Dithiaethyneporphyrin: An atypical [18]triphyrin(4.1.1) frame for contracted porphyrins

Article abstract of DOI:10.1002/anie.200501635

Fusion of the structural motifs 21,23-dithiaporphyrin and acetylene yields the 18-π-aromatic [18]triphyrin(4.1.1) framework (see structure; C gray, N blue, S yellow). The butyne moiety that joins the two thiophene rings reveals a slight distortion from li

Full text of DOI:10.1002/anie.200501635

Communications
distinguished by the fact that they contain only three pyrrole
or pyrrole-like rings, linked by two sp2-hybridized meso car-
bon atoms to form the tripyrrolic brace. The macrocyclic
structure of triphyrins is completed by a single chain of sp2-
and/or sp-hybridized carbon atoms. Besides vacataporphyrin,
only [15]triphyrin(1.1.3), which was obtained serendipitously
during the condensation of triisopropylsilyl propynal with 3,4-
diethylpyrrole, meets the criterion outlined above.[5] Alter-
natively, the replacement of the six inner protons of
[18]annulene by three oxygen, sulfur, or NH (NR)groups,
or some combination of the three, as explored originally by
Badger et al., leads to heteroatom-bridged annulenes 2; that
[6–8]
is, [18]triphyrin(2.2.2)or [18]heterotriphyrin(2.2.2).
Herein, we report the synthesis and characterization of
3,8,13,18-tetraphenyl-19,21-dithiaethyneporphyrin
(H(S2-
ETPP); 3). This porphyrin derivative is a novel type of
Porphyrinoids
DOI: 10.1002/anie.200501635
Dithiaethyneporphyrin: An Atypical
[18]Triphyrin(4.1.1) Frame for Contracted
Porphyrins**
´
Anna Berlicka, Lechosław Latos-Graz˙ynski,* and
Tadeusz Lis
contracted heteroporphyrin related to putative [18]triphyrin-
(4.1.1)with an acetylene moiety embedded in the macrocyclic
framework. It introduces a unique structural pattern for
contracted porphyrins,[2,4] created by fusing the structural
motifs of 21,23-dithiaporphyrin and acetylene.
The aza-deficent porphyrin 5,10,15,20-tetraaryl-21-vacatapor-
phyrin (butadieneporphyrin, [18]triphyrin(6.1.1); 1)is an
The synthetic strategy for 3 (Scheme 1)resembles the
[3+1] approach applied to prepare porphyrins, heteropor-
phyrins, and carbaporphyrinoids.[9] Retrosynthetic analysis
led to the identification of 1,4-di(2-thienyl)-1,4-diphenyl-2-
butyne (7)as the fundamental building block for the
construction of 3. Eventually, dithiaethyneporphyrin 3 was
formed through a condensation reaction that is similar to the
[3+1] procedure for porphyrins, although the meso carbon
atoms here originated from 9 rather than the usual mono-
pyrrolic fragment (12.7% yield).
The electronic spectrum of 3 (Figure 1)shows a distinct
intense Soret-like band at l = 448 nm accompanied by less-
intense Q bands at 518, 553, 646, and 725 nm, resembling the
spectroscopic features of aromatic 5,10,15,20-tetraphenyl-
annulene–porphyrin hybrid.[1] In principle, vacataporphyrin
1 (paradoxically expanded porphyrin)[2–4] can be considered
as a seminal molecule for the subclass of triphyrins, which are
1
21,23-dithiaporphyrin, S2TPP.[10] The H NMR spectrum of 3
also resembled that of S2TPP[10] and displayed resonances at
positions consistent with an aromatic structure: porphyrinoid
3 retains macrocyclic aromaticity through an 18-p-electron
delocalization motif. The scalar coupling detected between
NH20 and the b-pyrrolic protons H10 and H11 confirms the
molecular structure of 3 (Figure 2). The 13C NMR chemical
shifts of the four-carbon linker derived from 2-butyne reveals
a symmetric structure, with d = 116.8 ppm for C1 and C2 and
d = 111.9 ppm for C3 and C18.
