Novel 21,23-ditelluraporphyrins and the first 26,28-ditellurasapphyrin and 30,33-ditellurarubyrin

Article abstract of DOI:10.1021/om100570z

21,23-Ditelluraporphyrins 3, 9, and 16-18 bearing phenyl, 4-methoxyphenyl, and/or 3,4,5-trimethoxyphenyl meso substituents were prepared by the condensation of 2,5-di[hydroxy(aryl)methyl]tellurophenes 12 with 2,5-di[2-pyrrolo(aryl)methyl]tellurophenes 15

Full text of DOI:10.1021/om100570z

Organometallics 2010, 29, 3431–3441 3431
DOI: 10.1021/om100570z
Novel 21,23-Ditelluraporphyrins and the First 26,28-Ditellurasapphyrin
and 30,33-Ditellurarubyrin
Bharathwaj Sathyamoorthy, Abram Axelrod, Victoria Farwell, Stephanie M. Bennett,
Brandon D. Calitree, Jason B. Benedict,* Dinesh K. Sukumaran,* and Michael R. Detty*
Department of Chemistry, University at Buffalo, The State University of New York, Buffalo,
New York 14260-3000
Received June 9, 2010
21,23-Ditelluraporphyrins 3, 9, and 16-18 bearing phenyl, 4-methoxyphenyl, and/or 3,4,
5-trimethoxyphenyl meso substituents were prepared by the condensation of 2,5-di[hydroxy-
(aryl)methyl]tellurophenes 12 with 2,5-di[2-pyrrolo(aryl)methyl]tellurophenes 15 in the presence of
BF3-etherate followed by oxidation with p-chloranil. Compounds 15 were prepared from tellu-
rophenes 12 with pyrrole and BF3-etherate. Tellurophenes 12 were prepared in 44-72% isolated
yield by the addition of 1,6-diarylhexa-2,4-diyn-1,6-diols 13 to the reduction product of Te powder
and LiBHEt3. No additional Lewis acid was necessary in these reactions. Coupling of 1-aryl-
2-propyn-1-ols (14) with CuCl, pyridine, and air in MeOH gave diyndiols 13. 26,28-Ditellurasapphyrin
10 was isolated in 0.6% yield from the reaction mixture that produced 9 in 12% isolated yield. The
X-ray structure of 10 showed a nearly planar sapphyrin core with the Te atoms of both tellurophene
rings pointing to the center of the core. 30,33-Ditellurarubyrin 11 was isolated in 32% yield by the
reaction of two equivalents of trifluoroacetic acid with tellurophene dipyrrane 15c. 125Te NMR
spectra were recorded for the compounds of this study.
Chart 1
Core-modified porphyrins replace one or two pyrrole
N-H groups with O, S, Se, and/or Te atoms. The tellura-
and ditelluraporphyrins provide the broadest range of un-
usual structures and chemical reactivity. 23-Telluraporphyrin
˚
1 (Chart 1) has a Te N distance of 3.13 A, which is less
3 3 3
than the sum of van der Waals radii.1 21-Thia-23-tellurapor-
2
phyrin 2 has a Te S distance of 2.65 A, which is even more
˚
3 3 3
compressed. In 21,23-ditelluraporphyrin 3, the dominant
structure both in solution and in the crystalline state is one
in which the two Te atoms cannot both occupy the core and
one tellurophene is “flipped” with the Te atom pointed away
from the porphyrin core (as represented by 3A and 3B in
Chart 1).3 Telluraporphyrins 1 and 2 are easily oxidized,4
and the close proximity of heteroatoms leads to unusual
bonding interactions within the core with Te in the þ4
oxidation state.5 Telluraporphyrins 1 and 2 are also catalysts
for the activation of H2O2 via oxidation of Te(II) to Te(IV).6
The unusual structure of ditelluraporphyrin 3 gives
reduced symmetry relative to other porphyrins, and core-
modified porphyrins and spectral features of the ditellura-
porphyrin are quite different from those of related struc-
tures. The “flipped” tellurophene of 3 exchanges positions
with the other tellurophene via a dynamic process, which is
observed in temperature-dependent 1H NMR spectra of 3.3
At 210 K, the exchange process has slowed to the point that
the ring protons of the two different tellurophenes are
distinct with a 2 ppm difference in chemical shift.3 Further-
more, the symmetry is unusual for a porphyrin with four
identical meso-substituents with a single mirror plane, as
shown in 3A (Chart 1), as the only symmetry element.
*To whom correspondence should be addressed. Phone: (716) 645-
4228. Fax: (716) 645-6963. E-mail: mdetty@buffalo.edu.
_ ꢀ
(1) Latos-Grazynski, L.; Pacholska, E.; Chmielewski, P. J.;
Olmstead, M. M.; Balch, A. L. Angew. Chem., Int. Ed. Engl. 1995, 34,
2252–2254.
(2) Ulman, A.; Manassen, J.; Frolow, F.; Rabinovich, D. Tetrahe-
dron Lett. 1978, 1885–1886.
(3) Pacholska, E.; Latos-Grazynski, L.; Ciunik, Z. Angew. Chem.,
_ ꢀ
Int. Ed. 2001, 40, 4466–4469.
(4) Abe, M.; Hilmey, D. G.; Stilts, C. E.; Sukumaran, D. K.; Detty,
M. R. Organometallics 2002, 21, 2986–2992.
(5) Abe, M.; Detty, M. R.; Gerlits, O. O.; Sukumaran, D. K. Orga-
nometallics 2004, 23, 4513–4518.
(6) Abe, M.; You, Y.; Detty, M. R. Organometallics 2002, 21, 4546–
4551.
r
2010 American Chemical Society
Published on Web 07/09/2010
pubs.acs.org/Organometallics

3432 Organometallics, Vol. 29, No. 15, 2010
Sathyamoorthy et al.
Chart 2
Consequently, the two ortho- and meta-positions of the meso-
aryl groups have distinct chemical and magnetic environ-
ments, as shown in 3B.
Chart 3
Expanded porphyrin structures such as the sapphyrins7
and rubyrins8 have been described from the traditional Adler
synthesis of porphyrins and have been produced in low yields
under a variety of reaction conditions.9 Core-modified sap-
phyrin analogues of general structures 410,11 and 512 in which
pyrrole nitrogen atoms have been replaced with O, S, and Se
(Chart 2) have been described. An X-ray structure of sele-
nophene-containing analogue 612b (Chart 2) shows the same
selenophene “inversion” in the solid state as found in the
tellurophene “inversion” of ditelluraporphyrin 3.3 Telluro-
phene-substituted sapphyrins might provide some interest-
ing structural variation relative to other analogues.
Core-modified rubyrins 7 (Chart 2) have also been pre-
pared in which two of the rubyrin pyrrole NH groups have
been replaced with O, S, and Se atoms.10a X-ray structural
analysis of crystals of 7b and 7c indicate that the thiophene
and selenophene rings, respectively, are inverted as in 8A
(Chart 2) with the heteroatoms pointing away from the core,
while NMR studies in solution suggest that the predominant
solution structure has the heteroatoms pointing toward the
core. Again, tellurophene-substituted rubyrins might pro-
vide some interesting structural variations relative to other
analogues.
Herein, we describe the synthesis of 5,10,15,20-tetrakis-
(3,4,5-trimethoxyphenyl)-21,23-ditelluraporphyrin (9) and
other methoxyaryl-substituted telluraporphyrins. 26,28-Di-
tellurasapphyrin 10 was isolated as a minor product from the
synthesis of 9, and 30,33-ditellurarubyrin 11 (Chart 3) was
prepared independently. Compounds 10 and 11 represent the
first reported Te-containing sapphyrin and rubyrin analo-
gues. The methoxy substituents in these molecules should
provide precursors to water-soluble analogues, as has been
demonstrated for dithia- and diselenaporphyrins, which
have been evaluated as photosensitizers13 and membrane
probes.14
(7) (a) Bauer, V. J.; Clive, D. L. J.; Dolphin, D.; Paine, J. B., III;
Harris, F. L.; King, M. M.; Loder, J.; Wang, S. C.; Woodward, R. B.
