Synthesis and properties of heavy chalcogen analogues of the texas reds and related rhodamines

Article abstract of DOI:10.1021/om500346j

Analogues of Texas red incorporating the heavy chalcogens S, Se, and Te atoms in the xanthylium core were prepared from the addition of aryl Grignard reagents to appropriate chalcogenoxanthone precursors. The xanthones were prepared via directed metalation of amide precursors, addition of dichalcogenide electrophiles, and electrophilic cyclization of the resulting chalcogenides with phosphorus oxychloride and triethylamine. The Texas red analogues incorporate two fused julolidine rings containing the rhodamine nitrogen atoms. Analogues containing two half-julolidine groups (a trimethyltetrahydroquinoline) and one julolidine and one half- julolidine were also prepared. The photophysics of the Texas red analogues were examined. The S-analogues were highly fluorescent, the Se-analogues generated single oxygen (¹O₂) efficiently upon irradiation, and the Te-analogues were easily oxidized to rhodamines with the telluroxide oxidation state. The tellurorhodamine telluroxides absorb at wavelengths ～690 nm and emit with fluorescence maxima >720 nm. A mesityl-substituted tellurorhodamine derivative localized in the mitochondria of Colo-26 cells (a murine colon carcinoma cell line) and was oxidized in vitro to the fluorescent telluroxide.

Full text of DOI:10.1021/om500346j

Article
pubs.acs.org/Organometallics
Open Access on 05/02/2015
Synthesis and Properties of Heavy Chalcogen Analogues of the
Texas Reds and Related Rhodamines
Mark W. Kryman,†,§ Gregory A. Schamerhorn,†,§ Jacqueline E. Hill,† Brandon D. Calitree,†
Kellie S. Davies,† Michelle K. Linder,† Tymish Y. Ohulchanskyy,‡ and Michael R. Detty*,†,‡
†Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, United States
‡Institute for Lasers, Photonics and Biophotonics, Department of Chemistry, State University of New York, Buffalo, New York
14260-3000, United States
S
* Supporting Information
ABSTRACT: Analogues of Texas red incorporating the heavy chalcogens S, Se, and Te atoms in the xanthylium core were
prepared from the addition of aryl Grignard reagents to appropriate chalcogenoxanthone precursors. The xanthones were
prepared via directed metalation of amide precursors, addition of dichalcogenide electrophiles, and electrophilic cyclization of the
resulting chalcogenides with phosphorus oxychloride and triethylamine. The Texas red analogues incorporate two fused
julolidine rings containing the rhodamine nitrogen atoms. Analogues containing two “half-julolidine” groups (a
trimethyltetrahydroquinoline) and one julolidine and one “half-julolidine” were also prepared. The photophysics of the Texas
red analogues were examined. The S-analogues were highly fluorescent, the Se-analogues generated single oxygen (1O2)
efficiently upon irradiation, and the Te-analogues were easily oxidized to rhodamines with the telluroxide oxidation state. The
tellurorhodamine telluroxides absorb at wavelengths ≥690 nm and emit with fluorescence maxima >720 nm. A mesityl-
substituted tellurorhodamine derivative localized in the mitochondria of Colo-26 cells (a murine colon carcinoma cell line) and
was oxidized in vitro to the fluorescent telluroxide.
efficiency of fluorescence and their flat, rigid nature, which has
assisted in binding to biopolymers.1−12 Analogues of 1 with
even longer wavelengths of absorbance and emission have been
of interest.12−14
INTRODUCTION
■
The two fused julolidine rings of the rhodamine Texas red (1,
Chart 1) lock the N atoms into conjugation with the
rhodamine xanthylium core leading to longer wavelengths of
absorption. Compound 1 and related structures have found
numerous applications, primarily based on their wavelength and
We have prepared heavy-atom analogues of the tetrame-
thylrosamines/rhodamines (TMR-E, Chart 1)15−17 and ana-
logues incorporating one julolidine group18 and, more recently,
one “half-julolidine” group (a trimethyltetrahydroquinoline,
Chart 1) in the xanthylium core.19 The introduction of a single
fused julolidine or half-julolidine group gives a small increase in
absorption maxima (λmax), but larger shifts in λmax are realized
by replacing the oxygen atom of the xanthylium core with the
heavier chalcogen atoms S, Se, and Te. As the chalcogen atoms
increase in size, the resulting rhodamines have decreasing
quantum yields of fluorescence (ΦFL) and increasing quantum
yields for the generation of triplets and singlet oxygen
[Φ(1O2)].15−18 The synthesis of Texas red derivatives
incorporating the heavier chalcogen atoms S, Se, and Te
should give rhodamine analogues with values of λmax > 600 nm
Chart 1
Received: April 1, 2014
Published: May 2, 2014
© 2014 American Chemical Society
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with control of relative yields for fluorescence and triplet
production for different applications.
RESULTS AND DISCUSSION
■
Synthesis. Our synthetic approach is analyzed in Scheme 1.
A second observation regarding analogues of TMR-Te is the
facile oxidation to the telluroxide oxidation state. The
rhodamine telluroxides absorb at much longer wavelengths
(>60 nm longer) than the reduced forms. Furthermore, the
rhodamine telluroxides are highly fluorescent, while the
reduced tellurorhodamine/rosamines are nonfluorescent.20,21
Tellurium-containing derivatives of 1 should be readily oxidized
to telluroxides with absorption and emission wavelengths in the
near-infrared.
The key to the successful synthesis of TMR-related molecules
or derivatives incorporating a julolidine or half-julolidine was
access to the corresponding chalcogenoxanthones as precursors
to the rhodamine analogues.18,19,22−24 The synthesis of
chalcogenoxanthones is similarly key to this work. Texas red
analogues such as 5−7 can be prepared via the addition of
PhMgBr (or other Grignard or organolithium reagents) to
chalcogenoxanthones 2−4 followed by treatment with acid.
Chalcogenoxanthones 2−4 can be prepared via electrophilic
cyclization of the diaryl chalcogenide intermediates A (Scheme
1) under modified Friedel−Crafts conditions. Structures related
to A have shown a propensity to cyclize para to the amino
substituent under these conditions.19,22−24 Intermediates A can
be prepared via the addition of a diaryl dichalcogenide B
bearing a m-amino substituent to an anion C prepared by
amide-directed metalation.19,22−24
Herein, we describe the synthesis of S-, Se-, and Te-
containing analogues of 1 and related compounds via the
chalcogenoxanthone precursors 2−4 (Chart 2). The Texas red
Chart 2
The specific dichalcogenide precursors B were prepared as
shown in Scheme 2. 3-Bromoaniline (8) was converted to 8-
bromojulolidine (9) using a modification of the literature
procedure used to prepare other 8-substituted julolidines.25
Alkylation of 8 with excess 1-bromo-3-chloropropane at 140 °C
in the presence of Na2CO3 gave dialkylation of 8 in essentially
quantitative yield. The unpurified dialkylation product was
isolated by extraction, dried, and then heated at 160 °C in
anhydrous DMF for 48 h to give 926 in 68% isolated yield
overall. Formation of the Grignard reagent from 9 with Mg
turnings in THF proceeded only when the concentration of 9
in THF was at least 2.0 M. At lower concentrations, the
Grignard reagent either did not form or formed sluggishly.
Elemental S, Se, or Te was then added to the Grignard reagent
from 9 to give the corresponding julolidyl dichalcogenides 10
following air oxidation.
The half-julolidyl analogues 13 were prepared via allylation
of commercially available 3-bromo-N-methylaniline with 1-
chloro-3-methylbut-2-ene in DMF at 95 °C to give aniline 11 in
95% yield (Scheme 2). These conditions are more strenuous
than the literature conditions25 used for the allylation of N-
methylaniline (1-chloro-3-methylbut-2-ene and K2CO3 in
CH3CN at 40 °C) and were necessary to give product
formation. Cyclization of 11 with concentrated H2SO4 gave
tetrahydroquinoline 12.27 The Grignard reagent from 12
reacted with elemental S, Se, or Te to give dichalcogenides
13 following air oxidation.
analogues 5−7 with a 9-phenyl substituent were then prepared
(Chart 2). The S-containing analogues were highly fluorescent,
the Se-containing analogues were an order of magnitude less
fluorescent and generated singlet oxygen (1O2) efficiently upon
irradiation, and the Te-containing analogues were easily
oxidized to the telluroxide oxidation state and absorb at
wavelengths >690 nm and emit with fluorescence maxima >720
nm. Preliminary studies also indicate that tellurorhodamines
localize in the mitochondria of cells and that in vitro oxidation
of a tellurorhodamine and emission from the resulting
telluroxide can be observed in cells in culture.
Chalcogenoxanthones 2−4 were prepared as shown in
Scheme 3. Julolidine-9-carboxamide 1422 was treated with s-
BuLi and TMEDA to give directed ortho-lithiation. Treating the
resulting anion with a diaryl dichalcogenide 10 gave the
Scheme 1
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Scheme 2
dichalcogenide 10-E. This approach gave poorer yields than the
procedure shown in Scheme 3.
Scheme 3
Compounds 2−4 were converted to the Texas red analogues
5−7 (Scheme 2) with PhMgBr in THF followed by work up
with aqueous HPF6 (Table 1). Other 9-substituents should be
readily introduced using other Grignard or organolithium
reagents.15,16,18−22
It should be noted that the directed metalation of 16 gave
only one regioisomer following the addition of the
dichalcogenide electrophile. No product resulting from electro-
philic attack at the carbon next to the gem-dimethyl substituents
was observed. The electrophilic cyclization of intermediates 17
gave only one product−acylation at the para-position relative to
the amino substituent. The synthetic routes to chalcogenox-
anthones 2 and 4 could only lead to one regioisomer in the
directed metalation reaction and, for 2, only one product in the
electrophilic cyclization.
Photophysical Properties. Texas red (1) has an
absorbance maximum, λmax, of 587 nm in MeOH with a
molar extinction coefficient, ε, of 8.5 × 104 M−1 cm−1 (Table
1).1 The Texas red analogues 5 incorporating the heavier
chalcogen analogues have values of λmax at longer wavelengths
(594−617 nm, Table 1). For comparison purposes, values of
λmax and ε in MeOH for the TMR-E analogues (E = O−Se16
and Te15) are also compiled in Table 1. The heavy-chalcogen
analogues 5 of the Texas reds are all red-shifted 20−23 nm
relative to their corresponding TMR-E derivative, and all have
values of ε ≥ 1.24 × 105 M−1 cm−1. Compounds 6 with two
half-julolidine groups are red-shifted 8−9 nm relative to the
corresponding TMR-E analogues, while the red shift of the
unsymmetrical dyes 7 is intermediate at 13−16 nm.
Steady-state fluorescence spectra for 5−7 were acquired with
excitation at 532 nm.16 The emission maxima (λFL) and
quantum yields for fluorescence (ΦFL) for TMR-E (E = O−
Se16 and Te21) and dyes 5−7 are compiled in Table 1. Values
of ΦFL for the S-containing dyes 5-S, 6-S, and 7-S (ΦF = 0.42−
unsymmetrical diaryl chalcogenides 15, which were cyclized to
xanthones 2 with POCl3 and Et3N in CH3CN.23 Similarly,
tetrahydroquinoline carboxamide 1619 was treated with s-BuLi
and TMEDA followed by a diaryl dichalcogenide 13 to give the
unsymmetrical diaryl chalcogenides 17, which were cyclized to
xanthones 3 with POCl3 and Et3N in CH3CN.23 The
unsymmetrical xanthones 4 were prepared from carboxamide
14 and diaryl dichalcogenides 13 via the intermediacy of diaryl
chalcogenides 18. The cyclization of 18 with POCl3 and Et3N
in CH3CN23 gave xanthones 4.
0.53, Table 1) are comparable to ΦFL for TMR-S (ΦF
=
0.44).16 Selenium-containing dyes 5-Se, 6-Se, and 7-Se have
values of ΦFL roughly an order of magnitude smaller than their
corresponding S-analogues (ΦFL = 0.02−0.06, Table 1), and all
are more emissive than TMR-Se (ΦF = 0.009).16 Fluorescence
from all of the Te-containing analogues (TMR-Te, 5-Te, 6-Te,
and 7-Te) is weak (ΦFL < 0.005, Table 1).
