1H NMR investigation of high-spin and low-spin iron(III) meso-ethynylporphyrins

Article abstract of DOI:10.1021/ic050158q

The ¹H NMR spectra of iron(III) 5-ethynyl-10,15,20-tri(p-tolyl) porphyrin [(ETrTP)Fe^IIX_n], iron(III) 5-(phenylethynyl)-10, 15,20-tri(p-tolyl)porphyrin [(PETrTP)Fe^IIIX_n], iron(III) 5-(phenylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin [(PBTrTP)-Fe ^IIIX_n], iron(III) 5,10,15,20-tetra(phenylethynyl)porphyrin [(TPEP)Fe^IIIX_n], iron(III) 1,4-bis-[10,15,20-tri(p-tolyl) porphyrin-5-yl]-1,3-butadiyne {[(TrTP)Fe^IIIX_n] ₂B} and 5,10,15-triphenylporphyrin [(TrPP)Fe^IIIX _n] have been studied to elucidate the impact of meso-ethynyl substitution on the electronic structure and spin density distribution of high-spin (X = Cl^-, n = 1) and low-spin (X = CN^-, n = 2) derivatives. The meso substituents, i.e., ethynyl, phenylethynyl, and phenylbutadiynyl, provided insight into the efficiency of spin density delocalization along structural elements that are typically applied to transmit electronic effects along multipart polyporphyrinic systems. The positive spin density localized at the meso-carbon of high-spin iron(III) ethynylporphyrins is effectively delocalized along the ethyne or butadiyne fragment as illustrated by the comparison of isotropic shifts of C_meSo-H and -CC-H determined for (TrPP)Fe^IIICl (-82.6 ppm, 293 K) and (ETrTP)Fe^IIICl (-49.5 ppm, 298 K). The replacement of the ethynyl hydrogen by phenyl or phenylethynyl provided evidence for the π spin density distribution around the introduced phenyl ring. An analysis of the isotropic shifts for the low-spin bis-cyanide iron(III) porphyrins series reveals the analogous mechanism of spin density transfer. Treatment of high-spin [(TrTP)Fe^IIICl] ₂B with a base resulted in formation of the cyclic [(TrTP)Fe ^IIIOFe^III(TrTP)B]₂ complex linked by two μ-oxo bridges. (TPEP)H₂ has been characterized by X-ray crystallography as a porphyrin dication where two molecules of trifluoroacetic acid associate with two coordinated trifluoroacetate anions. The X-ray structure of bis-tetrahydrofuran 1,4-bis[10,15,20-tri(p-tolyl)porphyrinatozinc(II)-5-yl]- 1,3-butadiyne complex {[(TrTP)Zn^II(THF)]₂B} reveals two parallel, non-coplanar [(TrTP)Zn(THF)] subunits linked by the linear butadiyne moiety.

Full text of DOI:10.1021/ic050158q

Inorg. Chem. 2005, 44, 4522−4533
1H NMR Investigation of High-Spin and Low-Spin Iron(III)
meso-Ethynylporphyrins
Anna Berlicka, Lechosław Latos-Graz3yn´ski,* and Tadeusz Lis
Department of Chemistry, UniVersity of Wrocław, 50 383 Wrocław, Poland
Received January 31, 2005
The 1H NMR spectra of iron(III) 5-ethynyl-10,15,20-tri(p-tolyl)porphyrin [(ETrTP)FeIIIXn], iron(III) 5-(phenylethynyl)-
10,15,20-tri(p-tolyl)porphyrin [(PETrTP)FeIIIXn], iron(III) 5-(phenylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin [(PBTrTP)-
FeIIIXn], iron(III) 5,10,15,20-tetra(phenylethynyl)porphyrin [(TPEP)FeIIIXn], iron(III) 1,4-bis-[10,15,20-tri(p-tolyl)porphyrin-
5-yl]-1,3-butadiyne
the impact of meso-ethynyl substitution on the electronic structure and spin density distribution of high-spin (X
Cl-, n CN-, n
1) and low-spin (X 2) derivatives. The meso substituents, i.e., ethynyl, phenylethynyl, and
{ }
[(TrTP)FeIIIXn]2B , and 5,10,15-triphenylporphyrin [(TrPP)FeIIIXn] have been studied to elucidate
)
)
)
)
phenylbutadiynyl, provided insight into the efficiency of spin density delocalization along structural elements that
are typically applied to transmit electronic effects along multipart polyporphyrinic systems. The positive spin density
localized at the meso-carbon of high-spin iron(III) ethynylporphyrins is effectively delocalized along the ethyne or
butadiyne fragment as illustrated by the comparison of isotropic shifts of Cmeso
(TrPP)FeIIICl ( 82.6 ppm, 293 K) and (ETrTP)FeIIICl (
49.5 ppm, 298 K). The replacement of the ethynyl hydrogen
by phenyl or phenylethynyl provided evidence for the spin density distribution around the introduced phenyl ring.
−H and −CC−H determined for
−
−
π
An analysis of the isotropic shifts for the low-spin bis-cyanide iron(III) porphyrins series reveals the analogous
mechanism of spin density transfer. Treatment of high-spin [(TrTP)FeIIICl]2B with a base resulted in formation of
the cyclic [(TrTP)FeIIIOFeIII(TrTP)B]2 complex linked by two
µ-oxo bridges. (TPEP)H2 has been characterized by
X-ray crystallography as a porphyrin dication where two molecules of trifluoroacetic acid associate with two coordinated
trifluoroacetate anions. The X-ray structure of bis-tetrahydrofuran 1,4-bis[10,15,20-tri(p-tolyl)porphyrinatozinc(II)-5-
yl]-1,3-butadiyne complex
{
[(TrTP)ZnII(THF)]2B
}
reveals two parallel, non-coplanar [(TrTP)Zn(THF)] subunits linked
by the linear butadiyne moiety.
Introduction
allows unambiguous assignments of the electronic structure
based on characteristic hyperfine shift patterns for various
functional groups. The hyperfine shift pattern is distinct for
each oxidation/spin/ligation state of iron porphyrins.
Several modifications of iron porphyrins that allow fine-
tuning of electronic properties including the spin density
distribution have been explored. For instance, the spin density
distribution in iron(III) porphyrins can be controlled by the
following molecular features: controlled substitution at the
3 and 8 positions of deuterioporphyrin;5 the nature of the
substituents and the pattern of their distribution in iron(III)
The electronic structure of iron porphyrins represents a
continuously active and challenging area of research, espe-
cially because of the relevance of such studies to the structure
and function of catalytic systems based on hemoproteins and
1
iron porphyrins. In this line of investigations, H NMR
spectroscopy provides a particularly useful tool for character-
izing the oxidation/spin/ligation states of paramagnetic
hemoproteins and iron porphyrins.1-4 The interaction with
unpaired spin(s) at the metal ion induces large hyperfine
shifts for the substituent protons of iron porphyrins, and this
(3) Banci, L.; Bertini, I.; Luchinat, C.; Turano, P. Solutions Sturctures of
Hemoproteins. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic Press: San Diego, CA, 2000; pp
323-350.
(4) La Mar, G. N.; Satterlee, J. D.; De Ropp, J. S. Nuclear Magnetic
Resonance of Hemoproteins. In The Porphyrin Handbook; Kadish,
K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: San Diego,
CA, 2000; pp 185-298.
* To whom correspondence should be addressed. E-mail: LLG@
wchuwr.chem.uni.wroc.pl.
(1) Walker, F. A. Proton NMR and EPR Spectroscopy of Paramagnetic
Metalloporphyrins. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic Press: San Diego, CA, 2000; pp
81-183.
(2) Walker, F. A. Inorg. Chem. 2003, 42, 4526.
4522 Inorganic Chemistry, Vol. 44, No. 13, 2005
10.1021/ic050158q CCC: $30.25
© 2005 American Chemical Society
Published on Web 05/28/2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
octa-â-substituted porphyrin isomers;6 monosubstitution of
the â-pyrrole position of tetraphenylporphyrins;7 meso
substitution of 5,10,15-triphenylporphyrin;8 substitution of
the meso-phenyl ring(s) in iron(III) tetraphenylporphyrins;1,9
saturation of pyrrole rings to form iron(III) chlorins, sulf-
hemins, or dioxoisobacteriochlorin;10-12 the mutual orienta-
tion of planar nitrogen bases coordinated in axial positions;13
and the π-acceptor character of the axial ligand.14 Recent
studies have documented that the replacement of meso-aryl
substituents of extensively investigated 5,10,15,20-tetrarylpor-
phyrins by alkyl groups profoundly influences the molecular
and electronic structures of iron(III) porphyrins.15-18
its linear geometrysis expected to generate minimal steric
hindrance, which might favor an overall planar geometry of
the macrocycle. The electronic structure of the ethynyl(s)
allows the extensive conjugation with the porphyrinic mac-
rocycle readily accounting for the general features of alkynyl
porphyrins, which include significantly red-shifted absorption
spectra and less negative reduction potentials.27
The investigation of ethynylporphyrins originated with the
synthesis of nickel(II) octaethylporphyrin bearing the ethynyl
group at the meso position.28 Further synthetic studies yielded
tetraethynyl-substituted porphyrins.29-31 Eventually, porphy-
rins bearing arylethynyl substituents at four meso positions
were synthesized.32,33 The arylethynyl moieties allow the
electronic structure to be tuned and the solubility of the
porphyrin to be increased,32-37 as readily illustrated by the
fact that 5,10,15,20-tetra(phenylethynyl)porphyrin (common
name chlorphyrin) yields, untypical for meso-substituted
porphyrins, a green solution.32 Ethynyl- or butadiynyl-linked
multiporphyrin arrays have also been synthesized and
characterized.38-41 Such compounds belong to the larger class
of multiporphyrins that have been explored as light-harvest-
ing antennas and charge-separation devices for studies in
artificial photosynthesis.42-44
In this Article, we study the impact of the meso substitu-
tion of iron(III) porphyrin by ethynyl moiety(ies) on the 1H
NMR properties. Representative examples of the ethynylpor-
phyrin class, namely, 5-ethynyl-10,15,20-tri(p-tolyl)porphyrin
(1), 5-(phenylethynyl)-10,15,20-tri(p-tolyl)porphyrin (2),
5-(phenylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin (3), 5,-
10,15,20-tetra(phenylethynyl)porphyrin (4), and 1,4-bis-[10,-
15,20-tri(p-tolyl)porphyrin-5-yl]-1,3-butadiyne (5), were cho-
sen for these investigations (Chart 1). The resonances of the
pyrrole hydrogens provide a direct probe of the electronic
structure and spin density around the porphyrin macrocycle.