J. Am. Chem. Soc. 1983, 105, 6429–6436. (b) Broadhurst, M. J.; Grigg, R.;
Johnson, A. W. J. Chem. Soc., Perking Trans. 1 1972, 2111–2116.
(8) Sessler, J. L.; Morishima, T.; Lynch, V. Angew. Chem., Int. Ed.
Engl. 1991, 30, 977–980.
Results and Discussion
(9) (a) Geier, G. R., III; Lindsey, J. S. J. Org. Chem. 1999, 64, 1596–
1603. (b) Geier, G. R., III; Ciringh, Y.; Li, F.; Haynes, D. M.; Lindsey, J. S.
Org. Lett. 2000, 2, 1745–1748.
I. Synthesis. 2,5-Di(arylhydroxymethyl)tellurophenes 12 as
Precursors to 21,23-Ditelluraporphyrins. The most successful
synthetic approaches to telluraporphyrins 1-3 are summa-
rized in Scheme 1 and involve 2,5-di(phenylhydroxymethyl)-
tellurophene (12a) as a key intermediate. Tellurophene 12a is
(10) (a) Narayanan, S. J.; Sridevi, B.; Chandrashekar, T. K.; Vij, A.;
Roy, R. J. Am. Chem. Soc. 1999, 121, 9053–9068. (b) Narayanan, S. J.;
Sridevi, B.; Chandrashekar, T. K.; Vij, A.; Roy, R. Angew. Chem., Int. Ed.
1998, 37, 3394–3397.
_ ꢀ
(11) (a) Szterenberg, L.; Latos-Grazynski, L. J. Phys. Chem. A 1999,
103, 3302–3309. (b) Rachlewicz, K.; Sprutta, N.; Chmielewski, P. J.; Latos-
ꢀ
Graz_ynski, L. J. Chem. Soc., Perkin Trans. 2 1998, 969–976.
(13) (a) Detty, M. R.; Gibson, S. L.; Wagner, S. J. Med. Chem. 2004,
47, 3897–3915. (b) Hilmey, D. G.; Abe, M.; Nelen, M. I.; Stilts, C. E.; Baker,
G. A.; Baker, S. N.; Bright, F. V.; Davies, S. R.; Gollnick, S. O.; Oseroff,
A. R.; Gibson, S. L.; Hilf, R.; Detty, M. R. J. Med. Chem. 2002, 45, 449–461.
(14) Minnes, R.; Weitman, H.; You, Y.; Detty, M. R.; Ehrenberg, B.
J. Phys. Chem. B 2008, 112, 3268–3276.
(12) (a) Srinivasan, A.; Pushpan, S.; Kumar, M. R.; Mahajan, S.;
Chandrashekar, T. K.; Roy, R.; Ramamurthy, P. J. Chem. Soc., Perkin
Trans. 2 1999, 961–968. (b) Srinivasan, A.; Anand, V. G.; Narayanan, S. J.;
Pushpan, S.; Kumar, M. R.; Chandrashekar, T. K. J. Org. Chem. 1999, 64,
8693–8697.

Article
Organometallics, Vol. 29, No. 15, 2010 3433
Scheme 1
Scheme 2
prepared from the corresponding hexa-2,4-diyn-1,5-diol 13a.2
Other 2,5-di(1-hydroxy-1-arylmethyl)tellurophenes related in
structure to 12a have not been described.
We examined a general synthesis of 2,5-di(arylhydroxymethyl)-
tellurophenes 12 as shown in Scheme 2. The formal addition of
H2Te across 2,4-diyn-1,6-diols 13 leads directly to telluro-
phenes 12. Diynediols 13 have been prepared by the oxidative
coupling of 1-aryl-1-hydroxy-2-propynes 14 following numer-
ous procedures.15-19 Compounds 14, in turn, have been pre-
pared by the addition of magnesium acetylides to aryl
aldehydes.20 Several of the reported methods15-17 for coupling
alkynols 14 were examined, but diyndiols 13 were isolated in
only 10-35% yields. The most successful coupling procedure
employed was a modification18 of the Hay coupling19 of
terminal alkynes using catalytic Cu(I) and oxygen as the
reoxidant. Diyndiols 13a-c were isolated in 91%, 93%, and
75% isolated yields from 14a-c, respectively, using 0.15 equiv
of CuCl and 0.3 equiv of pyridine in MeOH under aerobic
conditions (Scheme 2).
2,5-Di(1-hydroxy-1-arylmethyl)tellurophenes 12 were pre-
pared by the addition of diyndiols 13 in EtOH to Li2Te prepared
by the reduction of Te powder with 2 equiv of LiBHEt3 in THF
(Scheme 2). Tellurophenes 12a-c were isolated in 44%, 71%,
and 72% yields, respectively. The addition of Na2Te (from
NaBH4 and Te powder) across hexadiyndiol 13a (Scheme 1)
gave 12a in 15% yield and required the presence of the Lewis acid
AgOAc.2 In the absence of AgOAc, the reaction of Na2Te with
13a does not give isolable yields of 12a. However, using Li2Te
prepared from LiHBEt3, no additional Lewis acid catalyst was
necessary. The BEt3 present in the reaction mixture was appa-
rently sufficient as a Lewis acid for the formation of tellurophenes
12 from diynols 13.
The diyndiols 13 and the tellurophene diols 12 have two
chiral centers, and these materials can form racemic mixtures
of two diastereomers. The 1H and 13C NMR spectra of
diynols 13 and tellurophene 12a do not differentiate the
two diastereomers. In contrast, tellurophene diols 12b and
12c show nearly 1:1 mixtures of the two diastereomers in
both the 1H and 13C NMR spectra of these compounds
(Supporting Information). The presence of both diastereo-
mers in 12b and 12c suggests that the NMR spectra of the two
diastereomers fortuitously overlap in the spectra of diyndiols
13 and tellurophene diol 12a rather than having only one
diastereomer present.
Synthesis of 21,23-Ditelluraporphyrins 3, 9, and 16-18.
Ditelluraporphyrin 3 was isolated in only 11% yield from the
Ulman2 synthesis utilizing 12a, pyrrole, BF3-etherate, and
chloranil.3 We examined the [3þ1] approach utilizing 1 equiv
of 12 and the corresponding tellurophene dipyrrane 15 to
prepare 21,23-ditelluraporphyrins.1,2 Telluorphene diols
12a-c gave dipyrranes 15a-c in 94%, 87%, and 99%
isolated yields, respectively, upon reaction with pyrrole in
1
the presence of BF3-etherate (Scheme 2). The H and 13C
NMR spectra of dipyrranes 15a-c suggest either a single
diastereomer or, more likely, that the two possible diaster-
eomers of 15a-c are not differentiated by our conditions for
NMR spectroscopy.
Ditelluraporphyrins 3, 9, and 16-18 were prepared by the
condensation of tellurophene diols 12 with the appropriate
dipyrranotellurophene 15 with BF3 etherate in CH2Cl2
followed by oxidation with p-chloranil (Scheme 2). Tetra-
phenyl analogue 3 was isolated in 34% yield following
reaction of 12a and 15a, which is higher than the 11% yield
previously reported.3 As the number of methoxy substituents
on the meso aryl groups increased, the yield of ditellurapor-
phyrin decreased: 16, with two 4-methoxyphenyl meso-sub-
stituents, was isolated in 28% yield from reaction of 12b and
15a; 17, with four 4-methoxyphenyl groups, was isolated in
19% yield from reaction of 12b and 15b; 18, with two
4-methoxyphenyl and two 3,4,5-trimethoxyphenyl groups,
was isolated in 13% yield from reaction of 12b and 13c; and
9, with four 3,4,5-trimethoxyphenyl groups, was isolated in
12% yield from reaction of 12c and 13c.
