Organometallic Chemistry of Azuliporphyrins: Synthesis, Spectroscopy, Electrochemistry, and Structural Characterization of Nickel(II), Palladium(II), and Platinum(II) Complexes of Azuliporphyrins

Article abstract of DOI:10.1021/ic030166b

Four azuliporphyrins, two meso-unsubstituted and two meso-tetraaryl substituted, were investigated in the synthesis of novel organometallic compounds. The meso-unsubstituted or etio series azuliporphyrins 8 reacted with nickel-(II) acetate, palladium(II) acetate, and platinum(II) chloride in DMF to give the corresponding chelates 14-16, where the metal cation lies within the macrocyclic cavity and binds to all three nitrogens and the internal carbon atom. The newly available meso-tetraarylazuliporphyrins 13 similarly afforded the corresponding nickel(II), palladium-(II), and platinum(II) complexes, 17-19, respectively. The new organometallic complexes are stable nonpolar compounds and were fully characterized spectroscopically and by mass spectrometry. The UV-vis data indicate that these complexes, in common with the parent azuliporphyrin system 8, do not possess porphyrin-type aromaticity. However, electron donation from the azulene unit can give rise to dipolar resonance contributors that provide a degree of carbaporphyrin-type aromatic character. The platinum(II) azuliporphyrins 16 gave noteworthy proton NMR spectra where the meso-protons showed satellite peaks due to transannular coupling to platinum-195. The pyrrolic protons of the platinum(II) meso-tetraarylazuliporphyrin 19b also showed similar satellite peaks due to coupling from the platinum-195 isotope. The electrochemistry of free base tetraphenylazuliporphyrin 13a and the related nickel(II) and palladium(II) complexes was investigated using cyclic voltammetry, and these data indicate that metal coordination improves the reversibility of the ligand-based oxidations. Nickel(II) azuliporphyrin 14a and palladium-(11) tetrakis(4-chlorophenyl)azuliporphyrin 18b were also structurally characterized by X-ray crystallography. The macrocyclic core of the palladium(II) complex 18b was significantly more planar than the nickel(II) derivative 14b, and this difference was attributed to the better size match between the azuliporphyrin cavity and the larger palladium-(II) ion. The straightforward synthesis of metalloazuliporphyrins under mild conditions, and their interesting spectroscopic, electrochemical, and structural features, demonstrates that the azuliporphyrin system holds great promise as a platform for organometallic chemistry.

Full text of DOI:10.1021/ic030166b

Inorg. Chem. 2003, 42, 7326−7338
Organometallic Chemistry of Azuliporphyrins: Synthesis, Spectroscopy,
Electrochemistry, and Structural Characterization of Nickel(II),
Palladium(II), and Platinum(II) Complexes of Azuliporphyrins†
Timothy D. Lash,* Denise A. Colby, Shelley R. Graham, Gregory M. Ferrence, and Lisa F. Szczepura
Department of Chemistry, Illinois State UniVersity, Normal, Illinois 61790-4160
Received May 16, 2003
Four azuliporphyrins, two meso-unsubstituted and two meso-tetraaryl substituted, were investigated in the synthesis
of novel organometallic compounds. The meso-unsubstituted or “etio” series azuliporphyrins 8 reacted with nickel-
(II) acetate, palladium(II) acetate, and platinum(II) chloride in DMF to give the corresponding chelates 14−16,
where the metal cation lies within the macrocyclic cavity and binds to all three nitrogens and the internal carbon
atom. The newly available meso-tetraarylazuliporphyrins 13 similarly afforded the corresponding nickel(II), palladium-
(II), and platinum(II) complexes, 17−19, respectively. The new organometallic complexes are stable nonpolar
compounds and were fully characterized spectroscopically and by mass spectrometry. The UV−vis data indicate
that these complexes, in common with the parent azuliporphyrin system 8, do not possess porphyrin-type aromaticity.
However, electron donation from the azulene unit can give rise to dipolar resonance contributors that provide a
degree of carbaporphyrin-type aromatic character. The platinum(II) azuliporphyrins 16 gave noteworthy proton NMR
spectra where the meso-protons showed satellite peaks due to transannular coupling to platinum-195. The pyrrolic
protons of the platinum(II) meso-tetraarylazuliporphyrin 19b also showed similar satellite peaks due to coupling
from the platinum-195 isotope. The electrochemistry of free base tetraphenylazuliporphyrin 13a and the related
nickel(II) and palladium(II) complexes was investigated using cyclic voltammetry, and these data indicate that metal
coordination improves the reversibility of the ligand-based oxidations. Nickel(II) azuliporphyrin 14a and palladium-
(II) tetrakis(4-chlorophenyl)azuliporphyrin 18b were also structurally characterized by X-ray crystallography. The
macrocyclic core of the palladium(II) complex 18b was significantly more planar than the nickel(II) derivative 14b,
and this difference was attributed to the better size match between the azuliporphyrin cavity and the larger palladium-
(II) ion. The straightforward synthesis of metalloazuliporphyrins under mild conditions, and their interesting
spectroscopic, electrochemical, and structural features, demonstrates that the azuliporphyrin system holds great
promise as a platform for organometallic chemistry.
Introduction
under mild conditions, and these porphyrin isomers also show
some promise in the stabilization of unusual oxidation
states.2,4 NCPs react as “dianionic ligands” (cross-conjugated
tautomer 1a, Chart 1 ) with nickel(II) or copper(II) acetate
under mild conditions to generate the cross-conjugated metal-
(II) derivatives 2a and 2b.5,6 Alternatively, NCPs can behave
The activation of C-H bonds toward metalation has
important industrial applications and is a topic of great
current interest.1 In addition, stable organometallic systems
may have unusual chemical and spectroscopic properties.2
The N-confused porphyrins (NCPs; e.g., 1)2,3 have emerged
as a superior system for generating organometallic derivatives
(3) (a) Furuta, H.; Asano, T.; Ogawa, T. J. Am. Chem. Soc. 1994, 116,
767. (b) Chmielewski, P. J.; Latos-Grazynski, L.; Rachlewicz, K.;
Glowiak, T. Angew. Chem., Int. Ed. Engl. 1994, 33, 779. (c) Liu, B.
Y.; Bru¨ckner, C.; Dolphin, D. Chem. Commun. 1996, 2141. (d) Geier,
G. R., III; Haynes, D. M.; Lindsey, J. S. Org. Lett. 1999, 1, 1455. (e)
Lash, T. D.; Richter, D. T.; Shiner, C. M. J. Org. Chem. 1999, 64,
7973.
* Author to whom correspondence should be addressed. E-mail:
tdlash@ilstu.edu.
† Conjugated Macrocycles Related to the Porphyrins. 29. Part 28: Lash,
T. D.; Colby, D. A.; Ferrence, G. M. Eur. J. Org. Chem., in press.
(1) (a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H.
Acc. Chem. Res. 1995, 28, 154. (b) Shilov, A. E.; Shul’pin, G. B.
Chem. ReV. 1997, 97, 2879.
(4) Furuta, H.; Ogawa, T.; Uwatoko, Y.; Araki, K. Inorg. Chem. 1999,
38, 2676.
(2) Furuta, H.; Maeda, H.; Osuka, A. Chem. Commun. 2002, 1795.
7326 Inorganic Chemistry, Vol. 42, No. 22, 2003
10.1021/ic030166b CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/09/2003

Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
derivative.9 Anaerobic reaction of NCP 1 with ferrous
bromide gave a complex with an agostic η2 CH interaction,10
while reactions with MnBr2 gave a similar complex that
readily oxidized to give the manganese(III) derivative 2d.11
Finally, [Rh(CO)2Cl]2 reacts with 1 to give inner core
coordination of a Rh(I) at two of the interior nitrogens with
outer core coordination to a second Rh(I) at the macrocyclic
periphery.12
Chart 1
Given the wealth of organometallic and coordination
chemistry that is associated with the NCPs,2 it is surprising
that related carbaporphyrinoid systems initially received very
little attention.13,14 However, organometallic derivatives of
true carbaporphyrins (e.g., silver(III) derivatives 4),15,16
oxacarbaporphyrins (nickel(II) and palladium(II) complexes
5),17 oxybenziporphyrins (palladium derivatives, e.g., 6),18
oxaoxybenziporphyrins (palladium(II) complex 7),19 and
benziporphyrins (palladium and platinum derivatives)20 have
recently been described. In addition, we have recently
demonstrated that azuliporphyrins 8 possess a CNNN
coordination core that is well suited to the production of
related organometallic species.21,22
Azuliporphyrins 8 (Scheme 1) are porphyrin analogues
where one of the pyrrole rings has been replaced by an
azulene unit.23,24 They are cross-conjugated systems, and for
this reason the free base form does not exhibit the typical
aromatic characteristics associated with the porphyrins.23 The
UV-vis spectra for azuliporphyrins do not show strong Soret
bands near 400 nm, as would be expected for an aromatic
system of the porphyrin family,25 and only broad ill-defined
(10) Chen, W.-C.; Hung, C. H. Inorg. Chem. 2001, 40, 5070.
(11) Bohle, D. S.; Chen, W.-C.; Hung, C.-H. Inorg. Chem. 2002, 41, 3334.
(12) Srinivasan, A.; Furuta, H.; Osuka, A. Chem. Commun. 2001, 1666.
(13) (a) Hayes, M. J.; Spence, J. D.; Lash, T. D. Chem. Commun. 1998,
2409. (b) Lash, T. D.; Muckey, M. A.; Hayes, M. J.; Liu, D.; Spence,
J. D.; Ferrence, G. M. J. Org. Chem., in press.
(14) (a) Lash, T. D. Synlett 2000, 279. (b) Lash, T. D. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: San Diego, 2000; Vol. 2, pp 125-199.
(15) (a) Muckey, M. A.; Szczepura, L. F.; Ferrence, G. M.; Lash, T. D.
Inorg. Chem. 2002, 41, 4840. (b) Lash, T. D.; Hayes, M. J.; Spence,
J. D.; Muckey, M. A.; Ferrence, G. M.; Szczepura, L. F. J. Org. Chem.
2002, 67, 4860. (c) Liu, D.; Lash, T. D. J. Org. Chem. 2003, 68, 1755.
(16) Lash, T. D.; Colby, D. A.; Muckey, M. A.; Liu, D.; Ferrence, G. M.
Abstracts of Papers, 225th National Meeting of the American Chemical
Society, New Orleans, LA; American Chemical Society: Washington,
DC, 2003; INOR 672.
(17) Liu, D.; Lash, T. D. Chem. Commun. 2002, 2426.
(18) (a) Stepien, M.; Latos-Grazynski, L.; Lash, T. D.; Szterenberg, L.
Inorg. Chem. 2001, 40, 6892. (b) Lash, T. D. Angew. Chem., Int. Ed.
Engl. 1995, 34, 2533. (c) Lash, T.D.; Chaney, S. T.; Richter, D. T. J.
Org. Chem. 1998, 63, 9076. (d) Richter, D. T.; Lash, T. D. Tetrahedron
2001, 57, 3659.
as “trianionic ligands” (fully aromatic tautomer 1b) in
reactions with silver(I) acetate to afford the silver(III)
complex 3a.4 A similar antimony(V) complex 3b with two
axial methoxy ligands has also been reported.7 Reaction of
1 with palladium(II) acetate can give the palladium(II)
complex 2c, but under some conditions dimeric products with
additional C-Pd bonds to the phenyl substituents are
produced.8 Zinc acetate coordinates with the three nitrogens
from the NCP core and a molecule of pyridine, but X-ray
crystallography suggests that there is an additional side-on
η1-type interaction to the internal carbon atom.9 Similar
interactions can also be observed in a dimeric acetate
(19) Venkatraman, S.; Anand, V. G.; Pushpan, S. K.; Sankar, J.; Chan-
drashekar, T. K. Chem. Commun. 2002, 462.
(20) Stepien, M.; Latos-Grazynski, L. Chem. Eur. J. 2001, 7, 5113.
(21) Preliminary communication: Graham, S. R.; Ferrence, G. M.; Lash,
T. D. Chem. Commun. 2002, 894.
(22) These results were presented, in part, at the following meetings: (a)
221st National Meeting of the American Chemical Society, San Diego,
CA, April 2001 (Graham, S. R.; Lash, T. D. Abstracts of Papers,
ORGN 186); (b) 2nd International Conference on Porphyrins and
Phthalocyanines (ICPP-2), Kyoto, Japan, July 2002 (Lash, T. D. Book
of Abstracts, Abstract No. S-76); (c) 225th National Meeting of the
American Chemical Society, New Orleans, LA, March 2003 (Lash,
T. D.; Colby, D. A.; Graham, S. R.; Ferrence, G. M. Abstracts of
Papers, INOR 673).
(5) Chmielewski, P. J.; Latos-Grazynski, L.; Schmidt, I. J. Am. Chem.
Soc. 1996, 118, 5690.
(6) Chmielewski, P. J.; Latos-Grazynski, L.; Schmidt, I. Inorg. Chem.
2000, 39, 5475.
(7) Ogawa, T.; Furuta, H.; Morino, A.; Takahashi, M.; Uno, H. Organomet.
Chem. 2000, 611, 551.
(8) (a) Furuta, H.; Kubo, N.; Maeda, H.; Ishizuka, T.; Osuka, A.; Nanami,
H.; Ogawa, T. Inorg. Chem. 2000, 39, 5424. (b) Furuta, H.; Maeda,
H.; Osuka, A.; Yasutake, M.; Shinmyozu, T.; Ishikawa, Y. Chem.
Commun. 2000, 1143.
(23) Lash, T. D.; Chaney, S. T. Angew. Chem., Int. Ed. Engl. 1997, 36,
839.
(9) Furuta, H.; Ishizuka, T.; Osuka, A. J. Am. Chem. Soc. 2002, 124, 5622.
(24) Lash, T. D. Chem. Commun. 1998, 1683.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7327

Lash et al.
Scheme 1
through analogous tropylium-fused carbaporphyrin forms as
illustrated by the hybrid structure 11.23 In TFA-CDCl3, the
proton NMR spectrum of 8 shows the meso-protons at 9.42
and 9.95 ppm, while the interior CH resonates at -2.56
ppm.23 The UV-vis spectrum of the dication also becomes
substantially more porphyrin-like showing two Soret-like
absorptions at 364 and 460 ppm.23
Azuliporphyrins 8 can easily be synthesized by two
different versions of the MacDonald “3 + 1” condensa-
tion.23,26,27 The azuliporphyrin system was first reported by
our group in 199723 and has been shown to have unique
chemical properties, specifically in its ability to undergo an
oxidative ring contraction to afford benzocarbaporphyrins
12 (Scheme 1).24 Recently, we also reported a one-pot
synthesis of meso-tetraarylazuliporphyrins from azulene,
pyrrole, and arylaldehydes under Lindsey-type Rothemund
reaction conditions.28-30 This chemistry makes the azulipor-
phyrin system readily available for the first time and has
facilitated more detailed studies into the chemistry of these
important porphyrin analogues. In this paper, we report full
details on the synthesis and spectroscopy of nickel(II),
palladium(II), and platinum(II) azuliporphyrins.21,22 In ad-
dition, structural characterizations of two organometallic
derivatives and preliminary electrochemical studies have been
performed.
Results and Discussion
The cross-conjugated azuliporphyrin system structurally
resembles the nonaromatic tautomer 1a of the N-confused
porphyrins31 and for this reason might be expected to undergo
similar metal insertion reactions. Indeed, shortly after we
first reported the synthesis of azuliporphyrin 8a, Ghosh and
co-workers performed a DFT study on this system and noted
that it should be well suited for metalation.32 Initially, we
reacted azuliporphyrin 8a with nickel(II) acetate in refluxing
chloroform-methanol, but this produced only low yields of
the related nickel(II) complex 14a. However, when the
chemistry was carried out in DMF at 80-90 °C, 14a was
produced in good yields after 10 min. Following chroma-
tography on silica gel eluting with chloroform, and crystal-
lization from chloroform-hexanes, the chelate was isolated
in 64% yield. The metallo derivative was stable to air and
water, and was relatively nonpolar as judged by TLC (Rf
value) and column chromatography compared to the free base
azuliporphyrin 8a. The diphenyl porphyrinoid 8b reacted
similarly to give the nickel(II) complex in 73% yield. Both
metal complexes gave complex UV-vis spectra (Figure 1A)
showing a moderately strong band at 385 nm in the case of
absorptions are observed through the visible region instead
of porphyrin-type Q bands.23 On the other hand, the proton
NMR spectrum for 8 in CDCl3 gave resonances for the two
types of meso-protons that were somewhat shifted downfield
to ca. 8.0 and 9.0 ppm.23 While these values are nowhere
near the shifts observed for true porphyrins, which show
these resonances near 10 ppm, the data suggest that azuli-
porphyrins have a significant diatropic ring current.14 In
addition, this proposal is supported by the observation that
the internal CH resonates upfield at +1.5 ppm, although this
is a pale shadow of the shifts observed for aromatic
carbaporphyrins where the CH resonance is commonly seen
at -7 ppm.25 The weak diatropic character observed for 8
was attributed to contributions from dipolar resonance forms
such as 9 that simultaneously give the structure 18π electron
aromatic character and external tropylium characteristics.23
Nonetheless, this contribution is limited due to the associated
charge separation which restricts the degree of aromatic
character for azuliporphyrins. However, addition of acid
“switches on” a strong diatropic ring current by generating
a diprotonated dication 10 that favors charge delocalization
(26) Lash, T. D. Chem. Eur. J. 1996, 2, 1197.
(27) Graham, S. R.; Colby, D. A.; Lash, T. D. Angew. Chem., Int. Ed.
2002, 41, 1371.
(28) Colby, D. A.; Lash, T. D. Chem. Eur. J. 2002, 8, 5397.
(29) Colby, D. A.; Lash, T. D. Book of Abstracts for the 2nd International
Conference on Porphyrins and Phthalocyanines (ICPP-2), Kyoto,
Japan, June 30 to July 5, 2002; Abstract No. P-247.
(30) See also: Colby, D. A.; Lash, T. D. J. Org. Chem. 2002, 67, 1031.
(31) Furuta, H.; Ishizuka, T.; Osuka, A.; Dejima, H.; Nakagawa, H.;
Ishikawa, I. J. Am. Chem. Soc. 2001, 123, 6207.
(25) Lash, T. D.; Hayes, M. J. Angew. Chem., Int. Ed. Engl. 1997, 36,
(32) Ghosh, A.; Wondimagegn, T.; Nilsen, H. J. J. Phys. Chem. B 1998,
102, 10459.
840.
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Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
ening, possibly due to aggregation in solution, although the
meso-protons were much better resolved at higher temper-
atures. However, the meso-protons for 14a in d5-pyridine
gave sharp, well-resolved resonances that were further shifted
downfield to give values of 8.9 and 9.6 ppm (the analogous
resonances for 8a in d5-pyridine were previously observed
at 8.6 and 9.5 ppm23). In addition, the porphyrinoid methyl
groups in 14a gave rise to a 6H singlet at 3.07 ppm, which
compares to values for 8a of 3.0 ppm in CDCl3 and 3.1 ppm
in d5-pyridine. Pyridine may aid in stabilizing the dipolar
canonical forms for azuliporphyrins and their metallo deriva-
tives and thereby enhance the diatropic character for this
system. In any case, the data indicate that the degree of
macrocyclic aromaticity in 14a is slightly enhanced compared
to the parent system 8a. Similar results were obtained for
the diphenyl-substituted azuliporphyrin chelate 14b. How-
ever, this latter derivative was more soluble and this allowed
the carbon-13 NMR spectrum to be obtained. Unfortunately,
as is the case for all of the reported metalloazuliporphyrins
in this paper, we were unable to identify the internal carbon
in the carbon-13 NMR spectra. However, the data does
demonstrate that the macrocycle has a plane of symmetry
and the two types of meso-carbons gave resonances at 99.9
and 108.5 ppm, values that are similar to those observed for
the free base azuliporphyrins 8.
Palladium(II) acetate was found to react with azulipor-
phyrins 8 under the same conditions to afford the related
palladium(II) derivatives 15. The UV-vis spectra of the
palladium chelates (Figure 1B) were quite different from the
nickel complexes 14 and showed three bands in the range
of 360-450 nm, together with broad absorptions from 500
to 800 nm. As was the case for the nickel(II) complexes,
the diphenyl derivative 15b showed small bathochromic
shifts compared to 15a. The palladium(II) complexes were
also only sparingly soluble in CDCl3, and the proton NMR
spectra for 15 in this solvent gave highly broadened
resonances for the meso-protons. Again, these signals
sharpened up somewhat at higher temperatures. In addition,
the proton NMR spectrum of 15a in d5-pyridine showed the
meso-protons as two well-defined 2H singlets at 9.02 and
9.78 ppm, values that suggest a further enhancement of the
macrocyclic ring current in the palladium chelates compared
to 8 and 14. This hypothesis is further supported by the
observation that the porphyrinoid methyl units are also shifted
slightly downfield to 3.2 ppm (6H, s). We speculate that the
palladium(II) ion is a better fit for the macrocyclic cavity
and this allows the azuliporphyrin to take on a more planar
conformation for 15 compared to 14. Structural evidence to
support this proposal is provided below. As was the case
for the nickel(II) chelates, carbon-13 NMR data could only
be obtained for the diphenyl-substituted azuliporphyrin
complex 15b. This confirmed the presence of a plane of
symmetry and showed the meso-carbons at 100.7 and 110.7
ppm. High-resolution mass spectrometry also confirmed the
molecular formulas for these organometallic species.
Figure 1. UV-vis absorption spectra of metalloazuliporphyrins in
chloroform: (A) nickel(II) complex 14b; (B) palladium(II) complex 15b;
(C) platinum(II) complex 16b.
14a and broad absorptions through the visible region. The
nickel(II) diphenylazuliporphyrin 14b showed slightly red
shifted absorptions but otherwise closely resembled 14a by
UV-vis spectroscopy. Mass spectrometry confirmed that
nickel had been incorporated into the macrocycle, and the
spectroscopic data were fully consistent with the proposed
organometallic derivatives 14. Nickel complex 14a was only
sparingly soluble, but it was possible to obtain a proton NMR
spectrum in CDCl3. The meso-protons were observed as two
2H singlets at 8.5 and 9.1 ppm, values that are slightly
downfield from those reported for free base azuliporphyrin
8a in CDCl3. These resonances showed considerable broad-
Reaction of 8a or 8b with platinum(II) chloride gave lower
yields (23-27%) of the platinum(II) complexes 16. The best
results were still obtained in DMF, and reactions in ben-
Inorganic Chemistry, Vol. 42, No. 22, 2003 7329

