Naphthiporphyrins

ARTICLE

pubs.acs.org/joc

Naphthiporphyrins^†

Timothy D. Lash,* Alexandra M. Young, Jane M. Rasmussen, and Gregory M. Ferrence

Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, United States

S Supporting Information

b

ABSTRACT: Benziporphyrins, cross-conjugated porphyrin

analogues with a benzene ring in place of one of the usual

pyrrole units, have varying degrees of macrocyclic aromati-

city because the 6π electron arene needs to give up its

aromatic characteristics to facilitate conjugation over the

entire system. As naphthalene would lose less resonance

stabilization energy in giving up one of its benzene units, it

was proposed that naphthiporphyrins would exhibit enhanced diatropicity compared to the related benziporphyrins. A

naphthiporphyrin was prepared using the “3 þ 1” variant of the MacDonald condensation by reacting 1,3-naphthalenedi-

carbaldehyde with a tripyrrane in the presence of TFA, followed by oxidation with DDQ. Although the free base form of

naphthiporphyrin showed no overall diatropicity, the corresponding dication in TFA-CDCl₃demonstrated a signiﬁcant

diatropic ring current where the internal CH shifted upﬁeld to between 4.0 and 4.6 ppm. Naphthiporphyrin was converted to

the corresponding palladium(II) complexes by reaction with Pd(OAc)₂in acetonitrile, and the complex was further

characterized by X-ray crystallography. Oxynaphthiporphyrins were similarly prepared by the “3 þ 1” methodology from

4-methoxy-1,3-naphthalene-dicarbaldehyde, and these showed slightly enhanced diatropic character compared to oxybenzi-

porphyrins. Reaction of oxybenziporphyrins or oxynaphthiporphyrins with silver(I) acetate aﬀorded the corresponding

silver(III) organometallic derivatives. A meso-tetraphenyl naphthiporphyrin was also synthesized in 4% yield by reacting a 1,4-

naphthalene dicarbinol with 2 equiv of benzaldehyde and 3 equiv of pyrrole in the presence of BF₃.Et₂O, followed by oxidation

with DDQ. However, this 1,4-naphthiporphyrin showed reduced diatropic character compared to the corresponding p-

benziporphyrin system. The NMR spectra for the 1,4-naphthiporphyrin show that the naphthalene unit pivots over the

macrocycle and this presumably leads to further steric interactions that reduce the planarity of the macrocycle. These results

demonstrate that while naphthiporphyrins can show enhanced aromatic properties as predicted, other factors may overwhelm

this eﬀect.

’ INTRODUCTION

macrocyclic delocalization, and 4 shows its internal CH

resonance at a typical benzene chemical shift of 7.9 ppm.¹¹

The meso-protons gave two 2H resonances at 6.57 (11,

16-CH) and 7.27 ppm (6,21-CH), values that are consider-

ably upﬁeld compared to those given by 1-3 and that are

consistent with a nonaromatic porphyrinoid.¹¹Benzipor-

phyrins would have to give up the favorable 6π-electron

arene aromaticity of the benzene unit to gain an

[18]annulene type conjugation pathway, and dipolar canoni-

cal forms like 6 would not be expected to contribute sig-

niﬁcantly to the properties of this system. However, addition

of TFA to NMR solutions of benziporphyrin 4 aﬀorded a

dication 4H₂^2þwhich showed an upﬁeld shift to the interior

CH to 5 ppm, while the external meso-protons shifted down-

ﬁeld by approximately 1 ppm.¹¹This result suggests that the

dication has a small diamagnetic ring current, presumably

due to resonance contributors like 7 which aid in charge

delocalization. Tetraarylbenziporphyrins 8 have also been

synthesized,^14ꢀ18and these too exhibit small diagmagnetic

Carbaporphyrinoid systems, where one of the usual pyrrole

units in the porphyrin macrocycle has been replaced with a

carbocyclic ring, show diverse spectroscopic properties and

chemical reactivity.^1ꢀ5While some carbaporphyrins (e.g., 1

and 2) show strong diatropic ring currents,^6,7azuliporphyrins

3 have much reduced aromatic properties⁸and benziporphyr-

ins 4 exhibit virtually no macrocyclic aromaticity.^9ꢀ11In

benzocarbaporphyrins 1⁶and tropiporphyrins 2,⁷the macro-

cycles possess 18π electron delocalization pathways that

are analogous to those found in true porphyrins, and this

provides an explanation for their porphyrin-like aromatic

properties.^12,13Azuliporphyrins, on the other hand, are

cross-conjugated and this interrupts any potential aromatic

delocalization pathway.⁸Nevertheless, the internal CH in

azuliporphyrins shows up near 3 ppm in their proton NMR

spectra, and this result demonstrates that a signiﬁcant albeit

weakened ring current is present in this system as well.⁸This

observation can be rationalized with dipolar resonance con-

tributors (e.g., 5) that possess both an 18π electron deloca-

lization pathway as well as tropylium character.⁸However,

cross-conjugation in benziporphyrins appears to prevent any

Received: March 23, 2011

Published: May 23, 2011

r

2011 American Chemical Society

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ring currents for the protonated species that are enhanced

when an electron-donating tert-butyl moiety is attached to the

benzene subunit.¹⁸Dimethoxybenziporphyrins 9 have also

been reported, and these show some diatropic character even

for the free base forms and substantially increased diatropicity

for the corresponding dications.^16,17,19These improved aro-

matic characteristics have been attributed to the inﬂuence of

the electron-donating methoxy substituents which stabilize

resonance contributors with 18π electron delocalization

pathways (e.g., 10).¹⁹

properties of naphthiporphyrins and their metallo-derivatives, are

presented below.