The transfer of the spin density along ethyne and butadiyne
linkers has been of the special interest. These structural
Apart from perimeter substitution, a fundamentally dif-
ferent approach involving core alteration has been suggested
as an independent route for control of the iron porphyrin
electronic and molecular structure.19-21 The specific proper-
ties of iron porphyrin isomers have provided noteworthy
insight into properties of iron porphyrins as well.22-26
Here, in the search for suitable means to control electronic
structures and spectroscopic properties of iron(III) porphy-
rins, we have decided to probe a distinctive class of meso-
substituted porphyrins, namely, ethynylporphyrins. Ethyn-
ylporphyrins have at least one meso-carbon directly linked
to the ethynyl group.27 The ethynyl substituentsbecause of
(5) La Mar, G. N.; Viscio, D. B.; Smith, K. M.; Caughey, W. S.; Smith,
M. L. J. Am. Chem. Soc. 1978, 100, 8085.
(6) Isaac, M. F.; Lin, Q.; Simonis, U.; Suffian, D. J.; Wilson, D. L.;
Walker, F. A. Inorg. Chem. 1993, 32, 4030.
(7) Wojaczyn´ski, J.; Latos-Graz˘yn´ski, L.; Hrycyk, W.; Pacholska, E.;
Rachlewicz, K.; Szterenberg, L. Inorg. Chem. 1996, 35, 6861.
(8) Wojaczyn´ski, J.; Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Eur. J. Inorg. Chem.
2002, 7, 1806.
(9) Walker, F. A.; Balke, V. L.; McDermott, G. A. J. Am. Chem. Soc.
1982, 104, 1569.
(10) Chatfield, M. J.; La Mar, G. N.; Parker, W. O.; Smith, K. M.; Leung,
H. K.; Morris, I. K. J. Am. Chem. Soc. 1988, 110, 6352.
(11) Liccocia, S.; Chatfield, M. J.; La Mar, G. N.; Smith, K. M.; Mansfield,
K. E.; Anderson, R. R. J. Am. Chem. Soc. 1989, 111, 6087.
(12) Barkigia, K. M.; Chang, C. K.; Fajer, J.; Renner, M. W. J. Am. Chem.
Soc. 1992, 114, 1701.
(13) Walker, F. A.; Simonis, U. J. Am. Chem. Soc. 1991, 113, 8652.
(14) Simonneaux, G.; Schunemann, V.; Morice, C.; Carel, L.; Toupet, L.;
Winkler, H.; Trautwein, A. X.; Walker, F. A. J. Am. Chem. Soc. 2000,
122, 4366.
(28) Arnold, D. P.; Johnson, A. W.; Mahendran, M. J. Chem. Soc., Perkin
Trans. 1 1978, 366.
(29) Proess, G.; Panker, D.; Hevesi, L. Tetrahedron Lett. 1992, 33, 269.
(30) Krivokapic, A.; Cowley, A. R.; Anderson, H. L. J. Org. Chem. 2003,
68, 1089.
(31) Anderson, H. L. Tetrahedron Lett. 1992, 33, 1101.
(32) Milgrom, L.; Yahioglu, G. Tetrahedron Lett. 1995, 36, 9061.
(33) Milgrom, L.; Rees, R. D.; Yahioglu, G. Tetrahedron Lett. 1997, 38,
4905.
(34) Jiang, B.; Yang, S.-W.; Barbini, D. C.; Jones, W. E., Jr. Chem. Comun.
1998, 213.
(35) Plater, M. J.; Aiken, S.; Bourhill, G. Tetrahedron 2002, 58, 2415.
(36) Anderson, H. L.; Wylie, A. P.; Prout, K. J. Chem. Soc., Perkin Trans.
1 1998, 1607.
(37) LeCours, S. M.; Guan, H.-V.; DiMagno, S. G.; Therien, M. J. J. Am.
Chem. Soc. 1996, 118, 1497.
(38) Arnold, D. P.; Hartnell, R. D. Tetrahedron 2001, 57, 1335.
(39) Arnold, D. P.; Heath, G. A.; James, D. A. New J. Chem. 1998, 22,
1377.
(40) Anderson, H. L. Chem. Commun. 1999, 2323.
(41) Shediac, R.; Gray, M. H. B.; Uyeda, H. T.; Johnson, R. C.; Hupp, J.
T.; Angiolillo, P. J.; Therien, M. J. J. Am. Chem. Soc. 2000, 122,
7017.
(15) Wołowiec, S.; Latos-Graz˘yn´ski, L.; Mazzanti, M.; Marchon, J.-C.
Inorg. Chem. 1997, 36, 5761.
(16) Mazzanti, M.; Marchon, J.-C.; Wojaczyn´ski, J.; Wołowiec, S.; Latos-
Graz˘yn´ski, L.; Shang, M.; Scheidt, W. R. Inorg. Chem. 1998, 37, 2476.
(17) Wołowiec, S.; Latos-Graz˘yn´ski, L.; Toronto, D.; Marchon, J.-C. Inorg.
Chem. 1998, 37, 724.
(18) Simonato, J.-P.; Pe´caut, J.; Le Pape, L.; Oddou, J.-L.; Jeandey, C.;
Shang, M.; Scheidt, W. R.; Wojaczyn´ski, J.; Wołowiec, S.; Latos-
Graz˘yn´ski, L.; Marchon, J.-C. Inorg. Chem. 2000, 39, 3978.
(19) Latos-Graz˘yn´ski, L.; Lisowski, J.; Olmstead, M. M.; Balch, A. L. Inorg.
Chem. 1989, 28, 1183.
(20) Balch, A. L.; Cornman, C. R.; Latos-Graz˘yn´ski, L.; Olmstead, M. M.
J. Am. Chem. Soc. 1990, 112, 7552.
(21) Pawlicki, M.; Latos-Graz˘yn´ski, L. Inorg. Chem. 2002, 41, 5866.
(22) Ohgo, Y.; Neya, S.; Ikeue, T.; Takahashi, M.; Takeda, M.; Funasaki,
N.; Nakamura, M. Inorg. Chem. 2002, 41, 4627.
(23) Rachlewicz, K.; Latos-Graz˘yn´ski, L.; Vogel, E. Inorg. Chem. 2000,
39, 3247.
(24) Rachlewicz, K.; Latos-Graz˘yn´ski, L.; Vogel, E.; Ciunik, Z.;
Jerzykiewicz, L. Inorg. Chem. 2002, 41, 1979.
(42) Burrell, A. K.; Officer, D. L.; Plieger, P. G.; Reid, D. C. W. Chem.
ReV. 2001, 101, 2751.
(43) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 2001, 34, 40.
(44) Harvey, P. D. Recent Advances in Free and Metalated Multi-Porphyrin
Assemblies and Arrays. A Photophysical Perspective. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: New York, 2003; pp 63-250.
(25) Rachlewicz, K.; Wang, S.-L.; Ko, J.-L.; Hung, C.-H.; Latos-Graz˘yn´ski,
L. J. Am. Chem. Soc. 2004, 126, 4420.
(26) Kadish, K. M.; Tabard, A.; Van Caemelbecke, E.; Aukauloo, A. M.;
Richard, P.; Guilard, R. Inorg. Chem. 1998, 37, 6168.
(27) Tomizaki, K.; Lysenko, A. B.; Taniguchi, M.; Lindsey, J. S.
Tetrahedron 2004, 60, 2011.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4523

Berlicka et al.
Chart 1
elements have been considered as specifically efficient in
the transmission of electronic effects along multipart poly-
porphyrinic systems.27,45,46 Appropriately chosen meso sub-
stituents, containing ethynyl, phenylethynyl, and phenyl-
butadiynyl groups, will provide insight into the spin density
delocalization in the ethynyl-fragment-containing framework.