The ditelluraporphyrins 9 and 16-18 appeared to be
stable in the crystalline form. However, in CHCl3 or CDCl3
solution, the ditelluraporphyrins were slowly air oxidized to
unknown products.
A second product was isolated from the reaction mixture
that produced 9. 26,28-Ditellurasapphyrin 10 (Chart 2) was
isolated in 0.6% yield as a dark purple powder from the
reaction of 12c and 13c in the presence of BF3-etherate and
chloranil.
(15) Chodkiewicz, W.; Cadiot, P. Compt. Rend. 1955, 241, 1055–
1057.
(16) Eglington, G.; Galbraith, A. R. Chem. Ind. 1936, 737–738.
(17) Lei, A. W.; Srivastava, M.; Zhang, X. M. J. Org. Chem. 2002, 67,
1969–1971.
(18) Stansbury, H. A., Jr.; Proops, W. R. J. Org. Chem. 1962, 27, 320.
(19) (a) Hay, A. S. J. Org. Chem. 1960, 25, 1275–1276. (b) Hay, A. S.
J. Org. Chem. 1962, 27, 3320–3321.
Synthesis of 30,33-Ditellurarubyrin 11. Dipyrrane 15c was
treated with 2 equiv of trifluoroacetic acid followed by
oxidation with p-chloranil10a to give 30,33-ditellurarubyrin
11 (Chart 3) in 32% isolated yield after neutralization with
Et3N. Ditellurarubyrin 11 was not formed in any appreciable
yield under the reaction conditions used to prepare 9 and 10,
(20) Bagley, M. C.; Dale, J. W.; Ohnesorge, M.; Xiong, X.; Bower, J.
J. Comb. Chem. 2005, 5, 41–44.

3434 Organometallics, Vol. 29, No. 15, 2010
Sathyamoorthy et al.
Table 1. Tellurium-125 NMR Chemical Shifts and Absorption Maxima for 21-Telluraporphyrins 1 and 2, 21,23-Ditelluraporphyrins 3, 9,
and 16-18, 26,28-Ditellurasapphyrin 10, and 30,33-Ditellurarubyrin 11
compound
125Te NMR, δa
λ )
max, nm (ε, M-1 cm-1 b
1
2
3
833c
657 (6400), 628 (5500), 534 (11 200), 482 (sh), 438 (76 000)c,d
686 (3700), 626 (4200), 545 (sh), 505 (sh), 445 (71 600)c,d
668 (16 000), 464 (32 000), 348 (25,000)d,e
1039c
9
731.0
730.1
729.0
726.7
731, 1095
685
692 (18 600), 489 (43 700), 385 (34 000)
690 (18 200), 484 (38 000), 385 (29 500)
698 (16 300), 484 (37 000), 385 (26 600)
694 (18 100), 488 (38 000), 385 (27 600)
830 (17 000), 746 (5200), 668 (18 000), 624 (19v000), 584 (11 000), 512 (190 000)
982 (73 000), 865 (7900), 750 (66 000), 692 (35 000), 641 (19 000), 548 (520 000)
16
17
18
10
11
a In CDCl3at 253 K with δ = 0.0 for 125TeMe2. b In CHCl3. c Ref 4. d In CH2Cl2. e ref 3.
The 125Te chemical shift values were nearly identical for 9
and 16-18 (δ 726.7-731.0, Table 1). These values are more
similar to the 125Te chemical shift for tellurophene (δ 793)21
than the 125Te chemical shifts reported for 21-tellurapor-
phyrins 1 (δ 833)4 and 2 (δ 1039).4
1H NMR Spectra. As was reported for the 1H NMR
spectrum of 3,3 the ditelluraporphyrins 9 and 16-18 undergo
conformational changes that are observable on the 1H NMR
time scale. The simplest spectra were recorded for ditellura-
porphyrin 9, as shown in Figure 3 (see Supporting Informa-
tion for 1H NMR spectra of 16-18.) At þ20 °C, the methoxy
groups of 9 appeared as two singlets at δ 4.05 and 3.99
integrating for 12 and 24 protons, respectively. At -20 °C,
these signals separated into four broadened but distinct
signals at δ 4.05, 4.00, 3.98, and 3.95 integrating for 12, 6,
12, and 6 protons, respectively. At þ20 °C, two tellurophene
protons appeared as a broadened singlet (bandwidth at half-
height of >250 Hz) centered at δ 8.6, the four pyrrole
protons appeared as a broadened singlet (bandwidth at
half-height of ∼55 Hz) centered at δ 7.9, the eight aromatic
protons appeared as a broadened singlet centered at δ 7.2
(bandwidth at half-height of ∼55 Hz), and the final two tell-
urophene protons appeared as a broadened singlet (bandwidth at
half-height of >250 Hz) centered at δ 6.2. At -20 °C, the
tellurophene protons appeared as two distinct two-proton, broa-
dened singlets (bandwidth at half-height of ∼20 Hz) centered at δ
8.75 and 5.95, the pyrrole protons appeared as two distinct two-
proton, broadened singlets (bandwidth at half-height of ∼20 Hz)
at δ 8.13 and 7.77, and the eight aromatic protons appeared as a
four-proton, broadened singlet (bandwidth at half-height of
∼20 Hz) at δ 7.40 and two two-proton, broadened singlets
(bandwidth at half-height of ∼20 Hz) at δ 7.05 and 6.95.
13C NMR Spectra. The 13C NMR spectrum of 9 at -20 °C
displayed 18 distinct carbons in the aromatic region (δ 108.7-
166.5), including four signals with very similar chemical shifts in
the δ 152.0-153.5 region as well as three distinct methoxy
carbons (δ 61.3, 61.2, and 56.3, Figure 4). On the basis of the
symmetry elements of 9 as shown in structures 3A and 3B of
Chart 1, one would expect 18 distinct carbon signals in the
aromatic region and up to four methoxy signals if rotation of
the meso-substituents averaged the magnetic environments of
the 13C signals in these substituents.
Figure 1. Electronic spectra of (a) 21,23-ditelluraporphyrin 9
(dashed line, 1.2 ꢀ 10-5 M) and (b) 26,28-ditellurasapphyrin 10
(solid line, 6.3 ꢀ 10-6 M) in CHCl3.
although trace amounts of 11 may have been formed, but in
e0.05% yield by 1H NMR spectroscopy.
II. Characterization of 21,23-Ditelluraporphyrins 9 and
16-18. Electronic Spectra. The electronic spectra of ditel-
luraporphyrins 9 and 16-18 were recorded in CHCl3, and
maxima are reported in Table 1. Three major bands were
observed as illustrated in Figure 1 for ditelluraporphyrin 9 at
385, 489, and 692 nm. The electronic spectra in CHCl3 were
red-shifted 18-34 nm relative to the values reported for 3 in
CH2Cl2 (Table 1).3 While the three bands were comparable
in intensity, the middle band was most intense in all five
ditelluraporphyrins. Noticeably absent was the strong Soret-
like band observed in telluraporphyrin 1 at 438 nm (ε of
76 000 M-1 cm-1) and telluraporphyrin 2 at 445 nm (ε of
71 600 M-1 cm-1, Table 1). The 690-698 nm band in the
21,23-ditelluraporphyrins is much stronger than band 1 for
telluraporphyrins 1 and 2 and for other 21,23-dithia-, 21-thia-
23-selena-, and 21,23-diselenaporphyrins.13b
125Te NMR Spectra. As shown in Figure 2, the 125Te NMR
spectra of 9 and 16-18 displayed a single 125Te resonance at
-20 °C, suggesting that interconversion of “normal” and
“flipped” tellurophenes was sufficiently rapid at -20 °C to
give an averaged 125Te signal. However, at þ20 °C, the 125Te
resonance was broadened in ditelluraporphyrins 17 and 18
and was not detectable in ditelluraporphyrins 9 and 16.
