Cadmium(II) and zinc(II) complexes of pyrrole-appended oxacarbaporphyrin: A side-on coordination mode of O-confused carbaporphyrin

Article abstract of DOI:10.1021/ic051238x

A pyrrole adduct of 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin [(H,pyr)OCPH]H₂ reacted with sodium ethanolate to yield 5,20-diphenyl-10,15-di(p-tolyl)-3-ethoxy-3-(2′-pyrrol)-2-oxa-21- carbaporphyrin [(EtO,Pyr)OCPH]H₂. Subsequently, true O-confused oxaporphyrin with a pendant pyrrole ring [(pyr)OCPH]H was formed by the addition of acid to [(EtO,pyr)OCPH]H₂, which triggered an ethanol elimination. In the course of this process, the tetrahedral-trigonal rearrangements originated at the C(3) atom. Insertion of zinc(II), cadmium(II), and nickel(II) into [(pyr)-OCPH]H yielded [(pyr)OCPH]Zn^IICl, [(pyr)OCPH]Cd^IICl, and [(pyr)OCP]Ni^II. The formation of [(pyr)OCP]Ni^II was accompanied by the C(21)H dehydrogenation step. The nickel(II) ion of [(pyr)OCP]Ni^II, coordinated to a dianionic macrocyclic ligand, is bound by three pyrrolic nitrogens and a trigonally hybridized C(21) atom of the inverted furan. The pyrrole-appended O-confused carbaporphyrin acts as a monoanionic ligand toward zinc(II) and cadmium-(II) cations. Three nitrogen atoms and the C(21)H fragment of the inverted furan occupy equatorial positions. In ¹H NMR spectra, the unique inner C(21)H resonances of the inverted furan ring are located at 0.15 ppm for [(pyr)-OCPH]Zn^IICl, and at 0.21 ppm for [(pyr)OCPH]Cd^IICl. The proximity of the furan fragment to the metal ion induces direct scalar couplings between the spin-active nucleus of the metal (^111/113Cd) and the adjacent ¹H nucleus. The interaction of the metal ion and C(21)H was also reflected by significant changes in carbon chemical shifts ([(pyr)-OCPH]Zn^IICl, 78.3 ppm; [(pyr)OCPH]Cd^IICl, 81.4 ppm; the free base, 101.3 ppm). The density functional theory (DFT) has been applied to model the molecular structures of zinc(II) and cadmium(II) complexes of O-confused oxaporphyrin with an appended pyrrole ring. The Cd...C(21) distance in the optimized structure exceeds the typical Cd-C bond lengths, but is much shorter than the corresponding van der Waals contact.

Full text of DOI:10.1021/ic051238x

Inorg. Chem. 2005, 44, 9779−9786
Cadmium(II) and Zinc(II) Complexes of Pyrrole-Appended
Oxacarbaporphyrin: A Side-on Coordination Mode of O-Confused
Carbaporphyrin
Miłosz Pawlicki, Lechosław Latos-Graz3yn´ski,* and Ludmiła Szterenberg
Department of Chemistry, UniVersity of Wrocław, 14 F. Joliot-Curie Street,
Wrocław 50 383, Poland
Received July 25, 2005
A pyrrole adduct of 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin [(H,pyr)OCPH]H2 reacted with sodium
ethanolate to yield 5,20-diphenyl-10,15-di(p-tolyl)-3-ethoxy-3-(2 -pyrrol)-2-oxa-21-carbaporphyrin [(EtO,pyr)OCPH]H2.
Subsequently, “true” O-confused oxaporphyrin with a pendant pyrrole ring [(pyr)OCPH]H was formed by the addition
of acid to [(EtO,pyr)OCPH]H2, which triggered an ethanol elimination. In the course of this process, the tetrahedral
′
−
trigonal rearrangements originated at the C(3) atom. Insertion of zinc(II), cadmium(II), and nickel(II) into [(pyr)-
OCPH]H yielded [(pyr)OCPH]ZnIICl, [(pyr)OCPH]CdIICl, and [(pyr)OCP]NiII. The formation of [(pyr)OCP]NiII was
accompanied by the C(21)H dehydrogenation step. The nickel(II) ion of [(pyr)OCP]NiII, coordinated to a dianionic
macrocyclic ligand, is bound by three pyrrolic nitrogens and a trigonally hybridized C(21) atom of the inverted
furan. The pyrrole-appended O-confused carbaporphyrin acts as a monoanionic ligand toward zinc(II) and cadmium-
1
(II) cations. Three nitrogen atoms and the C(21)H fragment of the inverted furan occupy equatorial positions. In H
NMR spectra, the unique inner C(21)H resonances of the inverted furan ring are located at 0.15 ppm for [(pyr)-
OCPH]ZnIICl, and at 0.21 ppm for [(pyr)OCPH]CdIICl. The proximity of the furan fragment to the metal ion induces
/
direct scalar couplings between the spin-active nucleus of the metal (111 113Cd) and the adjacent 1H nucleus. The
interaction of the metal ion and C(21)H was also reflected by significant changes in carbon chemical shifts ([(pyr)-
OCPH]ZnIICl, 78.3 ppm; [(pyr)OCPH]CdIICl, 81.4 ppm; the free base, 101.3 ppm). The density functional theory
(DFT) has been applied to model the molecular structures of zinc(II) and cadmium(II) complexes of O-confused
oxaporphyrin with an appended pyrrole ring. The Cd‚‚‚C(21) distance in the optimized structure exceeds the typical
Cd−C bond lengths, but is much shorter than the corresponding van der Waals contact.
Introduction
class of macrocyclic ligands, called carbaporphyrinoids. In
general, carbaporphyrinoids are porphyrin analogues that
possess at least one CH unit in place of a pyrrolic nitrogen
in the coordination core, and which are potentially suited
for accommodating a large variety of metal ions. For
instance, the coordination properties of 6,11,16,21-tetra-
arylbenziporphyrin,7-9 8,19-dimethyl-9,13,14,18-tetraethyl-
oxybenziporphyrin,10 azuliporphyrins,11 and benzocarba-
porphyrin12 have been investigated. 5,10,15,20-Tetraphenyl-
p-benziporphyrin is a carbaporphyrinoid with a p-phenylene
Inverted porphyrin 1 (N-confused porphyrin, 5,10,15,20-
tetraaryl-2-aza-21-carbaporphyrin)1,2 and its derivatives have
revealed a remarkable tendency to stabilize peculiar orga-
nometallic compounds.3-6 At present, one can notice that
organometallic chemistry in the macrocyclic environment
extends beyond the inverted porphyrin, and includes a whole
* To whom correspondence should be addressed. E-mail:
LLG@wchuwr.chem.uni.wroc.pl.
