Synthesis of phosphorescent asymmetrically π-extended porphyrins for two-photon applications

Article abstract of DOI:10.1021/jo501521x

Significant effort has been directed in recent years toward porphyrins with enhanced two-photon absorption (2PA). However, the properties of their triplet states, which are central to many applications, have rarely been examined in parallel. Here we repor

Full text of DOI:10.1021/jo501521x

Article
pubs.acs.org/joc
Open Access on 08/26/2015
Synthesis of Phosphorescent Asymmetrically π‑Extended Porphyrins
for Two-Photon Applications
Tatiana V. Esipova and Sergei A. Vinogradov*
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
*
S Supporting Information
ABSTRACT: Significant effort has been directed in recent
years toward porphyrins with enhanced two-photon absorp-
tion (2PA). However, the properties of their triplet states,
which are central to many applications, have rarely been
examined in parallel. Here we report the synthesis of
asymmetrically π-extended platinum(II) and palladium(II)
porphyrins, whose 2PA into single-photon-absorbing states is
enhanced as a result of the broken center-of-inversion
symmetry and whose triplet states can be monitored by
room-temperature phosphorescence. 5,15-Diaryl-syn-dibenzo-
porphyrins (DBPs) and syn-dinaphthoporphyrins (DNPs)
were synthesized by [2 + 2] condensation of the
corresponding dipyrromethanes and subsequent oxidative
aromatization. Butoxycarbonyl groups on the meso-aryl rings render these porphyrins well-soluble in a range of organic
solvents, while 5,15-meso-aryl substitution causes minimal nonplanar distortion of the macrocycle, ensuring high triplet emissivity.
A syn-DBP bearing four alkoxycarbonyl groups in the benzo rings and possessing a large static dipole moment was also
synthesized. Photophysical properties (2PA brightness and phosphorescence quantum yields and lifetimes) of the new
porphyrins were measured, and their ground-state structures were determined by DFT calculations and/or X-ray analysis. The
developed synthetic methods should facilitate the construction of π-extended porphyrins for applications requiring high two-
photon triplet action cross sections.
INTRODUCTION
asymmetrical porphyrins are usually more laborious to
synthesize. However, for technologies that rely on nonlinear
optical properties, asymmetrical π-extension may bring about
unique possibilities, for example, as a method to increase two-
photon absorption (2PA) cross sections.
A number of porphyrin-based systems with enhanced 2PA
■
In the past two decades, interest in porphyrins with
aromatically extended π-systems has been steadily on the
1
−4
rise.
Today areas of their application encompass optical
49
5
,6
7−9
limiting, organic light-emitting diodes (OLEDs) and other
10−13
electronic devices,
triplet annihilation (TTA),
biomedical optical imaging and sensing.
upconversion by sensitized triplet−
14−19 20−23
have been designed in the past, and in some cases 2PA cross
phototherapy,
and
50−57
24−28
sections of several thousand GM units have been reported.
However, in only a few cases have triplet states of these systems
Progress in all
of these areas depends on the availability of molecules with
different functional groups, optimal solubility, and tailored
photophysical properties, warranting continuous development
and optimization of synthetic methods.
52,57
been evaluated in parallel.
Triplet states, on the other hand,
are central to several key applications of porphyrins, including
58−60
two-photon photodynamic therapy (2P PDT)
and two-
photon phosphorescence lifetime microscopy (2PLM) of
Among π-extended porphyrins, fully symmetrical molecules
61−63
oxygen.
In those cases when evaluation of the triplet
such as tetrabenzoporphyrins, tetranaphthporphyrins, and
29
states of 2P-absorbing porphyrins has been attempted,
measurements have been performed by indirect methods,
such as quantification of singlet oxygen (a product of the triplet
quenching reaction) or measuring downstream effects of singlet
tetraanthraporphyrins captured the most attention, in part
because their synthetic chemistry has been most thoroughly
2
,4
developed. These chromophores are characterized by strong
6
,29,30
and narrow absorption bands in the red spectral region
and form brightly phosphorescent complexes with Pd and
59
oxygen itself. Such methods, however, can be subject to major
64
3
1−35
errors due to a large number of interfering parameters. At the
same time, it is quite possible that modifications of porphyrins
leading to an increase in 2PA can simultaneously cause severe
Pt
that are of interest for OLED and imaging applications.
In contrast, asymmetrically π-extended porphyrins, which also
36−47
have been known for a long time,
have been studied only
4
8
occasionally. Structural asymmetry generally causes broad-
ening of the porphyrin optical spectra, which may be seen as a
disadvantage from the applications’ point of view. In addition,
Received: July 21, 2014
©
XXXX American Chemical Society
A
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triplet quenching effects, e.g., via formation of low-lying charge
transfer states and/or by influencing the vibrational dynamics of
RESULTS AND DISCUSSION
■
3
4,35
Synthesis. The π-extended porphyrins synthesized in this
the macrocycle, enhancing its nonradiative triplet decay.
As
study are shown in Chart 1. Two adjacent pyrrole rings in each
macrocycle are fused with external aromatic fragments through
the β-carbon atoms, forming syn- (or adj-) dibenzo- and
dinaphtho[2,3]porphyrins. If meso-aryl substituents are dis-
regarded, these macrocycles belong to the C symmetry group,
unlike regular metalloporphyrins, which have D -type
symmetry and thus possess a center of inversion.
Previous studies have shown that planar meso-unsubstituted
π-extended porphyrins are significantly more emissive than
a result, while gaining in 2PA, these porphyrins could lose their
other critical property, i.e., the ability to form long-lived triplet
states.
Our goal was to develop 2P-absorbing porphyrins whose
triplet states can be monitored directly by emission. The
selection rules determining linear one-photon (1P) and 2P
transition probabilities in centrosymmetrical molecules, such as
2v
4
h
65
regular metalloporphyrins, are mutually exclusive. Conse-
quently, strongly allowed 1P transitions into B (Soret) and Q
3
4,71
6
6
their nonplanar meso-tetraarylated analogues.
meso-unsubstituted porphyrins are prone to aggregation and
However,
states, which are states of ungerade symmetry, are not allowed
for 2PA. On the other hand, gerade states, which can be
66
often pose serious solubility problems. On the other hand,
accessed via 2PA, lie at much higher energies, and their 2P
spectra overlap with linear transitions (e.g., Q bands), causing
the 2P excitation pathway to be overshadowed by 1P
absorption. The above selection rules, however, should be
relaxed if there is no center-of-inversion symmetry in a
porphyrin molecule, causing 1P states to become accessible
by 2PA.
73
meso-5,15-diarylporphyrins offer a useful compromise be-
tween emissivity and solubility. Nonplanar distortions in
porphyrins are usually caused by steric repulsion between β-
pyrrolic substituents (e.g., fused benzo rings) and meso-aryl
groups. Placing only two meso-aryls opposite to each other
allows the macrocycle to evade the strain by undergoing in-
plane as opposed to out-of-plane deformation and thus
Given that Pt and Pd complexes of π-extended porphyrins
exhibit strong phosphorescence and that asymmetric π-
extension significantly affects the electronic structure of
34
preserve planarity. Moreover, in syn-DBPs and syn-DNPs
Chart 1), aromatic rings are appended to pyrroles only on
one side” of the molecule, while the dipyrromethene fragment
(
“
3
0,48
porphyrins,
we set out to examine whether asymmetrically
on the opposite side remains strain-free. mono-Aryl-substituted
DBP 21 lacking a meso-aryl group between the two benzo
substituents was also synthesized. To improve the solubility, the
meso-aryl substituents in the majority of the synthesized
porphyrins were supplemented by meso-dialkoxycarbonyl
groups. In all cases, DFT ground-state calculations (B3LYP/
π-extended Pt and Pd porphyrins can act as efficient triplet
chromophores with intrinsically enhanced 2PA. Here we
present syntheses of nonfully symmetrical π-extended syn-
dibenzo- and syn-dinaphthoporphyrins (DBPs and DNPs,
respectively; Chart 1) and their phosphorescent Pt(II) and
6
-31G*) confirmed planar macrocycle structures (Figure S1 in
Chart 1. Structures of the Target Porphyrins
the Supporting Information).
The saturated precursor porphyrins for syn-DBPs and syn-
DNPs may be obtained from dipyrromethanes bearing C1
synthons at the 1- and 9-positions and appropriate unsub-
stituted counterparts (Scheme 1). Following the methods
7
6−79
developed by Lindsey and co-workers,
b i s ( N , N - d i m e t h y l a m i n o m e t h y l )
we chose to use
7
6
a n d b i s -
derivatives (Chart 2), which have
7
7,79
(
propyliminomethyl)
been shown to minimize scrambling in the condensation
reaction. Route A was selected because of easier accessibility
and higher stability of C1-dipyrromethanes derived from
unsubstituted pyrrole.
Generally, 1,9-bis(N,N-dimethylaminomethyl)-
dipyrromethanes such as 1 (Chart 2) are simpler to synthesize,
and they lead to excellent results when condensations are
Pd(II) complexes. Rational approaches to a number of related
3
6−47,67,68
tetrapyrroles have been explored previously.
In
particular, there is an example of a 5,15-meso-diaryl DBP,
76
carried out in alcohols. For example, in our case 1 was
46
reported by Smith et al., that is very similar to one of our
compounds (porphyrin 20) but was obtained via different
route, i.e., from a sulfolenoporphyrin precursor by the Diels−
Alder reaction. The methodology explored in our synthesis is
successfully employed in the synthesis of porphyrin 13 in
MeOH (see Scheme 3). However, in nonpolar solvents (e.g.,
toluene, benzene), which appeared to favor syntheses of the
majority of our porphyrins (see below), 1,9-bis-
6
9−71
based on the oxidative aromatization method
dihydroisoindole variant,
and its 4,7-
(
propyliminomethyl)dipyrromethane 2 allowed us to achieve
72−75
developed by Cheprakov and co-
significant improvements in the yield. Dipyrromethanes 1 and 2
workers. Preliminary photophysical measurements showed that
all of the synthesized Pt porphyrins exhibit very bright
phosphorescence at ambient temperatures and increased 2PA
compared with nonextended porphyrins. The 2PA is especially
enhanced in the case of porphyrins bearing alkoxycarbonyl
substituents on the fused benzo rings. The developed methods
should facilitate the construction of nonfully symmetrical π-
extended porphyrins for applications requiring enhanced 2PA/
triplet action cross sections, such as 2P PDT and 2PLM.
(
Chart 2) were prepared in 50−70% yield from pyrrole and the
corresponding aldehydes.
Cyclohexadieno- (3 and 4), cyclohexeno- (5 and 6), and
tetrahydronaphthaleno-fused (7) dipyrromethane esters were
synthesized in 70−90% yield from the respective pyr-
6
9,71,80,81
roles
and aldehydes (or dimethoxymethane) following
7
3,75,82
the previously developed procedures (Scheme 2).
case of sterically more hindered structures 5 and 7, longer times
(up to 72 h) were required to complete the condensations.
In the
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Scheme 1. Synthetic Approach to syn-DBPs and syn-DNPs
via Oxidative Aromatization
oligomerization. Dipyrromethane 12 was the least stable in the
series, and it had to be handled especially promptly. On the
basis of analyses of the crude reaction mixtures, the yields of the
dipyrromethanes (starting with esters 3−7) ranged from 30 to
6
5%.
The [2 + 2] assembly leading to the target porphyrins is
shown in Scheme 3. According to the original procedures,
condensation of 1,9-bis(N,N-dimethylaminomethyl)- or 1,9-
bis(N-propyliminomethyl)dipyrromethanes (Chart 2) with 1,9-
unsubstituted dipyrromethanes is carried out optimally in
refluxing methanol in the presence of a 10-fold molar excess of
76−79
Zn(OAc)2.
In cases when the reactants bear functional
groups sensitive to solvolysis, methanol may be substituted by
toluene, also under reflux, in which case 1,9-bis(N-
propyliminomethyl)dipyrromethanes are the substrates of
77
choice.
76
Following the original method, reaction of dipyrromethane
8
with 1 in MeOH in the presence of Zn(OAc) gave the Zn
2
complex of porphyrin 13 (Zn−13) in 13% yield. However,
applying the same conditions directly to the rest of our
substrates proved inefficient. For example, condensation of
dipyrromethanes 10 and 2 in MeOH gave Zn−15 in a rather
low 8% yield, and when the reaction was attempted in toluene,
the yield dropped below 5%. Other dipyrromethanes showed
similar results. On the basis of UV−vis spectra, we concluded
that at least in part the low yields were caused by competing
oxidation of dipyrromethanes into dipyrromethenes (dipyr-
rins), whose formation could be easily detected by character-
84
istic optical absorption. Dipyrrins are inert in the con-
densation.