Benziporphyrins not only provide insights into porphyri-

noid aromaticity but they also exhibit interesting and unusual

reactivity, undergoing regioselective oxidation reactions^15,17,20

and readily forming organometallic derivatives.^14ꢀ18,21Given

the signiﬁcance of these porphyrin analogues, we wanted to

extend these studies to the synthesis of naphthiporphyrins

(e.g., 11) where a naphthalene moiety is introduced in place of

a benzene unit. As the resonance stabilization of an individual

benzene ring within the naphthalene framework is far less than

that for benzene itself,²²it was anticipated that naphthipor-

phyrins could take on increased diatropic characteristics. In

essence, we postulated that the penalty for losing 6π electron

arene aromaticity in canonical forms such as 12 (Scheme 1)

should be somewhat reduced and that this should result in

increased diatropic character in naphthiporphyrins compared

to benziporphyrins. To test this hypothesis, syntheses of

naphthalene-containing porphyrinoids were developed.²³The

results from these investigations, together with the spectroscopic

’ RESULTS AND DISCUSSION

Synthesis, Metalation, and Spectroscopic Properties of a

Naphthiporphyrin. Benziporphyrin had previously been

synthesized by reacting tripyrrane 13a^24,25with isophthalalde-

hyde in the presence of TFA in dichloromethane, followed by

neutralization with triethylamine and oxidation with DDQ.¹¹In

this work, improved results were obtained when the oxidation

was carried out without first neutralizing the solution and

benziporphyrin 4 was isolated in 29% yield (Scheme 1). Simi-

larly, 1,3-naphthalenedicarbaldehyde²⁶reacted with tripyrrane

13a under these conditions to give naphthiporphyrin 11 in 24%

yield (Scheme 1). Much poorer results were obtained if the

solution was neutralized with triethylamine prior to oxidation

and the product was contaminated with an aromatic oxidation

product oxynaphthiporphyrin (see later). Naphthiporphyrin was

isolated as a stable dark-green-colored compound but showed no

significant aromatic character. The UVꢀvis spectrum of naphthi-

porphyrin 11 showed two moderately strong bands at 329 and

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Scheme 1

Figure 1. UVꢀvis spectra of benziporphyrin 4 (red line) and naphthi-

porphyrin 11 (blue line) in chloroform.

Figure 2. Partial 500 MHz proton NMR spectrum of naphthiporphyrin

11 in CDCl₃showing details of the aromatic region.

Table 1. Selected Proton NMR Data (ppm) for Benzipor-

phyrin 4, Naphthiporphyrin 11, and the Related Diprotonated

Dications

6-CH 11-CH

16-CH 21-CH 22-CH 8-Me 19-Me

410 nm and weaker poorly defined absorptions that extended

beyond 800 nm (Figure 1). The spectrum was bathochromically

shifted but otherwise similar to the UVꢀvis spectrum for benzi-

porphyrin, which shows two peaks at 316 and 383 nm and smaller

broad absorptions in the visible region (Figure 1). The proton NMR

spectrum for 11 in CDCl₃also gave no indication of a macrocyclic

ring current (Figure 2). Aromatic character could have resulted from

contributions from dipolar canonical forms such as 12 (Scheme 1)

or from the existence of a tautomeric species 14 that has an 18π-

electron delocalization pathway. However, neither of these options

appears to be viable for naphthiporphyrin. The meso-protons at

positions 11 and 16, which are furthest removed from the naphtha-

lene unit, gave rise to two 1H singlets at 6.54 and 6.56 ppm, while

benziporphyrin gives a 2H resonance for these protons at 6.57 ppm

(Figure 2, Table 1). The meso-protons in fully aromatic porphyr-

inoids show up near 10 ppm, and the observed values clearly fall into

the nonaromatic region. The meso-protons at positions 6 and 21

gave 1H singlets at 7.37 and 8.21 ppm, respectively, but these are

affected by their proximity to the naphthalene unit. The correspond-

ing protons in benziporphyrin resonate at 7.27 ppm (Table 1). The

internal CH for 11 shows up at 8.08 ppm, compared to a value of

7.90 ppm for 4, and again shows no sign of the upfield shift expected

in an aromatic system. The resonances for the methyl substituents

may also be used as a guide as these peaks are commonly observed

downfield at 3.6 ppm for porphyrins. The values of 2.45 and

4

7.27

7.37 6.54/6.56 6.54/6.56 8.21

8.15 7.15 7.15 8.15

8.29 7.17/7.20 7.17/7.20 8.81

6.57

7.27

7.90

8.08

4.97

4.50

2.43

8.45

2.70

2.73

2.43

2.54

2.70

2.77

11

4H₂

2þ

11H₂

2.54 ppm for 11, and 2.43 ppm observed for 4, are again consistent

with structures that have no overall aromatic character (Table 1).

The identity of 11 was further confirmed by Hꢀ H COSY,

HSQC, NOE difference ¹H NMR and carbon-13 NMR spectros-

copy, and mass spectrometry.

1

Addition of TFA to solutions of benziporphyrin or naphthi-

porphyrin shows the initial formation of a monoprotonated

species using UVꢀvis spectroscopy, followed by the formation

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Figure 3. Partial 500 MHz proton NMR spectrum of benziporphyrin

4 in TFA-CDCl₃. The internal CH shows up near 5 ppm.

of a diprotonated dication (see Supporting Information). The

monocation for naphthiporphyrin (11H^þ) shows a strong broad

band at 708 nm, but this disappears in the presence of higher

2þ

quantities of TFA. The dication 11H₂in 10% TFA-CHCl₃

gave two weak Soret-like bands at 330 and 400 nm and minor

bands at 571 and 617 nm. The proton NMR spectrum of 11H₂

Figure 4. Partial 500 MHz proton NMR spectrum of naphthiporphyrin

11 in TFA-CDCl₃. In this case the internal CH is apparent at 4.5 ppm.

