Adjacent versus opposite type di-aromatic ring-fused phthalocyanine derivatives: Synthesis, spectroscopy, electrochemistry, and molecular orbital calculations

Article abstract of DOI:10.1021/ja0123812

A series of adjacent and opposite type di-aromatic ring-fused phthalocyanines (Pc's) of varying size have been prepared and characterized spectroscopically and electrochemically, and most of their properties have been reasonably reproduced by molecular orbital (MO) calculations. The adjacent isomers alone were obtained preferentially by using a diphthalonitrile unit linked via a short aryl chain. The main results are summarized as follows. (i) The Q-band shifts to longer wavelength and its intensity increases, but the degree of change decreases, with increasing molecular size. On the bases of the experiments and MO calculations, setting the size of the effect of benzene directly fused to the tetraazaporphyrin (TAP) skeleton at unity, the effect of the second and third benzene units is roughly about 0.75-0.80 and 0.48 ± 0.06, respectively. As a result of this, among compounds having an isomeric π-system, the Q-band of a D_4h type species lies at longer wavelength than those of adjacently and oppositely di-aromatic ring-fused species. (ii) The Q-band of adjacently substituted species does not split appreciably, while that of the oppositely substituted species splits substantially, the extent having a parallel relationship with the ratio of long to short axes in the molecule. In general, the larger the ratio, the larger the splitting. (iii) The Q-band of oppositely dibenzo-fused and bis(dialkyl)-substituted TAP does not show explicit splitting because of the large coefficients of the carbons substituted with alkyl groups in the MOs. (iv) Interestingly, the first oxidation in adjacently and oppositely dibenzo-fused CoTAP occurs at the cobalt and ligand, respectively, although they are isomers to each other.

Full text of DOI:10.1021/ja0123812

Published on Web 06/14/2002
Adjacent versus Opposite Type Di-Aromatic Ring-Fused
Phthalocyanine Derivatives: Synthesis, Spectroscopy,
Electrochemistry, and Molecular Orbital Calculations
Nagao Kobayashi,* Hideya Miwa, and Victor N. Nemykin
Contribution from the Department of Chemistry, Graduate School of Science, Tohoku UniVersity,
Sendai 980-8578, Japan
Received October 17, 2001
Abstract: A series of adjacent and opposite type di-aromatic ring-fused phthalocyanines (Pc’s) of varying
size have been prepared and characterized spectroscopically and electrochemically, and most of their
properties have been reasonably reproduced by molecular orbital (MO) calculations. The adjacent isomers
alone were obtained preferentially by using a diphthalonitrile unit linked via a short aryl chain. The main
results are summarized as follows. (i) The Q-band shifts to longer wavelength and its intensity increases,
but the degree of change decreases, with increasing molecular size. On the bases of the experiments and
MO calculations, setting the size of the effect of benzene directly fused to the tetraazaporphyrin (TAP)
skeleton at unity, the effect of the second and third benzene units is roughly about 0.75-0.80 and 0.48 (
0.06, respectively. As a result of this, among compounds having an isomeric π-system, the Q-band of a
D4h type species lies at longer wavelength than those of adjacently and oppositely di-aromatic ring-fused
species. (ii) The Q-band of adjacently substituted species does not split appreciably, while that of the
oppositely substituted species splits substantially, the extent having a parallel relationship with the ratio of
long to short axes in the molecule. In general, the larger the ratio, the larger the splitting. (iii) The Q-band
of oppositely dibenzo-fused and bis(dialkyl)-substituted TAP does not show explicit splitting because of
the large coefficients of the carbons substituted with alkyl groups in the MOs. (iv) Interestingly, the first
oxidation in adjacently and oppositely dibenzo-fused CoTAP occurs at the cobalt and ligand, respectively,
although they are isomers to each other.
Introduction
symmetrical Pc’s are more suitable for several purposes than
low symmetrical porphyrins. For example, the Q-band transition
In the past decade, research on low symmetrical phthalocya-
nines (Pc’s) has been popular among Pc chemists.1-3 Low
in the visible region has much more allowed character than that
in porphyrins;4 therefore, adjustment of the color is easier. In
addition, the correspondence between experiments and quantum
chemical calculations is also generally better, since the HOMO-
LUMO transition is essentially explained by a one-electron
description.5 Monosubstituted type low symmetrical Pc deriva-
tives have been prepared either by mixed condensation reac-
tion,6,7 polymer support method,8 or ring-expansion reaction of
subphthalocyanines.9 Disubstituted analogues have so far been
obtained only by mixed condensation of two kinds of aromatic
ortho dinitriles or isoindolediimines, which gave mixtures of
products, and subsequent tedious purification by column
(1) PhthalocyaninessProperties and Applications; Leznoff, C. C., Lever, A.
B. P., Eds.; VCH Publishers: New York, 1989 (Vol. 1), 1992 (Vol. 2),
1993 (Vol. 3), and 1996 (Vol. 4).
(2) Kobayashi, N. In ref 1, Vol. 1, Chapter 3.
(3) Some representative ones: (a) Kobayashi, N.; Ashida, T.; Osa, T. Chem.
Lett. 1992, 1567, 2031. (b) Konami, H.; Ikeda, Y.; Hatano, M.; Mochiziki,
K. Mol. Phys. 1993, 80, 153. (c) Kobayashi, N.; Ashida, T.; Osa, T.;
Konami, H. Inorg. Chem. 1994, 33, 1735. (d) Baumann, T. F.; Sibert, J.
W.; Olmstead, M. M.; Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem.
Soc. 1994, 116, 2639. (e) Nemykin, V. N.; Subbotin, N. B.; Kostromina,
N. A.; Volkov, S. V.; Luk’yanets, E. A. Russ. J. Inorg. Chem. 1995, 40,
1141. (f) Kobayashi, N.; Togashi, M.; Osa, T.; Ishii, K.; Yamauchi, S.;
Hino, H. J. Am. Chem. Soc. 1996, 118, 1073. (g) Baumann, T. F.; Nasier,
M. S.; Sibert, J. W.; White, A. J. P.; Olmstead, M. M.; Williams, D. J.;
Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1996, 118, 10479.
(h) Humberstone, P.; Clarkson, G. J.; McKeown, N. B.; Treacher, K. E. J.
Mater. Chem. 1996, 6, 315. (i) Leznoff, C. C.; Drew, D. M. Can. J. Chem.
1996, 74, 307. (j) Nolan, K. J. M.; Hu, M.; Leznoff, C. C. Synlett 1997,
593. (k) Cook, M. J.; Jafari-Fini, A. J. Mater. Chem. 1997, 7, 5. (l) Dabak,
S.; Bekaroglu, O. J. Chem. Res. 1997, 8. (m) Aoudia, M.; Cheng, G.;
Kennedy, V. O.; Kenney, M. E.; Rodgers, M. A. J. J. Am. Chem. Soc.
1997, 119, 6029. (n) Rodriguez-Morgade, S.; Hanack, M. Chem. Eur. J.
1997, 3, 1042. (o) Forsyth, T. P.; Williams, D. B. G.; Montalban, A. G.;
Stern, C. L.; Barrett, A. G. M.; Hoffman, B. M. J. Org. Chem. 1998, 63,
331. (p) Maya, E. M.; Vazquez, P.; Torres, T. Chem. Eur. J. 1999, 7, 2004.
(q) Kobayashi, N.; Miwa, H.; Isago, H.; Tomura, T. Inorg. Chem. 1999,
38, 479. (r) Miwa, H.; Kobayashi, N. Chem. Lett. 1999, 1303. (s) Cabezon,
B. C.; Nicolau, M.; Barbera, J.; Torres, T. Chem. Mater. 2000, 12, 776. (t)
Cabezon, B.; Quesada, E.; Esperanza, S.; Torres, T. Eur. J. Org. Chem.
2000, 2767. (u) De la Torre, G.; Claessens, C. G.; Torres, T. Eur. J. Org.
Chem. 2000, 2821.
(4) Gouterman, M. In The Porphyrins; Dolphin, D., Ed.; Academic Press: New
York, 1978; Vol. 3, Chapter 1.
(5) Kobayashi, N.; Konami, H. In ref 1, Vol. 4, Chapter 9.
(6) Leznoff, C. C. In ref 1, Vol. 1, Chapter 1.
(7) Piechocki, C.; Simon, J. J. Chem. Soc., Chem. Commun. 1985, 259.
(8) (a) Leznoff, C. C.; Hall, T. W. Tetrahedron Lett. 1982, 23, 3023. (b) Hall,
T. W.; Greenberg, S.; McArthur, C. R.; Khouw, B.; Leznoff, C. C. NouV.
J. Chim. 1982, 6, 653. (c) Wohrle, D.; Krawczyk, G. Polym. Bull. 1986,
15, 193. (d) Leznoff, C. C.; Svirskaya, P. I.; Khouw, B.; Cerny, R. L.;
Seymour, P.; Lever, A. B. P. J. Org. Chem. 1991, 56, 82.
(9) (a) Kobayashi, N.; Kondo, R.; Nakajima, S.; Osa, T. J. Am. Chem. Soc.
1990, 112, 9640. (b) Kobayashi, N.; Ishizaki, T.; Ishii, K.; Konami, H. J.
Am. Chem. Soc. 1999, 121, 9096. (c) Kobayashi, N. J. Porphyrins
Phthalocyanines 1999, 3, 453. (d) Sastre, A.; Del Rey, B.; Torres, T. J.
Org. Chem. 1996, 61, 8591.
9
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J. AM. CHEM. SOC. 2002, 124, 8007-8020
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A R T I C L E S
Kobayashi et al.
chromatography.3a,c,e,g,m,n However, the separation and identi-
fication of adjacently (C2V type) and oppositely substituted (D2h
type) Pc’s are generally particularly difficult, since their
molecular weights are identical. To date, adjacent and opposite
dibenzo-substituted Pc’s have been prepared and compared,3b,m,n
but no one has prepared and characterized a series of adjacently
and oppositely substituted Pc’s of varying size. In the work
described in this paper, we have prepared these types of cobalt
Pc derivative and compared their spectroscopic and electro-
chemical properties (Figure 1). Some of the experimental results
are interpreted using the results of molecular orbital (MO)
calculations. As will be shown below, adjacently and oppositely
di-aromatic ring-fused Pc analogues have indeed strikingly
contrasting spectroscopic properties. In a few cases, the
experimentally obtained characteristics were different from those
expected theoretically. However, reasonable interpretations have
been eventually given.
Because of the solubility problem and the academic interest,
a series of cobalt complexes were prepared. Zinc and nickel
complexes are desirable from the standpoint of structural
analysis, since NMR spectroscopy is available. However,
naphthalene- and anthracene-fused zinc complexes decomposed
during column chromatography, while the low yield and low
solubility of anthracene-fused nickel complex prevented us from
preparing a series of nickel complexes. Cobalt complexes alone
had solubility and stability enough for characterization. Ac-
cordingly, cobalt was chosen as a central metal atom.
