1,4,8,11,15,18,22,25-alkylsulfanyl phthalocyanines: Effect of macrocycle distortion on spectroscopic and packing properties

Article abstract of DOI:10.1039/c5cc01085c

The effect of phthalocyanine macrocycle distortion on its spectroscopic and packing properties is studied, by comparing two phthalocyanines octa-non-peripherally substituted by alkanethiols of different bulkiness (n-hexyl and tert-butyl). Their X-ray structures evidence their core shape, respectively planar and strongly distorted, inducing a 55 nm shift of their maximum absorption wavelength. Comparison of frontier orbital energies revealed that this distortion decreases the conjugation potency of the benzo rings to the central pyrrolic rings. Also the tert-butyl derivative presents a MOF-like porous crystalline assembly with 22.2% void.

Full text of DOI:10.1039/c5cc01085c

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Y. Zorlu, U.
Kumru, Ü. ci, B. Divrik, E. Jeanneau, F. Albrieux, Y. Dede, V. Ahsen and F. Dumoulin, Chem. Commun.,
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

Page 1 of 4
ChemComm
Dynamic Article Links ►
Journal Name
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
View Article Online
DOI: 10.1039/C5CC01085C
ARTICLE TYPE
1, 4, 8, 11, 15, 18, 22, 25-Alkylsulfanyl phthalocyanines. Effect of
macrocycle distortion on spectroscopic and packing properties
a
a
a
b
c
d
Yunus Zorlu, Ufuk Kumru, Ümit İşci, Burcin Divrik, Erwann Jeanneau, Florian Albrieux, Yavuz
b
a
a
Dede, Vefa Ahsen and Fabienne Dumoulin*
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
The effect of phthalocyanine macrocycle distortion on their
spectroscopic and packing properties is studied, by
comparing two phthalocyanines octa non-peripherally
substituted by alkanethiols of different bulkiness (n-hexyl and
tert-butyl). Their X-ray structures evidence their core shape,
respectively planar and strongly distorted, inducing a 55 nm
shift of their maximum absorption wavelength. Comparison
of frontier orbital energies revealed that this distortion
decreases the conjugation potency of the benzo rings to the
central pyrrolic rings. Also the tert-butyl derivative presents a
MOF-like porous crystalline assembly with 22.2 % void.
1
0
1
5
Since their first use as dyes and pigments, phthalocyanines have
gained technological recognition, as their electronic and optical
properties are desired in a large number of highly specialized
2
2
3
3
4
4
0
5
0
5
0
5
1
applications. Controlled modulation of their photophysical
properties is crucial and must be tailored accordingly to the
targeted applications. The effect of substituent nature, number
and position on the Q band maximum absorption wavelength of
2
phthalocyanines is well known. NIR (Near Infra-Red) absorption
3
3b-c
is desired in several fields, such as photodynamic therapy,
3
d
4
imaging or light havesting. Non-peripheral substitution and
5
sulfanyl grafting are both known to red-shift the maximum
absorption wavelength of phthalocyanine Q-band, and have been
previously combined to shift the maximum electronic absorption
6
up to 800 nm. Aggregation (dimerization then oligomerization of
7
phthalocyanine macrocycle via their π-π stacking ) limits or even
inhibits the electronic events inducing the desired properties. The
steric hindrance of bulky substituents prevents macrocycles to
come close to each other enough to aggregate, and are commonly
used to lower aggregation and retain phthalocyanine electronic 50 ellipsoids drawn at the 30% probability level, H atoms omitted for clarity)
properties. Phthalocyanines 1 and 2, respectively octa non-
Fig. 1 a) Molecular structure, b) side view, c) face-on view (displacement
of 1 (left) and 2 (right). See the atom numbering scheme on Fig. S1
peripherally substituted by hexylsulfanyl and tert-butylsulfanyl
revealed by X-ray diffraction (Fig. 1), 1 is planar whereas the
moieties (Fig. 1) were selected as potential non-aggregated NIR
macrocycle of 2 is remarkably distorted.
