Synthesis and Structural Characterization of Nonplanar Tetraphenylporphyrins and Their Metal Complexes with Graded Degrees of β-Ethyl Substitution

Article abstract of DOI:10.1021/ic970765g

Different porphyrin conformations are believed to play a role in controlling the cofactor properties in natural tetrapyrrole - protein complexes. In order to study the correlation between macrocycle nonplanarity and physicochemical properties in detail, a series of six porphyrins with graded degrees of macrocycle distortion were synthesized via mixed condensation of pyrrole, diethylpyrrole, and benzaldehyde. The formal introduction of successively more β-ethyl groups into the tetraphenylporphyrin parent macrocycle gave access to diethyltetraphenylporphyrin (H₂DETPP), two regioisomers of tetraethyltetraphenylporphyrin (H₂tTETPP, H₂cTETPP), and hexaethyltetraphenylporphyrin (F₂HETPP). These conformationally designed compounds bridge the gap between the well-known tetraphenylporphyrin (H₂TPP) and the very nonplanar octaethyltetraphenylporphyrin (H₂OETPP), which are also formed during the reaction. Crystallographic studies showed that the macrocycle distortion in the solid state increases gradually in the order TPP < DETPP < tTETPP < cTETPP < HETPP < OETPP, i.e. with increasing degree of β-ethyl substitution and the number and localization of potential β-ethyl meso-phenyl interactions. This correlates well with increasing bathochromic shifts of the absorption bands in solution. Depending on the substituent pattern, different saddle-shaped macrocycle conformations were observed. While the conformation of tTETPP was symmetric, DETPP, cTETPP, and HETPP showed asymmetric distortion modes with individual β-pyrrole displacements reaching those described for dodecasubstituted porphyrins. Overall, higher displacements from planarity were found close to β-ethyl-meso-phenyl groups whereas smaller displacements were observed in parts of the molecules bearing β-hydrogen atoms. Nevertheless, a certain amount of redistribution of steric strain occurs as evidenced by significant displacements for pyrrole carbon atoms with β-hydrogens. Synthesis and structural investigation of the respective metal complexes with M = Cu(II), Ni(II), and Zn(II) showed similar correlations between β-ethyl substitution, bathochromic shift of absorption bands and nonplanarity as described for the free bases. The only exception was found for Ni^IItTETPP, which exhibited a highly nonplanar ruffled conformation. Additionally, the metal complexes allowed a study of the conformational effects of different metals at each level of macrocycle distortion. As observed for symmetric, nonplanar porphyrins larger metals led to a decrease in conformational distortion with associated changes in bond lengths and bond angles.

Full text of DOI:10.1021/ic970765g

Inorg. Chem. 1997, 36, 6103-6116
6103
Synthesis and Structural Characterization of Nonplanar Tetraphenylporphyrins and Their
Metal Complexes with Graded Degrees of â-Ethyl Substitution
Mathias O. Senge* and Werner W. Kalisch
Institut fu¨r Organische Chemie (WE02), Freie Universita¨t Berlin,
Takustrasse 3, D-14195 Berlin, Germany
ReceiVed June 19, 1997X
Different porphyrin conformations are believed to play a role in controlling the cofactor properties in natural
tetrapyrrole-protein complexes. In order to study the correlation between macrocycle nonplanarity and
physicochemical properties in detail, a series of six porphyrins with graded degrees of macrocycle distortion
were synthesized via mixed condensation of pyrrole, diethylpyrrole, and benzaldehyde. The formal introduction
of successively more â-ethyl groups into the tetraphenylporphyrin parent macrocycle gave access to diethyltet-
raphenylporphyrin (H2DETPP), two regioisomers of tetraethyltetraphenylporphyrin (H2tTETPP, H2cTETPP), and
hexaethyltetraphenylporphyrin (H2HETPP). These conformationally designed compounds bridge the gap between
the well-known tetraphenylporphyrin (H2TPP) and the very nonplanar octaethyltetraphenylporphyrin (H2OETPP),
which are also formed during the reaction. Crystallographic studies showed that the macrocycle distortion in the
solid state increases gradually in the order TPP < DETPP < tTETPP < cTETPP < HETPP < OETPP, i.e. with
increasing degree of â-ethyl substitution and the number and localization of potential â-ethyl meso-phenyl
interactions. This correlates well with increasing bathochromic shifts of the absorption bands in solution.
Depending on the substituent pattern, different saddle-shaped macrocycle conformations were observed. While
the conformation of tTETPP was symmetric, DETPP, cTETPP, and HETPP showed asymmetric distortion modes
with individual â-pyrrole displacements reaching those described for dodecasubstituted porphyrins. Overall, higher
displacements from planarity were found close to â-ethyl-meso-phenyl groups whereas smaller displacements
were observed in parts of the molecules bearing â-hydrogen atoms. Nevertheless, a certain amount of redistribution
of steric strain occurs as evidenced by significant displacements for pyrrole carbon atoms with â-hydrogens.
Synthesis and structural investigation of the respective metal complexes with M ) Cu(II), Ni(II), and Zn(II)
showed similar correlations between â-ethyl substitution, bathochromic shift of absorption bands and nonplanarity
as described for the free bases. The only exception was found for NiIItTETPP, which exhibited a highly nonplanar
ruffled conformation. Additionally, the metal complexes allowed a study of the conformational effects of different
metals at each level of macrocycle distortion. As observed for symmetric, nonplanar porphyrins larger metals
led to a decrease in conformational distortion with associated changes in bond lengths and bond angles.
Introduction
examples are 2,3,7,8,12,13,17,18-octaalkyl-5,10,15,20-tetra-
arylporphyrins,2b,5-10 dodecaphenylporphyrin (H2DPP),11 2,3,7,8,-
12,13,17,18-octaethyl-5,10,15,20-tetranitroporphyrin,12 and
2,3,7,8,12,13,17,18-octahalo-5,10,15,20-tetraarylporphyrins.13 Due
to their symmetry, these porphyrins are easily prepared via
simple condensation reactions and mostly show highly nonplanar
Porphyrins with nonplanar macrocycle conformations have
attracted considerable attention in recent years.1 This is due to
the hypothesis that fine-tuning of the macrocycle conformation
by the protein scaffold is one way by which nature might control
the physicochemical properties of the cofactors in intact
tetrapyrrole-protein complexes.2 This would account for the
often quite different functions of the same chromophore when
bound to different apoproteins. Indeed, more and more non-
planar tetrapyrrole macrocycle conformations are being identi-
fied in porphyrin-protein complexes.1,3 In order to prepare
suitable model compounds with nonplanar conformations, highly
substituted porphyrins4 have been utilized where steric conges-
tion at the porphyrin periphery leads to distorted macrocycles.
A considerable body of information has now accumulated
for such sterically overloaded porphyrins. The most prominent
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* Corresponding author. E-mail: mosenge@chemie.fu-berlin.de.
X Abstract published in AdVance ACS Abstracts, December 1, 1997.
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S0020-1669(97)00765-9 CCC: $14.00 © 1997 American Chemical Society

6104 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
saddle-shaped macrocycle conformations.14 Ruffled conforma-
tions can be induced either by metal effects or via bulky meso-
alkyl substituents11b,15 while “dome-”12b or “wave-” type11c,13b
distortion modes are found less frequently. In this context,
2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin
(H2OETPP), the structural hybrid of the planar octaethylpor-
phyrin (H2OEP) and tetraphenylporphyrin (H2TPP), has become
a kind of standard nonplanar porphyrin of choice and has been
employed for a variety of physical, theoretical, and spectroscopic
studies on porphyrin nonplanarity.5b,10
Nevertheless, several important questions remain to be
addressed. Naturally occurring pigments have asymmetric
substituent patterns and show distortions smaller than those
observed in highly nonplanar dodecasubstituted porphyrins.
Thus, a more detailed investigation of asymmetrically substituted
porphyrins with various degrees of conformational distortion
seemed advisable. In addition, most physicochemical studies
on nonplanar porphyrins have studied all-or-nothing effects, e.g.
by comparing a planar porphyrin like H2TPP or H2OEP with a
very nonplanar porphyrin like H2OETPP. In order to aid in
the interpretation of the physicochemical data, rationally planned
series of closely related porphyrins with different degree of
macrocycle distortion are necessary. While some attempts have
been made in this direction,5,13b,16,17 either related planar
compounds are not available for comparison or only fragmentary
structural data have yet been published.
(6) (a) Evans, B.; Smith, K. M.; Fuhrhop, J.-H. Tetrahedron Lett. 1977,
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Therefore, we have embarked on a comprehensive study of
asymmetrically substituted porphyrins and prepared a series of
porphyrins with graded degrees of distortion in order to study
the effect of different substituent patterns on the conformation.
This should allow a more detailed correlation of the relationship
between conformational distortion and (photo)physical proper-
ties. In light of the wealth of structural and physicochemical
data available for the sterically unhindered H2TPP and H2OEP
and now for the nonplanar H2OETPP, a porphyrin series of
choice seemed accessible via synthesis of ethyl-substituted
tetraphenylporphyrins with intermediate degree of â-ethyl-
substituted pyrrole rings closing the “conformational gap”
between H2TPP and H2OETPP. This would give a series of
six closely related porphyrins providing enough data points for
a more detailed analysis. While preliminary results on the
synthesis of the porphyrins have been reported in a communica-
tion,18 we report here on the synthesis and properties of the
free bases and metal complexes and give detailed structural
information from crystal structure determinations for all com-
pounds.
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Smith, K. M.; Fajer, J. J. Am. Chem. Soc. 1993, 115, 3627.
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Spectrosc. 1992, 23, 523. Kadish, K. M.; Van Caemelbecke, E.;
Boulas, P.; D’Souza, F.; Vogel, E.; Kisters, M.; Medforth, C. J.; Smith,
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Stenner, R.; Dreybrodt, W.; Mak, R. S. W.; Li, X.-y.; Sparks, L. D.;
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97, 3701. Choi, S.; Phililips, J. A.; Ware, W., Jr.; Wittschieben, C.;
Medforth, C. J.; Smith, K. M. Inorg. Chem. 1994, 33, 3873.
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K. M.; Fajer, J.; Holten, D. J. Am. Chem. Soc. 1994, 116, 7363. Kadish,
K. M.; Van Caemelbecke, E.; D’Souza, F.; Medforth, C. J.; Smith,
K. M.; Tabard, A.; Guilard, R. Organometallics 1993, 12, 2411; Inorg.
Chem. 1995, 34, 2984. Gentemann, S.; Nelson, N. Y.; Jaquinod, L.;
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J. S.; Ryan, D. E.; Blackwood, M. E., Jr.; Spiro, T. G. Inorg. Chem.
1997, 36, 764. Sibilia, S. A.; Hu, S.; Piffat, C.; Melamed, D.; Spiro,
T. G. Inorg. Chem. 1997, 36, 1013.
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Chem. 1992, 31, 2877. Takeda, J.; Sato, M. Chem. Lett. 1995, 939,
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Shelnutt, J. A. J. Am. Chem. Soc. 1992, 114, 9859. (c) Nurco, D. J.;
Medforth, C. J.; Forsyth, T. P.; Olmstead, M. M.; Smith, K. M. J.
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87, 2933. Hobbs, J. D.; Majumder, S. A.; Luo, L.; Sickelsmith, G.
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Experimental Section
General Procedures. Melting points were measured with a Reichert
Thermovar instrument and are uncorrected. 1H-NMR spectra were
obtained in deuteriochloroform at 270 or 500 MHz using a Bruker AM
270 or AMX 500 spectrometer; chemical shifts are expressed in ppm
relative to tetramethylsilane. Elemental analyses were performed on
a Perkin-Elmer 240 elemental analyzer. Electronic absorption spectra
were recorded on a UV/vis Specord S10 (Carl Zeiss) using dichlo-
romethane for the metal complexes, dichloromethane with 1% triethyl-
amine for the free bases, and dichloromethane with 1% TFA for the
dications as solvents. Mass spectra were measured on a Varian MAT
711 spectrometer. Purification of the metal complexes were performed
by using either silica gel 60 or Brockmann grade III basic alumina.
Reactions were monitored by analytical TLC using precoated stripes
of ALOX 60 or silica gel 60 plates.
Mixed Synthesis of H2TPP, H2DETPP, H2tTETPP, H2cTETPP,
H2HETPP, and H2OETPP. A 1.34 g (0.02 mol) quantity of pyrrole,
2.46 g (0.02 mol) of diethylpyrrole, 4.24 g (0.04 mol) of benzaldehyde,
and 0.5 mL (0.004 mol) of BF3‚OEt2 were added to a 2 L round-bottom
flask charged with 2 L of dry dichloromethane, and the reaction mixture
was stirred for 12 h under argon. A 9.2 g (0.04 mol) quantity of DDQ
was added all at once, and the solution was stirred for 1 h.
(13) (a) Bhyrappa, P.; Krishnan, V. Inorg. Chem. 1991, 20, 239. Mandon,
D.; Ochsenbein, P.; Fischer, J.; Weiss, R.; Jayaraj, K.; Austin, R. N.;
Gold, A.; White, P. S.; Brigaud, O.; Battioni, P.; Mansuy, D. Inorg.
Chem. 1992, 31, 2044. Henling, L. M.; Schaefer, W. P.; Hodge, J.
A.; Hughes, M. E.; Gray, H. B. Acta Crystallogr. 1993, C49, 1743.
Bhyrappa, P.; Nethaji, M.; Krishnan, V. Chem. Lett. 1993, 869.
Bhyrappa, P.; Krishnan, V.; Nethaji, M. J. Chem. Soc., Dalton Trans.
1993, 1901. Ochsenbein, P.; Mandon, D.; Fischer, J.; Weiss, R.; Austin,
R.; Jayaraj, K.; Gold, A.; Terner, J.; Bill, E.; Mu¨ther, M.; Trautwein,
A. X. Angew. Chem., Int. Ed. Engl. 1993, 32, 1437. Birnbaum, E. R.;
Hodge, J. A.; Grinstaff, M. W.; Schaefer, W. P.; Henling, L.; Labinger,
J. A.; Bercaw, J. E.; Gray, H. B. Inorg. Chem. 1995, 34, 3625. (b)
Ochsenbein, P.; Ayougou, K.; Mandon, D.; Fischer, J.; Weiss, R.;
Austin, R. N.; Jayaraj, K.; Gold, A.; Terner, J.; Fajer, J. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 348.
(14) For definitions of the different distortion modes see: Scheidt, W. R.;
Lee, Y. J. Struct. Bonding (Berlin) 1987, 64, 1.
(15) (a) Ema, T.; Senge, M. O.; Nelson, N. Y.; Ogoshi, H.; Smith, K. M.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1879. (b) Senge, M. O.; Ema,
T.; Smith, K. M. J. Chem. Soc., Chem. Commun. 1995, 733.
(16) Takeda, J.; Sato, M. Tetrahedron Lett. 1994, 35, 3565; Chem. Lett.
1994, 2233.
(17) Chan, K. S.; Zhou, X.; Luo, B.-s.; Mak, T. C. W. J. Chem. Soc., Chem.
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(18) Kalisch, W. W.; Senge, M. O. Tetrahedron Lett. 1996, 37, 1183.