1
Quantum yields for the generation of O2 [Φ(1O2)] by 5−7
were evaluated using steady-state 1O2 luminescence with TMR-
Se as a reference [Φ(1O2) = 0.87].16 In Figure 1, the smoothed
luminescence spectra of 1O2 produced by the sensitization of 5-
Alternatively, xanthones 4 were prepared from directed
metalation of 16 followed by treating the resulting anion with a
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Table 1. Synthetic Yields, Absorption Maxima (λmax), and Molar Extinction Coefficients (ε) in CH3OH, Fluorescence Emission
Maxima (λFL) and Quantum Yields for Fluorescence (ΦFL) in CH3OH, Quantum Yields for the Generation of Singlet Oxygen
[Φ(1O2)] in CH3OH for 5-E−7-E, and Values of λmax, ε, and Φ(1O2) for 19-Se and 20-Se
a
a
compd
% yield
λmax (nm)
ε (M−1 cm−1
)
λFL (nm)
ΦFL
0.84
Φ(1O2)
b
TMR-O
550
571
581
8.66 × 104
6.26 × 104
4.4 × 104
575
599
608
0.08
0.21
0.87
b
TMR-S
0.44
b
TMR-Se
0.009
c
c
d
d
TMR-Te
1
597
8.1 × 104
<0.005
0.43
e
e
e
587
8.5 × 104
615
5-S
91
86
92
92
78
75
90
75
89
594
604
617
579
590
607
587
597
610
588
1.24 × 105
1.35 × 105
1.44 × 105
1.04 × 105
1.36 × 105
1.21 × 105
1.20 × 105
1.22 × 105
1.27 × 105
1.26 × 105
621
631
642
606
617
632
614
624
637
0.42
0.06
0.002
0.53
0.03
0.002
0.47
0.02
0.003
<0.05
0.68
0.53
<0.05
0.79
0.47
<0.05
0.81
0.40
0.85
0.88
5-Se
5-Te
6-S
6-Se
6-Te
7-S
7-Se
7-Te
f
19-Se
20-Se
74
585
1.35 × 105
a
b
c
d
e
f
Standard deviation in values is 3%. Ref 16. Ref 15. Ref 20. Ref 1. Ref 18.
1
TMR-Se. Steady-state O2 luminescence emission for the S-
containing dyes 5-S, 6-S, and 7-S was difficult to extract from
the background and the values of Φ(1O2) for the S-containing
compounds are considered to be low [Φ(1O2) < 0.05]. Values
of Φ(1O2) are compiled in Table 1 for TMR-E (E = O−Se16
and Te23) derivatives and dyes 5−7.
The Se-containing analogues TMR-Se, 5-Se, 6-Se, and 7-Se
1
were found to generate O2 more efficiently [Φ(1O2) = 0.68−
0.87] than their corresponding Te-containing analogues TMR-
Te, 5-Te, 6-Te, and 7-Te [Φ(1O2) = 0.40−0.53]. A possible
reason for this can be that as the rate of S1 → T1 intersystem
crossing increases, the heavy atom simultaneously increases the
rate of T1 → S0 nonradiative transition, causing a decrease in
the triplet lifetime that, correspondingly, may decrease the
efficiency of the sensitization of singlet oxygen.28,29 The
1
observed intensity of O2 luminescence could be also affected
1
Figure 1. Luminescence of O2 sensitized with TMR-Se, 5-Se, 5-Te,
6-Se, 6-Te, 7-Se, and 7-Te through excitation at 532 nm (MeOH
solutions). Concentrations of all solutions were adjusted to match OD
= 0.10 at 532 nm.
by other possible interactions of 1O2, which are different for the
Texas red analogues with Se and Te atoms (e.g., possible
formation of exciplexes between O2 and dye molecules).
1
In examining the trends observed on the impact of amine
structure on Φ(1O2) within the Se-containing dyes, incorpo-
ration of the julolidyl fragment lowers Φ(1O2) more than
incorporation of the half-julolidyl fragment. Values for 5-Se, 6-
Se, 5-Te, 6-Se, 6-Te, 7-Se, and 7-Te are compared to the
luminescence spectrum of 1O2 produced by the sensitization of
Scheme 4
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Chart 3
Se, and 7-Se were compared to 19-Se18 incorporating one
julolidyl fragment and 20-Se incorporating one-half-julolidyl
fragment.
Compound 20-Se was prepared as shown in Scheme 4.
Lithiation of amide 16 with s-BuLi/TMEDA followed by the
addition of diselenide 2124 gave diaryl selenide 22 in 46%
isolated yield as the only observed product. Cyclization of 22
with POCl3/Et3N in CH3CN23 gave selenoxanthone 23 in 96%
yield. The addition of PhMgBr to 23 in THF followed by work-
up with aqueous HPF6 gave selenorhodamine 20-Se in 74%
1
isolated yield. The luminescence spectrum of O2 produced by
sensitization with 20-Se was compared to the luminescence
1
spectrum of O2 produced by sensitization of TMR-Se to give
Φ(1O2) of 0.88 (Table 1). The value of Φ(1O2) for 19-Se was
previously determined to be 0.85.18
The selenorhodamine TMR-Se has λmax of 581 nm in
MeOH, while values of λmax for 19-Se and 20-Se were 588 and
585 nm, respectively. The impact of the incorporation of a
single julolidyl or half-julolidyl moiety in the chromophore is
less than half the change observed in λmax for the incorporation
of two. The impact of the incorporation of a single julolidyl or
half-julolidyl moiety on Φ(1O2) is even smaller. Values of
Φ(1O2) for TMR-Se (0.87), 19-Se (0.85), and 20-Se (0.88) are
essentially identical within the 3% error of the experiments.
When both amino groups are constrained in julolidyl or half-
julolidyl fragments, values of Φ(1O2) are lower for 5-Se (0.68)
and 6-Se (0.76) relative to TMR-Se, 19-Se, or 20-Se.
Figure 2. Oxidation of 8 × 10−6 M 5-Te with 3 × 10−3 M H2O2 in
50% aqueous MeOH containing 0.1 M CF3CO2H. After an initial scan
at 0 s, subsequent scans were taken at 960, 1920, 2400, and 3360 s.
functionality displayed increased hydrolytic stability relative to
telluroxide 24 with a 9-phenyl substituent.20 To this end, 9-
mesityltellurorhodamine 27 was prepared in 83% yield by the
addition of the Grignard reagent from 2-bromomesitylene to
telluroxanthone 2-Te at ambient temperature in THF followed
by work-up with aqueous HPF6 (Scheme 5). Tellurorhodamine
27 absorbed light with a λmax of 617 nm and ε of 1.65 × 105
M−1 cm−1 in MeOH (Table 2). Tellurorhodamine 27 was
oxidized to telluroxide 28 with 3 × 10−3 M H2O2 in either pH
7.4 phosphate buffer or in MeOH containing 0.1 M CF3CO2H.
Mesityl-substituted telluroxide 28 was stable with no loss of the
704 nm chromophore (Table 2) after several hours at ambient
temperature.
Similarly, the addition of the Grignard reagent from 2-
bromomesitylene to telluroxanthone 3-Te at ambient temper-
ature in THF followed by work-up with aqueous HPF6 gave
tellurorhodamine 29 in 56% isolated yield (Scheme 5).
Tellurorhodamine 29 absorbed light with a λmax of 606 nm
and an ε of 9.66 × 104 M−1 cm−1 in MeOH (Table 2).
Tellurorhodamine 29 was oxidized with 3 × 10−3 M H2O2 in
either pH 7.4 phosphate buffer or in MeOH containing 0.1 M
CF3CO2H to give telluroxide 30 with a λmax of 692 nm (Table
2). Telluroxide 30 was less stable than telluroxide 28 and was
lost over several hours at ambient temperature in both solvent
systems.
Oxidation of Tellurorhodamines to Tellurorhodamine
Telluroxides. Earlier studies with chalcogenopyrylium dyes
1
show that rates of reaction of O2 with the chalcogen atom in
the dye chromophore is Te ≫ S > Se.30 Our recent studies
show a rapid oxidation of several tellurorhodamines with 1O2 to
give telluroxides 24−26 (Chart 3).20 We examined the
oxidations of 5-Te and 6-Te to the corresponding telluroxides
in two ways. Photooxidation of 8 × 10−6 M 5-Te in air-
saturated 50% aqueous MeOH containing 0.1 M CF3CO2H
with 375−800 nm light from a filtered tungsten lamp (50 mW
cm−2) gave loss of the chromophore for 5-Te (λmax 617 nm)
and appearance of a new chromophore at 716 nm, which was
transiently stable. The oxidation was more conveniently carried
out using H2O2 as an oxidant as shown in Figure 2. Texas red
analogue 5-Te was oxidized with 3 × 10−3 M H2O2 to give
presumably the corresponding telluroxide with λmax of 716 nm
(ε = 1.1 × 105 M−1 cm−1 assuming 100% conversion of 5-Te to
telluroxide) with an isosbestic point at 641 nm. The 716 nm
chromophore was lost upon standing under the conditions of
reaction over a 2-h time period. Attempts to prepare the
telluroxide on a milligram scale resulted decomposition to
many products.20
On a preparative scale, both 27 and 29 were oxidized in 0.1
M CF3CO2D in CD3OD with H2O2 (0.18 M) to allow the
1
acquisition of NMR spectra. For both compounds, H NMR
In our earlier work, tellurorhodamine telluroxides 25 and 26
(Chart 3) substituted with 9-aryl groups with ortho-methyl
spectra were acquired immediately after the addition of H2O2
and showed complete oxidation of the starting tellurorosamine
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Scheme 5
Table 2. Absorption Maxima (λmax), Molar Extinction
Coefficients (ε), Fluorescence Maxima (λFL), and
Fluorescence Quantum Yields (ΦFL) for Tellurorhodamine
27 and 29 and Tellurorhodamine Telluroxides 28 and 30
compd
λmax (nm)
ε (M−1 cm−1
)
λFL (nm)
ΦFL
a
27
617
704
606
692
1.65 × 105
1.35 × 105
9.66 × 104
1.65 × 105
<0.005
0.16
b
28
740
720
a
29
<0.005
0.16
b
30
a
b
In MeOH. In CH3OH containing 0.1 M CF3CO2H.
to telluroxides 28 and 30. For 28, no further changes were
observed over a 1.5-h period. For 30, loss of telluroxide signals
and the appearance of new products were observed over a 1.5-h
period.
Coupling patterns and chemical shifts are similar in the 27/
28 and 29/30 pairs, and 1H NMR spectra for both pairs in 0.1
M CF3CO2D in CD3OD are compiled in the Supporting
Information. Both tellurorosamine dyes 27 and 29 gave 13C
NMR spectra with the expected 19 (11 aromatic and 8
aliphatic) signals. The 13C NMR spectra of telluroxides 28 and
30 were not as well-defined (Supporting Information). All eight
different aliphatic carbons were observed for both compounds,
but only 8 aromatic signals for 28 and 10 aromatic signals for
30 were observed. Acquisition of data was limited by the
stability of the oxidized product. At higher concentrations of
28/30, the rate of loss of 30 was accelerated suggesting second-
order processes for the loss of 30. Solvent addition/elimination
to the telluroxide functionality might also lead to line
broadening on near-by carbons.
Both 28 and 30 were highly emissive. The absorption and
emission spectra of telluroxides 28 and 30 in MeOH containing
0.1 M CF3CO2H are shown in Figure 3. Values of ΦF for 28
and 30 were both 0.16 (Table 2) using Rhodamine 700 as a
known fluorescence standard with ΦF = 0.38.31
Biological Studies: Cellular Oxidation of 27. In our
early work examining telluropyrylium dyes as photosensitizers
for the photodynamic therapy (PDT) of cancer, we noted
mitochondrial fluorescence from the telluroxide oxidation state
following irradiation of dye-treated U-251 MG glioblastoma
cells.32,33 Oxidation of the telluropyrylium dyes via self-
Figure 3. Absorption and fluorescence spectra for (a) tellurorhod-
amine telluroxide 28 and (b) tellurorhodamine telluroxide 30 in
MeOH with 0.1 M CF3CO2H.
sensitized generation of singlet oxygen gave telluroxide
analogues that absorbed and fluoresced at shorter wavelengths
than the reduced form. More recent studies with telluride/
telluroxide20,34 and selenide/selenoxide35 pairs examined
fluorescence from the chromophore substituted with telluroxide
or selenoxide functionality as a probe for redox cycles in living
cells. In the case of telluride/telluroxide pairs based on the
rhodamine core, the telluroxide absorbs and fluoresces at
wavelengths longer than those of the reduced form.19,20
In order to examine the viability of tellurorhodamine 27/
telluroxide 28 as a redox pair indicator in cells, Colo-26 cells (a
murine colon carcinoma cell line) were incubated first with 0.5
μM MitoTracker Green (MTG) for 10 min and then 0.2 μM
tellurorhodamine 27 for an additional 5 min (15 min total for
MTG and 5 min total for 27). The cells were washed prior to
imaging on a fluorescence microscope. The cells were brought
to focus using a halogen lamp, which was used at the end of the
experiment to generate the transmission microscopy image
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shown in Figure 4a. Irradiating the cells with 620 nm light
should oxidize nonfluorescent tellurorhodamine 27 (Figure 4b,
TMR-E and 5-E derivatives (Table 1), but their photophysical
properties are quite similar to those for 5-E.