absorbing molecules, with the aim to explore the effect of the
1
crystallizes in centrosymmetric triclinic P-1 space group.
substituent bulkiness. 1 and 2 were prepared by previously
5
5
The dihedral angles between the four isoindole rings and the
reported lithium-assisted templating method from the
8
mean plane formed by the four pyrrole nitrogens that goes
corresponding phthalonitriles (Scheme S1). Phthalocyanine 2
o
through N
5
4
(isoindole) atoms (N8, N12, N16 and N20) are 3.41 ,
proved to be much less stable than 1, during the course of the
reaction as well as over time. Suitable crystals of 1 were grown
by recrystallization from DCM whereas crystals of 2 were
obtained by diffusion of ethanol into dichloromethane. As
o
o
o
.59 , 4.72 , 9.64 , respectively. The ring planarity is similar to
that of previously published nonperipherally octasubstituted
9
10
11
12
6
0
phthalocyanines (Table S2, entries 2, 4,
5
and 7 ). 2
crystallizes in the non-centrosymmetric cubic space group P-43n.
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

ChemComm
Page 2 of 4
The great steric hindrance of bulky tert-butylthiol groups leads to
an extremely distorted conformation (Fig. 1). The asymmetric 60 imposing -electrons to the -framework of the dye. This
absorbing dyes suggest that the frontier orbitals are fine-tuned by
1
8
View Article Online
unit consists of 1/4 of the phthalocyanine molecule. One of the
butylsulfanyl groups is nearly situated in the same plane as the
rationale operates by shifting the HOMO to higher energies while
DOI: 10.1039/C5CC01085C
the LUMO is usually left unchanged due to being empty. Hence
the HOMO - LUMO gap is decreased and λabs is red-shifted.
Applying this view to the pyrrolic rings of the phthalocyanine
°
5
0
5
0
5
0
5
0
5
0
5
isoindole ring system with an angle of 11.29 between the mean
plane of the isoindole and the plane that goes through atoms C5,
S6, and C7. The second butylsulfanyl group is nearly 65 core and treating the benzylic rings as fused -electron injection
°
perpendicular to the isoindole with an angle of 79.71 between the
agents, the degree of planarity of the phthalocyanine core impacts
the efficiency of -injection which in turn dictates the rise in
HOMO level. The more planar phthalocyanine core of 1
possesses an effectively conjugated -framework whereas -
plane formed by C2, S1, and C17 and isoindole ring. The
o
1
1
2
2
3
3
4
4
5
5
crystallographically equal isoindole rings make angles at 24.08
with the mean plane generated by the four pyrrole nitrogens. The
dihedral angle between the pair of the planes generated by the 70 electrons in 2 are localized on highly perturbed constituents of the
o
isoindole unites on either side of the phthalocyanine is 48.15
phthalocyanine core.
(
Fig. S2). Similar phthalocyanine ring distortions were observed
1
3-
in related 1,4,8,11,15,18,22,25-octasubstituted phthalocyanines
1
6
(
Table S2).
The electronic absorption spectra of both phthalocyanines in
THF at same concentration (Fig 2) evidenced a significant shift
between the two compounds, which have very different colours:
greyish violet for 1 and green for 2. Given the same alkylsulfanyl
nature of the substituents for both compounds, the distortion of
the macrocycle due to the bulkiness of the tert-butyl moieties
seems to be the reason of this 55 nm blue shift for 2. As the
relative spatial disposition of the substituents may not be the
same in solution and on their crystalline form, UV-vis solid state
spectra of each molecule has been recorded (Fig. S8, top). If the
spectra were not fully unequivocal, probably due to the proximity
of the molecules having an aggregation-like effect, colour of the
powder of phthalocyanine 1 and 2 spread out on a white sheet of
paper is similar to those of the solutions colour (Fig. S8, bottom).