(1) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Rachlewicz, K.; Głowiak,
T. Angew. Chem., Int. Ed. 1994, 33, 779.
(2) Furuta, H.; Asano, T.; Ogawa, T. J. Am. Chem. Soc. 1994, 116, 767.
(3) Latos-Graz˘yn´ski, L. Core Modified Heteroanalogues of Porphyrins
and Metalloporphyrins. In The Porphyrin Handbook; Kadish, K. M.,
Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000;
pp 361-416.
(4) Furuta, H.; Maeda, H.; Osuka, A. Chem. Commun. 2002, 1795.
(5) Srinivasan, A.; Furuta, H. Acc. Chem. Res. 2005, 38, 10.
(6) Harvey, J. D.; Ziegler, C. J. Coord. Chem. ReV. 2003, 247, 1.
(7) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Chem.sEur. J. 2001, 7, 5113.
(8) Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Szterenberg, L.; Panek, J.; Latajka,
Z. J. Am. Chem. Soc. 2004, 126, 4566.
(9) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Acc. Chem. Res. 2005, 38, 88.
(10) Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Lash, T. D.; Szterenberg, L. Inorg.
Chem. 2001, 40, 6892.
(11) Graham, S. R.; Ferrence, G. M.; Lash, T. D. Chem. Commun. 2002,
894.
10.1021/ic051238x CCC: $30.25
Published on Web 11/23/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 26, 2005 9779

Pawlicki et al.
Scheme 1. Heteroatom-Confusion Concept
palladium(II) (7-Pd) , and silver(III) (4-Ag, 6-Ag, or 7-Ag)
complexes (Scheme 3).
These carbaporphyrinoids reveal the peculiar flexibility
of their molecular and electronic structures, which readily
adjust the anionic character of a coordination core to an
oxidation state of the metal ion. Modifications are readily
triggered by the addition and/or elimination of a nucleophile
at the perimeter furan carbon. Tetrahedral-trigonal rear-
rangements originate at the C(3) atom, and control a crucial
pyrrole contribution to the macrocyclic conjugation.15
The further exploration of 4, 5, 6, and 7 as flexible
macrocyclic organometallic ligands implies their isolation
in free base forms. Recently, we have described the synthesis
and spectroscopic characterization of 2-oxa-21-carbaporphy-
rin derivatives without appended pyrrole linked to C(3),
including the inherently reactive, true O-confused 2-oxa-21-
carbaporphyrin [(H)OCPH]H 3.16 At this stage of exploration,
we have readily realized that the coordinating properties of
true O-confused oxaporphyrin, which contains the sp2
hybridized C(3) carbon atom, can be investigated, provided
that the stable 3-substituted derivatives of 3 will be used. In
light of this objective, O-confused oxaporphyrin with ap-
pended pyrrole, i.e., 2-oxa-3-(2′-pyrrolyl)-5,10,15,20-tet-
raphenyl-21-carbaporphyrin 7, is of particular importance.
The formation of an inverted porphyrin with a pendant
pyrrole ring was also reported.18 Potentially, 7 may act as a
mono- or dianionic ligand after the dissociation of NH or
NH and C(21)H protons, respectively. The dianionic nature
of 7 has already been revealed in the coordination of nickel-
(II) (7-Ni) or silver(III) (7-Ag) (Scheme 3).15
Here, the coordination of zinc(II) and cadmium(II) has
been explored. For the very first time, O-confused oxapor-
phyrin has been found to act as a monoanionic ligand.
Consequently, an unprecedented side-on coordination mode
of O-confused carbaporphyrin has been detected, which
affords an interaction between the metal ion and the C(21)H
unit. Previously, we have determined that the adjacency of
the NMR-active metal ion and the CH unit results in
profound changes in NMR parameters.8,13,19,20 Here, the
detected couplings with the spin-active 111/113Cd have been
applied as a proof for the unique interaction with the CH
unit of the inverted furan. Such couplings are usually
classified as “through-space” or “nonbonding”, because their
magnitude cannot be rationalized in terms of the network of
formal bonds in the molecule.21,22
Scheme 2. Derivatives of O-Confused Porphyrins
ring embedded in the tripyrrolic framework that may be
considered to have two adjacent CH units in the macrocyclic
core. Significantly, p-benziporphyrin forms a complex with
cadmium(II) and nickel(II) to reveal an unprecedented η2
Cd(II)-arene and η2 Ni(II)-arene interaction.8,13
In the construction of a nontrivial macrocyclic environment
for organometallic chemistry, we can apply a heteroatom
confusion (X-confusion) concept, originally exemplified by
a porphyrin-2-aza-21-carbaporphyrin couple.1,2 Thus, in-
terchanging a â-methine group with a heteroatom of 21-
heteroporphyrin transforms the regular porphyrin into its
X-confused isomer (1, 2, and 3, respectively) classified as
carbaporphyrinoid by virtue of a (CNNN) coordination core.
These molecules, although porphyrin-like in character, are
expected to have fundamentally different electronic and
coordination properties.
In our initial studies, we have reported the synthesis of
S-confused thiaporphyrin 2.14 Following this direction, we
have obtained a group of carbaporphyrins or metallocarba-
porphyrins, constructed using the O-confusion strategy
(Scheme 2).15 The extremely reactive periphery of 3-oxa-21--
carbaporphyrin 3 facilitates a formation of addition products
(pyrrole, 4; ethanol, 5) in reasonable yields.15,16 To date, the
synthesis and characterization of the free base related to 3
has been achieved in a single case of 4, which can be
formally considered as an effect of 2-oxa-3-(2′-pyrrolyl)-
5,10,15,20-tetraphenyl-21-carbaporphyrin [(pyr)OCPH]H 7
hydrogenation.15,17 The macrocycles 6 and 7 have been solely
characterized as ligands at the respective nickel(II) (7-Ni),
(17) From now on, we will use the symbol (H)OCP to denote the
hypothetical dianion obtained from the O-confused oxaporphyrin 3
by abstraction of a pyrrolic NH proton and the C-bound proton H(21).