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6105
(4.09), 663 (4.67). 1H-NMR (500 MHz, CDCl3): δ -3.04 (br s, 1H,
3
NH), -2.45 (br s, 1H, NH), 1.00 (t, J ) 7.5 Hz, 6H, CH3), 2.85 (m,
4H, CH2), 7.72 (m, 12H, Hm-Ph, Hp-Ph), 8.20 (m, 8H, Ho-Ph), 8.56 (d,
3
3J ) 5 Hz, 2H, Hpyrrole, 7-H, 18-H), 8.67 (d, J ) 5 Hz, 2H, Hpyrrole
,
8-H, 17-H), 8.94 (s, 2H, Hpyrrole, 12-H, 13-H). MS, m/z (relative
intensity, %): 670 (100) [M+], 335 (12) [M2+]. HRMS, m/z: calcd
for C48H38N4, 670.30965; found, 670.30926. Anal. Calcd for
C48H38N4: C, 85.94; H, 5.71; N, 8.35. Found: C, 85.77; H, 5.78; N,
8.18.
2,3,12,13-Tetraethyl-5,10,15,20-tetraphenylporphyrin, H2tTETPP.
Mp: 296-298 °C. UV/vis (CH2Cl2 + 1% NEt3), λmax, nm (log ꢀ):
426 (5.47), 527 (4.17), 593 (3.70), 649 (3.32). UV/vis (CH2Cl2 + 1%
TFA), λmax, nm (log ꢀ): 451 (5.55), 668 (4.58). 1H-NMR (500 MHz,
3
CDCl3): δ -2.60 (s, 2H, NH), 0.86 (t, J ) 7.5 Hz, 12H, CH3), 2.81
3
(q, J ) 7.5 Hz, 8H, CH2), 7.66-7.78 (m, 12H, Hm-Ph, Hp-Ph), 8.21
(m, 8H, Ho-Ph), 8.30 (s, 4H, Hpyrrole). MS, m/z (relative intensity, %):
726 (100) [M+], 698 (44), 363 (6) [M2+]. HRMS, m/z: calcd for
C52H46N4, 726.372 25; found, 726.372 93. Anal. Calcd for
C52H46N4‚H2O: C, 83.84; H, 6.49; N, 7.52. Found: C, 83.80; H, 6.28;
N, 7.24.
2,3,7,8-Tetraethyl-5,10,15,20-tetraphenylporphyrin, H2cTETPP.
Mp: 315-316 °C. UV/vis (CH2Cl2 + 1% NEt3), λmax, nm (log ꢀ):
433 (5.38), 540 (4.15), 575 (3.92), 604 (3.82), 672 (3.63). UV/vis (CH2-
Cl2 + 1% TFA), λmax, nm (log ꢀ): 455 (5.55), 588 sh (3.52), 621 sh
(3.90), 675 (4.67). 1H-NMR (250 MHz, CDCl3): δ -2.38 (br s, 2H,
3
NH), 0.46 (m, 6H, CH3), 0.68 (t, J ) 7.5 Hz, 6H, CH3), 2.36 (br s,
4H, CH2), 2.56 (br s, 4H, CH2), 7.74 (m, 12H, Hm-Ph, Hp-Ph), 8.36 (m,
8H, Ho-Ph), 8.56 (s, 4H, Hpyrrole). MS, m/z (relative intensity, %): 726
(100) [M+], 711 (10), 698 (44), 679 (11), 363 (15) [M2+]. HRMS,
m/z: calcd for C52H46N4, 726.372 25; found, 726.372 11. Anal. Calcd
for C52H46N4: C, 85.92; H, 6.38; N, 7.71. Found: C, 85.88; H, 6.43;
N, 7.53.
2,3,7,8,12,13-Hexaethyl-5,10,15,20-tetraphenylporphyrin,
H2HETPP. Mp: 295-297 °C. UV/vis (CH2Cl2 + 1% NEt3), λmax
,
nm (log ꢀ): 444 (5.35), 544 (4.12), 588 (3.90), 623 (3.72), 685 (3.45).
UV/vis (CH2Cl2 + 1% TFA), λmax, nm (log ꢀ): 462 (5.54), 570 sh
(3.82), 525 sh (4.08), 683 (4.61). 1H-NMR (250 MHz, CDCl3): δ
-2.23 (br s, 2H, NH), 0.35 (m, 6H, CH3), 0.48 (m, 6H, CH3), 0.66 (m,
6H, CH3), 1.49 (m, 2H, CH2), 2.15 (m, 4H, CH2), 2.55 (m, 6H, CH2),
7.65 (m, 12H, Hm-Ph, Hp-Ph), 8.25 (m, 10H, Ho-Ph, Hpyrrole). MS, m/z
(relative intensity, %): 782 (100) [M+], 392 (13) [M2+]. HRMS, m/z:
calcd for C56H54N4, 782.434 85; found: 782.434 36. Anal. Calcd for
C56H54N4‚0.5MeOH: C, 84.92; H, 7.06; N, 7.01. Found: C, 84.78;
H, 6.90; N, 6.81.
Metal Complexes. Most Zn, Ni, and Cu complexes were prepared
from the corresponding free-base porphyrins using standard metal
acetate methodology.19 The preparation of ZnIIcTETPP and ZnII
-
Subsequently, the reaction mixture was filtered through alumina
followed by column chromatography on Brockmann grade III basic
alumina using toluene with an increasing content of methanol as eluant.
Three crude fractions were obtained which showed the following
composition: (a) H2TPP/H2DETPP, (b) H2tTETPP/H2cTETPP, and (c)
H2HETPP/H2OETPP. H2TPP and H2DETPP were separated on a silica
gel column, eluting with toluene/hexane, 1/1 (v/v), while trans- and
cis-TETPP could be separated using an alumina column, eluting with
toluene containing 0.5% methanol. The third crude fraction, containing
H2HETPP and H2OETPP, could not be separated directly. Thus, the
free bases were converted into the corresponding iron(III) chloride
derivatives and separated by column chromatography on alumina
(toluene containing 1% NEt3) followed by demetalation to the free
bases. Alternatively and more conveniently, the H2HETPP and H2-
OETPP mixture could be converted to the respective Ni(II) complexes,
which could then be separated via preparative HPLC using a silica gel
column and 2% THF in hexane as eluant, followed by demetalation.
Recrystallization of the individual fractions from dichloromethane/
methanol yielded deep purple crystals: 1.12 g (16.8%) of H2TPP, 0.97
g (14.4%) of H2DETPP, 0.12 g (1.65%) of H2tTETPP, 0.88 g (12.1%)
of H2cTETPP, 0.65 g (9.8%) of H2HETPP, and 1.21 g (18.1%) of H2-
OETPP.
HETPP could more easily be performed by the following method. E.g.,
70 mg (0.09 mmol) of H2HETPP, 200 mg (0.9 mmol) of anhydrous
zinc bromide, and 330 mg of active potassium carbonate (2.4 mmol)
were stirred in 2 mL of dry THF and 10 mL of dichloromethane for
30 min. After filtration, the solvent was removed in vacuo, the residue
was dissolved again in dichloromethane with a trace of dry methanol,
and the solution was filtered again. Recrystallization from dichlo-
romethane/hexane under anhydrous conditions yielded 70 mg (0.08
mmol, 90%) of deep violet crystals of ZnIIHETPP.
(2,3-Diethyl-5,10,15,20-tetraphenylporphyrinato)zinc(II), ZnIIDE-
TPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log ꢀ): 420 (5.71),
550 (4.33). 1H-NMR (500 MHz, CDCl3): δ 1.08 (t, 3J ) 7.5 Hz, 6H,
3
CH3), 2.82 (q, J ) 7.5 Hz, 4H, CH2), 7.62-7.80 (m, 12H, Hm-Ph
,
3
H
p-Ph), 8.19 (m, 8H, Ho-Ph), 8.70 (d, J ) 6.5 Hz, 2H, Hpyrrole, 7-H,
18-H), 8.84 (d, 3J ) 6.5 Hz, 2H, Hpyrrole, 8-H, 17-H), 8.88 (s, 2H, Hpyrrole
,
12-H, 13-H). MS, m/z (relative intensity, %): 732 (100) [M+], 688
(20), 611 (34), 366 [M2+]. Anal. Calcd for C48H36N4Zn: C, 78.52;
H, 4.94; N, 7.63. Found: C, 78.52; H, 5.05; N, 7.37.
(2,3,12,13-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)zinc-
(II), ZnIItTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 424 (5.33), 554 (3.97). 1H-NMR (500 MHz, CDCl3): δ 0.93 (t, 3J
) 7.5 Hz, 12H, CH3), 2.75 (q, 3J ) 7.5 Hz, 8H, CH2), 7.66-7.76 (m,
2,3-Diethyl-5,10,15,20-tetraphenylporphyrin, H2DETPP. Mp:
324-325 °C. UV/vis (CH2Cl2 + 1% NEt3), λmax, nm (log ꢀ): 420
(5.62), 521 (4.27), 555 (3.74), 591 (3.81), 645 (3.53). UV/vis (CH2-
Cl2 + 1% TFA), λmax, nm (log ꢀ): 445 (5.61), 555 sh (3.79), 605 sh
(19) Smith, K. M., Ed. Porphyrins and Metalloporphyrins; Elsevier:
Amsterdam, 1975.