´
[*] A. Berlicka, Prof. Dr. L. Latos-Graz˙ynski, Prof. Dr. T. Lis
Department of Chemistry
University of Wrocław
F. Joliot-Curie Street 14
50 383 Wrocław (Poland)
Fax: (+71)32-823-48
E-mail: llg@wchuwr.chem.uni.wroc.pl
[**] Financial support from the Ministry of Scientific Research and
Information Technology (Grant 3 T09A 162 28) isgratefully
acknowledged.
Two canonical structures of 3 define 18-p-electron macro-
cyclic delocalization pathways (Scheme 2). Accordingly, the
Supporting information for thisarticle isavailable on the WWW
under http://www.angewandte.org or from the author.
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Chemie
relevant chemical shift values of carbon
atoms for acetylene or cumulene units
attached adjacent to aryl or 2-thienyl
moieties were considered for compari-
son. The sp-hybridized carbon atoms of
intermediate 7 gave a 13C NMR signal at
d = 84.4 ppm, that is, in the d = 70–
95 ppm range typical for acetylene. Sim-
ilarly, the 13C NMR chemical shifts of
cumulene fragments vary over quite a
wide range: d = 140.5 ppm for tetra(2-
thienyl)butatriene,[11] d = 152.0 ppm for
tetraphenylbutatriene,[12]
and
d =
134.5 ppm for 6,7,18,19-tetradehydro-
tetrathia[24]annulene(4.0.4.0)(some
admixture of the acetylenic structure
was suggested for the latter structure).[13]
Thus the 13C NMR chemical shifts of 3
point out that canonical structure 3ac and
3cum (ac = acetylene; cum = cumulene)
contribute to the overall electronic struc-
ture, although the acetylene character of
the Csp–Csp moiety prevails. The detected
chemical shifts of 3 were fairly typical for
acetylene–cumulene porphyrinoids[14,15]
and acetylene–cumulene annulenes.[16]
The structure of 3 was determined by
X-ray diffraction studies and is shown in
Figure 3.[17] The S···S distance is short
Scheme 1. Synthesis of dithiaethyneporphyrin 3: a) PhCOCl, AlCl3, CH2Cl2, RT!reflux, 6 h;
ꢁ
b) NaBH4, THF/MeOH (3:2 V/V); c) conc. HCl; d) BrMgC CMgBr, CuCl, THF, reflux, 2 h;
e) PhCOCl, AlCl3, CH2Cl2, room temperature, 14 h; f) NaBH4, THF/MeOH (3:2 V/V);
g) pyrrole, CH3SO3H, room temperature, 1 h; h) Et3N, DDQ, room temperature, 1.5 h.
DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone.
Figure 1. The electronic spectra of 3 (c, CH2Cl2), 10 (a, CHCl3),
and 11 (b, CH2Cl2).
Figure 2. 1H NMR spectra of a) 3 (CDCl3, 298 K), b) 10 (CDCl3, 240 K),
and c) 11 (CD2Cl2, 298 K). Peak labels correspond to systematic
position numbering or denote proton groups such as o,m,p positions
of the meso-phenyl groups. Chemical shift values are relative to TMS
(tetramethylsilane: d=0 ppm). (°): the intensity of the OCH3 signal
hasbeen decreased by a factor of 5.
Scheme 2. Canonical structures of 3.
electronic structure of 3 can be described as reflecting a
ꢁ
= ꢀ
ꢀ =
ꢀ =
C
combination of acetylene ( C C C C )and cumulene (
= = ꢀ
C C C )character of the C18-C1-C2-C3 fragment. The
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modate RuII binding. Consequently, the two thiophene rings
are severely tilted in opposite directions with respect to the
macrocyclic plane to allow the pyramidal side-on coordina-
tion of ruthenium(ii), in a similar manner as detected for
[(S2TPP)RuIICl2].[21] The puckering of dithiaethyneporphyrin
and the difference in coordination above and below the
porphyrin plane explains the observed lowering of symmetry
of 10 relative to 3. The 2-butyne fragment is not involved in
coordination, as the 13C chemical shifts of non-equivalent
atoms C1 and C2 in 10 (d = 111.1 and 113.7 ppm)resemble
those for 3.
