form. The IR spectrum showed strong bands at 3425 and 1693
2
1
cm which can be ascribed to the O–H and CNO stretches of
the oxalic acid, respectively. These bands were not observed in
the IR spectrum of the green powder of 3, showing that oxalic
acid is not present in this batch of sample. It has been found that
in the presence of some lanthanide complexes, oxalate anion
1
3
can be produced by reductive coupling of carbon dioxide. We
suggest that a small amount of oxalic acid is generated similarly
in this cerium-promoted cyclisation reaction. The guest mole-
cules co-crystallise with a small portion of 3 forming the green
transparent plates, while the major portion in green solid form is
free from oxalic acid. Attempts to recrystallise this sample by
3
the layering method (CHCl /MeOH) always led to precipita-
tion. However, by the addition of one equiv. of oxalic acid in the
MeOH layer, a substantial amount of green plates were obtained
for which the IR spectrum and the X-ray structure were found to
2 2 4
be identical with those of 3·C H O .
In summary, we have reported a new cerium-promoted
method to prepare the metal-free phthalocyanine 3, which forms
a novel 1+1 inclusion complex with oxalic acid generated
serendipitously in the reaction.
We thank The Chinese University of Hong Kong and the
Hong Kong Research Grants Council for support.
Notes and references
1
2
Phthalocyanines–Properties and Applications, ed. C. C. Leznoff and A.
B. P. Lever, VCH, New York, 1989, vol. 1; 1993, vols. 2 and 3; 1996,
vol. 4; N. B. McKeown, Phthalocyanine Materials: Synthesis, Structure
and Function, Cambridge University Press, Cambridge, 1998.
See, for example: C. F. van Nostrum and R. J. M. Nolte, Chem.
Commun., 1996, 2385; R. D. Gould, Coord. Chem. Rev., 1996, 156, 237;
A. Yamashita and T. Hayashi, Adv. Mater., 1996, 8, 791; P. Smolenyak,
R. Peterson, K. Nebesny, M. Törker, D. F. O’Brien and N. R.
Armstrong, J. Am. Chem. Soc., 1999, 121, 8628; M. Matsuda, T. Naito,
T. Inabe, N. Hanasaki and H. Tajima, J. Mater. Chem., 2001, 11,
2 2 4
Fig. 2 Crystal structure of 3·C H O : (a) view along the a axis, (b) view
along the b axis. All hydrogen atoms are omitted for clarity.
stituents, which act as the spacers. The crystal structure of 3,
however, is significantly different from those of
1
,4,8,11,15,18,22,25-octasubstituted phthalocyanines H
2
PcR
8
11
(
R = n-C H13, iso-OC H11), which adopt a brickstone
6 5
3
2
493.
arrangement in which the inter-ring spacing within a stack is
slightly larger (ca. 8.5 Å).
3
4
M. K. Engel, Kawamura Rikagaku Kenkyusho Hokoku, 1996, 8, 11;
Chem. Abstr., 1997, 127, 313213t.
A. Fujita, H. Hasegawa, T. Naito and T. Inabe, J. Porphyrins
Phthalocyanines, 1999, 3, 720; N. Matsumura, A. Fujita, T. Naito and
T. Inabe, J. Mater. Chem., 2000, 10, 2266; T. Inabe, J. Porphyrins
Phthalocyanines, 2001, 5, 3.
The most remarkable feature of the crystal structure is the
presence of oxalic acid molecules intercalated between the
phthalocyanine rings (Fig. 3). On the basis of the separation
between the phthalocyanine core and the oxalic acid molecule,
it seems that hydrogen bonding is not significant between these
species. The inclusion phenomenon may be simply due to the
polar nature of oxalic acid, which preferentially resides in the
more polar cavity between the phthalocyanine rings rather than
5 J. W. Buchler and D. K. P. Ng, in The Porphyrin Handbook, ed. K. M.
Kadish, K. M. Smith and R. Guilard, Academic Press, San Diego, CA,
2
000, vol. 3, ch. 20; D. K. P. Ng, J. Jiang, K. Kasuga and K. Machida,
in Handbook on the Physics and Chemistry of Rare Earths, ed. K. A.
Gschneidner, Jr., L. Eyring and G. H. Lander, Elsevier, Amsterdam,
3
in bulk CHCl .
2
001, vol. 32, ch. 210.
H. Wolleb, Eur. Pat. Appl., EP 703 280, 1996; Chem. Abstr., 1996, 124,
92301r.
The presence of oxalic acid in the crystal lattice was
6
7
corroborated with the analytical1 and IR data of 3 in a crystal
2
2
Cyclisation of 3- or 4-substituted phthalonitriles normally gives
tetrasubstituted phthalocyanines as a mixture of four constitutional
s
isomers which have C4h, D2h, C2v or C symmetry, respectively. The
ratio of these four isomers depends on the position and bulkiness of the
substituent. See: C. Rager, G. Schmid and M. Hanack, Chem. Eur. J.,
1
999, 5, 280.
8
9
D. S. Terekhov, K. J. M. Nolan, C. R. McArthur and C. C. Leznoff, J.
Org. Chem., 1996, 61, 3034.
Crystallographic data for 3·C
monoclinic, space group P2 /c (no. 14), with a = 15.8962(15), b =
.8141(9), c = 21.695(2) Å, b = 99.911(2)°, V = 2994.4(5) Å , and D
2 2 4 76 8 8 w
H O : C62H N O , M = 1061.31,
1
3
8
=
c
23
1.177 g cm for Z = 2. The structure was solved by direct methods
and refined by a full-matrix least-squares procedure using 4160 data to
a conventional R value of 0.0680 (R = 0.1988). CCDC reference
w
number 175743. See http://www.rsc.org/suppdata/cc/b1/b111133g/ for
crystallographic data in CIF or other electronic format.
1
1
0 S. Matsumoto, K. Matsuhama and J. Mizuguchi, Acta Crystallogr., Sect.
C, 1999, 55, 131.
1 I. Chambrier, M. J. Cook, M. Helliwell and A. K. Powell, J. Chem. Soc.,
Chem. Commun., 1992, 444; M. J. Cook, J. McMurdo and A. K. Powell,
J. Chem. Soc., Chem. Commun., 1993, 903.
1
76 8 8 2 2 4
2 Anal. Calc. for C62H N O (3·C H O ): C, 70.16; H, 7.22; N,10.56.
Found: C, 69.99; H, 7.29; N, 10.54%.
1
3 W. J. Evans, C. A. Seibel and J. W. Ziller, Inorg. Chem., 1998, 37, 770;
W.-K. Wong, L.-L. Zhang, F. Xue and T. C. W. Mak, J. Chem. Soc.,
Dalton Trans., 2000, 2245.
2 2 4
Fig. 3 Packing of 3·C H O : view nearly parallel to the phthalocyanine
planes. All hydrogen atoms are omitted for clarity.
CHEM. COMMUN., 2002, 628–629
629