6106 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
Table 1. Crystal Data and Data Collection Parameters for the Compounds Studied
H2DETPP
empirical formula C48H38N4
H2tTETPP
H2cTETPP
H2HETPP
NiIIDETPP
NiIItTETPP
C52H44N4Ni
C52H46N4‚CH2Cl2
C52H46N4‚2CH3OH C56H54N4‚1.3CH2Cl2 C48H36N4Ni
crystal size, mm
color
habit
mol wt
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
1 × 0.58 × 0.52 0.25 × 0.25 × 0.19 0.2 × 0.18 × 0.12 0.6 × 0.6 × 0.2
0.44 × 0.3 × 0.08 0.36 × 0.24 × 0.16
red
blue
black
block
blue-black
irregular shape
893.4
red
red
irregular shape
670.8
Cc
18.333(12)
20.664(14)
10.180(6)
90
109.65(5)
90
3632(4)
4
1.227
0.072
Mo KR
0.710 73
rhombus
811.9
P21/c
13.531(6)
28.172(11)
12.184(4)
90
112.55(3)
90
4289(3)
4
1.257
1.676
Cu KR
1.541 78
plate
rhombus
783.6
C2
18.087(8)
12.239(3)
18.037(7)
90
92.67(3)
90
3989(3)
4
1.305
1.019
Cu KR
1.541 78
Siemens P4/RA
130
791.01
P21/c
16.992(5)
16.206(3)
17.247(6)
90
115.66(2)
90
4281(2)
4
1.227
0.578
Cu KR
1.541 78
Siemens P4/RA
118
727.5
P21/c
13.198(9)
8.385(6)
29.227(9)
90
90.72(4)
90
3479(4)
4
1.389
1.126
Cu KR
1.541 78
Syntex P21
130
P21/c
11.274(4)
17.186(7)
25.339(9)
90
98.51(3)
90
4856(3)
4
1.222
Z
D
calcd, g‚cm-3
µ, mm-1
radiation
λ, Å
0.209
Mo KR
0.710 73
Siemens R3m/V
293
diffractometer
T, K
Siemens R3m/V Syntex P21
130
130
θ
max, deg
no. of indep reflns 4412
27.52
57.06
5796
3595
366
0.116
0.264
0.175
0.309
1.053
56.08
5589
3948
542
0.068
0.168
0.101
0.195
24
7616
4056
578
0.086
0.224
0.162
0.290
54.1
4218
2841
311
0.087
0.212
0.128
0.245
1.037
56.4
2778
2633
347
0.062
0.162
0.066
0.170
0.959
no. of obs reflns
no. of params
3664
469
0.052
R1 (I > 2.0σ(I))a
wR2 (I > 2.0σ(I))b 0.137
R1 (all data)a
wR2 (all data)b
S
0.067
0.160
0.792
1.05
1.026
NiIIcTETPP
NiIIHETPP
C56H52N4Ni
CuIIDETPP
C48H36N4Cu
CuIItTETPP
CuIIcTETPP
CuIIHETPP
empirical formula
crystal size, mm
color
C52H44N4Ni
1 × 0.3 × 0.15
blue
C52H44N4Cu‚CH2Cl2 C52H44N4Cu
C56H52N4Cu
0.55 × 0.38 × 0.1 0.24 × 0.16 × 0.03 0.52 × 0.26 × 0.22
0.8 × 0.03 × 0.02 0.4 × 0.16 × 0.1
red
red
red
red
black
habit
parallelepiped
783.6
P1h
parallelepiped
839.7
P1h
parallelepiped
732.4
P1h
parallelepiped
873.4
P1h
fiber
788.5
P1h
parallelepiped
844.6
P1h
mol wt
space group
a, Å
b, Å
c, Å
10.602(5)
13.112(7)
16.085(11)
113.53(4)
92.84(6)
99.34(4)
2007(2)
2
1.297
0.526
Mo KR
0.710 73
12.735(3)
12.915(3)
14.007(3)
78.37(2)
68.89(2)
83.84(2)
2103.5(8)
2
1.326
1.000
Cu KR
1.541 78
13.658(4)
14.279(4)
18.569(5)
92.68(2)
97.72(2)
93.52(2)
3576(2)
4 (2 indep mol)
1.360
12.321(3)
13.429(4)
13.679(4)
99.80(2)
94.14(2)
105.83(2)
2128.8(10)
2
1.363
2.202
Cu KR
1.541 78
Syntex P21
126
10.471(3)
13.201(3)
16.211(6)
113.74(2)
92.77(3)
99.00(2)
2010.5(10)
2
1.302
0.585
Mo KR
0.710 73
Siemens R3m/V
293
12.826(7)
12.920(7)
14.207(7)
78.98(4)
69.02(4)
84.49(5)
2157(2)
2
1.301
0.550
Mo KR
0.710 73
Siemens R3m/V
293
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, g‚cm-3
µ, mm-1
radiation
λ, Å
1.175
Cu KR
1.541 78
Siemens P4/RA
120
diffractometer
T, K
Siemens R3m/V Syntex P21
293
130
θ
max, deg
no. of indep reflns 9206
27.5
56.44
5643
4603
428
0.068
0.172
0.084
0.201
1.037
57.04
9456
7057
956
0.053
0.121
0.079
0.138
57.04
5753
4479
541
0.059
0.139
0.080
0.153
25
7109
4195
397
0.078
0.171
0.145
0.221
25
7578
4333
551
0.070
0.130
0.146
0.180
no. of obs refls
no. of params
5878
515
0.060
R1 (I > 2.0σ(I))a
wR2 (I > 2.0σ(I))b 0.146
R1 (all data)a
wR2 (all data)b
S
0.105
0.197
0.776
1.021
1.034
1.025
1.012
ZnIIDETPP(â-pic) ZnIIDETPP(MeOH)
ZnIItTETPP(pyr)
ZnIIcTETPP(pyr)
ZnIIHETPP
ZnIIHETPP(pyr)
empirical formula C54H43N5Zn
C49H40N4OZn
C57H49N5Zn‚0.4H2O C57H49N5Zn
C56H52N4Zn
C61H57N5Zn‚2CH2Cl2
crystal size, mm
color
habit
0.4 × 0.4 × 0.4
0.43 × 0.4 × 0.04 0.75 × 0.3 × 0.22
0.8 × 0.4 × 0.3 0.83 × 0.43 × 0.25 0.8 × 0.7 × 0.6
red
red
plate
red
red
red-black
irregular block
846.4
blue-black
irregular block
1095.3
cube
parallelepiped
876.6
parallelepiped
869.38
mol wt
space group
a, Å
b, Å
c, Å
827.3
P1h
766.2
P1h
P1h
P1h
P1h
Cc
10.033(2)
16.124(4)
16.447(5)
60.94(2)
83.16(2)
85.73(2)
10.387(4)
10.808(5)
17.503(12)
92.19(5)
95.88(4)
97.81(3)
12.800(4)
13.985(6)
14.152(5)
85.08(3)
68.22(3)
72.60(3)
12.142(3)
13.794(4)
15.574(5)
69.06(3)
72.05(2)
69.93(2)
12.736(3)
12.775(4)
14.214(3)
79.55(2)
68.39(2)
85.21(2)
17.284(5)
21.509(6)
16.118(4)
90
111.55(2)
90
R, deg
â, deg
γ, deg