These observations are in contradiction with reported statements
asserting the red-shifting effect of phthalocyanine ring
Fig. 2 UV-vis spectra of 1 (violet) and 2 (green) in THF (10 µM)
1
7
distortion. Anyway, there is only a limited number of reports of
phthalocyanine structures (all summarized in Table S2) along
with their UV-vis data, and no systematic interpretation of the
effect of the distortion of the macrocycle could be extracted from
these data, as no “all being equal” data are available: either the
substituent grafting atom is different, or the nature of the
substituents (alkyl vs aromatic). It was therefore decided to
corroborate our experimental UV-vis observations with DFT
calculations. Geometries of 1 and 2 were optimized at various
levels, all of which predicted an unexpected distortion in the core
of 2, while 1 adopted an essentially planar geometry (see Table
S3). We presumed this large degree of distortion as (i) the most
significant difference of 2 compared to 1 and (ii) the source of the
5
5 nm blue-shift in max abs of 2. Therefore frontier orbitals of 1
and 2 were analyzed. As seen from MO plots and energies
depicted in Fig. 3, both HOMOs and LUMOs for both species
show similar spatial distribution and LUMOs are energetically
very close lying. On the other hand, there is a small but
significant difference in energies of HOMOs. This difference
results in a 50 nm blue shift in the absorption wavelength of 2
which is in excellent agreement with the spectroscopic data of 55
nm.
In addition to a quantitative match between experiment and
theory, a sound explanation of the underlying electronic structure 75 Fig. 3 Frontier orbital energies (eV) and plots (isosurface at 0.03) of 1 and
2
at (U)B3LYP/cc-pVTZ, SCRF (Solvent = THF) level of theory. Alkyl
principles that may help rational designing of related systems is
also obtained. Previous experience in accessing long wave-length
chains and hydrogens are excluded for clarity.
2
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 4
ChemComm
Our quantum chemical calculations suggest that HOMO of 45 butylsulfanyl substituted derivative 2 crystallized in a very rare
distorted 2 does not experience an appreciable amount of -
electron injection, whereas the planarity of 1 allows an efficient
porous configuration with a remarkable solvent-accessible void,
View Article Online
likely to be of extreme interest for materials applications.
DOI: 10.1039/C5CC01085C

-system extension. Conformations of the Salkyl groups also
modulate the inductively transferred charge density to the
phthalocyanine core as evidenced by computed charges (Table 50 Acknowledgements
5
0
5
0
5
0
S4). Although the source of the spectroscopic difference is
dictated by structural means, the resultant electronic effect is
neatly seen on frontier orbital levels where an S → S excitation
that is mainly of the HOMO → LUMO type is computed to be 50
nm blue shifted for 2 (measured 55 nm).
The Scientific and Technological Research Council of Turkey
TUBITAK (PIA Turkey-France bilateral project Bosphorus
109M356) is gratefully acknowledged. Y.D. thanks TUBITAK
for support of theoretical studies (project 110T647).
0
1
1
1
2
2
3
Having a look at the packing of the phthalocyanines, one can 55 Notes and references
see that the hexylsulfanyl chains of 1 are nearly planar to the
plane of macrocycle, thereby allowing the formation of abundant
face-to-face π-π stacking (shortest centroid-to centroid distance of
a
Department of Chemistry, Gebze Technical University, P.O. Box 141,
Gebze, 41400 Kocaeli, Turkey. Fax: +90 262 605 30 05; Tel: +90 262
605 30 22. E-mail: fdumoulin@gtu.edu.tr
b
3
.570 Å) interactions, which help to consolidate the packing
Department of Chemistry, Faculty of Science, Gazi University,
6
0
Teknikokullar, Ankara 06500, Turkey
lattice, with no solvent-accessible void in the crystal structure.