Lash et al.
zonitrile afforded only low yields of the metalloporphy-
rinoids. The UV-vis spectra for the platinum(II) derivatives
16 (Figure 1C) were rather different from the nickel(II) or
palladium(II) complexes showing a strong band at 367 nm
for 16a, and 372 nm for 16b, together with a series of broad
ill-defined absorptions from 400 to 800 nm. Once again, the
bands for the diphenyl derivative 16b were shifted to slightly
longer wavelengths than 16a. A closer examination of the
UV-vis spectra for 14, 15, and 16 (Figure 1) indicates that
the same absorptions are present in each case, but they
nonetheless vary considerably in broadness and relative
intensity. The proton NMR spectrum for 16a in CDCl3-d5-
pyridine showed the meso-protons at 8.86 and 9.37 ppm,
values that suggest a slight decrease in the overall aromaticity
compared to 14a and 15a. The NMR spectra for both 16a
and 16b showed satellite peaks for the meso-protons (Figure
2) due to coupling from the isotope platinum-195 (natural
abundance 33.8%). This transannular coupling constant is
4
significant falling into the range of 4.4-5.6 Hz. The JPt,H
values for the 5,20-protons were consistently ca. 25% larger
than those for the 10,15-protons. Due to solubility problems,
only a poor quality carbon-13 NMR spectrum could be
obtained for 16b, but this showed values for the meso-
carbons (98.6, 110.3) similar to those reported above for 14b
and 15b.
Attempts to react azuliporphyrins 8 with silver(I) acetate
in refluxing DMF gave low yields of silver(III) carbapor-
phyrins. In control experiments, azuliporphyrins 8 were found
to slowly produce benzocarbaporphyrins 12 in refluxing
DMF, although not in synthetically useful yields, and silver-
(I) acetate does not appear to play a significant role in
producing the ring-contracted products. As carbaporphyrins
have previously been shown to incorporate silver(III) ions
in reactions with silver(I) acetate, the formation of silver-
(III) carbaporphyrins is to be expected.15 Reactions of 8 with
copper(II) acetate also readily produce metallo derivatives,
but in this case the chemistry is not straightforward and
further investigations will be required.
Recently, we reported a straightforward methodology for
synthesizing meso-tetraarylazuliporphyrins 13 (Scheme 2).28,29
The availability of these new meso-substituted porphyrinoids
has allowed us to extend the metalation chemistry, specifi-
cally to the tetraphenyl- and tetrakis(4-chlorophenyl)azuli-
porphyrins 13a and 13b, respectively. Azuliporphyrins 13
reacted with nickel(II) or palladium(II) acetate in DMF to
give the metallo derivatives 17 and 18 in 65-97% yield.
Platinum(II) chloride also reacted with azuliporphyrins 13
but, as had been the case in the meso-unsubstituted series,
the related platinum(II) chelates could only be isolated in
relatively poor yields (22-23%). The UV-vis spectra for
the metallo derivatives were quite varied (Figure 3), and also
differed somewhat from their meso-unsubstituted counter-
parts 14-16 as well. The tetraphenyl and tetrakis(4-chlo-
rophenyl) series of metalloporphyrinoids showed very similar
UV-vis spectra, and only the latter “b” series will be
discussed in this section. Nickel(II) complex 17b gave a
strong band at 400 nm, two broader absorption at 473 and
490 nm, and weaker broadened bands from 590 to 800 nm.
Figure 2. Partial 400 MHz proton NMR spectrum of the downfield region
for the platinum(II) azuliporphyrin 16b in d5-pyridine-CDCl3. The meso-
proton resonances at 9.09 and 9.43 ppm have been expanded to show the
195Pt satellite peaks. Signals labeled with an asterisk (*) correspond to solvent
impurities.
In contrast, palladium(II) derivative 18b gave three strong
bands at 374, 403, and 482 nm, and weaker broad bands
between 580 and 800 nm. The platinum(II) complex 19b
more closely resembled the nickel complex, showing a strong
band at 383 nm, two weaker bands at 444 and 466 nm, and
the same type of weaker broadened absorptions from 560 to
800 nm. The platinum(II) complexes 19 gave UV-vis
spectra that more closely resembled their “etio” counterparts
16 than was the case for the nickel(II) or palladium(II)
complexes.
7330 Inorganic Chemistry, Vol. 42, No. 22, 2003

Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
Scheme 2
The proton NMR spectra for the tetrakis(4-chlorophenyl)-
azuliporphyrin complexes 17b, 18b, and 19b (Figure 4) were
far better resolved than the corresponding tetraphenylazuli-
porphyrin derivatives, and for this reason the data for the
“b” series will be discussed in detail. The nickel(II) complex
in CDCl3 showed the meso-protons as a 2H singlet at 7.97
ppm and two 2H doublets at 8.02 and 7.8 ppm (the latter
overlaps with the resonances due to the ortho-protons on
the aryl substituents). For the palladium(II) complex 18b,
these values are observed at 7.97, 8.04, and 7.92 ppm, while
the platinum(II) derivative showed these resonances at 7.99,
7.94, and 7.91. The values fall too close together to make
any real distinctions between the diatropic character for these
chelates. However, the azulene protons vary to a greater
extent. Nickel(II) complex 17b gives a 2H triplet at 6.91, a
1H triplet at 7.21, and a 2H doublet at 7.43 ppm. These
resonances are observed at 6.84, 7.16, and 7.45 ppm for 18b,
while the platinum(II) complex 19b gives values of 6.66,
7.26, and 7.43 ppm. The 1H triplet should provide the best
indication of the electronic character for the azulene unit, as
the 23-proton is furthest removed from the remaining
porphyrinoid π-system. These data indicate that the platinum
complex takes on the greatest amount of tropylium character,
while the palladium derivative has the least. However, it is
worth noting that the 2H azulene triplet in the platinum
complex is shifted the most upfield to 6.62 ppm, possibly
indicating that the conformation of 19b induces a greater
amount of shielding at this position due to the orientation of
the adjacent aryl substituent. The pyrrolic protons for the
Figure 3. UV-vis absorption spectra of tetrakis(4-chlorophenyl)azuli-
porphyrin chelates in chloroform: (A) nickel(II) complex 17b; (B)
palladium(II) complex 18b; (C) platinum(II) complex 19b.
platinum(II) complex also show satellite peaks due to
coupling from platinum-195. Again the coupling constants
for this transannular interaction are significant (ca. 5 Hz).
In order to gain further insights into the properties of these
metallo derivatives, preliminary electrochemical studies were
conducted on the free base tetraphenylazuliporphyrin 13a
and its nickel(II) and palladium(II) derivatives, 17a and 18a,
respectively. The cyclic voltammogram of 13a is shown in
Figure 5; this scan was initiated at the open circuit potential
and scanned between the limits of -1.9 and +1.5 V vs Ag/
AgNO3. Starting at -0.4 V and scanning in the negative
direction, there are two quasi-reversible cathodic waves at
E1/2 ) -1.15 and -1.68 V. After switching the potential at
-1.9 V and continuing to scan in a positive direction, five
oxidative waves, one irreversible wave at Ep,a ) -0.24 V
Inorganic Chemistry, Vol. 42, No. 22, 2003 7331