The groups attached to the C(3) atom will be indicated by a prefix
enclosed in parentheses. The group attached to C(21) will appear as
a suffix. A similar description will be used for 4, formally a pyrrole
addition product of 3. Here, the hypothetical trianion is noted as
(H,pyr)OCP. Consequently, the following acronyms correspond to
neutral structures [(H)OCPH]H 3, [(H,pyr)OCPH]H2 4, [(H,EtO)-
OCPH]H2 5, [(pyr,EtO)OCPH]H2 6, and [(pyr)OCPH]H 7.
(18) Schmidt, I.; Chmielewski, P. J. Tetrahedron Lett. 2001, 42, 1151.
(19) Hung, C.-H.; Chang, F.-C.; Lin, C.-Y.; Rachlewicz, K.; Ste¸pien´, M.;
Latos-Graz˘yn´ski, L.; Lee, G.-H.; Peng, S.-M. Inorg. Chem. 2004, 43,
4118.
(12) Lash, T. D.; Rasmussen, J. M.; Bergman, K. M.; Colby, D. A. Org.
Lett. 2004, 6, 549.
(13) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. J. Am. Chem. Soc. 2002, 124, 3838.
(14) Sprutta, N.; Latos-Graz˘yn´ski, L. Tetrahedron Lett. 1999, 40, 8457.
(15) Pawlicki, M.; Latos-Graz˘yn´ski, L. Chem.sEur. J. 2003, 9, 4650.
(16) Pawlicki, M.; Latos-Graz˘yn´ski, L. J. Org. Chem., 2005, 70, 9123.
(20) Rachlewicz, K.; Wang, S.-L.; Peng, C.-H.; Hung, C.-H.; Latos-
Graz˘yn´ski, L. Inorg. Chem. 2003, 42, 7348.
(21) Hilton, J.; Sutcliffe, L. H. Prog. NMR Spectrosc. 1975, 10, 27.
9780 Inorganic Chemistry, Vol. 44, No. 26, 2005

Side-on Coordination Mode of O-Confused Carbaporphyrin
Scheme 3. Coordination Modes of Pyrrole-Appended O-Confused Porphyrins
Results and Discussion
to the tetrahedral carbon atom, which differentiates two sides
of the macrocycle. At the same time, the 13C chemical shift
(111.8 ppm) is consistent with the tetrahedral hybridization
of C(3), which is linked to two oxygen atoms. The presence
of the ethoxy substituent is manifested by the diastereotopi-
cally split methylene multiplets at 3.86 and 3.35 ppm (Figure
2, trace A, inset). Essentially, the molecule 6 demonstrates
aromaticity due to the typical 18-π-electron delocalization
pathway (Scheme 3). The strongly upfield positions of the
H(21) (-5.55 ppm) and inner NH (-2.82, -3.07 ppm, 223
K) resonances are readily accounted for by the ring-current
effect.
True O-Confused Oxaporphyrin with a Pendant Pyr-
role Ring [(pyr)OCPH]H (7). Gradual addition of TFA to
a solution of 6 in dichloromethane transforms the neutral
form of 6 into the violet protonated form 7-H2, i.e., {[(pyr)-
OCPH]H3}2+ 7-H2 (Scheme 4). Titration followed by UV-
vis spectroscopy proceeds with well-defined isosbestic points,
and the final spectrum of 7-H2 is shown in Figure 1. The
strong Soret band of 6 disappeared. Several bands in the
region typically assigned to the Soret-like band of aromatic
carbaporphyrinoids, however, could be detected, but their
low extinction coefficients, ca. ꢀ ) 8 × 103, imply lowering
of the aromatic character of 7-H2.
Synthesis of [(EtO,pyr)OCPH]H2. As described previ-
ously, the condensation of 2,4-bis(phenylhydroxymethyl)-
furan with pyrrole and p-tolylaldehyde (1:3:2 molar ratio)
via a one-pot, two-step, room-temperature synthesis yielded
a pyrrole adduct of 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-
21-carbaporphyrin 4.15 Originally, we focused our attention
on the coordinating properties of 4. In terms of present
studies, the facile transformation of [(H,pyr)OCP]AgIII 4-Ag
into [(C2H5O,pyr)OCP]AgIII 6-Ag (Scheme 3) via ethoxy
substitution is of particular interest.15 Significantly, a sub-
sequent acidification of 6-Ag yielded the silver(III) complex
of true O-confused oxaporphyrin, albeit with appended
pyrrole ring [(pyr)OCP]AgIII]+ 7-Ag. Presumably, the silver-
(III) cation activates the ligand perimeter, allowing for the
facile changes centered at the C(3) position. In principle, an
extrusion of silver from 6-Ag or 7-Ag using strong acid
should afford 7, which was never the case despite several
attempts.
The pyrrole adduct of 2-oxa-21-carbaporphyrin 4 under-
goes a substitution when treated with ethoxide in ethanol.
In comparison, to synthesize 7-Ag from 6-Ag,15 we carried
out the reaction, which requires an elevated temperature, in
a boiling solution of sodium ethoxide. The chromatographic
workup of the resulting mixture gave 6 practically in
quantitative yield. The structure of 6 was confirmed by a
combination of high-resolution mass spectrometry and NMR
spectroscopy.
The 1H NMR spectroscopic titration of 6 with TFA carried
out in CD2Cl2 at 298 K demonstrated a gradual growth of a
separate set of resonances assigned directly to 7-H2 (Figure
2, Scheme 4). A new aromatic carbaporphyrinoid 7-H2 has
been formed via an exocyclic C(3)-O bond cleavage,
presumably activated by protonation of the ethoxy group and
followed by elimination of ethanol. In the course of this
Spectroscopic Characterization of [(EtO,pyr)OCPH]H2
(6). The electronic spectrum of [(EtO,pyr)OCPH]H2 6 (Figure
1, blue), with its intense Soret-like band (433 nm in CH2-
Cl2) and a set of bands in the Q region, reflects the aromatic
character of this new ligand.
1
The H NMR spectrum of 6 (Figure 2, trace A) shows
three AB patterns assigned to three pyrrole rings at the
position expected for an aromatic carbaporphyrinoid. The
1
complete assignments of all H NMR resonances for 6,
1
shown in Figure 2, have been obtained by means of 2D H
NMR COSY and NOESY experiments using the unique
NOE correlation between CH2 and o-H(5-phenyl) as a
starting point. The ethoxy group and pyrrole ring are bound
Figure 1. Electronic spectra of 6 (blue), 7-H2 (red), and 7 (green) in CH2-
(22) Contreras, R. H.; Facelli, J. C. Annu. Rep. NMR Spectrosc. 1993, 27,
255.
