Extremely non-planar phthalocyanines with saddle or helical conformation: Synthesis and structural characterizations [2]

Full text of DOI:10.1021/ja0113753

10740
J. Am. Chem. Soc. 2001, 123, 10740-10741
Extremely Non-Planar Phthalocyanines with Saddle
or Helical Conformation: Synthesis and Structural
Characterizations
Nagao Kobayashi,* Takamitsu Fukuda, Keiji Ueno, and
Hiroshi Ogino
Department of Chemistry, Graduate School of Science
Tohoku UniVersity, Sendai 980-8578, Japan
ReceiVed June 5, 2001
Most of the applications of phthalocyanines (Pcs) are concerned
with the large, flat π-conjugation system, as well as the type of
central metal.1 In particular, it is well-known that, compared with
porphyrins,2 the metalloPcs (MtPcs) have extremely high planar-
ity: for example, nonsubstituted NiPc is essentially perfectly
planar,3 although MtPcs with larger metal ions such as Pb and
Sn distort the geometry to some extent.4 Structurally distorted
Pcs have been reported in the past few years, where the steric
congestion of substituents caused distortion of the macrocycle.4,5
In this communication, we report two types of Pc analogues whose
nonplanarity appears to be the highest yet reported. To induce
the largest distortion conceivable, aromatic ortho-dinitriles having
two protruding phenyl groups, 3 and 4, are used. These types of
dinitriles have long been believed to be too congested to form
Pcs by themselves6 and have therefore been employed for the
preparation of opposite type of MtPc analogues, utilyzing the
steric hindrance between the phenyl groups.7 In the course of
studies, however, we thought that, if these dinitriles can occupy
the adjacent positions of Pcs, the deviation from planarity would
be very large because of the overlap of the protruding phenyl
groups.8 As described below, we have overcome this problem,
and the resultant two Pc analogues obtained by the above inverse
concept, 1 and 2, are indeed confirmed to be the most nonplanar
Pcs ever substantiated structurally.
Figure 1. View of the molecular structure of 1: (a) top view and (b)
side view. Displacement ellipsoids are shown at the 50% probability level.
Hydrogen (in both (a) and (b)) and phenyl groups (in (b)) are omitted
for clarify.
Scheme 1
Both 19 and 210 were prepared by the so-called lithium method1
at ca. 170 and 150 °C, respectively (Scheme 1). In the case of 2,
dinitriles 4 and 5 were co-macrocyclized, so that repeated
(1) (a) Phthalocyanines-Properties and Applications; Leznoff, C. C., Lever,
A. B. P., Eds.; VCH: Weinheim, Germany, 1989, 1993, 1993, and 1996;
Vols. I-IV. (b) Shirai, H., Kobayashi, N., Eds.; Phthalocyanines-Chemistry
and Functions; IPC: Tokyo, 1997.
(2) Senge, M. O. In The Porphyrin Handbook; Kadish, K. M., Smith, K.
M., Guilard, R. Eds.; Academic Press: 2000; Vol. 1, Chapter 6 and references
therein.
(3) Robertson, J. M. J. Chem. Soc. 1937, 219.
(4) Engel, M. K. Rep. Kawamura Inst. Chem. Res. (English) 1997, 11;
Chem. Abs. 1997, 127, 313213.
chromatography was inevitably required. They were characterized
1
using mass spectra, elemental analysis, and H NMR (only for
1)9,10 and their molecular structures were analyzed by X-ray
crystallography. Crystals were grown in either chloroform-hexane
(1) or acetone-containing toluene (2).
Figures 1 and 2 show ORTEP drawings of 111 and 2,12
respectively. As expected, the steric hindrance arising from the
substituted phenyl groups appears quite significant in deforming
the Pc skeleton. For 1, the most significant structural characteristic
is an alternating up-and-down displacement of the individual
isoindole units from the mean plane generated by the four pyrrole
nitrogens (4N-plane). This type of structure has been termed a
saddle conformation.2 Figure 3 (top) shows the skeletal deviation
(5) Chambrier, I.; Cook, M. J.; Wood, P. T. Chem. Commun. 2000, 2133.
(6) (a) Mikhalenko, S. A.; Gladyr’, S. A.; Luk’yanets, E. A. Zh. Org. Khim.
1972, 8, 341; J. Org. Chem. URRS (Engl. Transl.), 1972, 8, 341. (b) Sugimori,
T.; Okamoto, S.; Kotoh, N.; Handa, M.; Kasuga, K. Chem. Lett. 2000, 1200.
(7) (a) Kobayashi, N.; Ashida, T.; Osa, T.; Konami, H. Inorg. Chem. 1994,
33, 1735. (b) Kobayashi, N.; Ashida, T.; Osa, T. Chem. Lett. 1992, 2031. (c)
Nemykin, V. N.; Subbotin, N. B.; Kostromina, N. A.; Volkov, S. V. MendeleeV
Commun. 1995, 71. (d) Yang, J.; Van De Mark, M. R. J. Heterocycl. Chem.