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6107
Table 1 (Continued)
ZnIIDETPP(â-pic)
ZnIIDETPP(MeOH)
ZnIItTETPP(pyr)
ZnIIcTETPP(pyr)
ZnIIHETPP
ZnIIHETPP(pyr)
V, Å3
2309(1)
2
1934(2)
2
2243.9(14)
2
2236.5(11)
2
1.291
2114.1(9)
2
5573(3)
4
Z
D
calcd, g‚cm-3
1.190
0.572
Mo KR
0.710 73
Siemens R3m/V
293
1.316
1.212
Cu KR
1.541 78
Syntex P21
130
1.297
1.108
Cu KR
1.541 78
Syntex P21
126
1.330
1.140
Cu KR
1.541 78
Syntex P21
126
1.305
0.677
Mo KR
0.710 73
Siemens R3m/V
126
µ, mm-1
radiation
λ, Å
0.594
Mo KR
0.710 73
Siemens R3m/V
126
diffractometer
T, K
θ
max, deg
26
9086
6565
542
0.068
0.202
0.097
0.257
0.819
57.04
5217
3848
57.04
6072
5075
27.5
10282
6493
568
0.062
0.124
0.119
0.157
1.017
57.01
6002
4046
27.5
6610
6014
658
0.045
0.096
0.038
0.088
1.020
no. of indep reflns
no. of obs reflns
no. of params
R1 (I > 2.0σ(I))a
wR2 (I > 2.0σ(I))b
R1 (all data)a
wR2 (all data)b
S
497
560
413
0.083
0.208
0.111
0.234
1.024
0.060
0.149
0.073
0.162
1.028
0.064
0.164
0.068
0.167
1.044
2
2
a R1 ) ∑||Fo - Fc||/∑|Fo|. b wR2 ) [∑(w(Fo - Fc2)2)/∑(w(Fo )2)]1/2
.
12H, Hm-Ph, Hp-Ph), 8.19 (m, 8H, Ho-Ph), 8.58 (s, 4H, Hpyrrole). MS,
m/z (relative intensity, %): 788 (100) [M+], 394 (12) [M2+]. Anal.
Calcd for C52H44N4Zn: C, 79.03; H, 5.56; N, 7.09. Found: C, 78.75;
H, 5.39; N, 6.78.
(6) [M2+]. Anal. Calcd for C48H36N4Ni: C, 79.24; H, 4.99; N, 7.70.
Found: C, 79.15; H, 5.11; N, 7.66.
(2,3,12,13-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)nickel-
(II), NiIItTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 423 (5.38), 544 (4.43), 581 (4.27). 1H-NMR (500 MHz, CDCl3):
(2,3,7,8-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)zinc-
(II), ZnIIcTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 431 (5.42), 561 (4.16), 611 sh (3.34). 1H-NMR (500 MHz,
CDCl3): δ 0.58, 0.81 (each t, 3J ) 7.5 Hz, 12H, CH3), 2.40, 2.67 (each
3
3
δ 0.76 (t, J ) 7.5 Hz, 12H, CH3), 2.59 (q, J ) 7.5 Hz, 8H, CH2),
7.59-7.70 (m, 12H, Hm-Ph, Hp-Ph), 7.98 (m, 8H, Ho-Ph), 8.36 (s, 4H,
H
pyrrole). MS, m/z (relative intensity, %): 782 (100) [M+], 738 (11),
709 (16), 391 (23) [M2+]. Anal. Calcd for C52H44N4Ni: C, 79.70; H,
5.66; N, 7.15. Found: C, 79.86; H, 5.93; N, 6.89.
3
q, J ) 7.5 Hz, 8H, CH2), 7.66-7.85 (m, 12H, Hm-Ph, Hp-Ph), 8.17-
8.39 (m, 8H, Ho-Ph), 8.63, 8.70 (each d, 3J ) 5 Hz, 4H, Hpyrrole). MS,
m/z (relative intensity, %): 788 (100) [M+], 715 (11), 394(13) [M2+].
Anal. Calcd for C52H44N4Zn‚0.5MeOH: C, 78.20; H, 5.75; N, 6.95.
Found: C, 78.26; H, 5.61; N, 6.81.
(2,3,7,8-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)nickel-
(II), NiIIcTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 424 (5.38), 541 (4.23), 575 (3.98). 1H-NMR (500 MHz, CDCl3):
δ 0.51, 0.72 (each t, 3J ) 7.5 Hz, 12H, CH3), 2.31, 2.50 (each q, 3J )
7.5 Hz, 8H, CH2), 7.67 (m, 12H, Hm-Ph, Hp-Ph), 8.09 (m, 8H, Ho-Ph),
8.39, 8.44 (each d, 3J ) 5 Hz, 4H, Hpyrrole). MS, m/z (relative intensity,
%): 782 (100) [M+], 709 (10), 679 (11), 391 (15) [M2+]. Anal. Calcd
for C52H44N4Ni: C, 79.70; H, 5.66; N, 7.15. Found: C, 79.69; H,
5.74; N, 6.84.
(2,3,7,8,12,13-Hexaethyl-5,10,15,20-tetraphenylporphyrinato)-
zinc(II), ZnIIHETPP. Mp: > 330 °C. UV/vis (CH2Cl2), λmax, nm
(log ꢀ): 443 (5.38), 572 (4.30). 1H-NMR (250 MHz, CDCl3): δ 0.49,
3
0.51, 0.71 (each t, J ) 7.5 Hz, 18H, CH3), 2.35, 2.37, 2.61 (each q,
3J ) 7.5 Hz, 12H, CH2), 7.62-7.85 (m, 12H, Hm-Ph, Hp-Ph), 8.21-
8.43 (m, 8H, Ho-Ph), 8.46 (s, 2H, Hpyrrole). MS, m/z (relative intensity,
%): 844 (100) [M+], 422 (19) [M2+]. Anal. Calcd for C56H52N4-
Zn‚H2O: C, 77.81; H, 6.30; N, 6.48. Found: C, 77.60; H, 6.14; N,
6.24.
(2,3,7,8,12,13-Hexaethyl-5,10,15,20-tetraphenylporphyrinato)-
nickel(II), NiIIHETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm
(log ꢀ): 429 (5.36), 546 (4.43), 585 (4.31). 1H-NMR (250 MHz,
3
CDCl3): δ 0.49, 0.50, 0.67 (each t, J ) 7.5 Hz, 18H, CH3), 2.23,
(2,3-Diethyl-5,10,15,20-tetraphenylporphyrinato)copper(II),
CuIIDETPP. Mp: 345 °C. UV/vis (CH2Cl2), λmax, nm (log ꢀ): 417
(5.61), 543 (4.28). MS, m/z (rel. int, %): 731 (100), [M+], 657 (23),
609 (33), 365 (14) [M2+]. Anal. Calcd for C48H36N4Cu: C, 78.72; H,
4.95; N, 7.65. Found: C, 78.75; H, 5.12; N, 7.40.
2.28, 2.47 (each q, 3J ) 7.5 Hz, 12H, CH2), 7.58-7.71 (m, 12H, Hm-Ph
,
H
p-Ph), 8.05-8.12 (m, 8H, Ho-Ph), 8.15 (s, 2H, Hpyrrole). MS, m/z
(relative intensity, %): 838 (100) [M+], 419 (18) [M2+]. Anal. Calcd
for C56H52N4Ni: C, 80.07; H, 6.24; N, 6.67. Found: C, 79.89; H,
6.27; N, 6.50.
(2,3,12,13-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)copper-
(II), CuIItTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 422 (5.33), 552 (3.34). MS, m/z (rel. int, %): 787 (100) [M+],
759 (19), 393 (7) [M2+]. Anal. Calcd for C52H44N4Cu: C, 79.21; H,
5.62; N, 7.11. Found: C, 79.38; H, 5.80; N, 6.71.
X-ray Crystallography. Suitable single crystals of the listed
compounds often could be obtained by slow diffusion of a concentrated
solution of the porphyrin in methylene chloride into methanol. Single
crystals of H2tTETPP and H2HETPP were grown from CH2Cl2/
CH3OH containing 2% KOH. ZnIIDETPP(â-pic) was crystallized from
CH2Cl2/CH3OH containing 5% â-picoline. ZnIIcTETPP(pyr) and
ZnIIHETPP(pyr) crystals were grown from CH2Cl2/CH3OH containing
10% pyridine while Zn(II)tTETPP(pyr) was crystallized from CDCl3/
CH3OH containing 10% pyridine. H2DETPP crystals were obtained
from CHCl3/hexanes, and CuIItTETPP was crystallized from CH2Cl2/
C2H5OH. The crystals were immersed in hydrocarbon oil (Paratone
N), and a single crystal was selected, mounted on a glass fiber, and
placed in the low-temperature N2 stream.20a Intensity data were
collected either using a Siemens R3m/V or Syntex P21 automatic four-
circle diffractometer equipped with a graphite monochromator and
locally modified low-temperature devices or using a Siemens P4
instrument equipped with a Siemens LT device and a Siemens rotating
anode, operating at 50 kV and 300 mA. Cell parameters for the
(2,3,7,8-Tetraethyl-5,10,15,20-tetraphenylporphyrinato)copper-
(II), CuIIcTETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 424 (5.47), 548 (4.43), 562 sh (3.35). MS, m/z (relative intensity,
%): 787 (100) [M+], 393 (22) [M2+]. Anal. Calcd for C52H44N4Cu:
C, 79.21; H, 5.62; N, 7.11. Found: C, 79.32; H, 5.81; N, 6.87.
(2,3,7,8,12,13-Hexaethyl-5,10,15,20-tetraphenylporphyrinato)cop-
per(II), CuIIHETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log
ꢀ): 429 (5.45), 547(4.45), 566 (4.49). MS, m/z (relative intensity, %):
843 (100) [M+], 421 (19) [M2+]. Anal. Calcd for C56H52N4-
Cu‚0.5H2O: C, 78.80; H, 6.26; N, 6.56. Found: C, 78.58; H, 6.28;
N, 6.66.
(2,3-Diethyl-5,10,15,20-tetraphenylporphyrinato)nickel(II),
NiIIDETPP. Mp: >350 °C. UV/vis (CH2Cl2), λmax, nm (log ꢀ): 419
(5.41), 535 (4.25), 571 sh (3.75). 1H-NMR (500 MHz, CDCl3): δ
0.88 (t, 3J ) 7.5 Hz, 6H, CH3), 2.66 (q, 3J ) 7.5 Hz, 4H, CH2), 7.54-
7.71 (m, 12H, Hm-Ph, Hp-Ph), 7.89-8.02 (m, 8H, Ho-Ph), 8.59 (s, 4H,
(20) (a) Hope, H. ACS Symp. Ser. 1987, 357, 257; Prog. Inorg. Chem.
1994, 41, 1. (b) Parkin, S. R.; Moezzi, B.; Hope, H. J. Appl.
Crystallogr. 1995, 28, 53. (c) SHELXTL PLUS, Version 5.03; Siemens
Analytical Instruments, Inc.: Madison, WI, 1994.
H
pyrrole, 7-H, 8-H, 17-H, 18-H), 8.65 (s, 2H, Hpyrrole, 12-H, 13-H). MS,
m/z (relative intensity, %): 726 (100) [M+], 682 (15), 605 (27), 363

6108 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
structures measured with Mo KR radiation were determined from 20-
30 reflections in the range 10° e θ e 15°; for structures measured
with Cu KR radiation, the range 20° e θ e 30° was used. Two
standard reflections were measured every 198 reflections and showed
only statistical variation in intensity during data collection (<2%
intensity change in most cases). The intensities were corrected for
Lorentz and polarization effects. With the exception of the structure
of H2DETPP, absorption corrections were applied using the program
XABS2;20b extinction effects were mostly disregarded. The free-base
porphyrin structures were solved using direct methods, while the
metalloporphyrin structures were solved via Patterson syntheses fol-
lowed by subsequent structure expansion using the SHELXTL PLUS
program system.20c Refinements were carried out by full-matrix least-
squares calculation based on |F2| using the same program system.
Hydrogen atoms were included at calculated positions by using a riding
model (C-H distance 0.96 Å, N-H distance 0.9 Å). Normally, no
hydrogen atoms were included for solvate molecules. All calculations
were carried out on a Silicon Graphics Indy workstation. Unless
otherwise stated, all non-hydrogen atoms were refined with anisotropic
thermal parameters.
In the structures of H2tTETPP, NiIIDETPP, NiIItTETPP, and
Zn(II)HETPP, the phenyl rings were refined with isotropic thermal
parameters as rigid groups (hexagon with C-C distances of 1.39 Å).
H2tTETPP crystallized with two disordered methylene chloride mol-
ecules of solvation. The chlorine atoms were refined as disordered
over two and three split positions. A similar situation was encountered
in the structure of H2HETPP. One solvate methylene chloride was
refined with the chlorine atoms disordered over two (Cl1S) and three
(Cl2S) split positions. The other CH2Cl2 molecule was situated on an
inversion center and was refined with 30% occupancy. The crystals
of NiIItTETPP were twinned and refined using the TWIN routine of
the XL program. Due to the twinning, some of phenyl carbon atoms
showed relatively high thermal parameters. Attempts to utilize disorder
models for the phenyl rings failed and resulted in unreasonably distorted
phenyl rings. In the structure of NiIIHETPP, only the nickel and side
chain ethyl and phenyl carbon atoms were refined with anisotropic
thermal parameters. CuIIcTETPP was refined with isotropic thermal
parameters for the phenyl carbon atoms. The structure of ZnIItTETPP-
(pyr) contains a disordered axial pyridine. The axial ligand was refined
as disordered over two split positions with occupancies of 0.6 and 0.4,
each. To account for residual electron density close to the major
pyridine fraction, a water molecule was included in the refinement
which refined with an occupancy similar to that of the minor pyridine
form (0.4). Only the nondisordered positions were refined with
anisotropic thermal parameters. For refinement of ZnIIHETPP, each
group of Ca, Cb, and Cm atoms was refined with a common isotropic
temperature factor. Only the zinc, nitrogen, and side chain ethyl carbon
atoms were refined with anisotropic thermal parameters. For ZnII-
cTETPP, a second crystalline modification was found which crystallized
in the triclinic system with unit cell parameters of a ) 10.414(8) Å, b
) 13.237(22) Å, c ) 16.240(25) Å, R ) 65.95(10)°, â ) 80.38(10)°,
γ ) 81.06(10), V ) 1991(4) Å3, and Z ) 2. Due to the high esd’s
observed for the unit cell parameters, no data collection was performed.
Table 2. Soret and Long-Wavelength Q-Band Absorption Maxima
of the Porphyrins Studied in Methylene Chloride
M
a
2+ b
H2
H4
free base dication
Ni(II)
Zn(II)
Cu(II)
porphyrin
OEP
TPP
397 618 401 591 391 551 400 567
417 647 436 653 415 525 419 578
398 560
n.d. n.d.
DETPP 420a 645a 445 663 419 571 420 582 sh 417 543
tTETPP 426a 649a 451 668 423 581 424 586 sh 422 552
cTETPP 433a 672a 455 675 424 575 431 611
HETPP 444a 685a 462 683 429 585 443 625
OETPP 456a 706a 468 687 432 585 455 643
424 562
429 566
430 598
a Spectra taken in methylene chloride containing % NEt3. b Spectra
taken in methylene chloride containing % TFA.
possible via repeated column chromatography on alumina, this
process is quite laborious. More convenient and less time-
consuming was conversion of the crude mixture containing H2-
HETPP and H2OETPP to the respective FeIIICl or NiII com-
plexes. The iron(III) complexes could be purified easily by
conventional column chromatography on alumina, while pre-
parative HPLC chromatography using a silica gel column was
required for the Ni(II) complexes.
A simple test for the relative conformation of the free-base
porphyrins in solution can be performed by inspection of their
electronic absorption spectra.5c All studies on porphyrin non-
planarity have shown that increasing macrocycle distortion is
accompanied by an increasing bathochromic shift of the
absorption bands. These red shifts are due to the destabilization
of the π-system, which mainly results in an increase of the
HOMO level and smaller perturbations of the LUMO.1c Table
2 lists the main absorption maxima of the compounds studied
and clearly shows that the absorption bands are successively
red-shifted and broadened with increasing number of â-ethyl
substituents. Since the number and positions of the diethyl-
pyrrole units should correspond to the degree of conformational
distortion the following order of nonplanarity is obtained: H2-
OETPP > H2HETPP > H2cTETPP > H2tTETPP > H2DETPP
> H2TPP.
In addition, UV/vis spectroscopy provides evidence for the
importance of the individual substituent pattern. Both regio-
isomers of TETPP bear the same number and type of substit-
uents. In general, two types of steric hindrance are present in
these compounds. The meso-phenyl substituents are flanked
either by two â-hydrogen atoms (H-Ph-H), by a â-ethyl and
a â-hydrogen substituent (Et-Ph-H), or by two â-ethyl
substituents (Et-Ph-Et). The steric strain imposed on the
macrocycle by these groups follow the order Et-Ph-Et > Et-
Ph-H > H-Ph-H. Indeed, H2cTETPP, which contains one
Et-Ph-Et and two Et-Ph-H units, shows a significantly
bathochromically shifted absorption spectrum compared to H2-
tTETPP, which only has Et-Ph-H units. Similar results were
obtained for the corresponding porphyrin dications. Increasing
nonplanarity in solution is also evident from 1H-NMR spectra.
The N-H protons show increasing deshielding in the order H2-
DETPP < H2tTETPP < H2cTETPP < H2HETPP (δ ) -3.04/
-2.45, -2.60, -2.38, and -2.23 ppm, respectively).
Besides a stepwise increase in nonplanarity upon going from
TPP to OETPP, we expected to see asymmetric distortion modes
for the intervening porphyrins. Thus, in order to determine the
exact macrocycle conformations, single-crystal X-ray structure
determinations were performed for all compounds. In contrast
to our experience with some other highly substituted porphyrins,
the present compounds could be crystallized quite easily.
Figure 1 shows side views of the four new free-base
porphyrins H2DETPP, H2tTETPP, H2cTETPP, and H2HETPP
Further details of the crystal data and structure solutions and
refinements are listed in Table 1 and have been deposited with the
CCDC.
Results and Discussion
For synthesis of the desired porphyrins, the method of mixed
condensation was used. An equimolar solution of pyrrole,
diethylpyrrole, and benzaldehyde was treated with BF3‚OEt2 as
catalyst for 2 h. Subsequent oxidation of the porphyrinogens
formed in situ yielded a mixture of all six possible compounds.
The mixture was easily separated by alumina column chroma-
tography into three fractions, each containing two products.
While the fractions containing H2TPP/H2DETPP or H2tTETPP/
H2cTETPP could easily be separated by a second chromato-
graphic step using silica gel or alumina, respectively, separation
of the fraction containing H2HETPP/H2OETPP proved to be
more difficult. Although separation of these compounds is