In order to prevent premature oxidation of dipyrromethanes
and establish overall milder conditions for the synthesis, the
reaction was attempted as a two-step process using dipyrro-
methane 2 as a reactant. In the first step, dipyrromethanes 9−
Chart 2. Dipyrromethanes with C1 Synthons at the 1- and 9-
Positions
1
2 were condensed with 2 under an inert atmosphere (Ar) in
the presence of Zn(OAc) in refluxing benzene. The latter has a
2
lower boiling point than toluene, helping to avoid side reactions
and decomposition of the sensitive dypyrromethanes. The
formation of the corresponding dehydroporphyrinogens and
depletion of the starting materials was monitored by MALDI-
TOF analysis. Once the concentration of the dehydroporphyri-
nogens stopped changing, usually after 2−3 h, the mixtures
were flushed with air and left to react for an additional 8−16 h
(
second step). At this stage, the reaction progress was
monitored by UV−vis spectroscopy, and the refluxing was
continued until the ratio of the intensity in the Soret band
region (∼350−400 nm) to the absorption by the side products
(dipyrrins) near 500−600 nm was at its maximum. It should be
noted that not all of the dipyrromethanes were converted into
dehydroporphyrinogens in the first step, but the mixtures were
simply allowed to reach their respective steady states.
Subsequent oxidation by air apparently was mild enough to
prevent fast oxidation of dipyrromethanes but effective in
converting dehydroporphyrinogens into porphyrins. The
dipyrromethanes in the meantime continued to undergo
condensation to generate new dehydroporphyrinogens for
oxidation. These conditions allowed us to obtain cyclo-
hexadieno- (14) and cyclohexenoporphyrins (15 and 16) in
20−30% yield and the least stable porphyrin 17 in 13% yield. In
all cases, the porphyrins were isolated as Zn complexes.
Generally, using acetic acid as the solvent, as opposed to
dichloromethane, was found to speed up the reactions by
factors of ∼2. The cyclohexadieno- (3 and 4) and
tetrahydronaphthaleno-fused (7) dipyrromethane esters were
unstable at room temperature and degraded rapidly during
purification. These compounds were introduced into sub-
sequent transformations without isolation. (Only compounds
that were isolated and fully characterized are identified in the
text by bold numbers). Dipyrromethane esters 3, 4, and 5 were
de-esterified and decarboxylated in a one-pot reaction upon
treatment with TFA, while benzyl esters 6 and 7 were first
converted to carboxylic acids by reduction on Pearlman’s
83
catalyst (Pd(OH) /C) and then introduced into the TFA-
2
mediated decarboxylation without isolation. De-esterification/
decarboxylation was carried out immediately prior to the
porphyrin synthesis, since α,α′-unsubstituted dipyrromethanes
are even more unstable than their ester precursors and degrade
rapidly in air, presumably as a result of oxidation and/or
Aromatization of precursors 13−17 into the target dibenzo-
(18−21) and dinaphthoporphyrins (22) requires the removal
of either two (13, 14, 17) or four (15, 16) hydrogens from each
C
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a
Scheme 2. Synthesis of β-Substituted Dipyrromethanes
a
Reagents and conditions: (a) p-TsOH, NBu Cl, CH Cl , r.t., 24 h (3), 48 h (4), 72 h (5). (b) p-TsOH, AcOH, 24 h (6), 48 h (7). (c) H /
4
2
2
2
83
Pd(OH) /C, THF, r.t., 24−48 h. (d) (i) TFA/CH Cl 1:1, 20 °C, 1 h; (ii) NaHCO .
2
2
2
3
exocyclic ring annealed with the macrocycle, whereas
dehydrogenation of less-saturated rings generally occurs much
treatment of 15 as either the free base or the Zn complex (Zn−
15) with excess DDQ in refluxing THF for 14 h did not show
any sign of conversion, while the oxidation in refluxing toluene
produced mixtures of aggregated inseparable products. Our
final targets in this study were phosphorescent Pt and Pd
complexes, and therefore, we turned our attention to the
2
,75
more easily.
The most common oxidant for aromatizations
is DDQ. Aromatizations may be inhibited by the formation of
porphyrin dications if the basicities of the corresponding free
6
9
bases are high. The latter is typical of highly nonplanar
porphyrins, which must be converted into stable metal
methods developed earlier for the synthesis of similar Pt and Pd
6
9
69,70
complexes (e.g., with Pd, Pt, or Cu) prior to oxidation.
Planar meso-unsubstituted and 5,15-diarylporphyrins
tetraaryltetrabenzo- and tetranaphthoporphyrins.
Prior to
71
72,73
may
oxidation, Zn−15 and Zn−16 were demetalated and then
converted into Pt and Pd complexes (see below). The latter
were smoothly oxidized using excess DDQ in toluene over 10
h, yielding the desired complexes M−20 and M−21 (M = Pt,
Pd) in ∼79−92% yield.
be oxidized directly as free bases, although metalation usually
facilitates the reaction.
Porphyrin 17 was the easiest to aromatize in our series. The
transformation of Zn−17 into Zn−22 could be observed
immediately upon addition of DDQ, even at room temperature,
by the change of the color of the mixture from red to deep
green. Similarly, aromatization of porphyrins Zn−13 and Zn−
Insertion of Pt(II) into the precursor porphyrins 15 and 16
and the target porphyrins 18, 19, and 22 was performed either
8
5
in benzoic acid melt or using the microwave-assisted
86
1
3
4 occurred when they were treated with DDQ in THF for just
0−40 min, although heating was required. The Zn complexes
method. In the former approach, the free-base porphyrins
were heated with a 3−4-fold molar excess of Pt(acac) in
2
of 18, 19, and 22 were isolated in almost quantitative yields.
The corresponding free-base porphyrins were obtained by facile
demetalation with HCl.
benzoic acid at 130−135 °C for 2−6 h. Subsequent methanol
workup, chromatographic purification, and reprecipitation from
CH Cl /MeOH (1:50) afforded the Pt(II)−porphyrin com-
2
2
The aromatization of tetraalkoxycarbonylporphyrins 15 and
plexes in 20−56% yield. In spite of the moderate yields, the
85
16, however, proved to be much more difficult. For example,
benzoic acid method in our hands has proved to be general
D
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a
Scheme 3. Synthesis of Target Porphyrins
a
Reagents and conditions: (a) (i) Zn(OAc) ·2H O (10 equiv), MeOH, reflux, 2 h; (ii) DDQ (3 equiv), r.t., 2 h. (b) (i) Zn(OAc) ·2H O (10 equiv),
2
2
2
2
C H , Ar, reflux, 2 h; (ii) air, reflux, 12−18 h. (c) DDQ (3 equiv), THF, reflux, 30−40 min. (d) HCl conc./CH Cl . (e) Pt insertion: (method 1)
6
6
2
2
Pt(acac) /benzoic acid, 130−135 °C, 2−6 h; (method 2) Pt(acac) /PhCN, microwave, 250 °C (∼200 kPa, 105−145 W), 40 min. Pd insertion:
2
2
Pd(Ac) /PhCN, microwave, 250 °C (∼200 kPa, 105−145 W), 40 min. (f) DDQ (5 equiv), toluene, reflux, 10 h. (g) DDQ (3 equiv), THF, r.t., 10
2
min.
and frequently leads to success when other methods, such as
commonly used refluxing in benzonitrile, fail. However, in this
particular instance, the best results were achieved using the
microwave-assisted insertion, developed by Bruckner and co-
a separate account. Because of the presence of meso-aryl
substituents and alkoxycarbonyl groups, all of the porphyrins
were found to be well-soluble in a range of organic solvents
(e.g., toluene, CH Cl , THF, DMF, and DMA), where they
2
2
8
6
workers. Microwave treatment of mixtures of the free-base
showed no signs of aggregation at the concentrations required
for optical measurements and above (up to 10− M). The
measurements were performed in dimethylacetamide (DMA).
This solvent is especially convenient because of its high boiling
point (165 °C), making it possible to deoxygenate solutions by
5
porphyrins and Pt(acac) (3−4 equiv) in benzonitrile for 40
2
min gave the corresponding Pt complexes in 92% to
quantitative yield. Similarly, the Pd complexes were obtained
in nearly quantitative yield.
Overall, the developed reaction sequences allowed us to
prepare the target Pt and Pd porphyrins in yields of 5−15%
relative to the starting pyrrole esters (Scheme 2). The methods
do not require expensive reagents and can be scaled to gram
quantities.
Photophysical Properties. This section provides a brief
overview of the photophysical properties of the newly
synthesized porphyrins, while leaving the detailed analysis for
inert gas bubbling (Ar or N ) at room temperature without
experiencing significant losses in the solution volume.
2
The optical absorption features of the Pt and Pd complexes
of the synthesized porphyrins are very similar to each other,
with the bands of the Pd porphyrins being red-shifted by 5−15
nm relative to the Pt complexes. The triplet lifetimes of the Pd
complexes Pd−19 through Pd−22 are 8−10 times longer than
those of the respective Pt porphyrins, while their phospho-
E
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rescence quantum yields are about 2 times lower (Table 1).
87
These trends are common for Pt and Pd porphyrins, and
Table 1. Selected Photophysical Parameters for Pt and Pd
Complexes of the Synthesized Porphyrins in DMA
absorption λmax (nm)
phosphorescence
a
complex
B band
Q band
λmax (nm)
Φ , τ (μs)
ph
Pt−18
Pt−19
Pt−20
Pt−21
Pt−22
Pd−19
Pd−20
Pd−21
Pd−22
401
402
412
405
423
417
427
421
435
556
559
568
562
593
570
581
574
605
685
686
680
675
753
706
702
696
774
0.31, 90
0.34, 92
0.37, 80
0.37, 83
0.11, 49
0.15, 850
0.16, 730
0.16, 730
0.04, 410
a
The phosphorescence quantum yields (Φ) and lifetimes (τ) were
measured at 22 °C in deoxygenated solutions. The fluorescence of
rhodamine 6G in EtOH (Φ = 0.95) was used as a standard. For
comparison, under these conditions the fluorescence quantum yield of
8
8
fl
tetraphenylporphyrin (H TPP) in deoxygenated C H is 0.055, and
2
6
6
the phosphorescence quantum yield of Pt meso-tetraphenyltetrabenzo-
porphyrin (Ph TBP) in deoxygenated DMF is 0.085.
4
below we discuss only Pt complexes Pt−18 through Pt−22,
while the properties of the Pd complexes can be inferred by
analogy.
Figure 1. (A) Absorption and (B) phosphorescence spectra of
porphyrins Pt−18 through Pt−22 in DMA. The absorption spectra
were normalized by the corresponding Q-band maxima; the inset
shows the zoomed Q-band region. The phosphorescence spectra were
normalized by the respective phosphorescence quantum yields (Table
The linear absorption and phosphorescence emission spectra
of porphyrins Pt−18 through Pt−22 are shown in Figure 1, and
the relevant data are compiled in Table 1. Similar graphs for the
Pd complexes are shown in Figure S2 in the Supporting
Information. It should be noted that the absorption features of
ZnDBPs Zn−18 and Zn−19 (Figure S3 in the Supporting
Information) correspond well with the literature data on similar
1
).
The transitions in Pt−18 through Pt−21 are polarized in the
4
8
Zn complexes.
directions in which the syn-DBP molecules have diameters
larger than those of regular Pt porphyrins but smaller than
those of PtTBPs. In syn-DNP Pt−22, on the other hand, the
macrocycle diameter along the polarization axes is similar to
that of PtTBPs. The energies of the spectral bands generally
follow this simple relationship: the “longer” the dipole, the
lower the energy of the absorption band. Of course, for
accurate quantitative interpretation of the spectroscopic data, a
detailed computational/photophysical study such as that
The absorption spectra of all of the synthesized Pt
porphyrins exhibit well-defined, narrow bands, resembling in
that way the spectra of the fully symmetrical Pt tetrabenzo-
2
5,32,35,71
porphyrins (PtTBPs) (D4h symmetry).
The Soret (or
B) (S ), Q (S ), and phosphorescence (T ) bands of
2
1
1
porphyrins Pt−18 through Pt−21 occupy somewhat inter-
mediate positions between the bands of regular nonextended Pt
8
7,89,90
25,32,35,71
porphyrins (PtPs)
and those of PtTBPs.
The Q
48
band of Pt−22 (λ = 593 nm) is bathochromically shifted,
performed recently for Zn benzoporphyrins will be required.
In the series of synthesized syn-DBPs, porphyrins Pt−20 and
Pt−21 exhibit the most bathochromically shifted Q and B
bands, while their phosphorescence maxima are the most
hypsochromically shifted. With the assumption that the
max
3
2,71
approaching the Q bands of PtTBPs (∼605−615 nm),
while its B band is also red-shifted, but broadened similar to the
B bands of tetranaphthoporphyrins. These observations can
be rationalized, at least to a first approximation, by recalling that
Q and B bands in regular symmetrical porphyrins are composed
of orthogonally polarized transitions (Q and Q , B and B )
71
phosphorescent triplet states (T ) in all of these porphyrins
1
are derived from the same electronic configurations as the S1
x
y
x
y
that are formed by configuration interaction involving single-
(or S ) states, the data for Pt−20 and Pt−21 appear to be
2
electron excitations between pairs of nearly degenerate
consistent with the expansion of the π-conjugation onto the
carbonyl groups in the benzo rings in the macrocycles. This
expansion further destabilizes one of the HOMOs, causing a
red shift in the absorption, but at the same time decreases the
exchange energy (2J) because of the increase in the size of the
66
HOMOs and LUMOs. π-Extension lifts the degeneracy of
one of the HOMOs (a ), leading to a spectral red shift as well
2
u
6
,91
to an increase in the oscillator strength of the Q band.