Dithiaethyneporphyrin
methanol (or ethanol)in the presence of silver acetate to
produce iso-8-methoxy-3,8,13,18-tetraphenyl-19,21-dithia-
3 reacts regioselectively with
ethyneporphyrin (11). Derivative 11 is related to a feasible
Figure 3. Crystal structure of dithiaethyneporphyrin 3: a) top and
b) side view (phenyl groups are omitted for clarity). The vibrational
ellipsoids represent 50% probability. The bond lengths in the
Csp2CspCspCsp2 (C18-C1-C2-C3) unit are 1.390(9) Š, 1.231(10) Š, and
1.418(10) Š, respectively. The dihedral angles between the plane
defined by the four meso carbon atoms(C3, C8, C13, C18) and the
planesof the five-membered ringsare asfollows: thiophene(S19)
ꢀ19.0(2)8, pyrrole 17.6(3)8, thiophene(S21) ꢀ18.0(3)8.
non-aromatic isomer of 3, that is, iso-dithiaethyneporphyrin,
iso-3. The UV/Vis spectrum of 11 confirms a loss of
aromaticity, as evident by the smaller extinction coefficients
(3.113(3)Š), and only a small number of compounds that
contain such close sulfur–sulfur contacts have been
reported.[13,18–20] The Csp2-Csp-Csp-Csp2 butyne moiety reveals
a slight distortion from linearity, showing a bowlike deforma-
tion directed outward of the macrocycle (C18-C1-C2:
174.0(9)8; C1-C2-C3: 176.6(9)8).
1
(Figure 1). The H NMR resonances of 11 were detected in
the region that is typical for the conjugated but non-aromatic
system. The 13C NMR shift of C8 (d = 83.1 ppm)is consistent
with its tetrahedral geometry, whereas those of atoms C1 and
C2 (d = 143.8 and 147.2 ppm)comply with a cumulenic
structure. Treatment of 11 with gaseous HCl results in partial
Treatment of 3 with [Ru3(CO)12] in chlorobenzene
resulted in formation of [(S2ETPP)RuII(CO)2Cl] (10) , as recovery of 3.
In conclusion, dithiaethyneporphyrin—a new aromatic
contracted porphyrinoid—has been synthesized and charac-
terized and displays the unique features of an
[18]dithiatriphyrin(4.1.1)frame.
Experimental Section
3: Pyrrole (0.11 mL, 1.58 mmol), 9 (0.9 g, 1.55 mmol), and freshly
distilled CH2Cl2 (750 mL)were placed in a 1-L flask. Nitrogen was
bubbled through the solution for 30 min, then CH3SO3H (0.2 mL,
3.1 mmol)was added, and the mixture was stirred in the dark for 1 h
under N2. Triethylamine (0.49 mL, 3.5 mmol)and DDQ (2.1 g,
9.3 mmol)were added and the solution was stirred for a further
1.5 h. The solvent was partly evaporated, and the reaction mixture
was purified by chromatography on silica gel. The first orange-brown
fraction (product 2)was eluted with dichloromethane and repurified
through a second chromatographic procedure on silica gel with