These data are consistent with an exchange process involving
more than two conformations, which has been previously
suggested for the dynamic 1H NMR spectra of ditellurapor-
phyrin 3.3
1H-13C COSY experiments at -20 °C (Supporting In-
formation) indicated that the tellurophene protons in the
two-proton singlets at δ 8.82 and 5.97 were attached to carbons
with 13C chemical shifts δ 142.6 and 159.9, respectively. The
two sets of pyrrole protons in the two-proton signals at δ 8.18
and 7.80 were attached to carbons with 13C chemical shifts δ
135.4 and 134.1, respectively. The asymmetry in the telluro-
phene and pyrrole protons is consistent with having the
(21) Martin, M. L.; Trierweiler, M.; Galasso, V.; Fringuelli, F.;
Taticchi, A. J. Magn. Reson. 1982, 47, 504–506.

Article
Organometallics, Vol. 29, No. 15, 2010 3435
Figure 2. 125Te NMR spectra of 21,23-ditelluraporphyrins 9 at -20 °C and 16-18 at -20 and þ20 °C.
“normal” and “flipped” tellurophenes in the porphyrin core, as
represented by the structure 3A in Chart 1 with relatively slow
interconversion between the two.
III. Characterization of 26,28-Ditellurasapphyrin 10. X-ray
Crystal Structure. Small, thin, green iridescent crystal plates
of 10 were grown by vapor diffusion of ethanol into a
benzene/dichloromethane solution of 10. X-ray data from
the crystals were refined to give the structure shown in
Figure 5. The crystals of 10 contained one benzene and two
dichloromethane molecules of crystallization. Tables of
crystallographic data, atomic coordinates and equivalent
isotropic displacement parameters, anisotropic displace-
ment parameters, and bond lengths and angles for ditellu-
rasapphyrin 10 are compiled in the Supporting Information
(Tables 1S-4S, respectively). The 26,28-ditellurasapphyrin
core has all five tellurophene and pyrrole rings essentially
planar, as shown in Figure 5b. Furthermore, none of the
rings are “flipped”: all heteroatoms in the rings are pointing
toward the interior of the sapphyrin core in the crystal. The
In structure 3B of Chart 1, the two ortho-protons on the
trimethoxyphenyl substituents would find themselves in
different magnetic environments if rotation of the aryl
groups were slow. In the 1H NMR spectrum of 9, the
aromatic protons of the trimethoxyphenyl substituents ap-
peared as a four-proton singlet at δ 7.41 and two two-proton
singlets at δ 7.10 and 6.95, suggesting that one set of ortho-
protons sees a single magnetic environment, while the other
set of ortho-protons sees two different magnetic environ-
1
ments. In H-13C COSY experiments, the protons of the
four-proton singlet were attached to carbons atoms with a
single 13C chemical shift of δ 110.6, while the protons
associated with the two-proton singlets at δ 7.10 and 6.95
were also attached to carbon atoms with a single 13C
chemical shift of δ 108.7. On the 13C NMR time scale,
rotation of the aryl substituents is sufficiently rapid to
average the magnetic environments of the individual 13C
signals. Consequently, one would expect 18 distinct 13C
NMR signals for the telluraporphyrin core, as is observed.
˚
Te1 Te2 distance of 3.468 A, while greater than the sum
3 3 3
˚
of covalent radii (2.6 A), is less than the sum of van der
21
Waals radii for Te (4.12 A). In the tellurophene rings,
˚
˚
Te-C bond lengths were on the order of 2.07-2.08 A and
C-Te-C bond angles were 82.5° and 82.8° at Te1 and Te2,
respectively.

3436 Organometallics, Vol. 29, No. 15, 2010
Sathyamoorthy et al.
Figure 3. 1H NMR spectra (500 MHz) of 21,23-ditelluraporphyrin 9 in CDCl3 at -20 and þ20 °C.
Figure 4. 13C NMR spectrum (125 MHz) of 21,23-ditelluraporphyrin 9 in CDCl3 at -20 °C.
The X-ray structure shows a tautomer of 10 in which the
pyrrole N-H on N1 (position 29) interacts strongly with Te2
but not with Te1. The pyrrole N-H was located from the
difference electron density map, and its position was refined
and is shown in Figure 5a. The Te H-N distance is
3 3 3
˚
2.509 A to the Te2 atom (position 28) and 3.346 A to the
˚
Te1 atom (position 26).
Electronic Spectra. The electronic spectrum of 10 was
recorded in CHCl3, and maxima are reported in Table 1.
Four major bands (ε > 8000 M-1 cm-1) were observed as
shown in Figure 1 at 830, 668, 624, and 512 nm. These values
are all red-shifted relative to 26,28-diselenasapphyrin 5 (822,
630, 590, and 480 nm, respectively).10a
125Te NMR Spectrum. The 125Te NMR spectrum of 26,28-
ditellurasapphyrin 10 at -20 °C displayed two signals (δ 731
and 1095, Table 1) separated by 364 ppm (Figure 6). In the
X-ray structure of 10, the two Te atoms are in different
chemical and magnetic environments. One Te atom is ad-
jacent to a pyrrole N-H and is capable of accepting a
hydrogen bond, while the second Te atom is not. At
-20 °C, the 364 ppm difference in chemical shift between
the two Te atoms is large, but consistent with two different
magnetic and chemical environments for the two Te atoms.
Figure 5. ORTEP drawing with thermal ellipsoids shown at the
50% probability level for the crystal structure of compound 10
viewed (a) from the top and (b) from the side with aryl groups
omitted for clarity. With the exception of the tautomeric hydro-
gen on N1, hydrogen atoms have been omitted for clarity.
Solvents of crystallization have also been omitted for clarity.
The X-ray structure of telluraporphyrin 1 shows Te H-N
3 3 3

Article
Organometallics, Vol. 29, No. 15, 2010 3437
Figure 6. 125Te NMR spectra of (a) 26,28-ditellurasapphyrin 10 and (b) 30,33-ditelluarubyrin 11 at -20 °C.
Figure 7. 1H NMR spectra (500 MHz) of the tellurophene/pyrrole/aromatic region (δ 6.5 to 12) and pyrrole N-H region (δ -4 to -6)
of 26,28-ditellurasapphyrin 10 in CDCl3 at (a) þ20 °C and (b) -20 °C and in CDCl3/D2O at (c) þ20 °C and (d) -20 °C.
interactions, and the 125Te NMR spectrum of 1gives a chemical
shift of δ 833. In contrast, 21-tellura-23-thiaporphyrin 2 cannot
have similar H-bonding interactions, and the 125Te NMR che-
mical shift observed for the Te atom in the tellurophene ring is δ
1039, a difference of 206 ppm. While the two porphyrin structures
are obviously different than the sapphyrin structure, the impact of
the pyrrole N-H appears comparable in a comparison of 125Te
chemical shifts in the three structures 1, 2, and 10.
two-proton singlet at δ 9.35. The aromatic protons at the meso-
positions of 10 appear as two four-proton singlets at δ 7.84 and
7.73 with the downfield signal broadened relative to the upfield
signal. The methoxy singlets appear as two six-proton singlets
at δ 4.33 and 4.30 and as two 12-proton singlets at δ 4.15 and
4.05. The pyrrolic N-H proton is highly shielded, appearing as
a broadened one-proton singlet at δ -4.85 (bandwidth at half-
height of ∼60 Hz) and is removed via exchange with D2O. At
-20 °C, the 1H NMR spectrum of 10 was quite similar to the
spectrum at þ20 °C.