Incorporating a single julolidine or a single half-julolidine
into the xanthylium core has little impact on the photophysical
properties. Singlet oxygen yields for TMR-Se, 19-Se, and 20-Se
are essentially identical, while values of λmax are between 581
and 587 nm (Table 1).
The tellurium analogues 5-Te and 6-Te are easily oxidized
with 1O2 or H2O2 presumably to the corresponding
telluroxides, but the telluroxide derivatives were hydrolytically
unstable. Texas red analogues 27 and 29 bearing a 9-mesityl
substituent are oxidized to telluroxides 28 and 30, respectively,
which are hydrolytically more stable than the oxidation
products of 5-Te and 6-Te. Both 28 and 30 are highly
fluorescent (ΦF = 0.16 for both). Tellurorhodamine 27 is
oxidized to telluroxide 28 by the self-sensitized generation of
1O2 in cells.
The heavy-chalcogen Texas red analogues can be applied to
several biological problems. The mesityl-substituted telluro-
rhodamine 27 and its corresponding telluroxide 28 represent a
redox-related, nonfluorescent/fluorescent pair of molecules that
can be observed in cells. Fluorescence from telluroxide 28 or
related structures (such as 30) in vitro might allow the tracking
of cellular redox processes.20 The Se-containing analogues 5-Se,
6-Se, and 7-Se as well as related structures have potential as
photosensitizers for the photodynamic therapy (PDT) of
malignant cells17,18,36,37 and as photosensitizers for the
photodynamic purging of blood-borne viral and bacterial
pathogens.38−40 For applications in PDT, the Se-containing
analogues 5-Se, 6-Se, and 7-Se absorb light wavelengths >600
nm, where light penetration of tissue is greatest.40
These versatile chromophores can also be applied to
problems related to solar energy and solar fuels as has been
done with analogues of the TMR-E dyes. Appropriate
substitution in the 9-position of the chromophores would
allow entry into longer-wavelength-absorbing photosensitizers
for dye-sensitized solar cells41,42 and longer-wavelength-
absorbing photosensitizers for the solar reduction of protons
to hydrogen.43 In the latter systems, control of excited state
lifetime (singlet vs triplet) is important, and the suite of Texas
red analogues allows control of both wavelengths of absorption
and singlet−triplet yields.
Figure 4. (a) Transmission microscopy image of Colo-26 cells treated
with MTG and tellurorhodamine 27. (b) Fluorescence microscopy
image of Colo-26 cells before irradiation with 620 30 nm light (t = 0
s). (c) Fluorescence microscopy image of Colo-26 cells from Panel b
after 15 s of irradiation with 620
Fluorescence microscopy image of MTG fluorescence in Colo-26 cells
(excitation with 470 20 nm light). (e) Overlay of images from
30 nm light (t = 15 s). (d)
panels b and d. (f) Overlay of images from panels c and d.
time = 0 s for 620 nm irradiation) via 27-sensitized generation
of 1O2 to give fluorescent telluroxide 28 (Figure 4c, time = 15 s
of irradiation with 620 30 nm light) in the cell. Excitation of
the MTG (470 20 nm light) is shown in Figure 4d. Figure 4e
and f shows the overlays of emission from telluroxide 28 and
the MTG. The images of Figure 4 clearly indicate that the
reduced tellurorhodamine dye 27 is in the Colo-26 cells and
that brief irradiation with 620 nm light gives photooxidation of
27 to fluorescent telluroxide 28 in Figure 4c. The overlay of
MTG emission and telluroxide 28 emission in Figure 4f
indicates that tellurorhodamine 28 is at least partially targeted
to the mitochondria.
EXPERIMENTAL SECTION
■
Preparation of 8-Bromo-1,2,3,5,6,7-hexahydropyrido[3,2,1-
ij]quinoline (9).25,26 3-Bromoaniline (8, 12.7 mL, 116 mmol, 1.0
equiv), sodium carbonate (49.0 g, 465 mmol), and 1-bromo-3-
chloropropane (173 mL, 1.74 mol) were heated at 140 °C for 48 h.
After cooling to room temperature, water (300 mL) was added, and
products were extracted with CH2Cl2 (3 × 200 mL). The combined
organic extracts were dried over anhydrous MgSO4, filtered, and
concentrated. Excess 1-bromo-3-chloropropane was then removed at
45 °C at 1 Torr. The crude dialkylated product was then dissolved in
15 mL of DMF and heated at 160 °C for 48 h. After cooling to room
temperature, 1 M NaOH (250 mL) was added. The resulting mixture
was extracted with diethyl ether (3 × 250 mL). The combined extracts
were dried over anhydrous MgSO4, filtered, and concentrated. The
crude product was recrystallized from MeOH to give 20.0 g (68.2%
CONCLUSIONS
■
We have successfully prepared heavy-chalcogen analogues of
Texas red (1) incorporating S, Se, and Te atoms in the
xanthylium core. The heavy-chalcogen analogues absorb at
longer wavelengths than 1. The excited state of S-containing
analogue 5-S is highly emissive (ΦFL = 0.42), while the excited
state of the Se- and Te-containing derivatives gives intersystem
crossing to the triplet with efficient generation of 1O2 [Φ(1O2)
= 0.68 for 5-Se and 0.53 for 5-Te]. We have also prepared
derivatives 6-E and 7-E incorporating fused trimethyltetrahy-
droquinoline (half-julolidine) in the xanthylium core. These
derivatives give values of λmax that are intermediate between the
1
overall) of 9 as a white solid, mp 31−32 °C: H NMR (500 MHz,
CD2Cl2) δ 6.73 (d, 1 H, J = 7.5 Hz), 6.63 (d, 1 H, J = 8.5 Hz), 3.18−
3.07 (m, 4 H), 2.75 (t, 2 H, J = 6.0 Hz), 2.68 (t, 2 H, J = 6.5 Hz),
2.01−1.90 (m, 4 H); 13C NMR (75.5 MHz, CDCl3) δ 144.5, 127.7,
122.9, 120.6, 120.5, 119.4, 50.0, 49.6, 28.5, 27.6, 21.9, 21.8; HRMS
(ESI, HRDFMagSec) m/z 252.0381 (calcd for C12H14N79Br + H+:
252.0382).
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Article
Preparation of Bisjulolidyl Disulfide 10-S. Compound 9 (2.77
g, 11.0 mmol) and ground Mg turnings (294 mg, 12.1 mmol) in 5.5
mL of THF were heated at reflux for 3 h. The reaction mixture was
cooled to room temperature, and elemental S (388 mg, 12.1 mmol)
and an additional 5.5 mL of THF were added. The resulting mixture
was stirred at room temperature for 3 h before adding 10 mL of 1.0 M
HCl (10 mL) and water (100 mL). The reaction mixture was stirred
overnight under air, and the products were then extracted with ether
(3 × 250 mL). The combined extracts were dried over anhydrous
MgSO4, filtered, and concentrated. The crude product was purified via
column chromatography on SiO2 eluted with 0.5:9.5 EtOAc/hexanes
(Rf = 0.5) to give 1.35 g (60.3%) of 10-S as a yellow solid, mp 107−
sulfate, filtered, and concentrated. The crude product was recrystal-
lized from hot methanol to give 6.26 g (79.5%) of 12 as a brown solid,
mp 55−57 °C: H NMR (500 MHz, CDCl3) δ 7.02 (d, 1 H, J = 8.0
Hz), 6.73 (dd, 1 H, J = 2.0, 8.0 Hz), 6.66 (d, 1 H, J = 2.0 Hz), 3.25 (t,
2 H, J = 6.0 Hz), 2.89 (s, 3 H), 1.73 (t, 2 H, J = 6.0 Hz), 1.25 (s, 6 H);
13C NMR (75.5 MHz, CD2Cl2) δ 147.1, 130.8, 127.4, 120.7, 118.5,
113.4, 47.8, 39.3, 37.1, 32.1, 30.6; HRMS (EI, HRDFMagSec) m/z
253.0456 (calcd for C12H16N79Br+: 253.0461).
1
Preparation of Diaryl Sulfide 13-S. Freshly ground magnesium
turnings (522 mg, 21.5 mmol, 1.1 equiv) were suspended in a stirred
solution of 12 (5.00 g, 19.6 mmol, 1.0 equiv) in THF (30 mL). A
crystal of elemental iodine was added, and the resulting solution was
heated at reflux for 3 h, then cooled to ambient temperature, and
elemental sulfur (628 mg, 19.6 mmol, 1.0 equiv) was added. The
resulting solution was stirred at ambient temperature for 3 h, and then
a solution of 1 M aqueous HCl (30 mL) was added. The mixture was
allowed to stir overnight under air before it was extracted with diethyl
ether (3 × 100 mL), and the combined organic fractions were dried
over anhydrous magnesium sulfate, filtered, and concentrated. The
crude products were purified via column chromatography on SiO2
eluted with 3:7 CH2Cl2/hexanes (Rf = 0.5), to give 2.81 g (70.0%) of
1
108 °C: H NMR (500 MHz, CD2Cl2) δ 6.77 (d, 2 H, J = 7.5 Hz),
6.70 (d, 2 H, J = 8.0 Hz), 3.16−3.06 (m, 8 H), 2.83 (t, 4 H, J = 6.0
Hz), 2.70 (t, 4 H, J = 6.0 Hz), 2.00−1.88 (m, 8 H); 13C NMR (75.5
MHz, CDCl3) δ 143.2, 133.0, 126.9, 120.8, 120.4, 116.3, 50.1, 49.5,
27.6, 25.1, 21.8, 21.6; HRMS (ESI, HRDFMagSec) m/z 408.1690
+
(calcd for C24H28N2S2 : 408.1688).
Preparation of Bisjulolidyl Diselenide 10-Se. The procedure
described for the preparation of 10-S was followed using 9 (5.00 g,
19.8 mmol), Mg turnings (530 mg, 12.1 mmol), and elemental Se
(1.72 mg, 21.8 mmol) in a total of 20 mL of THF. Work-up as
described and purification via chromatography on SiO2 (0.5:9.5
EtOAc/hexanes) gave 2.84 g (57.0%) of 10-Se as an orange solid, mp
1
13-S as a pale yellow solid, mp 66−68 °C: H NMR (500 MHz,
CDCl3) δ 7.08 (d, 2 H, J = 8.0 Hz), 6.81 (dd, 2 H, J = 1.5, 8.0 Hz),
6.72 (d, 2 H, J = 1.5 Hz), 3.21 (t, 4 H, J = 6.0 Hz), 2.84 (s, 6 H), 1.72
(t, 4 H, J = 6.0 Hz), 1.24 (s, 12 H); 13C NMR (75.5 MHz, CDCl3) δ
145.6, 135.6, 130.7, 126.1, 115.6, 110.2, 47.5, 39.1, 37.0, 31.8, 30.7;
1
126−128 °C: H NMR (400 MHz, CDCl3) δ 6.95 (d, 2 H, J = 7.6
Hz), 6.69 (d, 2 H, J = 8.0 Hz), 3.15−3.07 (m, 8 H), 2.83 (t, 4 H, J =
6.4 Hz), 2.73 (t, 4 H, J = 6.4 Hz), 2.01−1.90 (m, 8 H); 13C NMR
(75.5 MHz, CDCl3) δ 143.3, 128.8, 127.2, 121.9, 121.5, 120.5, 50.2,
49.7, 27.7, 27.6, 22.1, 21.9; HRMS (ESI, HRDFMagSec) m/z
505.0649 (calcd for C24H28N280Se2 + H+: 505.0656).
+
HRMS (EI, HRDFMagSec) m/z 412.2008 (calcd for C24H32N2S2 :
412.2001).