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6109
Table 3. Macrocycle Conformations of the Porphyrins Studieda
Cb displacement, Å
pyrrole tilt, deg
quadrant
Cm displacement, Å
C5 C10 C15 C20
0.03 0.05
quadrant
∆24,b
compd
Å
av
N21 N22 N23 N24
av
av
N21 N22 N23 N24
H2OEP21
0.02
0.05
0.19
0.10
0.29
0.38
0.46
0.54
0.02
0.26
0.45
0.39
0.46
0.49
0.53
0.62
0.21
0.02
0.32
0.26
0.40
0.44
0.49
0.55
0.01
0.05
0.06
0.06
0.18
0.28
0.33
0.45
0.43
0.50
0.08
0.06 0.11
d
d
d
d
d
d
0.04
d
d
d
d
d
d
1.7
4.0
11.9 11.9
4.3 6.8
2.2
6.6
1.1
1.4
d
d
d
d
3.1
d
d
d
6.7
H2TPP, tricl22a
H2TPP, tetrag22b
H2DETPP
0.06c 0.03 0.09
0.04c 0.05 0.03
0.14
0.19
0.61
0.76
0.95
1.17
0.06
0.27
0.82
0.32
0.61
0.89
1.00
1.25
0.16
0.05
0.58
0.52
0.73
0.83
0.95
1.13
0
0.14
d
0.38
0.38
d
0.29 0.04 0.15 0.29 0.05
0.64 0.59 0.62 0.57 0.04
0.93 1.24 0.57 0.31 0.12
0.79 1.17 1.08 0.74 0.06
1.03 1.27 1.26 1.10 0.03
0.06 0.03 0.05 0.06
0.5
H2tTETPP
H2cTETPP
H2HETPP
0.01 0.05 0.05 0.06 15.0 16.3 14.1 15.9 13.7
0.18 0.03 0.04 0.20 20.4 25.1 33.7 14.8 7.8
0.05 0.01 0.08 0.10 24.0 20.3 29.0 28.6 17.9
H2OETPP10a
NiIIOEP, tricl A23b
NiIIOEP, tetrag23a
NiIIDETPP
0.07 0.05
0.04 0.01
0
d
d
0.01 31.2 26.7 34.8 33.5 29.7
d
d
0.06 0.06
0.27
d
d
d
d
0.03
0.51
1.7
16.4 16.4
1.6
1.8
d
d
d
d
d
d
0.51
d
0.88 0.81 0.79 0.81 0.28
0.34 0.30 0.24 0.23 21.0 23.5 20.9 19.2 20.3
NiIItTETPPe
0.33 0.30
0.70 0.51
d
d
d
d
0.79
0.68
0.78 0.79
0.69 0.68
d
d
d
d
25.7 26.6 24.7
26.1 27.5 24.6
d
d
d
d
NiIIcTETPP
NiIIHETPP
NiIIOETPP9
CuIITPP24
1.08 1.00 0.78 0.71 0.20
1.11 1.04 1.03 0.82 0.16
1.19 1.27 1.26 1.27 0.03
0.23 0.14 0.21 0.20 20.8 26.8 23.3 17.0 16.2
0.24 0.14 0.13 0.13 23.4 26.5 24.8 23.9 18.2
0
0.42
0.01 0.01
0.03 0.06 0.03 29.4 27.7 30.2 29.3 30.5
0.16
d
d
d
d
d
0.42
0.01
d
d
d
d
d
13.4 13.4
1.5 0.9
d
2.0
d
d
d
d
CuIIOEP25
CuIIDETPe
0.02 0.08
0.73 0.45 0.62 0.52 0.16
0.55 0.59 0.36 0.58 0.07
0.86 0.63 0.69 0.73 0.23
1.09 0.97 0.67 0.58 0.17
1.10 1.01 0.99 0.71 0.13
1.12 1.07 1.13 1.18 0.04
0.22 0.03 0.19 0.18 13.9 18.3 10.1 14.1 12.9
0.04 0.12 0.06 0.07 12.2 13.2 14.0 7.7 13.7
0.23 0.29 0.20 0.19 18.1 21.2 15.5 18.0 17.8
0.21 0.15 0.20 0.12 19.8 27.2 23.5 15.1 13.4
0.21 0.11 0.13 0.05 23.0 27.0 24.8 24.0 16.2
0.02 0.02 0.04 0.09 27.4 27.3 25.6 27.6 29.1
CuIItTETPP
CuIIcTETPP
CuIIHETPP
CuIIOETPP8
ZnIITPP(H2O)26a
ZnIITPP, tricl26b
ZnIIOEP(pyr)27
ZnIIDETPP(MeOH)
ZnIIDETPP(â-pic)
ZnIItTETPP(pyr)
ZnIIcTETPP(pyr)
ZnIIHETPP
0
d
d
d
0
d
d
0
0
d
d
d
d
d
0
0
d
d
d
0.5
2.3
d
d
4.7
0.7
0.21
0.16
0.12
0.25
0.54
0.63
0.84
0.89
1.09
0.34 0.08
0.27 0.17
0.15
0.21 0.08
0.17 0.12
6.5
4.1
3.1
9.1
7.4
6.4
3.1
4.0
3.0
0.07 0.05 0.06 0.12
0.01 0.01 0.05
0.15 0.14 0.05 0.34
0.33 0.14 0.19 0.15 15.0 10.5 16.9 18.4 14.0
0.23 0.08 0.27 0.15 16.9 20.8 24.1 7.2 15.6
0.20 0.11 0.16 22.5 27.1 25.4 24.5 13.0
0.05 0.04 0.02 0.11 22.4 21.8 28.4 21.4 17.9
0.02 0.08 0.06 28.4 26.2 28.7 31.7 26.9
0.24 0.11 0.09 0.03 0.02
0.31 0.41 0.09 0.17 0.17
0.35 0.61 0.68 0.50 0.20
0.79 0.92 0.21 0.60 0.18
1.08 1.00 0.98 0.28 0.12
0.86 1.10 0.85 0.74 0.06
1.02 1.09 1.21 1.03 0.04
0
9.3 11.5 11.1
3.0 11.4
0
ZnIIHETPP(pyr)
ZnIIOETPP(MeOH)7
0
a Numbers are given relative to the least-squares plane for the four nitrogen atoms. Numbers listed for individual quadrants give the average
values of geometrically equivalent positions in each quadrant. b Average deviation of the 24 macrocycle atoms from their least-squares plane.
c Data relative to 24 macrocycle atom plane. d Generated by symmetry operation. e Two crystallographically independent molecules.
tTETPP < H2cTETPP < H2HETPP < H2OETPP. A good
measure for the overall degree of nonplanarity in a porphyrin
is the average deviation of the 24 macrocycle atoms from their
least-squares plane. As indicated in Table 3, these ∆24 values
increase in the same order with values of 0.02, 0.10, 0.29, 0.38,
0.46, and 0.54 Å, respectively. This ordering of the porphyrins
in the solid state gives the same result as was described above
for the situation in solution on the basis of the electronic
absorption spectra. For TPP, the starting compound in the series
presented here, two different crystalline modifications are
known.22 While triclinic TPP (∆24 ) 0.05 Å) is more or less
planar,22a tetragonal TPP has a ruffled conformation with ∆24
) 0.19 Å.22b All free-base ethyl-TPP compounds presented here
exhibit saddle-distorted macrocycles, i.e. out-of-plane rotation
of the pyrrole rings with large deviations observed for the Cb-
positions while the Cm positions remain in the plane of the
molecule. Thus, triclinic H2TPP was chosen as reference
compound for the ethyl-substituted TPP’s.
A display of the skeletal deviations shows not only that the
macrocycles become progressively more distorted with increas-
ing number of â-ethyl substituents but also that the distortion
modes are asymmetric in relation to the substituent pattern
(Figure 2). In general, the largest deviations are observed for
Cb positions in quadrants of the molecule bearing â-ethyl groups.
Here two different situations have to be considered. Either
Figure 1. Side views of the molecular structures of H2OEP, H2DETPP,
H2tTETPP, H2cTETPP, H2HETPP, and H2OETPP.
and those of H2OEP21 and H2OETPP.10a Even a rudimentary
visual inspection shows that the porphyrins become progres-
sively more nonplanar in the order H2OEP < H2DETPP < H2-
(22) (a) Silvers, S. J.; Tulinsky, A. J. Am. Chem. Soc. 1967, 89, 3331. (b)
Hamor, M. J.; Hamor, T. A.; Hoard, J. L. J. Am. Chem. Soc. 1964,
86, 1938.
(21) Lauher, J. W.; Ibers, J. A. J. Am. Chem. Soc. 1973, 95, 5148.