The shortest distance between planes of phthalocyanine
molecules within the crystal structure is 3.440 Å (Fig. S1),
whereas in the case of 2, the shortest distance between planes of
c
Centre de Diffractométrie Henri Longchambon, Université Lyon I, 43
boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
d
Centre Commun de Spectrométrie de Masse UMR 5246, CNRS-Claude
Bernard Lyon 1, Université de Lyon, Bâtiment Curien, 43, bd du 11
phthalocyanine molecules was 11.311 Å. Interestingly, 2 has 3-D 65 Novembre, 69622 Villeurbanne Cedex, France
channel voids encapsulated by phthalocyanines with different
†
Electronic Supplementary Information (ESI) available: Synthesis and
pore size (approx. 1.12 and 1.14 nm) in its crystal structure (Fig.
a and 4b), with solvent-accessible void being 22.2 % (2565.1
characterizations, crystallographic data collection and refinement details,
computational details, coordinates of all calculated structures, and energy
4
3
3
Å ) of the unit cell volume (11576.5 Å ) obtaining using the 70 components checkcif files CCDC 894420 (for 1) and CCDC 894419 (for
1
9
2
) and contain the supplementary crystallographic data for 1 and 2. These
data can be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. See
DOI: 10.1039/b000000x/
PLATON ''CALC SOLV''. It should be noted that free guest
molecules using X-ray single-crystal data could not be modelled.
Recently, McKeown and co-workers reported the nanoporous
structures of phthalocyanine-based nanoporous crystals with
important voids, but generated by co-crystallization with
7
8
8
9
9
5
0
5
0
5
1
2
C. G. Claessens, U. Hahn and T. Torres, The Chemical Record, 2008,
, 75
2
0
8
introduction of axial coordinating ligands.
a) Y. Rio, M. S. Rodríguez-Morgade and T. Torres, Org. Biomol.
Chem., 2008, 6, 1877; (b) E. A. Lukyanets and V. N. Nemykin J.
Porphyrins Phthalocyanines, 2010, 14, 1; c) N. Kobayashi, H. Ogata,
N. Nonaka and E. A. Luk’yanets, Chem. Eur. J., 2003, 9, 5123; (d) T.
Nyokong, Coord. Chem. Rev., 2007, 251, 1707.
3
a) G. de la Torre, C. G. Claessens and T. Torres, Chem. Commun.,
2
007, 2000; b) D. Aydın Tekdaş, U. Kumru, A. G. Gürek, M.
Durmuş, Vefa Ahsen and F. Dumoulin, Tetrahedron Lett. 2012, 53,
227; c) M. Machacek, A. Cidlina, V. Novakova, J. Svec, E. Rudolf,
M. Miletin, R. Kučera, T. Simunek and P. Zimcik, J. Med. Chem.
015, 58, 1736; D. Wöhrle, G. Schnurpfeil, S. G. Makarov, A.
5
2
Kazarin, and O. N. Suvorova, Macroheterocycles, 2012, 5, 191.
Y. Zorlu, I. Un and F. Dumoulin, J. Porphyrins Phthalocyanines,
4
2
009, 13, 760.
5
6
P. Gregory, J. Porphyrins Phthalocyanines, 2000, 4, 432.
a) I. Chambrier, M. J. Cook and P. T. Wood, Chem. Commun. 2000,
2
133; b) S. Z. Topal, Ü. İşci, U. Kumru, D. Atilla, A. G. Gürek, C.
Hirel, M. Durmuş, J.-B. Tommasino, D. Luneau, S. Berber, F.
Dumoulin and V. Ahsen, Dalton Trans., 2014, 43, 6897; c) M.
Machacek, A. Cidlina, V. Novakova, J. Svec, E. Rudolf, M. Miletin,
R. Kucera, T.Simunek and P. Zimcik, J. Med. Chem., 2015, DOI:
10.1021/jm5014852; d) K. Sakamoto, E. Ohno-Okumura, T. Kato
and H. Soga, J. Porphyrins Phthalocyanines, 2010, 14, 47.
A. W. Snow, Phthalocyanine Aggregation, in The Porphyrin
Handbook, eds. K. M. Kadish, K. M. Smith and R. Guilard,
Academic Press, New York, NY, 2003, vol. 17, pp. 129-176.