Just
as in fully symmetrical PtTBPs, the orthogonal transition
dipoles in Pt syn-DBPs and Pt syn-DNPs are identical to each
other. Consequently, the x and y bands are fully superimposed,
giving rise to narrow spectral lines, similar to those of PtTBPs.
In contrast, in anti-DBPs, the x and y dipoles are not equivalent,
resulting in multiple spectral lines in both the Q- and B-band
9
2
π-system, narrowing the S −T gap and raising the energy of
1
1
the T state. Between these two porphyrins, Pt−20 exhibits
1
more bathochromically shifted bands than Pt−21, which is
consistent with the presence of only one meso-aryl substituent
in the latter. The meso-aryl groups in 5,15-diarylporphyrins (see
the X-ray structure in Figure 2 and the computed structures in
4
8
regions.
F
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
in deoxygenated DMA at 22 °C is 0.42. Our setup allows time-
resolved acquisition of phosphorescence upon excitation by
trains of femtosecond pulses from a tunable Ti:sapphire laser
(
see the Supporting Information for details). In Pt porphyrins,
because of the ultrafast S → T intersystem crossing and
1
1
therefore nearly quantitative formation of the triplet
8
7,90,94
state,
the corrected integrated intensity of the phosphor-
escence (normalized by the phosphorescence quantum yield
and plotted against the excitation wavelength) is directly
suitable for comparisons of 2PA cross sections of different
porphyrins. To ensure the 2P excitation regime, the signal in all
cases was confirmed to exhibit a strictly quadratic power
dependence (slope of the log−log plot = 2.00 ± 0.05). The
results are summarized in Figure 3 (for the numerical data, see
Table S2 in the Supporting Information).
Figure 2. (top) ORTEP view of the X-ray crystallographic structure of
porphyrin Pt−19 (50% thermal ellipsoids) with two stacked
nonidentical porphyrin molecules in the cell. All of the hydrogen
atoms have been omitted for clarity. (bottom) View of the plain
porphyrin skeleton of Pt−19, showing the small nonplanar distortion
of the macrocycle and tilts of the two meso-aryl substituents. The aryl
group between the two benzo rings is rotated by 83° relative to the
porphyrin mean-square plane.
Figure 3. Relative 2PA cross sections (integrated intensities of 2P-
excited phosphorescence normalized by the phosphorescence
quantum yield) of PtTCHP (D ) and the synthesized Pt porphyrins.
The data are scaled in such a way that the relative 2PA cross section of
the most absorbing porphyrin, Pt−21, equals 1.0 at 770 nm.
Figure S1 in the Supporting Information) are almost
4
h
34
perpendicular to the porphyrin plane, and yet they participate
in the conjugation with the macrocycle, thereby inducing small
93
red shifts in the absorption spectra.
The phosphorescence quantum yields of Pt syn-DBPs (Φ ≈
It can be seen that the apparent 2PA cross sections of Pt syn-
DBPs and syn-DNPs are indeed larger than that of the reference
PtTCHP. In the case of Pt−22, measurements could not be
conducted at wavelengths shorter that 860 nm because of the
interfering linear excitation into the triplet state (S → T ) by
ph
0
.35) were found to be among the highest reported to date for
phosphorescent tetrapyrroles. The quantum yields were
measured against the fluorescence of rhodamine 6G in EtOH
8
8
(
Φ = 0.95), and the emission spectra were corrected for the
fl
0
1
wavelength dependences of the detector, excitation source, and
monochromators. It should be noted that under the same
conditions the phosphorescence quantum yield of Pt meso-
the femtosecond pulses. (It should be kept in mind that in Pt
porphyrins, because of the very strong spin−orbit coupling,
spin-forbidden S → T transitions may gain significant dipole
0
1
9
5,96
tetraphenyltetrabenzoporphyrin (Ph TBP) in deoxygenated
strength.
) The most striking enhancement occurs in the
4
DMF was determined to be 0.085, which is substantially
case of porphyrins Pt−20 and Pt−21 in which the benzo rings
contain alkoxycarbonyl groups, as their apparent 2PA cross
sections near 770 nm are ∼25-fold larger than that of PtTCHP
(Table S2 in the Supporting Information). However, it is also
clear that in all of the porphyrins the 2PA continues to rise past
800−810 nm, i.e., twice the maximum of the Soret band.
Apparently, breaking the center-of-inversion symmetry is not
the dominant factor in the enhancement of the 2PA, and the
most strongly absorbing 2PA states in these porphyrins are still
not the same as their linear 1P states.
7
,35
lower than reported previously.
Pt syn-DBPs are in line with their relatively planar structures
Figure 2 and Figure S1 in the Supporting Information), in
The high emission yields of
(
accordance with the previously observed correlation between
nonplanarity of π-extended porphyrins and enhanced non-
34
radiative triplet decay. On average only ∼60% of the triplet
state in Pt−18 through Pt−21 decays via the nonradiative
channel (Table S1 in the Supporting Information), while in,
e.g., highly nonplanar PtPh TBPs this fraction is larger than
4
9
0%. In DNP Pt−22, the proportion of the T1 → S0
These preliminary findings raise the following questions:
what are the 2P-absorbing states in π-extended Pt porphyrins,
and why do alkoxycarbonyl groups cause such a pronounced
enhancement of the 2PA? One obvious notion is that the
alkoxycarbonyl groups in porphyrins Pt−20 and Pt−21
significantly polarize these molecules. For example, on the
basis of DFT calculations (B3LYP/6-31G*), the ground-state
dipole moment of a Zn porphyrin analogous to Zn−20 is 6.12
D, whereas for the analogue of Zn−19 it is only 0.85 D (Figure
intersystem crossing is also increased to ∼90% because of the
narrower T −S gap.
1
0
In order to estimate the performance of porphyrins Pt−18
through Pt−22 under 2P excitation, we compared their
phosphorescence outputs to that of a regular symmetrical Pt
71
porphyrin, i.e., Pt tetracyclohexenoporphyrin (PtTCHP),
which possesses D4h symmetry (Figure S4 in the Supporting
Information). The phosphorescence quantum yield of PtTCHP
G
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
S1 in the Supporting Information). Such polarization could in
principle lead to an enhancement of 2PA, assuming that in the
excited state the dipole moment increases (or changes sign).
These and other pertinent photophysical questions should be
addressed in a separate study, for which the present work sets
the necessary synthetic stage.
1.0 mmol) was added, and the reaction mixture was stirred at room
temperature under Ar for 1.5 h. NaOH (1.2 g, 30 mmol) was added to
the mixture, and the stirring was continued for 45 min. The
precipitates were removed by filtration, and pyrrole was removed by
distillation in vacuum (∼1 mmHg, 18−20 °C). The residue was
purified by chromatography on a short silica gel column (10 cm,
CH Cl ) to give crude 5-(3,5-dibutoxycarbonylphenyl)-
97
2
2
dipyrromethane (2a) (3.6 g).
To a solution of 2a (3.6 g, 8.5 mmol) in dry DMF (10 mL) was
CONCLUSION
■
We have developed a synthesis of Pt and Pd complexes of
nonfully symmetrical syn-DBPs and syn-DNPs with solubilizing
substituents. These macrocycles possess nearly planar struc-
tures and phosphoresce in solutions at ambient temperatures
with exceptionally high quantum yields. Preliminary evaluation
showed that structural asymmetry causes an increase in the 2PA
into 1P-allowed states; however, much stronger 2P-absorbing
states are positioned at higher energies. Detailed photophysical
studies of the newly synthesized porphyrins are in progress.
added POCl (2.74 g, 17.9 mmol) dropwise at 0 °C under Ar. The
3
reaction mixture was stirred for 1 h at room temperature, poured into
a saturated aqueous solution of sodium acetate (250 mL), extracted
with CH Cl (3 × 100 mL), and dried over Na SO . The solvent was
2
2
2
4
removed in vacuum, and the residue was purified by column
chromatography (silica gel, CH Cl /EtOAc = 4:1) to give crude 1,9-
2
2
diformyl-5-(3,5-dibutoxycarbonylphenyl)dipyrromethane (2b) (3.3 g).
n-Propylamine (15 mL, 183 mmol) was added to 2b (3.3 g, 6.9
mmol), and the mixture was stirred for 1 h at room temperature.
Excess n-propylamine was removed in vacuum to give the title
compound 2 as a dark-orange solid (mp 112−114 °C). Yield: 3.86 g
1
3
EXPERIMENTAL SECTION
(69% over 3 steps). H NMR (CDCl ) δ (ppm): 0.90 (6H, t, J = 7.4
3
■
3
Hz, −CH ), 0.95 (6H, t, J = 7.4 Hz, −CH ), 1.38−1.49 (4H, m,
Descriptions of materials, equipment, and general protocols are
provided in the Supporting Information. HRMS data are reported for
the highest-intensity peak in the isotope mass distribution and
compared to the corresponding peak in the distribution simulated by
3
3
3
3
−
6
CH −), 1.60−1.78 (8H, m, −CH −), 3.41 (4H, dd, J = 6.8, J =
2
2
1
2
3
.9 Hz, −NCH −), 4.30 (4H, t, J = 6.7 Hz, −OCH −), 5.59 (1H, s,
2
2
3
3
broad, −CH−), 5.96 (2H, d, J = 3.6 Hz, Pyr), 6.50 (2H, d, J = 3.6
4
1
Hz, Pyr), 7.72 (2H, s, −NH−), 8.08 (2H, d, J = 1.4 Hz, Ar), 8.55
the mass spectrometer software. The abbreviations used in the H
NMR peak assignments are shown on p S20 in the Supporting
4
13
(
1H, t, J = 1.4 Hz, Ar). C NMR (CDCl ) δ (ppm): 11.7, 13.7, 19.2,
3
2
4.2, 30.6, 44.1, 62.3, 65.2, 109.6, 114.8, 114.9, 129.4, 130.4, 131.2,
Information.
1
1
C
33.6, 135.6, 135.7, 142.2, 151.4, 165.7. MALDI-TOF (m/z): calcd for
, 9 - B i s ( N , N - d i m e t h y l a m i n o m e t h y l ) - 5 - ( 4 -
+
methoxycarbonylphenyl)dipyrromethane (1). 4-Methoxycarbo-
33
H
44
N
4
O
4
560.34, found 561.24 [M + H] . HRMS (ESI-TOF) m/z:
+
nylbenzaldehyde (2.40 g, 15 mmol) and pyrrole (100 g, 1.5 mol) were
[M + H] calcd for C33H N O 561.34349, found 561.34371.
45 4 4
mixed together and purged with Ar for 10 min. InCl (0.3315 g, 1.5
α , α ′ - B i s ( t e r t - b u t o x y c a r b o n y l ) - m e s o - ( 3 , 5 -
dibutoxycarbonylphenyl)methylenebis(1,1′-(5,6-dibutoxycar-
bonyl-4,5,6,7-tetrahydro-2H-isoindole)) (5). p-Toluenesulfonic
acid (0.090 g, 0.48 mmol) and tert-butylammonium chloride (0.135
g, 0.48 mmol) were added to a solution of 1-tert-butoxycarbonyl-5,6-
3
mmol) was added, and the reaction mixture was stirred under Ar at
room temperature for 1.5 h. NaOH (1.8 g, 43.5 mmol) was added to
the mixture, and stirring was continued for additional 45 min. The
precipitates were removed by filtration, and pyrrole was removed by
distillation in vacuum (∼1 mmHg, 18−20 °C); the remaining traces of
pyrrole were removed by washing the residue with hexane (3 × 30
mL). The remaining material was dissolved in hot MeOH (100−150
mL). 5-(4-Methoxycarbonylphenyl)dipyrromethane (1a) precipitated
from solution as pale-yellow crystals upon cooling of the mixture to 0
7
1
dibutoxycarbonyl-4,5,6,7-dihydro-2H-isoindole (2 g, 4.75 mmol) and
7
0
3
,5-dibutoxycarbonylbenzaldehyde (0.727 g, 2.4 mmol) in CH Cl
2 2
(50 mL). The reaction mixture was stirred at room temperature under
Ar for 72 h. Small amounts of p-toluenesulfonic acid (0.045 g, 0.24
mmol) and tert-butylammonium chloride (0.07 g, 0.25 mmol) were
added to the reaction mixture after 24 h and then again after 48 h. The
reaction progress was monitored by TLC until the spot corresponding
to aldehyde disappeared. The mixture was diluted with CH Cl (100
°
C. It was collected by filtration and dried in vacuum. Pale-yellow
1
crystalline powder (mp 153−154 °C). Yield: 0.82 g (62%). H NMR
3
(
DMSO-d ) δ (ppm): 2.07 (12H, s, −NCH ), 3.26 (4H, d, J = 2.51
2
2
6
3
mL), washed with NaHCO (10% aq., 50 mL) and brine (50 mL), and
Hz, −CHN(CH ) ), 3.81 (3H, s, −OCH ), 5.37 (1H, s, −CH−), 5.53
3
3
2
3
3
3
3
dried over Na SO . The solvent was removed in vacuum, and the
(
1H, d, J = 2.8 Hz, Pyr), 5.54 (1H, d, J = 2.8 Hz, Pyr), 5.72 (1H, d, J
2
4
3
3
residue was purified by column chromatography (silica gel, CH Cl /
=
2.8 Hz, Pyr), 5.73 (1H, d, J = 2.8 Hz, Pyr), 7.23 (2H, d, J = 8.3 Hz,
2
2
3
THF = 50:1) to give the title compound 5 as an orange oil. Yield 2.23
Ar), 7.85 (2H, d, J = 8.3 Hz, Ar), 10.51 (2H, s, −NH).