1H NMR Spectra. At þ20 °C, 26,28-ditellurasapphyrin 10
displays two broadened, two-proton singlets at δ 11.13
(bandwidth at half-height of 50 Hz) and δ 10.90 (bandwidth
at half-height >100 Hz) for two different sets of tellurophene
protons (Figure 7). The pyrrole protons appear as two
two-proton doublets at δ 10.17 and 9.61 (J = 4 Hz) and as a
Following D2O exchange, the rate of tautomerization
decreased and eight of the 10 tellurophene/pyrrole protons
appeared with unique chemical shifts (Figure 7). Two of
the four tellurophene protons appeared as two one-proton

3438 Organometallics, Vol. 29, No. 15, 2010
Sathyamoorthy et al.
singlets at δ 11.07 (bandwidth at half-height of 35 Hz) and δ
10.87 (bandwidth at half-height of 35 Hz), while the six
pyrrole protons appeared as three distinct pairs of protons at
δ 10.18 and 10.13, δ 9.65 and 9.58, and δ 9.35 and 9.30 with
bandwidths at half-height of ∼35 Hz for each signal. The
remaining two tellurophene protons appeared as a broa-
dened, two-proton singlet at δ 11.28 (bandwidth at half-
height of 40 Hz). The aromatic protons of the 3,4,5-tri-
methoxyphenyl substituents at the meso-positions of 10
appeared as two four-proton singlets at δ 7.84 and 7.73 with
the downfield signal broadened relative to the upfield signal.
These results suggest that exchange of sites observed in the
absence of D2O is due to N-H tautomerization and not due
to ring-flipping as observed with ditelluraporphyrin 3.3
IV. Characterization of 30,33-Ditellurarubyrin 11. Elec-
tronic Spectra. The electronic spectrum of 30,33-ditellura-
rubyrin 11 was recorded in CHCl3, and maxima are reported
in Table 1. Five major bands (ε g 19, 000 M-1 cm-1) were
observed as shown in Figure 8 at 982, 865, 750, 692, and 641
nm in addition to a strong, Soret-like band at 548 nm (ε
520 000 M-1 cm-1). For the most part, these values are red-
shifted relative to 5,10,19,24-tetraphenyl-30,33-diselenaru-
byrin (7c) in CH2Cl2 (970, 849, 766, 666, and 530 nm).10a
125Te NMR Spectra. At -20 °C, 30,33-ditellurarubyrin 11
displays a single 125Te resonance at δ 685 (Figure 6, Table 1).
This value is at higher field than the 125Te chemical shifts
observed for either 26,28-ditellurasapphyrin 10 or the 21,23-
ditelluraporphyrins 9 and 16-18.
1H NMR Spectra. At þ20 °C, 30,33-ditellurarubyrin 11
displays two broadened, four-proton singlets at δ 11.18
(bandwidth at half-height of 15 Hz) for the tellurophene
protons and δ 10.59 (bandwidth at half-height 15 Hz) for one
set of pyrrole protons (Figure 7). The remaining four pyrrole
protons appeared as a four-proton doublet (J = 4 Hz) at
δ 9.75. The aryl protons of the 3,4,5-trimethoxyphenyl
substituents appeared as an eight-proton singlet at δ 7.95,
and the methoxy signals appeared as a 12-proton singlet at δ
4.34 and as a 24-proton singlet at δ 4.13. The two pyrrolic
N-H protons were apparent as a broad singlet at δ -5.60
(bandwidth at half-height of 800 Hz) and were removed by
exchange with D2O. At -20 °C, the 1H NMR spectrum of 11
was relatively unchanged relative to that at þ20 °C.
Following exchange with D2O, tautomerization of the
N-D deuterons is slower than tautomerization of the pyrrolic
N-H protons prior to exchange. Consequently, the signals for
the tellurophene protons at δ 11.18 and the pyrrole protons at
δ 10.59 and 9.75 are broadened relative to those prior to D2O
exchange. At -20 °C, the broadening is more extensive.
13C NMR Spectra. The 13C NMR spectrum of 11 was
acquired at -20 °C with discrete signals observed at δ 152.5,
137.8, 112.2, 62.0, and 56.9 (Figure 10) corresponding to five
of the six signals expected for the 3,4,5-trimethoxyphenyl
substituents (four different aromatic carbons, two different
methoxy carbons). The remaining 13C signals were contained
in two broadened signals (bandwidth at half-height of 25 Hz)
centered at δ 141 and 133. Following D2O exchange, the
signals at δ 152.5, 137.8, 112.2, 62.0, and 56.9 were un-
changed, but the broadened signals at δ 141 and 133 started
to resolve into several signals.
Summary and Conclusions
We have developed a synthetic approach to 2,5-di(arylhydroxy-
methyl)tellurophenes 12 utilizing the addition of Li2Te to
diyndiols 13. The Li2Te was generated by the reduction of Te
powder with lithium triethylborohydride. No additional Lewis
acid was necessary. The method tolerated not only phenyl sub-
stituents but also 4-methoxphenyl and 3,4,5-trimethoxyphenyl
substituents. The 2,5-di(arylhydroxymethyl)tellurophenes 12
Figure 8. Electronic spectrum of 30,33-ditellurarubyrin 11
(3.8 ꢀ 10-6 M) in CHCl3.
Figure 9. 1H NMR spectra (500 MHz) of 30,33-ditellurarubyrin 11 in CDCl3 at (a) þ20 °C and (b) -20 °C and in CDCl3/D2O at
(c) þ20 °C and (d) -20 °C.

Article
Organometallics, Vol. 29, No. 15, 2010 3439
Figure 10. 13C NMR spectrum (125 MHz) of 30,33-ditellurarubyrin 11 at -20 °C (a) in CDCl3 and (b) in CDCl3/D2O.
Scheme 3
the rings pointing toward the interior of the sapphyrin core.
The ditellurasapphyrin 10 displayed two distinct signals in
the 125Te NMR spectrum separated by ∼350 ppm, perhaps
reflecting the effects of H-bonding from a pyrrole NH (N1 in
Figure 3) to one Te atom (Te2 in Figure 3). In spite of the
influence of the pyrrole N-H, the two tellurophene rings
˚
have comparable Te-C bond lengths of 2.07-2.08 A and
comparable C-Te-C bond angles of 82.5° and 82.8°, which
are “normal” values for tellurophene rings (Table 4S in
Supporting Information).22 The ditellurasapphyrin 10 also
displayed dynamic processes in the 1H and 13C NMR spectra
of the compound, but the rate of these processes slowed
following D2O exchange of the pyrrole NH, suggesting that
the interconversion of pyrrole tautomers is responsible for
the dynamic processes as shown in Scheme 3 (with the 3,4,5-
trimethoxyphenyl groups omitted for clarity).
30,33-Ditellurarubyrin 11 was synthesized independently
from the reaction of dipyrrane 15c with 2 equiv of trifluoro-
acetic acid followed by oxidation with p-chloranil.10a The
ditellurarubyrin 11 displayed one signal in its 125Te NMR
spectrum at 685 ppm. The ditellurarubyrin 11 also displayed
were converted to ditelluraporphyrins 3, 9, and 16-18 by reac-
tion of 12 with the appropriate dipyrranotellurophenes 15 and
BF3-etherate in CH2Cl2 followed by oxidation of the initial
product with p-chloranil (Scheme 2).