Cl2.
Inorganic Chemistry, Vol. 44, No. 26, 2005 9781

Pawlicki et al.
methylene multiplet of 6 has been replaced by a quartet of
the free ethanol. Importantly, 1 equiv of ethanol was released,
as confirmed by careful integration of the alcohol resonances
with respect to those of 7-H2. The careful neutralization of
7-H2 with triethylamine produced 7.
The 1H NMR spectrum of 7-H2 (Figure 2, trace B) shows
three AB patterns assigned to three pyrrole rings. The NH
groups gave three broad singlets at 4.16, 4.12, and 4.00 ppm
(233 K), i.e., upfield with respect to the NH resonance of
unsubstituted pyrrole. The unique inner C(21)H resonance
of the inverted furan ring is located at -0.51 ppm, i.e.,
upfield with respect to the corresponding 3-H resonance of
furan (6.07 ppm).15 The free base 7 obtained by deprotonation
of 7-H2 with TEA preserves the character observed for the
dicationic form, but with lowered aromatic character in
comparison to 6. Thus the 1H NMR spectrum of 7 contains
three AB systems, with typical scalar coupling constants (ca.
5 Hz) assigned to the â-pyrrolic protons. An upfield
relocation of the pyrrole protons (7.85-7.39 ppm) in
comparison to the same positions in 7-H2, accompanied by
downfield relocation of H(21) (7-H2, -0.51; 7, 2.38 ppm),
reflects lowering of the aromatic character in 7.
1
One can consider the H NMR shifts of the internally
located CH proton and the peripheral pyrrole resonances as
a convenient spectroscopic criterion of carbaporphyrinoid
aromaticity. Under these terms, 7 and 7-H2 present a
relatively small degree of aromaticity, similar to that detected
previously for selected carbaporphyrinoids.14,23,24
Coordination of Zn(II) and Cd(II) by O-Confused
Oxaporphyrin. Insertion of zinc(II), cadmium(II), and
nickel(II) into 7 has been readily achieved by boiling a
mixture of the free base and an appropriate salt, usually
anhydrous chloride, in a chloroform or chloroform/THF
solution (Scheme 5).
Figure 2. 1H NMR spectra of (A) 6, (B) 7-H2, and (C) 7 (dichloromethane-
d2, 298 K). The diastereotopic splitting of the CH2 resonances of 3-ethoxide
of 6 is shown in trace A. Insets B and C present the NH and H(21)
resonances.
Scheme 4. Reactivity of Oxacarbaporphyrin with Appended Pyrrole
In all cases, yields are quantitative (see Experimental
Section). The resulting complexes will be denoted [(pyr)-
OCPH]ZnIICl 7-ZnCl, [(pyr)OCPH]CdIICl 7-CdCl, and [(py-
r)OCP]NiII 7-Ni. Significantly, 7-Ni was previously obtained
by a different route, i.e., by insertion of nickel(II) into 4.15
The insertion process was then accompanied by the dehy-
drogenation step, and the macrocyclic ring that is formed
corresponds to the true oxaporphyrin, although it’s embedded
into its 3-substituted form of 7. The nickel(II) ion of [(pyr)-
OCP]NiII is bound by three pyrrolic nitrogens and a trigonally
hybridized C(21) atom of the inverted furan.15
In contrast to nickel(II), the zinc(II) and cadmium(II) ions
do not form a regular metal-carbon bond (Scheme 5). The
macrocycle acts as a monoanionic ligand, and a compensa-
tion of the metal charge requires an axial chloride coordina-
tion. Three nitrogen atoms and the CH fragment of the
inverted furan occupy equatorial positions.
Spectroscopic Characterization of 7-ZnCl and 7-CdCl.
The electronic spectra registered for 7-ZnCl and 7-CdCl
(Figure 3) present complex patterns characteristic for the true
(23) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Głowiak, T. J. Am. Chem.
Soc. 1996, 118, 5690.
(24) Lash, T. D.; Chaney, S. T. Angew. Chem., Int. Ed. 1997, 36, 839.
reversible process, the tetrahedral-trigonal rearrangements
originate at the C(3) atom. The diastereotopically split ethoxy
9782 Inorganic Chemistry, Vol. 44, No. 26, 2005

Side-on Coordination Mode of O-Confused Carbaporphyrin
Scheme 5. Insertion of Metal Ions
Figure 4. 1H NMR spectra of (A) 7-ZnCl and (B) 7-CdCl (chloroform-d,
298 K). (C) 1D gsHSQC for 7-CdCl. Insets (not to scale) A1 and B1 show
the H(21) resonance for 7-ZnCl and 7-CdCl, respectively. The coupling to
111/113Cd is marked in inset B1.
be extracted from the 1D spectrum using appropriate filtering
techniques (Figure 4, trace C). â-Pyrrolic protons of 7-CdCl
exhibit the usual four-bond couplings to 111/113Cd (ca. 4.5
Hz), also observed for regular cadmium(II) porphyrins and
cadmium(II) benziporphyrins.8,13,25
O-confused oxaporphyrin with appended pyrrole or its
complexes.15 The analogical, complex patterns have been
observed for 7 and its dicationic form 7-H2 (Figure 1) as
well. Presumably, the absorption band at ca. 900 nm reflects
the conjugation of the appended pyrrole ring with the
O-confused porphyrin macrocycle.
The H(21) pattern displayed by 7-CdCl is shown in inset
B1 of Figure 3. The central line, which corresponds to the
molecules containing spin-inactive Cd isotopes, is flanked
with a pair of satellites. Significantly, the 111/113Cd satellites
(J ) 10.4 Hz) are detected for the (21)H signal (inset B1 of
Figure 4). This coupling is too effective to be of the usual
through-bond origin, because the metal nucleus and the
proton of the inverted furan are five bonds apart and the
geometry of the bond path is unfavorable. These couplings
are therefore a result of the weak cadmium-(21)H interac-
tion. In structural terms, the detected coupling reflects the
spatial proximity between the cadmium ion and the furan
fragment. The coupling constant value is slightly larger
compared to that of cadmium(II) benziporphyrin.8
The interaction of the metal ion and C(21)H is reflected
by carbon chemical shifts. The C(21) resonances of 7-CdCl
and 7-ZnCl have been detected at 78.3 and 81.4 ppm,
respectively. Thus they experience a remarkable upfield
change relative to free base 7 (101.3 ppm). Analogously,
the C(22) signals of the Zn(II), Cd(II), and Hg(II) complexes
of m-benziporphyrin complexes experience remarkable up-
field shifts relative to free base 1 (up to 26.6 ppm).