1
g (83%). H NMR (CDCl ) δ (ppm) (mixture of conformers): 0.83−
To a solution of 1a (0.9468 g, 2.9 mmol) in CH Cl (50 mL), N,N-
3
2
2
3
0
.91 (12H, m, −CH ), 0.95 (6H, t, J = 7.3 Hz, −CH ), 1.22−1.50
dimethylethyleneiminium iodide (Eschenmoser’s salt) (1.3871 g, 6.4
mmol) was added. The reaction mixture was stirred for 1 h at room
temperature and then diluted with CH Cl (350 mL), and K CO
3
3
3
(
16H, m, −CH −), 1.50−1.53 (18H, m, tBu), 1.48−1.60 (4H, m,
2
−
CH −), 1.68−1.78 (4H, m, −CH −), 2.24−2.47 (2H, m, −CHH−),
2
2
2
2
2
(
10% aq., 350 mL) was added. The organic layer was separated,
2.55−2.80 (2H, m, −CHH−), 2.99−3.27 (8H, m, −CHH−, −CH−),
3
washed with K CO (10% aq., 3 × 350 mL), dried over Na SO , and
concentrated in vacuum. The title compound was precipitated from
3.92−4.10 (8H, m, −OCH
2
−), 4.30 (4H, t, J = 6.6 Hz, −OCH
2
−),
2
3
2
4
5.50−5.54 (1H, m, broad, −CH−), 7.88−7.95 (2H, m, Ar), 8.39−8.44
13
CH Cl upon addition of hexanes, collected by filtration, and dried in
(1H, m, Ar), 8.52−8.50 (2H, m, −NH−). C NMR (CDCl ) δ
3
2
2
vacuum. Pale-yellow crystalline powder (mp 111−113 °C). Yield:
(ppm) (mixture of conformers): 13.62, 13.64, 13.71, 19.01, 19.04,
19.1, 19.2, 22.2, 22.3, 22.4, 22.5, 23.5, 23.6, 23.7, 23.8, 28.39, 28.42,
30.3, 30.47, 30.52, 30.54, 30.6, 40.56, 40.58, 40.7, 40.8, 40.90, 40.94,
40.96, 41.00, 41.1, 64.45, 64.49, 64.55, 64.60, 64.63, 65.3, 80.63, 80.65,
80.69, 116.9, 117.17, 117.23, 117.3, 118.76, 118.84, 118.9, 119.0,
125.3, 125.4, 125.5, 128.1, 128.3, 128.4, 128.5, 129.77, 129.8, 129.9,
131.85, 131.90, 133.2, 133.3, 139.5, 139.7, 139.8, 160.68, 160.70,
160.9, 165.25, 165.33, 172.6, 172.7, 172.76, 172.79, 173.01, 173.02.
0
.8223 g (62%). 1H NMR (DMSO-d ) δ (ppm): 2.07 (12H, s,
6
3
−
NCH ), 3.26 (4H, d, J = 2.51 Hz, −CHN(CH ) ), 3.81 (3H, s,
3
3 2
3
−
OCH ), 5.37 (1H, s, −CH−), 5.53 (1H, d, J = 2.8 Hz, Pyr), 5.54
3
3
3
3
(
=
1H, d, J = 2.8 Hz, Pyr), 5.72 (1H, d, J = 2.8 Hz, Pyr), 5.73 (1H, d, J
3
3
2.8 Hz, Pyr), 7.23 (2H, d, J = 8.3 Hz, Ar), 7.85 (2H, d, J = 8.3 Hz,
Ar), 10.51 (2H, s, −NH). C NMR (CDCl ) δ (ppm): 44.2, 44.9,
2.0, 56.6, 107.1, 107.5, 107.6, 128.4, 128.6, 128.9, 129.0, 129.8,
13
3
5
1
31.70, 131.74, 147.65, 147.67, 167.0. HRMS (ESI-TOF) m/z: [M +
MALDI-TOF (m/z): calcd for C63
H
90
N
2
O
16 1130.63, found 1153.42+
+
+
+
H] calcd for C H N O 395.24413, found 395.24368.
[M + Na] , 1169.39 [M + K] . HRMS (ESI-TOF) m/z: [M + H]
23
31
4
2
1
, 9 - B i s ( N - P r o p y l i m i n o m e t h y l ) - 5 - ( 3 , 5 -
calcd for C H N O 1131.63623, found 1131.63613.
63
91
2
16
dibutoxycarbonylphenyl)dipyrromethane (2). 3,5-Dibutoxycar-
α,α′-Bis(benzyloxycarbonyl)methylenebis(1,1′-(5,6-dime-
thoxycarbonyl-4,5,6,7-tetrahydro-2H-isoindole)) (6). p-Toluene-
sulfonic acid (0.033 g, 0.175 mmol) was added to a solution of 1-
bonylbenzaldehyde (3.06 g, 10 mmol) and pyrrole (66 g, 1.0 mol)
were mixed together and purged with Ar for 10 min. InCl (0.221 g,
3
H
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
benzyloxycarbonyl-5,6-dimethoxycarbonyl-4,5,6,7-dihydro-2H-isoin-
above for dipyrromethane 5. Decarboxylation of 4 gave crude
dipyrromethane 9 (0.46 g).
71
dole (1.3 g, 3.5 mmol) and dimethoxymethane (0.133 g, 1.75 mmol)
in acetic acid (25 mL), and the reaction mixture was stirred at room
temperature under Ar for 24 h. The mixture was poured into cold
water (80 mL), and the formed precipitate was collected by filtration
and dried in vacuum. The resulting solid was dissolved in MeOH (20
mL) and precipitated upon addition of water (10−15 mL) at 0 °C.
The precipitate was collected by centrifugation, washed with water (3
Dipyrromethane 7 was prepared from 1-benzyloxycarbonyl-4,9-
dihydro-2H-benzo[f ]isoindole (1.175 d, 3.88 mmol) and 3,5-
dibutoxycarbonylbenzaldehyde (0.593 g, 1.94 mmol) following the
procedure described above for dipyrromethane 6. Hydrogenolysis
followed by decarboxylation gave crude dipyrromethane 12 (0.35 g).
MALDI-TOF (m/z): calcd for C H N O 626.31, found 627.13 [M
41
42
2
4
+
×
20 mL), and dried in vacuum to give the title compound as a white
+ H] .
1
solid (mp 104−106 °C). Yield 1.23 g (93%). H NMR (CDCl ) δ
To avoid degradation, dipyrromethanes 3, 4, 7, 8, 9, and 12 were
immediately introduced into their respective subsequent syntheses
without purification.
3
(
3
3
ppm) (mixture of conformers): 2.65−2.78 (2H, m, −CHH−), 2.90−
.03 (2H, m, −CHH−), 3.04−3.24 (6H, m, −CHH−, −CH−), 3.26−
.38 (2H, m, −CH−), 3.62−3.69 (12H, m, −OCH ), 3.69−3.81 (2H,
5-Phenyl-15-(p-methoxycarbonylphenyl)-syn-dibenzopor-
3
7
3
m, −CH −), 5.17−5.33 (4H, m, −CH Ph), 7.25−7.34 (10H, m, Ar),
9
conformers): 21.80, 21.87, 21.92, 21.98, 22.4, 22.5, 22.6, 23.7, 23.76,
phyrin (18). 1 (0.5664 g, 1.44 mmol) and 8 (0.47 g, 1.44 mmol)
2
2
13
.30−9.48 (2H, m, −NH−). C NMR (CDCl ) δ (ppm) (mixture of
were dissolved in methanol (145 mL), and the reaction mixture was
3
purged with Ar. An excess of Zn(OAc) ·2H O (3.1409 g, 14.4 mmol)
2 2
2
1
1
1
3.83, 23.9, 24.0, 40.7, 40.8, 51.4, 51.95, 52.00, 65.7, 65.8, 116.42,
16.48, 116.54, 116.58, 126.2, 126.5, 126.6, 127.66, 127.68, 127.71,
27.90, 127.92, 128.0, 128.4, 128.5, 129.15, 129.24, 136.2, 161.4,
62.3, 173.33, 173.35, 173.36, 173.39, 173.45, 173.49, 173.52, 173.55.
was added, and the reaction mixture was refluxed for 2 h, during which
time the solution color turned deep red. After 2 h, the reaction mixture
was cooled to room temperature, and DDQ (0.9820 g, 4.3 mmol) was
added. The mixture was allowed to react overnight. The methanol was
evaporated under reduced pressure, and the product was purified by
MALDI-TOF (m/z): calcd for C H N O 754.27, found 752.96 [M
4
1
42
2
12
+
+
+
−
H] , 776.95 [M + Na] , 792.92 [M + K] . HRMS (ESI-TOF) m/z:
column chromatograpy (silica gel, CH Cl ). The fraction containing
2 2
+
[
M + H] calcd for C H N O 755.28099, found 755.27822.
the target porphyrin (as monitored by UV−vis spectroscopy) was
collected and evaporated to dryness to give crude Zn−13.
41
43
2
12
meso-(3,5-Dibutoxycarbonylphenyl)methylenebis(1,1′-(5,6-
dibutoxycarbonyl-4,5,6,7-tetrahydro-2H-isoindole)) (10). Di-
pyrromethane ester 5 (1.98 g, 1.75 mmol) was dissolved in CH Cl2
Zn−13 (0.14 g, 0.2 mmol) was treated with DDQ (0.145 g, 0.64
mmol) in refluxing THF (200 mL) during 30 min. The reaction
progress was monitored by UV−vis spectroscopy, whereby samples
were analyzed every 10 min. The reaction was stopped when no more
changes were detected in the spectra. The reaction mixture was
concentrated in vacuum and subjected to column chromatography
(silica gel, CH Cl ). After solvent removal and drying in vacuum, Zn−
2
(15 mL), and the solution was cooled to 0 °C on an ice bath. TFA (15
mL) was added dropwise to the solution under Ar. The ice bath was
removed, and the reaction mixture was stirred at room temperature for
1
NaHCO (10% aq., 50 mL) and brine (50 mL), and dried over
Na SO . The solvent was removed in vacuum, and the residue was
.5 h. The mixture was diluted with CH Cl (100 mL), washed with
2 2
3
2
2
18 was isolated as a purple crystalline powder. Yield 0.13 g (13% over
2
4
1
purified by column chromatography (silica gel, CH Cl /THF, gradient
two steps). UV−vis (THF) λ
(nm): 427, 561, 599. H NMR
2
2
max
3
from 15:1 to 2:1) to give crude dipyrromethane 10 as a dark-brown oil
0.92 g). The thus-obtained crude dipyrromethane 10 was used
(CDCl ) δ (ppm): 4.11 (3H, s, OCH ), 7.09 (2H, d, J = 8.0 Hz,
3
3
3
3
(
−Bn−), 7.59 (2H, dd, J
1
= J
2
= 7.5 Hz, −Bn−), 7.87−7.95 (4H, m,
3
immediately in the porphyrin synthesis (see below).
−Bn−, Ph), 8.01−8.09 (3H, m, Ph), 8.19 (2H, d, J = 8.3 Hz, Ar), 8.40
3
3
3
Methylenebis(1,1′-(5,6-dibutoxycarbonyl-4,5,6,7-tetrahy-
dro-2H-isoindole)) (11). Dipyrromethane ester 6 (1.23 g, 1.63
mmol) was dissolved in THF (50 mL), and the solution was purged
with Ar for 10 min. Pearlman’s catalyst (0.2 g) was added, and the
reaction mixture was purged with Ar again for 10 min and then with
H for 15−20 min. The mixture was kept under vigorous stirring
overnight under H (1 atm). The mixture was purged with Ar and then
passed through Celite to remove the catalyst. The resulting solution
was concentrated in vacuum to give crude α,α′-bis(carboxy)-
methylenebis(1,1′-(5,6-dibutoxycarbonyl-4,5,6,7-tetrahydro-2H-isoin-
dole)) (6a) (0.936 g) as a slightly pink viscous oil. MALDI-TOF (m/
(2H, d, J = 8.3 Hz, Ar), 8.82 (2H, d, J = 4.3 Hz, Pyr), 9.07 (2H, d, J
3
= 4.3 Hz, Pyr), 9.25 (2H, d, J = 7.5 Hz, −Bn−), 10.20 (2H, s, meso-
H). MALDI-TOF (m/z): calcd for C H N O Zn 684.07, found
684.36 [M] .
