Novel core-modified expanded porphyrins with meso-Ary1 substituents: Synthesis, spectral and structural characterization

Article abstract of DOI:10.1021/ja991472k

The synthesis, spectral and structural characterization of meso-aryl sapphyrins and rubyrins containing heteroatoms such as S, O, Se in addition to pyrrole nitrogens are reported. The synthesis of the desired expanded porphyrins has been achieved using a

Full text of DOI:10.1021/ja991472k

J. Am. Chem. Soc. 1999, 121, 9053-9068
9053
Novel Core-Modified Expanded Porphyrins with meso-Aryl
Substituents: Synthesis, Spectral and Structural Characterization
Seenichamy Jeyaprakash Narayanan,† Bashyam Sridevi,† Tavarekere K. Chandrashekar,*,†
Ashwani Vij,‡ and Raja Roy§
Contribution from the Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India,
Single-Crystal Diffraction Laboratory, UniVersity of Idaho, Moscow, Idaho 83843, andNMR DiVision,
Central Drug Research Institute, Lucknow, India
ReceiVed May 4, 1999
Abstract: The synthesis, spectral and structural characterization of meso-aryl sapphyrins and rubyrins containing
heteroatoms such as S, O, Se in addition to pyrrole nitrogens are reported. The synthesis of the desired expanded
porphyrins has been achieved using a single precursor, the modified tripyrranes containing heteroatoms, through
an unprecedented oxidative coupling reaction in moderately good yields. The product distribution and the
isolated yields were found to be dependent on the nature of the acid catalyst and its concentration. Use of 0.1
equiv of acid exclusively gave 26π rubyrins while a higher concentration of acid gave a mixture of 18π
porphyrin, 22π sapphyrin, and 26π rubyrin. Two additional products, 22π oxasmaragdyrin and 18π oxacorrole,
were isolated in the reaction of oxatripyrrane. All of the sapphyrins and rubyrins exhibit well-defined intense
Soret and Q-bands in the visible region, and the intensity and the position of the absorption maxima were
dependent on the number and the nature of the heteroatoms present in the cavity. The solid-state structures of
sapphyrins 8 and 9 show small deviations from planarity with formation of supramolecular ladders stabilized
by weak C-H‚‚‚S, C-H‚‚‚Se, and C-H‚‚‚N hydrogen bonds. 1H NMR studies reveal retainment of
supramolecular arrays in solution. The TFA adduct of 8 shows unusual binding in which both the hydroxyl
oxygen and the carbonyl oxygen participate, which is reminiscent of metal carboxylate binding and in total
1
contrast to that observed for â-substituted sapphyrins. H NMR studies on rubyrins indicate rapid rotation of
heterocyclic rings at room temperature, and protonation leads to a decrease in rate of rotation at room temperature.
1H NMR spectra of 10 and 17 in its free base form recorded at -50 °C reveal that the heterocyclic rings are
inverted and protonation leads to dramatic ring flipping. However, 11 shows normal structure in the solution.
The single-crystal X-ray structures of 10, 11, and 17 show that the heterocyclic rings, thiophene in 10,
selenophene in 11, and furan and thiophene in 17, are inverted in the solid state.
Introduction
neutral substrates,5 and media chemical sensors6 has led to a
flurry of research activity on their synthesis, characterization,
structure, and spectroscopic and electrochemical properties.5
They are also of interest in terms of aromaticity in large
conjugated cyclic systems7 and the range of coordination
environment available for transition metal cations.2a,3a,4,8 Even
though the pioneering work in the sixties by Woodward9a and
Johnson9b established the existence of expanded porphyrins, it
is only in the late eighties and early nineties that the chemistry
of expanded porphyrins has been exploited as a result of the
advances in the syntheses of key precursors such as dipyr-
romethanes10 and tripyrranes11,12 required for the construction
of the expanded porphyrin skeleton. A variety of expanded
The recent realization that expanded porphyrins1 have diverse
applications as sensitizers for PDT,2 MRI contrasting agents,3
multimetallic chelates for catalysis,4 receptors for anions and
* E-mail: tkc@iitk.ac.in. FAX: 91-512-597436/590260/590007.
† Indian Institute of Technology.
‡ University of Idaho.
§ Central Drug Research Institute.
(1) (a) Sessler, J. L.; Weghorn, S. J. Expanded, Contracted & Isomeric
Porphyrins, Tetrahedron Organic Chemistry Series, Vol. 15; Pergamon:
New York, 1997. (b) Jasat, A.; Dolphin, D. Chem. ReV. 1997, 97, 2267-
2340.
(2) (a) Sessler, J. L.; Hemmi, G.; Mody, T. D.; Murai, T.; Burrell, A.
K.; Young, S. W. Acc. Chem. Res. 1994, 27, 43-50. (b) Maiya, B. G.;
Cyr, M.; Harriman, A.; Sessler, J. L. J. Phys. Chem. 1990, 94, 3597-3601.
(c) Franck, B.; Nonn, A. Angew. Chem. Int. Ed. Engl. 1995, 34, 1795-
1811. (d) Franck, B.; Fulling, M.; Gossmann, G.; Mertes, H.; Schroder, D.
Proc. SPIE-Int. Soc. Opt. Eng. 1988, 997, 107-112. (e) Shiau, F.-Y.;
Liddell, P. A.; Vicente, G. H.; Ramana, N. V.; Ramachandran, K.; Lee,
S.-J.; Pandey, R. K.; Dougherty, T. J.; Smith, K. M. SPIE Future Dir. Appl.
Photodyn. Ther. 1989, 6, 71-86. (f) Judy, M. L.; Matthews, J. L.; Newman,
J. T.; Skiles, H.; Boriack, R.; Cyr, M.; Maiya, B, G.; Sessler, J. L.
Photochem. Photobiol. 1991, 53, 101-107. (g) Sessler, J. L.; Hemmi, G.;
Maiya, B. G.; Harriman, A.; Judy, M. L.; Boriak, R.; Matthews, J. L.;
Ehrenberg, B.; Malik, Z.; Nitzan, Y.; Ruck, A. Proc. SPIE-Int. Soc. Opt.
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(4) Burrell, A. K.; Sessler, J. L.; Cyr, M. J.; McGhee, E.; Ibers, J. A.
Angew. Chem., Int. Ed. Engl. 1991, 30, 91-93.
(5) (a) Sessler, J. L.; Andrievsky, A.; Genge, J. W. AdV. Supramol. Chem.
1997, 4, 97-142. (b) Sessler, J. L.; Burrell, A. K.; Furuta, H.; Hemmi, G.
W.; Iverson, B. L.; Kral, V.; Magda, D. J.; Mody, T. D.; Shreder, K.; Smith,
D.; Weghorn, S. J. Transition Met. Supramol. Chem. 1994, 391-408. (c)
Sessler, J. L.; Sansom, P. I.; Andrievsky, A.; Kral, V. In Supramolecular
Chemistry of Anions; Bianchi, A., James, K. B., Espana, E. G., Eds.; Wiley-
VCH: New York,1997; pp 355-419. (d) Shionoya, M.; Furuta, H.; Lynch,
V.; Harriman, A.; Sessler, J. L. J. Am. Chem. Soc. 1992, 114, 5714-5722.
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10.1021/ja991472k CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/21/1999