Significantly, the molecular structure of m-benziporphyrin
complexes supports the side-on interaction between the metal
ion and benzene.8 The proper tetrahedral geometry of an
internal carbon is reflected by the characteristic carbon shift
(33.4 ppm), as observed for nickel(II) complexes of alky-
lated26 and protonated N-confused porphyrin.27
1
The H NMR spectra observed for 7-ZnCl and 7-CdCl
are presented in Figure 4. The 1H NMR spectrum of 7-ZnCl
(Figure 4, trace A) shows three AB patterns located according
to the COSY map (8.28, 7.75 (3J ) 4.9 Hz); 8.18, 7.84 (3J
) 4.9 Hz); 7.80, 7.77 (3J ) 4.9 Hz)) and assigned to three
pyrrole rings. The unique inner C(21)H resonance of the
inverted furan ring is located at 0.15 ppm, i.e., slightly upfield
with respect to the corresponding (21)H resonance of 7. The
downfield relocation of â-H resonances of 7-ZnCl as
compared to those of 7 suggests some increase of ring current
effect due to coordination of the metal ion. The chemical
shifts determined for 7-CdCl resemble those of 7-ZnCl.
The proximity of the furan fragment to the metal ion
induces direct scalar couplings between the spin-active
nucleus of the metal (111/113Cd) and the adjacent 1H nucleus.
Interaction with the spin-active Cd nuclei leads to scalar
couplings observed in the 1H NMR spectra of 7-CdCl. These
couplings generate characteristic satellite patterns, which can
(25) Jakobsen, H. J.; Ellis, P. D.; Inners, R. R.; Jensen, C. F. J. Am. Chem.
Soc. 1982, 104, 7742.
(26) Schmidt, I.; Chmielewski, P. J. Chem. Commun. 2002, 92.
(27) Schmidt, I.; Chmielewski, P. J.; Ciunik, Z. J. Org. Chem. 2002, 67,
8917.
Figure 3. Electronic spectra of 7-ZnCl (blue) and 7-CdCl (red) in CH2-
Cl2.
Inorganic Chemistry, Vol. 44, No. 26, 2005 9783

Pawlicki et al.
Table 1. 1H (13C) NMR Chemical Shift Values Observed for the
Appended Pyrrole Ring
3′
4′
5′
21
pyrrole
6
7
7-H2
7-Ni15
7-ZnCl
7-CdCl
6.22 (108.2) 6.22 (108.2) 6.68 (118.5)
5.53 (107.3) 5.93 (108.9) 6.45 (116.5) -5.55 (111.8)
6.64 (124.6) 6.17 (114.7) 6.97 (131.9) -0.41 (101.3)
6.10 (116.5) 6.00 (111.2) 6.56 (123.8)
6.34 (119.2) 6.17 (111.9) 6.76 (126.4)
5.82 (117.1) 5.88 (111.5) 6.52 (124.3)
5.80 (116.2) 5.89 (111.0) 6.54 (123.6)
2.39 (109.1)
0.17 (81.8)
0.21 (78.3)
dipyrromethene 6.64 (128.8) 6.39 (117.2) 7.63 (143.1)
The analysis of the 13C chemical shifts registered for the
appended pyrrole ring of 7-ZnCl and 7-CdCl (Table 1)
provides essential insight into the different roles of the
pyrrole fragment, underscoring the direct electronic effects.
The ring-current contributions to overall changes in 13C
chemical shifts are negligible. For the sake of comparison,
the respective chemical shift values of the free pyrrole and
the conjugated pyrrole ring of 5-anisol-dipyrromethene15 have
been included in Table 1. These values set the spectroscopic
standards for two extreme structures of the appended pyrrole.
The analysis of the 13C chemical shifts registered for the
appended pyrrole ring of 7-ZnCl and 7-CdCl (Table 1)
suggests an effective conjugation between the macrocycle
and appended pyrrole moiety. In terms of 13C chemical shifts,
it is clear that the extent of the conjugation resembles one
characteristic for [(pyr)OCP]NiII.15
Figure 5. DFT calculated geometries of 7 (A) and 7-CdCl (B). The upper
traces present the perspective projection, whereas the bottom one shows
the side view (aryl groups omitted for clarity). The 7-ZnCl structure is nearly
identical to that of the cadmium compound (see text for details).
Here, we have performed the DFT calculations for 7-ZnCl
and 7-CdCl. We have found it necessary to include in
calculations m-aryl substituents despite a required substantial
computational effort. Previously, we found that the absence
of m-aryl produces substantial differences in the optimized
macrocyclic geometry.8,28,29 For comparison, we have carried
out the DFT optimization (B3LYP/6-31G**) of the free base
7. NICS (nucleus-independent chemical shift) values30-36
have been determined for the optimized structures 7 at a
center of the porphyrinoid crevice. The global NICS value
for 7 is -2.42 ppm (the value at 1 Å above the center is
-2.98 ppm), consistent with the observation that the diatropic
The remarkable changes of the appended pyrrole 1H NMR
pattern have been observed in the analyzed 7-H2, 7, 7-ZnCl,
and 7-CdCl series (Table 1). The marked upfield relocation
of the 7-ZnCl and 7-CdCl resonances with respect to 7-H2
or 7 is the most analytically important. As shown by the
X-ray study, the macrocycle of 7-Ni is only slightly distorted
from planarity.15 The dihedral angle between the macrocyclic
and appended pyrrole plane reflects the biphenyl-like ar-
rangement and equals 26.4°. The DFT calculations afford a
similar structure for 7. The visible puckering of the macro-
cycle and the large tilt of furan have been found in the
optimized structure of 7 (see below). Thus the reasons for
1
effect in H NMR is relatively small.