Zn−18 (0.020 g, 0.029 mmol) was dissolved in CH Cl (35 mL),
42
26
4
2
83
+
2
2
2
and the mixture was shaken with HCl (20% aq., 2 × 35 mL) in a
separatory funnel. The organic layer was washed with water (30 mL)
and dried over Na SO . The solvent was removed in vacuum, and the
2
2
4
solid was subjected to column chromatography (silica gel, CH Cl ).
2
2
Target porphyrin 18 was isolated as a purple crystalline powder (mp
>300 °C). Yield 0.018 g (100%). UV−vis (THF) λ (nm): 420, 527,
max
+
1
z): calcd for C H N O 574.18, found 596.90 [M + Na] , 612.88
560, 585, 641. H NMR (CDCl ) δ (ppm): −2.00 to −1.91 (1H, m,
27
30
2
12
3
+
[
M + K] .
Crude 6a (0.936 g, 1.63 mmol) was dissolved in THF (5 mL)/
CH Cl (20 mL), and the solution was cooled to 0 °C on an ice bath.
broad), −1.71 to −1.58 (1H, m, broad), 4.14 (3H, s, −OCH ), 7.33
3
3
3
3
(2H, d, J = 8.1 Hz, Ph), 7.71 (2H, dd, J = 7.9, J = 7.3 Hz, −Bn−),
1
2
3
3
2
2
7.95 (2H, dd, J = 7.4, J = 7.3 Hz, −Bn−), 8.01−8.08 (3H, m, Ph),
1
2
TFA (10 mL) was added dropwise to the solution under Ar. The ice
bath was removed, and the reaction mixture was stirred at room
temperature for 1 h. The mixture was diluted with CH Cl (100 mL),
washed with NaHCO (10% aq., 2 × 50 mL) and brine (50 mL), and
dried over Na SO . The solvent was removed in vacuum, and the
residue was purified on a short column (silica gel, 10 cm, CH Cl /
THF, 25:1) to give crude dipyrromethane 11 (0.42 g) as a dark-brown
oil. MALDI-TOF (m/z): calcd for C H N O 486.20, found 487.01
8.17−8.23 (2H, m, −Bn−), 8.32−8.38 (2H, m, Ar), 8.46−8.51 (2H,
m, Ar), 8.89−8.95 (2H, m, Pyr), 9.24−9.29 (2H, m, Pyr), 9.42−9.49
13
2
2
(2H, m, −Bn−), 10.47−10.53 (2H, m, meso-H). C NMR (CDCl ) δ
3
3
(ppm): 52.5, 99.1, 114.7, 120.4, 120.9, 125.5, 127.6, 127.6, 128.3,
129.2, 129.3, 129.6, 129.9, 130.0, 132.8, 134.5, 137.5, 139.9, 140.3,
141.3, 144.6, 144.8, 144.9, 145.8, 167.4. MALDI-TOF (m/z): calcd for
2
4
2
2
+
C H N O 620.22, found 621.69 [M + H] . HRMS (ESI-TOF) m/z:
[M + H] calcd for C H N O 621.22848, found 621.22687.
42
28
4
2
+
25
30
2
8
42 29 4 2
+
[
M + H] . The thus-obtained 11 was used immediately in the
5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-dibenzoporphyr-
in (19). 2 (0.373 g, 0.67 mmol) and 9 (0.350 g, 0.67 mmol) were
dissolved in benzene (65 mL), and the solution was purged with Ar.
Zn(OAc) ·2H O was added in excess (1.45 g, 6.7 mmol), and the
subsequent porphyrin synthesis.
Dipyrromethanes 3, 4, 7, 8, 9, and 12. Dipyrromethane 3 was
prepared from 2-tert-butoxycarbonyl-4,7-dihydro-2H-isoindole (1.18 g,
7
3
2
2
5
.4 mol) and benzaldehyde (0.285 g, 2.7 mmol) following the
mixture was heated under reflux with a Dean−Stark trap for 2 h under
Ar. The reaction mixture was purged with air, and the refluxing was
continued under air for 12 h. The reaction progress was monitored by
UV−vis spectroscopy. The solvent was removed in vacuum, and the
remaining material was subjected to column chromatography (silica
gel, CH Cl /EtOAc = 20:1). The band containing the target porphyrin
procedure described above for dipyrromethane 5. Decarboxylation of 3
gave of crude dipyrromethane 8 (0.47 g).
Dipyrromethane 4 was prepared from 1-tert-butoxycarbonyl-4,7-
dihydro-2H-isoindole (0.8672 g, 4 mmol) and 3,5-dibutoxycarbonyl-
benzaldehyde (0.606 g, 2 mmol) following the procedure described
2
2
I
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
3
3
was collected, and the solvent was removed in vacuum to give crude
Zn−14.
(2H, d, J = 1.4 Hz, Ar), 9.07 (2H, d, J = 4.3 Hz, Pyr), 9.12 (1H, dd,
3
3
3
3
J = J = 1.4 Hz, Ar), 9.17 (2H, d, J = 1.4 Hz, Ar), 9.59 (1H, dd, J
= J = 1.5 Hz, Ar), 9.82 (2H, s), 10.33 (2H, s, meso-H). C NMR
(CDCl ) δ (ppm): 13.7, 13.8, 19.2, 19.3, 30.6, 30.8, 65.6, 65.8, 98.3,
110.2, 119.7, 121.0, 125.3, 126.2, 127.1, 128.6, 129.0, 129.7, 130.1,
130.2, 130.3, 131.5, 132.5, 132.57, 132.63, 135.1, 137.7, 138.1, 138.2,
141.3, 141.5, 142.6, 144.0, 145.5, 146.5. MALDI-TOF (m/z): calcd for
C H N O 1062.46, found 1063.21 [M + H] . HRMS (ESI-TOF)
m/z: [M + H] calcd for C H N O 1063.46399, found 1063.46533.
5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dibutoxycarbonylcyclohexeno)porphyrin (15). Zn−15 was
synthesized similarly to porphyrin Zn−14 (see the synthesis of Zn−
19 above) from 2 (0.554 g, 1 mmol) and 10 (0.92 g, 1 mmol). The
reaction was complete in 16 h. The product was purified by column
chromatography (silica gel, CH Cl /EtOAc = 20:1) to give the title
1
3
2
1
13
Zn−14 (0.205 g, 0.2 mmol) was dissolved in THF (50 mL), and
DDQ (0.095 g, 0.42 mmol) was added. The reaction mixture was
heated under reflux for 40 min, and the reaction progress was
monitored by UV−vis spectroscopy. The solvent was removed under
vacuum, and the residue was diluted with CH Cl (100 mL), washed
2
3
2
2
+
with Na SO (2 × 50 mL) and water, and dried over Na SO . The
2
3
2
4
68 62
4
8
+
solution was concentrated, and the product was purified by column
68 63 4 8
chromatography (silica gel, CH Cl /EtOAc = 20:1) to give porphyrin
2
2
Zn−19 as a purple crystalline powder. Yield: 0.2 g (29% over two
steps). UV−vis (THF) λ (nm): 430, 561, 597. MALDI-TOF (m/z):
max
+
calcd for C H N O Zn 1024.34, found 1024.35 [M ].
60
56
4
8
Zn−19 (0.200 g, 0.195 mmol) was dissolved in CH Cl (150 mL).
2
2
The solution was vigorously shaken with HCl aq. (20%, 2 × 100 mL)
2
2
and then water (100 mL) and dried over Na SO . The solvent was
compound Zn−15 as a purple solid. Yield: 0.3 g (21%). MALDI-TOF
(m/z): calcd for C H N O Zn 1432.61, found 1432.87 [M] .
2
4
+
removed in vacuum, and the product was purified by column
80
96
4
16
chromatography (silica gel, CH Cl /EtOAc = 20:1) and further by
Zn−15 (0.300 g, 0.21 mmol) was dissolved in CH Cl (200 mL),
2
2
2
2
reprecipitation from CH Cl upon addition of MeOH/H O (∼50:0.5
and the solution was shaken with HCl aq. (20%, 2 × 100 mL) in a
separatory funnel, washed with water (100 mL), and dried over
Na SO . The solvent was removed in vacuum, and the product was
2
2
2
v/v). The precipitate was isolated by centrifugation, washed with
MeOH, and dried in vacuum to give the title compound as a purple
2
4
crystalline powder (mp 274−275 °C). Yield 0.17 g (91%). UV−vis
purified by column chromatography (silica gel, CH Cl /EtOAc =
20:1) and further by reprecipitation from CH Cl upon addition of
2 2
2 2
1
(
THF) λ (nm): 421, 529, 562, 584, 640. H NMR (CDCl ) δ
max
3
3
(
−
1
(
(
−
9
ppm): −2.04 to −1.52 (2H, m, broad), 0.89 (6H, t, J = 7.4 Hz,
MeOH. The precipitate was isolated by centrifugation, washed with
MeOH, and dried in vacuum to give the title compound as a purple
crystalline powder (mp 140−142 °C). Yield 0.27 g (94%). UV−vis
3
CH ), 0.96 (6H, t, J = 7.4 Hz, −CH ), 1.36−1.54 (8H, m, −CH −),
3
3
2
3
.70−1.85 (8H, m, −CH −), 4.42 (4H, t, J = 6.7 Hz, −OCH −), 4.48
2
2
3
3
1
4H, t, J = 6.7 Hz, −OCH −), 7.23 (2H, d, J = 8.1 Hz, −Bn−), 7.74
(THF) λ (nm): 409, 504, 535, 575, 629. H NMR (CDCl ) δ
2
max
3
3
3
3
3
2H, dd, J = J = 7.3 Hz, −Bn−), 8.07 (2H, dd, J = J = 7.3 Hz,
(ppm) (mixture of conformers): −3.02 to −2.58 (2H, m, broad),
1
2
1
2
3
Bn−), 8.87 (2H, d, J = 4.4 Hz, Pyr), 9.09−9.13 (4H, m, Ar), 9.15−
0.58−1.01 (24H, m, −CH ), 1.04−1.19 and 1.33−1.86 (32H, m,
3
3
.18 (1H, m, Ar), 9.30 (2H, d, J = 4.4 Hz, Pyr), 9.42−9.45 (1H, m,
−CH −), 2.97−3.27 (4H, m, −CHH−), 3.55−3.71 (4H, m,
2
3
13
Ar), 9.48 (2H, d, J = 7.9 Hz, −Bn−), 10.53 (2H, s, meso-H).
C
−CHH−), 3.83−4.02 (4H, m, −OCH −), 4.17−4.27 (4H, m,
2
NMR (CDCl ) δ (ppm): 13.69, 13.74, 19.2, 19.3, 30.6, 30.8, 65.6,
−OCH −), 4.40−4.49 (8H, m, −OCH −), 4.49−4.72 (4H, m,
3
2
2
3
6
1
1
5.8, 99.4, 112.2, 119.5, 121.1, 124.9, 127.7, 127.9, 130.0, 130.06,
30.14, 130.3, 131.6, 131.9, 137.1, 137.5, 138.4, 139.9, 140.3, 141.6,
−CH−), 8.94 (2H, d, J = 4.5 Hz, Pyr), 8.94−8.96 (1H, m, Ar), 8.97−
9.00 (1H, m, Ar), 9.07−9.12 (2H, m, Ar), 9.13−9.16 (1H, m, Ar),
3
42.3, 144.5, 144.9, 145.1, 165.8, 166.1. MALDI-TOF (m/z): calcd for
9.20−9.24 (1H, m, Ar), 9.38 (2H, d, J = 4.5 Hz, Pyr), 10.23−10.24
+
13
C H N O 962.43, found 963.11 [M + H] . HRMS (ESI-TOF) m/z:
(2H, m, meso-H). C NMR (CDCl ) δ (ppm) (mixture of
60
58
4
8
3
+
[
M + H] calcd for C H N O 963.43269, found 963.43134.
conformers): 13.3, 13.4, 13.67, 13.70, 13.74, 13.77, 13.77, 13.78,
18.75, 18.84, 19.14, 19.17, 19.21, 19.27, 19.31, 22.7, 24.0, 24.3, 28.1,
28.5, 29.7, 30.27, 30.34, 30.63, 30.65, 30.74, 40.7, 40.8, 41.8, 41.9, 64.6,
64.7, 64.9, 65.56, 65.66, 65.72, 101.6, 115.0, 115.1, 117.3, 129.1, 129.2,
60
59
4
8
5
,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-dinaphtho[2,3]-
porphyrin (22). Zn−17 was prepared similarly to Zn−14 (see the
synthesis of Zn−19 above) from 2 (0.316 g, 0.56 mmol) and 12
(
0.353 g, 0.56 mmol). The reaction was complete in 18 h. Zn−17 was
purified by column chromatography (silica gel, CH Cl /THF = 70:1).