2þ

in TFA-CDCl₃showed the presence of a signiﬁcant diatropic

ring current, although this is also observed for the benziporphyr-

in dication 4H₂^2þ. The proton NMR spectrum of 4 in TFA-

CDCl₃(Figure 3) shows the meso-protons downﬁeld at 7.15 and

8.15 ppm, while the internal CH shifts upﬁeld to approximately

5 ppm. The latter resonance is somewhat sensitive to the

concentration of 4 and the quantity of TFA, but consistently fell

into a range of 4.9ꢀ5.5 ppm. The data are clearly consistent with

the presence of a weak diatropic ring current, although the

positive charges on the macrocycle presumably contribute to

the downﬁeld shifts for the external protons. The latter factor

should be less signiﬁcant for the methyl substituents, but the 6H

singlet corresponding to the two equivalent methyls is still shifted

downﬁeld to 2.70 ppm (Table 1). The proton NMR spectrum for

Scheme 2

2þ

the diprotonated naphthiporphyrin dication 11H₂in TFA-

CDCl₃shows many of the same trends (Figure 4). The meso-

protons are observed at 7.17, 7.20, 8.29, and 8.81 ppm, values

that are substantially downﬁeld shifted compared to the free base,

and the methyl substituents give rise to two 3H singlets at 2.73

and 2.77 ppm. The meso-protons furthest removed from the

naphthalene unit (11,16-CH) are only slightly further downﬁeld

than the values seen for 4H₂^2þ, as is also the case for the methyl

resonances, but the data are consistent with a slightly increased

diatropic character in 11H₂^2þ. Support for this interpretation

comes from the resonance for the internal CH. As was the case

for benziporphyrin, this resonance varied somewhat with con-

centration and quantity of TFA added, but nevertheless fell into

the range of 4.0ꢀ4.6 ppm. Not only is the resonance for the

22-CH shifted upﬁeld, but it is also consistently upﬁeld from the

values observed for 4H₂^2þ. Three NH resonances were also

noted at 6.6, 8.7, and 9.2 ppm. Overall, our results support our

conjecture that naphthalene units would enhance the diatropic

properties of borderline aromatic benziporphyrin systems.

Although tetraarylbenziporphyrins have been shown to form

metallo-derivatives previously,^14ꢀ18no examples of metalated

species have been reported for meso-unsubstituted benzipor-

phyrins. Benziporphyrin 4 was reacted with nickel(II) acetate in

reﬂuxing DMF for 30 min and the corresponding nickel(II)

organometallic derivative 15a was generated in 42% yield

(Scheme 2). The corresponding palladium(II) complex 15b

was also formed by reacting 4 with palladium(II) acetate in

reﬂuxing acetonitrile. The UVꢀvis spectrum for the nickel

complex showed two weak Soret-like bands at 343 and

408 nm, and a broad absorption centered on 652 nm. In

contrast, the palladium complex gave a stronger Soret band at

406 nm, and a series of small absorptions between 450 and

800 nm. The proton NMR spectrum of 15a gave resonances for

the meso-protons at 7.16 and 7.48 ppm, while the methyl

substituents gave a 6H singlet at 2.45 ppm. These values are

all shifted downﬁeld compared to the free base benziporphyrin,

and suggest that the metalated derivative has a small diatropic

ring current. The palladium complex gives two 2H resonances

for the meso-protons at 7.35 and 7.72 ppm and a 6H singlet for

the methyl groups at 2.63 ppm, indicating that the diatropicity

of 15b is enhanced compared to the nickel complex. This is

consistent with results for other nickel(II) and palladium(II)

carbaporphyrinoid complexes^21band is attributable to the

palladium complex taking on a more planar conformation

compared to 4 where the macrocycle is likely to be distorted

or ruﬄed to accommodate the smaller nickel cation. Attempts

to prepare the nickel(II) complex of naphthiporphyrin were

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Scheme 3

Figure 5. Color ORTEP III drawing (50% probability level, hydrogens

drawn arbitrarily small) of palladium(II) naphthiporphyrin 16.

unsuccessful, but 11 reacted with palladium(II) acetate in

reﬂuxing acetonitrile to give the palladium derivative 16 in

37% yield (Scheme 2). In this case, the meso-protons were

observed at 7.27, 7.39, 7.64, and 8.50 ppm while the methyl

groups gave two 3H singlets at 2.58 and 2.72 ppm. Taking into

account the eﬀect of the naphthalene moiety on the nearby

meso-protons, these data suggest that the naphthiporphyrin

complex has similar diatropic character to the benziporphyrin

derivative.

The X-ray crystal structure of palladium complex 16 has also

been obtained (Figure 5), and this not only conﬁrms the presence

ofa naphthalenemoiety but alsodemonstrates that the macrocycle

is a little saddled as evidenced by the 0.180 Å rms distance the

framework atoms lie from the plane deﬁned by Pd, C(22), N(23),

N(24), and N(25). The largest deviations from the plane are

C(21) (0.325(4) Å), C(6) (ꢀ0.320(4) Å), C(2) (0.303(4) Å),

and C(19) (0.280(4) Å). Of the 25 framework atoms, 13 deviate

more than 0.15 Å from this plane. The structure exhibits frame-

work bond distances consistent with a generally localized π-

bonding model. The metal coordination environment of 16 is

essentially the typical 4-coordinate square planar geometry char-

acteristic of Pd(II) complexes. This is similar to related and quite

planar palladium(II) N-confused porphyrins^27ꢀ29and a related

palladium(II) pyrazoloporphyrin,^21dwith no particular signiﬁ-

cance being attributed to the small observed deviation from

planarity in 16. The 2.055(4) Å PdꢀC distance of 16 is longer

than the 1.946(5) Å distance observed in the previously char-

acterized palladium(II) pyrazoloporphyrin^21dbut is still consistent

with the 2.00(5) Å distances observed for nearly 3000 crystal-

lographically measured complexes containing PdꢀC(phenyl)

σ-bonds.³⁰

tripyrrane 13b to give the diphenyloxybenziporphyrin 17b

(Scheme 3). Oxybenziporphyrins give porphyrin-like UVꢀvis

spectra with a strong Soret band near 430 nm and a series of

Q bands extending to >700 nm. The NMR spectra of oxybenzi-

porphyrins confirm that these carbaporphyrinoids are highly

diatropic in nature, showing the internal CH upfield near

ꢀ7 ppm, while the meso-protons are shifted downfield to give

resonances between 8.8 and 10.3 ppm. Unlike benziporphyrins,

addition of TFA to solutions of oxybenziporphyrins leads to a

decrease in the aromatic properties for the system.¹¹In the

presence of trace amounts of TFA, a monocation 17H^þis

formed, but further addition of TFA leads to the formation of a

dicationic species 17H₂^2þ. The second protonation takes place on

the carbonyl unit, but this leads to a species with substantial

phenolic character (resonance contributor 19) that interrupts the

18π electron delocalization pathway.¹¹The loss of aromatic

character is particularly evident in the proton NMR spectra where

the internal CH shifts from ꢀ7 ppm to þ1 ppm upon addition of

TFA. Given the beneficial effect of a naphthalene unit on the

aromatic properties of naphthiporphyrin dication 11H₂^2þ, we

were interested to see how the properties of naphthalene analo-

gues of oxybenziporphyrins would be effected.³⁴To pursue this

study, an R-naphthol dialdehyde 20 was required (Scheme 4).