Results and Discussion
Synthesis of Ethynylporphyrins and Their Zinc(II) and
Iron(III) Complexes. The ethynylporphyrins 5-ethynyl-10,-
15,20-tri(p-tolyl)porphyrin [(ETrTP)H2, 1], 5-(phenylethyn-
yl)-10,15,20-tri(p-tolyl)porphyrin [(PETrTP)H2, 2], 5-(phen-
ylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin [(PBTrTP)H2, 3],
5,10,15,20-tetra(phenylethynyl)porphyrin [(TPEP)H2, 4], and
1,4-bis-[10,15,20-tri(p-tolyl)porphyrin-5-yl]-1,3-butadiyne
{[(TrTP)H2]2B, 5 (B-butadiyne)} were synthesized by pro-
cedures previously described in the literature.31,32,36,47,48
(TPEP)H2, 4, was characterized by X-ray crystallography
as a porphyrin dication in the crystal of [(TPEP)H4](CF3-
COO)2‚(CF3COOH)2.73‚(CH2Cl2)0.27. A perspective view of
the dication is shown in Figure 1.
2+
The dication 4-H2 presents a significantly saddle-
distorted macrocylic conformation. The average deviation
of the Câ atoms from the mean plane is 0.574 Å (0.262 Å
for all 24 macrocycle atoms). On each porphyrin face, a
trifluoroacetate (TFA) anion acts as a monodentate ligand
and binds through a carboxyl oxygen to two opposing N-H
protons. Each coordinated anion is associated with the
Figure 1. Molecular structure of [(TPEP)H4](CF3COO)2‚(CF3COOH)2.73
‚
(CH2Cl2)0.27 (with 50% probability ellipsoids). In trace A, the TFA anions,
TFAH molecules, and CH2Cl2 molecule are omitted for clarity. Trace B
shows two molecules of TFAH associated with coordinated TFA anions
on both faces of the porphyrin plane. The unit cell also contains the site
shared by CH2Cl2 and TFAH (0.27 and 0.73 occupancy, respectively).
Dashed lines indicate hydrogen bonds. The coplanarity of the porphyrin
plane and phenylethynyl substituents is visible. The bond lengths in the
ethyne unit are Cmeso-C, 1.419(3)-1.427(3) Å; CtC, 1.197(3)-1.199(3)
Å; and C-Cipso, 1.431(3)-1.437(3) Å.
(45) Piet, J. J.; Taylor, P. N.; Anderson, H. L.; Osuka, A.; Warman, J. M.
J. Am. Chem. Soc. 2000, 122, 1749.
(46) Rubtsov, I. V.; Susumu, K.; Rubtsov, G. I.; Therien, M. J. J. Am.
Chem. Soc. 2003, 125, 2687.
(47) Lin, V. S.-Y.; Therien, M. J. Chem. Eur. J. 1995, 1, 645.
(48) Koshushkov, S.; Haumann, T.; Boese, R.; Burkhardt, K.; Scheib, S.;
Buerle, P.; de Meijere, A. Angew. Chem., Int. Ed. Engl. 1995, 34,
781.
4524 Inorganic Chemistry, Vol. 44, No. 13, 2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
trifluoroacetic acid (TFAH) molecule via the hydrogen bond.
The pyrrole rings are twisted with respect to each other by
2+
23.0(2)°-27.9(2)°. The porphyrin dication 4-H2 presents
a degree of porphyrin distortion similar to that seen for the
octaethylporphyrin dication [(OEP)H4](CF3COO)2‚(CF3-
COOH)2,49 which is in contrast to meso-tetraarylporphyrin
dications showing a similar nonplanar saddle conformation
but with Câ displacements varying in the 0.9-1.2 Å
range.49-52
The angles between the planes of the phenyl rings and
2+
that of the porphyrin for 4-H2 are 4.6(2)°, 9.6(2)°, 12.4-
(2)°, and 16.5(2)°. These values are significantly smaller than
the corresponding dihedral angles measured for the pyridine
zinc complex of 5,10,15,20-tetra(4-butylphenylethynyl)-
porphyrin where the relevant angles are equal to 29.7(3)°
and 59.5(3)° for the two types of aryl rings.36 However, the
nearly coplanar arrangement was previously reported for
metalloporphyrins containing one or two aryl moieties linked
by ethynyl units at meso positions.53,54 In meso-tetraarylpor-
phyrins, the steric repulsion between the pyrrole hydrogen
and the ortho aromatic hydrogens favors torsional angles of
around 71°.55,56 However, the formation of meso-tetraarylpor-
phyrin dications results in a large degree of the in-plane
Figure 2. Electronic spectra of 1-FeCl (pink), 2-FeCl (red), 3-FeCl (blue),
4-FeCl (purple, spectrum for the saturated solution), 5-FeCl (green), and
(TPP)FeIIICl (black) in chloroform.
rotation of meso-aryl groups exemplified by 21° determined
2+ 50
for (TPP)H4
. At present, we assume that the formation
of the meso-tetraphenylethynylporphyrin dication prefers the
nearly coplanar arrangement of the phenyls and the porphyrin
plane. These torsional angles can be also determined by
crystal packing as a barrier to phenyls rotation, which is
expected to be very small compared to that for meso-
tetraarylporphyrins.
Still, the coplanarity of the porphyrin and phenylethynyl
moieties can account for the increased interaction between
the porphyrin and phenylethynyl π systems. This phenom-
enon can explain the enormous bathochromic shifts in the
UV-visible electronic spectrum of (TPEP)H2 with respect
to those of (TPP)H2 and tetra(trimethylsilylethynyl)por-
phyrin.32
Figure 3. Molecular structure of bis-tetrahydrofuran 1,4-bis-[10,15,20-
tri(p-tolyl)porphyrinatozinc(II)-5-yl]-1,3-butadiyne (5-Zn2) (with 50% prob-
ability ellipsoids). Trace B emphasizes the mutual arrangement of two
subunits. The bond lengths in the central butadiyne unit are Cmeso-C, 1.422-
(3) Å; CtC, 1.204(4) Å; and central C-C, 1.373(6) Å.
The insertion of iron into ethynylporphyrins resulted in
the formation of (ETrTP)FeIIICl (1-FeCl), (PETrTP)FeIIICl
(2-FeCl), (PBTrTP)FeIIICl (3-FeCl), (TPEP)FeIIICl (4-FeCl),
and [(TrTP)FeIIICl]2B [5-(FeCl)2]. The electronic spectra of
high-spin iron(III) ethynylporphyrins (Figure 2) are charac-
teristic for high-spin iron(III) tetraphenylporphyrins.57 The
extension of the aromatic system causes bathochromic shifts
of all bands and changes in their relative intensity as
compared to those in the spectrum of (TPP)FeIIICl.
Zinc(II) is readily inserted into 1-5 by a standard
metalation procedure to yield (ETrTP)Zn (1-Zn), (PETrTP)-
Zn (2-Zn), (PBTrTP)Zn (3-Zn), (TPEP)Zn (4-Zn), and
[(TrTP)Zn]2B (5-Zn2). The synthesis of zinc(II) complexes
was prompted by the fact that these complexes have been
applied as suitable diamagnetic standards in the analysis of
1H NMR spectra of the corresponding iron(III) ethynylpor-
phyrins. The IH NMR parameters of zinc(II) ethynylporphy-
rins are given in the Supporting Information.
The bis-tetrahydrofuran 1,4-bis-[10,15,20-tri(p-tolyl)por-
phyrinatozinc(II)-5-yl]-1,3-butadiyne (5-Zn2) complex was
characterized by X-ray crystallography (Figure 3). The
complex contains two [(TrTP)ZnII(THF)] subunits resembling
the zinc(II) 5,10,15-tri(p-metoxyphenyl)porphyrin {[Tr(p-
MeOP)P]ZnII}.58 Actually, the bond lengths and angles of
(49) Senge, M. O.; Forsyth, T. P.; Nguyen, L. T.; Smith, K. M. Angew.
Chem., Int. Ed. Engl. 1994, 33, 2485.
(50) Stone, A.; Fleischer, E. B. J. Am. Chem. Soc. 1968, 90, 2736.
(51) Senge, M. O.; Kalisch, W. W. Z. Naturforsch. B: Chem. Sci. 1999,
54, 943.
(52) Cetinkaya, E.; Johnson, A. W.; Lappert, M. F.; McLaughlin, G. M.;
Muir, K. W. J. Chem. Soc., Dalton Trans. 1974, 1236.
(53) LeCours, S. M.; DiMagno, S. G.; Therien, M. J. J. Am. Chem. Soc.
1996, 118, 11854.
(54) Yeung, M.; Ng, A. C. H.; Drew, M. G. B.; Vorpagel, E.; Breitung, E.
M.; McMahon, R. J.; Ng, D. K. P. J. Org. Chem. 1998, 63, 7143.
(55) Silver, A.; Tulinsky, A. J. Am. Chem. Soc. 1964, 86, 927.
(56) Huuskonen, S. P. J.; Wilson, G. S.; Anderson, H. L. Acta Crystallogr.
C: Cryst. Struct. Commun. 1998, 54, 662.
(57) Wojaczyn´ski, J.; Latos-Graz˘yn´ski, L.; Głowiak, T. Inorg. Chem. 1997,
(58) Wojaczyn´ski, J.; Latos-Graz˘yn´ski, L.; Chmielewski, P. J.; Van Calcar,
P.; Balch, A. L. Inorg. Chem. 1999, 38, 3040.
36, 6299.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4525

Berlicka et al.