Experimental Section
1
(i) Measurements. The 400 MHz H NMR spectral measurements
were made with a JEOL GSX-400 instrument. Mass spectra were
measured with a Perspective Biosystem MALDI-TOF Mass Voyager
DE-SI2 spectrometer using dithranol (1,8,9-anthracenetriol) as a matrix,
with a JEOL JMS-HX110 mass spectrometer (FAB mass) using
m-nitrobenzyl alcohol (NBA) as a matrix and with a Micromass LCT
(ESI-TOF mass) using chloroform and methanol as solvents. Electronic
absorption spectra were measured with a Hitachi U-3410 spectropho-
tometer. Magnetic circular dichroism (MCD) spectra were run on a
Jasco J-725 spectrodichrometer using toluene (Nacalai Tesque, for
adjacent species) or o-dichlorobenzene (o-DCB) (Nacalai Tesque, HPLC
grade, for opposite species) solutions of ca. 10-5-10-6 mol/L because
of the solubility problem and in an attempt to obtain nonaggregated
spectra, with a Jasco electromagnet that produces magnetic fields of
up to 1.09 T. The magnitude was expressed in terms of molar ellipticity
per tesla, [θ]M/104 deg mol-1 cm-3 cm-1 T-1
.
Cyclic voltammetry data were collected with a Hokuto Denko HA-
501 potentiostat connected to a Graphtec WX1200 XY recorder.
Differential pulse voltammetry data were recorded with a Yanaco
P-1100 polarographic analyzer connected to a Watanabe WX 4401 XY
recorder. Electrochemical experiments were performed under purified
nitrogen gas. A glassy carbon working electrode (area ) 0.07 cm2)
and a Pt wire counter electrode were employed. The reference electrode
was Ag/AgCl, corrected for junction potentials by referencing internally
to the Fc+/Fc couple. In the solution used, i.e., in o-DCB (Nacalai
Tesque, HPLC grade) containing 0.1 mol/L tetrabutylammonium
perchlorate (TBAP), the Fc+/Fc couple was observed at approximately
0.51 ( 0.02 V vs Ag/AgCl. For spectroelectrochemical measurements,
an optically transparent thin-layer electrode (OTTLE) cell of path length
1 mm was employed using a Pt minigrid as both the working and
counter electrodes, respectively,10 and a TBAP concentration of 0.3
mol/L.
Figure 1. Structures and abbreviations of the compounds in this study,
and the directions of x- and y-axes in each compounds. “Ad” and “Op”
mean “adjacent” and “opposite”, respectively, and the numbers at the end
indicate the number of benzene units fused to the tetraazaporphyrin (TAP)
skeleton.
Crystal structural analysis of an oppositely substituted compound
was performed on a Rigaku/MSC Mercury difractometer with graphite-
monochromated Mo KR radiation (λ ) 0.7107 Å). All calculations
were performed using the teXsan crystallographic software package11
on a Silicon Graphics O2 computer.
(10) Kobayashi, N.; Nishiyama, Y. J. Phys. Chem. 1985, 89, 1167.
9
8008 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
Scheme 1. Synthesis of Adjacent Type Species
as previously reported. 4-tert-Butylphthalonitrile (Tokyo Kasei) was
used as supplied. Isotropic distribution patterns of the mass spectra of
the following compounds are given in the Supporting Information.
[24,71-(2,2′-Biphenyldioxy)dibenzo[b,g]-12(or 13),17(or 18)-di-tert-
butyl-5,10,15,20-tetraazaporphyrinato(2-)]cobalt(II), AdCo2. A
mixture of 2,2′-bis(2,3-dicyanophenoxy)biphenyl3q (367 mg, 8.37 ×
10-4 mol), cis-1,2-dicyano-3,3-dimethyl-1-butene18 (218 mg, 1.62 ×
10-3 mol), dried cobalt dichloride (106 mg, 8.16 × 10-4 mol), and a
catalytic amount of ammonium molybdate was refluxed in ethylene
glycol (4 mL) for 17 h under nitrogen, and after cooling the residue
was collected by filtration, washed with water, and dried. The residue
was imposed on silica gel chromatography using hexane/toluene (1:1
v/v) as eluent. The fourth colored fraction, which eluted after the first
purplish red, second blue, and third purplish red fractions, was collected
and further chromatographed over silica gel using hexane/chloroform
(2:3 v/v) as eluent. Addition of methanol and water caused precipitation
(11 mg, 1.8%) of a dark blue powder of the desired compound. Mass
(FAB) (m/z): 766 (M+). Anal. Found: C, 67.41; H, 4.84; N, 14.35.
Calcd for C44H34N8O2Co‚H2O: C, 67.43; H, 4.63; N, 14.30.
[4,8-(2,2′-Biphenyldioxy)-16(or 17),23(or 24)-di-tert-butylphtha-
locyaninato(2-)]cobalt(II), AdCo4. A mixture of 2,2′-bis(2,3-
dicyanophenoxy)biphenyl3q (311 mg, 7.09 × 10-4 mol), 4-tert-
butylphthalonitrile (263 mg, 1.43 × 10-3 mol), cobalt dichloride (92
mg, 7.09 × 10-4 mol), and a catalytic amount of ammonium molybdate
was refluxed in ethylene glycol (4 mL) for 5 h under nitrogen, and
after cooling the residue was collected by filtration and washed with
water and methanol. Alumina chromatography using hexane/chloroform
(2:1 v/v) and subsequent recrystallization from ethyl acetate/hexane
yielded 20 mg (3.3%) of a dark blue solid. Mass (FAB) (m/z): 866
(M+). Anal. Found: C, 72.02; H, 5.09; N, 12.57. Calcd for C52H38N8O2-
Co: C, 72.13; H, 4.42; N, 12.94.
[24,71-(2,2′-Biphenyldioxy)dibenzo[b,g]-123(or 124),173(or 174)-
di-tert-butyldinaphtho[l,q]-5,10,15,20-tetraazaporphyrinato(2-)]co-
balt(II), AdCo6. A mixture of 2,2′-bis(2,3-dicyanophenoxy)biphenyl3q
(386 mg, 8.80 × 10-4 mol), 6-tert-butyldicyanonaphthalene19 (444 mg,
1.89 × 10-3 mol), cobalt dichloride (131 mg, 1.01 × 10-3 mol), and
a catalytic amount of ammonium molybdate was refluxed in ethylene
glycol (4 mL) for 9 h under nitrogen, and after cooling the residue
was collected by filtration and washed with water and methanol. Silica
gel chromatography using toluene as eluent gave 12 mg (1.4%) of a
green solid. Mass (FAB) (m/z): 966 (M+). Anal. Found: C, 74.80; H,
5.04; N, 10.43. Calcd for C60H42N8O2Co: C, 74.60; H, 4.38; N, 11.60.
[24,71-(2,2′-Biphenyldioxy)dibenzo[b,g]-121,128,171,178-tetra(3-
methylbutoxy)dianthro[l,q]-5,10,15,20-tetraazaporphyrinato(2-)]-
cobalt(II), AdCo8. 2,2′-Bis(2,3-dicyanophenoxy)biphenyl3q (111 mg,
2.53 × 10-4 mol) and 2,3-dicyano-1,4-diisopentoxyanthracene3r (205
mg, 5.12 × 10-4 mol) were dissolved in isoamyl alcohol (6 mL)
containing lithium (5 mg, 7.2 × 10-4 mol), and the solution was
refluxed for 1 h under nitrogen. After removal of half of the solvent
by evaporation, DMF (4 mL) and cobalt dichloride (300 mg, 2.31 ×
10-3 mol) were added, and the refluxing was continued for another
hour. After addition of methanol and water, the solid product was
collected by filtration and applied to silica gel chromatography using
toluene as eluent. Recrystallization from hexane afforded 3.4 mg (1.0%)
of the desired compound as a dark reddish brown solid. Mass (FAB)
(m/z): 1298 (M+). Anal. Found: C, 74.15; H, 5.89; N, 7.89. Calcd for
C80H70N8O6Co: C, 74.00; H, 5.43; N, 8.63.
21,24,121,124-Tetraphenyldibenzo[b,l]-7,8,17,18-tetrapropyl-21H,
23H-5,10,15,20-tetraazaporphyrin, OpH22. A mixture of dipropyl-
fumaronitrile21 (2 g, 1.23 × 10-3 mol), 3,6-diphenylphthalonitrile16 (0.95
g, 3.38 × 10-3 mol), and lithium (100 mg, 1.44 × 10-2 mol) was
refluxed in 1-pentanol for 80 min. After removal of the solvent by
evaporation, the residue was imposed on a silica gel column using first
toluene and then carbon tetrachloride as eluent. A portion of Rf ) 0.25
was collected and washed well with hexane, to afford 96 mg (6.4%)
(ii) Molecular Orbital Calculations. MO calculations were per-
formed by the ZINDO/S Hamiltonian in the HyperChem R.5.1
program12a which has been successfully applied to Pc systems.12b,c The
structures of Pc analogues for calculations were constructed by using
X-ray structural data of standard Pc,13 naphthalene,14a and anthracene14b
and by making the rings perfectly planar and adopting either the C2V
or D2h symmetry (essentially the same as those we used in our previous
papers).5,15 The central metal was assumed to be zinc(II) since Co(II)
is paramagnetic. However, to interpret the spectra of low symmetrical
closed-shell d8 Co(I) species, calculations were similarly performed
for two π systems. The choice of configuration was based on energetic
considerations, and all singly excited configurations up to 9 eV (72 590
cm-1) were included.
(iii) Synthesis. Adjacently substituted compounds were prepared
according to the pathway shown in Scheme 1. To prevent the formation
of opposite type species, a diphthalonitrile unit linked by the ortho
positions of biphenyl, i.e., 2,2′-bis(2,3-dicyanophenoxy)biphenyl,3q was
used. Opposite type compounds were obtained by normal mixed
condensation reactions utilizing the steric hindrance of one of the
starting dinitriles, i.e., 3,6-diphenylphthalonitrile.3a,16 OpCo2, OpCo4,
and OpCo6 were obtained by cobalt insertion reaction into the
corresponding metal-free species whose D2h π structures were prede-
termined by 1H NMR and electronic absorption spectra. The tetra-tert-
butylated tetraazaporphyrin cobalt complex (Co0) was that which we
used in our earlier papers.17 tert-Butylated dinitriles,17b,18-20 2,3-dicyano-
1,4-diisopentoxyanthracene,3r and dipropylfumalonitrile21 were prepared
(11) teXan: Crystal Structure Analysis Package; Molecular Structure Corp.,
The Woodlands, TX, 1985 and 1999.
(12) (a) HyperChem R.5.1 Pro; Hypercube Inc., Gainesville, FL, 1997. (b) Mack,
J.; Stillman, M. J. Inorg. Chem. 1997, 36, 413. (c) Cory, M. G.; Hirose,
H.; Zerner, M. C. Inorg. Chem. 1995, 34, 2969.
(13) Robertson, J. M.; Woodward, I. J. Chem. Soc. 1937, 219. Barrett, P. A.;
Dent, C. E.; Linstead, R. P. J. Chem. Soc. 1936, 1719. Brown, C. J. J.
Chem. Soc. A 1968, 2488; 2494. Kirner, J. F.; Dow, W.; Scheidt, D. R.
Inorg. Chem. 1976, 15, 1685.