The two DFT-optimized structures 7-ZnCl and 7-CdCl
(B3LYP/LANL2DZ) are very similar (Figure 5). The opti-
mized structural parameters are contained in the Supporting
Information. The Cd ion in 7-CdCl is displaced from the N3
plane by ca. 0.51 Å toward the chloride. A slightly smaller
displacement has been found for zinc(II) of 7-ZnCl (0.18
Å). The degrees of tilt adopted by the furan moieties in
7-ZnCl (48.9°) and 7-CdCl (49.0°) as expressed by the C4O/
N3 dihedral angles (given in parentheses) are remarkably
large as compared to that of the crystal structure of 7-Ni
(5.7°)15 or the DFT-optimized structure of 7 (23.2°).
1
the H NMR chemical shift changes are complex, as the
simultaneous modification of the macrocyclic ring current
and the molecular structure of the furan-appended pyrrole
fragment are important.
The optimized bond lengths (see the Supporting Informa-
tion) resemble those found by X-ray crystallography for zinc-
(II) and cadmium(II) carbaporphyrins.8,13,37 The dihedral
angles between furan and appended pyrrole equal 38.8° and
41.4° for 7-ZnCl and 7-CdCl, respectively. The optimized
M‚‚‚C(21) and M‚‚‚H(21) distances are 2.73 and 2.81 Å for
Cd(II), and 2.70 and 2.71 Å for Zn(II), respectively. The
distances resemble those determined by X-ray structure for
cadmium(II) m-benziporphyrin, in which scalar coupling was
DFT Studies. In metal complexes 7-ZnCl and 7-CdCl,
the reasonable conformation of the macrocycle has the furan
ring tilted away from the metal center, with the inner CH
bonds and the axial MCl bond in an anti orientation. The
observation of scalar coupling between the Cd nucleus and
H(21) in 7-CdCl indicates that there must be a certain
accumulation of electron density between the metal and furan
to transmit the coupling. This observation indicates that the
furan fragment approaches the cadmium ion at a distance
much shorter than the sum of the van der Waals radii. To
approach this problem, we have applied the density functional
theory (DFT) in a way similar to that previously described
for m-benziporphyrin and p-benziporphyrin complexes.8,28
(29) Szterenberg, L.; Latos-Graz˘yn´ski, L. THEOCHEM 1999, 490, 33.
(30) Schleyer, P. v. R.; Meaerker, C.; Dransfeld, A.; Jiao, H.; Hommes,
N. J. R. v. E. J. Am. Chem. Soc. 1996, 118, 6317.
(31) Cyran´ski, M. K.; Krygowski, T. M.; Wisiorowski, M.; Hommes, N.
J. R. v. E.; Schleyer, P. v. R. Angew. Chem., Int. Ed. 1998, 37, 177.
(32) Schleyer, P. v. R.; Manoharan, M.; Wang, Z.-X.; Kiran, B.; Jiao, H.;
Puchta, R.; Hommes, N. J. R. v. E. Org. Lett. 2001, 3, 2465.
(33) Krygowski, T. M.; Cyran´ski, M. K. Chem. ReV. 2001, 101, 1385.
(34) Furuta, H.; Maeda, H.; Osuka, A. J. Org. Chem. 2001, 66, 8563.
(35) Kawase, T.; Oda, M. Angew. Chem., Int. Ed. 2004, 43, 4396.
(36) Okazaki, T.; Laali, K. L. J. Org. Chem. 2004, 69, 510.
(28) Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Szterenberg, L. Inorg. Chem. 2004,
43, 6654.
(37) Furuta, H.; Ishizuka, T.; Osuka, A. J. Am. Chem. Soc. 2002, 124, 5622.
9784 Inorganic Chemistry, Vol. 44, No. 26, 2005

Side-on Coordination Mode of O-Confused Carbaporphyrin
also detected.8 A shorter distance was determined for the
zinc(II) N-confused porphyrin complex (2.49 Å).37-39 The
Cd‚‚‚C(21) distance in 7-CdCl exceeds the typical Cd-C
bond length (2.10-2.35 Å),40 but is much shorter than the
corresponding van der Waals contact (3.3 Å).41 Similarly,
the Zn‚‚‚C(21) distance in 7-ZnCl exceeds the typical Zn-C
bond length (1.984-1.987 Å),40,42 but is much shorter than
the corresponding van der Waals contact (3.1 Å).41
(two times). The remaining green solid was dissolved in fresh
distilled dichloromethane, and was filtered. The obtained solution
was purified with a chromatographic column filled with aluminum
oxide (GII). The fast-moving brown fraction was collected and
evaporated to give 6 with quantitative yield. 1H NMR (500.13 MHz,
3
3
CD2Cl2): δ 8.58 (d, 1H, J ) 4.6 Hz), 8.56 (d, 1H, J ) 4.6 Hz),
8.55 (d, 1H, 3J ) 4.6 Hz), 8.53 (d, 1H, 3J ) 4.6 Hz), 8.51 (d, 1H,
3J ) 4.9 Hz), 8.20 (d, 1H, 3J ) 4.9 Hz), 8.14 (m, 3H), 8.06 (d, 1H,
3
3J ) 8 Hz), 8.03-7.97 (m, 3H), 7.9 (d, 1H, J ) 8 Hz), 7.72 (t,
3
2H), 7.65-7.49 (m, 9H), 7.25 (m, 1H), 6.92 (d, 1H, J ) 8 Hz),
Conclusion
6.49 (m, 1H), 5.90 (m, 1H), 5.39 (m, 1H), 3.86 (m, 1H), 3.35 (m,
1H), 2.68 (s, 3H), 2.66 (s, 3H), 1.21 (t, 3H), -5.55 (s, 1H). 13C
NMR (125.7 MHz, CDCl3): δ 156.2, 153.4, 152.9, 140.5, 139.7,
139.5, 139.45, 139.4, 139.0, 138.7, 137.5, 137.4, 135.7, 134.9,
134.5, 134.3, 134.2, 133.7, 133.4, 133.1, 132.7, 132.4, 128.0,
127.75, 127.72, 127.70, 127.5, 127.1, 126.4, 126.2, 126.0, 125.9,
124.5, 123.8, 121.1, 120.2, 116.3, 114.8, 111.8, 108.7, 107.1, 106.1,
105.1, 105.0, 58.9, 21.7, 21.7, 15.2. UV-vis (λmax (nm), log ꢀ):
433 (4.71), 528 (2.63), 562 (2.49), 613 (2.27), 669 (2.42). HRMS
(ESI, m/z): calcd for [C52H42N4O2 + H+], 755.3386; found,
755.3381.