9054 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
porphyrins with varying degrees of ring size, such as sapphy-
rins,9,12 pentaphyrins,13 hexaphyrins,14 rosarins,15 rubyrins,16
octaphyrins,17 turcasarins,18 porphocyanines19 etc., have been
synthesized, and anion binding,5 metal chelation,8,4,2a,3a and
electrochemical5d,20 and photochemical20,21,2b properties of some
of them have been evaluated.
Core modification by the replacement of one or more pyrrolic
units by other heterocycles such as furan, thiophene, and
selenophene leads to a new class of expanded porphyrins.22
Introduction of heteroatoms into the core leads to changes in
the cavity size and electronic structure, thereby altering the
optical, electrochemical, and photochemical properties and could
be anticipated to generate interdisciplinary interest. A perusal
of literature reveals only limited reports on the synthesis and
characterization of core-modified expanded porphyrins. Johnson
and co-workers9b reported the first synthesis of furan- and
thiophene-containing sapphyrins. Later Sessler and co-workers23
have reported a series of â-substituted sapphyrins containing
one or more heteroatoms. Ibers and co-workers24 have reported
the synthesis of oxabronzaphyrin, thiaozaphyrin, and a thiophene-
containing porphycene-like 26π macrocycle by McMurray
coupling of appropriate dialdehydes. Cava et al.25 have synthe-
sized thiophene- and furan-containing annulenes, and Vogel and
co-workers26 have recently reported the synthesis of sulfur- and
selenium-containing pentaphyrins. There are few reports on
furan-containing 22π and 26π expanded macrocycles.27 Very
recently Lash and co-workers28 reported the synthesis of
carbasapphyrins by a [4 + 1] reaction of tetrapyrrole with
dialdehyde. Interestingly, in most of the above examples, the
expanded porphyrins have â-pyrrole substituents but free meso
carbon bridges.
Surprisingly, reports on the synthesis of expanded porphyrins
bearing meso-aryl substituents are very few and have appeared
very recently. Latos-Grazynski and co-workers29 were the first
to isolate N-5 meso-aryl sapphyrin as a byproduct in Rothemund
reaction in 1.1% yield. Later, Dolphin and co-workers5b
described a rational synthesis of N-5 meso-aryl sapphyrins using
tripyrranes in about 30% yield. Synthesis of diaryl sapphyrins
in 9.5% yield was reported by Sessler and co-workers30a under
Lindsey conditions30b using bipyrrole dialdehyde, pyrrole, and
benzaldehyde. We have been interested in the synthesis of core-
modified expanded porphyrins, and recent work from this
laboratory has described the synthesis of a series of heteroatom
sapphyrins and rubyrins in moderately good yields.31 Most of
the synthetic methodology described above require at least two
sensitive precursors, which involves a multistep synthesis before
the final condensation step, thus restricting the yield of the final
product. Furthermore, development of easy and efficient meth-
odology to synthesize the expanded porphyrins in multigram
quantities is still a synthetic challenge to exploit their diverse
applications. In this paper, we wish to report the synthesis,
characterization, and X-ray crystal structures of a series of 22π
sapphyrins and 26π rubyrins using a single precursor by an
unprecedented oxidative coupling reaction. It has been shown
that by choosing appropriate reaction conditions, it is possible
to control the product distribution and yield. Furthermore, the
structure of sapphyrins reveals the formation of supramolecular
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NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9055
Scheme 1. Synthesis of Core-Modified Macrocycles Containing Sulfur and Selenium
ladders stabilized by weak C-H‚‚‚S and C-H‚‚‚Se hydrogen-
bonding interactions, and such interactions are disrupted upon
protonation with TFA. The structure of the TFA adducts indicate
unusual binding in which both the carboxy oxygen and the
hydroxy oxygen bind through H-bonding with the protons of
the pyrrole nitrogens. The rubyrins also show unusual structures
in solid state where the two heterocyclic rings which are linked
to bipyrrole units are inverted, in contrast to a â-substituted
structure of N-6 rubyrin hydrochloride salt.16 A preliminary
report on this work has appeared recently.32
and 10 (Scheme 1). Change of acid from TFA to TsOH also
gave the same products, and the product distribution and yields
Results and Discussion
were found to be dependent on the concentration of the acid
catalyst. For example, reaction of 5 at 0.1 equiv of TFA
exclusively gave 11 in 10.6% yield, whereas reaction at 2 equiv
of TFA gave 9 (9.2%), 11 (18.3%), and 7 (1%). Chart 1A
summarizes the isolated yields of various products under
different acid concentrations. In general, in reaction of tri-
pyrranes containing S or Se, at 0.1 equiv of TFA, only 26π
rubyrins were formed, whereas at higher concentrations of TFA
both rubyrins and sapphyrins were formed in addition to 18π
modified porphyrins. The formation of rubyrins at lower
concentration clearly suggests an unprecedented self-coupling
of the tripyrranes, with the formation of two pyrrole-pyrrole
links at the final condensation step.
In contrast, oxatripyrrane 12 gave different products at
different concentrations of TFA (Scheme 2). Compound 13 was
isolated as the sole product (3.5%) in addition to some polymeric
materials at 0.1 equiv of TFA, whereas at higher concentrations
of TFA, in addition to 15 and 16, the ring-contracted oxacorrole
14 was also isolated (Chart 1B). Trace amounts of O2TPP were
also formed at higher concentrations. Compound 13 was found
to be relatively stable for extended periods under nitrogen and
vacuum without any noticeable decomposition.
Irrespective of the nature of the expanded porphyrin, the
currently available methods make use of an acid-catalyzed
[3 + 2],9,12 [4 + 2],16 [3 + 3],11,8d or [4 + 1]28 condensation
between the appropriate precursors, tripyrranes, terpyrranes,
tetrapyrranes, and the diformylbipyrroles, or the acid-catalyzed
cyclo condensation of 2-hydroxy-methyl pyrroles and their
analogues.33,7 More recently Smith and co-workers34a synthe-
sized sapphyrins by an acid-catalyzed condensation of a,c-
biladienes with pyrrole-2-carboxaldehyde. Recent work from
this laboratory made use of the reaction of bithiophene or bifuran
diols with either pyrrole or dipyrromethane to synthesize core-
modified sapphyrins and rubyrins in moderately good yields.31
In an attempt to synthesize 1 or 2 through an acid-catalyzed
[3 + 1] condensation of 4 or 12 with 3 and subsequent oxidation
with chloranil, we were surprised to discover the formation of
18π X2TPP, 22π sapphyrin, and 26π rubyrin in the reaction
mixture. Subsequent reaction of 4 under identical conditions
without the addition of 3 also resulted in the formation of 6, 8,
(32) Narayanan, S. J.; Sridevi, B.; Chandrashekar, T. K.; Vij, A.; Roy,
R. Angew. Chem., Int. Ed. Engl. 1998, 37, 3394-3397.
(33) Gosmann, M.; Franck, B. Angew. Chem., Int. Ed. Engl. 1986, 25,
1100-1101.
(34) (a) Paolesse, R.; Licoccia, S.; Spagnoli, M.; Boschi, T.; Khoury, R.
G.; Smith, K. M. J. Org. Chem. 1997, 62, 5133-5137. (b) Licoccia, S.;
Vona, M. L.; Paolesse, R. J. Org. Chem. 1998, 63, 3190-3195.
The observation that the rubyrins are exclusively formed at
low concentrations of TFA led us to attempt a mixed condensa-
tion of two different tripyrranes to get the rubyrins with two

9056 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
Scheme 2. Synthesis of Core-Modified Macrocycles Containing Furan
different heteroatoms (Scheme 3). Thus, condensation of 5 and
12 at 0.1 equiv of TFA followed by oxidation gave 17 in 25%
yield in addition to 10 (2.8% yield).
method of making rubyrin is easy and efficient relative to the
literature method16 in which at least two precursors involving
multistep syntheses are required before the final condensation
step. Also, in Sessler’s method,12,30 the precursors contained
preformed pyrrole-pyrrole links, whereas in the present method,
this pyrrole-pyrrole link is formed at the last stage, as is the
case for the corroles and sapphyrins reported by Smith et al.34
The formation of sapphyrins and porphyrins in the reaction
at higher concentrations of acid catalyst require fragmentaion
of the tripyrranes followed by condensation of the fragmented
products.35 Spectrophotometric and TLC analysis of the reaction
mixtures provides satisfactory evidence for the fragmentation.
Specifically, reaction of oxatripyrrane with 5 equiv of TFA
resulted in the appearance of weak band at 485 nm within 10
The sole formation of rubyrins at lower TFA concentrations
indicates an R-R self-coupling of the tripyrranes with the
formation of two direct pyrrole-pyrrole links to form a
rubyrinogen type intermediate,29 which on subsequent oxidation
with chloranil yields the 26π macrocycle (Scheme 4). The
protonation of tripyrrane leads to the two intermediates I and II
in which protonation occurs at R and â positions, respectively.
We choose to prefer the reaction of intermediate II (being the
active species) through an intermolecular electrophilic attack
to form intermediate III.34b Further rearrangement of III followed
by oxidation of chloranil results in the formation of rubyrins.
Attempts to isolate these intermediates proved futile as a result
of its instability toward oxidation to the aromatic congener. This
(35) Lash, T. D.; Chaney, S. T.; Richter, D. T. J. Org. Chem. 1998, 63,
9076-9088 and references therein.

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9057
Chart 1. Graphical Representation for the Yields of Macrocycles Obtained in Coupling Reactions: (A) Yield Data for Sulfur-
and Selenium-Containing Macrocycles and (B) Yield Data for Oxygen-Containing Macrocycles
Scheme 3. Synthesis of Rubyrin Having Oxygen and Sulfur
in the Core
min of addition. We attribute this to the formation of an
uncyclized conjugated macrocycle. Addition of chloranil resulted
in the appearance of intense bands around 450-500 nm and
weak bands in the range of 600-900 nm, suggesting the
formation of the expanded porphyrins. Furthermore, the TLC
analysis of tripyrrane after addition of TFA reveals additional
purple to red colored spots above and below the spot of
tripyrrane, and the intensity of the spots depends on the acid
concentration present at that time. Addition of chloranil results
in complete disappearance of the tripyrrane spot with new dark
spots suggesting the formation of macrocycles. The tripyrrane
fragments undergo acid-catalyzed cyclization to give sapphyrins
and porphyrins. Very recently, Lash and co-workers35 have
reported that the â-substituted tripyrranes undergo fragmentation
in the presence of acid catalyst and suggested the formation of
pyrrole and dipyrromethane in the reaction mixture. The possible
fragmented products in modified tripyrranes reported here could
be diol, heteroatom-containing dipyrromethane, and pyrrole in
addition to the unfragmented tripyrrane.35 If this is true, then
one would anticipate that the reaction of pyrrole and diols
containing heteroatoms under appropriate conditions should give
a mixture of expanded porphyrins. Indeed, independent work
from this laboratory31c and from the laboratory of Latos
Grazynski36 has shown that it is possible to synthesize expanded
porphyrins by simple reaction of diols and pyrrole. The
formation of 13 and 1437 from the reaction of oxatripyrrane is
interesting considering the fact that smaragdyrins are reported
min of addition of TFA. The intensity was found to be increasing
with time, and the maximum absorption was attained after 75
(36) Rachlewicz, K.; Sprutta, N.; Chmielewski, P. J.; Latos-Grazynski,
L. J. Chem. Soc., Perkin Trans 2 1998, 969-975.