(14) (a) House, H. O.; Koepsell, D. G.; Campbell, W. J. J. Org. Chem. 1972,
37, 1003. (b) Fillers, J. P.; Ravichsandran, K. G.; Abdalmuhdi, I.; Chang,
C. K. J. Am. Chem. Soc. 1986, 108, 417.
(15) Kobayashi, N.; Konami, H. J. Porphyrins Phthalocyanines 2001, 5, 233.
(16) Mikhalenko, S. A.; Gladyr, S. A.; Luk’yanets, E. A. J. Org. Chem. USSR
1972, 8, 341.
(17) (a) Kobayashi, N.; Nakajima, S.; Osa, T. Chem. Lett. 1992, 2415. (b)
Kobayashi, N.; Nakajima, S.; Osa, T. Inorg. Chim. Acta 1993, 210, 131.
(18) Kopranenkov, V. N.; Goncharova, L. S.; Luk’yanets, E. A. J. Gen. Chem.
USSR 1977, 47, 1954.
(19) Kovshev, E. I.; Punchanova, V. A.; Luk’yanets, E. A. J. Gen. Chem. USSR
1971, 7, 364.
(20) PhthalocyaninessChemistry and Functions; Shirai, H., Kobayashi, N., Eds.;
IPC Publishers: Tokyo, 1997 (in Japanese).
(21) Lange, S. J.; Nie, H.; Stern, C. L.; Barrett, A. G. M.; Hoffman, B. M.
Inorg. Chem. 1998, 37, 6435.
9
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A R T I C L E S
Kobayashi et al.
of the desired compound as a dark blue colored powder.22 Mass (ESI-
TOF) (m/z): 887 ([M + 1]+). Anal. Found: C, 81.27; H, 6.32; N,
12.59. Calcd for C60H54N8: C, 81.23; H, 6.14; N, 12.63. 1H NMR (400
MHz, CDCl3): δ -1.93 (br s, 2H, NH), 0.88 (t, 12H, CH3), 1.72 (sextet,
8H, -CH2-), 3.37 (t, 8H, CH2-), 7.70 (m, 12H, phenyl m-, p-H),
7.91 (s, 4H, arom H), 8.08 (dd, 8H, phenyl o-H). UV-vis (o-DCB)
λmax (log ꢀ): 335 (4.68), 570 (4.42), 613 (4.86), 683 (4.82).
[21,24,121,124-Tetraphenyldibenzo[b,l]-7,8,17,18-tetrapropyl-5,10,
15,20-tetraazaporphyrinato(2-)]cobalt(II), OpCo2. OpH22 (10 mg,
1.12 × 10-5 mol) and Co(OAc)2‚4H2O (160 mg, 6.42 × 10-4 mol)
were refluxed in 2 mL of chlorobenzene/2-ethoxyethanol (1:1 v/v) at
140 °C for 3 h. After removal of the solvent by evaporation, the residue
was purified by preparative TLC on silica using carbon tetrachloride/
toluene (1:1 v/v) as eluent to give, after washing with hexane, 8 mg
(75%) of the dark blue shiny desired solid. Mass (ESI-TOF) (m/z):
944 ([M + 1]+). Anal. Found: C, 75.85; H, 5.52; N, 11.82. Calcd for
C60H52N8Co: C, 76.34; H, 5.55; N, 11.87.
21,24,121,124-Tetraphenyldibenzo[b,l]-72(or 73),172(or 173)-di-tert-
butyldibenzo[g,q]-21H,23H-5,10,15,20-tetraazaporphyrin, OpH24.
A mixture of 3,6-diphenylphthalonitrile16 (2.8 g, 0.01 mol), 4-tert-
butylphthalonitrile (1.84 g, 0.01 mol), and Zn(OAc)2 (1.83 g, 0.01 mol)
was heated at 200 °C for 8 h under nitrogen. The dark blue colored
melt was treated in a refluxing acetic acid/hydrochloric acid (1:1 v/v)
mixture (∼20 mL) for ca. 4 h. After cooling, the solution was poured
onto crushed ice and neutralized with concentrated NH4OH. The
resultant dark blue solid was collected by filtration and washed with
MeOH until the washings were colorless. The solid was then dissolved
in CHCl3 and purified by silica gel chromatography using CHCl3/hexane
(4:1 v/v) as eluent. The first blue fraction was collected and further
purified by preparative TLC on silica using CHCl3/hexane (4:1 v/v) as
eluent, and subsequent recrystallization from CHCl3/ethanol afforded
22 mg (0.47%) of the desired compound. Mass (MALDI-TOF) (m/z):
931 ([M + 1]+). Anal. Found: C, 82.64; H, 5.64; N, 11.77. Calcd for
C64H50N8 (931.1576): C, 82.55; H, 5.41; N, 12.03. 1H NMR (400 MHz,
CDCl3): δ -0.77, -0.58 (2s, 2H, NH), 1.68, 1.70 (2s, 18H, t-Bu),
7.76-8.63 (m, 30H, arom).
[21,24,121,124-Tetraphenyldibenzo[b,l]-72(or 73),172(or 173)-di-tert-
butyldibenzo[g,q]-5,10,15,20-tetraazaporphyrinato(2-)]cobalt(II),
OpCo4. OpH24 (9.3 mg, 0.01 mmol) and CoCl2 5.2 mg (0.04 mmol)
were dissolved in dry DMF (∼10 mL), and the mixture was heated at
50 °C under nitrogen for 24 h. After evaporation of the DMF, the
residue was dissolved in CHCl3 and purified using preparative TLC
and subsequent recrystallization from CHCl3/ethanol to give 8.2 mg
(77.3%) of the desired OpCo2. Mass (ESI-TOF) (m/z): 987 (M+). Anal.
Found: C, 75.87; H, 4.93; N, 11.15. Calcd for C64H48N8Co‚H2O
(1006.0902): C, 76.41; H, 5.01; N, 11.14.
CHCl3/hexane (1:1 v/v) as eluent. The first green fraction was collected
and further purified using preparative TLC on silica and the same eluent.
The analytically pure sample was obtained by precipitation of the CHCl3
solution using ethanol. Yield: 18 mg (0.35%). Mass (MALDI-TOF)
(m/z): 1032 ([M + 1]+). Anal. Found: C, 82.67; H, 5.43; N, 10.71.
Calcd for C72H54N8‚H2O (1049.293): C, 82.42; H, 5.38; N, 10.68. H
NMR (400 MHz, CDCl3): δ -1.53 (br, 2H, NH), 1.71, 1.73 (2s, 18H,
t-Bu), 7.47-8.64 (m, 34H, arom).
1
[21,24,121,124-Tetraphenyldibenzo[b,l]-73(or 74),173(or 174)-di-tert-
butyldinaphtho[g,q]-5,10,15,20-tetraazaporphyrinato(2-)]cobalt-
(II), OpCo6. This compound was obtained by two methods. (i) A
mixture of dry DMF (∼10 mL), OpH26 (10.3 mg, 0.01 mmol), and
CoCl2 (5.2 mg, 0.04 mmol) was heated at 50 °C under nitrogen for 24
h. After evaporation of the DMF, the residue was purified using
preparative TLC with CHCl3 as eluent, and further by reprecipitation
from CHCl3/ethanol, to give 7.6 mg (65.5%) of a green powder of the
desired compound. Mass (ESI-TOF) (m/z): 1087 (M+). Anal. Found:
C, 77.23; H, 5.25; N, 11.00. Calcd for C72H52N8Co‚H2O (1106.2102):
C, 78.18; H, 4.92; N, 10.13. (ii) A mixture of 6-tert-butyl-2,3-
dicyanonaphthalene19 (300 mg, 1.28 × 10-3 mol), 3,6-diphenyl-
phthalonitrile16 (1.05 g, 3.74 × 10-3 mol), CoCl2‚2H2O (139 mg, 8.38
× 10-4 mol), and a catalytic amount of ammonium molybdate was
mixed well and heated at 195 °C for 8 h in ethylene glycol (6 mL).
After the mixture cooled, methanol was added and the resultant
precipitate collected, washed with methanol, and imposed on an alumina
column using toluene as eluent. The fifth blue band was collected and
further purified by silica gel chromatography using toluene as eluent
(Rf ) 0.65) and crystallized from chloroform/methanol to give 11 mg
(1.6%) of a green powder of the desired compound. Mass (FAB) (m/
z): 1088 ([M + 1]+). Anal. Found: C, 79.00; H, 5.02; N, 10.14. Calcd
for C72H52N8Co (1088.1947): C, 79.47; H, 4.82; N, 10.30.
[21,24,121,124-Tetraphenyldibenzo[b,l]-74(or 75),174(or 175)-di-tert-
butyldianthro[g,q]-5,10,15,20-tetraazaporphyrinato(2-)]cobalt-
(II), OpCo8. 3,6-Diphenylphthalonitrile16 (620 mg, 2.21 × 10-3 mol),
6-tert-butyl-2,3-dicyanoanthracene17b,20 (210 mg, 7.38 × 10-4 mol),
CoCl2‚2H2O (110 mg, 7.33 × 10-4 mol), and a catalytic amount of
ammonium molybdate were mixed well in an agate mortar and charged
in a pressure-proof cylinder. After the reaction proceeded for 40 min
at 270 °C, the products were imposed on an alumina column using
first CH2Cl2 until all the soluble material came out and then CH2Cl2/
MeOH to elute the portion containing the desired compound. The latter
portion was further purified using preparative TLC on silica and toluene
containing 2% pyridine (Rf ) 0.72), and further using preparative TLC
on alumina with CHCl3 as eluent (Rf ) 0.5), to give 1.4 mg (0.3%) of
green powder of the desired compound. Mass (FAB) (m/z): 1188 (M+).
Results and Discussion
21,24,121,124-Tetraphenyldibenzo[b,l]-73(or 74),173(or 174)-di-tert-
butyldinaphtho[g,q]-21H,23H-5,10,15,20-tetraazaporphyrin, OpH26.
Magnesium metal (0.24 g, 0.01 mol) and dry n-butyl alcohol (100 mL)
were heated to reflux under nitrogen for 4 h, and 3,6-diphenylphtha-
lonitrile16 (2.8 g, 0.01 mol) and 6-tert-butyl-2,3-dicyanonaphthalene19
(2.34 g, 0.01 mol) were added, and the reaction continued for 24 h.
The solvent was removed using an evaporator, 50 mL of CF3COOH
was added, and the solution was stirred for ca. 15 min in the dark. The
solution was poured onto crushed ice and neutralized with concentrated
NH4OH. The resultant dark green solid was filtered off and washed
several times with MeOH until the washings became colorless. The
solid was then purified by silica gel column chromatography using
(i) Synthesis. The synthesis of the adjacently substituted
species was straightforward. By the use of diphthalonitrile linked
by the shortest linkage, i.e., 2,2′-bis(2,3-dicyanophenoxy)-
biphenyl,3q the desired compounds were obtained without danger
of contamination by opposite species. However, in the case of
the opposite type species, it was necessary to confirm the D2h
type structure before insertion of the cobalt. The reactivity for
cyclization of the aromatic ortho dinitriles decreased the larger
the π system. Accordingly, to obtain larger macrocycles, more
severe reaction conditions (higher reaction temperatures and
longer reaction times) were required, yet the yields were not
increased markedly. In addition, purification of the larger
complexes became harder due to their reduced solubility and
stronger adsorption to silica or alumina columns. The stability
also seemed to be decreased for larger macrocycles. For
example, although OpCo6 and OpCo8 were stable in the solid
state, the color of an o-DCB solution of OpCo6 and OpCo8
changed gradually over a period of days.