The novel 21,23-ditelluraporphyrins 9 and 16-18 dis-
played the same dynamic processes as had been previously
observed with 3 in the temperature-dependent 1H NMR
spectra of these compounds.3 The 125Te NMR spectra of 9
and 16-18 displayed a single peak at -20 °C, suggesting that
the interconversion of “normal” and “flipped” tellurophenes
as shown in Chart 1 was sufficiently rapid at this temperature
to give an averaged signal.
1
dynamic processes in the H and 13C NMR spectra of the
compound, but the rate of these processes slowed following
D2O exchange of the pyrrole NH, suggesting that the interconver-
sion of pyrrole tautomers is responsible for the dynamic processes
as shown in Scheme 4 (with the 3,4,5-trimethoxyphenyl groups
omitted for clarity). The bandwidth at half-height of the pyrrole
NH in 11 is >500 Hz (Figure 9), which is consistent with exchange
at multiple sites.
(22) (a) Fanfani, L.; Nunzi, A.; Zanazzi, P. F.; Zanzari, A. R.;
Pellinghelli, M. A. Cryst. Struct. Commun. 1972, 1, 273–278. (b) Zukerman-
Schpector, J.; Daboub, M. J.; Dadboub, V. B.; Pereira, M. A. Acta Crystallogr.,
Sect. C: Cryst. Struct. Commun. 1992, C48, 767–768. (c) Catalano, D.;
Caporusso, A. M.; Da Settimo, F.; Forte, C.; Veracini, C. A. Gazz. Chim. Ital.
1988, 118, 529–532.
A minor product isolated from the synthesis of 9 was
26,28-ditellurasapphyrin 10, which is a novel heterocyclic
structure. The X-ray structure of 10 has all five tellurophene
and pyrrole rings essentially planar with all heteroatoms in

3440 Organometallics, Vol. 29, No. 15, 2010
Sathyamoorthy et al.
Scheme 4
graphic separation of 10 from the reaction of 7c and 4c described
above was a reddish pink band, which was collected and con-
centrated. The crystalline residue was recrystallized from
CHCl3/EtOH to give 0.008 g (0.6%) of ditellurasapphyrin 10
as dark purple crystals, mp >300 °C: 1H NMR (500 MHz,
CDCl3, 253 K) δ 11.18 (br s, 2 H), 11.02 (br s, 2 H), 10.22 (br s,
2 H), 9.66 (br s, 2 H), 9.39 (br s, 2 H), 7.87 (br s, 4 H), 7.75 (s, 4 H),
4.34 (s, 3 H), 4.31 (s, 3 H), 4.14 (s, 6 H), 4.06 (br s, 6 H), -5.02 (br s,
1 H); 1H NMR (500 MHz, CDCl3/D2O, 253 K) δ 11.30 (br s, 2 H),
11.10 (br s, 1 H), 10.88 (br s, 1 H), 7.87 (br s, 4 H), 7.75 (s, 4 H), 4.34
(s, 3 H), 4.31 (s, 3 H), 4.14 (s, 6 H), 4.06 (br s, 6 H). Anal. Calcd for
C60H55N3O12Te2 CHCl3: C, 52.91; H, 4.08; N, 3.03. Found: C,
3
53.08; H, 4.11; N, 2.97.
5,10,19,24-Tetra(3,4,5-trimethoxyphenyl)-30,33-ditellurarubyrin
(11). Trifluoroacetic acid (0.088 mL, 1.2 mmol) was added to a
stirred solution of dipyrrolotellurophene 15c (0.40 g, 0.60 mmol) in
300 mL of dry, degassed CH2Cl2 in a foil-covered flask. After 2 h,
p-chloranil (0.44 g, 1.8 mmol) was added and the resulting solution
was heated at reflux for 1 h. The reaction mixture was neutralized
with Et3N and concentrated. The residue was purified via chro-
matography on Al2O3 eluted with CHCl3. The first band was
collected and recrystallized from acetone to give 0.13 g (32%) of 11
as shiny green crystals, mp >300 °C (dec): 1H NMR (500 MHz,
CDCl3, 253 K) δ 11.31 (s, 4 H), 10.71 (s, 4 H), 9.88 (d, 4 H, II = 4
Hz), 8.07 (s, 8 H), 4.42 (12 H), 4.21 (s, 24 H), -5.5 (br s, 2 H); 13
C
NMR (125.7 MHz, CDCl3, 253 K) δ152.5, 141 (br), 137.9, 133 (br)
112.2, 62.0, 55.9; MS (ES) m/z 1335 (C64H58N4O12130Te2 þ Hþ:
1335). Anal. Calcd for C64H58N4O12Te2: C, 57.78; H, 4.39; N, 4.21.
Found: C, 57.81; H, 4.44; N, 4.18.
2
2,5-Di(1-hydroxy-1-phenylmethyl)tellurophene (12a). Lithium
triethylborohydride (1.0 M in THF, 18.3 mL, 18.3 mmol) was
added to Te powder (1.17 g, 9.15 mmol) under argon, and the
resulting mixture was stirred for 0.5 h at ambient temperature.
Diyndiol 13a (2.0 g, 7.6 mmol) in 80 mL of degassed EtOH was
added. The resulting mixture was stirred for 4 h. Saturated NH4Cl
(100 mL) was added, and products were extracted with CH2Cl2
(3 ꢀ 75 mL). The combined extracts were washed with brine
(100 mL), dried over MgSO4, filtered through Celite, and concen-
trated. The crude product was precipitated and recrystallized from
a 1:1 solution of CH2Cl2/hexanes to give 1.3 g (44%) of 13a as a
The photophysical properties (quantum yields for triplet
formation and singlet oxygen generation, rates of internal
conversion and intersystem crossing, radiative lifetimes) of
these new Te-containing heterocyclic systems have yet to be
explored. The methoxy substituents provide a handle for
the preparation of water-soluble analogues that may have
potential as photosensitizers13 and membrane probes.14
1
white solid, mp 145-146 °C: H NMR (CD3OD3, 500 MHz) δ
Experimental Section
7.40 (d, 4 H, J = 8 Hz), 7.29 (t, 4 H, J = 8 Hz), 7.23 (t, 2 H, J =
8 Hz), 7.21 (s, 2 H), 5.70 (s, 2 H); 13C NMR (CD3OD, 75 MHz) δ
158.4, 146.7, 133.3, 129.3, 128.5, 127.3, 77.5; HRMS (EI) m/z
376.0105 (calcd for C18H16O2130Teþ - H2O: 376.0101). Anal.
Calcd for C18H16O2Te: C, 55.16; H, 4.11. Found: C, 55.22; H, 4.09.
2,5-Di[hydroxy(4-methoxyphenyl)methyl]tellurophene (12b).
Lithium triethylborohydride (1.0 M in THF, 14.5 mL, 14.5 mmol),
Te powder (0.95 g, 7.5 mmol), and diyndiol 13b (2.0 g, 6.2 mmol) in
100 mL of EtOH were treated as described for the synthesis of 12a
to give 2.0 g (71%) of 12b as a white solid, as a 1:1 mixture of
5,10,15,20-Tetraphenyl-21,23-ditelluraporphyrin (3).3
Borontrifluoride-etherate (0.290 g, 2.04 mmol) was added to
dipyrrolotellurophene 15a (2.00 g, 4.08 mmol) and tellurophene
12a (1.46 g, 4.08 mmol) in 1200 mL of degassed CH2Cl2, and the
reaction mixture was stirred for 1 h in the dark at ambient
temperature. p-Chloranil (4.01 g, 16.3 mmol) was added, and
the resulting mixture was heated at reflux for 1 h in the dark. The
reaction mixture was concentrated, and the product was purified
on basic Al2O3 (CH2Cl2). The first green band was collected,
concentrated, and recrystallized (acetone/MeOH) to give 1.17 g
(34%) of 3 as a dark green solid, mp >300 °C.
