Centre (CCDC-932023-4) and can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif
(or from the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK;
fax þ44 1223 335 033; or by e-mail deposit@ccdc.cam.ac.uk).
3. Results and discussion
3.1. Synthesis and characterization
Fig. 1. MALDI-TOF mass spectra of 1 (top), 2 (bottom) with DCTB used as matrix
(isotopic patterns for the molecular ions are shown in insets).
Target compound 2ꢀMePhTBTAPZn (1) was synthesized according
to a recently developed procedure [7b] by the template reaction in
a melt. A mixture of phthalonitrile, (2-methylbenzyl)triphenyl-
Fig. 4. UVeVis spectra of 2 (ca. 1.0 ꢂ 10ꢀ5 M) in DMSO (a) and 80% aqueous DMSO (b)
indicating a tendency to predominant formation of aggregates close to J-type.
Fig. 2. UVeVis spectra of 1 and 2 in THF.

V.V. Kalashnikov et al. / Dyes and Pigments 105 (2014) 216e222
219
Table 2
reagents, and second, it affords TBTAP compound 1 without ad-
mixtures of di- and triarylated derivatives [12b] or corresponding
TBP byproduct.
Comparison of selected parametersa in supramolecular structures I and II.
I
IIA
IIB
The obtained complexes 1 and 2 were characterized by MALDI-
TOF mass spectrometry, 1H NMR and UVeVis spectroscopy. The
mass spectra contain corresponding molecular ion peaks with
isotopic distribution typical for zinc compounds (Fig. 1).
ꢀ
dZneN, [A]
2.025(3)e2.040(3) 2.009(4)e2.033(4) 2.017(4)e2.034(4)
ꢀ
dZneO, [A]
2.123(2)
0.298
3.288
4.210
3.648
1.580
2.076(4)
0.397
3.292
5.686
5.130
3.934
50.78
2.086(10)
0.394
3.322
5.598
5.040
ꢀ
dZne4N, [A]
ꢀ
d4N, [A]
ꢀ
dZneZn, [A]
The 1H NMR spectrum of 1 matches with that reported previ-
ously [7b]. The UVeVis spectra (Fig. 2) are characterized by the
presence of the intense Q absorption bands in the visible long-wave
region at 646e670 nm and the less intense B bands in the UV region
at 344e442 nm. Note the splitting of the absorption maxima for 1,
which is characteristic for both planar [1,7a,b] and sandwich [7c]
TBTAP complexes due to decreased molecular symmetry.
Furthermore, aggregation behavior in aqueous DMSO solutions
was examined for both compounds (Figs. 3 and 4). In the case of 1,
the aggregates formed can be attributed to the H-type [13], since
they are characterized by the appearance of a new broad absorption
band with the maximum at 620 nm, which is hypsochromically
(UV) shifted with respect to the Q band of the monomer. A similar
tendency also can be observed in the B band region. In contrast, the
ꢀ
dc4N, [A]
ꢀ
dshift, [A]
3.790
Shift angle, [ꢁ] 25.88
44.04
a
Selected distances and angles are denoted according to Fig. S3; N denotes Niso
atoms; O denotes O atom of the apical DMSO molecule.
phosphonium chloride and zinc powder was gradually heated from
200 to 300 ꢁC (Scheme 1). The reaction also produced PcZn com-
plex (2) as a byproduct. The complexes were further separated and
purified by column chromatography.
There are two main advantages of the elaborated technique
over the earlier published methods [12]. First, it does not employ
air/water sensitive, e.g. Grignard [12a], or any other unstable
Fig. 5. Crystal structures of I (top left) and two independent molecules IIA (top right) and IIB (bottom). Thermal ellipsoids are drawn at the 30% probability level.

220
V.V. Kalashnikov et al. / Dyes and Pigments 105 (2014) 216e222
aggregation of 2 is more close to the J-type [13] as indicated by the
emergence of a pronounced bathochromically (NIR) shifted ab-
sorption in the wide region up to 850 nm. Cumulatively, the
observed features imply that during the assembly the interacting
molecules are less relatively shifted in the case of 1 as compared
with 2, which finds a good correlation with the XRD data discussed
below. Note that UVeVis spectra measured for crystallized com-
pounds 1 and 2 reveal the same peculiarities as the aggregates in
solution yet characterized by lower quality typical for solid samples
and, therefore, not presented herein.
the macrocycle and axially by O atom of DMSO molecule with
generally close values of ZneN and ZneO bond lengths for both
structures I and II. Selected bond distances, angles and other
characteristic parameters are summarized in Table 2. The interac-
tion of the central Zn atom with the apical O atom of DMSO leads to
a deviation of Zn from the center of cavity, which is less pro-
nounceable for I (parameter dZne4N, Table 2). Additionally, in two
independent structures IIA and IIB the coordinated DMSO mole-
cules are partially disordered as opposed to I, where they are
strictly fixed (Fig. 5). In aggregate, this suggests a denser apical
packing in the structure I.
The TBTAP and Pc molecules in both structures form centro-
symmetric dimers [1$DMSO]2 and [2$DMSO]2 with an external
orientation of the DMSO molecules (Fig. 6). The ring-to-ring sepa-
ration of the two virtually parallel macrocycle mean planes, d4N
3.2. XRD structural analysis
The molecular and crystal structures of Zn complexes 1 and 2
were determined by XRD method. Suitable single crystals were
obtained by slow crystallization from concentrated DMSO solu-
tions. The compounds form supramolecular structures [1$DMSO]$
2(DMSO) (I) and [2$DMSO]$0.65(DMSO)$0.5(CH3OH) (II), which
belong to the triclinic space group P-1 and contain respectively two
TBTAP and four Pc molecules per unit cell as defined by XRD
analysis (Table 1).
ꢀ
(Table 2), varies close to 3.3 A, which is shorter than van der Waals
In both supramolecular complexes each Zn(II) center exhibits
4 þ 1 coordination forming a distorted square pyramid. The Zn
atom is equatorially coordinated by four isoindole N atoms (Niso) of
Fig. 6. Supramolecular centrosymmetric dimer {I 4 I’} in crystal of I (top) and its
space-filling representation (bottom).
Fig. 7. Packing arrangement of the supramolecular structure I in a trimetric (top) and a
side view (bottom) supplemented by a schematic representation of the dimeric layers.