1-Methoxynaphthalene was reacted with 2 equiv of bromine in

acetic acid to give the corresponding 2,4-dibromo derivative 21

in 94% yield. Metalation at room temperature with excess

n-butyllithium, followed by the addition of DMF and hydrolysis

Synthesis, Metalation, and Spectroscopic Properties of

Oxynaphthiporphyrins. Some time ago, we reported that

4-hydroxy-1,3-benzenedicarbaldehyde reacted with tripyrrane

13a using the “3 þ 1” variant of the MacDonald condensation³¹

to give an aromatic porphyrinoid 17a (Scheme 3).¹⁰Although

this reaction could have given the hydroxybenziporphyrin 18a,

this species tautomerizes to produce oxybenziporphyrin

17a.^{10,11,19,32,33}The reaction has also been carried out with

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Scheme 4

Scheme 5

with hydrochloric acid gave the corresponding dialdehyde 22.

Treatment with boron tribromide in dichloromethane at room

temperature then gave the required dialdehyde 20. Naphthol

dialdehyde 20 was reacted with tripyrrane 13a in the presence of

TFA to give, following neutralization with triethylamine and

oxidation with DDQ, oxynaphthiporphyrin 23a in approximately

20% yield. Surprisingly, reaction of 4-methoxy-1,3-naphthalene-

dicarbaldehyde (22) with tripyrrane 13a under the same condi-

tions gave superior results aﬀording the oxynaphthiporphyrin in

35% yield. The methyl ether appears to undergo spontaneous

cleavage under the reaction conditions and no methoxynaphthi-

porphyrin could be isolated. This stands in contrast with earlier

studies, where dimethoxybenzene dialdehydes reacted with

tripyrrane 13a using the same “3 þ 1” methodology to give

dimethoxybenziporphyrins with no cleavage of the methyl ethers

occurring under these mild conditions.¹⁹Although this result was

unexpected, the use of the methoxy derivative 22 is convenient as

it cuts out one step in the synthesis. Dialdehyde 22 also reacted

with tripyrrane 13b to give the related diphenyloxynaphthipor-

phyrin 23b in comparable yields (Scheme 5). Again, hydroxy-

naphthiporphyrins 24 might arise in this chemistry but this

species apparently strongly favors the aromatic seminaphthoqui-

none tautomers. The formation of this tautomer is conﬁrmed by

the presence of an absorption for CdO stretching at 1630 cm^ꢀ1

and the presence of a CdO resonance in the carbon-13 NMR

spectra near 190 ppm.

oxybenziporphyrins. These eﬀects are easily monitored using

UVꢀvis spectroscopy. Figure 6 shows the formation of mono-

cation 17aH^þby adding small increments of TFA to a cuvette

containing a solution of oxybenziporphyrin 17a in chloroform.

The Soret band and the secondary peak shift to slightly higher

wavelength (427 and 467 nm) and the Q bands show signiﬁcant

shifts as well. Addition of 20 equiv of TFA takes the ﬁrst

protonation to completion. Similar results were obtained with

oxynaphthiporphyrin 23a, where the Soret and the associated

secondary absorption shift to 431 and 460 nm, respectively

(Figure 7). Further protonation requires a large excess of TFA.

However, in 1% TFA-CHCl₃oxybenziporphyrin shows a greatly

reduced intensity of the Soret band, and in 5% TFA the

monocation 17aH^þhas been completely converted into a new

As is the case for oxybenziporphyrin,^10,11oxynaphthiporphyr-

in shows some shifts in its proton NMR spectra due to

concentration. Nevertheless, under comparable conditions, oxy-

naphthiporphyrin 23a shows slightly enhanced diatropic char-

acter compared to oxybenziporphyrin 17a. The internal CH was

observed at ꢀ7.4 ppm, while the meso-protons were shifted

downﬁeld to give resonances at 9.27, 9.33, 9.94, and 10.65 ppm.

The UVꢀvis spectrum of 23a was similar to 17a, showing a

strong Soret band at 429 nm and a secondary absorption at

447 nm, followed by a series of four Q bands between 500 and

700 nm. The related diphenyl compound gave similar spectro-

scopic results. Both oxynaphthiporphyrins were further charac-

2þ

species 17aH₂(Figure 8). The dication gives a weak Soret

band at 431 nm and Q bands at 552, 596, 693, and 764 nm.

Although similar changes were observed for oxynaphthiporphyr-

in 23a, 1% TFA only slightly reduced the intensity of the Soret

band and it was necessary to use a 50% TFA-chloroform solution

to fully form the new species 23aH₂^2þ(Figure 9). This gave a

weak split Soret band at 441 and 460 nm, and Q bands at 635,

689, and 760 nm. The presence of the naphthalene unit appears

to inhibit the second protonation rather than enhance the

aromatic characteristics of the dicationic species but the diﬀer-

ences between the two porphyrinoid systems are substantial.

Addition of one drop of TFA to a solution of 23a in CDCl₃gave a

1

terized by ¹Hꢀ H COSY, HSQC, NOE diﬀerence proton NMR

and carbon-13 NMR spectroscopy and mass spectrometry (see

Supporting Information).

Addition of TFA to solutions of oxynaphthiporphyrins 23 in

chloroform lead to reduced aromatic character, but far higher

quantities of acid were required to see the same eﬀects as for

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Figure 8. UVꢀvis spectra of oxybenziporphyrin 17a in chloroform with

Figure 6. UVꢀvis spectra of oxybenziporphyrin 17a in chloroform with

0 (red), 2 (orange), 5 (green), and 20 equiv (blue) of triﬂuoroacetic acid

showing the formation of monocation 17aH^þ.

20 equiv of TFA (monocation, red), and in 1% TFA-CHCl₃(orange),

2% TFA-chloroform (green), and 5% TFA-chloroform (blue) showing

2þ

the formation of dication 17aH₂

.

Figure 7. UVꢀvis spectra of oxynaphthiporphyrin 23a in chloroform

with 0 (red), 1 (orange), 2 (green), 5 (blue), and 10 equiv (purple) of

triﬂuoroacetic acid showing the formation of monocation 23aH^þ.