9058 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
Scheme 4. Possible Mechanism for the Formation of Rubyrins
to be highly unstable toward acid and light. However, to our
surprise, 13 is very stable and even forms metal complexes with
transition metals. The preliminary X-ray structure of the Rh(I)
complex of 13 indicates that only one imino and one amino
nitrogen participate in coordination with the metal. Even 14 form
stable metal complexes with Ni(II), Cu(II), Co(II), and Rh(I).38
The disadvantage of the methodology described here is the
formation of a mixture of products in the reaction. Fortunately,
the ease of separation of the products due to their differing
polarity, moderately good yields, and the easy synthesis of the
only precursor in yields more than 60% makes the methodology
efficient and effective.
Spectral Characterization. The new expanded porphyrins
were characterized by FAB-MS, UV-vis, proton 1D and 2D
NMR, and single-crystal X-ray crystallography. FAB-MS
conforms to the proposed composition. The UV-vis spectra
show an intense Soret-like band in the region 440-550 nm with
ꢀ values of the order 105 mol-1 cm-1 and Q-type absorptions
in the region of 550-1100 nm. Representative UV-vis spectra
of the free base of 9 and the protonated derivative of 16 shown
in Figure 1a and 1b, respectively, clearly establish the porphy-
rinic nature of the macrocycles.22b The gradual red shift of the
absorption bands and the linear relationship (Figure 1c) between
the number of π electrons and the wavelength of the most
intense absorption band (Soret) are consistent with the increased
delocalization pathway on the expansion of the ring.2c
A
comparison of ꢀ values for the dications described here with
those reported by Franck and co-workers shows that the ꢀ values
are smaller by an order of 10 relative to those of the 22π and
26π macrocycles of Franck et al.2c
The aromatic nature of the macrocycles was established from
the observed ∆δ values2c (the difference in chemical shift of
the inner NH protons and the outer ring protons in the 1H NMR
spectrum), which is a measure of the size of the ring current.
The ∆δ values vary in the range 11.78-14.87 for the various
macrocycles reported in this work, and they compare well to
those observed for N-5 meso-aryl sapphyrin (14.8)12 and N-6
rubyrin (16.5).16 However, these values are much smaller than
those observed for 22π [20.2 (from inner CH and outer CH)
and 19.39 (from inner NH and outer CH)] and 26π [24.1 (from
inner CH and outer CH) and 20.12 (from inner NH and outer
CH)] macrocycles of Franck2c as a result of the nonplanar
structure of macrocycles (vide infra).
(37) X-ray structures of both 13 and 14 have been solved. 13 shows a
nonplanar structure (N2 -0.0171, N3 -0.0041, N1 0.0145, N4 0.0120 Å)
with a P1 space group. There are two crystallographically independent
molecules in the unit cell. 14 shows a nearly planar structure (N1 0.0155,
N2 -0.0039, N3 -0.0046, O1 -0.0051 Å) with small deviations. The
structural details will be published separately.
(38) Compound 14 behaves differently with respect to coordination
towards transition metals. For example, the X-ray structure of the Ni(II)
complex shows coordination of all three pyrrole nitrogens and the furan
oxygen, while in the Rh(I) complex, only one amino and one imino nitrogen
are coordinated. The details of the structure will be published separately.
N-H Tautomerism in Sapphyrins. Unlike â-substituted
sapphyrins, the meso-aryl sapphyrins exhibit two types of
geometry referred to as planar and inverted.39 In the planar
geometry, the pyrrole nitrogen atom in the ring opposite to the

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9059
Figure 2. 1H NMR spectra of 9 at variable temperatures in CD2Cl2.
aryl sapphyrin 8, 9 and 15 do not show any ring flipping upon
protonation.
The 1H NMR spectra of 8 and 9 reveal that the NH
tautomerism in 8 is rapid relative to that in 9 at room
temperature, resulting in the appearance of a broad signal at
-4.4 ppm for 9 while no signal is observed for 8 for the inner
NH proton. However, on cooling of the solution to -95 °C,
sharp resonances are seen for both 8 and 9 at -5.0 and -5.35
ppm, respectively. Significant changes are observed in the
aromatic region upon variation of temperature from 25 to -95
°C (Figure 2). Specifically, in addition to line broadening of
all of the resonances, the selenophene protons (bb′, cc′),
bipyrrole protons (dd′, ee′), and pyrrole protons (aa′) that were
equivalent at 25 °C show doubling of peaks at -95 °C. This
observation can be explained by assuming the following possible
tautomeric equilibrium. The equivalence of pyrrole, selenophene,
and bipyrrole protons at room temperature suggests the existence
of a rapid tautomerism, as observed for many tetrapyrrolic
macrocycles.41 However, at -95 °C, the existence of tautomer
I is excluded by the fact that this is a symmetric tautomer with
respect to the mirror plane passing through the pyrrole nitrogen
and the middle of bipyrrolic unit and accordingly only a singlet
Figure 1. (A) UV-vis spectra for 9 (6.976 × 10-6 M) in dichloro-
methane, (B) UV-vis spectra for diprotonated salt of 16 (1.807 ×
10-5M) in dichloromethane with excess TFA solution, and (C) plot of
number of π electrons versus λmax of the core-modified expanded
porphyrins.
bipyrrole unit is in the ring current region while the â protons
of the ring are in the periphery; in the inverted geometry, the
heteroatom is in the periphery while the â-CH protons come
1
into the ring current region. The H NMR chemical shifts can
easily distinguish between the two geometries. The N-5 meso-
aryl sapphyrin show an inverted geometry in its free base form
1
and planar geometry when it is protonated.39,40 Thus H NMR
chemical shifts of 8, 9, and 15 suggest that 8 and 9 have planar
structures while 15 has inverted structure.36 Unlike in N-5 meso-
(39) Rachlewicz, K.; Sprutta, N.; Latos-Grazynski, L.; Chmielewski, P.
J.; Szterenberg, L. J. Chem. Soc., Perkin Trans 2 1998, 959-967.
(40) Narayanan, S. J.; Sridevi, B.; Srinivasan, A.; Chandrashekar, T. K.;
Roy, R. Tetrahedron Lett. 1998, 39, 7389-7392.