1
30.03, 130.04, 130.06, 130.5, 130.6, 130.7, 131.1, 131.8, 136.6, 136.8,
2
2
137.0, 137.1, 138.59, 138.60, 140.0, 140.1, 141.8, 142.0, 142.3, 144.8,
144.9, 146.3, 165.5, 165.8, 166.0, 166.1, 172.5, 172.6, 173.1, 173.3.
MALDI-TOF (m/z): calcd for C H N O 1370.70, found 1371.14
MALDI-TOF (m/z): calcd for C H N O Zn 1128.40, found
6
8
64
4
8
+
1
128.52 [M] .
80
98
4
16
+
+
Zn−17 (0.09 g, 0.08 mmol) was dissolved in CH Cl (30 mL), and
2
2
[M + H] . HRMS (ESI-TOF) m/z: [M + H] calcd for C H N O
80 99 4 16
DDQ (0.038 g, 0.168 mmol) was added. The reaction mixture was
stirred for 10 min at room temperature and was monitored by UV−vis
spectroscopy. The solvent was removed in vacuum, and the remaining
material was dissolved in CH Cl (100 mL), washed with Na SO (2 ×
1
371.70497, found 1371.70702.
5
-(3, 5-Dibutoxycarbonylphenyl)- syn-bis(4′,5′-
dimethoxycarbonylcyclohexeno)porphyrin (16). Zn−16 was
synthesized similarly to porphyrin Zn−14 (see the synthesis of Zn−
19 above) from 2 (0.484 g, 0.86 mmol) and 11 (0.42 g, 0.86 mmol).
The reaction was complete in 12 h. The product was purified by
column chromatography (silica gel, CH Cl /THF, gradient from 50:1
to 25:1). Zn−16 was isolated as a purple crystalline powder. Yield: 0.2
g (24%). MALDI-TOF (m/z): calcd for C H N O Zn 988.29,
found 987.93 [M] .
2
2
2
3
5
0 mL) and water (50 mL), and dried over Na SO . The mixture was
2 4
chromatographed (silica gel, CH Cl /THF = 70:1), and Zn−22 was
2
2
isolated as a green crystalline powder. Yield: 0.08 g (13% over two
2
2
steps). UV−vis (THF) λ (nm): 452, 583, 623. MALDI-TOF (m/z):
max
+
calcd for C H N O Zn 1124.37, found 1124.05 [M] .
68
60
4
8
52 52
4
12
+
Zn−22 (0.080 g, 0.071 mmol) was dissolved in CH Cl (100 mL),
2
2
and the solution was shaken with HCl aq. (10%, 4 × 100 mL) in a
separatory funnel, washed with water (100 mL), and dried over
Na SO . The solvent was removed in vacuum, and the product was
Zn−16 (0.200 g, 0.2 mmol) was dissolved in CH Cl (200 mL),
2
2
and the solution was shaken with HCl aq. (20%, 2 × 100 mL) in a
separatory funnel, washed with water (100 mL), and dried over
Na SO . The solvent was removed in vacuum, and the product was
purified by column chromatography (silica gel, CH Cl /THF = 5:1)
and further by reprecipitation from CH Cl /THF (1:1) upon addition
2 2
2
4
purified by column chromatography (silica gel, CH Cl /THF = 70:1).
2
2
2
4
The title porphyrin 22 was precipitated from CH Cl /THF solution
2
2
2 2
upon addition of MeOH (∼1:100 v/v) and isolated as a green
crystalline powder (mp 286−288 °C). Yield 0.068 g (90%). UV−vis
of MeOH. The precipitate was isolated by centrifugation, washed with
MeOH, and dried in vacuum to give the title compound as a brown
crystalline powder (mp 287−288 °C). Yield 0.182 g (98%). UV−vis
1
(
(
THF) λ (nm): 422, 454, 521, 560, 594, 661. H NMR (CDCl ) δ
max
3
3
ppm): −0.72 (1H, broad), −0.25 (1H, broad), 0.83 (6H, t, J = 7.4
3
1
Hz, −CH ), 0.96 (6H, t, J = 7.4 Hz, −CH ), 1.31−1.43 (4H, m,
(DMA) λ (nm): 404, 499, 531, 568, 623. H NMR (CDCl ) δ
3
3
max
3
−
1
CH −), 1.44−1.55 (4H, m, −CH −), 1.65−1.76 (4H, m, −CH −),
(ppm) (mixture of conformers): −3.75 to −3.17 (2H, m, broad),
2
2
2
3
.76−1.86 (4H, m, −CH −), 4.41 (4H, t, J = 6.7 Hz, −OCH −), 4.47
0.90−1.04 (6H, m, −CH ), 1.42−1.53 (4H, m, −CH −), 1.74−1.85
2
2
3
2
3
3
(
4H, t, J = 6.7 Hz, −OCH −), 7.59 (2H, s), 7.67 (2H, dd, J = 7.4,
(4H, m, −CH −), 3.62−3.99 (4H, m, −CHH−), 3.76 (3H, s,
2
1
2
3
3
3
3
J = 7.0 Hz), 7.76 (2H, dd, J = 7.4, J = 6.9 Hz), 7.88 (2H, d, J =
−OCH ), 3.77 (3H, s, −OCH ), 3.80 (3H, s, −OCH ), 3.82 (3H, s,
2
1
2
3
3
3
3
3
8
.1 Hz), 8.44 (2H, d, J = 8.1 Hz), 8.66 (2H, d, J = 4.3 Hz, Pyr), 9.05
−OCH ), 4.07−4.28 (4H, m, −CHH−), 4.39−4.49 (4H, m,
3
J
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
3
−
OCH −), 4.50−4.65 (4H, m, −CH−), 8.89 (1H, d, J = 4.5 Hz,
Pd−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dibutoxycarbonylcyclohexeno)porphyrin (Pd−15). Method 2. Pd−
2
3
Pyr), 8.90 (1H, d, J = 4.5 Hz, Pyr), 9.06−9.12 (2H, m, Ar), 9.13−9.17
1H, m, Ar), 9.33 (1H, d, J = 4.5 Hz, Pyr), 9.34 (1H, d, J = 4.5 Hz,
Pyr), 9.64−9.79 (1H, m, meso-H), 10.05 (2H, s, meso-H). C NMR
CDCl ) δ (ppm) (mixture of conformers): 13.7, 13.8, 19.25, 19.27,
3.7, 23.9, 24.0, 30.7, 30.8, 40.87, 40.90, 41.05, 41.07, 52.19, 52.23,
5.6, 95.59, 95.63, 101.1, 101.2, 117.82, 117.83, 129.8, 130.1, 130.5,
30.8, 136.6, 136.7, 138.39, 138.42, 142.56, 142.59, 166.1, 166.2,
73.36, 173.38, 173.44. MALDI-TOF (m/z): calcd for C H N O
12
26.37, found 927.13 [M + H] , 965.07 [M + K] . HRMS (ESI-TOF)
m/z: [M + H] calcd for C H N O 927.38102, found 927.38357.
3
3
(
15 was synthesized from 15 (0.017 g, 0.0124 mmol) and Pd(OAc)
2
13
(0.011 g, 0.05 mmol). The reaction was complete in 40 min.
Chromatography was performed using CH Cl /THF (50:1) to give
(
2
2
3
2
6
1
1
9
crude Pd−15 (0.018 g), which was used in the subsequent
aromatization reaction without further purification.
Pt−5-(3,5-Dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dimethoxycarbonylcyclohexeno)porphyrin (Pt−16). Method 2. Pt−
52
54
4
+
+
1
6 was synthesized from 16 (0.05 g, 0.054 mmol) and Pt(acac)
2
+
(0.085 g, 0.22 mmol). The reaction was complete in 40 min.
52
55
4
12
Chromatography was performed using a CH Cl /THF gradient from
Insertion of Pt and Pd into Porphyrins. Method 1 (Benzoic
2
2
85
Acid Melt Method, Used for Insertion of Pt). A free-base porphyrin,
platinum(II) acetylacetonate, and benzoic acid were mixed together
and heated to 130−140 °C under Ar. The reaction progress was
monitored by UV−vis spectroscopy; samples were analyzed every 15
min. The reaction was stopped after the Q00 band maximum of the
free-base porphyrin disappeared. The mixture was dispersed in
50:1 to 25:1. Pt−16 was isolated as an orange crystalline solid (mp
>300 °C). Yield: 0.060 g (100%). UV−vis (DMA) λmax (nm): 384,
1
500, 531. H NMR (CDCl
) δ (ppm) (mixture of conformers): 0.88−
3
1.00 (6H, m, −CH
), 1.42−1.54 (4H, m, −CH
−), 1.71−1.87 (4H, m,
), 3.75
3
2
−CH −), 2.99−3.52 (8H, m, −CHH−), 3.71 (3H, s, −OCH
2
3
(3H, s, −OCH ), 3.76 (3H, s, −OCH ), 3.79 (3H, s, −OCH ), 4.06−
3
3
3
3
MeOH/H O (∼2:1, 50 mL), and the precipitate, which contained
the target Pt porphyrin, was isolated by centrifugation. It was
redispersed in MeOH/H O (∼2:1, 20 mL) and centrifuged again. This
washing procedure was repeated three times, after which the final solid
was dried in vacuum. The product was purified by column
chromatography, and the fraction containing the target compound
was collected. The solvent was removed in vacuum, and the target
4.34 (4H, m, −CH−), 4.40−4.53 (4H, m, −OCH −), 8.78 (1H, d, J
2
2
3
= 4.8 Hz, Pyr), 8.79 (1H, d, J = 4.9 Hz, Pyr), 8.84−8.91 and 8.96−
9.00 (2H, m, Ar), 9.07−9.11 (1H, m, Ar), 9.12−9.20 (3H, m, Ar, Pyr),
9.21−9.29 and 9.48−9.63 (2H, m, meso-H), 9.71 (1H, s, broad, meso-
H). The 13C NMR spectrum was not recorded because of the low
solubility. MALDI-TOF (m/z): calcd for C H N O Pt 1119.32,
2
5
2
52
4
12
+
+
found 1119.73 [M] . HRMS (ESI-TOF) m/z: [M + H] calcd for
metalloporphyrin was reprecipitated from CH Cl2 by addition of
C H N O Pt 1120.33057, found 1120.33205.
2
52 53
4
12
MeOH. The precipitate was collected by centrifugation and dried in
Pd−5-(3,5-Dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dimethoxycarbonylcyclohexeno)porphyrin (Pd−16). Method 2.
Pd−16 was synthesized from 16 (0.015 g, 0.0162 mmol) and
vacuum.
8
6
Method 2 (Microwave-Assisted Method). A free-base porphyrin
was dissolved in dry benzonitrile (∼2−4 mL), and the solution was
placed into a thick-walled microwave vial (Biotage, 5 mL).
Platinum(II) acetylacetonate or palladium(II) acetate was added,
and the vessel was sealed, after which the mixture was subjected to
microwave irradiation at 250 °C (∼2 bar, 105−145 W) for 40 min
under stirring. The reaction progress was monitored by UV−vis
spectroscopy; samples were analyzed every 20 min. The reaction was
stopped after the Q00 band maximum of the free-base porphyrin
disappeared. After the mixture was cooled, benzonitrile was removed
in vacuum, and the product was purified by column chromatography
on silica gel. The fraction containing the target compound was
collected, and the solvent was removed in vacuum. The target
metalloporphyrin was reprecipitated from CH Cl upon addition of
Pd(OAc)
(0.0145 g, 0.065 mmol). The reaction was complete in 40
Cl /THF (25:1) to
2
min. Chromatography was performed using CH
2
2
give crude Pd−16 (0.0165 g), which was used in the aromatization
step without further purification (see below).
Pt−5-Phenyl-15-(p-methoxycarbonylphenyl)-syn-dibenzopor-
phyrin (Pt−18). Method 1. Pt−18 was synthesized from 18 (0.015 g,
0.026 mmol) and Pt(acac) (0.041 g, 0.1 mmol) in benzoic acid (1.5
2
g). The reaction was complete in 2 h. Chromatography was performed
using CH Cl . The target compound was isolated as a pink crystalline
powder (mp >300 °C). Yield: 0.008 g (38%). UV−vis (DMA) λmax
2
2
/
1
nm (log ε): 401 (5.33), 519 (4.19), 556 (4.91). H NMR (CDCl
) δ
), 7.04 (2H, d, J = 8.3 Hz, −Bn−), 7.58
= 8.0, J = 7.8 Hz, −Bn−), 7.89−7.96 (4H, m, −Bn−,
2
3
3
(ppm): 4.13 (3H, s, −OCH
3
3
3
(2H, dd, J
Ph), 8.02−8.12 (3H, m, Ph), 8.26 (2H, d, J = 8.2 Hz, Ar), 8.46 (2H,
2
2
1
3
MeOH, and the precipitate was collected by centrifugation and dried
in vacuum.