Figure 9. UVꢀvis spectra of oxynaphthiporphyrin 23a in chloroform

with 10 equiv of TFA (monocation, red), and in 1% TFA-CHCl₃

(orange), 10% TFA-chloroform (green), 20% TFA-chloroform (blue),

clean proton NMR spectrum of the monocation 23aH^þ. This

showed the internal CH at ꢀ5.69 ppm and three broad NH

resonances at ꢀ4.41, ꢀ1.42, and ꢀ0.98 ppm. The meso-protons

were shifted downﬁeld to 9.71, 9.78, 10.55, and 10.86 ppm. The

methyl groups gave two 3H singlets at 3.46 and 3.47 ppm. The

results indicate that the monocation has a similar diamagnetic

ring current to the free base form of oxynaphthiporphyrin.

Addition of further quantities of TFA to the NMR solution

resulted in small downﬁeld shifts to the internal protons,

indicating that dication 23aH₂^2þis present in equilibrium with

23aH^þ, but the results conﬁrm that the monocation predomi-

nates in solution at higher acid concentrations (see Supporting

Information). Similar spectroscopic data were obtained for the

diphenyl substituted porphyrinoids 17b and 23b.

There are three hydrogens present in the internal cavity of

oxybenziporphyrins and oxynaphthiporphyrins, and in principle

these porphyrinoids could act as trianionic ligands. However,

oxybenziporphyrin reacts with palladium(II) chloride in the

presence of potassium carbonate to form the palladium(II)

organometallic species 25 (Scheme 6).³⁵In this instance, the

system is acting as a dianionic ligand in much the same way as

benziporphyrins 4 (see previous section). Nevertheless, many

carbaporphyrinoid systems including benzocarbaporphyrins,

and 50% TFA-chloroform (purple) showing the formation of dication

2þ

23aH₂

.

tropiporphyrins and N-confused porphyrins form silver(III)

derivatives upon reaction with silver(I) salts.^7b,36,37Oxybenzi-

porphyrin 17a was reacted with silver acetate in chloro-

formꢀmethanol at room temperature and the silver(III)

complex 26a was isolated in 96% yield (Scheme 6). Diphenyl

oxybenziporphyrin reacted similarly to give the related complex

26b in 95% yield. Unfortunately, 26a and 26b were fairly

insoluble in organic solvents. Silver(III) complex 26a gave a

poor quality NMR spectra in CDCl₃, or a mixture of methanol-d₄

and CDCl₃, which showed the meso-protons in the downﬁeld

region and conﬁrmed the diatropic character of this species.

Improved spectroscopic data could be obtained for the diphenyl

substituted silver complex 26b, and in this case the proton NMR

spectrum for a dilute sample in CDCl₃showed the meso-protons

as four 1H singlets at 8.87, 9.69, 9.71, and 10.32 ppm, while the

methyl groups gave 3H singlets at 3.30 and 3.43 ppm. The

solubility of 26b was improved by adding some methanol-d₄to

the NMR solution, but it was only possible to obtain a low quality

carbon-13 NMR spectrum for this silver(III) complex. The

UVꢀvis spectrum of 26a showed a Soret band at 456 nm and

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Scheme 6

the rest of the porphyrinoid framework. This would increase the

interaction between the naphthalene 2¹-CH and the adjacent

meso-hydrogen causing the naphthalene moiety to twist out of

alignment. For the oxybenziporphyrins, the silver(III) cation

would draw the macrocycle into a planar arrangement, but this is

not possible for the oxynaphthiporphyrin series. Hence, other

factors need to be taken into account when assessing the

spectroscopic data. Similar arguments can be used to explain

why palladium(II) naphthiporphyrin 16 showed no increased

diatropicity compared to the benziporphyrin complex 15b (see

previous section).

Silver has two naturally occurring isotopes with natural

abundances of 51.82% (¹⁰⁷Ag) and 48.18% (¹⁰⁹Ag).³⁸The near

equal abundances of two isotopes diﬀering by two mass units

gives the mass spectra of silver complexes 26a, 26b, 27a and 27b

a superﬁcial resemblance to bromine compounds. In addition,

both isotopes have a spin I = ¹/₂.³⁸In most silver(III) carbapor-

phyrinoid complexes, it has not been possible to locate the

carbon connected to the silver cation.³⁷However, the silver(III)

complex of tetraphenyl N-confused porphyrin showed the

carbon as two overlapping doublets at 138.97 ppm with coupling

constants of 75.7 and 83.0 Hz.³⁶The gyromagnetic ratios for

¹⁰⁷Ag and ¹⁰⁹Ag are reported to be ꢀ1.0828 and ꢀ1.2448,

respectively.³⁸Therefore, the ratio of the J values should be 1.15.

The values reported by Furuta and co-workers give a slightly

lower ratio of 1.10.³⁶The best resolved carbon-13 NMR

spectrum for our silver complexes corresponded to the most

soluble derivative 27a. The carbon-13 NMR spectrum for this

silver(III) oxynaphthiporphyrin showed some signs of long-

range coupling but also gave two doublets at 163.2 ppm with

J values of 50.1 and 56.4 Hz (see Supporting Information). The

J values are smaller than the ones reported for the N-confused

porphyrin complex, but the ratio for the two values of 1.125 is

closer to the expected value.

Synthesis and Spectroscopic Properties of Tetraphenyl-

1,4-naphthiporphyrin. In 2002, Stepien and Latos-Grazynski

reported a low yielding synthesis of tetraaryl-p-benziporphyrins

28 (Scheme 7).³⁹This was accomplished by reacting dicarbinols

29 with 3 equiv of pyrrole and 2 equiv of benzaldehyde or

p-tolualdehyde in the presence of BF₃.Et₂O in dichloromethane,

followed by oxidation with DDQ, and the p-benziporphyrins

were isolated in 1% yield.³⁹The 1,4-connection to the benzene

ring cannot accommodate a completely planar porphyrinoid

structure and the p-phenylene unit is pivoted out of the mean

macrocyclic plane for the system by 44ꢀ48° (Scheme 8).³⁹The

benzene ring is too large to pass through the macrocyclic cavity,

but at room temperature the arene moiety undergoes a rapid

teeter-tottering or see-sawing motion between two equivalent

conformations A and B, where the environments of the two

CHdCH components interconvert (Scheme 8). In spite of the

nonplanar structure and conformational mobility of this system,

the proton NMR data showed the presence of a significant

diamagnetic ring current.³⁹The pyrrolic protons were shifted

downfield by approximately 1 ppm compared to the nonaromatic

tetraphenylbenziporphyrin 8, and gave resonances at 7.62, 7.74,

and 8.20 ppm.³⁹At 323 K, the four p-phenylene protons gave a

single resonance at 5.24 ppm corresponding to the average

environment for this teeter-tottering unit, but when the tem-

perature was lowered to 168 K two distinct 2H resonances were

observed at 7.68 and 2.32 ppm.³⁹The upfield shift of the “inner”

phenylene protons strongly supports the proposed diatropic

properties for this system, and the aromatic character was further

broadened Q bands between 550 and 650 nm. The IR spectrum

for 26a showed two strong peaks for the carbonyl group at 1619

and 1641 cm^ꢀ1, while 26b showed these two bands at 1618 and

1639 cm^ꢀ1. The origin of the peak splitting is not clear, and we

speculate that this is due to a Fermi resonance. Mass spectral data

were also obtained for these complexes.