In the present work, we have described the isolation and
reactivity of the true O-confused oxaporphyrin, albeit with
an appended pyrrole ring covalently linked at the C(3)
position. The pyrrole-appended O-confused oxaporphyrin
molecule, applied as a ligand toward nickel(II), zinc(II), and
cadmium(II) metal ions, reveals the peculiar plasticity of its
molecular and electronic structure. The insertion of nickel-
(II) was accompanied by the dehydrogenation step, and the
macrocyclic ring formed corresponds to the true oxaporphy-
rin, although it’s embedded into its 3-substituted form. The
nickel(II) ion is bound by three pyrrolic nitrogens and a
trigonally hybridized C(21) atom of the inverted furan. In
contrast, the zinc(II) and cadmium(II) ions favor the different
coordination mode of oxacarbaporphyrin. Namely, the mac-
rocycle acts as a monoanionic ligand, and three nitrogen
atoms and the CH fragment of the inverted furan occupy
equatorial positions. Essentially, the oxidation state and the
size of the central metal ion can be considered to be a factor
that determines the molecular structure of the ligand. The
monoanionic, dianionic, or trianionic macrocyclic core of
pyrrole-appended derivatives has been favored to match
requirements of zinc(II), cadmium(II), nickel(II), palladium-
(II), and silver(III).
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-carba-
porphyrin Dication 7-H2. 6 (10 mg) was dissolved in 15 mL of
fresh distilled dichloromethane. The concentrated TFA was added
until the distinct color change from brown to violet was observed.
The crude product was recrystallized with CH2Cl2/hexane to give
7-H2 with almost quantitative yield (up to 97%). 1H NMR (500.13
3
MHz, CD2Cl2): δ 9.34 (bs, 1H), 8.51 (d, 2H, J ) 7.3 Hz), 8.43
(d, 2H, 3J ) 7.3 Hz), 8.34 (d, 1H, 3J ) 4.6 Hz), 8.33 (d, 1H, 3J )
4.9 Hz), 8.08-8.01 (m, 6H), 7.99 (d, 1H, 3J ) 4.6 Hz), 7.98-7.93
(m, 4H), 7.92-7.79 (m, 7H), 7.67-7.62 (m, 4H), 6.98 (m, 1H),
6.67 (m, 1H), 6.17 (m, 1H), 2.67 (s, 3H), 2.66 (s, 3H), -0.51 (s,
1H). 13C NMR (125.7 MHz, CD2Cl2): δ 152.2, 150.2, 149.8, 148.9,
148.1, 147.3, 146.2, 144.9, 141.6, 141.2, 140.9, 140.5, 138.8, 138.4,
137.1, 136.9, 139.7, 136.6, 135.7, 132.5, 131.8, 131.6, 131.4, 130.5,
130.4, 130.2, 129.5, 129.3, 129.1, 129.0, 128.7, 128.2, 124.8, 123.5,
122.8, 121.1, 117.2, 116.1, 114.9, 113.9, 101.1, 21.7, 21.6. UV-
vis (λmax (nm), log ꢀ): 356 (3.91), 389 (3.98), 444 (4.17), 472 (4.13),
533 (4.11), 573 (4.18), 652 (3.58), 708 (3.52), 911 (3.39). HRMS
(ESI, m/z): calcd for [C50H36N4O + H+], 709.2967; found,
709.2962.
In the present paper, we have described spectroscopic
manifestations of the side-on metal-arene interactions
observed in the diamagnetic Zn(II) and Cd(II) complexes.
The metal-furan interaction leads to scalar coupling between
the spin-active metal nucleus (111Cd, 113Cd) and the proximate
1H and 13C nuclei of the arene.
1
7. H NMR (500.13 MHz, CDCl3): δ 8.00 (m, 2H), 7.97 (m,
3
3
3H), 7.85 (d, 1H, J ) 4.9 Hz), 7.80 (d, 1H, J ) 4.6 Hz), 7.67-
3
3
7.57 (m, 13H), 7.48 (d, 1H, J ) 4.6 Hz), 7.39 (d, 1H, J ) 4.6
Hz), 7.35 (m, 4H), 6.56 (m, 1H), 6.10 (m, 1H), 6.00 (m, 1H), 4.47
(bs, 1H), 2.53 (s, 6H), 2.39 (s, 1H). UV-vis (λmax (nm), log ꢀ):
360 (4.04), 420 (4.18), 449 (4.15), 502 (4.17), 528 (sh), 627 (3.46),
681 (3.77), 809 (3.29), 883 (3.17).
Experimental Section
Solvents and Reagents. Chloroform-d and dichloromethane-d2
(both CIL) were used as received. The starting macrocycle 4 (5,20-
diphenyl-10,15-ditolyl-2-oxa-3-hydro-3-(2′-pyrrolilo)-21-carbapor-
phyrin) was obtained as previously described.15
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-ethoxy-3-(2′-pyrrolilo)-21-
carbaporphyrin 6. In a round-bottom flask, 10 mg of 4 was
dissolved in 30 mL of ethanol. To that solution was added metallic
sodium (7 mg), and the obtained mixture was refluxed for an
additional 30-40 min. After that time, the solvent was removed
with a vacuum rotary evaporator. The solid residue was dissolved
in a small volume of fresh distilled dichloromethane and evaporated
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-carba-
porphyinato Chlorozinc(II) 7-ZnCl. 7 (10 mg) was dissolved in
15 mL of chloroform with a small amount of fresh distilled
triethylamine (2 drops). Zinc(II) chloride (excess) was added in a
small volume of fresh distilled THF. After 20 min, the resulting
mixture was washed with water (3 × 20 mL). The organic layer
was dried with Na2SO4, filtered, and evaporated with a vacuum
rotary evaporator. The crude product was recrystallized with CHCl3/
1
hexane to gave 7-ZnCl with quantitative yield. H NMR (500.13
(38) Furuta, H.; Ishizuka, T.; Osuka, A. Inorg. Chem. Commun. 2003, 6,
398.
(39) Furuta, H.; Morimoto, T.; Osuka, A. Inorg. Chem. 2004, 43, 1618.
(40) Hursthouse, M. B.; Motevalli, M.; O’Brien, P.; Walsh, J. R.; Jones,
A. C. Organometallics 1991, 10, 3196.
(41) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(42) Dekker, J.; Boersma, J.; Fernholt, L.; Haaland, A.; Spek, A. L.
Organometallics 1987, 6, 1202.