Preparation of Diaryl Diselenide 13-Se. The procedure
described for the preparation of 13-S was followed using 12 (2.00 g,
7.87 mmol), Mg turnings (211 mg, 8.66 mmol), and elemental Se
(1.72 g, 21.8 mmol) in a total of 16 mL of THF. Work-up as described
followed by purification via column chromatography on SiO2 eluted
with 2:8 CH2Cl2/hexanes (Rf = 0.4) and recrystallization from hexanes
Preparation of Bisjulolidyl Ditelluride 10-Te. The procedure
described for the preparation of 10-S was followed using 9 (2.00 g,
7.93 mmol), Mg turnings (212 mg, 8.73 mmol), and elemental Te
(1.11 g, 8.73 mmol) in a total of 8 mL of THF. Work-up as described
and purification via recrystallization from CH2Cl2/hexanes gave 1.70 g
(71.4%) of 10-Te as an orange solid, mp 138−139 °C: 1H NMR (500
MHz, CDCl3) δ 7.18 (d, 2 H, J = 8.0 Hz), 6.59 (d, 2 H, J = 8.0 Hz),
3.15−3.06 (m, 8 H), 2.82 (t, 4 H, J = 6.5 Hz), 2.78 (t, 4 H, J = 6.5 Hz),
2.10−1.90 (m, 8 H); 13C NMR (75.5 MHz, CDCl3) δ 143.5, 128.1,
127.5, 124.6, 122.8, 109.5, 50.4, 50.2, 33.5, 28.1, 23.0, 22.4; HRMS (EI,
HRDFMagSec) m/z 604.0354 (calcd for C24H28N2130Te2 + H+:
604.0350).
Preparation of 3-Bromo-N-methyl-N-(3-methylbut-2-enyl)-
aniline (11). 1-Chloro-3-methylbut-2-ene (5.87 mL, 49.5 mmol, 1.5
equiv) was slowly added to a stirred solution of potassium carbonate
(6.84 g, 49.5 mmol, 1.5 equiv) and commercially available 3-bromo-N-
methylaniline (6.45 g, 33.0 mmol, 1.0 equiv) in DMF (30 mL). The
resulting solution was heated to 95 °C for 16 h before it was allowed
to cool to ambient temperature. Water (30 mL) was added, and the
mixture was extracted with diethyl ether (3 × 100 mL). The combined
organic fractions were washed with water (4 × 100 mL), dried over
anhydrous magnesium sulfate, vacuum filtered, and concentrated in
vacuo. The crude products were purified via column chromatography
on SiO2 eluted with 30:70 CH2Cl2/hexanes (Rf = 0.60) to give 8.00 g
(95.3%) of 11 as a yellow oil: 1H NMR (500 MHz, CDCl3) δ 7.05 (t,
1 H, J = 8.0 Hz), 6.83 (t, 1 H, J = 2.0 Hz), 6.79 (d, 1 H, J = 8.0 Hz),
6.59 (dd, 1 H, J = 2.0, 8.0 Hz), 5.16 (m, 1 H), 3.87 (d, 2 H, J = 6.5
Hz), 2.88 (s, 3 H), 1.73 (s, 6 H); 13C NMR (75.5 MHz, CDCl3) δ
150.8, 135.1, 130.2, 123.4, 120.1, 118.8, 115.3, 111.1, 50.2, 37.8, 25.7,
17.9; IR (film on NaCl) νmax 2969, 2913, 1953, 1555, 1494, 1450
cm−1; HRMS (ESI, HRDFMagSec) m/z 253.0459 (calcd for
C12H16N79Br+: 253.0461).
1
gave 1.33 g (66.8%) of 13-Se as an orange solid, mp 76−78 °C: H
NMR (500 MHz, CDCl3) δ 7.05 (d, 2 H, J = 8.0 Hz), 6.92 (dd, 2 H, J
= 1.5, 7.5 Hz), 6.82 (d, 2 H, J = 2.0 Hz), 3.20 (t, 4 H, J = 6.0 Hz), 2.82
(s, 6 H), 1.72 (t, 4 H, J = 6.0 Hz), 1.24 (s, 12 H); 13C NMR (75.5
MHz, CDCl3) δ 145.4, 130.8, 129.0, 125.9, 118.9, 113.7, 47.2, 38.8,
36.7, 31.6, 30.8; HRMS (EI, HRDFMagSec) m/z 508.0895 (calcd for
+
C24H32N280Se2 : 508.0896).
Preparation of Diaryl Ditelluride 13-Te. The procedure
described for the preparation of 13-S was followed using 12 (2.50 g,
9.84 mmol), Mg turnings (263 mg, 10.8 mmol), and elemental Te
(1.72 g, 21.8 mmol) in a total of 20 mL of THF. Workup as described
followed by purification via column chromatography on SiO2 eluted
with 2:8 CH2Cl2/hexanes (Rf = 0.4) and recrystallization from hexanes
1
gave 2.64 g (88.9%) of 13-Te as a dark red solid, mp 85−87 °C: H
NMR (500 MHz, CDCl3) δ 7.08 (dd, 2 H, J = 1.5, 7.5 Hz), 6.98 (d, 2
H, J = 1.5 Hz), 6.94 (d, 2 H, J = 8.0 Hz), 3.19 (t, 4 H, J = 6.0 Hz), 2.81
(s, 6 H), 1.72 (t, 4 H, J = 6.0 Hz), 1.24 (s, 12 H); 13C NMR (75.5
MHz, CDCl3) δ 145.6, 131.4, 126.1, 124.8, 119.9, 105.9, 47.4, 39.0,
36.9, 31.7, 30.7; HRMS (ESI, HRDFMagSec) m/z 609.0758 (calcd for
C24H32N2130Te2 + H+: 609.0763).
Preparation of Diaryl Sulfide 15-S. sec-Butyllithium (1.14 M in
cyclohexane, 3.39 mL, 3.87 mmol) was added dropwise to a stirred
solution of TMEDA (576 μL, 3.87 mmol) and amide 1417 (1.00 g,
3.52 mmol) in THF (70 mL) at −78 °C. A solution of 10-S (1.58 g,
3.87 mmol) in THF (70 mL) at −78 °C was added immediately. The
resulting mixture was stirred at −78 °C for 3 h and then 15 h at room
temperature. A solution of saturated NH4Cl (25 mL) was added, and
the products were extracted with CH2Cl2 (3 × 100 mL). The
combined organic extracts were dried over anhydrous MgSO4, filtered,
and concentrated. The crude product was purified via chromatography
on SiO2 (1:9 Et2O/DCM, Rf = 0.5) to give 765 mg (44.5%) of 15-S as
a yellow oil: 1H NMR (500 MHz, CD2Cl2) δ 6.76 (s, 1 H), 6.60 (d, 1
H, J = 8.0 Hz), 6.01 (d, 1 H, J = 8.0 Hz), 3.78−3.68 (m, 1 H), 3.65−
3.54 (m, 1 H), 3.34−3.20 (m, 4 H), 3.18−3.05 (m, 6 H), 2.74−2.62
(m, 8 H), 2.13−1.93 (m, 6 H), 1.92−1.83 (m, 2 H), 1.72−1.53 (m, 4
H), 1.47−1.32 (m, 2 H); 13C NMR (75.5 MHz, CD2Cl2) δ 168.9,
Preparation of 7-Bromo-1,4,4-trimethyl-1,2,3,4-tetrahydro-
quinoline (12).27 Concentrated sulfuric acid (23.6 mL) was added
dropwise to aniline 11 (7.87 g, 31.0 mmol, 1.0 equiv) at 0 °C. The
resulting mixture was warmed to ambient temperature and was stirred
for 1 h before it was transferred via pipet into water at 0 °C. Sodium
hydroxide pellets were added until the solution was basic to litmus.
The mixture was extracted with ether (4 × 100 mL), and the
combined organic fractions were dried over anhydrous magnesium
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Article
143.8, 143.5, 134.3, 131.3, 126.9, 126.0, 125.2, 124.8, 122.9, 118.5,
118.2, 113.8, 50.5, 50.1, 49.8, 49.7, 48.1, 42.2, 28.1, 27.8, 26.3, 26.1,
25.8, 25.3, 24.9, 22.5, 22.4, 21.9, 21.8; IR (film on NaCl) 2934, 2854,
1630, 1587, 1488, 1438, 1305, 1202 cm−1; HRMS (EI, HRDFMagSec)
m/z 487.2652 (calcd for C30H37ON3S+: 487.2658).
Preparation of Diaryl Telluride 17-Te. sec-Butyllithium (1.19 M
in 92:8 cyclohexane/hexanes, 3.23 mL, 2.88 mmol), TMEDA (429 μL,
2.88 mmol), amide 1621 (750 mg, 2.62 mmol), and 13-Te (1.74 g,
2.88 mmol) in THF (55 + 40 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:19
EtOAc/DCM, Rf = 0.7), 17-Te was isolated in 764 mg (49.6%)
yield as a yellow solid, mp 182−184 °C: 1H NMR (500 MHz, CDCl3)
δ 7.23 (d × d, 1 H, J = 1.0, 7.5 Hz), 7.18 (d, 1 H, J = 1.0 Hz), 7.10−
7.04 (m, 2 H), 6.40 (s, 1 H), 3.60−3.53 (m, 4 H), 3.21 (t, 2 H, J = 6.0
Hz), 3.17 (t, 2 H, J = 6.0 Hz), 1.72−1.65 (m, 4 H), 1.65−1.59 (m, 4
H), 1.26 (s, 6 H), 1.21 (s, 6 H); 13C NMR (75.5 MHz, CDCl3) δ
171.5, 145.9, 145.5, 131.5, 128.7, 127.7, 126.1, 125.1, 123.5, 123.4,
119.8, 115.7, 114.2, 47.2, 46.9, 46.4 (br), 38.9, 37.9, 36.7, 36.2, 31.6,
31.1, 30.4, 30.1, 25.9, 24.4; IR (film on NaCl) 2931, 2852, 1591 cm−1;
HRMS (ESI, HRDFMagSec) m/z 590.2380 (calcd for
C30H41N3O130Te + H+: 590.2385).
Preparation of Diaryl Sulfide 18-S. sec-Butyllithium (1.00 M in
92:8 cyclohexane/hexanes, 3.87 mL, 3.87 mmol), TMEDA (577 μL,
3.87 mmol), amide 1417 (1.00 g, 3.52 mmol), and 13-S (1.60 g, 3.87
mmol) in THF (2 × 60 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:9 Et2O/
CH2Cl2, Rf = 0.5), 18-S was isolated in 992 mg (55.4%) yield as a
white solid, mp 141−143 °C: 1H NMR (500 MHz, CDCl3) δ 6.94 (d,
1 H, J = 8.0 Hz), 6.69 (s, 1 H), 6.44 (s, 1 H), 6.30 (d, 1 H, J = 8.0 Hz),
3.72−3.65 (m, 1 H), 3.63−3.55 (m, 1 H), 3.22−3.05 (m, 7 H), 3.04−
2.89 (m, 2 H), 2.80 (s, 3 H), 2.78−2.68 (m, 3 H), 2.02−1.90 (m, 2 H),
1.87 (quintet, 2 H, J = 6.0 Hz), 1.70 (t, 2 H, J = 6.0 Hz), 1.62−1.44
(m, 4 H), 1.32−1.23 (m, 2 H), 1.20 (s, 3 H), 1.19 (s, 3 H); 13C NMR
(75.5 MHz, CDCl3) δ 169.0, 145.1, 143.2, 134.8, 130.3, 128.2, 125.7,
125.6, 125.2, 124.1, 122.1, 114.6, 109.4, 49.5, 49.1, 47.6, 47.1, 41.7,
38.8, 36.8, 31.2, 30.5, 30.4, 27.4, 25.6, 25.4, 25.0, 24.1, 21.3, 21.2; IR
(film on NaCl) 2934, 2853, 1630, 1590, 1552, 1500, 1438 cm−1;
HRMS (ESI, HRDFMagSec) m/z 490.2878 (calcd for C30H39N3OS +
H+: 490.2887).
Preparation of Diaryl Selenide 15-Se. sec-Butyllithium (1.03 M
in cyclohexane, 1.88 mL, 1.93 mmol), TMEDA (288 μL, 1.93 mmol),
amide 1417 (500 mg, 1.76 mmol, 1.0 equiv), and 10-Se (972 mg, 1.93
mmol) in THF (2 × 35 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:9 Et2O/
DCM, Rf = 0.5), 15-Se was isolated in 450 mg (47.9%) yield as a
yellow oil: 1H NMR (500 MHz, CD2Cl2) δ 6.73 (s, 1 H), 6.54 (d, 1 H,
J = 8.0 Hz), 6.09 (d, 1 H, J = 8.5 Hz), 3.76−3.68 (m, 1 H), 3.59−3.51
(m, 1 H), 3.29−3.07 (m, 10 H), 2.86−2.71 (m, 6 H), 2.70−2.62 (m, 2
H), 2.08−1.91 (m, 6 H), 1.86 (quintet, 2 H, J = 6.5 Hz), 1.69−1.52
(m, 4 H), 1.42−1.30 (m, 2 H); 13C NMR (75.5 MHz, CD2Cl2) δ
169.8, 143.9, 143.8, 131.9, 131.4, 127.3, 126.1, 124.8, 123.4, 122.9,
119.8, 119.3, 116.1, 54.2, 50.5, 50.2, 49.9, 48.3, 42.3, 28.6, 28.2, 27.8,
27.0, 26.5, 25.8, 25.0, 22.5, 22.4, 22.3, 22.0; IR (film on NaCl) 2934,
2854, 1627, 1596, 1502, 1461, 1437, 1390, 1316, 1304, 1262, 1211
cm−1; HRMS (ESI, HRDFMagSec) m/z 536.2184 (calcd for
C30H37ON380Se + H+: 536.2175).