(22) A portion with Rf ) 0.15 (silica, CCl4) was confirmed to be the
corresponding adjacent isomer, 21,24,71,74-tetraphenyldibenzo[b,g]-12,13,-
17,18-tetrapropyl-21H,23H-5,10,15,20-tetraazaporphine, from the following
data. Mass (ESI-TOF) (m/z): 887 ([M + 1]+). 1H NMR (400 MHz,
CDCl3): δ -0.32, -0.35 (2s, 2H, NH), 0.88 (t, 6H, CH3), 1.22 (t, 6H,
CH3), 1.68 (sextet, 4H, -CH2-), 2.23 (sextet, 4H, -CH2-), 3.27 (t, 4H,
CH2-), 3.71 (t, 4H, CH2-), 7.23-7.41 (m, 8H, phenyl), 7.70-7.74 (m,
8H, phenyl), 7.83 (d, 2H, arom H), 7.93 (d, 2H, arom H), 8.11 (dd, 4H,
phenyl). UV-vis (CHCl3) λmax: 269, 333, 586, 642, 685.
9
8010 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
Table 1. Crystal Data and Experimental Details of OpCo2
empirical formula
formula weight
crystal system
C67H60N8Co
1036.20
triclinic
space group
P1h (No. 2)
crystal color, habit
crystal dimensions
lattice parameters
blue, plate
0.05 × 0.10 × 0.20 mm
a ) 12.890(2) Å
b ) 14.5300(8) Å
c ) 16.270(4) Å
R ) 69.290(8)°
â ) 69.750(4)°
γ ) 84.370(4)°
V ) 2673.1(8) Å3
-100.0 °C
temperature
Z value
2
residuals: R1; Rw
goodness-of-fit indicator
linear absorption coefficient
0.070; 0.103
1.25
3.72 cm-1
pyrroles (106.4(8)° and 105.1(8)°), and the Co-N(pyrrole)
distance along the long axis of the molecule (av. 1.92 Å) is
longer by 0.01 Å than that along the short axis. Although not
explicitly perceivable in Figure 2, the plane connecting the two
fused benzo rings is slightly bent toward a toluene molecule
included in the crystal (for further details, see Supporting
Information).
(iii) Electronic Absorption and Magnetic Circular Dichro-
ism Spectroscopy. We could not detect any evidence for
aggregation until ca. 10-4 mol/L. Accordingly, spectroscopic
data were collected at concentrations lower than this concentra-
tion.
(a) C2W Species. Figure 3A and B shows absorption and MCD
spectra, respectively, of C2V species in toluene, with the Q-band
data for these summarized in Table 2. With increasing size of
the π system, the Q-band shows a significant shift to longer
wavelength, while the Soret band broadens and has a slight shift
to longer wavelength. The shifts of the Q-bands are 1550 cm-1
for Co0-AdCo2, 1020 cm-1 for AdCo2-AdCo4, 837 cm-1
Figure 2. ORTEP drawing of OpCo2‚C6H5CH3 showing the 50% prob-
ability thermal ellipsoids. Hydrogen atoms have been omitted for clarity.
(ii) X-ray Crystal Analysis of OpCo2. Although the D2h
structure was confirmed in most cases from measurements of
1H NMR and electronic absorption spectra, the structure of
OpCo2 was also confirmed by X-ray analysis of a single crystal
which was grown from toluene/methanol solution, since it gave
an unusual electronic spectrum (see following sections). The
crystal data and experimental details are summarized in Table
1. As shown in Figure 2, OpCo2 had the expected opposite
type D2h π structure.23 The X-ray structural data for the same
π structure were previously reported for a nickel complex.3g In
that case, all bond lengths and angles within the two distinct
types of pyrroles were nearly equivalent. In OpCo2, the CR-
Np-CR angles in pyrroles with the fused benzo rings (108.1(7)°
and 106.8(8)°) are slightly larger than those in the alkyl-linked
Figure 3. (A) Electronic absorption and (B) MCD spectra of Co0, AdCo2, AdCo4, AdCo6, and AdCo8 in toluene.
J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002 8011
9

A R T I C L E S
Kobayashi et al.
Table 2. Electronic Absorption and MCD Spectral Data
3
species
electronic absorption λ/nm (log ꢀ)
MCD λ/nm (10-4[θ]M/deg‚dm mol-1 cm-1 T-1
)
long/shorta ∆λ/cm-1 b
f c
Co0
319 (4.47) 338 (4.46) 573 (4.59)
321 (-1.45) 348 (-2.33) 526 (12.0)
580 (-21.3)
560 (12.6)
1.00
1.00
1.00
1.00
1.00
1.62
1.00
1.37
1.73
0
0.012
AdCo2 319 (4.57) 570 (4.32) 629 (4.80)
304 (1.89)
619 (12.9)
345 (-2.49) 365 (-1.82) 570 (18.7)
∼0
0.129
0.193
0.234
0.240
637 (-49.4)
343 (-4.59) 607 (44.6)
676 (-218)
AdCo4 328 (4.78) 607 (4.53) 647 (4.58) 672 (5.26) 318 (5.09)
665 (181)
AdCo6 335 (4.87) 412 (4.05) 639 (4.56) 682 (4.60) 323 (6.25)
637 (26.8)
199
269
274
545
602
1025
1884
347 (-6.66) 382 (-1.18) 424 (3.07)
712 (5.28)
639 (43.0)
673 (25.5)
354 (-6.37) 472 (1.46)
739 (10.4) 779 (70.3)
706 (171)
718 (-219)
504 (4.74)
801 (-100)
AdCo8 330 (4.82) 350 (4.84) 495 (4.20) 706 (4.52) 325 (1.68)
789 (5.17)
702 (22.8)
308 (1.52)
630 (23.0)
OpCo2 328 (4.76) 583 (4.45) 639 (4.92)
340 (-4.40) 364 (-3.23) 582 (19.5)
654 (-45.4)
347 (-6.89) 618 (26.4)
OpCo4 331 (4.86) 610 (4.47) 673 (5.01) 697 (5.01) 323 (3.02)
698 (-83.3)
OpCo6 323 (4.86) 631 (4.53) 688 (4.95) 705 (4.89) 323 (3.09)
668 (35.1)
352 (-5.79) 632 (17.5)
762 (-48.6)
368 (-4.69) 417 (-1.82) 474 (1.92)
826 (-22.5)
680 (50.1)
763 (4.96)
705 (5.56)
OpCo8 323 (4.85) 372 (4.76) 658 (4.49) 719 (4.89) 316 (1.92)
825 (4.67) 712 (28.4)
a Geometrical ratio of the long axis to short axes of π conjugated structures. b Splitting of the Q-band estimated by band deconvolution analysis of both
electronic absorption and MCD spectral data. c The oscillator strength of the Q-band estimated by band deconvolution analysis.
for AdCo4-AdCo6, and 1370 cm-1 for AdCo6-AdCo8. Here,
the substituent effect must be taken into account, particularly
since the effect of the alkoxy group is large when it is linked to
the benzene periphery closest to the Pc core (the so-called R
positions).24,25 Substituent effects depend on the type and
number of the substituent groups, and approximate additivity
exists when the same substituent is introduced at the same
position of fused aromatics. For example, when the Q-band of
tetra-tert-butylated ZnPc prepared from 4-tert-butylphthalonitrile
is compared with that of peripherally unsubstituted ZnPc, the
Q-band of the former occurs at longer wavelength than the latter,
by ca. 140 cm-1 (i.e., 33 cm-1 per tert-butyl group).26 Similarly,
the Q-band position of Pc’s containing eight alkoxy groups at
the so-called R positions appears approximately 1400-1840
cm-1 lower in energy than the band position of unsubstituted
species.25,27 Thus, if we unify the substituent effect, calculating
from the effect of tert-butyl groups and alkoxy groups, the above
interpreted if we consider that the substituent effect of the outer
fused benzene unit is smaller than that on the inner side.3r
A few small absorption peaks have been detected between
the Q and Soret bands of AdCo6 and AdCo8 (Figure 3A). These
are assigned to transitions restricted mainly in the naphthalene
or anthracene ring moieties (see MO section).
The MCD spectra of these C2V (D4h for Co0) species show
dispersion type, Faraday A-term type curves corresponding to
the Q00 absorption peaks, indicating that their excited states are
orbitally doubly degenerate.28 The occurrence of this phenom-
enon for C2V type species, however, was predicted ca. 40 years
ago independently by Ballhausen29a and Gouterman.29b When
benzene units are fused to the D4h TAP skeleton, viewing
radially from the center of the TAP skeleton, the originally
degenerate Qx00 and Qy00 bands shift to longer wavelength to
the same extent, so that a single Q-band without detectable
energy splitting is observed even in the resultant C2V type
compounds. The appearance of Faraday A-term type curves in
a system lacking a symmetry element higher than a 3-fold
rotation axis may be surprising. However, if the Qx00 and Qy00
bands differ slightly in energy, these Faraday A-term type curves
can be rationalized as pseudo A-terms30a produced by the
superimposition of closely lying Faraday B-terms of opposite
signs.30b The SAP effect is a first-order perturbation.4,29b
Accordingly, the Q-band position of the Qx00 and Qy00 bands in
C2V π systems is expected to be at the same energy. Later,
however, we show that MO calculations based on the actual
C2V symmetry and including much higher perturbation terms
than the SAP method produce a slightly split Q-band (section
(v)).
differences may be ca. 1320, 1020, 837, and 520-740 cm-1
,
respectively, in the above order, i.e., per two benzene units.
The shift is, in this way, not linear with respect to the number
of fused benzene unit, but its extent decreases with increasing
molecular size. In other words, the substituent effect of the outer
benzene unit is smaller than that of the inner one. Thus, when
a benzene unit is fused to the tetraazaporphyrin (TAP) skeleton
directly, the wavelength of the Q-band shift is roughly ca. 510-
660 cm-1, while for a benzene unit fused via benzene and
naphthalene, it is approximately 420 and 260-370 cm-1
,
respectively. This is also seen when comparing the Q-band
position between AdCo8 (789 nm, 12 670 cm-1) and tetra-tert-
butylated cobalt naphthalocyanine (756 nm, 13 230 cm-1 24
) in
To understand the spectroscopic variations more quantita-
tively, the oscillator strength, f, of the Q-band was estimated
the same solvent. The size of the π conjugation system of both
compounds is the same; i.e., eight benzene units are fused to
the TAP skeleton. If we eliminate the substituent effect of the
tert-butyl and alkoxy groups, the Q00-band of these compounds
may appear at around 735 ( 6 and 752 ( 1 nm (ca. 13 600 (
100 and 13 300 cm-1),24 respectively. Thus, although the π
skeleton of AdCo8 (adjacently dinaphtho-substituted Pc) and
naphthalocyanine has an isomeric relationship, the effective π
size of the former appears smaller. This is again reasonably
(24) Luk’yanets, E. A. Electronic Spectra of Phthalocyanines and Related
Compounds; NIOPIK: Moscow, 1989.