Oxynaphthiporphyrin 23a and 23b also reacted smoothly with

silver(I) acetate to give the corresponding silver(III) complexes

27 in 68ꢀ87% yield (Scheme 6). These derivatives were far more

soluble in organic solvents and this allowed the silver complexes

1

to be characterized by ¹H NMR, ¹Hꢀ H COSY, HSQC, NOE

diﬀerence proton NMR and carbon-13 NMR spectroscopy, as

well as by IR and UVꢀvis spectroscopy and mass spectrometry.

The UVꢀvis spectrum for 27a in chloroform showed a strong

Soret band at 456 nm and broad Q bands between 500 and

620 nm. Diphenyl complex 27b gave a similar UVꢀvis spectrum

with a Soret band at 458 nm. Carbon-13 NMR spectra for 27a

and 27b showed resonances for the carbonyl moiety at 191.6 and

191.7 ppm, respectively. The proton NMR spectra for silver(III)

oxynaphthiporphyrins 27a and 27b demonstrated that the com-

plexes had retained highly diatropic characteristics. The data for

27b will be discussed so that it can be compared to the results for

oxybenziporphyrin complex 26b. The proton NMR spectrum for

27b showed the meso-protons as four 1H singlets at 9.29, 9.42,

9.52, and 9.85 ppm, while the methyl resonances appeared at 3.11

and 3.34 ppm. These values suggest that the diatropicity of the

oxynaphthiporphyrin complexes is slightly decreased compared

to the oxybenziporphyrin series. This is the opposite of our

expectations but could be explained due to steric factors. Silver-

(III) carbaporphyrins are known to be quite planar,^37aand this

factor would draw the naphthalene unit into the same plane as

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Scheme 7

Scheme 9

Scheme 10

Scheme 8

borohydride then gave the corresponding dicarbinol 37 as a

mixture of two diastereoisomers. The dialcohol was reacted with

3 equiv of pyrrole and 2 equiv of benzaldehyde in dichloro-

methane with a catalytic quantity of BF₃.Et₂O to generate a

naphthiporphyrinogen 38, and this was oxidized in situ with

DDQ to aﬀord tetraphenyl-1,4-naphthiporphyrin 33. The novel

porphyrinoid was isolated in approximately 4% yield as a dark

green solid and was easily separated from the tetraphenylpor-

phyrin byproduct by column chromatography on grade 2 basic

alumina.

The UVꢀvis spectrum of 33 in chloroform gave a moderately

strong band at 466 nm and a broad absorption at 632 nm

(Figure 10). Addition of 1 equiv of TFA gave rise to a new

spectrum with an intensiﬁed band at 488 nm and a broad

absorption centered on 757 nm, and this species was attributed

to the corresponding monocation 33H^þ. Further addition of

TFA resulted in the formation of a new species, assigned to the

dication 33H₂^2þ, and this showed a hypsochromically shifted

Soret band at 471 nm and a broad absorption at 731 nm. None of

these spectra resembled those for porphyrin-type systems, and

the Soret-like bands between 400 and 500 nm were weaker than

the one reported for p-benziporphyrin 28.³⁹The proton NMR

spectrum for 33 in CDCl₃was particularly revealing, and against

our expectations showed that the diatropicity was decreased

compared to the corresponding p-benziporphyrin (Figure 11).

The pyrrolic protons gave resonances at 7.14, 7.22, and

7.97 ppm, values that are between 0.23 and 0.52 ppm upﬁeld

from the corresponding resonances in 28. The naphthalene

protons were also anomalous. The 21,22-CH unit gave a singlet

at 6.93 ppm, but the AA⁰XX⁰system corresponding to the

supported by an analysis of bond lengths from X-ray crystallo-

graphy.³⁹The aromatic properties are believed to be due to

resonance contributors like 30 which have the necessary 18π

electron delocalization pathways.³⁹Nickel(II) and cadmium

complexes of 28 were also reported and these showed an

interesting η²-interaction with the p-phenylene unit.^15,39

Given the intriguing properties of p-benziporphyrins, we were

interested in seeing how the aromatic properties would be altered

for a naphthalene analogue of this system. A similar teeter-

tottering process might occur for a 1,4-naphthiporphyrin

(Scheme 9), but in this case the two conformations would not

be equivalent. We reasoned that conformation A would be less

favorable due to steric interactions and that the proposed system

would exist primarily as conformer B. This unit might be

expected to be better suited to support a macrocyclic ring current

and could thereby show an enhanced diamagnetic ring current.

Some time ago, we had attempted to prepare p-benziporphyrin

31 using the “3 þ 1” methodology from tripyrrane 13a and

terephthalaldehyde (Scheme 10), but no porphyrinoid products

could be isolated.⁴⁰Perhaps not surprisingly, reaction of 13a with

1,4-naphthalenedicarbaldehyde²⁶also failed to aﬀord any of the

desired naphthiporphyrin product 32 (Scheme 10). However,

the synthesis of tetraphenyl-1,4-naphthiporphyrin 33 was easily

carried out in three isolated steps from 1,4-naphthalenedicar-

boxylic acid (34, Scheme 11). Treatment of dicarboxylic acid 34

with thionyl chloride gave the corresponding diacyl chloride 35,

and this was used directly to carry out a double FriedelꢀCrafts

acylation reaction with benzene and AlCl₃to give excellent yields

of 1,4-dibenzoylnaphthalene (36). Reduction with sodium

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Scheme 11

Figure 10. UVꢀvis spectra of tetraphenyl-1,4-naphthiporphyrin 33 in

chloroform with 0 equiv (free base, red line), 1 equiv (monocation

33H^þ, blue line) and 10 equiv TFA (dication 33H₂^2þ, purple line).