Chart 2
the two subunits are within the limits expected for zinc(II)
porphyrins.58 The porphyrin macrocycle of [(TrTP)ZnII-
(THF)] adopts a ruffled conformation. The zinc, which
axially coordinates a THF molecule, is displaced from the
average porphyrin plane by 0.324(1) Å. The butadiyne linker
is practically linear. Actually, the C(5) and C(5′) meso-
carbons are nearly located on the straight line defined by
butadiyne carbon atoms. The porphyrin planes of the subunits
are parallel in the solid state resulting from a crystallographic
inversion center located in the center of the molecule.
However, free rotation around the butadiyne unit is expected
in solution.36
symmetry equivalent to the a-d and A sets). The analysis
carried out for four-coordinate [(TrTP)M]2B (5-M2) holds
for the six-coordinate [(TrTP)Fe(CN)2]2B {5-[Fe(CN)2]2} as
well. For the dimeric [(TrTP)FeIIICl]2B [5-(FeCl)2], the
spectroscopic pattern can be more complicated. The ionic
radius and charge of the high-spin iron(III) impose five-
coordinate square-pyramidal structures on each [(TrTP)FeIII-
Cl] subunit. Accordingly, these metal ions are displaced from
the porphyrin plane. The two subunits of [(TrTP)FeIIICl]2B
[5-(FeCl)2] are not necessarily coplanar. The dimeric mol-
ecule has C2 symmetry with the C2 axis perpendicular to
the C(5)-C(5′) linker. Thus two [(TrTP)FeIIICl] subunits are
equivalent. However, as seen in Chart 2, the pyrrolic
positions 7-H(a) and 3-H(a′), 8-H(b) and 2-H(b′), 12-H(c)
and 18-H(c′), and 13-H(d) and 17-H(d′) are no longer
equivalent, in contrast to [(TrTP)M]2B (5-M2). Additionally,
the symmetry lowering in these five-coordinate complexes
renders the three tolyls substituents on each porphyrin
The distance between the two planes defined by the four
nitrogen atoms of each porphyrinic subunit equals 1.72(2)
Å. Previously, Anderson and co-workers structurally char-
acterized the pyridine zinc(II) meso-butadiyne linked dimer
derived from 5,15-bis(3,5-di-tert-butylphenyl)-10,20-bis(tri-
hexylsilylethynyl)porphyrin.59 This dimer containing a 56-
atom π system is remarkably planar (to (0.391 Å). The
displacement range from the 52-atom plane of 5-Zn2 is
markedly larger (to (0.587 Å). In the two dimers, the bond
lengths of the butadiyne unit are comparable.
1
inequivalent. Such a geometry has been reflected in the H
NMR spectrum of the previously investigated iron(III) 5,5′-
bis(10,15,20-triphenylporphyrin) {[(TrPP)FeIIICl]2} with di-
rect meso-meso linkage of two iron(III) porphyrinic sub-
units.58 In contrast to [(TrPP)FeIIICl]2, where the steric
hindrance of the adjacent pyrrolic fragments hinders rotation
around the meso-meso linkage, fast rotation around the
butadiyne linker is sterically allowed for [(TrTP)FeIIICl]2B
[5-(FeCl)2]. Thus, the number of â-H pyrrole resonances will
be reduced to four. Consequently, only two sets of meso-
(p-tolyl) resonances are predicted. On each meso-tolyl ring,
the two ortho and two meta protons are not equivalent
because the porphyrin plane bears different substituents on
opposite sides and rotation about the meso-carbon-tolyl bond
is restricted. On the other hand, two ortho, two meta, and
two p-methyl resonances are expected when two porphyrin
sides are identical {e.g., the six-coordinate complex [(TrTP)-
Fe(CN)2]2B, 5-[Fe(CN)2]2}.
1
High-Spin Iron(III) Porphyrin H NMR Studies. To
understand the spectral data, the structural characteristics of
metalloporphyrins were considered. The monomeric com-
plexes containing the tri(p-tolyl)porphyrin unit (ethynylpor-
phyrins 1, 2, 3) will have the highest maximal C2V symmetry
when the corresponding metalloporphyrin has identical
ligation on both sides of the porphyrin plane or Cs symmetry
when the ligation on either side is different. In both cases,
four distinct types of pyrrole protons (labeled a-d for 2-MX
in Chart 2) and two types of phenyl groups (labeled A and
B) are present. C4V symmetry is expected in the case of
complexes derived from 4 yielding a single â-H resonance.
For the dimeric porphyrin 5-M2 (X,Y positions not
occupied) with simple planar coordination in each macro-
cycle, the molecule exhibits at least the D2 symmetry. In
Chart 2, this dimer is shown with two subunits in different
planes, as fast rotation around butydiyne linker is expected.
In the 5-M2 dimer, again four distinct types of pyrrole protons
labeled a-d and two types of p-tolyl groups (labeled A and
B) are present (the primed positions, a′-d′ and A′, are
1
Respective H NMR spectra for high-spin iron(III) ethy-
nylporphyrins are presented in Figures 4 and 5. For the sake
of comparison, the spectrum of chloroiron(III) 5,10,15-tri-
phenylporphyrin (TrPP)FeIIICl (6-FeCl) has been included
in Figure 4 (trace A). The spectral parameters are gathered
in Table 1. Resonance assignments, which are given above
selected peaks, were made on the basis of relative intensities
and line widths. The plots of temperature dependence of the
(59) Taylor, P. N.; Huuskonen, J.; Rumbles, G.; Aplin, R. T.; Williams,
E.; Anderson, H. L. Chem. Commun. 1998, 909.
4526 Inorganic Chemistry, Vol. 44, No. 13, 2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
Table 1. Chemical Shifts of High-Spin Iron(III) Ethynylporphyrins
phenyl
meta
tolyl
meta
compound
pyrrole
ortho
para
ortho
methyl
(ETrTP)FeIIICl (1-FeCl)a,b
(PETrTP)FeIIICl (2-FeCl)a
(PBTrTP)FeIIICl (3-FeCl)a
(TPEP)FeIIICl (4-FeCl)a
[(TrTP)FeIIICl]2B (5-FeCl)a
(TrPP)FeIIICl (6-FeCl)c
78.4, 79.4
77.8, 78.6, 80.1
78.0, 79.5
75.7
77.8, 78.5, 79.1
78.5, 81.1, 81.9
-
-
-
5.4, 8.1
5.3, 8.3
8.4
-
8.7
11.4, 11.8, 12.5, 13.0
11.5, 11.9, 12.7, 13.0
11.2, 11.6, 12.3, 12.8
-
11.2, 11.7, 12.4, 12.8
-
5.9, 6.2
6.1, 6.3
5.8, 6.1
-
5.8, 6.2
-
2.2
11.5
9.5
10.7
-
0.8
4.8
4.1
-
5.1, 8.2
4.3
2.7
-
6.4, 6.5
12.1, 12.3, 13.3, 13.5
-
a Measured in chloroform-d at 298 K. b Ethynyl-H, -45.4 ppm. c Measured in chloroform-d at 293 K; meso-H, -72.4 ppm.59
Figure 4. 1H NMR spectra of (A) (TrPP)FeIIICl (6-FeCl) and (B) (ETrTP)-
FeIIICl (1-FeCl) in chloroform-d at 298 K. Resonance assignments: o-Ph,
m-Ph, and p-Ph, ortho-, meta-, and para-phenyl protons, respectively; o-Tol
and m-Tol, ortho- and meta-tolyl protons, respectively; pyrr, pyrrole protons;
CH3, methyl protons of the tolyl; meso, meso-proton; -CCH, ethynyl proton;
s, solvent. The relative intensity of the 70-90 ppm region has been increased
by a factor of 3.
chemical shifts, which are typical for the high-spin iron(III)
electronic state of iron porphyrins, are shown in the Sup-
porting Information. Direct comparisons to iron(III) tetra-
phenylporphyrin derivatives facilitated the assignment.1,8,57,58,60
Figure 5. 1H NMR spectra of (A) (PETrTP)FeIIICl (2-FeCl), (B)
(PBTrTP)FeIIICl (3-FeCl), (C) (TPEP)FeIIICl (4-FeCl, generated by titration
of the µ-oxo dimer 4-Fe2O by chloroform-d saturated with HCl), and (D)
[(TrTP)FeIIICl]2B [5-(FeCl)2] in chloroform-d at 298 K. Resonance assign-
ments: µ-oxo, protons of µ-oxo dimer 4-Fe2O; *, impurities; all others
follow those of Figure 4. The relative intensity of the 70-90 ppm region
in all traces has been increased by a factor of 3.
Thus, the eight equivalent â-pyrrole positions of (TPEP)-
FeIIICl (4-FeCl) produce a singlet at 75.7 ppm. The four
unequivalent pyrrole positions of 1-FeCl, 2-FeCl, and 3-FeCl
are expected to generate four downfield-shifted pyrrole
resonances for well-resolved spectra. Severe overlapping of
relatively broad resonances reduces this number to three or
two, accompanied by the appropriate alteration of intensities.