hexane/benzene (1:1 V/V)as eluant. Product 2 was recrystallized from
CH2Cl2/CH3OH (120 mg, 12.7%); UV/Vis (CH2Cl2): lmax (loge) = 448
(5.2), 518 (4.4), 553 (4.1), 646 (3.4), 725 nm (3.3); 1H NMR (500 MHz,
CDCl3, 298 K, TMS): d = 9.61, 9.29 (AB, 3J(H,H) = 4.4 Hz, 4H;
H5,16, H6,15), 8.96 (d, 3J(H,H) = 7.7 Hz, 4H; 3,18-o-Ph), 8.77 (d,
4J(H,H) = 1.5 Hz, 2H; H10,11), 8.42 (d, 3J(H,H) = 7.7 Hz, 4H; 8,13-o-
confirmed by high-resolution mass spectrometry. The
1H NMR spectrum of complex 10 revealed a lowering of
symmetry relative to 3. The geometry of 10 as inferred from
1
the H NMR spectroscopic pattern (Figure 2b)reflects the
balance between constraints of the macrocyclic ligand and the
coordination requirement of ruthenium(ii)for octahedral
geometry. Dithiaethyneporphyrin 3 has to distort to accom-
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Angewandte
Chemie
Ph), 7.88 (t, 3J(H,H) = 7.7 Hz, 4H; 3,18-m-Ph), 7.85 (t, 3J(H,H) =
7.7 Hz, 4H; 8,13-m-Ph), 7.75 (t, 3J(H,H) = 7.7 Hz, 2H; 8,13-p-Ph),
7.63 (t, 3J(H,H) = 7.7 Hz, 2H; 3,18-p-Ph), ꢀ3.24 ppm (br s, 1H; NH);
HR-MS (ESI): m/z calcd for C42H27N32S2 [M+]: 609.1585; found:
609.1607; elemental analysis: calcd (%)for C 42H27NS2: C 82.27, H
4.65, N 2.50, S 10.45; found: C 82.72, H 4.46, N 2.30, S 10.52.
[11] T. Kawase, S. Muro, H. Kurata, M. Oda, J. Chem. Soc. Chem.
Commun. 1992, 778.
[12] J. P. C. M. van Dongen, M. J. A. de Bie, R. Steur, Tetrahedron
Lett. 1973, 1371.
[13] H. Kurata, H. Baba, M. Oda, Chem. Lett. 1997, 571.
[14] N. Jux, P. Koch, H. Schmickler, J. Lex, E. Vogel, Angew. Chem.
1990, 102, 1429; Angew. Chem. Int. Ed. Engl. 1990, 29, 1385.
[15] D. O. Mµrtire, N. Jux, P. F. Aramendia, R. M. Negri, J. Lex, S. E.
Braslavsky, K. Schaffner, E. Vogel, J. Am. Chem. Soc. 1992, 114,
9969.
10: Compound 3 (20 mg, 0.033 mmol)and [Ru (CO)12] (0.84 g,
3
1.32 mmol)in freshly distilled chlorobenzene (20 mL)were heated at
reflux for 4 h under N2. The solvent was evaporated to dryness and the
residue was purified by chromatography on silica gel. After an initial
orange-red fraction (recovered 3)had been eluted with hexane/
benzene (1:1 V/V), elution with benzene led to a second brown
fraction, which was collected and identified as 10. The second fraction
was purified through a second column (silica gel with hexane/benzene
(1:3 V/V)and recrystallized from CHCl 3/CH3OH to yield the title
product (9 mg, 34%). UV/Vis (CHCl3): lmax (loge) = 367 (4.3), 440
[16] M. Nagawa, Angew. Chem. 1979, 91, 215; Angew. Chem. Int. Ed.
Engl. 1979, 18, 202.