Preparation of Diaryl Telluride 15-Te. sec-Butyllithium (1.08 M
in cyclohexane, 3.58 mL, 3.52 mmol), TMEDA (576 μL, 3.87 mmol),
amide 1417 (1.00 g, 3.52 mmol, 1.0 equiv), and 10-Te (2.32 g, 3.87
mmol) in THF (2 × 70 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:9 Et2O/
DCM, Rf = 0.5), 15-Te was isolated in 763 mg (37.2%) yield as a
yellow oil: 1H NMR (500 MHz, CD2Cl2) δ 6.75 (s, 1 H), 6.51 (d, 1 H,
J = 8.0 Hz), 6.37 (d, 1 H, J = 8.0 Hz), 3.80−3.55 (m, 2 H), 3.40−3.26
(m, 2 H), 3.23 (t, 2 H, J = 6.0 Hz), 3.18−3.05 (m, 6 H), 3.00−2.76
(m, 4 H), 2.74−2.55 (m, 4 H), 2.07−1.92 (m, 6 H), 1.89−1.80 (m, 2
H), 1.75−1.51 (m, 4 H), 1.4−1.38 (m, 2H); 13C NMR (75.5 MHz,
CD2Cl2) δ 171.3, 143.9, 143.1, 134.3, 127.8, 127.5, 124.5, 123.1, 122.8,
121.5, 120.4, 118.4, 114.2, 50.4, 50.1, 50.0, 49.9, 48.4, 42.5, 33.8, 31.0,
28.1, 27.8, 26.6, 25.7, 24.9, 22.7, 22.4, 22.3, 22.0; IR (film on NaCl)
2934, 2852, 1623, 1582, 1486, 1436, 1388, 1328, 1305, 1202 cm−1;
HRMS (ESI, HRDFMagSec) m/z 586.2073 (calcd for
C30H37ON3130Te + H+: 586.2072).
Preparation of Diaryl Sulfide 17-S. sec-Butyllithium (0.94 M in
92:8 cyclohexane/hexanes, 4.09 mL, 3.84 mmol), TMEDA (572 μL,
3.84 mmol), amide 1621 (1.00 g, 3.49 mmol), and 13-S (1.58 g, 3.84
mmol) in THF (2 × 70 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:9 EtOAc/
CH2Cl2, Rf = 0.6), 17-S was isolated in 1.06 g (61.6%) yield as a yellow
solid, mp 83−85 °C: 1H NMR (500 MHz, CDCl3) δ 7.07 (d, 1 H, J =
8.0 Hz), 7.00 (s, 1 H), 6.68−6.62 (m, 2 H), 6.43 (s, 1 H), 3.66 (br s, 2
H), 3.26−3.04 (m, 6 H), 2.84 (s, 3 H), 2.73 (s, 3 H), 1.76−1.66 (m, 4
H), 1.63−1.44 (m, 6 H), 1.24 (s, 12 H); 13C NMR (MHz, CDCl3) δ
168.8, 145.1, 132.3, 131.1, 130.0, 129.5, 125.6, 125.2, 123.7, 119.2,
113.7, 112.9, 47.5 (br), 47.0, 46.8, 42.1 (br), 38.7, 38.4, 36.6, 36.2,
31.3, 31.2, 30.3, 30.1, 25.4 (br), 24.1; IR (film on NaCl) 2931, 2852,
1630, 1593, 1501, 1467, 1434 cm−1; HRMS (ESI, HRDFMagSec) m/z
492.3035 (calcd for C30H41N3OS + H+: 492.3043).
Preparation of Diaryl Selenide 17-Se. sec-Butyllithium (1.19 M
in 92:8 cyclohexane/hexanes, 3.23 mL, 3.84 mmol), TMEDA (572 μL,
3.84 mmol), amide 1621 (1.00 g, 3.49 mmol), and 13-Se (1.94 g, 3.84
mmol) in THF (2 × 55 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 (1:9 Et2O/
CH2Cl2, Rf1 = 0.6), 17-Se was isolated in 1.04 g (55.3%) yield as a
yellow oil: H NMR (500 MHz, CDCl3) δ 7.07 (d, 1 H, J = 7.5 Hz),
6.99 (s, 1 H), 6.86−6.78 (m, 2 H), 6.43 (s, 1 H), 3.44 (br s, 4 H), 3.18
(quintet, 4 H, J = 6.0 Hz), 2.83 (s, 3 H), 2.65 (s, 3 H), 1.71 (t, 2 H, J =
6.0 Hz), 1.68 (t, 2 H, J = 6.0 Hz), 1.64−1.57 (m, 2 H), 1.57−1.48 (m,
4 H), 1.23 (s, 6 H), 1.21 (s, 6 H); 13C NMR (75.5 MHz, CDCl3)
169.6, 145.3, 130.7, 128.9, 128.6, 127.4, 125.8, 124.8, 123.8, 122.1,
116.7, 113.7, 47.1, 46.9, 45.0 (br), 38.7, 38.2, 36.6, 36.3, 31.4, 31.2,
30.3, 30.1, 25.6, 24.2; IR (film on NaCl) 2930, 1627, 1593, 1499, 1467,
1430 cm−1; HRMS (ESI, HRDFMagSec) m/z 562.2330 (calcd for
C30H41N3O80Se + Na+: 562.2307).
Preparation of Diarylselenide 18-Se. sec-Butyllithium (1.23 M
in 92:8 cyclohexane/hexanes, 3.15 mL, 3.87 mmol), TMEDA (577 μL,
3.87 mmol), amide 1417 (1.00 g, 3.52 mmol), and 13-Se (1.96 g, 3.87
mmol) in THF (2 × 40 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 eluted with
2:9 EtOAc/CH2Cl2, (Rf = 0.5), 18-Se was isolated in 1.21 g (64.0%)
1
yield as a red solid, mp 55−57 °C: H NMR (500 MHz, CDCl3) δ
6.93 (d, 1 H, J = 8.0 Hz), 6.68 (s, 1 H), 6.54 (d, 1 H, J = 1.5 Hz), 6.43
(dd, 1 H, J = 1.5, 8.0 Hz), 3.78−3.66 (m, 1 H), 3.62−3.51 (m, 1 H),
3.22−3.12 (m, 5 H), 3.11−3.05 (m, 2 H), 3.04−2.97 (m, 1 H), 2.89−
1.89 (m, 2 H), 2.76 (s, 3 H), 2.72−2.68 (m, 2 H), 2.00−1.89 (m, 2 H),
1.82 (m, 2 H), 1.70 (m, 2 H), 1.65−1.43 (m, 4 H), 1.34−1.21 (m, 2
H), 1.20 (s, 3 H), 1.19 (s, 3 H); 13C NMR (75.5 MHz, CDCl3) δ
170.2, 145.7, 143.4, 131.2, 130.4, 129.3, 126.2, 126.0, 124.3, 123.9,
122.4, 117.5, 112.1, 49.9, 49.6, 48.0, 47.6, 42.1, 39.2, 37.2, 31.7, 30.9,
30.8, 28.5, 27.8, 25.9, 25.4, 24.5, 21.9, 21.6; IR (film on NaCl) 2933,
2853, 1628, 1587, 1499 cm−1; HRMS (ESI, HRDFMagSec) m/z
537.2254 (calcd for C30H39N3O80Se+: 537.2253).
Preparation of Diaryltelluride 18-Te. sec-Butyllithium (0.94 M
in 92:8 cyclohexane/hexanes, 1.23 mL, 1.16 mmol), TMEDA (173 μL,
1.16 mmol), amide 1417 (300 mg, 1.05 mmol), and 13-Te (700 mg,
1.16 mmol) in THF (2 × 40 mL) were treated as described for the
preparation of 15-S. Following chromatography on SiO2 eluted with
1:9 EtOAc/CH2Cl2, (Rf = 0.5), 18-Te was isolated in 233 mg (37.9%)
1
yield as a light brown solid, mp 81−83 °C: H NMR (500 MHz,
CDCl3) δ 6.90 (d, 1 H, J = 8.0 Hz), 6.72 (s, 1 H), 6.70−6.63 (m, 2 H),
3.66 (br s, 2 H), 3.32−3.10 (m, 7 H), 3.07 (t, 2 H, J = 5.5 Hz), 2.99−
2.87 (m, 1 H), 2.79 (s, 3 H), 2.74 (t, 2 H, J = 6.5 Hz), 1.93 (quintet, 2
H, J = 6.0 Hz), 1.83 (quintet, 2 H, J = 6.0 Hz), 1.71 (t, 2 H, J = 5.5
Hz), 1.66−1.50 (m, 4 H), 1.42−1.33 (m, 2 H), 1.21 (s, 6 H); 13C
NMR (75.5 MHz, CDCl3) δ 171.7, 145.7, 142.7, 133.6, 130.2, 127.3,
126.3, 123.9, 123.4, 117.7, 114.0, 113.6, 49.7, 49.6, 48.2 (br), 47.4, 42.3
(br), 39.0, 37.0, 33.7, 31.6, 30.7, 27.7, 26.1 (br), 25.2 (br), 24.4, 22.2,
21.4; IR (film on NaCl) 2932, 2852, 1623, 1582, 1546, 1497, 1434
cm−1; HRMS (ESI, HRDFMagSec) m/z 588.2231 (calcd for
C30H39N3O130Te+: 588.2228).
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Preparation of Bisjulolidyl Thioxanthone 2-S. Phosphorus
oxychloride (1.73 mL, 18.6 mmol) was added dropwise to a solution
of triethylamine (2.59 mL, 18.6 mmol) and 15-S (755 mg, 1.55 mmol)
in anhydrous CH3CN (50 mL). The resulting mixture was heated at
reflux for 12 h and was then cooled to 0 °C. A solution of 1 M NaOH
(10 mL) was added slowly, and the resulting mixture was poured into
a stirred solution of cold 1 M NaOH (200 mL). The resulting mixture
was stirred for 6 h, and products were then extracted with CH2Cl2 (3
× 250 mL). The combined organic extracts were dried over anhydrous
MgSO4, filtered, and concentrated. The resulting solid was recrystal-
lized from CH2Cl2/hexanes to give 511 mg (82.0%) of 2-S as a brown
mL, 13.8 mmol), and 17-Te (677 mg, 1.15 mmol) in anhydrous
CH3CN (25 mL) were treated as described for the preparation of 2-S.
The crude product was recrystallized from CH2Cl2/hexanes to give
1
507 mg (87.4%) of 3-Te as a brown solid, mp >250 °C: H NMR
(500 MHz, CDCl3) δ 8.57 (s, 2 H), 6.64 (s, 2 H), 3.36 (t, 4 H, J = 6.0
Hz), 2.98 (s, 6 H), 1.75 (t, 4 H, J = 6.0 Hz), 1.34 (s, 12 H); 13C NMR
(75.5 MHz, CDCl3) δ 183.2, 147.1, 131.0, 129.3, 122.6, 118.9, 112.3,
47.2, 38.7, 36.0, 31.7, 29.8; IR (film on NaCl) 2924, 1585 cm−1;
HRMS (ESI, HRDFMagSec) m/z 505.1500 (calcd for
C25H30N2O130Te + H+: 505.1493).
Preparation of Julolidyl/Half-julolidyl Thioxanthone 4-S.
Phosphorus oxychloride (1.72 mL, 18.4 mmol), triethylamine (2.56
mL, 11.0 mmol), and 18-S (750 mg, 1.53 mmol) in anhydrous
CH3CN (30 mL) were treated as described for the preparation of 2-S.