The characteristic meso-substituent dependent patterns, are
demonstrated in Figures 4 and 5. These pyrrolic resonances
are spread near the position typical for high-spin iron(III)
tetraphenylporphyrins, i.e., ca. 80 ppm (298 K), resembling
spectra of others meso-substituted high-spin iron(III) 5-X-
triarylporphyrin complexes (X ) H, NO2, Br, OAc, OH).8,58
The meso-(p-tolyl) resonances are located in the region that
is typical for high-spin iron(III) porphyrins. The multiplicity
of the respective resonances is directly related to the
symmetry of molecules as discussed in detail above. Thus,
for 1-FeCl, 2-FeCl, and 3-FeCl, the characteristic well-
resolved pattern of meta-(p-tolyl) resonances was detected.
In each case, the pattern consists of two doublets with a 2:1
intensity ratio, readily assigned to A and B meso positions.
The presence of two lines for one meso substituent confirms
the slow p-tolyl rotation around the Cmeso-Cipso bond. The
1H NMR spectrum of dimeric [(TrTP)FeIIICl]2B [5-(FeCl)2]
matches the spectra of the above-described monomeric
species as far as the pyrrolic and meta-(p-tolyl) resonances
are concerned. This observation is consistent with the
anticipated free rotation around the butadiyne unit.
Considering the fact that the iron(III) tri(p-tolyl)porphyrin
fragment is common for all compounds under investigation,
the identification of other paramagnetic shifted resonances
is straightforward by default. This spectroscopic task is of
(60) Wojaczyn´ski, J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1995, 34, 1044.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4527

Berlicka et al.
primary importance, as the delocalization of the spin density
along the ethynyl or butadiynyl fragment is the main interest
of the presented project. The respective assignments are given
in Figures 4 and 5 and in Table 1. As seen in Figure 4 (trace
B), this is the single resonance in the far upfield region that
can be assigned to the ethynyl proton of 1-FeCl. The position
resembles that of the meso-H resonance of 6-FeCl (Figure
4, trace A). Significantly, the difference in line widths is
remarkable despite the identical axial ligation. In contrast,
the other resonances (â-H and meta-H of meso-aryls) of
1-FeCl and 6-FeCl reveal similar line widths. Paramagneti-
cally induced broadening can be of both dipolar and scalar
origin, but the scalar contribution is typically small. The
dipolar contribution to the line width broadening is presumed
to be proportional to r-6, where r is the distance from the
paramagnetic center to the proton in question.61,62 Thus, the
marked difference in line widths seen for meso-H of 6-FeCl
and ethynyl-H of 1-FeCl clearly reflects the distance from
the paramagnetic center and is consistent with the proposed
assignment. Analogously, relatively narrow resonances were
detected for the phenyls capping ethynyl or butadiynyl
moieties of 2-FeCl, 3-FeCl, and 4-FeCl as compared to
(TPP)FeIIICl where meso-phenyls are directly linked to the
meso-carbon.
Figure 6. Plot of chemical shifts versus 1/T for the cyclic [(TrTP)FeIII-
OFeIII(TrTP)-B]2 [52-(FeOFe)2] complex with two µ-oxo bridges linking
subunits of two iron diporphyrins connected by the butadiyne linker. The
solid lines are for illustrative purposes only. Inset: Pyrrolic fragment of
1
the H NMR spectrum (298 K, CDCl3).
2-Fe2O, 3-Fe2O, and 6-Fe2O. Specifically, the well-resolved
set of four pyrrole resonances at 13.0, 13.3, 13.7, and 15.0
ppm (298 K) that reflects anti-Curie behavior was identified
(Figure 6).
The feasible formation of the high-spin (TrTP)FeIIIOH
moiety has not been documented in the conditions of our
experiments. The possible hydroxy species were expected
to be discerned by a set of resonances resembling those of
the precursor [(TrTP)FeIIICl]2B [5-(FeCl)2]. The analytically
significant pyrrole resonances of [(TrTP)FeIII(OH)]2B
[5-(FeOH)2] or [(TrTP)FeIIICl]B[(TrTP)FeIIIOH] [5-(FeCl)-
(FeOH)] would be broader than the resonances of 5-(FeCl)2,
as is characteristic for the hydroxy group coordination to
iron(III) porphyrins.65,66 Scheme 1 presents one feasible route
resulting in the formation of a variety species containing
µ-oxo diiron units. The gradual replacement of chloride by
hydroxide initially produces [(TrTP)FeIIICl]B[(TrTP)FeIIIOH]
[5-(FeCl)(FeOH)], followed by [(TrTP)FeIII(OH)]2B [5-
(FeOH)2]. Subsequent condensation (dehydratation) generates
the µ-oxo-bridged diiron(III) fragment -(TrTP)FeIIIOFeIII-
(TrTP)-, which can be built into the more elaborate
molecular structures as shown in Scheme 1. For instance, in
(HOFe)-5-(FeOFe)-5-(FeOH), the terminal subunits remain
high-spin five-coordinate with the OH group in the axial
µ-Oxo-Bridged Diiron Complexes. Treatment of the
high-spin iron(III) ethynylporphyrins 1-FeCl, 2-FeCl, 3-FeCl,
and 4-FeCl with K2CO3 in water or chromatography on a
basic alumina column resulted in formation of the µ-oxo-
bridgeddiironcomplexes[(ETrTP)FeIII]2O(1-Fe2O),[(PETrTP)-
FeIII]2O (2-Fe2O), [(PBTrTP)FeIII]2O (3-Fe2O), and [(TPEP)-
FeIII]2O (4-Fe2O). The 1H NMR patterns of 1-Fe2O, 2-Fe2O,
and 3-Fe2O, which spread in the 12-16 ppm range, are
reproduced by a convolution of four pyrrole resonances and
reflect the symmetry of the iron(III) tri(p-tolyl)porphyrin
subunit. As expected, a single pyrrole line was detected for
symmetrical 4-Fe2O. These â-H resonances demonstrate the
anti-Curie behavior of the isotropic shifts, i.e., an increase
of the pyrrole resonance shifts on warming, as expected for
µ-oxo-bridged diiron porphyrins.63 The spectral properties
resemble those of asymmetric tetraphenylporphyrin deriva-
tives including µ-oxo-bridged diiron complexes of N-
methylporphyrin, 21-oxaporphyrin, and recently character-
ized µ-oxo diiron(III) 5,10,15-triphenylporphyrin (6-Fe2O)
[δ, 13.2 (4H), 13.4 (4H), 13.6 (8H), meso-H (2H) 6.3 ppm,
293 K].21,58,64 The ethynyl-H resonance of 1-Fe2O is expected
in the region of intense solvent signals (1-2 ppm).
1
position, which has been excluded on the basis of the H
NMR evidence. The flexibility of [(TrTP)FeIIICl]2B [5-(FeCl)2]
allows for the formation of the cyclic [(TrTP)FeIIIOFeIII-
(TrTP)-B]2 [5-(FeOFe)2] complex with two µ-oxo bridges
linking subunits of two diiron diporphyrins connected by the
butadiyne linker. The structure of 5-(FeOFe)2 was unambigu-
ously confirmed by mass spectrometry (m/z ) 2662.0; calcd
for C172H116N16O2Fe4 2662.3).
1
The H NMR studies indicate that chromatography of
[(TrTP)FeIIICl]2B [5-(FeCl)2] on a basic alumina column
1
yields a single product with the H NMR spectroscopic
features of the µ-oxo-bridged diiron(III) fragment -(TrTP)-
FeIIIOFeIII(TrTP)- characterized above in detail for 1-Fe2O,
Previoulsy, Anderson and co-workers demonstrated that
the zinc(II) complexes of the conjugated porphyrin oligomers,
(61) La Mar, G. N.; Walker, F. A. NMR of Paramagnetic Porphyrins. In
The Porphyrins; Dolphin, D., Ed.; Academic Press: New York, 1979;
pp 57-161.
(62) Bertini, I.; Luchinat, C. Coord. Chem. ReV. 1996, 150, 1.
(63) Boersma, A. D.; Phillippi, M. A.; Goff, H. M. J. Magn. Reson. 1984,
57, 197.
(65) Cheng, R.-J.; Latos-Graz˘yn´ski, L.; Balch, A. L. Inorg. Chem. 1982,
21, 2412.
(64) Wysłouch, A.; Latos-Graz˘yn´ski, L.; Grzeszczuk, M.; Drabent, K.;
(66) Balch, A. L.; Chan, Y.-W.; Cheng, R.-J.; La Mar, G. N.; Latos-
Graz˘yn´ski, L.; Renner, M. W. J. Am. Chem. Soc. 1984, 106, 7779.
Bartczak, T. J. Chem. Soc., Chem. Commun. 1988, 1377.