6110 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6111
Table 4. Core Conformations of the Porphyrins Studied (Data Given in Å)
compd
M-Na av
M-N21
M-N22
M-N23
M-N24
M-Lax
∆Mb
core size av
H2OEP, tricl21
H2TPP, tricl22a
H2TPP, tetrag22b
H2DETPP
H2tTETPP
H2cTETPP
2.062
2.06
2.054
2.064
2.057
2.070
2.049
2.051
2.026
2.03
2.054
2.166
2.139
2.114
2.133
2.042
2.098
2.10
c
1.974
1.976
2.058
1.974
2.057
1.957(2)
c
1.916(6)
1.871(6)
1.887(6)
1.932(3)
1.910(3)
1.901(2)
c
1.999(3)
1.959(3)
1.977(3)
1.945(3)
1.979(5)
1.960(4)
1.991(5)
c
2.045(2)
2.062(3)
2.030(5)
2.043(4)
2.048(4)
2.071(3)
1.995(5)
2.052(3)
2.056(5)
c
c
c
c
c
c
2.062
2.06
2.054
2.064
2.057
2.070
2.049
2.051
1.958
1.929
1.922
1.896
1.894
1.923
1.921
1.906
1.981
1.998
1.989
1.999
1.984
1.975
1.980
1.978
2.043
2.037
2.043
2.052
2.043
2.048
2.045
2.026
2.039
2.048
2.135
2.139
2.094
2.142
2.034
c
1.980
1.974
2.015
1.948
2.072
c
H2HETPP
H2OETPP10a
NiIIOEP, tricl A23b
NiIIOEP, tetrag23a
NiIIDETPP
1.958(2)
1.929(3)
1.923(6)
1.893(6)
1.893(6)
1.923(4)
1.921(3)
1.906(2)
1.981(7)
1.998(3)
1.990(3)
1.999(3)
1.984(4)
1.975(5)
1.980(5)
1.977(5)
2.050(3)
2.037(3)
2.067(6)
2.062(5)
2.068(4)
2.071(3)
2.070(3)
2.028(4)
2.069(3)
2.063(5)
1.959(2)
1.929(3)
1.942(6)
1.914(6)
1.899(6)
1.930(4)
1.938(3)
1.911(2)
1.981(7)
1.996(3)
2.027(3)
2.027(3)
2.021(4)
1.989(5)
2.009(5)
1.959(5)
2.050(3)
2.029(2)
2.068(3)
2.091(5)
2.099(4)
2.094(3)
2.075(3)
2.068(4)
2.091(3)
2.069(5)
0
0
0
0.03
0
0.01
0.01
0.01
0
c
c
1.921(6)
c
c
1.907(4)
1.931(3)
1.905(2)
c
1.911(6)
c
c
1.921(3)
1.905(3)
1.906(2)
c
NiIItTETPPd
NiIIcTETPP
NiIIHETPP
NiIIOETPP9
CuIITPP24
CuIIOEP25
CuIIDETPPd
c
c
0
2.012(3)
2.014(3)
2.017(4)
1.962(5)
2.001(5)
1.970(5)
c
1.960(4)
1.976(3)
1.953(4)
1.970(5)
1.950(5)
1.990(5)
c
0.05
0.02
0.02
0.02
0.02
0
CuIItTETPP
CuIIcTETPP
CuIIHETPP
CuIIOETPP8
ZnIITPP(H2O)26a
ZnIITPP, tricl26b
ZnIIOEP(pyr)27
ZnIIDETPP(MeOH)
ZnIIDETPP(â-pic)
ZnIItTETPP(pyr)
ZnIIcTETPP(pyr)
ZnIIHETPP
2.228(12)
0.17
0
c
c
2.061(3)
2.101(5)
2.086(4)
2.108(3)
2.062(3)
2.057(4)
2.086(3)
2.072(5)
2.075(3)
2.026(5)
2.045(4)
2.034(4)
2.072(3)
1.991(4)
2.046(3)
2.051(5)
2.200(3)
2.217(5)
2.165(4)
2.182(6)
2.177(3)
0.31
0.21
0.32
0.31
0.32
0.07
0.35
0.22
ZnIIHETPP(pyr)
ZnIIOETPP(MeOH)7
2.131(3)
2.226(5)
a For the free-base porphyrins, M refers to the geometrical center of the N4 least-squares plane. b Displacement of the metal from N4 plane.
c Generated by symmetry operation. d Two crystallographically independent molecules.
diethylpyrrole ring can be situated next to a meso-phenyl which
is flanked by a â-H and a â-ethyl group (Et-Ph-H) or
alternatively it can be part of a Et-Ph-Et group. The latter
type of pyrrole ring is encountered in cTETPP and HETPP (and
OETPP), and as expected, individual pyrrole displacements in
these compounds are even larger.
H2tTETPP exhibited an almost symmetric distortion mode
with only minor differences between individual quadrantssan
indication of the extent to which steric strain can be redistrib-
uted. The fact that the distortion of â-hydrogen-substituted
pyrrole units exceeded those of the unsubstituted positions in
H2cTETPP has to be due to the different steric building blocks.
The latter has a H-Ph-H unit in the “southern” region, while
H2tTETPP contains only Et-Ph-H blocks. Similar results are
obtained if the angles formed between individual pyrrole rings
and the N4 plane are inspected (Table 3).
The possibility remained that part of the steric strain is
relieved by in-plane distortion of the macrocycle. Such effects
have been described for 2,3,5,7,8,12,13,15,17,18-decasubstituted
porphyrins and are characterized by in-plane elongation of the
porphyrin core, leading to inequivalency of different N-N
vectors.28 No evidence for this was found. In addition, for all
compounds described here, packing analyses were performed.
Generally, with increasing degree of nonplanarity, the packing
types deviated more and more from the layer-type structures
observed for planar porphyrins and came closer to the interlock-
ing fit often observed for highly nonplanar porphyrins.5-14
However, in distinction to the symmetric, dodecasubstituted
porphyrins in several cases, weak π-π aggregates were
observed for the asymmetric porphyrins described here. These
were characterized by interplanar separations between neighbor-
ing molecules in the range 3.5-4 Å and lateral shifts of the
porphyrin centers in the range 3.5-4.6 Å. According to the
classification given by Scheidt and Lee,14 these interactions fall
into the intermediate/weak category. Since this effect did not
correlate with any of the conformational parameters and
otherwise the molecules were well separated, the influence of
crystal packing forces was deemed to be low and the observed
out-of-plane displacements have to be mainly due to the steric
strain imposed by the peripheral substituents.
The local effect of macrocycle distortion is best evidenced
by the fact that individual displacements can reach those
observed in dodecasubstituted porphyrins. For example ring
II in H2cTETPP shows Cb displacements (1.24 Å) and pyrrole
tilt angles (33.7°) which are very similar to the largest ones
described for H2OETPP (1.27 Å and 34.8°).10a However, this
statement has to be viewed with some caution. Redistribution
of steric strain does occur and the macrocycle for a given
macrocycle is relatively flexible, leaving room for packing and
aggregation forces.14 This is clearly evidenced by significant
distortions for ring III in H2DETPP or the inequivalence of the
deviations observed for the pairs of pyrrole rings bearing either
â-ethyl or â-hydrogen substituents in H2cTETPP. Nevertheless,
the differences between chemically equivalent groups become
smaller with increasing overall degree of macrocycle distortion.
Structural data on the core conformation (Table 4) and the
bond lengths and angles (Table 5) show that structural differ-
ences between pyrrole rings containing N-H hydrogens and
those without are retained in the nonplanar porphyrins. This is
evidenced by longer N-Ct vector lengths and wider Ca-N-
Ca angles for N-H pyrrole rings (Ct is defined as the
geometrical center of the N4 unit). Bond lengths and bond

6112 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
Table 5. Selected Bond Lengths (Å) and Angles (deg) for the Free-Base Porphyrins Studied
quadrant H2OEP21 H2TPP, tricl22a H2TPP, tetr22b H2DETPP H2tTETPP H2cTETPP H2HETPP H2OETPPa,10a
N-Ca
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
1.364(2)
1.367(2)
b
b
1.438(2)
1.463(2)
b
b
1.373(2)
1.363(2)
b
b
1.390(2)
1.394(2)
b
b
109.6(1)
105.7(1)
b
b
107.8(1)
110.9(1)
b
b
107.4(1)
106.3(1)
b
b
125.0(1)
125.1(1)
b
b
1.376
1.365
b
1.350(7)
b
b
b
1.438(8)
b
b
b
1.362(9)
b
b
b
1.403(7)
b
b
b
108.9(4)
b
b
b
107.5(4)
b
b
b
106.9(5)
b
b
b
126.0(5)
b
b
b
1.377(5)
1.376(5)
1.373(5)
1.370(5)
1.447(5)
1.456(5)
1.430(5)
1.458(5)
1.380(5)
1.345(6)
1.357(6)
1.342(6)
1.402(5)
1.410(5)
1.397(5)
1.409(5)
110.8(3)
104.8(3)
110.8(3)
105.0(3)
106.8(3)
110.9(3)
106.3(3)
111.0(3)
107.8(3)
106.7(3)
108.4(4)
106.6(4)
124.1(3)
126.9(4)
125.8(3)
127.0(4)
126.4(3)
124.6(4)
125.6(3)
126.0(3)
129.2(3)
122.2(4)
127.9(4)
121.9(4)
1.383(9)
1.366(9)
1.377(9)
1.367(9)
1.430(10)
1.459(10)
1.441(10)
1.452(10)
1.369(10)
1.336(10)
1.370(10)
1.337(11)
1.400(10)
1.401(10)
1.401(10)
1.404(10)
109.6(6)
106.6(6)
110.4(6)
106.0(6)
106.9(6)
109.7(6)
106.6(6)
110.6(6)
108.2(6)
107.0(6)
108.1(6)
107.0(7)
122.6(6)
127.4(6)
123.2(6)
126.8(7)
125.8(7)
124.6(6)
126.0(6)
125.9(7)
130.5(7)
122.9(6)
130.2(6)
123.2(7)
1.381(5)
1.365(5)
1.379(5)
1.366(5)
1.444(5)
1.465(6)
1.427(6)
1.457(5)
1.379(6)
1.374(6)
1.354(5)
1.342(5)
1.414(6)
1.411(5)
1.405(5)
1.407(5)
110.7(3)
106.3(3)
110.4(3)
105.7(3)
106.6(3)
110.7(3)
106.1(3)
110.5(3)
108.0(3)
106.1(4)
108.6(4)
106.7(4)
123.6(3)
123.0(3)
125.6(3)
126.1(4)
124.6(4)
124.1(3)
124.3(4)
124.8(3)
129.7(4)
126.1(4)
128.1(4)
123.2(3)
1.368(6)
1.363(6)
1.369(6)
1.374(7)
1.450(7)
1.460(7)
1.446(7)
1.451(7)
1.368(7)
1.361(8)
1.375(7)
1.337(8)
1.396(7)
1.424(7)
1.400(7)
1.399(7)
111.9(4)
105.1(4)
112.4(4)
105.3(4)
105.9(4)
111.2(4)
105.5(4)
110.3(5)
108.1(5)
106.0(5)
108.2(5)
107.0(5)
123.1(5)
122.3(5)
123.1(5)
125.7(5)
124.3(5)
124.9(5)
124.1(5)
126.2(5)
130.8(5)
126.2(5)
131.4(5)
123.9(5)
1.368
1.451
1.377
1.407
b
Ca-Cb
1.428
1.455
b
b
Cb-Cb
1.355
1.347
b
b
Ca-Cm
1.400
1.400
b
b
Ca-N-Ca
N-Ca-Cb
Ca-Cb-Cb
N-Ca-Cm
Ca-Cm-Ca
Cm-Ca-Cb
109.2
106.2
b
106.1
111.0
b
107.3
110.3
b
108.7
106.9
122.4
123.8
128.8
b
108.1
106.8
b
b
126.0
126.3
b
b
127.4(1)
127.7(1)
b
b
127.3(1)
124.0(1)
b
b
125.6
125.6
b
125.2(5)
b
b
b
b
126.2
123.5
b
125.1(5)
b
b
b
b
a Average data for geometrically equivalent positions. b Generated by symmetry operation.
angles for individual quadrants of the porphyrins also give
evidence for the influence of increasing macrocycle distortion.
Ca-Cb, Cb-Cb, and Ca-Cm bonds become more elongated and
N-Ca-Cm and Ca-Cm-Ca angles become smaller, while Cm-
Ca-Cb angles are larger in nonplanar macrocycles. Although
these results agree well with those for symmetric nonplanar
porphyrins,5-13 the novel, less symmetric porphyrins presented
here give evidence for the local influence of the different
substituent patterns. Areas of the porphyrin macrocycle with
steric hindrance yield geometrical data which resemble those
of the highly nonplanar H2OETPP, while parts of the molecules
without steric strain exhibit bond lengths and angles closer to
those of their planar counterparts. In some instances, the relative
trends of individual geometrical parameters for sterically
hindered macrocycle parts even exceed those found for H2-
OETPP when compared to H2TPP or H2OEP. For example,
the Cb-Cb bond length in pyrrole N21 of H2DETPP (1.380 Å)
is considerably longer than the average for triclinic H2TPP
(1.351 Å)22a or H2OEP (1.368 Å)21 and slightly longer than the
average found in H2OETPP (1.377 Å), despite the fact that the
latter is considerably more distorted than H2DETPP. This
presents further evidence for the local influence of peripheral
steric strain.
an ordering of the metal complexes similar to that observed for
the free bases and dications on the basis of the bathochromic
shift of the absorption bands: MIIOETPP > MIIHETPP >
MIIcTETPP > MIItTETPP > MIIDETPP > MIITPP. The only
exception to this ordering was observed for the Ni(II) complexes
of cTETPP and tTETPP. Here the ordering found for the other
series was reversed and NiIItTETPP showed a more red-shifted
Q absorption band (λmax ) 581 nm) than NiIIcTETPP (λmax
)
575 nm).
The crystal structures of the nickel(II) complexes (Figure 2)
show that three of the four new porphyrins (NiIIDETPP,
NiIIcTETPP, and NiIIHETPP) exhibit saddle-distorted macro-
cycles. This is in agreement with the results for dodecasub-
stituted porphyrins with peripheral steric strain induced by
â-alkyl and meso-aryl groups, which all have been described
as saddle conformations.9 Compared to the free-base porphyrins
and to NiIIOETPP, these porphyrins showed a significant degree
of ruffling, as indicated by average Cm displacements on the
order of 0.2 Å (Table 3) and by the tilt of the pyrrole rings in
their plane (Figure 2). While saddle conformations are char-
acterized by large displacements of the Cb-position, ruffled
conformations are characterized by significant Cm displacements
and an in-plane rotation of the pyrrole rings.14
In order to study the influence of different metals on the
conformation, metal complexes with M ) Ni(II), Zn(II), and
Cu(II) were prepared via metalation with metal acetates or metal
bromides. Inspection of the absorption spectra (Table 2) showed
Ruffled conformations are often found for metalloporphyrins
with small metal ions, which tend to distort the macrocycle in
order to minimize their M-N bonds. The best known example