Figure 11. 500 MHz proton NMR spectrum of tetraphenyl-1,4-

naphthiporphyrin 33 in CDCl₃.

supposedly external naphthalene protons gave two upﬁeld multi-

plets at 6.01 and 6.28 ppm. The data indicate that it is conformer

A, and not B, that is favored for this 1,4-naphthiporphyrin

(Scheme 9). This form is presumably favored due to π-stacking

interactions, but the bulky naphthalene unit is likely to increase

the tilt angle and diminish the aromatic properties for the

macrocycle. The proton NMR spectrum for naphthiporphyrin

33 was assigned using NOE diﬀerence proton NMR spectros-

copy, and these results showed a correlation between both the

21,22- and the 2¹,3¹-naphthalene protons and the o-protons on

the adjacent phenyl substituents. These correlations are consis-

tent with conformation A, as only the protons at positions 2¹

and 3¹would be expected to interact with the o-protons in con-

former B (see Supporting Information). Unfortunately, we have

not as yet been able to structurally characterize 33 by X-ray

crystallography.

Figure 12. Partial 500 MHz proton NMR spectra of naphthiporphyrin

33 in CDCl₃before and after carrying out a D₂O shake. The external

protons are shifted downﬁeld but the 2¹,2²,3¹, and 3²protons overlying

the system shift upﬁeld.

NMR solution of 33 in CDCl₃and the mixture shaken for several

min. The proton NMR spectrum was then rerun but the NH peak

could still not be identiﬁed. However, many of the peaks shifted

following the deuteration (Figure 12). The pyrrolic protons and

the 21,22-protonsonthe naphthalenesubunit all shifted downﬁeld

but the 2¹,2²,3¹,3²protons moved upﬁeld. Even though the shifts

were small (<0.1 ppm), these results are surprising as they indicate

that the diatropic characteristics of 1,4-naphthiporphyrin 33 are

enhanced upon deuteration. The changes could be attributed to

the shorter NꢀD bond replacing the original NꢀH unit, which

might allow the naphthalene unit in conformer A to tilt further

The NH resonance in the proton NMR spectrum of 33 could

not be identiﬁed and in an attempt to identify this resonance, a

D₂O shake was conducted. Two drops of D₂O were added to an

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toward the tripyrrolic component of the system and in so doing

improve π-conjugation around the macrocycle. Deuteration of

[18]annulene has been shown to have a similar eﬀect, where the

shorter CꢀD bonds apparently allow the 18-membered ring to

ﬂatten out, and this leads to leads to a small but measurable

increase in the aromatic ring current.⁴¹Similar observations have

alsobeen made for the antiaromaticcharacterof [16]annulene and

the aromatic characteristics of the related dianion.⁴²However,

having such a large eﬀect due to a single deuteration seemed

unrealistic. Therefore, a control experiment was conducted using

H₂O instead to D₂O. This resulted in slightly larger shifts than had

been observed with D₂O and demonstrated that the increased

diatropicity is not due to deuteration on the nitrogen atom.

Presumably the conformational changes that are responsible for

the observed changes in the NMR spectra result from hydrogen

bonding to the core nitrogens.

’ EXPERIMENTAL SECTION

1,3-Naphthalenedicarbaldehyde. The dialdehyde was pre-

pared by the procedure described by Ried et al.²⁶Recrystallization from

ethanol gave an off-white powder, mp 120.5ꢀ122 °C (lit. mp²⁶124 °C);

¹H NMR (500 MHz, CDCl₃): δ 7.70ꢀ7.74 (1H, m), 7.84ꢀ7.88 (1H,

m), 8.11 (1H, d, J = 8.2 Hz), 8.47 (1H, d, J = 1.6 Hz), 8.59 (1H, br s),

9.32 (1H, d, J = 8.6 Hz), 10.24 (1H, s), 10.45 (1H, s); ¹³C NMR

(CDCl₃): δ 125.8, 128.4, 130.4, 132.4, 132.6, 133.2, 133.3, 133.5, 133.7,

140.1, 191.0, 193.2.

9,13,14,18-Tetraethyl-8,19-dimethylbenziporphyrin (4).

Tripyrrane dicarboxylic acid 13a^24,25(100 mg, 0.22 mmol) was stirred

with TFA (1 mL) under nitrogen for 2 min. The mixture was diluted

with dichloromethane (99 mL) and isophthalic dicarboxaldehyde

(31 mg, 0.23 mmol) was immediately added in a single portion. The

resulting solution was stirred overnight under nitrogen in the dark and

then oxidized by stirring with DDQ (60 mg, 0.26 mmol) for 1 h. The

mixture was then washed with water, followed by saturated aqueous

sodium bicarbonate solution (the aqueous solutions were back-extracted

with chloroform at each stage in the extractions). The solvent was

removed under reduced pressure and the residue chromatographed on

grade 3 basic alumina, eluting with dichloromethane to give a dark blue

band. The solvent was removed under reduced pressure and recrystal-

lized from chloroformꢀmethanol to yield benziporphyrin (30 mg, 0.065

mmol, 29%) as dark-blue crystals, mp >300 °C (lit. mp¹¹>300 °C); ¹H

NMR (500 MHz, CDCl₃): δ 1.28 (6H, t, J = 7.6 Hz), 1.36 (6H, t, J =

7.6 Hz), 2.43 (6H, s), 2.77 (4H, q, J = 7.6 Hz), 2.86 (4H, q, J = 7.6 Hz),

6.57 (2H, s), 7.27 (2H, s), 7.75 (1H, t, J = 7.5 Hz), 7.90 (1H, br s), 7.98

(2H, dd, ³J = 7.5 Hz, ⁴J = 1.5 Hz), 8.93 (1H, br s); ¹H NMR (500 MHz,

trace TFA-CDCl₃): δ 1.28ꢀ1.34 (12H, 2 overlapping triplets), 2.62

(6H, s), 2.89 (8H, q, J = 7.7 Hz), 5.24 (1H, br s), 5.47 (1H, s), 6.91 (2H, s),

7.91 (1H, t, J = 7.7 Hz), 7.94 (2H, s), 8.19 (2H, d, J = 8.0 Hz);