V.V. Kalashnikov et al. / Dyes and Pigments 105 (2014) 216e222
221
ꢀ
distance for aromatic systems (ca. 3.5 A) and comparable with that
The crystal packing of the dimers in I and II further supports the
above statements. Thus, in I the dimers are arranged in highly or-
dered layers, while the interlayer space is filled with the solvate
DMSO molecules (Fig. 7 and S4).
found in the bis(tetrapyrrole) rare-earth element (REE) doublee
decker complexes in the range of 2.65e3.40 A [14]. Thus, existence
of considerable axial p-stacking interactions in the structures I and
ꢀ
II can be reasonably stated. A similar tendency to dimerization was
previously shown in the crystal structures of some zinc Pcs [8a,b,i],
yet they were characterized by comparatively longer interplanar
distances. The substituted PcZn dimers with an internal orientation
of the coordinated molecules were reported as well [8d], but the
separation of the Pc rings predictably was more pronounced lead-
The separation between the layers defined as the distance be-
tween the 4Niso planes of the opposite TBTAP macrocycles amounts
to about 5.85 A. In turn, the Pc dimers in II form solvent-filled
ꢀ
nanoscale channels containing disordered DMSO and methanol
molecules (Fig. 8). Note that such packing arrangement is still quite
rare for the planar PcZn compounds [8a]. The width of the channel
defined as the distance between the 4Niso planes of the opposite Pc
ing to the weaker
pep interactions. Note that formation of the
ꢀ
dimeric structures in the crystals of TBTAP derivatives was not
observed so far, although the assembly to the trimeric units was
mentioned [5b].
decks in IIA is measured to be 11.18 A, and the height defined as the
separation between the 4N’iso planes of the opposite Pc’ decks in IIB
ꢀ
equals 11 A, consequently, the average diameter of the channel
ꢀ
Mutual orientations, defined by dZneZn, dc4N, dshift and shift angle
parameters (Table 2), as well as distortions from planarity of the
TBTAP and Pc molecules 1 and 2 in the corresponding dimers
(Fig. S1 and S2) are essentially different. We explain these differ-
ences primarily by the structural effect of the meso-aryl moiety
introduced in 1. According to the XRD data, the 2-methylphenyl
substituent is almost perpendicular to the 4Niso plane with the
rotation angle of 88ꢁ, while the methyl groups are directed outside
the dimer, which can be explained by spatial factor and perfectly
illustrated by the space-filling representation in Fig. 6. Another
interesting feature of the meso-aryl in 1 is that it is tilted inside the
dimer by the angle of 4.67ꢁ (Fig S3). In combination with the tilts of
the benzo rings (Fig. S1) this reveals that a slight wave-like
distortion [15] is characteristic for the TBTAP molecules in I,
whereas in II the Pc molecules are close to the dome-shaped
conformation (Fig. S2). Cumulatively, significant decrease of the
macrocycle mutual shift combined with slight yet characteristic
decrease of the interplanar distance can be pointed out for the
centrosymmetric dimers in the TBTAP supramolecular structure I
as opposed to the Pc structure II, which indicates a generally denser
amounts to about 11 A.
Thus, analysis of structural features of I and II on both the mo-
lecular and supramolecular levels reveals that a more dense crystal
packing as well as intensified
p-stacking interactions are charac-
teristic for I. Apparently, this generally results from the presence of
the 2-methylphenyl moiety at the meso-position of the TBTAP core.
Being fundamentally interested in controlling the structural effects
we will focus our further efforts on obtaining and studying of the
single-crystal XRD data for the meso-substituted sandwich-type
TBTAP molecules.
4. Conclusion
Employing
a
novel synthetic procedure the meso-(2-
methylphenyl)substituted 2ꢀMePhTBTAPZn complex 1 was obtained
and characterized by the spectroscopic techniques. The PcZn com-
pound 2 formed as a single macrocyclic byproduct was isolated as
well. Structural features of the single-crystals of 1 and 2 were
investigated by the XRD analysis. The compounds form supramo-
lecular structures I and II, moreover, I represents the first X-ray
structure of a meso-substituted TBTAP derivative. The structures are
composed of centrosymmetric dimers, which are stabilized by the
molecular packing in I and, consequently, enhanced
pep in-
teractions. This represents a quite interesting result taking into
account the presence of such a bulky substituent at the meso po-
sition of 1.
axial
pep interactions between the macrocycles. The detailed
analysis of I and II on both the molecular and supramolecular levels
surprisingly showed that I is characterized by a more dense crystal
packing, and consequently, by enhanced p-stacking interactions. The
main contribution to the revealed differences is proposed to be made
by the presence of the meso-aryl moiety in the TBTAP complex 1.
Acknowledgments
We thank Presidium of the Russian Academy of Sciences,
Council under the President of the Russian Federation for State
Support of Young Scientists and Leading Scientific Schools (Grant
NL-6590.2013.3) and Russian Foundation for Basic Research
(Grants 12-03-00774, 12-03-31125) for financial support.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2014.02.012.
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