5,10,15,20-Tetra(3,4,5-trimethoxyphenyl)-21,23-ditellurapor-
phyrin (9). Dipyrrolotellurophene 15c (0.40 g, 0.60 mmol) and 12c
(0.34 g, 0.60 mmol) in 180 mL of degassed CH2Cl2, BF3-etherate
(0.043 g, 0.30 mmol), and p-chloranil (0.59 g, 2.4 mmol) were
treated as described for the preparation of 3. The first green band
was collected, concentrated, and recrystallized twice from 5:95
EtOH/CHCl3 to give 0.089 g (12%) of 9 as dark green crystals, mp
>300 °C: 1H NMR (500 MHz, CDCl3, 253 K) δ 8.82 (s, 2 H), 8.18
(s, 2H), 7.80(s, 2 H), 7.41(s, 4H), 7.10(s, 2H), 6.95(s, 2H), 5.97(s,
2 H), 4.06 (s, 24 H), 4.01 (s, 6 H), 3.97 (s, 6 H); 13C NMR (125.7
MHz, CDCl3, 253 K) δ 166.5, 159.9, 158.4, 152.9, 152.6, 151.3,
144.2, 142.6, 139.3, 137.2, 136.8, 135.4, 134.1, 132.6, 129.7, 114.9,
110.6, 108.7, 61.3, 61.2, 56.3; HRMS (ES) m/z 1205.1702 (calcd for
C56H52N2O12130Te2 þ Hþ: 1205.1717). Anal. Calcd for C56H52N2-
O12Te2: C, 56.04; H, 4.37; N, 2.33. Found: C, 56.29; H, 4.23; N, 2.33.
5,10,15,20-Tetra(3,4,5-trimethoxyphenyl)-26,28-ditellurasap-
phyrin (10). Preceding the first green band in the chromato-
1
diastereomers by H NMR, mp 121-124 °C: Distinct pairs of
diastereomeric protons and carbons are indicated by * (spectra in
1
Supporting Information); H NMR (400 MHz, CD3OD) δ 7.31
(AA0BB0, 4 H, J = 8 Hz, *), 7.30 (AA0BB0, 4 H, J = 8 Hz, *), 7.18
(s, 2 H, *), 7.17 (s, 2 H, *), 6.85 (AA0BB0, 4 H, J = 8 Hz), 5.66 (s,
2 H), 3.77 (s, 6 H, *), 3.76 (s, 6 H, *); 13C NMR (75 MHz, CD3OD)
δ 160.6, 158.5 (*), 158.4 (*), 138.81 (*), 138.78 (*), 133.2, 128.61 (*),
128.59 (*) 114.7, 77.1, 55.7; HRMS (ES) m/z 477.0331 (calcd For
C20H20O4130Te þ Naþ: 477.0332). Anal. Calcd for C20H20O4Te: C,
53.15; H, 4.46. Found: C, 53.27; H, 4.48.
2,5-Di[hydroxy(3,4,5-trimethoxyphenyl)methyl]tellurophene (12c).
Lithium triethylborohydride (1.0 M in THF, 14.5 mL, 14.5 mmol),
Te powder (0.95 g, 7.5 mmol), and diyndiol 13c (2.7 g, 6.2 mmol) in
100 mL of degassed EtOH were treated as described for the
synthesis of 12a to give 3.7 g (71%) of 12c as a white solid, as a
1:1 mixture of diastereomers by 1H NMR, mp 194-195 °C:
Distinct pairs of diastereomeric protons and carbons are indicated
1
by * (spectra in Supporting Information); H NMR (400 MHz,
CD3OD) δ 7.27 (s, 2 H, *), 7.26 (s, 2 H, *), 6.74 (s, 4 H, *), 6.73 (s,

Article
Organometallics, Vol. 29, No. 15, 2010 3441
4 H, *), 5.66 (s, 2 H, *), 5.65 (s, 2 H, *), 3.81 (s, 12 H, *), 3.79 (s,
12 H, *), 3.73 (s, 6 H, *), 3.72 (s, 6 H, *); 13C NMR (75 MHz,
acetone-d6) δ 158.3 (*), 158.1 (*), 154.3, 142.3, 138.4, 132.4, 104.4,
76.8, 60.44 (*), 60.42 (*), 56.39 (*), 56.38 (*); HRMS (ES) m/z
597.0748 (calcd for C24H26O8130Te þ Naþ: 597.0739). Anal. Calcd
for C24H26O8Te: C, 50.39; H, 4.93. Found: C, 50.47; H, 4.88.
2,5-Di[2-pyrrolo(phenyl)methyl]tellurophene (15a). Borontri-
fluoride-etherate (0.34 g, 2.4 mmol) was added to tellurophene
12a (1.90 g, 4.85 mmol) in degassed pyrrole (60 mL), and the
resulting mixture was stirred for 1 h under argon. The reaction
was diluted with CH2Cl2, and 40% NaOH (25 mL) was added.
The organic layer was separated, washed with water (3 ꢀ 100
mL) and brine (100 mL), dried over MgSO4, and concentrated.
Excess pyrrole was removed via distillation at 50 °C (20 Torr),
and the product was purified on SiO2 (70:30 hexanes/EtOAc) to
give 2.24 g (94%) of 15a as a brown oil that was used without
further purification: 1H NMR (CDCl3, 500 MHz) δ 7.92 (s, 2 H),
7.25 (s, 2 H), 7.25-6.81 (m, 10 H), 6.66 (s, 2 H), 6.12 (s, 2 H), 5.97
(s, 2 H), 5.47 (s, 2 H); 13C NMR (CDCl3, 75 MHz) δ 154.5, 144.4,
134.7, 134.4, 128.6, 128.2, 127.0, 117.7, 117.2, 108.2, 107.1;
HRMS (EI) m/z 492.0847 (calcd for C26H22N2Teþ: 492.0840).
2,5-Di[2-pyrrolo(4-methoxyphenyl)methyl]tellurophene (15b).
Tellurophene 12b (1.50 g, 3.32 mmol), pyrrole (15 mL), and BF3
etherate (0.22 g, 1.6 mmol) were treated as described for 15a to give
1.59 g (87%) of 15b as a brown oil that was used without further
purification: 1H NMR (CDCl3, 400 MHz) δ 7.94 (br s, 2 H), 7.24 (s,
2 H), 7.19 (d, 4 H, J = 7 Hz), 6.82 (d, 4 H, J = 7 Hz), 6.67 (s, 2 H),
6.12 (s, 2 H), 5.97 (s, 2 H), 5.43 (s, 2 H), 3.78 (s, 6 H); HRMS (ES)
m/z 553.1124 (calcd for C28H26N2O2130Te þ Hþ: 553.1129).
2.66 mmol) and 12b (1.20 g, 2.66 mmol) in 1600 mL of degassed
CH2Cl2, BF3 etherate (0.114 g, 0.80 mmol), and p-chloranil (2.61
g, 10.6 mmol) were treated as described for the preparation of 3.