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6113
highly substituted porphyrins like cTETPP or HETPP, the
relative magnitudes of the differences between peripherally
sterically strained regions and those with â-hydrogen substit-
uents are similar in the free-base and nickel(II) porphyrins. A
possible explanation for this effect, which is also found for the
respective Cu(II) porphyrins (see below), might be that the less
highly substituted porphyrins can pack more closely in the
crystal and thus packing forces can exert more influence in these
compounds than in the more highly substituted porphyrins.
For a given distortion mode, e.g. saddle or ruffle, increasing
macrocycle distortion leads to shorter average M-N bond
lengths. Crystal structure analysis of the DETPP, tTETPP,
cTETPP, and HETPP metalloporphyrins presented here shows
that this is achieved in asymmetrically substituted porphyrins
mainly via shortening of the M-N bond lengths involving the
less distorted regions. M-N bond lengths to pyrrole rings
deviating strongly from the mean plane are generally longer
than those involving more planar quadrants of the macrocycle.
A typical example is NiIIcTETPP, which shows average Ni-N
bond lengths of 1.931 Å for the ethyl-substituted pyrroles
(average tilt angle against the N4 plane 25.1°) and 1.914 Å for
the hydrogen-substituted pyrroles (average tilt angle 16.6°).
Similar conclusions are possible for the ruffled NiIItTETPP,
which has an average Ni-N bond length of 1.893 Å (∆Cm
)
Figure 3. Side views of the molecular structures of one of the two
independent molecules in the structures of NiIItTETPP (top) and
NiIIcTETPP (bottom). Hydrogen atoms and disordered positions have
been omitted for clarity. Both views have the same orientation with
the N4 plane orthogonal to the plane of the paper and the macrocycle
viewed along a N-Ni-N axis.
0.68, 0.79 Å). This is shorter than the 1.929 Å found for
tetragonal NiIIOEP (∆Cm ) 0.51 Å)23a or the 1.917 Å described
for NiIITC5TPOMeP (∆Cm ) 0.60 Å).5c Interestingly, it is still
shorter than the 1.909(5) Å described for a ruffled (dodeca-
phenylporphyrinato)nickel(II) [NiIIDPP], which exhibited Cm
displacements of 0.86 Å.11c Ruffling can also be induced by
introduction of sterically demanding meso-alkyl groups.11b,15
Such compounds show structural data similar to those for
NiIItTETPP. For example, (2:3,7:8,12:13,17:18-tetracyclopen-
teno-5,10,15,20-tetra-n-pentylporphyrinato)nickel(II) has an av-
erage Ni-N bond length of 1.911 Å and Cm displacements of
0.83 Å,11b while (5,10,15,20-tetraisopropylporphyrinato)-
nickel(II) has an average Ni-N bond length of 1.896 Å and
Cm displacements of 0.74 Å.15a The shortest experimentally
determined Ni-N bond length of 1.88 Å has been described
on the basis of EXAFS data in toluene for NiIIDPP.9
of a metalloporphyrin with different conformations is NiIIOEP,23
which has been found in both planar and severely ruffled
modifications (Cm displacements of 0.51 Å).23a Similarly, (2:
3,7:8,12:13,17:18-tetracyclopenteno-5,10,15,20-tetrakis(3,4,5-tri-
methoxyphenyl)porphyrinato)nickel(II) [NiIITC5TPOMeP], a
porphyrin for which no steric strain was expected due to the
small size of the five membered cyclopenteno rings and for
which molecular mechanics calculations5c and EXAFS inves-
tigations9 had predicted a planar conformation, was found to
exhibit a ruffled conformation in the solid state due to crystal
packing forces (Cm displacements 0.60 Å).5c
As noted above, an exception to the order of nonplanarity
established for the free-base porphyrins was found for
NiIIcTETPP and NiIItTETPP. As shown in Figures 2 and 3,
this is due to the fact that NiIItTETPP, in contrast to all other
structures described in this paper, has a ruffled conformation.
The compound crystallized with two independent molecules
which are mainly differentiated by the degree of in-plane rotation
of the pyrrole rings. The degree of ruffling is severe; average
Cm displacements for both molecules are 0.68 and 0.79 Å which
is significantly more than the values described in the preceding
paragraph for NiIITC5TPOMeP and NiIIOEP.
Overall, the nickel(II) porphyrins gave results similar to those
obtained for the respective free-base porphyrins. Thus, areas
of the porphyrins with steric strain exhibited larger distortions
from planarity with associated changes in their bond lengths
and angles (Table 6). Larger differences were found if less
highly substituted nickel(II) and free-base porphyrins are
compared, e.g. DETPP. Here, the differences between regions
with peripheral steric strain and those without are much less
pronounced in the nickel(II) compound. Upon going to more
As evidenced by structural data for H2tTETPP, steric strain
is present in the tTETPP system. Thus, the observation of a
ruffled conformation for NiIItTETPP cannot be due solely to
packing forces and the possibility remains that multiple con-
formations may exist, including a yet unidentified saddle
conformation for NiIItTETPP. Such a case has been described
for NiIIDPP, where ruf, wave, and saddle conformations have
been identified in different crystalline modifications and
derivatives.11c
Overall, the structures of the Cu(II) complexes are very
similar to those of the respective Ni(II) complexes. Selected
structural data and a comparison with CuIITPP,24 CuIIOEP,25
and CuIIOETPP8 are given in Tables 3 and 4. All Cu(II)
complexes exhibited significant degrees of ruffling in addition
to the saddle distortion mode (see Figure 2 and Cm displacements
in Table 3). Individual differences are found in the degree of
macrocycle distortion, which is generally 10-30% smaller than
that found in the Ni(II) complexes. Interestingly, CuIItTETPP
did not crystallize in a completely ruffled conformation as did
NiIItTETPP but rather retained an overall saddle-shaped distor-
tion like the other compounds. On the basis of the ordering of
the UV/vis data, a similar conformation is assumed to be
(23) (a) Meyer, E. F., Jr. Acta Crystallogr. 1972, B28, 2162. (b) Cullen,
D. L.; Meyer, E. F., Jr. J. Am. Chem. Soc. 1974, 96, 2095. (c) Alden,
R. G.; Crawford, B. A.; Doolen, R.; Ondrias, M. R.; Shelnutt, J. A. J.
Am. Chem. Soc. 1989, 111, 2070. (d) Brennan, T. D.; Scheidt, W. R.;
Shelnutt, J. A. J. Am. Chem. Soc. 1988, 110, 3919.
(24) Fleischer, E. B.; Miller, C. K.; Webb, L. E. J. Am. Chem. Soc. 1964,
86, 2342.
(25) Pak, R.; Scheidt, W. R. Acta Crystallogr. 1991, C47, 431.

6114 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
Table 6. Selected Bond Lengths (Å) and Angles (deg) for the Nickel(II) Porphyrins Studied
NiIItTETPPb
quadrant NiIIOEP, tricla,23b NiIIOEP, tetr23a NiIIDETPP
mol 1
mol 2
NiIIcTETPP NiIIHETPP NiIIOETPPa,9
N-Ca
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
adj
1.376(4)
1.443(3)
1.346(2)
1.371(4)
1.386(2)
c
c
c
1.449(5)
c
c
c
1.362(5)
c
c
c
1.372(2)
c
c
c
90.0
180.0
127.4(2)
c
c
c
105.1(3)
c
c
c
110.6(2)
c
c
c
106.8(3)
c
c
c
124.0(2)
c
c
c
124.1(2)
c
c
c
1.394(9)
1.385(9)
1.396(9)
1.382(9)
1.394(10) 1.396(9)
1.381(10) 1.377(9)
1.388(5)
1.386(5)
1.383(5)
1.384(5)
1.456(6)
1.456(6)
1.432(6)
1.433(5
1.361(6)
1.353(6)
1.344(6)
1.349(6)
1.394(6)
1.396(6)
1.393(6)
1.393(5)
90.4(1)
170.0(1)
125.8(3)
126.5(3)
127.2(3)
127.3(3)
105.9(3)
105.2(3)
104.7(3)
104.9(3)
109.6(4)
110.0(4)
110.4(4)
110.3(3)
107.1(4)
107.1(4)
107.2(4)
107.1(4)
122.5(4)
121.9(4)
124.4(4)
124.0(0)
122.3(9)
121.9(4)
121.9(4)
121.6(4)
127.5(4)
127.7(4)
124.7(4)
125.1(4)
1.391(5)
1.384(6)
1.384(5)
1.382(5)
1.450(6)
1.461(6)
1.459(6)
1.435(6)
1.371(6)
1.365(6)
1.364(6)
1.352(6)
1.394(6)
1.400(6)
1.398(6)
1.387(6)
90.5(2)
169.7(2)
126.0(3)
126.3(3)
126.4(3)
126.9(3)
105.4(3)
105.4(3)
105.3(3)
105.2(3)
110.1(3)
110.2(3)
110.3(4)
110.2(4)
106.9(4)
106.7(4)
106.7(4)
107.1(4)
122.2(4)
122.2(4)
122.4(4)
124.2(4)
122.5(4)
121.6(4)
121.8(4)
122.0(4)
127.5(4)
127.1(4)
126.8(4)
123.4(4)
1.381(2)
1.451(3)
1.365(5)
1.395(2)
c
c
c
c
Ca-Cb
Cb-Cb
Ca-Cm
1.444(10) 1.450(11) 1.462(10)
1.430(10) 1.441(11) 1.446(10)
1.429(10)
1.440(10)
1.365(10) 1.378(11) 1.359(11)
1.342(10) 1.344(11) 1.344(11)
1.343(10)
1.359(10)
1.398(10) 1.401(10) 1.388(11)
1.397(10) 1.400(11) 1.383(11)
1.392(10)
1.389(10)
90.2(2)
172.9(3)
126.3(5)
126.8(5)
127.5(5)
126.5(5)
104.8(6)
104.8(6)
103.7(6)
105.3(6)
110.3(6)
110.2(6)
110.7(6)
110.3(6)
107.6(5)
107.3(6)
107.4(6)
106.4(6)
121.8(7)
123.6(6)
123.4(6)
125.4(6)
121.7(6)
122.0(6)
120.6(6)
121.7(6)
127.5(6)
125.6(6)
125.6(6)
124.4(6)
c
c
c
c
c
c
c
c
c
c
c
c
N-M-N
N-M-N
M-N-Ca
90.2(1)
180.0
128.0(2)
90.0(2)
178.7(5)
90.1(2)
175.1(4)
90.6(2)
168.7(1)
125.3(2)
opp
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
127.1(5)
126.8(5)
126.2(5)
126.5(5)
c
c
c
c
Ca-N-Ca
N-Ca-Cb
Ca-Cb-Cb
N-Ca-Cm
Ca-Cm-Ca
Cm-Ca-Cb
103.9(2)
111.6(3)
106.5(3)
124.4(3)
125.1(3)
124.1(3)
105.6(6)
106.2(6)
106.2(6)
106.2(6)
105.9(2)
109.8(1)
106.8(1)
121.3(2)
121.4(1)
128.3(1)
c
c
c
c
110.3(6)
109.5(6)
109.3(6)
109.6(6)
c
c
c
c
106.7(6)
107.5(7)
107.3(6)
107.3(6)
c
c
c
c
123.0(6)
125.5(7)
122.7(6)
124.3(7)
c
c
c
c
119.5(7)
121.6(7)
122.1(7)
120.1(7)
c
c
c
c
125.0(2)
125.9(7)
124.3(7)
127.6(7)
125.5(7)
c
c
c
c
c
c
c
a Average data for geometrically equivalent positions. b Two crystallographically independent molecules. c Generated by symmetry operation.
predominant in solution, and thus the view of CuIItTETPP given
in Figure 2 might be taken as an indication for the conformation
of a putative saddle-shaped NiIItTETPP.
methanol and the other with â-picoline as the axial ligand.
Considerable differences were observed between these two
forms (Figure 2). While the conformation of the methanol
adduct resembled that found for the corresponding free base,
the â-picoline adduct showed significantly larger deviations from
planarity for the pyrrole rings with N22 and N24 and had a
considerable degree of ruffling mixed into the conformation.
Since neither methanol nor â-picoline is a sterically demanding
axial ligand, the differences between both structures may be
taken as a measure of the flexibility inherent in the DETPP
macrocycle. Similar results were observed for the ZnII(pyridine)
complexes of tTETTP and cTETPP. Notably, ZnIItTETPP(pyr)
exhibited the only â-ethyl-substituted pyrrole ring (N21) in the
present series, which deviated less from the mean plane than a
â-H-substituted pyrrole (e.g., N22). However, the axial pyridine
was severely disordered, and thus results for this compound have
to be interpreted with some caution.
The zinc(II) porphyrins again gave results similar to those
described for the free bases or Ni(II) or Cu(II) complexes.
Selected structural data are compiled in Tables 3, 4, and 7 and
compared with data for ZnIITPP,26 ZnIIOEP(pyr),27 and ZnII-
OETPP(MeOH).7 However, zinc(II) has the propensity to form
five-coordinated species with donor molecules, and depending
on the crystallization conditions, different axial ligands are
present in the individual compounds. Thus, two crystal
structures were obtained for ZnIIDETPP, one with an axial
(26) (a) Golder, A. J.; Povey, D. C.; Silver, J.; Jassim, Q. A. A. Acta
Crystallogr. 1990, C46, 1210. (b) Scheidt, W. R.; Mondal, J. U.;
Eigenbrot, C. W.; Adler, A.; Radonovich, L. J.; Hoard, J. L. Inorg.
Chem. 1986, 25, 795.
(27) Cullen, D. L.; Meyer, E. F., Jr. Acta Crystallogr. 1976, B32, 2259.
(28) Medforth, C. J.; Senge, M. O.; Forsyth, T. P.; Hobbs, J. D.; Shelnutt,
J. A.; Smith, K. M. Inorg. Chem. 1994, 33, 3865. Senge, M. O.;
Medforth, C. J.; Forsyth, T. P.; Lee, D. A.; Olmstead, M. M.; Jentzen,
W.; Pandey, R. K.; Shelnutt, J. A.; Smith, K. M. Inorg. Chem. 1997,
36, 1149.
ZnIIHETPP could be crystallized both as the four-coordinate
compound ZnIIHETPP without any axial ligand and as the five-
coordinate complex ZnIIHETPP(pyr) with an axial pyridine.