Lash et al.
Figure 5. Cyclic voltammogram (200 mV/s) of 13a in anhydrous
dichloromethane, 0.2 M Bu4NBF4.
through the reductive wave at -1.68 V, indicating that it
must be due to a decomposition product. While the first two
oxidative waves look irreversible in Figure 5, they appear
as quasi-reversible waves when scanning was started at -0.4
V and reversed at +1.0 V, instead of +1.7 V. Notably, the
cyclic voltammogram of 13a is similar to that of the
previously reported free base carbaporphyrin 12a15b in that
both display more complex redox behavior than the well
studied H2TPP and H2OEP.33 Specifically, both 13a and 12a
contain two reductive waves and numerous oxidative waves.15b
However, there are also some significant differences between
13a and 12a, as would be expected for these rather different
carbaporphyrinoid systems (for instance, 12a shows a far
greater degree of aromatic character than 13a). (1) The
difference between the two reductive waves of 13a is ∆E1/2
) 0.53 V, which is larger than the difference between the
reductive waves for porphyrins and metalloporphyrins (∆E1/2
) 0.42 ( 0.05 V) and for the free base carbaporphyrin 12a
(∆E1/2 ) 0.35 V).15b (2) All of the oxidative waves in 13a
appear to be quasi-reversible, which is not the case for 12a.
ox
red
(3) The HOMO-LUMO gap for 13a is E1/2 - E1/2
)
-
ox
1.49 V, whereas the gap for carbaporphyrin 12a is E1/2
E1/2red ) 2.17 V. The HOMO-LUMO gap has been shown
to be dependent on a variety of factors including the
substituents on the ring and the planarity of the ring, so given
the differences in aromatic character between 13a and 12a
it is not surprising that these values are different.
The cyclic voltammogram of palladium(II) complex 18a
displays one irreversible reductive wave at Ep,c ) -1.15 V,
one irreversible oxidative wave at -0.14 V, and two
reversible oxidative waves at E1/2 ) +0.46 and +1.01 V
when scanned in a similar manner as 13a (Figure 6a).
Switching potential experiments show that the Ep,a at -0.14
V appears only after scanning through the reductive couple
at -1.15 V. Therefore, this peak is assigned to a decomposi-
tion product. Only a few studies that focus on the electro-
chemistry of palladium porphyrin complexes have been
reported to date.33 Of these, Pd(TPP) and Pd(OEP) were
reported to contain four waves: two reversible reductive
waves and two reversible oxidative waves. We observed two
Figure 4. 400 MHz proton NMR spectrum of tetrakis(4-chlorophenyl)-
azuliporphyrin chelates in CDCl3: (A) nickel(II) complex 17b; (B)
palladium(II) complex 18b; (C) platinum(II) complex 19b. In the spectrum
for 19b, the 195Pt satellite peaks for the pyrrolic protons are clearly evident
between 7.9 and 8.0 ppm.
and four quasi-reversible waves at E1/2 ) +0.34, +0.70,
+0.96, and +1.30 V, are observed (scanning out further to
+1.7 V did not reveal any additional waves). Switching
potential experiments verified that the irreversible oxidative
wave (Ep,a ) -0.24 V) is only observed after scanning
(33) Kadish, K. M.; van Caemelbecke, E.; Royal, G. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: San Diego, 2000; Vol. 8, pp 1-114.
7332 Inorganic Chemistry, Vol. 42, No. 22, 2003

Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
appear irreversible). Notably, the HOMO-LUMO gap of
ox
red
17a (E1/2 - E1/2 ) 1.62 V) is also similar to the free
base azuliporphyrin 13a. Due to the fact that the nickel(II)
center can be oxidized to nickel(III) or reduced to nickel(I)
within a narrow potential range, the electrochemical studies
of nickel porphyrin complexes are more complex than those
of palladium. Numerous studies focusing on the electro-
chemistry of nickel porphyrin complexes have been reported,
and many have incorporated spectroscopic studies to help
investigate the nature of the oxidized and reduced prod-
ucts.33,34 We have not collected any spectro-electrochemical
data. However, we do believe that the reversible waves at
E1/2 ) 0.41 and 0.86 V are ligand-centered oxidations, on
the basis of the fact that these waves do not shift dramatically
compared to the palladium(II) complex 18a or the free base
azuliporphyrin 13a. Thus, we propose that at least one of
the additional oxidative waves seen in the cyclic voltam-
mogram of 17a is due to a metal-centered redox process,
i.e., a Ni(III)/(II) couple. These assignments are consistent
with previous electrochemical reports on nickel(II) porphyrin
complexes.
It is interesting to note that metal coordination by 13a
appears to improve the reversibility of the ligand-based
oxidations. This is not the case with H2TPP and H2OEP
where all four redox processes (two oxidative and two
reductive) are reversible before and after metal coordination.
The loss of protons upon coordination is likely to be partially
responsible for increasing the reversibility of the oxidation
couples in 17a and 18a. However, the proposed increase in
aromatic character for the metal complexes compared to the
free base azuliporphyrins may also be affecting the reactivity
of the oxidized metal complexes.
Further insights into the structures of nickel(II) azulipor-
phyrin 14b and palladium(II) tetrakis(4-chlorophenyl)azu-
liporphyrin 18b were obtained by single-crystal X-ray
diffraction analysis. Both represent the first structurally
characterized azuliporphyrin complexes. Crystal data and a
summary of the intensity data and collection parameters for
these structures are given in Table 1, and ORTEP III
illustrations and selected bond lengths and angles summariz-
ing the coordination spheres of the metals are given in
Figures 7 and 8.
In the case of 14b, the macrocycle is significantly distorted
from planarity (Figure 7) as evidenced by the pyrrole to mean
[18]annulene plane dihedral angles of 14.3(1)°, 16.8(1)°, and
19.9(1)°, and the azulene to mean [18]annulene plane
dihedral angle of 15.0(1)°. The nickel(II) ion is essentially
situated over the center of the macrocyclic cavity and draws
the macrocycle into a bowl with the nickel atom slightly
above the C(21), N(22), N(23), N(24) plane. The dihedral
angle between the azulene plane and the pyrrole N(23) plane
is 34.8(1)°, and the dihedral angle between the pyrrole N(22)
and pyrrole N(24) planes is 30.8(2)°. These parameters in
conjunction with the distances (0.327 Å rms) at which
skeletal atoms lie from the plane defined by Ni(1)C(21)N-
Figure 6. Cyclic voltammograms (200 mV/s) of the Pd (a, 18a) and Ni
(b, 17a) complexes of azuliporphyrin in anhydrous dichloromethane, 0.2
M Bu4NBF4.
oxidative waves, but only one reductive wave within the
limits scanned (+1.7 V to -1.9 V vs Ag/AgNO3). The ∆Ep
for the reversible processes are comparable to the ∆Ep of
ferrocene run under similar conditions, indicating that these
are one-electron processes. The difference between the
oxidative waves of 18a (∆E1/2 ) 0.55 V) is within the range
observed for Pd(TPP) (∆E1/2 ) 0.42 V) and Pd(OEP) (∆E1/2
red
) 0.72 V). The HOMO-LUMO gap for 18a (E1/2ox - E1/2
) 1.61 V) is much smaller than that for Pd(TPP) and Pd-
red
(OEP) (E1/2ox - E1/2 ∼ 2.4 V). However, it is comparable
to the gap for 13a. In the case of the previously reported
palladium porphyrin complexes, all waves have been un-
ambiguously assigned to processes associated with the
porphyrin ring itself. On the basis of the similarities between
the cyclic voltammograms of 13a, 18a, and 17a (i.e., the
potentials for the oxidative and reductive processes as well
as the HOMO-LUMO gap are comparable), and on the basis
of the fact that oxidation to palladium(III) is unlikely, we
propose that the couples observed in the cyclic voltammo-
gram of 18a are also ligand-centered redox processes.
The cyclic voltammogram of the analogous nickel(II)
complex (17a) is similar to the palladium(II) complex 18a
in that it also shows one irreversible reductive wave at Ep,c
) -1.21 V, one irreversible oxidative wave at Ep,a ) -0.19
V, and two reversible oxidative waves at E1/2 ) +0.41 and
+0.86 V when it is scanned within the limits of -1.9 and
+1.1 V (Figure 6b). As with the palladium(II) complex, the
irreversible oxidative wave at Ep,a ) -0.19 V is assigned to
a decomposition product generated during the irreversible
reduction. However, when the positive switching potential
was increased to +1.7 V, two additional irreversible oxidative
waves at Ep,a ) 1.45 and 1.60 V are also observed (accessing
these waves makes the waves at E1/2 ) 0.41 and 0.86 V
(34) (a) Kadish, K. M.; Sazou, D.; Maiya, G. B.; Han, B. C.; Liu, Y. M.;
Saoiabi, A.; Ferhat, M.; Guilard, R. Inorg. Chem. 1989, 28, 2542. (b)
Connick, P. A.; Macor, K. A. Inorg. Chem. 1991, 30, 4654.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7333