[17] X-ray crystal structure data for 3·CHCl3: crystals were prepared
by slow diffusion of CH3OH into a solution of 3 in CHCl3 to yield
dark brown crystals of C42H27NS2·CHCl3, size 0.22 ” 0.014 ”
0.008 mm3, monoclinic, space group P21/n, a = 14.726(6)Š, b =
8.536(3)Š, c = 27.761(9)Š, b = 105.02(3)8, V= 3370(2)Š 3,
1calcd. = 1.437, Z = 4; Xcalibur PX k-geometry diffractometer,
CuKa radiation (l = 1.5418 Š), T= 100 K, 2qmax = 153.88; total
number of reflections collected: 23091; number of independent
reflections: 6527, of which 6527 were included in the refinement
of 419 parameters; an analytical numeric absorption correction
was applied:[22] m = 3.883 mmꢀ1, Tmin = 0.661, Tmax = 0.972. The
structure was solved by using direct methods with SHELXS-97
and refined against j F2 j using SHELXL-97 (G. M. Sheldrick,
University of Göttingen, Germany, 1997), final R1/wR2 indices
(for I > 2s(I)): 0.0691/0.1108; max/min residual electron density:
+ 0.40/ꢀ0.42 eAꢀ3. The disordered molecule of chloroform is
present. Hydrogen atoms except H20 (NH)were fixed in
idealized positions using the riding model constraints. CCDC-
265651 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
1
(4.5), 505 (4.6), 659 (3.8), 711 nm (3.4); H NMR (500 MHz, CDCl3,
3
240 K, TMS): d = 9.83, 9.78 (AB, J(H,H) = 5.2 Hz, 2H; H15, H16),
3
9.81, 9.67 (AB, J(H,H) = 5.2 Hz, 2H; H5, H6), 8.65 (m, 4H; 3,18-o-
Ph), 8.49 (d, 3J(H,H) = 7.3 Hz, 1H; 13-o-Ph), 8.46 (d, 3J(H,H) =
3
7.3 Hz, 1H; 8-o-Ph), 8.17 (d, J(H,H) = 7.3 Hz, 1H; 8-o-Ph), 8.13 (d,
3J(H,H) = 7.3 Hz, 1H; 13-o-Ph), 8.10, 8.00 (AB, 3J(H,H) = 4.1 Hz,
2H; H10, H11), 7.85 (m, 7H; m-Ph), 7.78 (m, 2H; 8-p-Ph, 13-m-Ph),
7.74 (t, 3J(H,H) = 7.3 Hz, 1H; 13-p-Ph), 7.66 ppm (m, 2H; 3,18-p-Ph);
IR (KBr): n˜ = 2065, 2012 cmꢀ1 (C O); HR-MS (ESI): m/z calcd for
ꢁ
12
C H26NO232S235Cl102Ru [M+]: 801.0311; found: 801.0428; elemental
44
analysis: calcd (%)for C 44H26NO2S2ClRu·0.8CHCl3·1.4CH3OH: C
58.92, H 3.47, N 1.49; found: C 59.10, H 3.79, N 1.10.
11: UV/Vis (CH2Cl2): lmax (loge) = 325 (4.4), 415 (4.6), 649 nm
(3.9); 1H NMR (500 MHz, CD2Cl2, 298 K, TMS): d = 7.77 (d, 3J-
(H,H) = 7.3 Hz, 2H; 3-o-Ph), 7.73 (d, 3J(H,H) = 7.3 Hz, 2H; 18-o-
Ph), 7.67 (d, 3J(H,H) = 7.0 Hz, 2H; 8-o-Ph), 7.54 (d, 3J(H,H) = 7.0 Hz,
2H; 13-o-Ph), 7.49 (m, 3H; 13-m,p-Ph), 7.45 (t, 3J(H,H) = 7.3 Hz, 2H;
18-m-Ph), 7.42 (t, 3J(H,H) = 7.3 Hz, 2H; 3-m-Ph), 7.37 (m, 2H; 3,18-
p-Ph), 7.28 (m, 3H; 8-m,p-Ph), 7.16, 6.89 (AB, 3J(H,H) = 4.0 Hz, 2H;
H15, H16), 7.11, 6.95 (AB, 3J(H,H) = 4.0 Hz, 2H; H5, H6), 6.81, 6.54
(AB, 3J(H,H) = 4.4 Hz, 2H; H10, H11), 3.38 ppm (s, 3H; OCH3);
HR-MS (ESI): m/z calcd for C43H30NO32S2 [MꢀH]+: 640.1769; found:
640.1793.
´
[18] L. Latos-Graz˙ynski, J. Lisowski, L. Szterenberg, M. M. Olm-
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Received: May 12, 2005
Published online: July 25, 2005
[22] Xcalibur PX Software–CrysAlis CCD and CrysAlis RED
version 1.171, Oxford Diffraction Ltd., Poland, Wrocław,
Poland, 1995–2003.
Keywords: annulenes· aromaticity · heterocycles·
NMR spectroscopy · porphyrinoids
.
´
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Angew. Chem. Int. Ed. 2005, 44, 5288 –5291
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