D. Wöhrle, M. Eskes, K. Shigehara, A. Yamada, Synthesis, 1993,
194; b) U. Kumru, F. Dumoulin, E. Jeanneau, F. Yuksel, Y.Cabezas,
Y. Zorlu and V. Ahsen, Struct. Chem., 2012, 23, 175.
I. Chambrier, M. J. Cook, M. Helliwell and A. K. Powell, Chem.
Commun., 1992, 444.
M. P. Donzello, C. Ercolani, A. A. Gaberkorn, E. V. Kudrik, M.
Meneghetti, G. Marcolongo, C. Rizzoli and P. A. Stuzhin, Chem.-
Eur. J., 2003, 9, 4009.
Fig. 4 a) Channels with different size and b) Perspective view of the 3-D
channel voids encapsulated by phthalocyanine units in the unite cell.
3
5
1
1
1
00
05
10
7
8
To conclude, these two molecules are the first example of a
comparison between a planar and a distorted phthalocyanine
derivative with the same substitution pattern, as both compounds
carry alkylsulfanyl substituents. This allows to attribute the
observed shift in UV-vis absorption to the macrocycle distortion.
More derivatives with substituents of other sizes and bulkiness
are being synthesized. We plan as well to investigate the effect of
metalation of the phthalocyanine core. Besides, the distorted tert-
4
0
9
1
0
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

ChemComm
Page 4 of 4
1
1
1
2
M. J. Cook, J. McMurdo and A. K. Powell Chem. Commun., 1993,
03.
A. N. Cammidge, C. H. Tseng, I. Chambrier, D. L. Hughesand M. J.
9
View Article Online
DOI: 10.1039/C5CC01085C
Cook, Tetrahedron Lett., 2009, 50, 5254.
5
0
5
0
5
0
13 N. Kobayashi, T. Fukuda, K. Ueno and H. Ogino, J. Am. Chem. Soc.,
001, 123, 10740.
Y. Gao, Y. Chen, R. Li, Y. Bian, X. Li and J. Jiang, Chem.-Eur. J.,
009, 15, 13241
2
14
15
16
17
2
J. D. Wang, J. L. Huang, J. W. Cai and N. S. Chen, Chin. J. Struct.
Chem., 2002, 21, 617.
S. M. Gorun, J. W. Rathke and M. J. Chen, Dalton Trans., 2009,
1
1
2
2
3
1
095.
(a) N. Kobayashi, T. Furuyama and K. Satoh, J. Am. Chem. Soc.,
011, 133, 19642; (b) T. Furuyama, K. Satoh, T. Kushiya and N.
2
Kobayashi, J. Am. Chem. Soc., 2014, 136, 765.
1
1
8
a) K. Hanson, L. Roskop, P. I. Djurovich, F. Zahariev, M. S. Gordon
and M. E. Thompson, J. Am. Chem. Soc., 2010, 132, 16247; b) L. X.
Chen, W. J. H. Jager, M. P. Niemczyk and M. R. Wasielewski, J.
Phys. Chem. A, 1999, 103, 4341; c) S. Duman, Y. Cakmak, S.
Kolemen, E. U. Akkaya and Y. Dede, J. Org. Chem. 2012, 77, 4516.
9 A. L., Spek, J. App. Cryst., 2003, 32, 7. Analysis of Solvent
Accessible Voids in the Structure was performed using the CALC
SOLV within the PLATON software package with a probe radius of
1
.20 Å and grid spacing of 0.2 Å. Van der Waals (or ion) Radii used
in the analysis are C (1.70 Å), H (1.20 Å), N (1.55 Å), S (1.80 Å),
respectively.
2
0 a) N. B. McKeown, S. Makhseed, K. J. Msayib, L. L. Ooi, M.
Helliwell and J. E. Warren, Angew. Chem., Int. Ed., 2005, 44, 7446;
b) C. G. Bezzu, M. Helliwell, J. E. Warren, D. R. Allan and N. B.
McKeown, Science, 2010, 327, 1627.
4
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]