9060 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
is expected for the pyrrole protons (aa′) at this temperature, in
contrast to experimental observation. Furthermore, the doubling
of the selenophene protons (bb′, cc′) and bipyrrole protons (dd′,
X-ray analysis) show broad resonances of varying line widths
(20.1, 18.1, and 12 Hz). However, the crystals grown in a CH2-
Cl2/hexane mixture show sharp well-defined resonances for the
pyrrole, bipyrrole, selenophene, and meso phenyl protons. Figure
3 shows the effect of addition of different concentrations of
methanol to the solution containing a crystal of 9 grown in the
CH2Cl2/hexane mixture. It is seen from the figure that addition
of methanol results in line broadening of pyrrole protons (a),
selenophene protons (b, c), bipyrrole protons (d, e), and phenyl
protons (f-i) and that the extent of broadening is different for
different protons. Furthermore, the spectrum of the crystal grown
in CH2Cl2/CH3OH (the one used for X-ray analysis) resembles
that shown in Figure 3 after addition of methanol. This
observation clearly suggests that supramolecular array is retained
in solution as well.6 Compound 8 also behaves in the same
fashion.
ee′) suggests that the proton is exchanging site only between
two bipyrrolic nitrogens, revealing the existence of tautomers
of II and III. A similar observation was made by Latos
Grazynski et al.36 for 8 and 15 very recently, and activation
parameters are also reported. Upon protonation two separate
NH resonances are seen for 8 and 9, suggesting the inequiva-
lence of pyrrole and bipyrrole NH protons, as well as retainment
of planar geometry.
The structure of the TFA adduct of 8 is shown in Figure 4.
There are five TFA molecules in the unit cell, out of which
only one is directly involved in binding with the protons of the
ring nitrogens above the plane of the macrocycle. The second
TFA molecule is linked to bound TFA through O7 with
O7‚‚‚H-O hydrogen bonding (length 2.571(14) Å, bond angle
170.62°). The remaining TFA molecules are linked with each
other through a series of O‚‚‚H-O hydrogen bonds and are
linked to the sapphyrin molecule by C19-H19A‚‚‚F1 (3.17(3)
Å, 129.02°), C39-H39‚‚‚O5 (3.374(10) Å, 168.15°), and C44-
H44A‚‚‚O5 (3.483(10) Å, 174.30°). The TFA binding results
in severe nonplanarity of the otherwise planar macrocycle, in
which the two thiophene rings are twisted below the plane of
the macrocycle. The three nitrogen atoms bearing protons that
are involved in binding are pointing above the plane of the
macrocycle, facilitating the binding of the anion.
1H NMR spectral studies of 13 and 14 also show considerable
aromatic character despite the removal of a meso carbon. The
NH tautomerism in 13 is very rapid, and even at -50 °C the
inner NH resonances are not seen in the NMR spectrum,
suggesting that the molecule adopts a symmetric conformation
with respect to the mirror plane passing through the methine
bridge and the furan oxygen atom. The bipyrrole protons and
the furan protons resonate in the aromatic region. In contrast,
14 exhibits asymmetric tautomerism in which the NH proton
adjacent to the furan ring is localized and only the NH proton
on the bipyrrole ring is changing sites between the two nitrogen
atoms of the bipyrrole ring. This observation was confirmed
by the 2D-TOCSY spectrum.
Sessler and co-workers23d have recently published solid state
structures of TFA adducts of two sapphyrins, all aza sapphyrins
(N5) and a furan-containing sapphyrin (ON4), in which two
molecules of TFA are bound above and below the plane of the
macrocycle. We choose to compare the mode of binding of TFA
in N5 and ON4 sapphyrins with the TFA adduct of 8. This
comparison, shown in Scheme 5, reveals many interesting
similarities and differences: (a) In both N-5 and ON4 sapphy-
rins, two molecules of TFA are bound, one each above and
below the plane of the macrocycle, with N-H‚‚‚O interactions.
One TFA has three such interactions in both the cases, while
the other in N-5 has two and ON4 has one such interaction,
corresponding to the number of available hydrogen bonding
sites.23d (b) In both cases, the carbonyl oxygen is not involved
in binding. (c) In the TFA adduct of 8 only one TFA molecule
is involved in direct binding with the macrocycle with three
N-H‚‚‚O interactions, but the difference is that both of the
oxygens of TFA are involved in the binding, which is
reminiscent of metal carboxylate binding in metal complexes.42
The C-O distances are almost similar (C1C-O7, 1.233(7) Å
and C1C-O8, 1.238(7) Å). These CO bond distances and the
OCO bond angle (O7-C1c-O8, 128.0(6)°) compare well with
the copper complex of trifluoro carboxylate (C-O, 1.242(11)
Å and O-C-O 129.0(9)°).42 (d) A comparison of the bond
distances listed show a regular decrease in the N-H‚‚‚O bond
length as the number of such interactions are reduced. This
comparative data clearly highlights how the macrocycle adjusts
itself to the environment (in this case, a reduced number of
H-bonding sites) around which it should bind anions.
Structure of Sapphyrins. In accordance with 1H NMR
results, both 8 and 9 show a planar structure in the solid state,
with only small deviations from the planarity.32 Substitution of
pyrrole NH by S and Se changes the π electron delocalization
pattern, and the bond distances are altered in the macrocycles
relative to the free thiophene or selenophene rings. The NH
proton present on the bipyrrole nitrogen shows hydrogen
bonding interactions with both of the heteroatoms inside the
cavity. For example, H‚‚‚S1 and H‚‚‚S2 distances for 8 are
2.87(8) Å and 2.55(8) Å, whereas the corresponding H‚‚‚Se1
and H‚‚‚Se2 distances for 9 are 2.63(17) Å and 2.28(17) Å,
respectively. The important feature of the structure is the
presence of weak intermolecular hydrogen-bonding interactions
involving C-H‚‚‚S and C-H‚‚‚Se in 8 and 9, respectively; as
described previously,32 these interactions are responsible for the
supramolecular ladder-like arrangement of 8 and 9 in the solid
state.
To investigate whether these supramolecular structures are
confined only to solid-state packing forces or they are prevalent
in solution, we have recorded 1H NMR spectra of crystals of 9
grown in two different solvent mixtures. To our surprise, the
crystals grown in a CH2Cl2/CH3OH mixture (the one used for
(41) (a) Crossley, M. J.; Field, L. D.; Harding, M. M.; Sternhell, S. J.
Am. Chem. Soc. 1987, 109, 2335-2341. (b) Vogel, E.; Kocher, M.;
Schmickler, H.; Lex, J. Angew. Chem., Int. Ed. Engl. 1986, 25, 257-259.
(c) Wehrle, B.; Limbach, H.-H.; Kocher, M.; Ermer, O.; Vogel, E. Angew.
Chem., Int. Ed. Engl. 1987, 26, 934-936. (d) Braun, J.; Schlabach, M.;
Wehrle, B.; Kocher, M.; Vogel, E.; Limbach, H.-H. J. Am. Chem. Soc.
1994, 116, 6593-6604.
1H NMR of Rubyrins. The 1H NMR spectra of rubyrins are
found to be critically dependent on the temperature. At room
(42) Doedens, R. J. Progress in Inorganic Chemistry; Lippard, S. J., Ed.;
John Wiley & Sons: New York, 1976; 21, pp 209-231.

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9061
Figure 3. Effect of the addition of different concentrations of methanol on the 1H NMR spectra of 9 (4.94 × 10 -3M). The number on the left (µL)
represents the concentration of methanol added.
temperature all of the rubyrins give only broad signals (line
width, ∼38.4 Hz), and as the temperature is lowered the
spectrum becomes fairly resolved, making assignments possible.
This observation suggests that the heterocyclic rings linked to
the bipyrrole units are rapidly rotating and at low temperature
the rate of rotation is reduced relative to the NMR time scale.
It is also observed that protonation of the rubyrins leads to
reasonably resolved spectra, suggesting that the protonation also
leads to reduction in the rate of rotation of heterocyclic rings.
Figure 5a and b shows the 1H NMR spectra of 10 at -50 °C in
its free base and protonated forms, respectively. Specifically,
the free base of 10 shows the thiophene protons (t) at 0.55 and
0.35 ppm, with the bipyrrole protons (bb′,cc′) at 8.93 and 8.36
ppm and the phenyl protons as a multiplet at 7.78 ppm. These
temperature (Figure 5c) and well-resolved spectra at at -50 °C
(Figure 5b). The thiophene protons (t) experience a dramatic
downfield shift (0.45 to 8.74 ppm) and the -NH protons (e, d)
appear as two singlets between -2 to -4 ppm. Furthermore,
the bipyrrole protons (bb′, cc′), which were equivalent at room
temperature, become inequivalent at -50 °C, resulting in the
appearance of an additional doublet of doublet (b, b′, c, c′).
Similar behavior is also observed for 17.
1
In comparison, 11 behaved differently than 10. The H-1H
COSY spectrum recorded at -50 °C is shown in Figure 6. In
this case, it is possible to observe the inner -NH proton as a
broad signal at -1.0 ppm (d), and the selenophene protons
appear at 9.85 ppm (a). Both the selenophene protons and the
NH protons do not show any correlations, whereas the bipyrrole
protons (b, c) reveal correlation. Protonation of 11 leads to
resolvable spectra at room temperature and well-resolved spectra
at -50 °C with sharp NH resonances, (Figure 5d and 5e). As
in the case of 10, here also the bipyrrole protons (bb′, cc′)
become inequivalent at -50 °C. It was not possible to record
assignments were made on the basis of the H-1H and H-
13C COSY spectrum recorded at -50 °C. The fact that the
thiophene protons are still broad at this temperature suggesta
that the rotation is not completely arrested. Protonation of 10
leads to observance of resonably resolved spectra at room
1
1

9062 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
Scheme 5. Binding Modes of Trifluoroacetic Acid Anion to
the N5 Sapphyrin, ON4 Sapphyrin, and S2N3 Sapphyrin 8a
Figure 4. ORTEP diagram illustrating the geometry of the bound TFA
anion in the complex [8.TFA]. Top, plane view; bottom, side view
(phenyl rings are omitted for clarity). The other four TFA molecules
(cocrystallized in the lattice) are also omitted for clarity.
1
well-resolved H NMR spectra for the free base of 16 even at
low temperature. However, the protonation leads to the same
effects as observed for 10, 11, and 17.
The conclusions arrived from 1H NMR results on the solution
structure of rubyrins are summarized in the Scheme 6. It is seen
that 10 and 17 in their free base forms have similar structures
in which both the thiophene rings in 10 and thiophene and furan
rings in 1743 are inverted resulting in the appearance of â C-H
ring protons in the shielded region as observed at -50 °C.
Protonation leads to the flipping of the thiophene rings, resulting
in the appearance of these protons in the aromatic region. Such
a ring inversion upon protonation has been observed by Latos-
Grazynski et al.39 for the N-5 meso-aryl sapphyrins, and to the
best of our knowledge this is the first report on rubyrins. The
solid-state structure of 10 (vide infra) also supports such an
inversion of the thiophene rings. However, chemical shifts
observed for the selenophene protons in the free base form for
11 force us to conclude that 11 has a normal structure at -50
°C in which the two selenophene rings are not inverted in
solution. However, the X-ray structure of 11 in its free base
form in the solid state show inversion of the selenophene rings
(vide infra). The protonated form of 16 also has the similar
structure as observed for 10, 11, and 17.
a Data for N5 Sapphyrin and ON4 Sapphyrin are taken from ref
23(d).
are two molecules of benzonitrile solvent per macrocycle unit.
It is clear from the figure that the two thiophene rings are
inverted with respect to the plane containing the bipyrrole rings.
Specifically, the thiophene ring (S1) is 14.10° above and the
thiophene ring (S1′) is 14.10° below the plane containing the
bipyrroles. Substitution of pyrrole NH by thiophene S changes
the π-electron delocalization, and the bond distances are altered
accordingly relative to those observed for the HCl salt of N6
rubyrins16 (Table 2). The aromatic nature of the macrocycle is
evident from the observation that the CR-Câ distances
(1.411(3) Å, 1.401(3) Å) are higher than the average Câ-Câ
distances (1.360(3) Å).16 Furthermore, a comparison of the
interpyrrole (heterocycle) angles at the bridging methines with
X-ray Structure of Rubyrins. The single-crystal X-ray
structure of 10 in its free base form is shown in Figure 7. There
(43) Preliminary X-ray structure of 17 suggests that the furan and the
thiophene rings are inverted in the solid state.