Lash et al.
Table 1. Summary of the Crystal Structure Data Collection and
Refinement for 14b and 18b
14b
18b
chemical formula
Mr, g/mol
crystal system
space group
unit cell params
a, Å
C44H35N3Ni
664.5
monoclinic
P21/n
C50H27Cl4N3Pd‚7/6(CHCl3)
1049.25
triclinic
P1h
31.028(2)
8.8409(6)
11.7434(8)
12.4999(8)
13.4732(9)
14.949(1)
71.939(1)
89.423(1)
68.782(1)
2216.4(3)
2
1.581
0.912
193(2)
12937
b, Å
c, Å
R, deg
â, deg
96.166(2)
γ, deg
V, Å3
3202.8(4)
4
1.378
Z
D
calcd, Mg m-3
Figure 8. ORTEP III drawing (50% probability level) of 18b, depicting
the planar conformation with hydrogen atoms drawn arbitrarily small.
Selected bond lengths (Å): C(21)-Pd 1.980(3), N(22)-Pd 2.021(2),
N(23)-Pd 2.075(2), N(24)-Pd 2.016(2), C(1)-C(21) 1.427(4), C(4)-C(21)
1.436(4). Selected bond angles (deg): C(21)-C(1)-C(2) 108.9(2), C(1)-
C(2)-C(3) 106.8(2), C(2)-C(3)-C(4) 107.4(2), C(3)-C(4)-C(21) 108.7-
(2), C(4)-C(21)-C(1) 107.2(2), C(6)-N(22)-C(9) 106.3(2), C(11)-
N(23)-C(14) 106.6(2), C(16)-N(24)-C(19) 106.2(2), C(21)-Pd-N(22)
90.7(1), N(22)-Pd-N(23) 89.48(9), N(23)-Pd-N(24) 89.55(9), N(24)-
Pd-C(21) 90.4(1), C(21)-Pd-N(23) 178.5(1), N(22)-Pd-N(24) 177.17-
(9).
µ, mm-1
0.644
T, K
193(2)
14860
6534
4718 (I > 2σI)
1.8-26.4
0.052
reflns collected
indep reflns
reflns obsd
θ range, deg
R[F2 > 2σ(F2)]
wR(F2) observed
S
8946
7795 (I > 2σI)
1.72-26.39
0.0395
0.0994
1.032
0.116
1.009
params (restraints)
433 (0)
575 (6)
1.897(3) Å is consistent with the smaller covalent bonding
radius of carbon compared to nitrogen. The trans-Ni(1)-
N(23) bond length of 1.964(2) Å is slightly distended. We
have suggested that this 0.03 Å increase in bond length may
be the result of a small trans-effect caused by the more Lewis
basic alkenyl, C(21).21 Similar 0.05 and 0.04 Å increases in
bond length are respectively observed in 18b and a closely
related silver(III) benzocarbaporphyrin.15a The trans-Ni-N
bond length is 0.021(2) Å longer than the cis-Ni-N in a
related nickel(II) N-confused isoquinoporphyrin;36 however,
all of the Ni-N bond lengths are similar in the case of 2-(2′-
bromoethyl)-5,10,15,20-tetraphenyl-2-aza-21-carbaporphy-
rinato-nickel(II),37 and 5,10,15,20-tetraphenyl-2-aza-21-
carbaporphyrinatosilver(III) shows only a 0.01 Å increase
in the trans-Ag-N bond length.4 Although the structural
characterizations of two other four-coordinate square planar
metal complexes of N-confused porphyrins have been
published, these display disorder involving the metal-
nitrogen bonds ,and this precludes comparison with our
data.3b,8a While the small trans-effect observed in 14b and
18b may indeed be real, the observed metal to ligand bond
lengths, as well as the degree of nonplanarity and mode of
distortion, are very much influenced by the metric parameters
of the ligand framework. Conclusive evidence relating
electronic effects to core metric parameters awaits the growth
of a database of structurally characterized carbaporphyrins.
Figure 7. ORTEP III drawing (50% probability level) of 14b, depicting
the presence of a ruffled conformation; hydrogen atoms and core substituents
have been omitted for clarity. Selected bond lengths (Å): C(21)-Ni 1.896-
(3), N(22)-Ni 1.934(2), N(23)-Ni 1.964(2), N(24)-Ni 1.928(2), C(1)-
C(21) 1.417(4), C(4)-C(21) 1.426(4). Selected bond angles (deg): C(21)-
C(1)-C(2) 110.6(3), C(1)C(2)-C(3) 106.5(3), C(2)-C(3)-C(4) 106.8(3),
C(3)-C(4)-C(21) 110.6(3), C(4)-C(21)-C(1) 105.3(2), C(6)-N(22)-
C(9) 104.7(2), C(11)-N(23)-C(14) 105.3(2), C(16)-N(24)-C(19) 104.6-
(2), C(21)-Ni-N(22) 90.4(1), N(22)-Ni-N(23) 90.1(1), N(23)-Ni-N(24)
89.9(1), N(24)-Ni-C(21) 89.9(1), C(21)-Ni-N(23) 177.2(1), N(22)-Ni-
N(24) 176.2(1).
(22)N(23)N(24) classify the porphyrin skeleton as ruffled.
Particularly illustrative are the C(5), C(10), C(15), and C(20)
bridges which alternate being above and below the plane
and exhibit four of the five largest deviations from the plane
at -0.424(3), 0.503(3), -0.474(3), and 0.502(3) Å, respec-
tively. In the context of this discussion, cis and trans
notations are relative to the carbon atom bonded to the metal.
The metal is centered between the donor ligands with
equivalent cis-Ni-N bond lengths of 1.934(3) and 1.928(3)
Å. These values fall within the typical 1.924 ( 0.025 Å range
reported for ruffled nickel(II) coordinated porphyrin-type
macrocycles.35 The shorter Ni(1)-C(21) bond length of
When turning to the structure of palladium(II) azulipor-
phyrin 18b (Figure 8), it is immediately apparent that the
macrocyclic core is significantly more planar than is the case
for the nickel(II) complex 14b. This is evidenced by the
pyrrole to mean [18]annulene plane dihedral angles of 9.7-
(2)°, 4.7(2)°, and 7.4(2)°. However, the azulene to mean [18]-
(35) Bruno, I. J.; Cole, J. C.; Edgington, P. R,; Kessler, M.; Macrae, C. F.;
McCabe, P.; Pearson, J.; Taylor, R. Acta Crystallogr. 2002, B58, 389.
A search of the Cambridge Structural Data base query returned 198
hits for tetrapyrrole nickel complexes with CR bridges at the R carbons.
These hits were broadly sorted into ruffled (169) and planar (29)
populations; comparison was made to the 211 Ni-N (nickel to pyrrole)
distances averaged from the ruffled population. A CSD search returned
11 hits for tetrapyrrole palladium complexes with CR bridges at the
R carbons; from these hits 60 Pd-Ni (palladium to pyrrole) distances
were averaged.
(36) Xiao, Z.; Patrick, B. O.; Dolphin, D. Chem. Commun. 2002, 1816.
(37) Schmidt, I.; Chmielewski, P. J.; Ciunik, Z. J. Org. Chem. 2002, 67,
8917.
7334 Inorganic Chemistry, Vol. 42, No. 22, 2003

Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
obtained at 18-21 °C unless otherwise stated. UV-vis spectra were
recorded on a Varian Cary UV spectrophotometer. EI mass spectral
determinations were made at the Mass Spectral Laboratory, School
of Chemical Sciences, University of Illinois at Urbana-Champaign,
supported in part by a grant from the National Institute of General
Medical Sciences (GM 27029). Elemental analyses were obtained
from the School of Chemical Sciences Microanalysis Laboratory
at the University of Illinois.
annulene plane dihedral angle of 15.8(1)° is deceptively large
due to the significant 11.6(2)° twist between the azulene’s
tropylium and cyclopentadienyl rings. The 8.1(2)° cyclo-
pentadienyl to mean [18]annulene plane dihedral angle is
more representative of the macrocycle conformation. The
palladium(II) ion is situated at the center of the macrocyclic
cavity and lies slightly, 0.0148(3) Å, above the C(21), N(22),
N(23), N(24) plane. The distances (0.293 Å rms) at which
skeletal atoms lie from the plane defined by Pd(1)C(21)N-
(22)N(23)N(24) classify the porphyrin skeleton as slightly
saddled. Particularly illustrative are the â-pyrrolic carbon
atom deviations from the plane. These pairs of atoms, C(7)/
C(8), C(12)/C(13), and C(17)/C(18), along with the azulene
C(3)/C(2) atoms alternate, as pairs, above and below the
plane. These atoms also exhibit the seven largest deviations
from the plane at -0.458(3), -0.408(3), 0.231(4), 0.239-
(4), -0.224(3), -0.320(3), and 0.312(3) Å, respectively. The
metal is centered between the donor ligands with equivalent
cis-Pd-N bond lengths of 2.021(2) and 2.016(2) Å. These
values fall within the typical 2.012 ( 0.018 Å range reported
for palladium-coordinated porphyrin-type macrocycles.35 The
shorter Pd(1)-C(21) bond length of 1.980(3) Å is consistent
with the smaller covalent radius of carbon compared to
nitrogen. The trans-Pd(1)-N(23) bond length is 2.075(2) Å,
which, as discussed earlier, represents a 0.05 Å increase in
bond length relative to the trans-Pd-N parameters. The more
planar nature of complex 18b compared to 14b illustrates
the better size match between the azuliporphyrin cavity and
the larger palladium(II) ion relative to the nickel(II) ion. The
ions have crystal radii equal to 0.78 and 0.63 Å for the
respective square planar coordinated divalent metal ions.38
Metal Complexes of meso-Unsubstituted Azuliporphyrins. [8,-
12,13,17-Tetraethyl-7,18-dimethylazuliporphyrinato]nickel(II)
(14a). A mixture of azuliporphyrin 8a (50 mg) and nickel(II) acetate
tetrahydrate (50 mg) in DMF (50 mL) was heated for 10 min at
80-90 °C. The mixture was diluted with chloroform and washed
with water. The organic solvent was removed in vacuo, and the
residue was chromatographed on silica gel eluting with chloroform.
Recrystallization from chloroform-hexanes gave the nickel(II)
complex 14a (36 mg, 64%) as brown crystals, mp >300 °C. UV-
vis (CHCl3): λmax (log ꢀ) 385 (4.74), 454 (4.54), 546 nm (4.36).
1H NMR (CDCl3; 40 °C): δ 1.59 (6H, t, J ) 7.6 Hz), 1.64 (6H, t,
J ) 7.6 Hz), 3.07 (6H, s), 3.42-3.48 (4H, two overlapping quartets),
7.42-7.53 (3H, m), 8.49 (2H, s), 8.93 (2H, d, J ) 10 Hz), 9.11
1
(2H, s). H NMR (d5-pyridine): δ 1.56 (6H, t, J ) 7.2 Hz), 1.61
(6H, t, J ) 7.6 Hz), 3.07 (6H, s), 3.46 (8H, q, J ) 7.6 Hz), 7.47-
7.52 (3H, m), 8.89 (2H, s), 9.31 (2H, d, J ) 9.6 Hz), 9.64 (2H, s).
HRMS (EI): m/z calcd for C36H35N3Ni 567.2184, found 567.2182.
[8,17-Diethyl-7,18-dimethyl-12,13-diphenylazuliporphyrinato]-
nickel(II) (14b). A mixture of diphenylazuliporphyrin 8b (20 mg)
and nickel(II) acetate tetrahydrate (25 mg) in DMF (30 mL) was
heated for 10 min at 80-90 °C. The mixture was diluted with
chloroform and washed with water. The organic solvent was
removed in vacuo, and the residue was chromatographed on silica
gel eluting with chloroform. Recrystallization from chloroform-
hexanes gave the nickel(II) complex 14b (16 mg, 73%) as iridescent
black crystals, mp >300 °C. UV-vis (CHCl3): λmax (log ꢀ) 368
1
Conclusions
(4.82), 466 (4.99), 646 nm (4.40). H NMR (CDCl3; 40 °C): δ
1.50 (6H, t, J ) 7.4 Hz), 3.06 (6H, s), 3.33 (4H, q, J ) 7.4 Hz),
7.36-7.52 (5H, m), 7.54-7.59 (4H, m), 7.75 (4H, d, J ) 6.8 Hz),
8.54 (2H, br s), 8.82 (2H, br d), 9.01 (2H, br s). H NMR (d5-
Azuliporphyrins have been shown to readily form orga-
nometallic derivatives under mild conditions. Stable com-
plexes have been generated where a central nickel-
(II), palladium(II), or platinum(II) ion resides within the
macrocyclic cavity and binds to all four atoms in the CNNN
core. The diamagnetic complexes are easily character-
ized by spectroscopic and mass spectrometric methods, and
two organometallic derivatives were further characterized
by X-ray crystallography. These results, together with the
easy availability of tetraarylazuliporphyrins via a one-pot
Rothemund-type reaction, suggest that azuliporphyrins have
the potential to be valuable ligands for the production of
unusual coordination complexes and organometallic deriva-
tives.
1
pyridine): δ 1.48 (6H, t, J ) 7 Hz), 3.09 (6H, s), 3.31 (4H, q, J )
7 Hz), 7.48-7.54 (5H, m), 7.60-7.64 (4H, m), 7.97 (4H, d, J )
7.6 Hz), 9.08 (2H, s), 9.36 (2H, d, J ) 8.8 Hz), 9.72 (2H, s). 13C
NMR (d5-pyridine): δ 11.4, 17.0, 19.9, 99.9, 108.5, 128.3, 129.4,
130.1, 132.2, 132.6, 137.0, 138.8, 139.4, 142.6, 143.7, 146.5, 147.8,
151.8, 154.3, 156.0. HRMS (EI): m/z calcd for C44H35N3Ni
663.2184, found 663.2182. Anal. Calcd for C44H35N3Ni: C, 79.53;
H, 5.31; N, 6.32. Found: C, 79.09; H, 5.17; N, 6.41.
[8,12,13,17-Tetraethyl-7,18-dimethylazuliporphyrinato]pal-
ladium(II) (15a). A mixture of azuliporphyrin 8a (26 mg) and
palladium(II) acetate (12 mg) in DMF (50 mL) was heated for 10
min at 80-90 °C. The mixture was diluted with chloroform and
washed with water. The organic solvent was removed in vacuo,
and the residue was chromatographed on silica gel eluting with
chloroform. Recrystallization from chloroform-hexanes gave the
title palladium(II) complex (28 mg, 93%) as black crystals, mp >
300 °C. UV-vis (CHCl3): λmax (log ꢀ) 368 (5.02), 412 (4.98), 447
Experimental Section
Azuliporphyrins 8a, 8b, 13a, and 13b were prepared as described
previously.23,28,29 NMR spectra were obtained on a Varian Gemini
400 MHz NMR spectrometer and reported in ppm relative to CDCl3
(residual chloroform at 7.26 ppm in proton NMR and CDCl3 triplet
at 77.23 ppm in carbon-13 NMR spectra) or d5-pyridine (residual
downfield resonance at 8.71 ppm in proton NMR and the downfield
triplet at 149.2 ppm in carbon-13 NMR spectra). These spectra were
1
(4.90), 574 nm (4.28). H NMR (CDCl3; 40 °C): δ 1.65 (6H, t, J
) 7.6 Hz), 1.68 (6H, t, J ) 7.6 Hz), 3.16 (6H, s), 3.46-3.58 (8H,
2 overlapping quartets), 7.44-7.54 (3H, m), 8.57 (2H, br s), 9.03
1
(2H, br d), 9.18 (2H, br s). H NMR (d5-pyridine): δ 1.62 (6H, t,
J ) 7.4 Hz), 1.65 (6H, t, J ) 7.4 Hz), 3.16 (6H, s), 3.48-3.56
(8H, 2 overlapping quartets), 7.54-7.58 (3H, m), 9.02 (2H, s), 9.43
(2H, m), 9.78 (2H, s). HRMS (EI): m/z calcd for C36H35N3Pd
(38) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7335