(25) (a) Kobayashi, N.; Sasaki, N.; Higashi, Y.; Osa, T. Inorg. Chem. 1995, 34,
1636. (b) Cook, M. J.; Dunn, A. J.; Howe, S. D.; Thomson, A. J.; Harrison,
K. J. J. Chem. Soc., Perkin Trans. 1 1998, 2453. (c) Bedworth, P. V.;
Perry, J. W.; Marder, S. R. Chem. Commun. 1997, 1353.
(26) Konami, H.; Hatano, M. Chem. Lett. 1988, 1359.
(27) Our unpublished data.
(28) Stillman, M. J.; Nyokong, T. In ref 1, Vol. 1, Chapter 3.
(29) (a) Ballhausen, C. J. Introduction to Ligand Field Theory; McGraw-Hill:
New York, 1962. (b) Gouterman, M. J. Mol. Spectrosc. 1961, 6, 138.
(30) (a) Kaito, A.; Nozawa, T.; Yamamoto, T.; Hatano, M.; Orii, Y. Chem.
Phys. Lett. 1977, 52, 154. (b) Tajiri, A.; Winkler, Z. Z. Naturforsch. 1983,
38a, 1263.
(23) Detailed X-ray data are available as Supporting Information.
9
8012 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
Figure 4. (A) Electronic absorption and (B) MCD spectra of OpCo2, OpCo4, OpCo6, and OpCo8 in o-DCB.
by band deconvolution analysis (Table 2).31,32 The value is seen
to increase, while the extent of the change decreases with
increasing molecular size.
in these molecules. The Q MCD bands of OpCo2 and OpCo4
look like Faraday A-terms in shape, but these are produced by
the superimposition of closely lying Faraday B-terms of opposite
signs.30 The energy difference between the opposite and adjacent
isomers increases with increasing ratio of long axis to short axis,
and in the cases of Co8 species, the splitting energies for the
(b) D2h Species. Figure 4A and B displays absorption and
MCD spectra of D2h type species in toluene, with data
summarized in Table 2. Only OpCo2 was prepared from 3,6-
diphenylphthalonitrile and dipropylmaleonitrile, since when tert-
butylated maleonitrile was used as one of the two starting
dinitriles, the desired compound could not be separated from
the other reaction products. However, since the substituent effect
of alkyl groups is small,,24,26 we considered that this would not
produce any serious problem for the analysis and discussion.
Similarly to the case for the above C2V type species, the Q-band
shifts to longer wavelength, while the extent of change decreases
with increasing molecular size. In addition, the Q-band generally
splits into two peaks, and the degree of splitting increases with
increasing molecular size. If we define the center of the split
bands as the band position, ∆E of OpCo2-OpCo4, OpCo4-
opposite and adjacent isomers become 1940 and 353 cm-1
,
respectively. In the spectra of OpCo4, OpCo6, and OpCo8, the
positions of the MCD peaks and troughs nearly correspond to
the absorption peaks, supporting the contribution of Faraday
B-terms.
(iv) Electrochemistry and Spectroelectrochemistry. Cyclic
voltammograms of all the cobalt complexes are shown in Figure
5, and the electrochemical data are summarized in Table 3.
Although the substituent groups of the adjacently and oppositely
substituted complexes are different, there are many similarities
between the complexes. For example, the potentials of the first
reduction (CoII/I) and second reduction couples (ligand first
reduction, L-2/-3) are very close to each other for all complexes,
OpCo6, and OpCo6-OpCo8 are 1050, 960, and 631 cm-1
,
2
respectively, and the splitting energies of the Q-bands change
as summarized in Table 2. Compared with the Q-band, the Soret
band position does not change significantly from species to
species and remains in the 323-328 nm region. The peak at
372 nm of OpCo8 may be a split component of the Soret band,
since the MCD spectra give opposite signs corresponding to
the absorption peaks at 323 and 372 nm.
indicating that the orbital energy for accepting electrons (dz
and the LUMO) does not change significantly from species to
species, even if the size of the molecule varies. Another
similarity is the significant negative shift of the first (L-1/-2
)
and second ligand oxidation (L0/-1) potentials with increasing
molecular size (Table 3). Thus, irrespective of the molecular
shape, whether it is C2V or D2h, the HOMO destabilizes with
increasing molecular size.33 However, there are also some
differences. We observed two characteristics. The most notable
difference was seen in the cyclic voltammograms of AdCo2
The MCD spectra of these species are composed of super-
position of Faraday B-terms, since there is no orbital degeneracy
(31) Band deconvolution of the spectral data was carried out using the program
SIMPFIT developed by Stillman’s group.32 Reasonable fits could be
obtained by fitting Faraday A-terms at the Q-bands of these compounds.
Detailed band fitting parameters are available as Supporting Information.
(32) (a) Browett, W. R.; Stillman, M. J. Comput. Chem. 1987, 11, 241. (b)
Nyokong, T.; Gasyna, Z.; Stillman, M. J. Inorg. Chem. 1987, 26, 1087. (c)
Browett, W. R.; Gasyna, Z.; Stillman, M. J. J. Am. Chem. Soc. 1988, 110,
3633. (d) Ough, E.; Nyokong, T.; Creber, K. A. M.; Stillman, M. J. Inorg.
Chem. 1988, 27, 2724. (e) Ough, E. A.; Stillman, M. J. Inorg. Chem. 1994,
33, 573. (f) Mack, J.; Stillman, M. J. J. Am. Chem. Soc. 1994, 116, 1292.
(33) Concerning the argument of the changes of the HOMO energies based upon
redox potential shifts, one reviewer pointed out that the shifts may reflect
large changes in stabilization energies of the oxidized rather than parent
species. This possibility cannot be ruled out. However, we feel that the
shifts are more related to the changes of the HOMO energies as follows.
Namely, if we can presume that the larger compounds are more readily
oxidized by allowing the positive charge to be delocalized to a larger extent,
the shifts of the LUMO also can be conjectured to change in a similar
manner. The experimental results, however, do not show this trend.
9
J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002 8013

A R T I C L E S
Kobayashi et al.
Figure 5. Cyclic voltammograms of all cobalt complexes in this study, measured at a scan rate of 50 mV/s in o-DCB containing 0.1 M TBAP. Concentrations
of the compounds used for the measurements are shown.
Table 3. Redox Potential Data (vs Fc+/Fc) for AdCo2, AdCo4, AdCo6, AdCo8, OpCo2, OpCo4, OpCo6, and OpCo8 in o-Dichlorobenzene
Containing 0.1 M TBAPa
III/II
II/I
species
E
3+/2+ (L0/-1
)
E
2+/1+ (Co
)
E
1+/0 (L-1/-2
)
E
0/1- (Co )
E
1-/2- (L-2/-3
)
∆E b
p
AdCo2
AdCo4
AdCo6
AdCo8
OpCo2
OpCo4
OpCo6
OpCo8
0.40 (0.10)
0.60 (0.11)
0.54 (0.11)
0.61 (0.20)
0.48 (0.14)
0.48 (0.11)
0.48 (0.10)
0.54 (0.10)
0.58 (0.10)
0.16 (0.12)
0.03 (0.20)
-0.15 (0.10)
0.14, 0.25c
0.05 (0.10)
-0.05 (0.13)
-0.14 (0.13)
-0.89 (0.11)
-0.87 (0.10)
-0.89 (0.10)
-0.86 (0.10)
-1.03 (0.12)
-0.97 (0.10)
-0.90 (0.22)
-0.90 (0.15)
-2.03 (0.11)
-2.02 (0.12)
-2.02 (0.10)
-2.01 (0.10)
-2.17 (0.14)
-2.03c
2.61
2.18
2.05
1.86
2.42
2.08
1.95
1.83
0.75 (0.11)
0.17 (0.10)
0.73 (0.11)
0.76c
0.62 (0.10)
0.34 (0.09)
-2.00 (0.10)
-1.97 (0.11)
a Numbers in parentheses indicate the potential differences between negative and positive peak potentials at a sweep rate 50 mV/s. b The potential differences
between the first oxidation and reduction potentials. c The potentials are not clear in the cyclic voltammograms, therefore, these potentials are determined
from differential pulse voltammograms.
and OpCo2 in the positive potential region. Although the
assignment of the redox couple was based on the spectroelec-
trochemistry results, which are described below, the first
oxidation couple for AdCo2 is assigned to the CoIII/II couple,
while that for OpCo2 is assigned to the first ligand oxidation.
Because of this phenomenon, there is a possibility that the first
ligand oxidation potential of AdCo2 is more positive than that
of normal AdMt2 without metal oxidation, since part of the
+1 charge of cobalt spreads over the ligand, thereby making
ligand oxidation more difficult. The second point concerns the
detection of the second ligand oxidation couple. As seen in the
voltammograms, this couple is observed for all oppositely
substituted species, but in the case of adjacently substituted
species it is only seen with naphthalene and anthracene
substituted species. This may be related to the fact that the
Q-band position of AdCo species lies at shorter wavelength than
the longest wavelength component of the split Q-band of OpCo
species.
Oxidation across the first couple of AdCo2 and OpCo2
resulted in the spectroscopic changes shown in Figure 6A and
B, respectively. In the case of AdCo2, the Soret band decreased
in intensity and a new peak appeared to longer wavelength,
while the Q-band intensified markedly, with isosbestic points
occurring at five wavelengths. These are the changes commonly
observed when CoII is oxidized to CoIII species in Pc and Pc
analogues.34 Although the first oxidation of CoPc occurs at the
cobalt in coordinating solvents such as DMF, it generally occurs
at the ligand in noncoordinating solvents such as o-DCB, as
used in this study. AdCo2 is only the second example of a
compound showing the first oxidation at cobalt in noncoordi-
nating solvent, following tetra-tert-butylated tetraazaporphyrin.17a
Since the first oxidation of cobalt tetraphenyl- and octaeth-
(34) (a) Nevin, W. A.; Liu, W.; Greenberg, S.; Hempstead, M. R.; Marcuccio,
S. M.; Melnik, M.; Leznoff, C. C.; Lever, A. B. P. Inorg. Chem. 1987, 26,
891. (b) Kobayashi, N.; Herman, L. W.; Nevin, W. A.; Janda, P.; Leznoff,
C. C.; Lever, A. B. P. Inorg. Chem. 1990, 29, 3415. (c) Day, P.; Hill, H.
A. O.; Price, M. G. J. Chem. Soc. (A) 1968, 90.
9
8014 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
Figure 6. Development of the electronic spectra of (A) AdCoII2 and (B)
OpCoII2 with time, showing the formation of (A) cobalt-oxidized AdCoIII2
and (B) ligand-oxidized OpCoII2 radical species, respectively. The applied
potentials were +0.96 and +0.82 V vs Ag/AgCl, respectively.