4528 Inorganic Chemistry, Vol. 44, No. 13, 2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
Scheme 1
from the dimer to the hexamer, form stable ladder complexes
with 1,4-diazabicyclo[2.2.2]octane and 4,4′-bipyridyl.67,68 The
geometry of 5-(FeOFe)2 resembles that of the 2:2 ladder
dimer with the 1,4-diazabicyclo[2.2.2] coordinating linker.68
Spectral Characterization of Low-Spin Iron(III) Eth-
ynylporphyrins. Titration of 1-FeCl, 2-FeCl, 3-FeCl, 4-FeCl,
and 5-(FeCl)2 dissolved in chloroform-d with an excess of
potassium cyanide in methanol-d4 results in their conversion
to the six-coordinate low-spin complexes [(ETrTP)FeIII(CN)2]
[1-Fe(CN)2], [(PETrTP)FeIII(CN)2] [2-Fe(CN)2], [(PBTrTP)-
FeIII(CN)2] [3-Fe(CN)2], [(TPEP)FeIII(CN)2] [4-Fe(CN)2], and
{[(TrTP)FeIII(CN)2]2B}2 {5-[Fe(CN)2]2}, respectively. Nearly
identical spectra were generated by dissolution of the
respective iron(III) ethynylporphyrin in methanol-d4 saturated
with potassium cyanide. The assignment of the ethynyl-H
resonance of 1-Fe(CN)2 was possible only in the first stage
of titration of 1-FeCl in chloroform-d with KCN in methanol-
d4. In this experiment, selective deuteration at this particular
position took place with methanol-d4 as the source of
deuterium. The deuteration was confirmed by an independent
experiment. Specifically, after titration in the presence of
methanol-d4, when the deuteration had been completed, the
sample was dried and redissolved in chloroform-d in the
presence of (TBA)CN (tetrabutylammonium cyanide). This
sample yielded a spectrum resembling that obtained directly
by titration of 1-FeCl with (TBA)CN but with the single
ethynyl resonance missing.
Figure 7. 1H NMR spectra of (A) [(ETrTP)FeIII(CN)2]- [1-Fe(CN)2], (B)
[(PETrTP)FeIII(CN)2]- [2-Fe(CN)2], (C) [(PBTrTP)FeIII(CN)2]- [3-Fe-
(CN)2], (D) [(TPEP)FeIII(CN)2]- [4-Fe(CN)2], and (E) {[(TrTP)FeIII-
(CN)2l]2B}2- {5-[Fe(CN)2]2} in chloroform-d/methanol-d4 solution at 298
K. Resonance assignments follow those of Figures 4 and 5; squares and
circles denote the scalar coupled pairs of pyrrole protons. The relative
intensity of the region between -6 and -16 ppm in all traces has been
increased by a factor of 2.
of bis-cyanide iron(III) ethynylporphyrins to the presence
of methanol follows the general trend. Usually, low-spin iron-
(III) porphyrins, formed by the coordination of two cyanide
ligands, produce very narrow paramagnetically shifted
resonances because of their optimal relaxation properties.5
An excess of potassium cyanide added to 4-FeCl led to side
reactions, as cyanide acts generally as a reducing agent
toward iron(III) porphyrins.7,71 The one-electron reduction
introduces [(TPEP)FeII(CN)2], which remains in fast ex-
change with the maternal [(TPEP)FeIII(CN)2]. The fast
electron exchange causes significant broadening of the
pyrrole resonances and their slight shift toward the downfield
direction.
Previously, complex equilibria were detected in the course
of titration of covalently linked diiron diporphyrins (por-
phyrin subunits connected by diether aliphatic moieties) with
cyanide.72 Analogously, the stepwise addition of cyanide to
a chloroform solution of 5-(FeCl)2 revealed a multiplicity
of species. Here, the final titration product, {[(TrTP)FeIII-
(CN)2]2B}2- {5-[Fe(CN)2]2}, is the only species analyzed.
The representative 1H NMR spectra of 1-Fe(CN)2, 2-Fe(CN)2,
3-Fe(CN)2, 4-Fe(CN)2, and 5-[Fe(CN)2]2 are shown in Figure
Titration of iron(III) ethynylporphyrins with (TBA)CN in
chloroform-d produced the low-spin bis-cyanide species,
although with â-resonances shifted upfield in comparison
with the spectra collected in the presence of methanol-d4. It
has already been demonstrated that hydrogen bonding to the
cyanide ligand causes a general decrease of [(TPP)FeIII(CN)2]
isotropic shifts.69,70 Thus, the sensitivity of the isotropic shifts
(67) Anderson, H. L. Inorg. Chem. 1994, 33, 972.
(68) Taylor, P. N.; Anderson, H. L. J. Am. Chem. Soc. 1999, 121, 11538.
(69) La Mar, G. N.; Del Gaudio, J.; Frye, J. S. Biochim. Biophys. Acta
1977, 498, 422.
(70) Ikezaki, A.; Nakamura, M. Inorg. Chem. 2002, 41, 2761.
(71) La Mar, G. N.; Del Gaudio, J. AdV. Chem. Ser. 1977, 162, 207.
(72) Wołowiec, S.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1994, 33, 3576.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4529

Berlicka et al.
Table 2. Chemical Shifts of Low-Spin Iron(III) Ethynylporphyrins
phenyl
meta
tolyl
compound
pyrrole
ortho
para
ortho
meta
methyl
[(ETrTP)FeIII(CN)2]- [1-Fe(CN)2]a,b
[(PETrTP)FeIII(CN)2]- [2-Fe(CN)2]a
[(PBTrTP)FeIII(CN)2]- [3-Fe(CN)2]a
[(TPEP)FeIII(CN)2]- [4-Fe(CN)2]a
{[(TrTP)FeIII(CN)2]2B}2- [5-[Fe(CN)2]2]a
[(TrTP)FeIII(CN)2]- [6-Fe(CN)2]c
-9.3, -11.1, -11.5, -12.3
-8.5, -10.3, -10.7, -11.4
-9.4, -11.9, -12.2, -13.1
-14.7
-9.0, -11.7, -11.9, -12.5
-9.5, -9.7, -10.5, -12.3
-
-
-
4.9, 5.6
5.0, 5.6
4.8, 5.6
-
4.9, 5.7
-
7.0, 7.3
7.1, 7.5
6.8, 7.2
-
7.0, 7.3
-
2.5, 2,7
2.6, 2.8
2.3, 2.5
-
2.5, 2.6
-
5.4
7.7
5.5
6.5
5.8
-
5.1, 6.1
7.4
7.1
-
7.3, 7.8
6.6
6.2
-
6.4, 6.7
a Obtained by titration of high-spin iron(III) complexes in chloroform-d with KCN in methanol-d4 at 298 K. b Ethynyl-H, -6.3 ppm. c Measured in
methanol-d4 at 293 K; meso-H, -6.9 ppm.59
7. The chemical shift values are collected in Table 2. The
characteristic sets of four pyrrole resonances of 1-Fe(CN)2,
2-Fe(CN)2, 3-Fe(CN)2, and 5-[Fe(CN)2]2, located in the range
between -8 and -13 ppm (298 K), are of importance in
describing the ground state of the electronic structure. These
pyrrole resonances are accompanied by two sets of ortho
and p-methyl resonances assigned to meso-(p-tolyls) that
reveal upfield isotropic shifts and corresponding sets of meta
resonances with opposite, i.e., downfield, isotropic shifts. In
our case, the primary assignment could be made on the basis
of the resonance positions, their intensities, and their multiplet
structure due to scalar coupling. A two-dimensional COSY
experiment was effective in connecting the pyrrole proton
resonances in low-spin iron(III) complexes of ethynylpor-
phyrins. We could easily separate the p-tolyl proton signals
into two subsets, each assigned to individual meso-(p-tolyls).
Significantly, the characteristic coupling of three phenyl
resonances in 2-Fe(CN)2, 3-Fe(CN)2, and 4-Fe(CN)2 allowed
their direct identification.
relationship between the electron-donating/-withdrawing
properties of the 5-substituents and the H NMR spectral
1
pattern.58 Actually, the analogous effects of the meso
substituent on the geometric and electronic structures of high-
spin and low-spin iron(III) meso-substituted octaethylpor-
phyrins {[(5-X-OEP)FeIII], X ) Ph, n-butyl, Cl, CN, HCO,
NO2} were explored as well.74 To trace the extent of
communication via the ethyne or butydiyne fragment, the
isotropic shifts of the resonances of the capping fragments,
i.e., -H or phenyl, were analyzed in detail in the series -H,
-Ph, -CC-H, -CC-Ph, -CC-CC-Ph, -(CC-CC-
TrTP)FeIII. Finally, the communication between two iron-
(III) porphyrinic fragments linked via the butadiyne moiety
of 5-Fe2 was explored.
1
First, we used H NMR spectroscopy to analyze the
influence of meso substitution on the (TrTP)FeIII moiety. A
comparison of the isotropic shifts leads to the general
conclusion that the â-H patterns are quite similar for each
considered set of pairs: (TrPP)FeIIICl and (5-X-TrTP)FeIII-
Cl, [(TrPP)FeIII(CN)2] and [(5-X-TrTP)FeIII(CN)]2, [(TrPP)-
Titration with the 1-methylimidazole ligand produced
spectra that demonstrate the typical shifts of low-spin iron-
(III) porphyrins with the (dxy)2(dxzdyz)3 ground electronic
state.1
+
FeIII(1-MeIm)2]+ and [(5-X-TrTP)FeIII(1-MeIm)]2 (X )
ethynyl, phenylethynyl, phenylbutadiynyl). Thus, monoeth-
ynyl substitution barely affects the ground electronic state
of the (TrTP)FeIII moiety.