Lash et al.
615.1866, found 615.1863. Anal. Calcd for C36H35N3Pd‚2/5CHCl3:
C, 65.85; H, 5.37; N, 6.33. Found: C, 65.53; H, 5.34; N, 6.22.
[8,17-Diethyl-7,18-dimethyl-12,13-diphenylazuliporphyrinato]-
palladium(II) (15b). A mixture of diphenylazuliporphyrin 8b (25
mg) and palladium(II) acetate (15 mg) in DMF (30 mL) was heated
for 10 min at 80-90 °C. The mixture was diluted with chloroform
and washed with water. The organic solvent was removed in Vacuo,
and the residue was chromatographed on silica gel eluting with
chloroform. Recrystallization from chloroform-hexanes gave the
palladium(II) diphenylazuliporphyrin 15b (21 mg, 72%) as black
crystals, mp >300 °C. UV-vis (5% Et3N-CHCl3): λmax (log ꢀ)
nickel(II) acetate tetrahydrate (10 mg) in DMF (10 mL) under reflux
for 20 min and the solution cooled to room temperature. The
mixture was diluted with chloroform, washed with water, and dried
over sodium sulfate. The solvent was evaporated on a rotary
evaporator; residual DMF was removed using an oil pump. The
residue was chromatographed on a grade III alumina column, eluting
with 20% hexanes-dichloromethane. The product was obtained
as a green fraction. Recrystallization from chloroform-hexanes
gave the nickel(II) complex (8.8 mg; 81%) as lustrous green
crystals, mp >300 °C. UV-vis (CHCl3): λmax (log ꢀ) 400 (4.84),
1
468 (4.65), 488 (4.67), 594 (4.15), 649 (4.18), 794 nm (3.54). H
1
NMR (CDCl3): δ 6.75 (2H, t, J ) 10 Hz), 7.08 (1H, t, J ) 9.4
Hz), 7.37 (2H, d, J ) 10 Hz), 7.56-7.65 (12H, m), 7.82-7.90
(10H, m), 8.00 (2H, s), 8.06 (2H, d, J ) 4.8 Hz). 13C NMR
(CDCl3): δ 117.8, 127.2, 127.3, 127.5, 127.9, 129.0, 129.6, 130.0,
132.5, 133.0, 133.5, 133.6, 135.2, 137.7, 141.2, 141.8, 146.5, 148.2,
151.8, 156.5, 166.0. HRMS (FAB): m/z calcd for C50H31N3Ni +
H 732.1950, found 732.1950. Anal. Calcd for C50H31N3Ni‚
1/2CHCl3: C, 76.57; H, 4.01; N, 5.30. Found: C, 76.64; H, 3.85;
N, 5.39.
380 (4.82), 415 (4.78), 450 (4.69), 580 (4.15), 638 nm (3.92). H
NMR (CDCl3; 50 °C): δ 1.59 (6H, t, J ) 7.6 Hz), 3.14 (6H, s),
3.42 (4H, q, J ) 7.6 Hz), 7.33-7.41 (3H, m), 7.51 (2H, t, J ) 7.4
Hz), 7.58 (4H, t, J ) 7.6 Hz), 7.83 (4H, d, J ) 7.2 Hz), 8.75 (2H,
1
br s), 8.81 (2H, d, J ) 9.2 Hz), 9.10 (2H, br s). H NMR (d5-
pyridine): δ 1.55 (6H, t, J ) 7.4 Hz), 3.16 (6H, s), 3.40 (4H, q, J
) 7.4 Hz), 7.52 (2H, t, J ) 7.6 Hz), 7.57-7.60 (3H, m), 7.63 (4H,
t, J ) 7.6 Hz), 8.01 (4H, d, J ) 7.2 Hz), 9.23 (2H, s), 9.42 (2H,
m), 9.82 (2H, s). 13C NMR (d5-pyridine): δ 11.4, 17.1, 20.0, 100.7,
110.7, 123.4, 126.8, 128.4, 129.4, 132.7, 133.0, 137.7, 137.9, 141.8,
143.3, 149.3, 156.0. HRMS (EI): m/z calcd for C44H35N3Pd
711.1866, found 711.1882. Anal. Calcd for C44H35N3Pd‚1/10-
CHCl3: C, 73.15; H, 4.88; N, 5.80. Found: C, 73.28; H, 4.70; N,
5.72.
[5,10,15,20-Tetrakis(4-chlorophenyl)azuliporphyrinato]nickel-
(II) (17b). Tetrakis(4-chlorophenyl)azuliporphyrin 13b (10.0 mg)
was reacted with nickel(II) acetate tetrahydrate (10 mg) in DMF
(20 mL) under the foregoing conditions. Recrystallization from
chloroform-hexanes gave the organometallic complex (7.0 mg;
65%) as lustrous green crystals, mp 252-256 °C, dec. UV-vis
(CHCl3): λmax (log ꢀ) 400 (4.88), 473 (4.69), 490 (4.70), 591 (4.19),
[8,12,13,17-Tetraethyl-7,18-dimethylazuliporphyrinato]-
platinum(II) (16a). A mixture of azuliporphyrin 8a (26.0 mg) and
platinum(II) chloride (16 mg) in DMF (25 mL) was heated under
reflux for 15 min. The mixture was diluted with chloroform and
washed with water. The organic solvent was removed in vacuo,
and the residue was chromatographed on silica gel eluting with
chloroform. Recrystallization from chloroform-hexanes gave the
title platinum(II) complex (9.5 mg, 27%) as black crystals, mp >300
°C. UV-vis (CHCl3): λmax (log ꢀ) 367 (4.97), 427 (4.55), 442
(4.62), 513 (4.34), 551 (4.31), 621 (4.04), 670 (infl, 3.97), 741 nm
1
647 (4.21), 796 nm (3.60). H NMR (CDCl3): δ 6.91 (2H, t, J )
10.2 Hz), 7.21 (1H, t, J ) 9.6 Hz), 7.43 (2H, d, J ) 10.4 Hz),
7.56-7.61 (8H, m), 7.76-7.81 (10H, m), 7.97 (2H, s), 8.02 (2H,
d, J ) 5.2 Hz). 13C NMR (CDCl3): δ 116.8, 127.6, 127.7, 129.7,
130.0, 132.5, 132.9, 134.0, 134.4, 134.5, 134.7, 135.2, 135.8, 138.1,
139.4, 140.0, 146.5, 148.3, 151.7, 156.5, 165.8. HRMS (FAB): m/z
calcd for C50H27Cl4N3Ni 867.0313, found 867.0314. Anal. Calcd
for C50H27Cl4N3Ni‚1/5CHCl3: C, 67.43; H, 3.06; N, 4.70. Found:
C, 67.60; H, 2.91; N, 4.76.
1
(infl, 3.56). H NMR (CDCl3-d5-pyridine): δ 1.66 (6H, t, J )
Hz), 1.70 (6H, t, J ) Hz), 3.19 (6H, s), 3.47-3.55 (8H, 2
overlapping quartets), 7.31 (2H, t, J ) 9.6 Hz), 7.63 (1H, t, J )
9.6 Hz), 8.86 (2H, singlet with platinum-195 satellites, 4JPt,H ) 4.4
Hz), 9.24 (2H, d, J ) 9.6 Hz), 9.37 (2H, singlet with platinum-195
satellites, 4JPt,H ) 5.3 Hz). HRMS (FAB): m/z calcd for C36H35N3-
Pt 704.2479, found 704.2482.
[5,10,15,20-Tetraphenylazuliporphyrinato]palladium(II) (18a).
Tetraphenylazuliporphyrin 13a (10.0 mg) was heated under reflux
with palladium(II) acetate (5 mg) in DMF (10 mL) for 10 min and
the solution cooled to room temperature. The mixture was diluted
with chloroform, washed with water, and dried over sodium sulfate.
The solvent was evaporated on a rotary evaporator; residual DMF
was removed using an oil pump. The residue was chromatographed
on a grade III alumina column, eluting with 20% hexanes-
dichloromethane. The product was obtained as a green fraction.
Recrystallization from chloroform-hexanes gave the palladium-
(II) complex (7.8 mg; 67%) as a lustrous black powder, mp > 300
°C. UV-vis (CHCl3): λmax (log ꢀ) 375 (4.69), 402 (4.83), 481
(4.75), 586 (4.28), 629 (4.26), 791 nm (3.68). 1H NMR (d5-
pyridine): δ 6.96 (2H, t, J ) 9.8 Hz), 7.25 (1H, t, J ) 10 Hz),
7.61-7.68 (12H, m), 7.71 (2H, d, J ) 10.4 Hz), 7.94-7.97 (4H,
m), 8.06-8.09 (4H, m), 8.23 (2H, d, J ) 5.2 Hz), 8.26 (2H, s),
8.38 (2H, d, J ) 4.8 Hz). 13C NMR (d5-pyridine): δ 119.8, 127.1,
127.3, 127.5, 127.8, 128.2, 129.5, 132.2, 132.5, 132.6, 133.6, 133.9,
136.6, 137.0, 139.3, 142.5, 143.2, 144.9, 147.7, 160.5. HRMS
(FAB): m/z calcd for C50H31N3Pd 779.1553, found 779.1554. Anal.
Calcd for C50H31N3Pd‚1/8CHCl3: C, 75.71; H, 3.94; N, 5.28.
Found: C, 75.38; H, 3.74; N, 5.12.
[8,17-Diethyl-7,18-dimethyl-12,13-diphenylazuliporphyrinato]-
platinum(II) (16b). A mixture of diphenylazuliporphyrin 8b (20.0
mg) and platinum(II) chloride (14 mg) in DMF (25 mL) was reacted
under the foregoing conditions. Recrystallization from chloroform-
hexanes gave the platinum(II) azuliporphyrin 16b (6.1 mg, 23%)
as black crystals, mp > 300 °C. UV-vis (5% Et3N-CHCl3): λmax
(log ꢀ) 372 (5.03), 420 (4.62), 442 (4.68), 521 (4.37), 560 (4.41),
629 (4.145), 670 (4.12), 750 nm (infl, 3.63). 1H NMR (d5-
pyridine): δ 1.63 (6H, t, J ) 7.4 Hz), 3.23 (6H, s), 3.42 (4H, q, J
) 7.4 Hz), 7.35 (2H, t, J ) 9.6 Hz), 7.57 (2H, t, J ) 7.4 Hz),
7.63-7.70 (5H, m), 7.98 (4H, d, J ) 7.2 Hz), 9.09 (2H, singlet
with platinum-195 satellites, 4JPt,H ) 4.4 Hz), 9.24 (2H, d, J ) 10
Hz), 9.43 (2H, singlet with platinum-195 satellites, 4JPt,H ) 5.6 Hz).
13C NMR (CDCl3-d5-pyridine): δ 9.1, 14.5, 17.8, 98.6, 110.3, 126.2,
127.1, 130.4, 136.1, 137.4, 138.2, 138.6, 139.6, 157.6. HRMS
(EI): m/z calcd for C44H35N3Pt 799.2458, found 799.2458. Anal.
Calcd for C44H35N3Pt‚1/3CHCl3: C, 58.63; H, 4.78; N, 5.64.
Found: C, 58.62; H, 4.87; N, 5.50.
[5,10,15,20-Tetrakis(4-chlorophenyl)azuliporphyrinato]-
palladium(II) (18b). Tetrakis(4-chlorophenyl)azuliporphyrin 13b
(10 mg) was reacted with palladium(II) acetate (10.0 mg) in DMF
(20 mL) under the foregoing conditions. Recrystallization from
chloroform-hexanes gave the organometallic derivative (11.0 mg;
Metal Complexes of meso-Tetraaryl Substituted Azulipor-
phyrins. [5,10,15,20-Tetraphenylazuliporphyrinato]nickel(II)
(17a). Tetraphenylazuliporphyrin 13a (10.0 mg) was heated with
7336 Inorganic Chemistry, Vol. 42, No. 22, 2003