Figure 7. Development of the electronic spectra of (A) AdCoII2 and (B)
OpCoII2 with time, showing the formation of cobalt-reduced (A) AdCoI2
and (B) OpCoI2, respectively. The applied potentials were -1.0 and -1.3
V vs Ag/AgCl, respectively.
ylporphyrins in noncoordinating solvents generally occurs at
cobalt, AdCo2 appears to be intermediate between normal
porphyrins and Pc’s.35 In contrast, in the spectra of OpCo2, the
original Q-band decreased in intensity, and a new Q-band peak
developed at longer wavelength, at 707 nm, together with a
weak, broad band extending to ca. 1000 nm. These are
indications of ligand oxidation, which is seen not only in cobalt
Pc’s but also in other metallo Pc’s.36 Thus, OpCoII2 was
concluded to be oxidized to OpCoII2 ring-oxidized cation radical
species.
Although not shown, when the AdCoIII2 species was further
oxidized at a potential positive of the second oxidation potential
(+1.2 V vs Ag/AgCl), the intense Q-band decreased in intensity
and a new peak appeared at a longer wavelength, 668 nm,
together with a small peak at ca. 950 nm. From these changes,
we concluded that the ligand was oxidized36 to produce the
AdCoIII2 π cation radical species.
Figure 8. Size and symmetry dependence of the first and second oxidation
Figure 7A and B shows the spectroscopic changes observed
across the first reduction of AdCo2 and OpCo2, respectively.
With the progress of electrolysis, both compounds showed
roughly similar changes; the Q-band faded away and a new
Q-band, which has approximately half the intensity of the
original Q-band, developed at longer wavelength, accompanied
by an increase in absorbance in the region between the Q and
Soret bands. A set of isosbestic points was detected at least at
three wavelengths. These are similar to the changes observed
to date for many CoPc derivatives when CoII was reduced to
CoI, and the band developed between the Q and Soret bands
has been assigned to an MLCT band from cobalt eg to ligand
b1u and b2u orbitals under D4h symmetry.37 Thus, there is no
doubt that the first reduction is occurring at cobalt.
and the first reduction couples, for data collected from Figure 5 and Table
3.
opposite and adjacent isomers. For example, although the first
reduction potential of adjacent species is independent of the
molecular size, that of the oppositely substituted species
stabilizes slightly with increasing molecular size. Although the
extent of this is only slight, it appears to be real, since the first
reduction potential shifts systematically positively with increas-
ing molecular size. This may be related to the splitting of the
LUMO in the oppositely substituted species, since the LUMO
energy in these species is always lower than that of the core. In
addition, although not easily perceivable from this figure, the
potential difference between the first oxidation and reduction
of oppositely substituted species is approximately 100 mV
smaller than that in the adjacently substituted species.
(v) Molecular Orbital Calculations. (a) Predicted Absorp-
tion Spectra. To enhance our understanding of the above
spectroscopic and electrochemical data, MO calculations have
been performed using the ZINDO/S Hamiltonian.12 Figure 9A
and B displays the calculated spectra, while Table 4 summarizes
the details of the calculation results, including orientation of
transition dipoles and configurations. Calculations were carried
out for the zinc structures, since Co(II) is paramagnetic.
The size and symmetry dependence of the first and second
oxidation and the first reduction couples is summarized in Figure
8, collected from the data in Figure 5 and Table 3. This figure
demonstrates that there are a few differences between the
(35) Wolberg, A.; Manassen, J. J. Am. Chem. Soc. 1970, 92, 2982. Lin, X. Q.;
Kadish, K. M. Anal. Chem. 1985, 57, 1498.
(36) Manivannan, V.; Nevin, W. A.; Leznoff, C. C.; Lever, A. B. P. J. Coord.
Chem. 1988, 19, 139. Stillman, M. J. In ref 1, Vol. 3, Chapter 5. Nevin,
W. A.; Lever, A. B. P. Anal. Chem. 1988, 60, 727.
(37) Stillman, M. J.; Thomson, A. J. J. Chem. Soc., Faraday Trans. 2 1973, 70,
790. Kobayashi, N. Coord. Chem. ReV. 2001, 219-221, 93.
9
J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002 8015

A R T I C L E S
Kobayashi et al.
Table 4. Calculated Transition Energies, Oscillator Strength (f), and Configurationsa
energy/
cm-1
energy/
cm-1
nm
f
pol.b
configurationsc
nm
f
pol.b
configurationsc
TAP
16330 612 0.656
16330 612 0.656
35010 286 0.061
x
y
y
57-58 (89)
57-59 (89)
55-58 (92)
35010 286 0.061
36150 277 2.806
36150 277 2.806
x
y
x
55-59 (92)
56-58 (84)
56-59 (84)
57-59 (10)
57-58 (10)
AdZn2
15540 644 0.753
15610 640 0.863
27480 364 0.051
35210 284 0.999
36140 277 0.341
36270 276 2.27
y
x
y
y
y
x
75-76 (95)
75-77 (93)
75-79 (95)
74-77 (48)
71-76 (27)
74-76 (68)
36880 271 0.272
37090 270 0.208
37100 270 0.357
38690 258 0.467
39300 254 0.139
y
x
y
y
y
73-76 (81)
72-76 (57)
75-83 (46)
75-81 (37)
75-81 (29)
71-77 (11)
71-76 (21)
72-77 (29)
75-81 (16)
72-76 (15)
75-83 (28)
AdZn6
13370 748 1.123
13460 743 1.199
19720 507 0.074
31450 318 0.167
32020 312 0.148
34240 292 0.08
35830 279 0.495
36470 274 1.94
y
x
y
x
y
x
y
x
111-112 (95)
111-113 (95)
111-114 (95)
110-120 (82)
36530 274 0.15
36850 271 1.404
37800 265 0.405
38320 261 0.289
38360 261 0.36
38800 258 0.231
39860 251 0.145
40090 249 0.432
x
y
y
x
y
x
x
x
111-122 (75)
108-113 (55) 104-113 (16)
107-112 (20) 105-112 (17)
111-124 (58)
110-113 (49) 109-112 (23)
111-120 (66) 109-113 (19)
111-123 (70)
107-112 (36) 111-125 (26)
107-113 (27) 111-124 (19) 104-112 (15)
106-112 (36)
108-112 (65)
110-114 (23) 104-112 (19) 109-115 (16)
AdZn8
12760 783 1.102
13060 766 1.282
17820 561 0.178
19060 525 0.056
27550 363 0.064
28660 349 0.11
28960 345 0.213
29360 341 0.266
33460 299 0.06
y
x
y
x
x
y
y
y
x
129-130 (95)
33740 296 0.078
35590 281 0.81
35740 280 2.423
36230 276 0.619
36550 274 1.443
37220 269 0.176
37730 265 0.263
37830 264 0.258
38630 259 0.512
y
y
x
y
y
x
x
y
x
128-133 (38) 127-132 (22)
129-141 (39) 129-142 (38)
126-130 (37)
129-141 (26) 129-145 (25) 126-131 (22)
126-131 (32) 129-142 (22)
123-131 (58)
129-143 (30) 129-144 (30)
123-130 (39)
126-130 (22)
129-131 (95)
129-132 (93)
129-133 (95)
128-130 (8)
128-131 (66)
127-130 (37) 129-137 (26)
127-131 (55) 128-132 (21)
129-140 (43)
Nc
12740 785 1.301
12740 785 1.301
21300 469 0.09
21300 469 0.09
31960 313 0.204
31960 313 0.204
35230 284 0.148
x
y
x
y
x
y
x
129-130 (95)
129-131 (95)
129-134 (90)
129-135 (90)
128-130 (71)
128-131 (71)
125-130 (40)
35230 284 0.148
36190 276 0.227
36190 276 0.227
36930 271 2.6 16
36930 271 2.616
39120 256 0.466
39120 256 0.466
y
y
x
y
x
y
x
125-131 (40)
129-142 (50) 129-143(22)
129-143 (50) 129-142 (22)
124-130 (56) 125-131 (29)
124-131 (56) 125-130 (29)
123-130 (70)
123-131 (70)
Pc
14240 702 1.071
14240 702 1.071
36020 278 0.985
36020 278 0.985
y
x
y
x
93-95 (91)
37580 266 0.807
37580 266 0.807
38290 261 0.866
38290 261 0.866
y
x
y
x
92-94 (48)
92-95 (48)
89-94 (73)
89-95 (73)
93-102 (26) 89-94 (15)
93-103 (26) 89-95 (15)
92-94 (19)
93-94 (91)
93-102 (68) 92-94 (22)
93-103 (68) 92-95 (22)
92-95 (19)
OpZn2
14530 688 0.953
16250 616 0.801
33300 300 1.079
34500 290 1.70
37370 268 0.079
y
x
x
x
x
75-76 (93)
75-77 (91)
71-76 (49)
74-76 (45)
75-81 (78)
39000 256 0.987
39310 254 1.343
40650 246 0.105
40760 245 0.258
y
y
x
y
71-77 (46)
74-77 (44)
67-76 (53)
69-76 (88)
74-77 (44)
71-77 (40)
69-77 (26)
74-76 (38)
71-76 (38)
OpZn6
13150 760 1.07
13710 729 1.313
22160 451 0.053
33070 302 0.361
33920 294 0.249
35730 280 3.204
y
x
y
x
y
x
111-112 (96)
111-113 (95)
111-115 (97)
109-113 (63)
111-121 (81)
108-112 (81)
37010 270 0.243
37690 265 0.196
38410 260 0.204
39070 256 1.306
40250 248 1.054
41510 241 0.22
y
x
y
y
y
y
108-113 (32) 111-123 (32)
106-112 (80)
111-123 (50) 108-113 (31)
106-113 (72)
110-114 (24) 111-127 (20) 109-115 (17)
111-127 (64)
OpZn8
12660 790 1.027
13390 747 1.569
19560 511 0.072
26180 382 0.093
28460 351 0.064
29650 337 0.345
30680 326 0.226
33250 301 0.199
y
x
y
x
y
x
y
y
129-130 (96)
129-131 (95)
129-133 (94)
129-136 (96)
34820 287 3.736
35550 281 0.334
37490 267 0.104
38690 258 2.312
39180 255 0.156
39730 252 0.390
40410 247 0.105
x
y
x
y
x
y
x
y
126-130 (67)
129-141 (74)
124-130 (75) 118-130 (15)
126-131 (63)
127-130 (67) 128-132 (20)
127-131 (70)
129-146 (52) 129-152 (20)
129-147 (34) 124-131 (25) 129-144 (18)
128-134 (14)
129-138 (72)
128-132 (33) 127-133 (29) 127-130 (17) 41280 242 0.081
129-147 (23) 128-137 (20)
a Excited states with less than 42000 cm-1, f > 0.05, and configurations which contribute more than 15% are shown. b Polarization. c Orbital numbers 57,
93, 75, 111, and 129 are HOMOs of TAP, Pc, AdZn2 and OpZn2, AdZn6 and OpZn6, and AdZn8, OpZn8, and Nc, respectively. In AdZn6 and OpZn6, the
MOs numbered 109, 110, 114, and 115 are naphthalene-centered orbitals. In AdZn8 and OpZn8, the MOs numbered 127,128, 132, and 133 are anthracene-
centered orbitals. In Nc, the MOs numbered 125, 126, 127, 128, 133, 134, and 135 are naphthalene-centered orbitals.