1995, 32, 1521.
(8) Nemykin, V. N.; Kobayashi, N.; Nonomura, T.; Luk’yanets, E. A. Chem.
Lett. 2000, 184.
(9) Synthetic procedure and some spectroscopic data for 1: Lithium (100
mg, 15 mmol) was heated at 100 °C in 1-hexanol (5 mL) until all of the
metal was dissolved. After cooling to room temperature, diphenylphthalonitrile
(1 g, 3.6 mmol) was added and reacted for 1 h at 170 °C. Most of the solvent
was boiled off, DMF (5 mL) was added, and the mixture was poured into
200 mL of water. The precipitated solid was filtered off, washed with water
and methanol, and dried under reduced pressure. The crude products were
further purified using column chromatography (silica, toluene-cyclohexane
(1:1 v/v)) to give 40 mg (4.0%) of 1 (Rf ) 0.7) as a yellowish green solid.
FAB mass (m/z): 1123 (M+ + 1). Anal. Calcd for C80H50N8: C, 85.54; H,
(10) Synthetic procedure and some spectroscopic data for 2: Lithium (100
mg, 15 mmol) was heated at 100 °C in 1-hexanol (5 mL) until all of the
metal was dissolved. After cooling to room temperature, diphenylmaleonitrile
(180 mg, 0.78 mmol) and 2,3-dicyano-1,4-diphenylanthracene (250 mg, 0.66
mmol) were added and reacted for 1 h at 150 °C. Most of the solvent was
boiled off. DMF (30 mL) and CoCl2 (1.4 g, 11 mmol) were added and
maintained at 150 °C for 30 min. The mixture was poured into 200 mL of
water, and the resultant solid filtered off, washed with water and methanol,
and dried. The residue was purified using preparative TLC (silica, toluene),
to give 40 mg (9.5% on the basis of the dicyano-diphenylanthracene) of 2 (Rf
) 0.83) as a green solid. FAB mass (m/z): 1280 (M++ 1). Anal. Found: C,
81.98; H, 4.33; N, 8.65. Calcd for C88H52N8Co: C, 82.55; H, 4.09; N, 8.75.
UV-vis (toluene, λ, nm (lg ꢀ)): 748 (5.89), 669sh (5.49), 490 (5.17), 425sh
(5.43), and 355 (5.89). Another green band was recognized at Rf ) 0.68, and
this portion was identified as monoanthracene-fused TAP (16 mg, 5.4% based
on diphenylmaleonitrile).
1
4.49; N, 9.98. Found: C, 85.50; H, 4.74; N, 9.80. H NMR (toluene-d8, 400
MHz at 0 °C): δ 7.47 (s, 8H, Pc), 7.45 (d, 16H, phenyl o-H), 7.18 (t, 8H,
phenyl p-H), 7.10 (dd, 16H, phenyl m-H), 2.02 (-60 °C) to 2.12 (100 °C) (s,
2H, NH) (at 0 °C, NH signal is not detectable hidden by CH3 signal of the
solvent). UV-vis (CHCl3, λ, nm (lg ꢀ)): 788 (4.96), 699sh (4.37), 414sh
(4.39), 336 (4.58), and 281sh (4.91).
10.1021/ja0113753 CCC: $20.00 © 2001 American Chemical Society
Published on Web 10/03/2001

Communications to the Editor
J. Am. Chem. Soc., Vol. 123, No. 43, 2001 10741
the isoindole units on either side of the core reach 46.0 and 41.9°
(43.9° on average), which are well above the recently reported
value for 1,4,8,11,15,18,22,25-octaisopentyl Pc by Cook et al.
(32.0°)5 and is unambiguously the largest deformation seen in
the Pc derivatives known to date. As seen in Figure 1, the
deformation seems to originate mainly from twisting around the
meso-N atoms, that is each isoindole unit retains a relatively high
planarity (see Supporting Information) and the twisting among
isoindole units dominates the total molecular structure. On the
other hand, despite being a nonplanar macrocycle, the bond
lengths in 1 are close to those found in nonsubstituted planar H2-
Pc.13 For example, bond lengths of N1-C1, N8-C1, C4-C27,
and C63-C68 are 1.372(4), 1.331(4), 1.480(5), and 1.419(4) Å,
respectively, while the corresponding bond lengths in H2Pc are
1.34, 1.33, 1.49, and 1.39 Å, respectively.13
The ORTEP drawing in Figure 2 clearly illustrates that
compound 212 is a tetraazaporphyrin (TAP) adjacently fused by
two anthracene rings. Similarly to 1, 2 is conformationally highly
stressed due to the peripherally substituted phenyl groups, and
therefore the whole molecule adopts a kind of helical structure.
In other words, the structure of 2 is similar to helicene, although
no significant vertical overlap between π orbitals is conceivable.