Ni(II), Pd(II), and Pt(II) Complexes of Azuliporphyrins
97%) as a black powder, mp > 300 °C. UV-vis (CHCl3): λmax
(log ꢀ) 374 (4.76), 403 (4.90), 482 (4.82), 587 (4.35), 627 (4.33),
783 nm (3.76). 1H NMR (CDCl3): δ 6.84 (2H, t, J ) 10 Hz), 7.16
(1H, t, J ) 9.6 Hz), 7.45 (2H, d, J ) 10 Hz), 7.57-7.63 (8H, m),
7.75 (4H, AA′XX′ system), 7.86 (4H, AA′XX′ system), 7.92 (2H,
d, J ) 5.2 Hz), 7.97 (2H, s), 8.04 (2H, d, J ) 5.2 Hz). 13C NMR
(CDCl3): δ 126.5, 127.4, 127.5, 129.4, 130.2, 132.3 (2), 134.2,
134.5, 134.6, 134.9, 136.1, 136.4, 138.5, 140.6, 141.5, 144.7, 147.7,
149.5, 157.6. HRMS (FAB): m/z calcd for C50H27Cl4N3Pd 914.9994,
found 914.9998. Anal. Calcd for C50H27Cl4N3Pd‚CHCl3: C, 59.05;
H, 2.72; N, 4.05. Found: C, 59.38; H, 2.61; N, 4.14.
Empirical absorption correction was performed on the data from
14b through the use of the SADABS procedure.39c Face-indexed
absorption correction by integration was performed on the data from
the triclinic crystal of 18b using SHELXTL.39d Solution and data
analysis were performed using the WinGX software package.40 Both
structures were solved using the direct methods program SIR-92.41
The remaining atoms were located using difference Fourier
synthesis, and full-matrix least-squares refinement on F2 that led
to a convergence was performed using SHELXL-97.42 With the
exception of a solvent molecule in 18b, non-hydrogen atoms were
refined with anisotropic thermal parameters. Hydrogen atoms were
assigned positions based on the geometries of their attached carbon
atoms, and were given isotropic thermal parameters 20% greater
than their parent carbon atoms.
[5,10,15,20-Tetraphenylazuliporphyrinato]platinum(II) (19a).
Tetraphenylazuliporphyrin 13a (10.0 mg) was heated under reflux
with platinum(II) chloride (10 mg) in DMF (10 mL) for 10 min
and the solution cooled to room temperature. The mixture was
diluted with chloroform, washed with water, and dried over sodium
sulfate. The solvent was evaporated on a rotary evaporator; residual
DMF was removed using an oil pump. The residue was chromato-
graphed on a grade III alumina column, eluting with 20% hexanes-
dichloromethane, and the product was obtained as a green fraction.
Recrystallization from chloroform-hexanes gave the platinum(II)
complex (3.0 mg; 23%) as a dark green powder, mp >300 °C.
UV-vis (CHCl3): λmax (log ꢀ) 382 (4.96), 442 (4.71), 466 (4.73),
X-ray quality crystals of 14b were obtained by diffusion of
hexanes into dichloromethane. A dark green rod thereby obtained
of approximate dimensions 0.60 × 0.05 × 0.05 mm3 was mounted
on a glass fiber with super-glue and transferred to the diffractometer.
Limiting indices were as follows: -38 e h e 38, -11 e k e 10,
-13 e l e 14. The structure was refined to convergence, (∆/σ)max
) 0.006; a final difference Fourier synthesis showed features in
the range ∆Fmax ) 0.746 e Å-3 to ∆Fmin ) -0.502 e Å-3 and were
deemed of no chemical significance. This structure was previously
communicated,21 but the detailed analysis is provided in this Article.
X-ray quality crystals of 18b were obtained by slow evaporation
of chloroform. A pale brown plate thereby obtained of approximate
dimensions 0.50 × 0.24 × 0.06 mm3 was mounted on a glass fiber
with super-glue and transferred to the diffractometer. Limiting
indices were as follows: -15 e h e 15, -16 e k e 14, -18 e l
e 18. In addition to the parent molecule, 1.1667 CHCl3 molecules
were located in the asymmetric unit. The first solvent molecule
was readily observed in the initial SIR-92 solution and was refined
anisotropically. The remaining partial occupancy, disordered solvent
was located from difference Fourier synthesis and is poorly behaved.
The best model gave 1/3 of a chloroform solvent molecule located
with the carbon atom 0.58 Å from, and disordered about, a
crystallographic inversion center; thus, atoms of this CHCl3 were
treated as having 1/6 occupancy in the asymmetric unit. To establish
reasonable bonding parameters, this CHCl3 molecule was con-
strained such that all C-Cl distances were isometric, and all Cl-
Cl separations were isometric. Isotropic refinement gave 1.80(3)
Å C-Cl and 1.07(2)° Cl-C-Cl bond angles for the disordered
CHCl3 molecule. The structure was refined to convergence, (∆/
σ)max ) 0.001; a final difference Fourier synthesis showed features
in the range ∆Fmax ) 0.98 e Å-3 to ∆Fmin ) -0.616 e Å-3. These
peaks are in the vicinity of the full occupancy chloroform solvent.
The 10 largest residual electron density peaks all lie within 1 Å of
a chlorine or the palladium atom, and were deemed to be of minimal
structural and of no chemical significance.
1
570 (4.35), 616 (4.24), 774 nm (3.53). H NMR (CDCl3): δ 6.66
(2H, t, J ) 10 Hz), 7.26 (1H, t, overlaps with residual chloroform
signal), 7.56-7.65 (14H, m), 7.87-7.94 (10H, m), 7.97-8.02 (4H,
m). 13C NMR (d5-pyridine; 55 °C): δ 119.3, 124.3, 127.1, 127.3,
127.6, 127.9, 132.2, 133.0, 133.2, 133.3, 133.6, 133.7, 134.1, 135.3,
138.5, 142.1, 142.4, 143.0, 146.5, 149.3, 161.4. HRMS (FAB): m/z
calcd for C50H31N3Pt 868.2166, found 868.2166.
[5,10,15,20-Tetrakis(4-chlorophenyl)azuliporphyrinato]-
platinum(II) (19b). Tetrakis(4-chlorophenyl)azuliporphyrin 13b (10
mg) was reacted with platinum(II) chloride (10 mg) in DMF (20
mL) under the foregoing conditions. Recrystallization from chlo-
roform-hexanes gave the platinum(II) derivative 19b (2.75 mg;
22%) as a dark green powder, mp >300 °C. UV-vis (CHCl3):
λmax (log ꢀ) 383 (4.99), 444 (4.73), 466 (4.75), 567 (4.38), 619
(4.24), 654 (infl, 4.12), 771 nm (3.57). 1H NMR (CDCl3): δ 6.62
(2H, t, J ) 10 Hz), 7.24 (1H, t, J ) 10 Hz), 7.43 (2H, d, J ) 10.8
Hz), 7.56 (4H, AA′XX′ system), 7.61 (4H, AA′XX′ system), 7.71
(4H, AA′XX′ system), 7.84 (4H, AA′XX′ system), 7.91 (2H,
doublet, J ) 5.2 Hz), 8.04 (2H, d, J ) 5.6 Hz, with Pt-195
satellites), 7.99 (2H, singlet with Pt-195 satellites, 4JPt,H ) 5.6 Hz).
HRMS (FAB): m/z calcd for C50H27Cl4N3Pt 1004.0607, found
1004.0608.
Cyclic Voltammetry. The electrochemical studies were carried
out in anhydrous dichloromethane using a BAS CV-27 potentiostat
equipped with an x-y recorder. A conventional three-electrode cell
consisting of a platinum disk working electrode, a platinum wire
auxiliary electrode, and a Ag/AgNO3 (0.01 M) reference electrode
was used. The cyclic voltammograms were run in a 0.2 M Bu4-
NBF4 solution in an inert atmosphere glovebox at a scan rate of
200 mV/s. The scanning limits were +1.7 V to -1.9 V vs Ag/
AgNO3, and the ferrocene/ferrocenium couple appeared at +0.22
V vs the Ag/AgNO3 reference. All potentials are reported vs the
Ag/AgNO3 reference electrode.
Complete X-ray structural data has been deposited at the
Cambridge Crystallographic Data Center, CCDC No. 179074 and
(39) (a) Bruker SMART 1000 CCD software package; Bruker Advanced
X-ray Solutions: Madison, WI, 1999. (b) Bruker SAINT Integration
Software for Single-Crystal Data framessh, k, l, intensity; Bruker
Advanced X-ray Solutions: Madison, WI, 1999. (c) Bruker SADABSs
Empirical adsorption correction procedures; Bruker Advanced X-ray
Solutions: Madison, WI, 1999. (d) SHELXTLsProgram for crystal
structure analysis; Bruker Advanced X-ray Solutions: Madison, WI,
1997.
(40) (a) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837. (b) Farrugia,
L. J. J. Appl. Crystallogr. 1997, 30, 565.
(41) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343.
Crystal Structure Determination of 14b and 18b. Crystal data
and a summary of the intensity data and collection parameters for
14b and 18b are given in Table 1. X-ray data for the two
compounds were collected using a Bruker P4/R4/SMART 1000
CCD diffractometer equipped for Mo KR radiation (λ ) 0.71073
Å), at -80 °C. Data collection and cell refinement were performed
using SMART.39a Data reduction was accomplished using SAINT.39b
(42) Sheldrick, G. M. SHELXS-97; 97-2 ed.; Programs for X-ray Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7337

Lash et al.
No. 211045. Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, U.K. (Fax, + 44-1223-336033; e-mail, deposit@ccdc.cam.ac.uk;
URL, http://www.ccdc.cam.ac.uk).
and Pfizer Inc. We also thank Dr. Robert McDonald and
The University of Alberta Structure Determination Labora-
tory for the collection of low-temperature CCD X-ray data.
1
Supporting Information Available: UV-vis, H NMR, 13C
Acknowledgment. This material is based upon work
supported by the National Science Foundation under Grants
CHE-9732054 and CHE-0134472 (to T.D.L.) and the donors
of the Petroleum Research Fund, administered by the
American Chemical Society (to T.D.L. and G.M.F.). D.A.C.
received additional funding from the Barry M. Goldwater
Foundation, the Johnson and Johnson Travel Award Program,
NMR and mass spectra for selected compounds. Tables of crystal-
lographic details, atomic coordinates, bond lengths and angles,
critical angle planes, torsional angles, anisotropic thermal param-
eters, and hydrogen atom parameters for azuliporphyrin derivatives
14b and 18b. Crystallographic data in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
IC030166B
7338 Inorganic Chemistry, Vol. 42, No. 22, 2003