The last green band was repurified via chromatography on basic
Al2O3 (30:70 EtOAc/hexanes) to give 0.34 g (13%) of 19 as dark
green crystals, mp >300 °C, following recrystallization from
acetone/MeOH. 1H NMR (500 MHz, CDCl3, 253 K) δ 8.56 (s,
2 H), 8.13 (br d, 4 H), 8.00 (s, 2 H), 7.62 (s, 2 H), 7.15 (d, 4 H, J =
8.5Hz), 6.99 (s, 2 H), 6.89 (s, 2 H), 6.29 (s, 2 H), 4.05 (s, 6 H), 3.965
(br s, 12 H), 3.945 (br s, 6 H); HRMS (ES) m/z 1101.1279 (calcd.
for C52H44N2O8130Te2 þ HOþ: 1101.1250). Anal. Calcd for
C52H44N2O8Te2: C, 57.82; H, 4.11; N, 2.59. Found: C, 58.01; H,
4.13; N, 2.73.
X-ray Diffraction Data. X-ray diffraction data on 10 were
collected at 90(1) K using a Bruker SMART APEX2 CCD
diffractometer installed at a rotating anode source (Mo KR
˚
radiation, λ = 0.71073 A) and equipped with an Oxford
Cryosystems nitrogen gas-flow apparatus. The data were col-
lected by the rotation method with a 0.5° frame-width (ω scan)
and 60 s exposure time per frame. Four sets of data (360 frames
in each set) were collected for each compound, nominally
covering complete reciprocal space. The data were integrated,
scaled, sorted, and averaged using the APEX2 software
package.22 The structure was solved by direct methods using
SHELXTL version 2008/4.23 The structure was refined by full-
matrix least-squares against F2.
Non-hydrogen atoms were refined anisotropically. Positions
of hydrogen atoms were found by difference electron density
Fourier synthesis. The CH3 hydrogens were treated as part of
idealized CH3 groups with Uiso = 1.5Ueq, while the remainder of
the hydrogen atoms were refined with the “riding” model with
2,5-Di[2-pyrrolo(3,4,5-trimethoxyphenyl)methyl]tellurophene
(15c). Tellurophene 12c (3.00 g, 5.42 mmol), pyrrole (30 mL),
and BF3-etherate (0.22 g, 1.6 mmol) were treated as described
for 15a to give 3.49 g (99%) of 15c as a brown oil that was used
U
iso = 1.2Ueq.
Crystallographic data are compiled in Table 1S in the Sup-
1
without further purification: H NMR (CDCl3, 400 MHz) δ
porting Information. Atomic coordinates, anisotropic displace-
ment parameters, and bond lengths and angles are given in
Tables 2S-4S, respectively, in the Supporting Information.
NMR Spectral Data. The NMR samples were prepared in
CDCl3 in 5 mm NMR tubes. The 125Te NMR spectra were
recorded on a Varian Inova-400 NMR spectrometer at 126.289
MHz and 55 °C. The spectral width for acquisition was set to 320
kHz with an acquisition time of 0.82 s. The data were collected
for 16K transients, with a pulse width of 9 μs and a relaxation
delay of 3-4 s. The FIDs were transformed with an exponential
line broadening function of 10-15 Hz. 1D 1H, 2H, and 13C data
and 2D 1H, 13C-HSQC data were acquired on a Varian Inova-
500 NMR spectrometer using standard Varian pulse sequences
and parameters.
7.96 (br s, 2 H), 7.30 (s, 2 H, J = 4.5 Hz), 6.69 (s, 2 H), 6.51 (s, 4 H),
6.15 (s, 2 H), 6.01 (s, 2 H), 5.40 (s, 2 H), 3.83 (s, 6 H), 3.78 (s, 12 H);
13C NMR (CDCl3, 75 MHz) δ 154.2, 153.3, 140.2, 137.1, 134.2,
134.3, 117.3, 108.4, 107.3, 105.5, 60.9, 56.2, 51.4; HRMS (ES) m/z
695.1363 (calcd for C32H34N2O6130Te þ Naþ: 695.1371).
5,20-Di(4-methoxyphenyl)-10,15-diphenyl-21,23-ditellurapor-
phyrin (16). Dipyrrolotellurophene 15a (2.00 g, 4.08 mmol) and
tellurophene 12b (1.84 g, 4.08 mmol) in 1800 mL of degassed
CH2Cl2, BF3-etherate (0.290 g, 2.04 mmol), and p-chloranil (4.01 g,
16.3 mmol) were treated as described for 3. The first green band was
collected, concentrated, and recrystallized using acetone/MeOH to
give 1.01 g (28%) of 16 as a green solid, mp >300 °C: 1H NMR (500
MHz, CDCl3, 295 K) δ 8.28 (br s, 2 H), 8.08 (br d, J = 8.5 Hz) and
7.92 and 7.75 (br d, J = 4 Hz) [4 o-protons of the 4-methoxyphenyl
and 4 o-protons of the phenyl substituents, 8Htotal], 7.87(brs, 2H),
7.78 (br s, 2 H), 7.59 (t, 4 H, J = 7 Hz), 7.53 (t, 2 H, J = 7 Hz), 7.13
(d, 4 H, J = 8.5 Hz), 6.41 (br s, 2 H), 3.96 (s, 4 H); HRMS (ES) m/z
921.0616 (calcd for C46H32N2O2130Te2 þ HOþ: 921.0626). Anal.
Calcd for C46H32N2O2Te2: C, 61.39; H, 3.58; N, 3.11. Found: C,
61.62; H, 3.91; N, 3.42.
Acknowledgment. This research was supported in part
by the Office of Naval Research (Award No. N0014-09-1-
0217 to M.R.D.) and by the US National Science Foun-
dation (CHE0843922 to J.B.B.).
Supporting Information Available: General experimental de-
tails, synthetic procedures for the preparation of 13a-c and
14a-c, tables of crystallographic data, atomic coordinates and
equivalent isotropic displacement parameters, anisotropic dis-
placement parameters, and bond lengths and angles for 10, 1H
NMR spectra for 16-18, partial 1H-13C COSY spectrum for 9,
HRMS data for 9 and 16-18, and 1H and 13C NMR spectra for
tellurophenes 12b and 12c. This material is available free of
charge via the Internet at http://pubs.acs.org.
5,10,15,20-Tetra(4-methoxyphenyl)-21,23-ditelluraporphyrin
(17). Dipyrrolotellurophene 15b (1.50 g, 2.73 mmol) and 12b (1.23 g,
2.73 mmol) in 1500 mL of degassed CH2Cl2, BF3-etherate (0.19 g,
1.4 mmol), and p-chloranil (2.68 g, 10.9 mmol) were treated as
described for the preparation of 3. The first green band was collected,
concentrated, and recrystallized using acetone/MeOH to give 0.50 g
1
(19%) of 17 as dark green crystals, mp >300 °C: H NMR (500
MHz, CDCl3, 253 K) δ 8.50 (br s, 2 H), 8.10 (br s, 2 H), 7.98 (br s,
2H), 7.68 (br s, 2 H), 7.60 (br s, 2 H), 7.14 (d, 4 H), 6.21 (br s, 2 H),
3.98 (s, 12 H); HRMS (EI) m/z 964.0891 (calcd for C48H36-
N2O2130Te2þ: 964.0800). Anal. Calcd for C48H36N2O2Te2: C,
60.05; H, 3.78; N, 2.92. Found: C, 60.12; H, 3.73; N, 2.89.
(23) APEX2, Area Detector Control and Integration Software, Ver.
2008.4-0; Br€uker Analytical X-ray Systems: Madison, WI. 2008.
(24) SHELXTL, An Integrated System for Solving, Refining and
Displaying Crystal Structures from Diffraction Data, Ver. 2008/4; Br€uker
Analytical X-ray Systems: Madison, WI, 2008.
5,20-Bis(3,4,5-trimethoxyphenyl)-10,15-di(4-methoxyphenyl)-
21,23-ditelluraporphyrin (18). Dipyrrolotellurophene 15c (1.78 g,