As far as we know, this is the first realization of a helical structure
using low symmetrical Pcs or porphyrins. The dihedral angle
between the neighboring planes formed by the two adjacent
isoindole units (i.e., outer naphthalene rings have been ignored
to compare the two compounds) is 40.5°. On the other hand, the
values in 1 are 29.6, 30.1, 31.3, and 32.0° (30.7° on average),
which is, interestingly, much smaller than those in 2. It is
intuitively anticipated that central metals whose sizes fit into the
Pc cavity (such as cobalt, nickel, etc.) reduce the skeletal
deformation. Accordingly, these experimental results, which are
wholly contrary to our expectations, might be considered to result
from the low symmetrical π-conjugation system of 2. Since the
two anthracene units are such large substituents on the TAP
skeleton, the interaction of these two units primarily determines
the whole molecular structure, dominating the ring-planarizing
effect of the metal. Figure 3 (bottom) shows that the skeletal
deformation is particularly marked for the pyrroles fused to
anthracene rings (ca. 0.5-0.8 Å) and the deviations of the other
pyrroles are somewhat smaller (ca. 0.2-0.6 Å), emphasizing the
helical structure of 2 (Figure 2b).
In summary, we have prepared two novel, structurally highly
deformed Pc derivatives and determined that they adopt either
saddle or helical conformations depending on the geometry of
the π-conjugation system. They have been identified to have the
most deformed macrocyclic core in the Pcs and TAPs thus far
determined in the solid state. In particular, 2 is the first helicene-
like compound found in the porphyrin and Pc family. Compared
with normal flat Pcs and TAPs without substituents, the bond
lengths are virtually unchanged. Hence, the structural deformation
appears to originate primarily from strain of the bond angles.
Although we used 3,6-dipenylphthalonitrile and zinc ion to obtain
oppositely substituted Pcs in our previous papers,7a,b the use of a
stonger template, that is lithium ion, made it possible to prepare
sterically crowded 1 and 2. Detailed spectroscopic and electro-
chemical properties of 1, 2 will be reported in due course.
Figure 2. View of the molecular structure of 2: (a) top view and (b)
side view. Displacement ellipsoids are shown at the 50% probability level.
Hydrogen (in both (a) and (b)) and phenyl groups (in (b)) are omitted
for clarify.
Figure 3. Linear display of the out-of-4N-plane deviations from planarity
for the core atoms of 1 (top) and 2 (bottom). Squares indicate the carbon
atoms fused to anthracene rings.
of the central 20-membered macrocyclic atoms of 1 from the 4N-
plane. The observed maximum deviation is ca. 1.03 Å, which is
the largest observed thus far for Pcs, and even compares with
those of the representative highly disordered porphyrins (ca. 0.7-
1.4 Å),2 even though Pcs, unlike porphyrins, cannot have bulky
substituents structurally at their meso-positions which are impor-
tant in deforming the π-conjugation plane. The degree of deviation
of the other pyrrole units is approximately in the same order (ca.
1 Å). The dihedral angles between the pair of planes formed by
(11) Crystallographic data for 1: single crystals of 1 containing CHCl3 and
hexane were obtained by recrystallization from a CHCl3/hexane solution.
C82.51H55.11N8Cl1.68, triclinic, space group P-1h(No. 2), with unit-cell dimensions
a ) 15.5258(5) Å, b ) 15.8918(7) Å, c ) 16.4589(2) Å, R ) 87.287(2)°, â
) 67.873(2)°, γ ) 61.084(3)°, V ) 3247.1(2) Å3, Z ) 2, Dcalc ) 1.246 g/cm3.
Intensity data were collected at 150 K on a Rigaku RAXIS-RAPID Imaging
Plate diffractmeter with graphite monochromated Mo KR radiation. The
structure was solved by direct methods and expanded using Fourier techniques;
25149 reflections were measured in which 13169 were independent. Final R1
) 0.094, Rw ) 0.219 (I > 2.0 σ(I)). Full details are described in the Supporting
Information.
Acknowledgment. This research was supported by a Grant-in-Aid
for Scientific Research (B) No. 11440192 from the Ministry of Education,
Science, Sports, and Culture, Japan, and the Shorai Foundation for Science
and Technology. T.F. thanks JSPS for financial support (Grant No.
13008393).
(12) Crystallographic data for 2: C105H92N8CoO6, monoclinic, space group
C2/c (No. 15), with unit-cell dimensions a ) 31.460(9) Å, b ) 20.602(4) Å,
c ) 28.041(3) Å, â ) 115.608(1), V ) 16389(5) Å3, Z ) 8, Dcalc ) 1.314
g/cm3. Intensity data were collected at 150 K on a Rigaku/MSC Mercury
diffractometer with graphite monochromated Mo KR radiation. The structure
was solved by direct methods and expanded using Fourier techniques. A total
of 49418 reflections were measured in which 16857 were independent. Final
R1 ) 0.086, Rw ) 0.097 (I > 2.0 σ(I)). Full details are described in the
Supporting Information.
Supporting Information Available: X-ray data for 1 and 2 (CIF
and PDF). This material is available free of charge via the Internet at
http://pubs.acs.org.
JA0113753
(13) Robertson, J. M. J. Chem. Soc. 1936, 1195.