MHz, CDCl3): δ 8.28 (d, 1H, 3J ) 4.9 Hz), 8.20 (d, 2H, 3J ) 7.3
Hz), 8.17 (d, 1H, 3J ) 4.9 Hz), 8.1 (bs, 1H), 8.09 (d, 1H, 3J ) 7.3
3
3
Hz), 7.84 (d, 1H, J ) 4.6 Hz), 7.8 (d, 1H, J ) 4.9 Hz), 7.79-
3
7.75 (m, 1H), 7.74 (d, 1H, J ) 4.9 Hz), 7.73-7.68 (m), 7.67-
7.62 (m), 7.38-7.34 (m, 4H), 6.52 (m, 1H), 5.88 (m, 1H), 5.77
(m, 1H), 2.55 (2xs, 6H), 0.15 (s, 1H). 13C NMR (125.7 MHz,
Inorganic Chemistry, Vol. 44, No. 26, 2005 9785

Pawlicki et al.
CDCl3): δ 162.7, 161.2, 157.4, 157.1, 152.8, 152.6, 148.8, 148.4,
140.8, 138.3, 137.9, 137.4, 137.2, 135.9, 135.4, 135.0, 134.4, 133.7,
133.5, 133.4, 132.8, 129.7, 129.3, 129.1, 128.9, 128.0, 127.9, 126.1,
125.1, 123.9, 122.6, 120.1, 118.3, 118.2, 116.6, 111.2, 81.4, 21.4.
UV-vis (λmax (nm), log ꢀ): 357 (4.60), 469 (4.81), 518 (4.76),
546 (4.79), 631 (4.07), 689 (4.25), 771 (3.99), 851 (4.36). HRMS
(ESI, m/z): calcd for C50H35N4OZn+, 771.2102; found, 771.2097.
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-carba-
porphyrinato Chlorocadmium(II) 7-CdCl. 7 (10 mg) was dis-
solved in 15 mL of chloroform with a small amount of fresh distilled
triethylamine (2 drops). Cadmium(II) chloride (excess) was added,
and the resulting mixture was refluxed for the next 30 min. After
that time, the solvent was removed with a vacuum rotary evaporator.
The remaining solid was dissolved in 20 mL of fresh distilled
dichloromethane, and washed with water (3 × 20 mL). The organic
layers were dried with Na2SO4, filtered, and evaporated. The crude
product was recrystallized with CHCl3/hexane to give 7-CdCl with
recorded on a diode array Hewlett-Packard 8453 spectrometer. Mass
spectra were recorded on an AD-604 spectrometer using the
electrospray and liquid matrix secondary-ion mass spectrometry
techniques.
DFT Calculations. DFT calculations for structures 7, 7-CdCl,
and 7-ZnCl were performed with the GAUSSIAN03 program.43
Geometry optimizations were carried out within unconstrained C1
symmetry. Becke’s three-parameter exchange functional44 with the
gradient-corrected correlation formula of Lee, Yang, and Parr (DFT-
(B3LYP))45 was used with the LANL2DZ basis set for metal
complexes,46 and with 6-31G** for the free base 7. Harmonic
vibrational frequencies were calculated for 7 (6-31G**), 7-ZnCl,
and 7-CdCl (LANL2DZ) using analytical second derivatives, in
order to establish the nature of the stationary points. All structures
were found to have converged to a minimum on the potential-energy
surface.
To probe the ring current in 7, we calculated the nucleus-
independent chemical shift (NICS) (HF/6-31G**/B3LYP/6-31G**).
1
quantitative yield. H NMR (500.13 MHz, CDCl3): δ 8.28 (bs,
1H), 8.21-8.15 (m, 3H), 8.12-8.08 (m, 3H), 7.81-7.61 (m, 14H),
7.40-7.35 (m, 4H), 6.54 (m, 1H), 5.89 (m, 1H), 5.79 (m, 1H),
2.55 (s, 6H), 0.21 (t, 1H, JH-Cd ) 10.4 Hz). 13C NMR (125.7 MHz,
CDCl3): δ 164.2, 162.4, 160.1, 159.5, 153.9, 153.5, 148.3, 141.0,
138.9, 138.6, 137.9, 137.5, 136.2, 135.8, 135.4, 135.0, 134.9, 134.8,
134.6, 133.9, 133.5, 129.7, 129.5, 129.3, 128.6, 128.3, 125.8, 124.1,
122.8, 119.9, 119.6, 116.7, 111.5, 78.3, 21.8. UV-vis (λmax (nm),
log ꢀ): 362 (4.55), 483 (4.76), 525 (4.74), 551 (4.73), 639 (3.92),
697 (4.01), 785 (4.07), 868 (4.42). MS (ESI, m/z): calcd for
C50H35N4O112Cd+, 819.3; found, 819.1.
Acknowledgment. This work was supported by the
Ministry of Scientific Research and Information Technology
of Poland under Grant 3 T09A 162 28. DFT calculations
were preformed at the Supercomputer Centers in Wrocław
and Poznan´.
Supporting Information Available: Bond lengths for DFT
optimized geometry and optimized structural parameters of 7,
7-CdCl, and 7-ZnCl. This material is available free of charge via
the Internet at http://pubs.acs.org.
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-carba-
porphyrinato Nickel(II) 7-Ni. 7 (10 mg) was dissolved in 15 mL
of chloroform with a small amount of fresh distilled triethylamine
(2 drops). To the resulting mixture was added nickel(II) chloride
(excess) dissolved in 10 mL of methanol, and the resulting mixture
was stirred for an additional 12 h. After that time, the solvent was
removed with a vacuum rotary evaporator. The remaining solid
was dissolved in a small amount of fresh distilled dichloromethane,
filtered, and chromatographed with silica gel (Mesh 35-70). The
fast-moving green fraction was collected, and was recrystallized
with CHCl3/MeOH to gave 7-Ni (yield 60%). The complex presents
spectroscopic properties identical to those previously described.15
Instrumentation. NMR spectra were recorded on a Bruker
Avance 500 spectrometer (frequencies: 1H 500.13 MHz, 13C 125.77
MHz, 113Cd 106.05 MHz) equipped with either a broadband inverse
gradient probehead or a direct broadband probehead. A 1D variant
of a gradient-selected HSQC sequence was employed to record the
113Cd-filtered spectra, with evolution times optimized for the
observed range of coupling constants. Absorption spectra were
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9786 Inorganic Chemistry, Vol. 44, No. 26, 2005