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9063
Figure 5. 1H NMR (CDCl3) spectra of (a) 10 at -50 °C, (b) bis-TFA salt of 10 at -50 °C, (c) bis-TFA salt of 10 at 25 °C, (d) bis-TFA salt of
11 at 25 °C, and (e) bis-TFA salt of 11 at -50 °C.
those of the N6 rubyrins reveal significant lowering of the angles
in 10. For example, the angles C19-C12-C4 (123.3(2)°) and
C1-C5-C26′ (123.30(19)°) observed for 10 are lower than the
corresponding angles observed for N6 rubyrins16 (137.0° and
137.63°, respectively), and surprisingly these angles are closer
to that observed for porphyrins (127° for H2OEP2+),16 suggesting
that the ring inversion results in the less open inner core. The
repulsion due to the NH and CH are avoided by tilting of
thiophene rings above and below the plane containing the
bipyrrole.
The effect of ring inversion leads to increases (N2-N2′ 7.431
Å for 8, 6.345 Å for N6 rubyrin) in the distances of diagonal
nitrogens and decreases (N1-N2 2.688 Å for 8, 3.078 Å for
N6 rubyrin) in the adjacent nitrogens relative to N6 rubyrins.16
The observed average C-N distances (1.359 Å) compares well
with those observed for N6 rubyrins (1.365 Å).16 The C-S
distances (1.745 Å) are close to the value observed for thia
porphyrins (1.737 Å).44
the plane containing the selenophene ring (Se1) and the plane
containing the pyrrole ring (N4) is 23.01°. The CR-Câ distances
of the selenophene rings vary in this case. For example, C3-
C4 and C1-C2 distances are 1.381(14) and 1.390(13) Å,
respectively. On the other hand, C29-C30 and C27-C28
distances of other selenophene ring are 1.409(14) and
1.414(14) Å, respectively. Even the Câ-Câ distances of two
selenophene rings are different (C2-C3, 1.412(13) Å and C28-
C29, 1.366(14) Å.) However, the CR-Câ distances (C12-C13,
1.445(14) Å; C14-C15, 1.432(15) Å; C16-C17, 1.403(14) Å;
C18-C19, 1.426(15) Å) are higher than the Câ-Câ distances
(C13-C14, 1.3119(15) Å; C17-C18, 1.381(15) Å), confirming
the aromatic nature. The interpyrrole (heterocycle) angles at the
bridging methines are 124.5(9)° and 122.3(9)°, which are similar
to those observed for 10. Here also the ring inversion leads to
increases in diagonal nitrogen distances (N1-N3, 7.323 Å) and
decreases in adjacent nitrogen distances (N1-N2, 2.759 Å)
relative to N6 rubyrins.16 The average C-N distance is 1.363
Å, and the C-Se distances (C1-Se1, 1.891(10) Å; C27-Se2,
1.903(11) Å) are closer to that observed for the selenaporphyrins
(1.85 Å).26b, 45
The single-crystal X-ray structure of 11 is shown in Figure
8. The unit cell contains two crystallographically independent
molecules with a molecule of methanol coordinated to one of
them. There are five nitrobenzene solvent molecules, one of
which is highly disordered. The selenophene rings are found to
be inverted, and both of the selenophene rings are above the
mean plane defined by four meso carbons. The angle between
A comparison of the structures of 10 and 11 shows some
similarities and some differences. In both structures the imino
hydrogen atom could not be assigned unequivocally to a specific
bipyrrole nitrogen atom as a result of the rapid interconversion
(44) Latos-Grazynski, L.; Lisowski, L.; Szterenberg, L.; Olmstead, M.
M.; Balch, A. L. J. Org. Chem. 1991, 56, 4043-4045.
(45) Latos-Grazynski, L.; Pacholska, E.; Chmielewski, P. J.; Olmstead,
M. M.; Balch, A. L. Inorg. Chem. 1996, 35, 566-573.

9064 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
1
Figure 6. 2D H-1H COSY spectra of 11 in CDCl3.
Scheme 6. Solution Structure of Rubyrins before and after Protonation
of NH tautomers during the time required for the measurement.
Our analysis suggests a 50% probability of occupation on each
nitrogen atom. The difference in the structure exists in the
orientation of the inverted rings. For example, in 10 the
thiophene rings are tilted above and below the plane containing
bipyrroles, thus making the â carbons C2 and C3 above the
plane while C2′ and C3′ are below the plane by an angle of
14.10°. However, in 11, both selenophene rings are above the
plane containing the bipyrrole units by an angle 23.01°, thus
making the â carbons C2, C3 and C28, C29 above the plane.
This is clearly seen in the side view of Figures 7 and 8.
To get further insight into the inversion of the heterocyclic
rings in rubyrin, the structure of selenatripyrrane 5 was solved
by single-crystal X-ray diffraction (Figure 9). The structure
clearly shows that the pyrrole rings are trans to each other with
respect to the selenophene ring. The dihedral angles between
the central selenophene and the terminal pyrroles (Se1-C1-
C5-C12 and Se1-C4-C16-C23) are 31.3(6)° and 65.7(5)°,

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9065
Figure 9. ORTEP diagram of the selenophene-containing tripyrrane
5.
the required planar conformation for the formation of second
pyrrole-pyrrole link is achieved through a possible free rotation
along C1-C5 or C4-C16.29,34b
Conclusions
Synthesis of a range of core-modified sapphyrins and rubyrins
has been achieved by an acid-catalyzed condensation reaction
involving a single precursor, the modified tripyrranes. The
finding that the methodology works smoothly for three different
tripyrranes and the possible cross-coupling reaction between two
different tripyrranes highlights the versatility of the synthetic
method. Successful synthesis of stable smaragdyrin, a new mode
of binding of the TFA anion to the protonated sapphyrin, and
the retention of a supramolecular array of sapphyrins in solution
are some of the new features observed. Furthermore, the ring
inversion of rubyrins in the solid state and the dramatic ring
flipping on protonation are observed for the first time. It is hoped
that the availability of easy synthetic methodologies to prepare
these fascinating expanded porphyrins in multigram quantities
will allow development of their diverse chemistry and the
exploitation of their use in biomedical applications.
Figure 7. Two views of the molecular structure of 10 showing inverted
thiophene rings. In the side view the phenyl rings are omitted for clarity.
Experimental Section
Instrumentation. 1H NMR spectra were measured on a 300 or 500
MHz Bruker spectrometer or a 400 MHz Varian spectrometer in CDCl3
or CD2Cl2 solution. Chemical shifts are expressed in parts per million
relative to residual CHCl3 (7.258 ppm) or CH2Cl2 (5.3 ppm). FAB mass
spectra were obtained on a JEOL SX-120/DA6000 spectrometer. The
electrospray mass spectra were recorded on a MICROMASS QUAT-
TRO II triple quadrupole mass spectrometer. Analyses (C, H, N) were
done on a Heraeus Carlo Erba 1108 elemental analyzer. The melting
points are uncorrected and were measured on a JSGW melting point
apparatus. The UV-vis spectra were recorded on a Shimadzu UV-
vis spectrophotometer and a Perkin-Elmer Lamda 20 UV-vis spec-
trophotometer.
Materials. All NMR solvents were used as received. Dicloromethane
was dried by distillation under nitrogen by calcium hydride. Tetra-
hyrofuran (THF) was distilled from sodium/benzophenone under
nitrogen. Triethylamine was dried over KOH pellets and distilled under
vacuum. n-Hexane was distilled under nitrogen from sodium. Pyrrole,
thiophene, and furan (Aldrich) were distilled and then used. Selenophene
was used as received. n-BuLi, trifluoroacetic acid (TFA), p-toluene-
sulfonic acid, and p-chloranil (Fluka) were used as received. Silica gel
Figure 8. Two views of the molecular structure of 11 showing inverted
selenophene rings. In the side view the phenyl rings are omitted for
clarity.
respectively, thus showing that the molecule adopts a helical
twist in the solid state.8d This twisting of the molecule avoids
the formation of linear polymeric products during the condensa-
tion process, thus supporting the so-called helical effect involved
in the formation of the macrocycles.46 It is possible that the
first pyrrole-pyrrole link is formed in this conformation and
(46) (a) Franck, B. Angew. Chem., Int. Ed. Engl. 1982, 21, 343-353.
(b) Bringmann, G.; Franck, B. Liebigs Ann. Chem. 1982, 1272-1279. (c)
Tietze, L. F.; Geissler, H. Angew. Chem., Int. Ed. Engl. 1993, 32, 1040-
1042. (d) Vogel, E.; Dorr, J.; Herrmann, A.; Lex, J.; Schmickler, H.;
Walgenbach, P.; Gisselbrecht, J. P.; Gross, M. Angew. Chem., Int. Ed. Engl.
1993, 32, 1597-1600.