Spin Density Transfer Along Ethyne or Butadiyne
Linkers. The electronic structure of meso-ethynyl(s) allows
extensive conjugation with the porphyrinic macrocycle
readily accounting for the general features of ethynylpor-
phyrins. Geometry optimizations and electronic structure
calculations using density functional theory (DFT) have been
reported for porphyrins with meso-ethynyl substituents.73 The
calculated electronic structures clearly show that the ethynyl
group contributes to the π-electron conjugation along the
porphyrin ring for the HOMO and LUMO and significantly
reduces the HOMO-LUMO gap, consistent with experi-
mental results.73 The ZINDO calculation carried out for
copper(II) 5,15-bis(arylethynyl)-10,20-diphenylporphyrins
demonstrated that the frontier molecular orbitals extend on
the arylethynyl moiety.72
In this context, the introduction of the ethynyl group raises
the problem of the impact of such a modification on the
electronic properties of the resulting iron(III) porphyrins to
be followed by 1H NMR spectroscopy. Evidently, the
investigated compounds complete the previously investigated
iron(III) 5-X-triarylporphyrin series (X ) H, Br, OCH3, OH,
NO2, [(TrPP)FeIII]) characterized in order to elucidate the
In light of the current interest in applications of porphyrinic
arrays,75 the ethynyl fragment plays a crucial structural role,
allowing multiporphyrin covalently linked structures, which
act efficiently in energy transfer or as elements in molecular
photonic devices,27 to be built. Apart from their architectural
function, the linkers containing ethynyl make available a
channel for electronic communication between the porphy-
rins. The electronic coupling between the porphyrin core and
its substituents is optimized by the cylindrical symmetric
ethynyl linker. As steric factors do not preclude it, a coplanar
arrangement of the involved aromatic ring systems along the
molecular axis of the highest conjugation is expected. For
instance, a highly extended system is effectively created in
5-phenylethynyl-10,15,20-tri(p-tolyl)porphyrin (2), leading
to the expectation that the phenylethynyl unit and the
porphyrin macrocycle will communicate electronically.27,75,76
Significantly, when aryl groups are directly attached to the
meso-carbon, the steric hindrance favors torsional angles of
(74) Kalish, H.; Camp, J. E.; Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Olmstead,
M. M.; Balch, A. L. Inorg. Chem. 2002, 41, 989.
(75) Holten, D.; Bocian, D. F.; Lindsey, J. S. Acc. Chem. Res. 2002, 35,
57.
(76) LeCours, S. M.; Philips, C. M.; de Paula, J. C.; Therien, M. J. J. Am.
Chem. Soc. 1997, 119, 12578.
(73) Wang, Z. Q.; Day, P. N.; Pachter, R. J. Chem. Phys. 1998, 108, 2504.
4530 Inorganic Chemistry, Vol. 44, No. 13, 2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
around 71°, which decreases the conjugation between the
meso-aryls of (TPP)FeIIICl.61,78,79 In terms of the present
considerations, chloroiron(III) 5-(phenylbutadiynyl)-10,15,-
20-tri(p-tolyl)porphyrin (3-FeCl) reveals the effect of an
elongation of the conducting rod by addition of one more
ethynyl moiety. The comparison of the chemical shifts in
the Table 1 leads to the conclusion that spin delocalization
via the meso-butadiynyl to the capping phenyl is still
operating but the effect is clearly diminished as compared
to that of the phenylethynyl of 2-FeCl. Significantly, the sign
alternation around the phenyl moiety of 3-FeCl is still
detectable.
As a final point, the communication between two high-
spin iron(III) porphyrinic fragments linked via the butadiyne
moiety can be addressed. The similarity of the spectrum of
the diiron complex 5-(FeCl)2 to those containing the analo-
gous (TrTP)FeIIICl subunit allowed us to conclude that the
spin density transfer is relatively small and comparable to
that via the identical linker seen for capping phenyl of
3-FeCl.
Spin delocalization along the ethynyl substituents was
observed for the low-spin complexes. Characteristic features
of the spin delocalization for this particular spin state have
to be considered. Thus, low-spin Fe(III) complexes of 4-fold-
symmetric porphyrins such as (TPP)H2 and (OEP)H2 can
exist in two different electronic states: (dxy)2(dxz,dyz)3 and
the less common (dxz,dyz)4(dxy)1.1 However, an increasing
number of examples of the less common, (dxz,dyz)4(dxy)1 state
have come to light recently.1,14,17,70,80,81 For the lower-
symmetry complexes [(5-R-OEP)FeIII(CN)2]- where one
meso position is unique, the situation is more complex, and
the ground state of [(5-R-OEP)FeIII(CN)2] combines the
features of both ground states with the composition for any
one complex controlled by the nature of the meso-R
substituent.74
porphyrin and aryl systems.31
The isotropic shifts of the resonances of the capping
fragments, i.e., -H and phenyl, were analyzed in detail for
the high-spin iron(III) ethynylporphyrins (ETrTP)FeIIICl (1-
FeCl), (PETrTP)FeIIICl (2-FeCl), (PBTrTP)FeIIICl, (3-FeCl),
and (TrPP)FeIIICl (6-FeCl) and the low-spin iron(III) ethy-
nylporphyrins [(ETrTP)FeIII(CN)2] [1-Fe(CN)2], [(PETrTP)-
FeIII(CN)2][2-Fe(CN)2], [(PBTrTP)FeIII(CN)2] [3-Fe(CN)2],
and [(TrPP)FeIII(CN)2] [6-Fe(CN)2]. The meso-aryl reso-
nances of the analyzed species are included in the comparison
as well, as they represent the extent of delocalization into
aryls groups directly linked to the meso-carbon, allowed
because the aryl and porphyrinic moieties are not orthogonal.
The typical spin delocalization pathways for high-spin
iron(III) porphyrins produce resonances for the â-pyrrole
[(TPP)FeIIIX] or R-CH2 [(OEP)FeIIICl] protons that are
strongly shifted downfield. This downfield shift is a result
of the σ contact contribution due to delocalization through
the σ framework by way of the σ donation to the half-
2
2
occupied dx -y iron(III) orbital. Additionally, π delocalization
places a considerable amount of positive spin density at the
meso positions. The mechanism has been identified as iron-
to-porphyrin π back-bonding and involves the empty 4e(π*)
orbitals of the porphyrin with a large contribution from the
2pz meso-carbon atomic orbitals.1 We have noticed previously
that the contact shift of high-spin iron(III) tetraphenylpor-
phyrins might result from simultaneous delocalization in the
σ orbitals as well as in both filled 3e(π) and vacant 4e(π*)
molecular orbitals.7 Recently, Cheng and co-workers con-
2
sidered that an unpaired electron in the dz orbital of the metal
can interact with the a2u-type π orbital of the macrocycle to
cause significant π-spin delocalization to meso-carbons and
that this is the major contribution to the large negative
chemical shifts of the meso-H of chloroiron(III) octaeth-
ylporphyrin and other porphyrins.77 The π-spin density
localized at meso-carbons produces the sign alternation of
the contact shifts measured for the meso-phenyl resonances
in (TPP)FeIIIX and (5-X-TPP)FeIIIX.1,7,58 It is reflected by
the large upfield shift of the meso-protons of (OEP)FeIIICl
and (5-X-OEP)FeIIICl.1,74 Consequently, the high-spin five-
coordinate iron(III) porphyrins are characterized by a rela-
tively large positive spin density at the meso-carbon, as
illustrated here by the resulting upfield localization of the
meso-H of (TrPP)FeIIICl, -72.4 ppm (293 K). The positive
spin density localized at the meso-carbon can be readily
delocalized along the ethynyl or butadiyne fragment of
appropriate iron(III) ethynylporphyrins. The efficiency of the
spin transfer is remarkable, as illustrated by the chemical
shifts of Cmeso-H and -CC-H determined for 1-FeCl and
6-FeCl (Figure 4, Table 1). Substitution of the ethynyl
hydrogen -CC-H by phenyl -CC-C6H5 affords a spec-
troscopic pattern consistent with the π-spin density distribu-
tion around the introduced phenyl ring. Significantly, the
contact shift values are comparable to those determined for
The upfield meso-proton shift seen for iron porphyrins with
the (dxz,dyz)4(dxy)1 ground state arises from the presence of
spin in the a2u-like porphyrin orbital, which has principal
contributions at the meso positions and little or no contribu-
tion at the pyrrole positions.1,82,83 Complexes with the
(dxz,dyz)4(dxy)1 electronic state that involve (OEP)2- as the
ligand are rare, but [(OEP)FeIII(t-BuNC)2]+ is one example
that is reported to have a nearly pure (dxz,dyz)4(dxy)1 electronic
1
ground state.84 The H NMR spectrum of [(OEP)FeIII(t-
BuNC)2]+ shows that the meso-protons are shifted relatively
far upfield (δ ) -37 ppm at 303 K).84 Significantly, the
positive π spin density is expected for low-spin iron(III)
(78) La Mar, G. N.; Walker, F. A. J. Am. Chem. Soc. 1973, 95, 6950.
(79) Behere, D. V.; Birdy, R.; Mitra, S. Inorg. Chem. 1982, 21, 386.
(80) Simmoneaux, G.; Bondon, A. Isocyanides and Phosphines as Axial
Ligands in Heme Proteins and Iron Porphyrin Models. In The
Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: San Diego, CA, 2000; pp 299-322.
(81) Ikeue, T.; Ohgo, Y.; Saitoh, T.; Yamaguchi, T.; Nakamura, M. Inorg.
Chem. 2001, 40, 3423.
(82) Walker, F. A.; Nasri, H.; TurowskaTyrk, I.; Mohanrao, K.; Watson,
C. T.; Shokhirev, N. V.; Debrunner, P. G.; Scheidt, W. R. J. Am.
Chem. Soc. 1996, 118, 12109.