The crude product was recrystallized from CH2Cl2/hexanes to give
538 mg (86.9%) of 4-S as a brown solid, mp >250 °C: 1H NMR (500
MHz, CDCl3) δ 8.37 (s, 1 H), 8.10 (s, 1 H), 6.50 (s, 1 H), 3.37 (t, 2
H, J = 6.0 Hz), 3.28−3.21 (m, 4 H), 3.00 (s, 3 H), 2.85 (t, 2 H, J = 6.5
Hz), 2.75 (t, 2 H, J = 6.5 Hz), 2.05 (quintet, 2 H, J = 6.5 Hz), 1.96
(quintet, 2 H, J = 6.5 Hz), 1.75 (t, 2 H, J = 6.0 Hz), 1.35 (s, 6 H); 13C
NMR (75.5 MHz, CDCl3) δ 177.5, 147.1, 144.9, 136.3, 134.6, 130.3,
127.4, 125.5, 119.5, 117.8, 117.7, 112.2, 103.7, 49.7, 48.9, 46.9, 38.5,
35.7, 31.6, 29.5, 27.4, 23.7, 21.1, 20.7; IR (film on NaCl) 2931, 1592,
1573, 1513, 1421 cm−1; HRMS (ESI, HRDFMagSec) m/z 404.1917
(calcd for C25H28N2OS+: 404.1917).
Preparation of Julolidyl/Half-julolidyl Selenoxanthone 4-Se.
Phosphorus oxychloride (2.46 mL, 26.4 mmol), triethylamine (3.68
mL, 26.4 mmol), and 18-Se (1.18 g, 2.20 mmol) in anhydrous
CH3CN (40 mL) were treated as described for the preparation of 2-S.
The crude product was recrystallized from CH2Cl2/hexanes to give
610 mg (61.4%) of 4-Se as a brown solid, mp >250 °C: 1H NMR (500
MHz, CDCl3) δ 8.43 (s, 1 H), 8.14 (s, 1 H), 6.55 (s, 1 H), 3.31 (t, 2
H, J = 6.0 Hz), 3.22−3.13 (m, 4 H), 2.94 (s, 3 H), 2.80 (t, 2 H, J = 6.0
Hz), 2.63 (t, 2 H, J = 6.0 Hz), 2.00 (quintet, 2 H, J = 6.0 Hz), 1.91
(quintet, 2 H, J = 6.0 Hz), 1.70 (t, 2 H, J = 6.0 Hz), 1.32 (s, 6 H); 13C
NMR (75.5 MHz, CDCl3) δ 179.8, 147.3, 145.4, 134.1, 133.9, 130.7,
129.4, 127.3, 119.9, 119.5, 119.4, 114.4, 106.3, 50.0, 49.2, 47.2, 38.8,
36.0, 31.8, 29.7, 27.5, 25.5, 21.3, 21.2; IR (film on NaCl) 2930, 1589,
1569, 1514 cm−1; HRMS (ESI, HRDFMagSec) m/z 453.1432 (calcd
for C25H28N2O80Se + H+: 453.1440).
Preparation of Julolidyl/Half-julolidyl Telluroxanthone 4-Te.
Phosphorus oxychloride (306 μL, 3.28 mmol), triethylamine (457 μL,
3.28 mmol), and 18-Te (160 mg, 0.273 mmol) in anhydrous CH3CN
(20 mL) were treated as described for the preparation of 2-S. The
crude product was recrystallized from CH2Cl2/hexanes to give 83.0 mg
(60.6%) of 4-Te as a brown solid, mp >250 °C: 1H NMR (300 MHz,
CD2Cl2) δ 8.47 (s, 1 H), 8.17 (s, 1 H), 6.74 (s, 1 H), 3.32 (t, 2 H, J =
6.0 Hz), 3.26−3.14 (m, 4 H), 2.95 (s, 3 H), 2.83 (t, 2 H, J = 6.3 Hz),
2.53 (t, 2 H, J = 6.3 Hz), 2.06−1.86 (m, 4 H), 1.72 (t, 2 H, J = 6.0 Hz),
1.34 (s, 6 H); 13C NMR (75.5 MHz, CDCl3) δ 183.6, 147.6, 146.0,
131.7, 131.6, 129.0, 122.9, 122.8, 122.7, 120.9, 119.5, 118.6, 112.5,
50.3, 49.8, 47.6, 39.1, 36.5, 32.1, 30.1, 30.0, 27.9, 22.0, 21.8; IR (film
on NaCl) 2928, 1583, 1560, 1406, 1304, 1280, 1261, 1207 cm−1;
HRMS (ESI, HRDFMagSec) m/z 503.1329 (calcd for
C25H28ON2130Te + H+: 503.1337).
Preparation of Bisjulolidyl Thiorhodamine 5-S. Phenyl-
magnesium bromide (1 M in THF, 1.24 mL, 1.24 mmol) was added
dropwise to a stirred solution of 2-S (100 mg, 0.248 mmol) in THF
(10 mL), and the resulting mixture was heated at reflux for 16 h and
then cooled to ambient temperature. The reaction was quenched by
the addition of glacial acetic acid (2 mL) and the resulting mixture was
poured into 200 mL of aqueous 10% HPF6. After stirring for 12 h, the
precipitate was collected via filtration and washed with water (30 mL)
and diethyl ether (4 × 25 mL) to give 138 mg (91.4%) of 5-S as a
green solid, mp >250 °C: 1H NMR (500 MHz, CD2Cl2) δ 7.63−7.56
(m, 3 H), 7.30−7.23 (m, 2 H), 6.95 (s, 2 H), 3.54−3.44 (m, 8 H), 2.94
(t, 4 H, J = 6.0 Hz), 2.65 (t, 4 H, J = 6.0 Hz), 2.16 (quintet, 4 H, J =
6.0 Hz), 1.95 (quintet, 4 H, J = 6.0 Hz); 13C NMR (75.5 MHz,
CDCl3) δ 157.3, 148.5, 138.8, 137.0, 132.8, 129.8, 129.2, 128.8, 125.1,
118.6, 114.1, 51.5, 50.5, 28.2, 24.4, 20.8, 20.4; λmax (MeOH) 594 nm
1
solid, mp >250 °C: H NMR (300 MHz, CD2Cl2) δ 7.95 (s, 2 H),
3.41−3.10 (m, 8 H), 2.95−2.65 (m, 8 H), 2.14−1.82 (m, 8 H); 13C
NMR (75.5 MHz, CD2Cl2) δ 178.1, 145.8, 134.8, 127.7, 120.7, 118.1,
113.5, 50.6, 49.7, 28.2, 24.5, 21.9, 21.6; IR (film on NaCl) 2932, 1590,
1421, 1331, 1302 cm−1; HRMS [ESI, high-resolution, double focusing
magnetic sector (HRDFMagSec)] m/z 403.1845 (calcd for
C25H26O1N2S1 + H+: 403.1839).
Preparation of Bisjulolidyl Selenoxanthone 2-Se. Phosphorus
oxychloride (1.46 mL, 15.7 mmol), triethylamine (2.19 mL, 15.7
mmol), and 15-Se (700 mg, 1.31 mmol) in anhydrous CH3CN (30
mL) were treated as described for the preparation of 2-S. The crude
product was recrystallized from CH2Cl2/hexanes to give 410 mg
1
(70.0%) of 2-Se as a brown solid, mp >250 °C: H NMR (500 MHz,
CDCl3) δ 8.17 (s, 2 H), 3.31−3.24 (m, 8 H), 2.86 (t, 4 H, J = 6.5 Hz),
2.79 (t, 4 H, J = 6.5 Hz), 2.08 (quintet, 4 H, J = 6.5 Hz), 1.98 (quintet,
4 H, J = 6.5 Hz); 13C NMR (125 MHz, CDCl3) δ 180.3, 145.5, 133.6,
129.3, 120.2, 119.3, 114.6, 50.2, 49.4, 27.6, 25.5, 21.5, 21.3; IR (film on
NaCl) 2927, 2834, 1586, 1569, 1540, 1416, 1329, 1301, 1204 cm−1;
HRMS (ESI, HRDFMagSec) m/z 451.1289 (calcd for C25H26ON280Se
+ H+: 451.1283).
Preparation of Bisjulolidyl Telluroxanthone 2-Te. Phosphorus
oxychloride (1.44 mL, 15.5 mmol), triethylamine (2.16 mL, 15.5
mmol), and 15-Te (753 mg, 1.29 mmol) in anhydrous CH3CN (30
mL) were treated as described for the preparation of 2-S. The crude
product was recrystallized from CH2Cl2/hexanes to give 380 mg
(59.1%) of 2-Te as a brown solid, mp >250 °C: 1H NMR (500 MHz,
CD2Cl2) δ 8.13 (s, 2 H), 3.51−3.23 (m, 8 H), 2.85 (t, 4 H, J = 6.5
Hz), 2.70 (t, 4 H, J = 6.5 Hz), 2.07 (quintet, 4 H, J = 6.5 Hz), 1.97
(quintet, 4 H, J = 6.5 Hz); 13C NMR (125 MHz, CDCl3) δ 184.2,
146.1, 131.4, 122.8, 122.3, 121.3, 118.6, 50.5, 49.9, 30.0, 28.1, 22.2,
21.9; IR (film on NaCl) 2940, 2836, 1583, 1556, 1535, 1504, 1406,
1321, 1292, 1204 cm−1; HRMS (ESI, HRDFMagSec) m/z 501.1172
(calcd for C25H26ON2130Te + H+: 501.1180).
Preparation of Bishalf-julolidyl Thioxanthone 3-S. Phospho-
rus oxychloride (2.36 mL, 25.3 mmol), triethylamine (3.53, 25.3
mmol), and 17-S (1.04 g, 2.11 mmol) in anhydrous CH3CN (25 mL)
were treated as described for the preparation of 2-S. The crude
product was recrystallized from CH2Cl2/hexanes to give 708 mg
1
(82.5%) of 3-S as a brown solid, mp >250 °C: H NMR (500 MHz,
CDCl3) δ 8.39 (s, 2 H), 6.44 (s, 2 H), 3.38 (t, 4 H J = 6.0 Hz), 3.01 (s,
6 H), 1.76 (t, 4 H, J = 6.0 Hz), 1.35 (s, 12 H); 13C NMR (75.5 MHz,
CDCl3) δ 177.5, 147.3, 136.7, 130.3, 125.9, 118.2, 103.4, 47.1, 38.7,
35.9, 31.7, 29.7; IR (film, NaCl) 2957, 1594, 1574, 1520, 1434 cm−1;
HRMS (ESI, HRDFMagSec) m/z 407.2149 (calcd for C25H30N2OS +
H+: 407.2152).
Preparation of Bishalf-julolidyl Selenoxanthone 3-Se.
Phosphorus oxychloride (0.849 mL, 9.11 mmol), triethylamine (1.27
mL, 9.11 mmol), and 17-Se (409 mg, 0.759 mmol) in anhydrous
CH3CN (15 mL) were treated as described for the preparation of 2-S.
The crude product was recrystallized from CH2Cl2/hexanes to give
250 mg (72.5%) of 3-Se as a brown solid, mp >250 °C: 1H NMR (500
MHz, CDCl3) δ 8.47 (s, 2 H), 6.53 (s, 2 H), 3.38 (t, 4 H, J = 6.0 Hz),
3.00 (s, 6 H), 1.75 (t, 4 H, J = 6.0 Hz), 1.34 (s, 12 H); 13C NMR (75.5
MHz, CDCl3) δ 179.5, 147.3, 134.1, 130.5, 127.5, 119.7, 106.2, 47.2,
38.8, 36.0, 31.8, 29.8; IR (film on NaCl) 2955, 1590, 1562, 1517 cm−1;
HRMS (ESI, HRDFMagSec) m/z 455.1599 (calcd for C25H30N2O80Se
+ H+: 455.1596).
Preparation of Bishalf-julolidyl Telluroxanthone 3-Te.
Phosphorus oxychloride (1.29 mL, 13.8 mmol), triethylamine (1.92
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Organometallics
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(ε = 1.24 × 10−5 M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z
463.2203 (calcd for C31H31N2S+: 463.2202).
118.8, 113.9, 104.8, 51.5, 50.6, 48.4, 39.8, 34.7, 32.1, 28.6, 28.1, 24.3,
20.7, 20.2; λmax (MeOH) 587 nm (ε = 1.20 × 105 M−1 cm−1); HRMS
(ESI, HRDFMagSec) m/z 465.2358 (calcd for C31H33N2S+:
465.2359).