9066 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
Table 1. Crystallographic Data for 10, 11, 5, and the TFA Adduct of 8
TFA adduct of 8
10
11
5
solvent for crystallization dichloromethane/TFA/methanol benzonitrile/methanol nitrobenzene/ethanol/methanol dichloromethane/n-heptane
empirical formula
temperature (K)
crystal system
space group
volume (Å3)
a (Å)
C58H36F15N3O10S2
298(2)
triclinic
C66H44N6S2
213(2)
monoclinic
C2/c
5047.2(2)
29.0002(6)
15.0991(4)
11.9801(3)
90
105.816(1)
90
C136H99N13O11Se4
298(2)
triclinic
C26H20N2Se
213(2)
monoclinic
P2(1)/c
2097.58(7)
5.9753(1)
13.1916(2)
26.6852(6)
90
94.272(1)
90
P1
P1
2812.42(10)
13.7165(3)
14.8857(2)
16.5289(4)
104.403(1)
109.278(1)
107.093(1)
2
5645.58(14)
16.8453(3)
17.1105(2)
21.2573(3)
91.248(1)
112.815(1)
90.368(1)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
Z
4
4
calcd density (mg/m3)
reflections collected
unique
1.516
9469
5680
1.297
10690
3601
1.416
19762
11511
1.391
10698
3946
R(int)
F(000)
0.0603
1304
0.0701
2056
0.0575
2460
0.0649
896
limiting indices
-13 E h E 13
-8 E k E 14
-16 E l E 16
1.197
-32 E h E 32
-16 E k E 11
-13 E l E 13
1.045
-16 E h E 14
-17 E k E 17
-21 E l E 21
1.107
-7 E hE 5
-15 E k E 16
-28 E l E 32
1.181
goodness of fit (F2)
final R indices {I > 2σ(I)} R1 ) 0.0739
R1 ) 0.0444
wR2 ) 0.1132
R1 ) 0.0598
wR2 ) 0.1211
R1 ) 0.0768
wR2 ) 0.2041
R1 ) 0.1164
wR2 ) 0.2207
R1 ) 0.0656
wR2 ) 0.1250
R1 ) 0.1042
wR2 ) 0.1458
wR2 ) 0.1784
R indices (all data)
R1 ) 0.0931
wR2 ) 0.1926
Table 2. Selected Bond Lengths (Å), Bond Angles (deg), and Torsional Angles (deg) for 10, 11, and 5
10 11
5
S1-C1
S1-C4
C1-C2
C2-C3
C3-C4
C1-C5
C4-C12
C5-C26′
C12-C19
C5-C6
C12-C13
N1-C19
N1-C22
C19-C20
C20-C21
C21-C22
C22-C23
1.736(2)
1.753(2)
1.411(3)
1.360(3)
1.401(3)
1.415(3)
1.409(3)
1.408(3)
1.420(3)
1.496(3)
1.488(3)
1.364(3)
1.352(3)
1.427(3)
1.372(3)
1.414(3)
1.416(3)
Se1-C1
Se1-C4
C1-C2
C2-C3
C3-C4
C4-C5
C1-C46
C5-C12
1.891(10)
1.887(10)
1.390(13)
1.412(13)
1.381(14)
1.404(14)
1.411(13)
1.397(14)
1.391(13)
1.532(14)
1.483(14)
1.376(13)
1.321(13)
1.445(14)
1.311(15)
1.432(15)
1.433(15)
1.417(14)
Se1-C1
Se1-C4
C1-C2
C2-C3
C3-C4
C1-C5
C4-C16
C5-C12
1.884(5)
1.880(5)
1.337(7)
1.429(7)
1.353(6)
1.515(7)
1.509(6)
1.513(7)
1.525(6)
1.540(7)
1.524(6)
1.375(6)
1.378(7)
1.379(7)
1.431(8)
1.357(8)
C46-C45
C5-C6
C16-C23
C5-C6
C46-C47
N1-C12
N1-C15
C12-C13
C13-C14
C14-C15
C15-C16
C41-C42
C16-C17
N1-C12
N1-C15
C12-C13
C13-C14
C14-C15
N1-C3
N2′-N1
N1-N2
C3-C2′
N2-N2′
2.90
N1-C3
N1-N4
N1-N2
C3-C28
N1-N3
2.935
6.810
2.759
4.780
7.323
6.928
2.688
4.248
7.431
C1-S1-C4
93.49(10)
109.1(2)
122.72(16)
128.98(10)
123.3(2)
129.2(3)
123.39(19)
118.33(10)
C1-Se1-C4
C12-N1-C15
Se1-C1-C46
C2-C1-C46
C4-C5-C12
C13-C12-C5
N1-C12-C5
N1-C15-C16
88.5(5)
108.3(9)
122.2(8)
128.6(9)
124.5(9)
129.1(10)
124.4(10)
119.0(10)
C1-Se1-C4
C12-N1-C15
Se1-C1-C5
C2-C1-C5
C1-C5-C12
C13-C12-C5
N1-C12-C5
87.8(2)
C19-N1-C22
S1-C4-C12
C3-C4-C12
C4-C12-C19
C20-C19-C12
N1-C19-C12
N1-C22-C23
109.0(5)
121.6(3)
128.4(4)
112.6(4)
132.1(5)
119.5(5)
S1-C1-C5-C26′
C1-C5-C6-C11
C4-C12-C19-C20
N1-C22-C23-C24
-173.1(2)
65.0(3)
173.6(2)
179.7(2)
Se1-C4-C5-C12
C4-C5-C6-C7
C4-C5-C12-C13
N1-C15-C16-C17
-169.2(9)
64.9(14)
-169.1(11)
-179.3(12)
Se1-C1-C5-C12
C1-C5-C6-C7
C1-C5-C12-C13
31.3(6)
59.2(6)
-114.8(6)
(100-120 mesh) or basic alumina (Merck, usually Brockmann grade
III) was used for column chromatography. 16-Thiatripyrrane (4) and
16-oxatripyrrane (12) were prepared according to the published
procedure11c and stored under inert atmosphere at -10 °C.
obtained by stirring a chloroform solution containing 10% TFA and
the recrystallized sample of free base 8. The solution was evaporated,
and the single crystal of 8.TFA was obtained by layering the 10% TFA/
dichloromethane solution of 8.TFA with methanol in a thin glass tube.
The same crystallization technique was used to obtain the single crystals
X-ray Structure Determinations. The trifluoroacetate salt of 8 was