9
8016 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
With respect to opposite type species, the following results
have been obtained and are therefore compared with experi-
ments. (vi) The Q-band splits into two, and the extent of the
splitting is larger the larger the difference between the short
and long axes of the molecule, as has been observed experi-
mentally (Table 2). However, no obvious splitting was detected
in the absorption spectra of OpCo2 (Figure 4A), despite this
being substantiated to be the opposite type isomer by X-ray
analysis (section (i)) (we will comments on this point later,
below). (vii) If we define the center of the split Q-band as the
positions of the Q-band, this is similar to the corresponding
adjacent species, as expected from the symmetry-adapted
perturbation theory.4,5,29b For OpZn2, OpZn6, and OpZn8, the
positions are 650, 745, and 768 nm (or 15 380, 13 460, and
13 020 cm-1), and the values for AdZn2, AdZn6, and AdZn8
were 642, 745, and 775 nm (or 15 580, 13 420, and 12 900
cm-1). (viii) Calculated oscillator strengths of the Q-band of
opposite species appear slightly (3-9%) larger than those of
the corresponding adjacent species (Table 4), although it is
difficult to detect this difference experimentally. (ix) The Soret
band position does not depend markedly on the molecular size.
In the case of OpZn6 and OpZn8, naphthalene- or anthracene-
centered, short-axis polarized transitions have been predicted
to the red of the Soret band.
Figure 9. Calculated absorption spectra for the low symmetrical zinc
derivatives in this study. (A) Adjacent species and (B) opposite species.
Corresponding to the experimental data obtained for adjacent
molecules (Figure 3), the following information has been
obtained from the calculations. (i) The Q-band shifts to longer
wavelength, but the extent of this per two benzene units becomes
smaller the larger the size of the molecules. The experimental
energy differences were, after elimination of the substituent
effect, ca. 1320 cm-1 for Co0-AdCo2, 1020 cm-1 for AdCo2-
AdCo4, 837 cm-1 for AdCo4-AdCo6, and 520-740 cm-1 for
AdCo6-AdCo8. The calculated corresponding values were 761,
1334, 824, and 503 cm-1, respectively. (ii) Setting the relative
intensity of the Q-band of Co0 at unity, the experimental ratios
of the oscillator strengths for Co0:AdCo2:AdCo4:AdCo6:AdCo8
were 1.00:1.15:1.72:2.09:2.14. Calculations of the corresponding
values gave 1.00:1.23:1.63:1.77:1.82 (comparison of f values
in Table 4), indicating that the effect of fused benzene decreases
the farther the benzene from the center of the molecule. (iii)
The predicted splitting (293 cm-1) of the Q-band of AdZn8 is,
as seen in Figure 9A, much larger than that (98 cm-1) of AdZn6.
After obtaining this calculated result, we checked the experi-
mental values for AdCo8 and AdCo6, and these were 353 and
237 cm-1, respectively, assuming that the energy difference
between the MCD trough and peak roughly represents the
splitting (267 cm-1 for tetra-tert-butyl CoPc17b). (iv) Although
the calculations estimate the Soret transition to lie at higher
(b) Molecular Orbital Energy Level. Figure 10 shows the
calculated energies of some frontier orbitals. The main results
may be summarized as follows. (i) The HOMO destabilizes,
but to a decreasing extent with increasing molecular size, while
the second HOMO of the macrocycle remains almost constant
(note that there are several naphthalene- or anthracene-centered
orbitals in the larger molecules, which are marked in the figure).
(ii) The HOMO energy is similar between the corresponding
opposite and adjacent isomers. (iii) The LUMO of opposite
isomers split into two, and the differences are 5150, 1640, and
2270 cm-1 for OpZn2, OpZn6, and OpZn8, respectively. Since
the Q-band is approximated as an almost pure one-electron
transition (Table 2), these differences have a parallel relationship
with the calculated splittings of the Q-band of these molecules
(1717, 561, and 728 cm-1, respectively). (iv) The splitting of
the LUMO of adjacent species is small, if it occurs at all. (v)
In agreement with the experimental fact that the Q-band of
adjacently dinaphthalene-fused Pc’s lies at shorter wavelength
than that of naphthalocyanine (Nc),17b the calculated energy
difference between the HOMO and LUMO in the former
(28 500 cm-1) is slightly larger than that of the latter (28 000
cm-1), supporting the view that the effect of fusion of the outer
benzene is smaller (note that the π system of these two species
is isomeric).
energy than experimentally observed, by ca. 4700-7900 cm-1
,
the band position is rather insensitive to the size of the
molecules, as is indeed observed (Figure 3A). (v) x- and y-axes
polarized transitions are predicted on the longer wavelength side
of the Soret band of AdZn6 at 318 and 312 nm (or 31 450 and
32 050 cm-1) and of AdZn8 at ca. 363-376 and 341-349 nm
(or 27 100 ( 500 and 29 000 ( 400 cm-1). These are transitions
involving mostly naphthalene- or anthracene-centered orbitals.
These transitions may correspond to bands at 412 nm for AdCo6
and at 495 nm for AdCo8, since the MCD signal associated
with these bands changes from plus to minus, viewing from
the longer wavelength side (note that x- and y-axes polarized
transitions in Table 4 give MCD signals of plus and minus,
respectively, experimentally).
(c) Interpretation of the Peculiarity of the Spectrum of
OpCo2 from MO Calculations. Now we have to consider the
apparent discrepancy between the experimental unsplit (Figure
4A) and predicted (by MO calculations), largely split Q-band
spectra (Table 4) of oppositely dibenzo-substituted TAPs. As
shown in our previous papers,3c,q we consider that the spectral
shift of TAP derivatives can be explained by the SAP
method.4,5,29b Lending support to this, the splitting of the Q-band
estimated by the SAP method (1495 cm-1 38-43
is not far away
)
from the calculated value (1717 cm-1) for OpZn2. Accordingly,
we have to consider much higher order perturbations in
explaining the Q-band of OpCo2. To obtain insight into this
9
J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002 8017

A R T I C L E S
Kobayashi et al.
Figure 10. Partial molecular orbital energy diagram for skeletons containing zinc. Orbitals marked by / indicate naphthalene- or anthracene-centered
orbitals. Numbers indicate orbital number.
problem, we decided to calculate the MOs including substituent
groups, although only π systems were taken into consideration
in the above calculations.
The summary of calculations is shown stepwise in Figure
11. The introduction of four alkyl (methyl) groups at the 7,8,-
(38) Since the SAP method predicts how much the Qx00- and Qy00-bands shift
from the doubly degenerate Q00-band position, we have estimated the shift
experimentally as follows. In OpCo2, four alkyl groups are linked to the
TAP skeleton at the opposite positions along the x-axis, while two
diphenylbenzo groups are fused at opposite positions along the y-axis.
Unsubstituted MgTAP shows the Q00-band at 586 nm (17 065 cm-1) in
CHCl3,38 while octaethylated MgTAP has the Q00-band at 597 nm (16 750
cm-1) in CH2Cl2.39 Taking into account that the Q-band positions of TAPs
and Pc’s are almost the same in these two solvents and that an approximate
additivity exists on the substituent effect,24,25 the shift by four alkyl groups
at opposite positions of the TAP skeletons is estimated to be ca. 158
{)(17 065 - 16 750)/2} cm-1, which corresponds to ca. 5-6 nm at around
600 nm. The substituent effect of the two p-diphenylbenzo groups can be
estimated by comparing the data of metal-free species. If the center of the
split Q-band is defined as the position of the Q-band, then that of OpH22
is at 646 nm in o-DCB. If we subtract the above contribution by four alkyl
groups, it is inferred that the Q-band of two p-diphenylbenzo-substituted
TAP lies at ca. 640 nm (15 625 cm-1). On the other hand, since the center
of the split Q-band of unsubstituted H2TAP is at 579 nm (17 278 cm-1) in
chlorobenzene,40 which is a similar solvent to o-DCB, the effect is calculated
as ca. 1653 cm-1. Although there is no absorption data on unsubstituted
CoTAP,41 tetra(cyclohexano) CoTAP, an octaalkylated CoTAP, shows a
Q-band at 591 nm (16 920 cm-1) in chlorobenzene.42 Since the substituent
effect of an octaalkyl group is 315 cm-1 from the above data on MgTAP,
and the Q-band positions of Pc’s and TAPs in chlorobenzene and toluene
are very close,24,41 the Q-band position of unsubstituted CoTAP in these
solvents is estimated to lie at 580 nm (17 235 cm-1). In this way, the two
Q
00-band positions of OpCo2 calculated by the SAP method appear to lie
at ca. 586 (17 235 - 158 ) 17 077 cm-1) and 642 nm (17 235 - 1653 )
15 582 cm-1). The splitting estimated by the SAP method is, therefore,
1495 cm-1
.
Figure 11. Calculated frontier orbital energy of the OpZn2 π skeleton,
OpZn2 substituted by four methyl groups at 7,8,17,18-positions, OpZn2
substituted by four phenyl groups at 21,24,121,124-positions, and OpZn2
substituted by four methyl groups at 7,8,17,18-positions and four phenyl
groups at 21,24,121,124-positions. Numbers below each structure indicate
the predicted Q-band position and splitting energy.
(39) Stuzhin, P. A.; Khelevina, O. G. Coord. Chem. ReV. 1996, 147, 41.
(40) Ough, E. A.; Creber, K. A. M.; Stillman, M. J. Inorg. Chim. Acta 1996,
246, 361.
(41) Linstead, R. P.; Walley, M. J. Chem. Soc. 1952, 4839.
(42) Kobayashi, N. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M.,
Guilard, R., Eds.; Academic Press: New York, 1999; Vol. 2, Chapter 13.
(43) Ficken, C. E.; Linstead, R. P. J. Chem. Soc. 1952, 4846.
9
8018 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002

Di-Aromatic Ring-Fused Phthalocyanine Derivatives
A R T I C L E S
Table 5. Calculated Transition Energies, Oscillator Strength (f),
and Configurationsa
energy/
cm-1
nm
f
pol.b
configurationsc
OpZn2Me4
14470
15800
691
633
0.888
0.757
y
x
87-88 (93)
87-89 (91)
86-89 (6)
86-88 (7)
OpZn2Ph4
14310
15850
699
631
0.955
0.893
y
x
131-132(93)
131-133(93)
128-133 (6)
128-132 (6)
OpZn2Me4Ph4
14300
15200
699
658
0.890
0.864
y
x
143-144(93)
143-145(93)
140-145 (6)
140-144 (6)
a Only Q-bands are shown. b Polarization. c Orbital numbers 87, 131, and
143 are HOMOs of OpZn2Me4, OpZn2Ph4, and OpZn2Me4Ph4, respec-
tively.
Figure 12. Four frontier orbitals of OpZn2. The positions 7, 8, 17, and
18, to which alkyl groups are linked, and the positions 21, 24, 121, and 124,
to which phenyl groups are connected, are indicated in one of the figures.