(83) Ikeue, T.; Ohgo, Y.; Saitoh, T.; Nakamura, M.; Fujii, H.; Yokoyama,
M. J. Am. Chem. Soc. 2000, 122, 4068.
(77) Cheng, R.-J.; Chen, P.-Y.; Lovell, T.; Liu, T.; Noodleman, L.; Case,
(84) Guillemot, M.; Simonneaux, G. J. Chem. Soc., Chem. Commun. 1995,
2093.
D. A. J. Am. Chem. Soc. 2003, 125, 6774.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4531

Berlicka et al.
2+
porphyrins where the (dxz,dyz)4(dxy)1 electronic state contribute
to the electronic structure, which is the case for the
bis-cyanide complexes 1-Fe(CN)2, 2-Fe(CN)2, 3-Fe(CN)2,
5-[Fe(CN)2]2, and 6-Fe(CN)2 formed in methanol solution.
The efficiency of the spin transfer is remarkable, as illustrated
by the relevant isotropic shifts for 1-Fe(CN)2 (-CC-H,
-10.4 ppm) and 6-Fe(CN)2 (Cmeso-H, -17.1 ppm). Sig-
nificantly, the butadiynyl linker of 3-Fe(CN)2 transmits a
sufficient amount of spin density for a measurable effect to
be detected at the capping phenyl moiety.
The differences in values of the induced contact shifts can
be readily explained. Specifically, different amounts of
positive π spin density are originally located at the meso
positions of high-spin and low-spin complexes because of
the obvious differences in the nature of the ground electronic
states.
In regard to the delocalization of the spin density at the
phenylethynyl fragment, it is illustrative to consider the case
where the phenylethynyl moiety is directly coordinated to
high- or low-spin iron(III) porphyrins: (TPP)FeIII(CCPh) (o-
H, -83.9; m-H, 48.9; p-H, -77.8), (THF)(TPP)FeIII(CCPh)
(o-H, -15.6; m-H, 31.8; p-H, -19.4), (py)(TPP)FeIII(CCPh)
(o-H, -31.9; m-H, 32.9; p-H, -13.8) (chemical shift values
at 203 K given in ppm in parentheses).85 The patterns of
resonances for the axial aryl protons are similar for high-
spin and low spin species, as with the ortho- and para-phenyl
resonances shifted upfield and meta-phenyl resonances
shifted downfield. This pattern of shifts reflects the presence
of the unpaired π spin density on the aryl groups in both
cases provided by either low-spin or high-spin iron(III). The
coordination is definitely the most efficient in providing the
considerable amount spin density to the phenylethynyl
fragment. Accordingly, an effect seemingly of the same
nature is more pronounced for (TPP)FeIII(CCPh) than for
(TrTP-CCPh)FeIIICl (2-FeCl). In light of these studies, the
spin density transfer documented here for the ethynyl and
butadiynyl linkers is expected to be operating in the transfer
of spin density by higher conjugated polyynes with end
groups containing paramagnetic metals.86
Table 3. Crystal Data for [(TPEP)H4
]
(CF3COO)2‚(CF3COOH)2.73‚(CH2Cl2)0.27 and [(TrTP)Zn(THF)]2B with
Refinement Details
2+
[(TPEP)H4
]
(CF3COO)2‚(CF3COOH)2.73
‚
(CH2Cl2)0.27
[(TrTP)Zn(THF)]2B
emp formula
fw
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C
61.73H35.27N4O9.46F14.20Cl0.54
C94H74N8O2Zn2
1478.35
monoclinic
P21/n
15.092(3)
13.529(3)
18.244(3)
90
104.54(3)
90
3605.7(12)
100(2)
1273.27
triclinic
P1h
10.454(2)
14.450(4)
20.164(4)
95.81(3)
97.36(3)
110.75(3)
2789.4(11)
100(2)
T, K
Z
D
2
2
calcd, g‚cm-3
1.516
1.362
0.71073
0.725
0.0575
0.1539
radiation λ, Å
µ, mm-1
R1a
0.71073
0.159
0.0577
0.1685
wR2a
2
2
2
a R1 ) ∑||Fo - Fc||/∑|Fo|, wR2 ) [∑[w(Fo - Fc )2/∑[w(Fo )2]]1/2
.
described above. Conversion into the iron(III) complexes proceeded
quantitatively.
X-ray Data Collection and Refinement. Crystals of [(TPEP)-
H42+](CF3COO)2(CF3COOH)2.73(CH2Cl2)0.27 were prepared by dif-
fusion of methanol into a dichloromethane solution with a trace
amount of TFAH contained in a thin tube. Crystals of [(TrTP)Zn-
(THF)]2B were obtained by diffusion of THF into a dichloromethane
solution of 5-Zn2. Crystal data for both compounds are given in
Table 3, together with refinement details. The crystals were mounted
on glass fibers and then flash-frozen to 100 K (Oxford Cryosystem-
Cryostream Cooler). Preliminary examination and intensity data
collections were carried out on an Oxford Diffraction KM4CCD
κ-axis diffractometer with graphite-monochromated Mo KR radia-
tion. The data were corrected for Lorentz and polarization effects.
For [(TrTP)Zn(THF)]2B crystals, an analytical absorption correction
was applied.87 Data reduction and analysis were carried out with
the Oxford Diffraction (Wrocław) programs. The structures were
solved by direct methods (program SHELXS97)88 and refined by
the full-matrix least-squares method on all F2 data using the
SHELXL97 programs.89
In the cell unit of [(TPEP)H42+](CF3COO)2(CF3COOH)2.73‚(CH2-
Cl2)0.27, the dichloromethane and TFAH molecule share one position
with occupancies of 0.27 and 0.73, respectively. Additionally, one
oxygen atom in the TFA anion and one in the TFAH molecule are
disordered and occupy two positions (0.9 and 0.1 occupancy,
respectively).
Experimental Section
Materials. 5-Ethynyl-10,15,20-tri(p-tolyl)porphyrin [(ETrTP)-
H2, 1], 5-(phenylethynyl)-10,15,20-tri(p-tolyl)porphyrin [(PETrTP)-
H2, 2], 5-(phenylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin [(PBTrTP)-
H2, 3], 5,10,15,20-tetra(phenylethynyl)porphyrin [(TPEP)H2, 4], 1,4-
bis-[10,15,20-tri(p-tolyl)porphyrin-5-yl]-1,3-butadiyne {[(TrTP)H2]2B,
5} were synthesized using known procedures.31,32,36,47,48
High-Spin Iron(III) Ethynylporphyrins. A solution of 500 mg
of iron(II) chloride tetrahydrate (2.5 mmol) in 10 mL of methanol
was added in three portions over the course of 1 h (at 20-min
intervals) to a refluxing solution of the appropriate ethynylporphyrin
(0.025 mmol of 1, 2, 3, or 5) dissolved in 20 mL of chloroform.
After the solvent had been removed under reduced pressure, the
solid residue was extracted with dichloromethane and filtered off.
In the case of 4-FeCl, 4 and a metal source were refluxed in pyridine
solution for 1 h, and workup was performed using the procedure
The center of [(TrTP)Zn(THF)]2B is located at a crystallographic
inversion center. [(TrTP)Zn(THF)]2B (5-Zn2) contains two disor-
dered methyl groups. In both structures, non-hydrogen atoms were
refined with anisotropic displacement parameters except disordered
atoms. The hydrogen atoms of p-methyl groups of [(TrTP)Zn-
2+
(THF)]2B and the dichloromethane molecule in the (TPEP)H4
crystal were included in the calculated positions and refined using
a riding model.
(87) KM4 CCD Software: CrysAlis CCD and CrysAlis RED, version 1.171;
Oxford Diffraction Poland: Wrocław, Poland, 2003.
(88) Sheldrick, G. M. SHELXS97: Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(89) Sheldrick, G. M. SHELXL97: Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(85) Balch, A. L.; Latos-Graz˘yn´ski, L.; Noll, B. C.; Phillips, S. L. Inorg.
Chem. 1993, 32, 1124.
(86) Szafert, S.; Gladysz, J. A. Chem. ReV. 2003, 103, 4175.
4532 Inorganic Chemistry, Vol. 44, No. 13, 2005

High- and Low-Spin Iron(III) meso-Ethynylporphyrins
Instrumentation. NMR spectra were recorded on a 500 MHz
Bruker Avance spectrometer equipped with a broadband inverse
gradient probehead. Proton data are referenced to the residual
solvent signals. Mass spectrum of 5-(FeOFe)2 was recorded on the
Voyager-Elite Spectrometer (CBMiM, Ło´dz´, Poland) using the
MALDI-TOF technique.
Supporting Information Available: Crystallographic data in
CIF format. VT NMR data for 1-FeCl, 2-FeCl, 3-FeCl, 4-FeCl,
and 5-(FeCl)2. 1H NMR parameters for zinc(II) ethynylporphyrins,
low-spin iron(III) ethynylporphyrins in methanol-d4 saturated with
KCN and low-spin iron(III) ethynylporphyrins obtained by addition
of (TBA)CN to chloroform-d solution. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This work was supported by the
Ministry of Scientific Research and Information Technology
of Poland (KBN) under Grant 3 T09A 162 28.
IC050158Q
Inorganic Chemistry, Vol. 44, No. 13, 2005 4533