Preparation of Bisjulolidyl Selenorhodamine 5-Se. Phenyl-
magnesium bromide (1 M in THF, 2.23 mL, 2.23 mmol) and 2-Se
(100 mg, 0.223 mmol) in THF (10 mL) were treated as described for
the preparation of 5-S to give 125 mg (85.6%) of 5-Se as a blue solid,
Preparation of Julolidyl/Half-julolidyl Selenorhodamine 7-
Se. Phenylmagnesium bromide (1 M in THF, 1.11 mL, 1.11 mmol)
and 4-Se (100 mg, 0.222 mmol) in THF (10 mL) were treated as
described for the preparation of 5-S to give 110 mg (75.3%) of 7-Se as
a purple solid, mp 237−239 °C: 1H NMR (500 MHz, CDCl3) δ 7.65−
7.54 (m, 3 H), 7.30−7.23 (m, 2 H), 7.19 (s, 1 H), 7.18 (s, 1 H), 7.10
(s, 1 H), 3.56−3.44 (m, 6 H), 3.21 (s, 3 H), 2.78 (t, 2 H, J = 6.0 Hz),
2.64 (t, 2 H, J = 6.0 Hz), 2.18 (quintet, 2 H, J = 6.0 Hz), 1.95 (quintet,
2 H, J = 6.0 Hz), 1.73 (t, 2 H, J = 6.0 Hz), 1.03 (s, 6 H); 13C NMR
(75.5 MHz, CDCl3) 158.7, 149.1, 148.1, 142.6, 141.6, 137.6, 134.9,
133.8, 131.7, 129.0, 128.8, 128.4, 124.3, 119.2, 119.1, 116.2, 107.4,
51.1, 50.2, 48.0, 39.5, 34.4, 31.7, 28.6, 27.6, 25.7, 20.2, 19.9; λmax
(MeOH) 597 nm (ε = 1.22 × 105 M−1 cm−1); HRMS (ESI,
HRDFMagSec) m/z 513.1803 (calcd for C31H33N280Se+: 513.1803).
Preparation of Julolidyl/Half-julolidyl Tellurorhodamine 7-
Te. Phenylmagnesium bromide (1 M in THF, 1.00 mL, 1.00 mmol)
and 4-Te (100 mg, 0.200 mmol) in THF (10 mL) were treated as
described for the preparation of 5-S to give 125 mg (88.7%) of 7-Te as
1
mp >250 °C: H NMR (500 MHz, CDCl3) δ 7.62−7.54 (m, 3 H),
7.28−7.20 (m, 2 H), 6.98 (s, 2 H), 3.56−3.40 (m, 8 H), 2.86 (t, 4 H, J
= 6.0 Hz), 2.62 (t, 4 H, J = 6.0 Hz), 2.18 (quintet, 4 H, J = 6.0 Hz),
1.94 (quintet, 4 H, J = 6.0 Hz); 13C NMR (75.5 MHz, CDCl3) δ
159.1, 148.3, 141.0, 138.4, 135.1, 129.8, 129.0, 128.7, 124.5, 119.4,
116.5, 51.5, 50.6, 28.1, 26.2, 20.8, 20.6; λmax (MeOH) 604 nm (ε =
1.35 × 105 M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z 511.1649
(calcd for C31H31N280Se+: 511.1647).
Preparation of Bisjulolidyl Tellurorhodamine 5-Te. Phenyl-
magnesium bromide (1 M in THF, 1.00 mL, 1.00 mmol) and 2-Te
(100 mg, 0.201 mmol) in THF (10 mL) were treated as described for
the preparation of 5-S to give 130 mg (92.3%) of 5-Te as a purple
solid, mp >250 °C: 1H NMR (500 MHz, CD2Cl2) δ 7.60−7.51 (m, 3
H), 7.25−7.19 (m, 2 H), 7.09 (s, 2 H), 3.47 (t, 4 H, J = 6.0 Hz), 3.43
(t, 4 H, J = 6.0 Hz), 2.73 (t, 4 H, J = 6.5 Hz), 2.59 (t, 4 H, J = 6.0 Hz),
2.20 (quintet, 4 H, J = 6.0 Hz), 1.93 (quintet, 4 H, J = 6.0 Hz); 13C
NMR (75.5 MHz, CDCl3) δ 162.2, 147.7, 140.6, 138.1, 135.6, 129.7,
128.6, 128.5, 124.2, 121.5, 121.0, 51.4, 50.7, 30.5, 28.0, 21.0, 20.8; λmax
(MeOH) 615 nm (ε = 1.44 × 105 M−1 cm−1); HRMS (ESI,
HRDFMagSec) m/z 561.1540 (calcd for C31H31N2130Te+: 561.1544).
Preparation of Bishalf-julolidyl Thiorhodamine 6-S. Phenyl-
magnesium bromide (1 M in THF, 2.46 mL, 2.46 mmol) and 3-S (100
mg, 0.246 mmol) in THF (10 mL) were treated as described for the
preparation of 5-S to give 124 mg (82.1%) of 6-S as a green solid, mp
1
a purple solid, mp >250 °C: H NMR (500 MHz, CD2Cl2) δ 7.62−
7.54 (m, 3 H), 7.41 (s, 1 H), 7.28 (s, 1 H), 7.27−7.23 (m, 2 H), 7.22
(s, 1 H), 3.53−3.46 (m, 4 H), 3.44 (t, 2 H, J = 6.0 Hz), 3.19 (s, 3 H),
2.67−2.58 (m, 4 H), 2.24−2.17 (m, 2 H), 1.98−1.90 (m, 2 H), 1.71 (t,
2 H, J = 6.0 Hz), 0.99 (s, 6 H); 13C NMR (75.5 MHz, CDCl3) δ 162.9,
148.8, 148.3, 140.3, 138.7, 136.8, 135.1, 135.0, 134.1, 129.6, 128.8,
128.6, 124.5, 122.0, 121.7, 121.6, 114.3, 51.6, 50.9, 48.5, 39.8, 34.9,
32.0, 30.8, 28.7, 27.9, 20.9, 20.7; λmax (MeOH) 610 nm (ε = 1.27 ×
105 M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z 563.1697 (calcd for
C31H33N2130Te+: 563.1700).
1
252−254 °C: H NMR (500 MHz, CD2Cl2) δ 7.68−7.61 (m, 3 H),
7.36−7.30 (m, 2 H), 7.29 (s, 2 H), 7.00 (s, 2 H), 3.58 (t, 4 H, J = 6.0
Hz), 3.24 (s, 6 H), 1.75 (t, 4 H, J = 6.0 Hz), 1.09 (s, 12 H); 13C NMR
(75.5 MHz, CD2Cl2) δ 158.7, 150.5, 142.9, 136.2, 135.1, 130.6, 129.7,
129.6, 128.9, 119.4, 104.6, 48.5, 40.0, 34.6, 32.2, 28.6; λmax (MeOH)
579 nm (ε = 1.04 × 105 M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z
467.2514 (calcd for C31H35N2S+: 467.2515).
Preparation of Diaryl Selenide 22. sec-Butyllithium (1.00 M in
cyclohexane, 0.96 mL, 0.96 mmol), TMEDA (144 μL, 0.964 mmol),
amide 1619 (0.250 g, 0.873 mmol), and diselenide 2122 (0.730 g, 1.83
mmol) in THF (2 × 30 mL) were treated as described for the
preparation of 15-S. The crude product was purified via column
chromatography (SiO2, 4:6 EtOAc/hexanes) to yield 194 mg (45.9%)
of 22 as a pale yellow oil: 1H NMR (500 MHz, CDCl3) δ 7.13 (t, 1 H,
J = 8.1 Hz), 7.04−6.95 (m, 2 H), 6.90 (d, 1 H, J = 8.1 Hz), 6.64 (dd, 1
H, J = 2.4, 8.1 Hz), 6.48 (s, 1 H), 3.62−3.36 (m, 4 H), 3.19 (t, 2 H, J =
6.0 Hz), 2.91 (s, 6 H), 2.67 (s, 3 H), 1.71 (t, 2 H, J = 6.0 Hz), 1.65 (m,
2 H), 1.58 (m, 4 H), 1.23 (s, 6 H); 13C NMR (300 MHz, CDCl3) δ
169.8, 150.7, 145.6, 130.7, 129.4, 129.2, 128.3, 125.2, 124.1, 122.2,
118.1, 114.0, 111.5, 47.1, 45.0 (br), 40.2, 38.5, 36.4, 31.5, 30.3, 25.8,
24.4; IR (film on NaCl) 2933, 2852, 1625, 1590, 1557, 1533, 1493,
1467, 1430, 1347, 1317, 1260 cm−1; HRMS (ESI, HRDFMagSec) m/z
486.2018 (calcd for C26H35N3O80Se + H+: 486.2018).
Preparation of Bishalf-julolidyl Selenorhodamine 6-Se.
Phenylmagnesium bromide (1 M in THF, 1.10 mL, 1.10 mmol) and
3-Se (100 mg, 0.22 mmol) in THF (10 mL) were treated as described
for the preparation of 5-S to give 113 mg (77.9%) of 6-Se as a green
1
solid, mp 246−248 °C: H NMR (500 MHz, CD2Cl2) δ 7.65−7.59
(m, 3 H), 7.33−7.27 (m, 4 H), 7.17 (s, 2 H), 3.55 (t, 4 H, J = 6.0 Hz),
3.23 (s, 6 H), 1.74 (t, 4 H, J = 6.0 Hz), 1.05 (s, 12 H); 13C NMR (75.5
MHz, CDCl3) δ 159.6, 149.6, 144.5, 137.5, 134.1, 132.1, 129.0, 128.5,
127.1, 119.8, 107.9, 48.3, 39.9, 34.5, 31.8, 28.6; λmax (MeOH) 590 nm
(ε = 1.36 × 105 M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z
515.1960 (calcd for C31H35N280Se+: 515.1960).
Preparation of Selenoxanthone 23. Phosphorus oxychloride
(0.380 mL, 4.08 mmol), triethylamine (0.567 mL, 4.07 mmol), and
selenide 22 (165 mg, 0.339 mmol) in anhydrous CH3CN (15 mL)
were treated as described for the preparation of 2-S. The crude
product was recrystallized from CH2Cl2/hexanes to give 130 mg
Preparation of Bishalf-julolidyl Tellurorhodamine 6-Te.
Phenylmagnesium bromide (1 M in THF, 1.98 mL, 1.98 mmol) and
3-Te (100 mg, 0.198 mmol) in THF (10 mL) were treated as
described for the preparation of 5-S to give 105 mg (75.0%) of 6-Te as
a green solid, mp 250−252 °C: 1H NMR (500 MHz, CDCl3) δ 7.61−
7.55 (m, 3 H), 7.48 (s, 2 H), 7.35 (s, 2 H), 7.25−7.21 (m, 2 H), 3.49
(t, 4 H, J = 6.0 Hz), 3.24 (s, 6 H), 1.71 (t, 4 H, J = 6.0 Hz), 1.00 (s, 12
H); 13C NMR (75.5 MHz, CD2Cl2) δ 163.5, 149.2, 140.0, 136.0,
135.5, 134.2, 129.3, 129.0, 128.7, 122.1, 114.8, 48.6, 39.9, 34.8, 32.0,
28.6; λmax (MeOH) 607 nm (ε = 1.21 × 105 M−1 cm−1); HRMS (ESI,
HRDFMagSec) m/z 565.1857 (calcd for C31H35N2130Te+: 565.1857).
Preparation of Julolidyl/Half-julolidyl Thiorhodamine 7-S.
Phenylmagnesium bromide (1 M in THF, 2.47 mL, 2.47 mmol) and
4-S (100 mg, 0.247 mmol) in THF (10 mL) were treated as described
for the preparation of 5-S to give 136 mg (90.1%) of 7-S as a purple
1
(95.7%) of 23 as a yellow solid, mp 200−203 °C: H NMR (500
MHz, CDCl3) δ 8.94 (d, 1 H, J = 9.0 Hz), 8.46 (s, 1 H), 6.76 (dd, 1 H,
J = 3.0, 9.0 Hz), 6.67 (d, 1 H, J = 3.0 Hz), 6.54 (s, 1 H), 3.39 (t, 2 H, J
= 6.0 Hz), 3.07 (s, 6 H), 3.02 (s, 3 H), 1.76 (t, 2 H, J = 6.0 Hz), 1.35
(s, 6 H); 13C NMR (500 MHz, CDCl3) δ 179.8, 151.6, 147.7, 136.4,
134.4, 132.2, 130.9, 127.8, 120.5, 119.9, 111.3, 107.9, 106.4, 47.5, 40.0,
39.0, 36.2, 32.0, 29.9; IR (film on NaCl) 1590, 1314, 1287 cm−1;
HRMS (ESI, HRDFMagSec) m/z 401.1126 (calcd for C21H24N2O80Se
+ H+: 401.1127).
Preparation of Half-julolidyl Selenorhodamine 20-Se.