3
3
3
d, J = 8.2 Hz, Ar), 8.82 (2H, d, J = 4.7 Hz, Pyr), 9.16 (2H, d, J = 4.7
3
13
Pt−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dibutoxycarbonylcyclohexeno)porphyrin (Pt−15). Method 1. Pt−15
Hz, Pyr), 9.25 (2H, d, J = 7.8 Hz, −Bn−), 10.39 (2H, s, meso-H).
C
NMR (CDCl ) δ (ppm): 52.5, 101.4, 114.5, 119.9, 122.1, 125.9, 127.2,
3
was synthesized from 15 (0.153 g, 0.108 mmol) and Pt(acac) (0.170
127.3, 128.2, 128.6, 129.37, 129.43, 129.8, 130.4, 130.5, 132.5, 133.8,
2
g, 0.433 mmol) in benzoic acid (3 g). The reaction was complete in 6
h. Chromatography was performed using CH Cl /THF (50:1). The
136.3, 137.5, 139.2, 139.4, 140.2, 141.5, 145.9, 167.3. MALDI-TOF
+
(m/z): calcd for C H N O Pt 813.17, found 813.41 [M] . HRMS
2
2
42 26
4
2
+
target compound was isolated as an orange solid (mp 157−160 °C).
(ESI-TOF) m/z: [M] calcd for C H N O Pt 813.17012, found
42 26 4 2
1
Yield: 0.07 g (42%). UV−vis (THF) λ (nm): 391, 503, 535. H
813.16860.
max
NMR (CDCl ) δ (ppm) (mixture of conformers): 0.59−1.01 (24H,
Pt−5,15-Bis(3,5-Dibutoxycarbonylphenyl)-syn-dibenzoporphyrin
3
m, −CH ), 1.04−1.19 and 1.34−1.86 (32H, m, −CH −), 2.87−3.12
(Pt−19). Method 1. Pt−19 was synthesized from 19 (0.12 g, 0.132
3
2
(
−
4
4H, m, −CHH−), 3.48−3.63 (4H, m, −CHH−), 3.86−4.02 (4H, m,
mmol) and Pt(acac) (0.21 g, 0.53 mmol) in benzoic acid (2.00 g, 16.4
2
3
OCH −), 4.17−4.59 (16H, m, −OCH −, −CH−), 8.79 (2H, d, J =
mmol). The reaction was complete in 6 h. Chromatography was
2
2
.9 Hz, Pyr), 8.90−8.94 (2H, m, Ar), 8.98−9.06 (2H, m, Ar), 9.12−
.16 (1H, m, Ar), 9.19−9.25 (3H, m, Ar, Pyr), 10.03−10.08 (2H, m,
performed using CH Cl /THF = 50:1. The target compound was
2
2
9
isolated as a dark-red crystalline powder (mp >300 °C). Yield: 0.08 g
(56%). UV−vis (DMA) λmax/nm (log ε): 402 (5.34), 521 (4.16), 559
13
meso-H). C NMR (CDCl ) δ (ppm) (mixture of conformers): 13.37,
3
1
3
1
1
3
6
1
1
1
3.44, 13.68, 13.70, 13.73, 13.76, 13.78, 18.76, 18.83, 19.15, 19.18,
9.20, 19.26, 19.31, 23.68, 23.71, 23.99, 28.82, 29.16, 29.69, 30.30,
0.36, 30.63, 30.65, 30.73, 40.36, 40.41, 41.86, 41.94, 64.6, 64.7, 64.9,
5.6, 65.7, 65.8, 104.0, 117.3, 177.4, 119.4, 129.8, 129.9, 130.3, 130.5,
30.6, 130.7, 131.2, 131.3, 136.6, 136.7, 137.0, 137.1, 137.2, 137.8,
38.3, 138.4, 138.6, 138.7, 139.1, 139.2, 139.4, 140.5, 141.70, 141.79,
(4.92). H NMR (CDCl
3
) δ (ppm): 0.87 (6H, t, J = 7.4 Hz, −CH
),
3
3
0.94 (6H, t, J = 7.4 Hz, −CH
), 1.35−1.51 (8H, m, −CH
−), 1.68−
−), 4.45 (4H,
−), 6.96 (2H, d, J = 8.0 Hz, −Bn−), 7.60 (2H,
3
2
3
1.83 (8H, m, −CH
−), 4.41 (4H, t, J = 6.7 Hz, −OCH
2
2
3
3
t, J = 6.7 Hz, −OCH
2
3
3
3
3
dd, J
= J
= 7.5 Hz, −Bn−), 7.96 (2H, dd, J = J = 7.2 Hz,
1 2
1
2
3
3
−Bn−), 8.78 (2H, d, J = 3.5 Hz, Pyr), 9.03 (2H, d, J = 1.6 Hz, Ar),
3
3
3
41.83, 165.5, 165.7, 166.0, 166.1, 172.5, 172.6, 173.1, 173.2. HRMS
9.07 (2H, d, J = 1.6 Hz, Ar), 9.15 (1H, dd, J = J = 1.6 Hz, Ar), 9.22
1 2
+
3
3
(
ESI-TOF) m/z: [M + H] calcd for C H N O Pt 1565.65650,
(2H, d, J = 3.6 Hz, Pyr), 9.31 (2H, d, J = 7.5 Hz, −Bn−), 9.44 (1H,
80
97
4
16
3
3
1
3
found 1565.65826.
dd, J = J = 1.6 Hz, Ar), 10.50 (2H, s, meso-H). C NMR (CDCl )
1 2 3
Method 2. Pt−15 was synthesized from 15 (0.065 g, 0.0475 mmol)
δ (ppm): 13.7, 13.8, 19.2, 19.3, 30.6, 30.8, 65.6, 65.8, 101.4, 114.5,
120.1, 120.5, 125.2, 127.4, 127.5, 128.7, 129.8, 130.1, 130.3, 131.7,
132.1, 136.1, 137.1, 137.1, 137.4, 137.7, 138.1, 139.1, 140.1, 141.7,
and Pt(acac) (0.056 g, 0.143 mmol). The reaction was complete in 40
2
min. Yield: 0.074 g (100%).
K
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1
1
42.4, 165.8, 166.1. MALDI-TOF (m/z): calcd for C H N O Pt
155.37, found 1155.01 [M] . HRMS (ESI-TOF) m/z: [M] calcd for
diluted with CH Cl (100 mL), washed with Na SO (10% aqueous
60
56
4
8
2
2
2
3
+
+
solution, 2 × 50 mL) and water (50 mL), and dried over Na SO . The
2 4
C H N O Pt 1155.37445, found 1155.37554.
solvents were removed in vacuum, and the product was purified by
column chromatography on silica gel. The fraction containing the
target compound was collected, and the solvent was removed in
vacuum. The target metalloporphyrin was reprecipitated from CH Cl
60
56
4
8
Method 2. Pt−19 was synthesized from 19 (0.02 g, 0.021 mmol)
and Pt(acac) (0.024 g, 0.062 mmol) and purified as in method 1
above. Yield: 0.022 g (92%).
2
2
2
Pd−5,15-Bis(3,5-Dibutoxycarbonylphenyl)-syn-dibenzoporphyrin
upon addition of MeOH, and the precipitate was collected by
centrifugation and dried in vacuum.
(
Pd−19). Method 2. Pd−19 was synthesized from 19 (0.01 g, 0.01
mmol) and Pd(OAc) (0.0093 g, 0.042 mmol). Chromatography was
2
Pt−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dibutoxycarbonylbenzo)porphyrin (Pt−20). Pt−20 was synthesized
from Pt−15 (0.05 g, 0.033 mmol) using DDQ (0.03 g, 0.132 mmol).
The reaction was complete in 10 h. Chromatography was performed
using CH Cl /THF = 50:1. Pt−20 was isolated as a bright-purple
performed using CH Cl /THF = 50:1. Pd−19 was isolated as a dark-
2
2
purple crystalline solid (mp 296−297 °C). Yield: 0.011 g (100%).
1
UV−vis (DMA) λ
(nm): 417, 534, 570. H NMR (CDCl ) δ
max
3
3
3
(
−
4
ppm): 0.88 (6H, t, J = 7.4 Hz, −CH ), 0.95 (6H, t, J = 7.4 Hz,
3
2
2
CH ), 1.35−1.54 (8H, m, −CH −), 1.68−1.84 (8H, m, −CH −),
3
2
2
crystalline solid (mp 256−258 °C). Yield: 0.04 g (88%). UV−vis
3
3
1
.41 (4H, t, J = 6.8 Hz, −OCH −), 4.46 (4H, t, J = 6.7 Hz,
OCH −), 7.01 (2H, d, J = 8.1 Hz, −Bn−), 7.62 (2H, dd, J = 7.8,
2
(DMA) λ /nm (log ε): 412 (5.43), 527 (4.29), 568 (5.01). H NMR
max
3
3
3
3
−
2
1
(CDCl ) δ (ppm): 0.87 (6H, t, J = 7.4 Hz, −CH ), 0.95 (6H, t, J =
3
3
3
3 3
3
3
J = 7.4 Hz, −Bn−), 7.95 (2H, dd, J = J = 7.4 Hz, −Bn−), 8.76
2
1
2
7.4 Hz, −CH ), 1.05 (6H, t, J = 7.4 Hz, −CH ), 1.10 (6H, t, J = 7.4
3
3
3
3
3
(
2H, d, J = 4.6 Hz, Pyr), 9.03 (2H, d, J = 1.6 Hz, Ar), 9.07 (2H, d, J
Hz, −CH ), 1.34−1.62 (16H, m, −CH −), 1.69−1.92 (16H, m,
3
2
3
3
3
=
1.6 Hz, Ar), 9.13−9.19 (3H, m, Pyr, Ar), 9.29 (2H, d, J = 7.8 Hz,
−CH −), 4.35 (4H, t, J = 7.1 Hz, −OCH −), 4.42 (4H, t, J = 6.8 Hz,
2
2
3
3
3
3
−
Bn−), 9.44 (1H, dd, J = J = 1.6 Hz, Ar), 10.42 (2H, s, meso-H).
−OCH −), 4.46 (4H, t, J = 6.7 Hz, −OCH −), 4.54 (4H, t, J = 6.8
1
2
2
2
1
3
3
C NMR (CDCl ) δ (ppm): 13.69, 13.74, 19.2, 19.3, 30.6, 30.8, 65.6,
Hz, −OCH −), 7.55 (2H, s, −Bn−), 8.85 (2H, d, J = 4.9 Hz, Pyr),
3
2
3
3
6
1
1
5.8, 101.2, 114.6, 120.0, 120.3, 125.1, 127.3, 127.4, 129.4, 129.8,
30.2, 130.6, 131.7, 132.0, 136.9, 137.5, 137.7, 137.8, 138.6, 138.7,
39.4, 140.8, 142.1, 142.8, 165.8, 166.1. MALDI-TOF (m/z): calcd for
9.03 (2H, d, J = 1.6 Hz, Ar), 9.07 (2H, d, J = 1.6 Hz, Ar), 9.17 (1H,
3
3
3
dd, J = J = 1.6 Hz, Ar), 9.31 (2H, d, J = 4.9 Hz, Pyr), 9.46 (1H, dd,
J = J = 1.6 Hz, Ar), 9.61 (2H, s, −Bn−), 10.63 (2H, s, meso-H). C
NMR (CDCl ) δ (ppm): 13.66, 13.73, 13.79, 13.83, 19.16, 19.17,
1
2
3
3
13
1
2
+
C H N O Pd 1066.31, found 1065.90 [M] . HRMS (ESI-TOF) m/
z: [M] calcd for C H N O Pd 1066.31478, found 1066.31410.
60
56
4
8
3
+
60
56
4
8
19.26, 19.32, 30.63, 30.68, 30.73, 65.65, 65.68, 65.8, 66.1, 103.3, 116.0,
Pt−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-dinaphtho[2,3]-
1
1
1
20.8, 121.4, 126.9, 129.4, 130.1, 130.4, 130.6, 131.4, 132.2, 132.3,
porphyrin (Pt−22). Method 1. Pt−22 was synthesized from 22 (0.032
g, 0.03 mmol) and Pt(acac) (0.05 g, 0.12 mmol) in benzoic acid (2
g). The reaction was complete in 2 h. Chromatography was performed
using CH Cl . The target compound was isolated as a dark-green
32.7, 135.4, 136.7, 137.1, 137.5, 137.6, 139.1, 140.3, 140.9, 141.1+,
2
41.2, 165.2, 165.9, 166.7, 168.8. HRMS (ESI-TOF) m/z: [M + H]
calcd for C H N O Pt 1557.59389, found 1557.5965.