Nonplanar Tetraphenylporphyrins
Inorganic Chemistry, Vol. 36, No. 26, 1997 6115
Table 7. Selected Bond Lengths (Å) and Angles (deg) for the Zinc(II) Porphyrins
ZnIIOEP ZnIITPP, ZnIIDETPP ZnIIDETPP ZnIItTETPP ZnIIcTETPP
ZnIIHETPP ZnIIOETPP
quadrant (pyr)a,27
tricla,26b
(MeOH)
(â-pic)
(pyr)
(pyr)
ZnIIHETPP
(pyr)
(MeOH)a,7
1.371(4)
N-Ca
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
adj
1.366(1)
1.452(6)
1.353(5)
1.390(6)
88.8(1)
1.376(2)
1.376(8)
1.370(8)
1.371(8)
1.373(8)
1.465(9)
1.434(9)
1.442(9)
1.446(9)
1.369(9)
1.345(9)
1.343(9)
1.346(9)
1.413(9)
1.418(9)
1.403(9)
1.401(9)
89.4(2)
1.377(6)
1.372(6)
1.370(6)
1.377(6)
1.458(6)
1.434(7)
1.443(7)
1.431(7)
1.364(7)
1.341(7)
1.343(7)
1.332(7)
1.406(6)
1.407(7)
1.405(7)
1.412(7)
88.6(2)
1.376(5)
1.377(5)
1.373(5)
1.370(5)
1.462(6)
1.442(6)
1.462(6)
1.445(6)
1.364(6)
1.352(6)
1.367(6)
1.349(6)
1.410(6)
1.405(6)
1.409(6)
1.405(6)
88.7(1)
1.377(5)
1.377(4)
1.373(5)
1.374(5)
1.451(5)
1.467(5)
1.444(5)
1.445(5)
1.366(5)
1.365(5)
1.357(5)
1.349(5)
1.418(5)
1.414(5)
1.408(5)
1.404(5)
88.7(1)
1.376(7)
1.382(7)
1.375(7)
1.381(7)
1.465(8)
1.453(9)
1.468(6)
1.438(7)
1.379(8)
1.384(7)
1.364(8)
1.366(7)
1.412(8)
1.415(7)
1.405(7)
1.408(7)
90.1(2)
1.370(4)
1.378(4)
1.371(4)
1.379(4)
1.458(5)
1.460(5)
1.464(5)
1.446(5)
1.370(5)
1.371(5)
1.370(5)
1.351(5)
1.410(5)
1.414(5)
1.414(5)
1.407(5)
88.4(1)
b
b
Ca-Cb
Cb-Cb
Ca-Cm
1.440(3)
1.461(2)
1.370(7)
1.416(3)
b
b
1.349(3)
b
b
1.400(3)
b
b
N-M-N
N-M-N
M-N-Ca
90.0(1)
89.4(4)
opp
163.0(16) 180.0(1)
168.5(2)
126.7(4)
126.5(4)
126.6(4)
126.5(4)
106.7(5)
106.3(5)
106.6(5)
106.7(5)
110.0(5)
109.7(5)
109.4(5)
109.4(6)
106.2(6)
107.2(6)
107.3(6)
107.2(6)
123.6(6)
126.4(6)
125.1(6)
126.5(6)
125.1(6)
125.5(6)
124.8(6)
127.2(6)
126.4(6)
123.8(6)
125.5(6)
124.0(6)
162.0(2)
125.1(3)
126.7(3)
126.1(3)
126.9(3)
107.0(4)
106.5(4)
106.7(4)
106.2(4)
109.4(4)
109.3(4)
109.4(4)
109.2(4)
106.9(4)
107.4(4)
107.3(4)
107.7(4)
123.4(4)
126.1(4)
125.0(4)
125.8(4)
125.3(4)
124.9(4)
125.5(4)
125.7(4)
127.1(4)
124.6(4)
125.5(4)
124.9(4)
162.7(1)
125.3(3)
126.3(3)
123.8(3)
126.4(3)
107.2(3)
107.2(3)
107.0(3)
107.2(3)
109.4(4)
108.9(4)
109.7(4)
109.2(4)
106.9(4)
107.5(4)
106.7(4)
107.3(4)
123.2(4)
126.1(4)
123.3(4)
126.2(4)
125.1(4)
125.3(4)
124.9(4)
126.4(4)
127.4(4)
125.0(4)
127.1(4)
124.6(4)
162.1(1)
123.2(2)
126.0(2)
126.1(2)
126.5(2)
106.8(3)
106.9(3)
106.7(3)
107.0(3)
109.5(3)
109.7(3)
109.6(3)
109.1(3)
106.9(3)
106.8(3)
107.0(3)
107.3(4)
122.6(3)
123.6(3)
124.7(3)
125.8(3)
126.4(3)
125.1(3)
124.8(4)
124.6(3)
127.8(3)
126.7(3)
125.4(4)
125.0(4)
174.7(2)
124.2(3)
124.6(3)
124.8(4)
126.6(4)
107.6(4)
106.6(5)
107.8(4)
106.1(4)
109.4(5)
109.8(4)
108.9(5)
109.8(4)
106.7(5)
106.7(6)
107.0(4)
107.0(4)
123.1(5)
122.3(5)
123.2(4)
124.6(4)
124.9(4)
124.9(5)
124.7(4)
123.8(5)
127.5(5)
127.6(5)
127.9(5)
125.3(5)
160.4(1)
123.0(2)
125.5(2)
122.8(2)
126.5(2)
107.1(3)
107.3(3)
107.4(3)
106.8(3)
109.6(3)
109.3(3)
109.4(3)
109.2(3)
106.6(3)
106.9(3)
106.7(3)
107.4(3)
121.9(3)
123.2(3)
122.5(3)
125.7(3)
125.3(3)
125.1(3)
124.3(3)
124.7(3)
128.3(3)
127.5(3)
128.1(3)
125.0(3)
167.8(4)
122.9(6)
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
N21
N22
N23
N24
126.7(3)
106.4(5)
110.1(4)
106.7(2)
124.3(5)
127.9(3)
125.5(3)
126.4(1)
b
b
Ca-N-Ca
N-Ca-Cb
Ca-Cb-Cb
N-Ca-Cm
Ca-Cm-Ca
Cm-Ca-Cb
106.6(2)
107.7(5)
109.2(3)
106.8(2)
122.4(2)
124.4(4)
128.2(2)
b
b
109.4(2)
b
b
107.4(2)
b
b
125.9(2)
b
b
124.8(2)
b
b
124.6(2)
b
b
a Average values for geometrically equivalent positions. b Generated by symmetry operation.
Differences between both compounds in bond lengths and angles
for the metal centers are typical for the four- and five-
coordinated zinc(II) porphyrins. The four-coordinated complex
showed slightly larger overall deviations from planarity and
exhibited more pronounced differences between substituted and
unsubstituted pyrrole rings. The differences between the four-
and five-coordinated ZnIIHETPP were considerably smaller than
those between the two ZnIIDETPP structures. Displacements
of the zinc(II) center from the N4 plane and structural data for
the axial ligands of all five-coordinated porphyrins (Table 4)
were comparable to those found for other five-coordinated
zinc(II) porphyrins.14
For symmetric, highly nonplanar metalloporphyrins, it has
been established that the size of the central metal is inversely
correlated to the degree of macrocycle distortion.8,12b Thus, for
a given macrocycle system, the overall degree of nonplanarity
should decrease in the order Ni(II) > Cu(II) > Zn(II). Table 3
shows that this order is retained at every level of â-ethyl
substitution, i.e. at every level of inherent steric strain. For
example, the ∆24 values are 0.62, 0.55, and 0.50 Å for
NiIIOETPP, CuIIOETPP, and ZnIIOETPP, respectively.
A
similar ordering of 0.49, 0.44, and 0.33 Å for M ) Ni, Cu, and
Zn, respectively, is observed for MIIcTETPP. This effect is
retained when individual quadrants of the porphyrin system are
inspected, and all data indicate that, with respect to structural
data like out-of-plane displacements or changes in bond lengths
and angles,8 metal effects in asymmetric saddle-distorted
porphyrins are similar to those found for symmetric porphyrins.
In addition to asymmetric distortion modes being induced
by the peripheral substituent pattern, some degree of asymmetry
is also induced by the axial ligand. In all five-coordinated
species described here, the degree of macrocycle distortion was
less for the macrocycle side facing the axial ligand than for
other. This can be exemplified by comparing the N21 and N23
quadrants (which face toward the axial ligand) with those of
N22 and N24 (which point away from the axial ligand) in Table
3.
Conclusions
The data presented here indicate that mixed condensation of
pyrrole, diethylpyrrole, and benzaldehyde yields a series of
porphyrins which show successively more nonplanar macro-

6116 Inorganic Chemistry, Vol. 36, No. 26, 1997
Senge and Kalisch
cycles in the order TPP < DETPP < tTETPP < cTETPP <
HETPP < OETPP. Crystal structures reveal that the increasing
steric strain imposed on the macrocycle by introduction of
successively more â-ethyl groups remains to some extent
localized in the respective regions of the porphyrin macrocycle.
Thus, asymmetric saddle-shaped distortions of the macrocycle
are observed for most compounds. Observation of the ruffled
NiIItTETPP is another example of the inherent flexibility of the
porphyrin macrocycle. Preliminary data29 show this series to
be an excellent candidate for further spectroscopic and photo-
physical studies, which will be reported in due course.
chungsgemeinschaft (Se543/2-4 and Heisenberg-Stipendium
Se543/3-1). We are indebted to Prof. Smith for his continuing
support and for providing instrument time at the UC Davis
crystallographic facility and to Drs. K. M. Barkigia and J. Fajer
(Brookhaven National Laboratory) for providing the crystal-
lographic coordinates for H2OETPP.
Supporting Information Available: Figures showing the atom
numbering, thermal ellipsoid plots, and deviations of the macrocycle
atoms from planarity for all compounds, selected packing plots and
side views of individual molecules, and tables listing the core size,
bond lengths, and bond angles for the Cu(II) porphyrins, phenyl tilt
angles, and packing analyses (37 pages). Ordering information is given
on any current masthead page. The results of the crystal structure
determinations have been deposited with the CCDC.
Acknowledgment. This work was supported by grants from
the Fonds der Chemischen Industrie and the Deutsche Fors-
(29) Bu¨chner, M.; Ro¨der, B. Personal communication.
IC970765G