NoVel Core-Modified Expanded Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 39, 1999 9067
of 10, 11, and 5 using appropriate solvent mixtures as shown in the
Table 1. The X-ray diffraction data were collected on a Siemens
SMART 3-circle diffractometer equipped with a CCD detector. The
data were acquired with the Siemens SMART software and processed
on a SGI-Indy/Indigo 2 workstation by using the SAINT software.
Graphite monochromated Mo KR radiation (λ ) 0.71073 Å) was used
for data collection. The structures were solved by direct methods using
the SHELXS 90 program and refined by full-matrix least squares on
F2 using SHELXL 93, incorporated in SHELXTL-PC V 5.03. Details
of crystals are listed in Table 1 and selected bond lengths and angles
are given in Table 2. Other pertinent information, including X-ray
experimental details for each compound, is included in the Supporting
Information.
(ꢀ × 10-4) 470(22.4), 584(1.75), 623(1.07), 730(0.59), 820(1.68); UV-
vis (CH2Cl2/TFA) λmax (nm) (ꢀ × 10-4) 499(12.3), 660sh (1.17), 727-
(2.42), 826(2.74); FAB-MS m/z 714 [M+•]. Anal Calcd for
C48H31N3S2: C, 80.76; H, 4.38; N, 5.89. Found: C, 80.80; H, 4.35; N,
5.86. The last pink band eluted with ethyl acetate/dichloromethane (1:
3) gave a lustrous green solid, identified as the 5,10,19,24-tetraphenyl-
30,33-dithiarubyrin 10 (yield 20 mg, 8.5%, recrystallized from dichlo-
romethane/n-heptane (1:1): decomposes above 300 °C; 1H NMR (500
MHz, CDCl3, -50 °C) δ 0.35(s, 2H), 0.55(s, 2H), 7.45-7.48(m, 8H),
1
7.73-7.74(m, 12H), 8.360(s, 4H), 8.932(s, 4H); H NMR (300 MHz,
CDCl3/TFA, -50 °C) δ -2.91(s, 2H), -3.28(s, 2H), 7.68-7.94(m,
20H), 8.28(d, J ) 6 Hz, 2H), 8.74(br s, 4H), 9.89(d, J ) 6 Hz, 2H),
10.06(d, J ) 6 Hz, 2H), 10.62(d, J ) 6 Hz, 2H); 1H NMR (500 MHz,
CDCl3/TFA, 25 °C) δ -2.47(br s, 2H), -2.80(s, 2H), 7.95-7.98(m,
8H), 8.09(m, 12H), 8.88(br s, 4H), 9.80(d, J ) 4 Hz, 4H), 10.54(d, J
) 4 Hz, 4H); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4) 385(0.16),
532(14.2), 658(1.12), 764(0.9), 1017(1.36); UV-vis (CH2Cl2/TFA)
λmax (nm) (ꢀ × 10-4) 542(19.4), 722(0.82), 813(1.8), 1004 (5.9);
FAB-MS m/z 779 [M+•]. Anal Calcd for C52H34N4S2: C, 80.18; H,
4.40; N, 7.19. Found: C, 80.16; H, 4.35; N, 7.22.
Syntheses. 2,5-Bis(phenylhydroxymethyl)selenophene. A 2,5-
dilithioselenophene suspension was prepared by adding butyllithium
(12.72 mL,19.08 mmol) at room temperature to a mixture of n-hexane
(40 mL), TMEDA (2.87 mL, 19.08 mmol), and selenophene (1 g, 7.60
mmol) in an inert atmosphere. The mixture was stirred for about 30
min and then refluxed for 1 h to complete the conversion. Then the
mixture was allowed to cool to 10 °C, and benzaldehyde (1.93 mL,
19.08 mmol) in dry THF,(15 mL) was added dropwise. The temperature
of the reaction mixture was gradually raised to room temperature, and
stirring was continued for 60 min. The reaction was quenched with
saturated ammonium chloride solution and stirred for 30 min. The
organic layer was separated, and the aqueous layer was extracted with
diethyl ether. The organic layers were combined and dried over sodium
sulfate. The solvent was evaporated, and the product was recrystallized
from toluene to afford a white solid (yield 1.59 g, 57%): mp 143-
5,10,15,20-Tetraphenyl-26,28-diselenasapphyrin (9) and 5,10,19,-
24-Tetraphenyl-30,33-diselenarubyrin (11). The above procedure was
followed using the 16-selenatripyrrane 5 (0.15 g, 0.34 mmol), TFA
(0.053 mL, 0.68 mmol), and chloranil (0.25 g, 1.03 mmol). Sapphyrin
9 as a greenish purple solid and rubyrin 11 as a green solid were
obtained in 9.2% (25.4 mg) and 18.3% (54.6 mg) yields, respectively.
1
Data for 9: decomposes above 280 °C; H NMR (300 MHz, CDCl3,
25 °C) δ -4.4(br s, 1H), 7.6(m, 8H), 7.96(m, 4H), 8.39(m, 4H), 8.49
(m, 4H), 8.96(s, 2H), 9.36(d, 2H, J ) 6 Hz), 10.01(d, 2H, J ) 6 Hz),
10.35(d, 2H, J ) 6 Hz), 10.47(d, 2H, J ) 6 Hz); UV-vis (CH2Cl2)
λmax (nm) (ꢀ × 10-4) 475(30.1), 517(6.4), 592(2.8), 631(1.8), 736-
(0.7), 823(3.2); UV-vis (CH2Cl2/TFA) λmax (nm) (ꢀ × 10-4) 519-
(19.8), 677 (0.96), 752 (1.83), 859(2.9); FAB-MS m/z 810 [M+• for
80Se]. Anal Calcd for C48H31N3Se2: C, 71.38; H, 3.87; N, 5.20. Found:
C, 71.32; H, 3.89; N, 5.25. Data for 11: decomposes above 300 °C; 1H
NMR (300 MHz, CDCl3, -50 °C) δ 9.88(s, 4H), 9.66(d, 4H, J ) 4.2
Hz), 8.91(d, 4H, J ) 4.2 Hz), 8.64-8.66(m, 8H), 7.94-8.10(m, 8H),
1
144 °C; H NMR (400 MHz, CDCl3) δ 2.27(br s, 2H), 5.85(s, 2H),
6.77(s, 2H), 7.17-7.28(m, 6H), 7.30-7.38(m, 4H); EI-MS 343 (M+).
Anal. Calcd for C18H16O2Se: C, 62.98; H, 4.70. Found: C, 62.92; H,
4.73.
16-Selenatripyrrane (5). 2,5-Bis(phenylhydroxymethyl)selenophene
(0.7 g, 2.04 mmol) was dissolved in pyrrole (5.6 mL, 81.60 mmol),
and the mixture was degassed by bubbling nitrogen gas. Trifluoroacetic
acid (TFA) (0.015 mL, 0.20 mmol) was added to this solution, and the
mixture was stirred for about 30 min at room temperature. The
completion of the reaction was followed with TLC. Dichloromethane
(100 mL) was added, and the reaction mixture was neutralized with
40% NaOH solution. The organic layer was separated and washed two
times with water (50 mL) before drying over sodium sulfate. The excess
pyrrole was removed at room temperature by vacuum. Chromatography
on silica gel with ethyl acetate and petroleum ether (1:10) gave the
desired tripyrrane as a pale yellow solid (yield 0.65 g, 75%): mp 105-
106 °C; 1H NMR (300 MHz, CDCl3) δ 5.59(s, 2H), 5.97(s, 2H), 6.16-
6.13(m, 2H), 6.68(m, 2H), 6.80(s, 2H), 7.35-7.24(m, 10H), 7.91(br s,
2H); EI-MS: 443 (M+). Anal. Calcd for C26H24N2Se: C, 70.42; H,
5.45; N, 6.32. Found: C, 70.47; H, 5.48; N, 6.28.
1
7.68-7.81(m, 4H), -0.06(br, s); H NMR (300 MHz, CDCl3/TFA,
-50 °C) δ -2.95(s, 2H), -3.07(s, 2H), 7.87-8.15(m, 20H), 8.24(d, J
) 6 Hz, 2H), 8.82(br s, 4H), 9.83(d, J ) 6 Hz, 2H), 10.06(d, J ) 6
1
Hz, 2H), 10.62(d, J ) 6 Hz, 2H); H NMR (500 MHz, CDCl3/TFA,
25 °C) δ -2.47(br s, 2H), -2.56(br s, 2H), 7.94-7.97(m, 8H), 8.06-
(m, 12H), 8.9(br s, 4H), 9.72(d, J ) 4 Hz, 4H), 10.53(d, J ) 4 Hz,
4H); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4) 530(13.4), 666(1.09),
766(0.62), 849(0.77), 970(1.34); UV-vis (CH2Cl2/TFA) λmax (nm)
(ꢀ × 10-4) 546 (15.4), 728 (0.98), 814(1.11), 1016(5.07); FAB-MS
m/z 875(100) [M+• for 80Se]. Anal Calcd for C52H34N4Se2: C, 71.56;
H, 3.93; N, 6.42. Found: C, 71.52; H, 3.96; N, 6.43.
5,10,19-Tetraphenyl-25-oxasmaragdyrin (13). This was prepared
by the reaction of 16-oxatripyrrane 12 (0.15gm, 0.4 mmol) with TFA
(0.003 mL, 0.042 mmol) followed by oxidation with chloranil (0.29gm,
1.19 mmol) by a similar procedure as described above. The crude
product upon chromatographic separation on basic alumina with
petroleum ether and dichloromethane (3:10) gave 13 as a purple solid
(yield 7.8 mg, 3.3%): decomposes above 275 °C; 1H NMR (300 MHz,
CDCl3, 25 °C) δ 7.83(m, 9H), 8.21(m, 4H), 8.38(m, 2H), 8.42(d, J )
4.2 Hz, 2H), 8.74(s, 2H), 8.95(d, J ) 4.2 Hz, 2H), 9.36(d, J ) 4.2 Hz,
General Procedure for the Synthesis of Macrocycles. 5,10,15,-
20-Tetraphenyl-26,28-dithiasapphyrin (8) and 5,10,19,24-Tetra-
phenyl-30,33-dithiarubyrin (10). 16-Thiatripyrrane 4 (0.12 g, 0.301
mmol) dissolved in dry CH2Cl2 (150 mL) was stirred under nitrogen
atmosphere for 5 min. The reaction mixture was protected from sunlight.
TFA (0.023 mL,0.301 mmol) was added, and stirring was continued
for a further 90 min. Chloranil (0.22 g, 0.903 mmol) was added, and
the reaction mixture was opened to air and refluxed for further 90 min.
The mixture was neutralized with triethylamine, and the solvent was
evaporated in vacuo. The residue so obtained was chromatographed
on a basic alumina column. The first orange fraction eluted with
petroleum ether and dichloromethane (2:1) gave a purple solid identified
as dithiaporphyrin 6 (2 mg, 1%). The second green band eluted with
ethyl acetate/dichloromethane (1:10) gave a greenish purple solid that
was identified as 5,10,15,20-tetraphenyl-26,28-dithiasapphyrin 8 (yield
30 mg, 14%, recystallised from toluene/n-heptane (1:1): decomposes
2H), 9.46 (d, J ) 4.2 Hz, 2H); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4
)
443(33.0), 456sh (16.0), 552(2.0), 591(1.4), 633(1.0), 696(1.4); UV-
vis (CH2Cl2/HCl) λmax (nm) (ꢀ × 10-4) 450(27.9), 482(13.5), 605(1.8),
657(2.4), 720(4.6); emission (CH2Cl2) λ ) 701 nm; FAB-MS m/z 593
[M+]. Anal Calcd for C41H28N4O: C, 83.09; H, 4.76; N, 9.45. Found:
C, 83.14; H, 4.72; N, 9.49.
5,10,15-Tetraphenyl-21-oxacorrole (14). This was prepared by a
similar procedure as above with 16-oxatripyrrane 12 (0.167gm, 0.44
mmol), TFA (0.17 mL, 2.2 mmol), and chloranil (0.328 mg, 1.33
mmol). In the chromatographic separation on basic alumina, the first
band eluted with a mixture of petroleum ether and dichloromethane
(1:10) gave 14 as a purple solid (yield 10 mg, 4.3%): decomposes
1
above 280 °C; H NMR (300 MHz, CDCl3, 25 °C) δ 7.85(m, 7H),
7.92(m, 4H), 8.37(m, 4H), 8.46(m, 4H), 8.81(s, 2H), 9.29(d, 2H, J )
3 Hz), 9.93(d, 2H, J ) 6 Hz), 9.95(d, 2H, J ) 6 Hz), 10.06(d, 2H, J
) 6 Hz); 1H NMR (300 MHz, CDCl3/TFA, 25 °C) δ -2.18(br s, 2H),
-2.85(s 1H), 8.18(m, 8H), 8.23(m, 4H), 8.76(m, 4H), 8.89 (m, 4H),
9.17(s, 2H), 9.75(d, 2H, J ) 6 Hz), 10.12(d, 2H, J ) 6 Hz), 10.32(d,
2H, J ) 6 Hz), 10.33(d, 2H, J ) 6 Hz); UV-vis (CH2Cl2) λmax (nm)
1
above 270 °C; H NMR (300 MHz, CDCl3, 25 °C) δ -1.91(s, 1H),
7.77(m, 9H), 8.13 (m, 2H), 8.30(m, 4H), 8.35(d, 1H, J ) 4.5 Hz),