80
89
4
16
2
2
Pd−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dibutoxycarbonylbenzo)porphyrin (Pd−20). Pd-20 was prepared
from Pd−15 (0.018 g, 0.012 mmol) using DDQ (0.011 g, 0.049
mmol). The reaction was complete in 8 h. Chromatography was
performed using CH Cl /THF = 50:1. Pd−20 was isolated as a dark-
crystalline powder (mp >300 °C). Yield: 0.0075 g (20%). UV−vis
1
(
DMA) λ /nm (log ε): 423 (5.02), 549 (4.16), 593 (4.93). H NMR
max
3
3
(
7
CDCl ) δ (ppm): 0.81 (6H, t, J = 7.3 Hz, −CH ), 0.95 (6H, t, J =
3
3
.3 Hz, −CH ), 1.30−1.41 (4H, m, −CH −), 1.41−1.53 (4H, m,
3
2
2
2
−
4
−
7
CH −), 1.65−1.74 (4H, m, −CH −), 1.75−1.84 (4H, m, −CH −),
2
2
2
purple crystalline solid (mp 243−245 °C). Yield: 0.0165 g (92% over
3
3
.40 (4H, t, J = 6.7 Hz, −OCH −), 4.46 (4H, t, J = 6.7 Hz,
1
2
two steps based on 15). UV−vis (DMA) λ (nm): 427, 541, 581. H
max
OCH −), 7.35−7.43 (2H, m, broad), 7.60−7.67 (2H, m, broad),
3
2
NMR (CDCl ) δ (ppm): 0.88 (6H, t, J = 7.4 Hz, −CH ), 0.95 (6H, t,
3
3
.69−7.76 (2H, m, broad), 7.76−7.83 (2H, m, broad), 8.36−8.40 (2H,
3
3
3
J = 7.4 Hz, −CH ), 1.05 (6H, t, J = 7.4 Hz, −CH ), 1.10 (6H, t, J =
3
3
3
m, broad), 8.67 (2H, m, broad), 9.02 (2H, d, J = 1.5 Hz, Ar), 9.11
7
−
−
.4 Hz, −CH ), 1.35−1.62 (16H, m, −CH −), 1.70−1.92 (16H, m,
3
3
3
3
2
(
2H, m, broad), 9.15 (1H, dd, J = J = 1.6 Hz, Ar), 9.17 (2H, d, J =
3
3
1
2
CH −), 4.36 (4H, t, J = 7.1 Hz, −OCH −), 4.42 (4H, t, J = 6.8 Hz,
3
3
2
2
1.5 Hz, Ar), 9.63 (1H, dd, J = J = 1.5 Hz, Ar), 9.72 (2H, s, broad),
3
3
1
2
OCH −), 4.47 (4H, t, J = 6.7 Hz, −OCH −), 4.54 (4H, t, J = 6.8
13
2
2
1
0.46 (2H, s, broad, meso-H). The C NMR spectrum was not
3
Hz, −OCH −), 7.61 (2H, s, −Bn−), 8.86 (2H, d, J = 4.8 Hz, Pyr),
+
2
recorded because of the low solubility. HRMS (ESI-TOF) m/z: [M]
calcd for C H N O Pt 1256.40747, found 1256.40717.
3
3
9
.04 (2H, d, J = 1.5 Hz, Ar), 9.08 (2H, d, J = 1.5 Hz, Ar), 9.17 (1H,
68
60
4
8
3
3
3
dd, J = J = 1.6 Hz, Ar), 9.32 (2H, d, J = 4.8 Hz, Pyr), 9.46 (1H, dd,
1
2
Pd−5,15-Bis(3,5-dibutoxycarbonylphenyl)-syn-dinaphtho[2,3]-
3
3
13
J = J = 1.6 Hz, Ar), 9.66 (2H, s, −Bn−), 10.67 (2H, s, meso-H).
C
1
2
porphyrin (Pd−22). Method 2. Pd−22 was synthesized from 22
NMR (CDCl ) δ (ppm): 13.67, 13.74, 13.80, 13.84, 19.16, 19.18,
(
0.004 g, 0.0038 mmol) and Pd(OAc) (0.0034 g, 0.015 mmol). The
3
2
1
1
1
9.27, 19.32, 30.63, 30.69, 30.74, 65.65, 65.66, 65.8, 66.2, 102.7, 115.7,
20.7, 121.0, 126.9, 129.3, 130.0, 130.5, 130.9, 131.7, 132.09, 132.12,
32.4, 136.0, 136.7, 137.2, 137.3, 137.8, 137.9, 140.3, 141.50, 141.52,
reaction was completed in 40 min. Chromatography was performed
using CH Cl . Pd−22 was isolated as a dark-green crystalline powder
2
2
(
4
mp >300 °C). Yield: 0.0036 g (82%). UV−vis (DMA) λ (nm):
max
1
3
165.2, 166.0, 166.8, 168.8. MALDI-TOF (m/z): calcd for
35, 561, 605. H NMR (CDCl ) δ (ppm): 0.81 (6H, t, J = 7.4 Hz,
3
+
3
C H N O Pd 1466.52, found 1465.90 [M] . HRMS (ESI-TOF)
−
1
CH ), 0.95 (6H, t, J = 7.4 Hz, −CH ), 1.28−1.41 (4H, m, −CH −),
.41−1.54 (4H, m, −CH −), 1.64−1.74 (4H, m, −CH −), 1.74−1.84
80 88
4
16
3
3
2
+
m/z: [M + H] calcd for C H N O Pd 1467.53279, found
80 89
4
16
2
2
3
3
1
467.53562.
(
=
4H, m, −CH −), 4.40 (4H, t, J = 6.5 Hz, −OCH −), 4.46 (4H, t, J
2
2
Pt−5-(3,5-Dibutoxycarbonylphenyl)-syn-bis(4′,5′-
6.6 Hz, −OCH −), 7.42−7.49 (2H, m, broad), 7.60−7.69 (2H, m,
2
dimethoxycarbonylbenzo)porphyrin (Pt−21). Pt−21 was synthe-
sized from Pt−16 (0.04 g, 0.036 mmol) using DDQ (0.032 g, 0.143
mmol). The reaction was complete in 12 h. Chromatography was
broad), 7.70−7.78 (2H, m, broad), 7.80−7.87 (2H, m, broad), 8.38−
.47 (2H, m, broad), 8.66−8.74 (2H, m, broad), 9.00−9.05 (2H, m,
broad), 9.10−9.20 (5H, m, broad), 9.60−9.66 (1H, m, broad), 9.73−
8
13
performed using CH Cl /THF = 5:1. Pt−21 was isolated as a pink
9
.82 (2H, m, broad), 10.46−10.53 (2H, m, broad). The C NMR
2
2
crystalline powder (mp >300 °C). Yield: 0.032 g (81%). UV−vis
spectrum was not recorded because of the low solubility. MALDI-TOF
1
+
(
(
1
−
DMA) λ
(nm): 405 (5.40), 522 (4.27), 562 (5.03). H NMR
(
(
1
m/z): calcd for C H N O Pd 1166.34, found 1165.88 [M] . HRMS
ESI-TOF) m/z: [M] calcd for C H N O Pd 1166.34628, found
166.34671.
max
68
60
4
8
3
+
DMSO-d , 80 °C) δ (ppm): 0.99 (6H, t, J = 7.3 Hz, −CH ), 1.49−
6
3
68
60
4
8
.61 (4H, m, −CH −), 1.79−1.90 (4H, m, −CH −), 4.20 (6H, s,
2
2
3
OCH ), 4.21 (6H, s, −OCH ), 4.51 (4H, t, J = 6.5 Hz, −OCH −),
Aromatization of Dicyclohexenoporphyrins M−15 and M−
3
3
2
1
6 into DBPs M−20 and M−21 (M = Pd, Pt). The porphyrin was
7.91−8.03 (2H, m, broad), 8.09−8.27 (2H, m, broad), 8.65−8.99
(10H, m, broad). The 13C NMR spectrum was not recorded because
of the low solubility. MALDI-TOF (m/z): calcd for C H N O Pt
dissolved in toluene (∼50 mL), and DDQ was added. The reaction
mixture was refluxed, and the reaction progress was monitored by
UV−vis spectroscopy. The reaction was stopped when no further
changes could be observed in the spectra. The reaction mixture was
5
2
44
4
12
+
+
1111.26, found 1111.72 [M] . HRMS (ESI-TOF) m/z: [M] calcd for
C H N O Pt 1111.26014, found 1111.26239.
52
44
4
12
L
dx.doi.org/10.1021/jo501521x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Pd−5-(3,5-Dibutoxycarbonylphenyl)-syn-bis(4′,5′-
dimethoxycarbonylbenzo)porphyrin (Pd−21). Pd−21 was synthe-
sized from Pd−16 (0.0165 g, 0.016 mmol) using DDQ (0.0145 g,
(11) Shea, P. B.; Kanicki, J.; Ono, N. J. Appl. Phys. 2005, 98,
No. 014503.
(12) Shea, P. B.; Pattison, L. R.; Kawano, M.; Chen, C.; Chen, J. H.;
Petroff, P.; Martin, D. C.; Yamada, H.; Ono, N.; Kanicki, J. Synth. Met.
2007, 157, 190.
0
.064 mmol). The target porphyrin was purified by column
chromatography (silica gel, CH Cl /THF = 5:1) and then by
2
2
reprecipitation from THF upon addition of MeOH. Pd−21 was
isolated as a dark-purple crystalline powder (mp >300 °C). Yield:
(13) Shea, P. B.; Yamada, H.; Ono, N.; Kanicki, J. Thin Solid Films
2
012, 520, 4031.
0
.013 g (79% over two steps based on 16). UV−vis (DMA) λ
max
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1
(
nm): 421, 534, 574. H NMR (DMSO-d , 80 °C) δ (ppm): 1.00 (6H,
6
3
t, J = 7.3 Hz, −CH ), 1.50−1.61 (4H, m, −CH −), 1.80−1.89 (4H,
3
2
3
m, −CH −), 4.12−4.22 (12H, m, −OCH ), 4.50 (4H, t, J = 6.5 Hz,
2
3
S.; Aleshchenkov, S.; Nelles, G.; Cheprakov, A.; Yasuda, A.; Mullen,
̈
−
8
OCH −), 7.62−7.72 (2H, m, broad), 7.73−7.86 (2H, m, broad),
2
K.; Wegner, G. Angew. Chem., Int. Ed. 2007, 46, 7693.
.00−8.26 (3H, m, broad), 8.29−8.50 (4H, m, broad), 8.50−8.59 (2H,
(16) Baluschev, S.; Yakutkin, V.; Wegner, G.; Miteva, T.; Nelles, G.;
m, broad), 8.85−8.92 (1H, m, broad). MALDI-TOF (m/z): calcd for
C H N O Pd 1022.20, found 1021.71 [M] . HRMS (ESI-TOF) m/
z: [M] calcd for C H N O Pd 1022.20031, found 1022.20218.
Yasuda, A.; Chernov, S.; Aleshchenkov, S.; Cheprakov, A. Appl. Phys.
Lett. 2007, 90, No. 181103.
+
52
44
4
12
+
52
44
4
12
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G.; Cheprakov, A.; Baluschev, S. Chem.Eur. J. 2008, 14, 9846.
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ASSOCIATED CONTENT
Supporting Information
Additional experimental details; NMR, MALDI-TOF, and
optical data; and X-ray crystallographic data for compound
Pt−19 (CIF). This material is available free of charge via the
Internet at http://pubs.acs.org.
■
*
S
(
19) Deng, F.; Sommer, J. R.; Myahkostupov, M.; Schanze, K. S.;
Castellano, F. N. Chem. Commun. 2013, 49, 7406.
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31, 144.
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(
2
(
Photobiol., A 1994, 77, 23.
AUTHOR INFORMATION
Corresponding Author
E-mail: vinograd@mail.med.upenn.edu.
■
(22) Gottumukkala, V.; Ongayi, O.; Baker, D. G.; Lomax, L. G.;
Vicente, M. G. H. Bioorg. Med. Chem. 2006, 14, 1871.
(23) Menard, F.; Sol, V.; Ringot, C.; Granet, R.; Alves, S.; Le Morvan,
C.; Queneau, Y.; Ono, N.; Krausz, P. Bioorg. Med. Chem. 2009, 17,
*
Notes
7
(
1
647.
24) Vinogradov, S. A.; Wilson, D. F. J. Chem. Soc., Perkin Trans. 2
995, 103.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(25) Lebedev, A. Y.; Cheprakov, A. V.; Sakadzic, S.; Boas, D. A.;
Wilson, D. F.; Vinogradov, S. A. ACS Appl. Mater. Interfaces 2009, 1,
Support from the Penn Medicine Neuroscience Center and the
National Institutes of Health (Grant R01-GM103591) is
gratefully acknowledged. The authors are grateful to Dr.
Patrick Carroll (Department of Chemistry, University of
Pennsylvania) for the X-ray structure determination and Dr.
Leland Maine (Department of Biochemistry and Biophysics,
University of Pennsylvania) for assistance with HRMS
measurements.
1
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