Phenylmagnesium bromide (1.0 M in THF, 2.50 mL, 2.50 mmol)
and selenoxanthone 23 (200 mg, 0.501 mmol) in THF (20 mL) were
treated as described for the preparation of 5-S to give 225 mg (74.3%)
1
solid, mp 249−251 °C: H NMR (500 MHz, CD2Cl2) δ 7.66−7.58
(m, 3 H), 7.33−7.27 (m, 2 H), 7.19 (s, 1 H), 7.06 (s, 1 H), 7.03 (s, 1
H), 3.57 (t, 2 H, J = 6.5 Hz), 3.54−3.48 (m, 4 H), 3.22 (s, 3 H), 2.88
(t, 2 H, J = 6.5 Hz), 2.67 (t, 2 H, J = 6.5 Hz), 2.17 (quintet, 2 H, J =
6.0 Hz), 1.96 (quintet, 2 H, J = 6.0 Hz), 1.74 (t, 2 H, J = 6.5 Hz), 1.07
(s, 6 H); 13C NMR (75.5 MHz, CD2Cl2) δ 157.8, 150.0, 148.9, 141.9,
139.6, 136.6, 134.8, 133.2, 130.2, 129.7, 129.4, 128.8, 125.4, 119.1,
1
of 20-Se as a green solid, mp 215−218 °C: H NMR (500 MHz,
CD2Cl2) δ 7.66−7.59 (m, 2 H), 7.45 (d, 1 H, J = 9.0 Hz), 7.36 (s, 1
H) 7.32−7.27 (m, 3 H), 7.23 (d, 1 H, J = 2.5 Hz), 7.19 (s, 1 H), 6.82
(dd, 1 H, J = 2.5, 9.5 Hz), 3.57 (t, 2 H, J = 6.5 Hz), 3.26 (s, 3 H), 3.23
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Organometallics
Article
(s, 6 H), 1.75 (t, 2 H, J = 6.5 Hz), 1.05 (s, 6 H); 13C NMR (500 MHz,
CD2Cl2) δ 161.3, 153.0, 150.7, 145.4, 145.1, 138.4, 137.6, 135.0, 133.1,
129.5, 128.9, 120.5, 120.0, 114.7, 108.9, 108.3, 48.9, 40.7, 40.3, 34.6,
32.1, 28.5; λmax (CH3OH) 585 nm (ε = 1.35 × 105 M−1 cm−1); IR
(film on NaCl) 1591, 1509, 1448, 1387, 1356, 1330, 1252, 1211 cm−1;
HRMS (ESI, HRDFMagSec) m/z 461.1490 (calcd for C27H29N2Se+:
461.1497).
J = 6.0 Hz), 3.21 (s, 4 H), 2.42 (s, 3 H), 1.82 (s, 6 H), 1.82 (t, 4 H, J =
6.0 Hz), 1.00 (s, 6 H). To this solution was added 12.5 μL of an 8.8 M
solution of H2O2 (0.11 mmol, 0.18 M final concentration). The H
1
NMR spectrum of the resulting solution was recorded within 3 min of
1
addition of the H2O2, and oxidation was complete at this point: H
NMR (500 MHz, CD3OD 0.1 M CF3C(O)OD) δ 8.00 (s, 2 H), 7.19
(s, 2 H), 7.15 (s, 2 H), 3.76 (t, 4 H, J = 6.0 Hz), 3.48 (s, 4 H), 2.42 (s,
3 H), 1.93 (s, 6 H), 1.77 (t, 4 H, J = 6.0 Hz), 1.00 (s, 6 H); 13C NMR
(500 MHz, 0.1 M CF3C(O)OD in CD3OD) δ 153.4, 140.8, 137.0,
136.8, 135.7, 129.8, 129.4, 123.7, 50.2, 40.8, 35.3, 32.6, 32.3, 28.9, 21.2,
19.6; λmax (CH3OH) 692 nm (ε = 1.65 × 105 M−1 cm−1); HRMS
(ESI, HRDFMagSec) m/z 623.2279 (calcd for C34H41N2O130Te+:
623.2276).
Determination of Singlet Oxygen Yields from Singlet
Oxygen Phosphorescence Spectroscopy. Generation of singlet
oxygen (1O2) was assessed by its phosphorescence peak at 1270 nm. A
spectrometer equipped with a near-infrared photodetector was used
for acquisition of the emission spectra in NIR spectral range. A diode-
pumped solid-state laser at 532 nm was the excitation source. The
emission signal was collected at 90° relative to the exciting laser beam
with the use of a 950 nm long-pass filter to attenuate the scattered
light and fluorescence from the samples. The samples (methanol
solutions of the compounds in quarts cuvettes) were placed in front of
the spectrometer entrance slit.
Fluorescence Experiments. Measurements of fluorescence
quantum yield were performed on a spectrofluorometer using either
fluorescent dye Rhodamine 6G with known ΦFL = 0.9344 in MeOH for
5-E−7-E or fluorescent dye LD 700 perchlorate (Rhodamine 700) as a
reference with known ΦFL = 0.3831 in MeOH for 27 and 28.
Cell Experiments. Colo-26, a murine colon carcinoma cell line,
was maintained in RPMI 1640 supplemented with 10% fetal calf serum
(FCS) and antibiotics at 37 °C, and 5% CO2. Colo-26 cells were
harvested, counted, and seeded at a density of 1.5 × 105 cells per well
in 0.5 mL of RPMI supplemented medium the night before the assay
in a 24-well plate. The day of the assay, the medium was removed from
a single well at a time, and 0.5 mL of HBSS was added to the cells.
MitoTracker Green (0.25 μL of stock solution and 0.5 μM final
concentration) was added to the well, and the plate was incubated for
10 min. Tellurorhodamine 27 (0.2 μM) was added, and the plate was
incubated for an additional 5 min (total incubation = 15 min). The
HBSS containing tellurorhodamine 27 and MitoTracker Green was
removed, and 0.5 mL of fresh HBSS was added.
Preparation of Tellurorhodamine 27. 2-Bromomesitylene (469
μL, 3.07 mmol) was dissolved in dry THF (1.5 mL) in a round-
bottomed flask. Magnesium (82.0 mg, 3.37 mmol) was added and the
solution stirred at room temperature until most of the magnesium was
consumed. The resulting solution of Grignard reagent was added via
cannula to a stirred suspension of 2-Te (100 mg, 0.204 mmol) in dry
THF (10 mL). The resulting solution was heated at reflux for 24 h,
cooled to ambient temperature, and poured into 200 mL of an ∼10%
aqueous HPF6 solution. The resulting precipitate was collected via
filtration after 12 h of stirring and was washed with water (100 mL)
and diethyl ether (100 mL) to give 127 mg (83.0%) of 27 as a dark
purple solid, mp >250 °C. 1H NMR (500 MHz, CD2Cl2) δ 7.10 (s, 2
H), 7.03 (s, 2 H), 3.47 (t, 4 H, J = 6.0 Hz), 3.43 (t, 4 H, J = 6.0 Hz),
2.74 (t, 4 H, J = 6.5 Hz), 2.61 (t, 4 H, J = 6.5 Hz), 2.42 (s, 3 H), 2.21
(quintet, 4 H, J = 6.0 Hz), 1.93 (quintet, 4 H, J = 6.5 Hz), 1.80 (s, 6
H); 13C NMR (75.5 MHz, CD2Cl2) δ 162.4, 147.9, 138.5, 136.6,
136.0, 135.9, 135.4, 128.7, 125.1, 120.9, 120.8, 51.4, 50.7, 30.5, 28.0,
21.2, 21.0, 20.8, 19.7; λmax (MeOH) 617 nm (ε = 1.65 × 105 M−1
cm−1); HRMS (ESI, HRDFMagSec) m/z 603.2013 (calcd for
C34H37N2130Te+: 603.2012).
Oxidation of Tellurorhodamine 27 to Tellurorhodamine
Telluroxide 28. Tellurorhodamine 27 (1.5 mg, 0.20 μmol) was
dissolved in 0.60 mL of a solution of 0.1 M CF3CO2D in CD3OD in a
5 mm NMR tube. The 1H NMR spectrum of 27 in this solvent system
was acquired: δ 7.09 (s, 2 H), 7.07 (s, 2 H), 3.54−3.48 (m, 4 H),
3.47−3.43 (m, 4 H), 2.82−2.74 (m, 4 H), 2.64−2.56 (m, 4 H), 2.42
(s, 3 H), 2.23−2.15 (m, 4 H), 1.98−1.88 (m, 4 H), 1.79 (s, 6 H). To
this solution was added 12.5 μL of an 8.8 M solution of H2O2 (0.11
1
mmol, 0.18 M final concentration). The H NMR spectrum of the
resulting solution was recorded within 3 min of addition of the H2O2,
and oxidation was complete at this point: 1H NMR (500 MHz,
CD3OD 0.1 M CF3C(O)OD) δ 7.05 (s, 2 H), 6.81 (s, 2 H), 3.75−
3.67 (m, 4 H), 3.66−3.60 (m, 4 H), 3.46−3.36 (m, 4 H), 2.58−2.49
(m, 4 H), 2.39 (s, 3 H), 2.29−2.17 (m, 4 H), 2.00−1.86 (m, 4 H), 1.90
(s, 6 H); 13C NMR (500 MHz, 0.1 M CF3C(O)OD in CD3OD) δ
151.1, 139.3, 137.2, 136.2, 135.4, 130.1, 128.5, 126.0, 52.0, 51.4, 30.4,
27.3, 20.8, 20.2, 20.1, 18.6; λmax (CH3OH) 704 nm (ε = 1.35 × 105
M−1 cm−1); HRMS (ESI, HRDFMagSec) m/z 619.1963 (calcd for
C34H37N2O130Te+: 619.1963).
A camera-equipped fluorescence microscope was used in the cell
imaging experiments. Tellurorhodamine 27 and/or telluroxide 28 were
excited with 620 30 nm light, and MitoTracker Green was excited
with 470 20 nm light. ImageJ software was used to color the images
and to give an overlay of images.
Preparation of Tellurorhodamine 29. 2-Bromomesitylene (461
μL, 2.98 mmol) was added to a stirred suspension of ground
magnesium turnings (79.7 mg, 3.28 mmol) in THF (3 mL). The
resulting solution was stirred at ambient temperature for 3 h before it
was transferred via cannula to a stirred solution of telluroxanthone 3-
Te (150 mg, 0.298 mmol) at room temperature in THF (5 mL). The
mixture was heated at reflux overnight, then cooled to ambient
temperature before glacial acetic acid (2 mL) was added. The resulting
solution was poured into cold, stirring 10% aqueous HPF6 (200 mL),
and the resulting mixture was stirred for 12 h. The precipitate was
collected via filtration and washed with water (50 mL) and hexanes
(75 mL), yielding 125 mg (55.8%) of 29 as a blue solid, mp 166−168
°C: 1H NMR (500 MHz, CD2Cl2) δ 7.40 (s, 2 H), 7.39 (s, 2 H), 7.08
(s, 2 H), 3.50 (t, 4 H, J = 6.0 Hz), 3.20 (s, 6 H), 2.44 (s, 3 H), 1.82 (s,
6 H), 1.73 (t, 4 H, J = 6.0 Hz), 1.01 (s, 12 H); 13C NMR (75.5 MHz,
CD2Cl2) δ 164.1, 149.5, 138.9, 135.9, 135.8, 135.6, 135.1, 133.7, 128.7,
121.5, 114.9, 48.5, 39.9, 34.8, 31.9, 28.8, 21.2, 19.5; λmax (CH3OH) 606
nm (ε = 9.66 × 104 M−1 cm−1); HRMS m/z 607.2329 (ESI,
HRDFMagSec) (C34H41N2130Te+: 607.2326).
ASSOCIATED CONTENT
■
S
* Supporting Information
General experimental procedures and 1H and 13C NMR spectra
for 2-E−7-E, 9, 10-E, 11, 12, 13-E, 15-E, 17-E, 18-E, 20-E, 22,
23, and 27−30. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: mdetty@buffalo.edu.
Author Contributions
§M.W.K. and G.A.S. contributed equally to this work.
Notes
The authors declare no competing financial interest.
Oxidation of Tellurorhodamine 29 to Tellurorhodamine
Telluroxide 30. Tellurorhodamine 29 (1.5 mg, 0.20 μmol) was
dissolved in 0.60 mL of a solution of 0.1 M CF3CO2D in CD3OD in a
5 mm NMR tube. The 1H NMR spectrum of 29 in this solvent system
was acquired: δ 7.73 (s, 2 H), 7.43 (s, 2 H), 7.16 (s, 2 H), 3.54 (t, 4 H,
ACKNOWLEDGMENTS
■
This research was supported in part by the NIH (GM-94367)
and the National Science Foundation (CHE-1151379).
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(31) Sauer, M.; Han, K.-T.; Muller, R.; Nord, S.; Schulz, A.; Seeger,
̈
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