9068 J. Am. Chem. Soc., Vol. 121, No. 39, 1999
Narayanan et al.
1
8.57(q, 1H), 8.78(d, 1H, J ) 5.1 Hz), 8.80 (d, 1H, J ) 4.8 Hz), 8.82-
(d, 1H, J ) 4.2 Hz), 9.03(d, 1H, J ) 4.2 Hz), 9.05(q, 1H), 9.09(d, 1H,
J ) 5.1 Hz); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4) 411(27.0), 497-
(1.6), 528(1.6), 583 (0.7), 632 nm (2.1); UV-vis (CH2Cl2/HCl) λmax
(nm) (ꢀ × 10-4) 412(24.3), 431sh (13.7), 523(3.2), 583(0.3), 635(5.4);
emission (CH2Cl2) λ ) 640 nm; emission (CH2Cl2/HCl) λ ) 652 nm;
FAB-MS m/z 528 [M+]. Anal Calcd for C37H25N3O: C, 84.23; H, 4.78;
N, 7.96. Found: C, 84.27; 4.75; N, 7.99.
300 °C; H NMR (300 MHz, CDCl3, -50 °C) δ 2.15(s, 2H), 2.69(s,
2H), 7.47-7.52(m, 8H), 7.66-7.70(m, 12H), 8.09-8.10(d, 1H), 8.15-
(s, 1H), 8.18(s, 1H), 8.19(s, 1H), 8.23(s, 1H), 8.26(s, 1H), 8.45-8.46-
(d, 1H), 8.48-8.50(d, 1H); 1H NMR (300 MHz, CDCl3/TFA, -50 °C)
δ -1.83(s, 1H), -2.06(s, 1H), -2.21(s, 1H), -2.32(s, 1H), 7.80-7.85-
(m, 8H), 7.94(br s, 2H), 8.05-8.10(m, 12H), 8.21(d, 1H), 8.25(s, 1H),
8.73(br s, 2H), 8.86(d, J ) 6 Hz, 1H), 9.70(d, J ) 6 Hz, 1H), 9.80(d,
J ) 6 Hz, 1H), 9.84(s, 1H), 10.30(d, J ) 6 Hz, 1H), 10.34(d, J ) 6
1
5,10,15,20-Tetraphenyl-26,28-dioxasapphyrin (15) and 5,10,19,-
24-Tetraphenyl-30, 33-dioxarubyrin (16). These compounds were
prepared similarly as above from 16-oxatripyrrane 12 (0.18 g, 0.47
mmol), TFA (0.07 mL, 0.93 mmol), and chloranil (0.34 g, 1.40 mmol).
Chromatographic separation on basic alumina with ethyl acetate/
dichloromethane (1:1) gave 15 as a greenish purple solid (yield 7.1
mg, 2.3% ). Upon changing the eluent to a mixture of dichloromethane/
methanol (1:1) 16 came as a greenish brown solid (yield 54 mg, 15.6%).
Data for 15: decomposes above 270 °C; 1H NMR (300 MHz, CDCl3)
δ -0.75 (s, 2H), 7.66 (m, 4H), 7.85 (m, 8H), 8.31 (m, 4H), 8.78 (d,
4H), 8.89(d, J ) 6 Hz, 2H), 9.12 (d, J ) 6 Hz, 2H), 9.54 (d, J ) 6 Hz,
Hz, 1H); H NMR (500 MHz, CDCl3/TFA, 25 °C) δ -1.48(s, 1H),
-1.77(s, 1H), -1.84(s, 1H), -1.94(s, 1H), 7.80-7.83(m, 4H), 7.94-
7.97(m, 4H), 8.02-8.09(m, 12H), 8.81(s, 2H), 8.82(s, 2H), 9.63(d, J
) 4 Hz, 2H), 9.75(d, J ) 4 Hz, 2H), 10.24(d, J ) 4 Hz, 2H), 10.28(d,
J ) 4 Hz, 2H); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4) 530(17.3),
647(2.0), 772(0.6), 1015(2.1); UV-vis (CH2Cl2/TFA) λmax (nm) (ꢀ ×
10-4) 549(34.7), 723(1.48), 807(1.4), 1011(10.9); electrospray-MS m/z
763 [M+]. Anal Calcd for C52H34N3SO: C, 81.87; H, 4.49; N, 7.34.
Found: C, 81.88; H, 4.46; N, 7.38.
Acknowledgment. This work was supported by a grant from
the Department of Science & Technology (DST) and Council
of Scientific and Industrial Research (CSIR), Government of
India, New Delhi, to T.K.C. The single-crystal CCD X-ray
facility at the University of Idaho was established with the
assistance of the NSF-Idaho EPSCoR program under NSF OSR-
9350539 and the M.J. Murdock Charitable Trust, Vancouver,
WA. The use of the 500 MHz NMR spectrometer at TIFR,
Bombay, is acknowledged. This paper is dedicated to Professor
P. T. Manoharan on the occasion of his 64th birthday.
2H), 9.74 (d, J ) 6 Hz, 2H); UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4
)
474(20.11), 581(2.1), 625(1.79), 741(0.59), 838(1.36); UV-vis (CH2-
Cl2/TFA) λmax (nm) (ꢀ × 10-4) 476 (16.0), 504(9.2), 629 (1.30), 686-
(1.11), 806(2.3); FAB-MS m/z 683 [M + 1]. Anal Calcd for
C48H31N3O2: C, 84.56; H, 4.58; N, 6.16. Found: C, 84.54; H, 4.59; N,
1
6.19. Data for 16: decomposes above 300 °C; H NMR (300 MHz,
CDCl3/HCl, 25 °C) δ -1.55(br s, 2H), -1.6(br s, 2H), 7.98(m, 12H),
8.51(s, 4H), 8.77(m, 8H), 9.61(s, 4H), 9.86(s, 4H); UV-vis (CH2Cl2)
λmax (nm) (ꢀ × 10-4) 564(4.8), 703(0.7), 771(1.26), 900(0.39), 1041-
(2.22); UV-vis (CH2Cl2/TFA) λmax (nm) (ꢀ × 10-4) 524(8.3), 584-
(2.8), 720(0.3), 875 (0.21), 985(2.46); FAB-MS m/z 748 [M + 1].
Anal Calcd for C52H34N4O2: C, 83.63; H, 4.59; N, 7.50. Found: C,
83.68; H, 4.63; N, 7.46.
5,10,19,24-Tetraphenyl-30-thia-33-oxarubyrin (17). This was syn-
thesized by the reaction of 16-thiatripyrrane 4 (0.32gm, 0.82 mmol)
and 16-oxatripyrrane 12 (0.31gm, 0.82 mmol) with TFA (0.006 mL,
0.08 mmol) followed by chloranil (0.61gm, 2.47 mmol) oxidation. This
was purified from column chromatography (basic alumina). Elution
with 1:10 ethyl acetate/dichloromethane gave 10 (20 mg, 2.8%). A pink
band eluted with mixture of 2:10 ethyl acetate/dichloromethane gave
a green solid identified as 17 (yield 160 mg, 25%): decomposes above
Supporting Information Available: 1D and 2D NMR
spectra of compounds 5, 8-11, 13-15, and 17, along with tables
of crystal data, structure solution and refinement, atomic
coordinates, bond lengths and angles, and anisotropic thermal
parameters for compounds 5, 10, 11, and the TFA adduct of 8.
X-ray crystallographic files are available through the Web only.
This material is available free of charge via the Internet at
http://pubs.acs.org.
JA991472K