17,18-positions and of four phenyl groups at the 21,2,4121,124-
positions decreased the Q-band splitting compared to the parent
molecule (1717 cm-1) to 1328 and 1538 cm-1, respectively,
and when both the alkyl and phenyl groups were included in
the calculations, the value became nearly half (908 cm-1).44
These data suggest that the substituents do lessen the splitting
of the Q-band and that the effect of four alkyl groups is larger
than that of four phenyl groups, although generally the sub-
stituent effect of the latter group is more significant.2,24 This
inverse trend can be reasonably explained by considering the
size of the coefficient of carbons in frontier MOs in Figure 12.
As can be seen, the coefficients of carbons at the 7,8,17,18-
positions are much larger than those at 21,2,4121,124-positions
of the opposite dibenzoTAP skeleton, where four phenyl groups
are bound except in the case of the LUMO+1, indicating that
the substituent effect can appear much more sensitively at the
former four positions. This is indeed reflected in the change of
MO energy (Figure 11, top). When four phenyl groups were
introduced at 21,2,4121,124-positions of the opposite dibenzoTAP
skeleton, the energy of the four frontier orbitals changed slightly,
while linking four alkyl groups to the 7,8,17,18-positions
substantially destabilized the HOMO-1, HOMO, and LUMO,
and as a result, the LUMO and LUMO+1 levels approach each
other. Then, since more than 90% of the Q-band is composed
of the HOMO-to-LUMO and LUMO+1 transitions (Table 5),
the splitting of the Q-band also becomes smaller.
the LUMO+1 (b1u*) and LUMO+2 (b2u*). Similarly, the
corresponding band observed at 519 nm for CoITAP was
reproduced at 457 nm (21 900 cm-1).17a For OpCoI2, the split
MLCT bands were calculated at 426 (23 470 cm-1, f ) 0.571,
polarization ) y) and 383 nm (26 110 cm-1, f ) 0.941,
polarization ) x). These were almost pure one-electron transi-
tions from the HOMO-1 (b1g dπ) to LUMO+2 (au π*) and
LUMO+3 (b3u π*) orbitals, respectively, in D2h symmetry. From
the relative intensity ratio and the difference between the
observed and calculated wavelengths, these transitions appear
to correspond to two peaks at ca. 559 and 493 nm of OpCoI2
in Figure 7B. In the case of AdCoI2, MLCT transitions (mostly
from the HOMO-1 (b1 dπ) and HOMO-2 (a2 dπ) to the
LUMO+1∼4 π*) are calculated at 433 (23 100, 0.078), 400
(25 000, 0.273), 397 (25 200, 0.112), 373 (26 810, 0.170), 370
(27 030, 0.084), 346 (28 900, 0.368), and 343 (29 150, 0.183)
nm, since many transitions are allowed and can mix with π-π*
transitions in C2V symmetry. From the configuration, the
contributions of π-π* transitions to the bands estimated at 400,
397, 373, 346, and 343 nm are ca. 42, 44, 28, 46, and 25%,
respectively. The above results suggest the presence of three
peaks at ca. 430 (weak), 390-400 (medium), and 340-350
(strong) nm. These bands may correspond to an experimental
weak peak at ca. 550 nm, a medium peak at 525 nm, and an
intense peak at 458 nm for AdCoI2 in Figure 7A.
Conclusions
(d) Interpretation of the Split MLCT Band of AdCoI2 and
OpCoI2 Species. The main results of the MO calculations on
Co(I) species are summarized in Table 6. The MLCT bands
observed experimentally at 470 and ca. 425-430 nm for CoIPc
were reproduced at 415 and 381 nm (or 24 100 and 26 350
cm-1).33,36 These are transitions from the HOMO-1 (eg dπ) to
We have succeeded in preparing a series of adjacent and
opposite type di-aromatic ring-fused cobalt Pc derivatives of
varying size. The spectroscopic properties have been examined
using electronic absorption and magnetic circular dichroism
spectroscopies, together with electrochemical methods, and most
of the properties have been reproduced by MO calculations using
the ZINDO/S Hamiltonian. The adjacent isomers have been
obtained preferentially on their own by using a diphthalonitrile
unit linked via a short aryl chain. The Q-band shifts to longer
wavelength, and its intensity increases but the extent decreases
with increasing molecular size. The substituent effect caused
by fusion of benzene on the Q-band position decreases with
increasing separation of the benzene unit from the center of the
tetraazaporphyrin skeleton. Setting the magnitude of the effect
of benzene directly fused to the TAP skeleton at unity, the effect
of the second and third benzene units is roughly about 0.75-
0.80 and 0.48 ( 0.06, respectively. On ring annulation, the
HOMO destabilizes significantly, while the LUMO remains
(44) To confirm even a part of these substituent effects experimentally, we have
prepared two compounds, i.e., [21,24,121,124-tetraphenyldibenzo[b,l]-5,10,-
15,20-tetraazaporphyrinato(2-)]zinc(II) C48H28N8Zn {Mass (ESI-TOF) (m/
z): 781 ([M + 1]+). 1H NMR (400 MHz, CDCl3 + 2% C5D5N): δ 7.76
(m, 12H, phenyl m-, p-H), 8.08 (s, 4H, arom H), 8.28 (d, 8H, phenyl o-H),
8.73 (s, 4H, arom H). UV-vis (CHCl3) λmax: 339, 572, 625, 667.} and
[21,24,121,124-tetraphenyldibenzo[b,l]-7,8,17,18-tetrapropyl-5,10,15,20-tet-
raazaporphyrinato(2-)]zinc(II) C60H52N8Zn {Mass (ESI-TOF) (m/z): 949
([M + 1]+). UV-vis (CHCl3) λmax: 341, 587, 645.}. The former compound
exhibited Q-band peaks at 625 and 667 nm (splitting energy ) 1007 cm-1),
while the latter showed a single relatively broad Q-band peak at 645 nm
with a half-width of 779 cm-1 (the half-width of the Q-band at 593 nm of
tetra-tert-butylated ZnTAP in the same solvent is ca. 570 cm-1 (our
unpublished data)), which may be produced by a superimposition of closely
lying Qy00 and Qx00 bands. The splitting of the Q-band of the latter
compound appears at 360 cm-1, estimated from the energy difference
between the MCD trough (655 nm) and peak (640 nm) of the Q-band.
Thus, four alkyl groups indeed function to reduce the Q-band splitting.
9
J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002 8019

A R T I C L E S
Kobayashi et al.
Table 6. Calculated Transition Energies, Oscillator Strength (f), and Configurations of Cobalt(I) Species
-1
λ/nm
ν/cm
f
obsda
pol.b
configurationsc
assignment
CoTAP
569
569
457
457
323
323
17590
17590
21870
21870
31010
31010
0.458
0.458
0.213
0.213
0.074
0.074
624 (16030)
519 (19270)
61f63 (87)
61f62 (87)
60f64 (95)
59f64 (95)
60f65 (77)
59f65 (77)
Q
Q
MLCT
MLCT
MLCT
MLCT
y
x
x
y
56f63 (18)
56f62 (18)
OpCo2
615
542
426
383
317
16270
18440
23490
26120
31580
0.468
0.557
0.571
0.941
0.105
672 (14880)
y
x
y
x
x
79f81 (94)
79f80 (91)
78f82 (93)
78f83 (83)
77f82 (80)
Q
Q
MLCT
MLCT
MLCT
559 (17890)
493 (20280)
AdCo2
599
596
433
400
397
373
370
346
343
16710
16770
23110
25010
25200
26790
27030
28930
29170
0.588
0.567
0.078
0.273
0.112
0.170
0.084
0.368
0.183
664 (15060)
x
y
x
y
x
x
y
x
y
79f80 (84)
79f81 (90)
77f82 (65)
79f83 (42)
79f82 (44)
79f82 (28)
78f80 (24)
79f84 (46)
77f83 (38)
77f80 (7)
Q
Q
525 (19050)
458 (21830)
79f82 (26)
77f83 (24)
78f83 (33)
78f83 (25)
78f84 (24)
77f84 (23)
79f83 (25)
MLCT, π-π*
MLCT, π-π*
MLCT, π-π*
MLCT, π-π*
MLCT, π-π*
MLCT, π-π*
MLCT, π-π*
78f82 (19)
77f82 (24)
77f81 (21)
78f83 (18)
77f87 (12)
CoPc
649
649
415
415
381
381
15410
15410
24110
24110
26250
26250
0.723
0.723
0.108
0.108
0.562
0.562
708 (14120)
471 (21230)
435 (22990)
97f98 (47)
97f99 (47)
96f101 (52)
95f101 (52)
96f100 (70)
95f100 (70)
97f99 (46)
97f98 (46)
95f100 (22)
96f100 (22)
95f101 (21)
96f101 (21)
Q
Q
MLCT
MLCT
MLCT
MLCT
97f104 (16)
97f103 (16)
a Observed band wavelength (nm) and energies (cm-1) from the data reported in this paper (OpCo2 and AdCo2), in Kobayashi, N.; Nakajima, S.; Osa,
T. Chem. Lett. 1992, 2415 (CoTAP), and in Nevin, W. A.; Hempstead, M. R.; Liu, W.; Leznoff, C. C.; Lever, A. B. P. Inorg. Chem. 1987, 26, 570 (CoPc).
b Polarization. On the direction of x,y, see Figure 1. c Values in parentheses indicate the contribution (%) of the configuration. Numbers at both sides of
arrows indicate orbital numbers. CoTAP (HOMO: 61; LUMO: 62; dπ: 59, 60; dz2:58; dxy: 57), OpCo2 (79; 80; 77, 78; 76; 74), AdCo2 (79; 80; 77, 78;
76; 75), CoPc (97; 98; 95, 96; 94; 93), AdCo6 (115; 116; 113, 114; 112; 111), AdCo8 (133; 134; 131, 132; 130; 127), CoNc (133; 134; 131, 132; 130; 129).
almost constant. In the adjacently substituted series, a single
Q-band is observed, while in the oppositely substituted species,
split Q-bands are generally observed, except in the case of an
oppositely dibenzo-fused dialkylated TAP. The extent of the
splitting of the Q-band of oppositely substituted species has a
parallel relationship with the splitting of the LUMO of these
species, which in turn relates to the ratio of long to short axes
in the molecule. Thus, the larger the ratio, the larger the splitting.
The first oxidation in adjacently and oppositely dibenzo-fused
CoTAP occurs at the cobalt and ligand, respectively. A small
splitting of the Q-band of an oppositely dibenzo-fused alkylated
TAP and split MLCT bands observed for two dibenzo-
substituted CoITAP are reasonably explained in terms of MO
calculations.
Supporting Information Available: Tables of crystal data and
structure refinement, atomic coordinates and equivalent isotropic
displacement parameters, bond lengths and angles, and aniso-
tropic displacement parameters for OpCo2; calculated and
observed isotropic distribution patterns of the mass spectra of
all cobalt complexes; and band-fitting parameters for the spectra
of Co0, AdCo2, AdCo4, AdCo6, and AdCo8 in toluene (PDF).
This material is available free of charge via the Internet at http://
pubs.acs.org. CCDC 180877 contains the supplementary crystal-
lographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre, 12 Union
Rd., Cambridge CB2 1EZ, UK; deposit@ccdc.cam.uk).
Acknowledgment. This research was supported by the Daiwa
JA0123812
Anglo-Japanese Foundation.
9
8020 J. AM. CHEM. SOC. VOL. 124, NO. 27, 2002