¹H NMR (TFA-CDCl₃): δ 1.33 (6H, t, J = 7.7 Hz), 1.39 (6H, t, J =

7.7 Hz), 2.70 (6H, s), 2.96ꢀ3.01 (8H, 2 overlapping quartets), 4.97

(1H, s), 7.15 (2H, s), 8.01 (1H, t, J = 7.7 Hz), 8.15 (2H, s), 8.33 (2H,

d, J = 7.7 Hz), 9.23 (2H, br s); ¹³C NMR (CDCl₃): δ 10.3, 15.2, 16.0,

18.1, 18.4, 93.1, 122.7, 125.2, 129.0, 134.3, 137.4, 140.7, 141.3, 141.5,

148.0, 157.3, 169.2; ¹³C NMR (TFA-CDCl₃): δ 10.6, 14.2, 15.1, 18.1,

18.4, 94.4, 128.5, 132.1, 134.1, 140.6, 142.1, 143.9, 147.1, 149.0,

154.5, 162.8; HR MS (EI): Calcd for C₃₂H₃₅N₃: 461.2831. Found:

461.2832.

[9,13,14,18-Tetraethyl-8,19-dimethylbenziporphyrinato]-

nickel(II) (15a). Nickel(II) acetate tetrahydrate (22 mg, 0.088

mmol) was added to a solution of benziporphyrin 25 (20 mg,

0.044 mmol) in DMF (40 mL), and the solution was stirred under

reflux for 30 min. The solution was cooled, diluted with chloroform,

and washed with water. The organic layer was separated, evaporated

to dryness and chromatographed on grade 3 basic alumina,

eluting with chloroform, to give a dark green band. The solvent

was evaporated to dryness and the residue recrystallized from

chloroformꢀmethanol to yield the nickel(II) complex (10 mg,

0.019 mmol, 42%) as dark-green crystals, mp >300 °C; UVꢀvis

(CHCl₃): λ_max(log ε) 343 (4.20), 408 (4.22), 529 (3.43), 652 nm

(3.64); ¹H NMR (500 MHz, CDCl₃): δ 1.31 (6H, t, J = 7.7 Hz), 1.39

(6H, t, J = 7.7 Hz), 2.45 (6H, s), 2.87 (4H, q, J = 7.7 Hz), 2.94 (4H, q,

J = 7.7 Hz), 7.16 (2H, s), 7.48 (2H, s), 7.51 (1H, t, J = 7.3 Hz), 8.04

(2H, d, J = 7.3 Hz); ¹³C NMR (CDCl₃): δ 10.42, 15.37, 16.54, 18.52,

18.55, 29.92, 95.26, 123.41, 125.52, 135.95, 140.01, 141.32, 141.44,

144.76, 145.84, 153.14, 159.11; HR MS (EI): Calcd for C₃₂H₃₃N₃Ni:

517.2028. Found: 517.2022.

Addition of TFA to NMR solutions of 33 generated the

corresponding dication but this species gave poor quality NMR

spectra. However, the data suggested that the macrocycle retains

the same type of conformation. The 1,4-naphthiporphyrin was

1

further characterized by ¹Hꢀ H COSY, HSQC, and carbon-13

NMR spectroscopy and electron impact mass spectrometry.

’ CONCLUSIONS

The incorporation of naphthalene units into a carbaporphyr-

inoid framework leads to signiﬁcant changes compared to the

analogous benziporphyrins. Naphthiporphyrin 11, like benzipor-

phyrin 4, is nonaromatic, but protonation leads to the formation

of a dication 11H₂^2þwith an increased diamagnetic ring current

compared to the related benziporphyrin dication. Similarly,

oxynaphthiporphyrins 23 show a slight increase in their diatropic

character compared to oxybenziporphyrins 17. Furthermore,

although oxybenziporphyrins readily form dicationic species that

have lost most of their aromatic characteristics, oxynaphthipor-

phyrins do not favor the second protonation step. These results

are consistent with a valence bond theory interpretation of

porphyrinoid aromaticity based on the presence of 18π electron

delocalization pathways. In benziporphyrins, the competition

between the 6π electron arene and the 18π electron delocaliza-

tion pathways generally favors the former at the expense of the

latter. As the loss of a benzene unit from a naphthalene system

involves a smaller decrease in resonance stabilization energy,

naphthiporphyrins were expected to better facilitate porphyri-

noid aromaticity. Nevertheless, other factors may overwhelm this

eﬀect. Silver(III) complexes of oxynaphthiporphyrins are less

diatropic than the corresponding silver(III) oxybenziporphyrins

because the silver cation draws the macrocycle into a more planar

conformation that increases steric interactions between the

naphthalene unit and the adjacent meso-proton. This leads the

carbocyclic moiety to twist away, decreasing the eﬃciency of

π-conjugation. In tetraphenyl-1,4-naphthiporphyrin 33, the por-

phyrinoid favors a conformation where the naphthalene folds over

the rest of the macrocycle and steric interactions disrupt much of

the π-conjugation. The 1,4-naphthiporphyrin is potentially of

value in the formation of metallo-derivatives with unusual coordi-

nation properties as the extra fused benzene ring will lie over a

metal cation that binds to the three nitrogen atoms. The results

from our studies demonstrate that the introduction of a naphtha-

lene unit in place of a benzene moiety can increase the aromatic

character, but these modiﬁcations may lead to unexpected changes

that extend our understanding of carbaporphyrinoid systems.

[9,13,14,18-Tetraethyl-8,19-dimethylbenziporphyrinato]-

palladium(II) (15b). Palladium(II) acetate (20 mg, 0.089 mmol)

was added to a solution of benziporphyrin 4 (20 mg, 0.043 mmol) in

acetonitrile (40 mL), and the solution was stirred under reflux for

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30 min. The solution was cooled, diluted with chloroform, washed

with water, and the organic layer separated and then evaporated to

dryness. The residue was chromatographed with grade 3 basic

alumina, eluting with chloroform, and the product was collected as

a reddish/brown band. The solvent was evaporated to dryness and

the residue recrystallized from chloroformꢀmethanol to yield the

palladium(II) complex (8.5 mg, 0.015 mmol, 35%) as dark-purple

crystals, mp >300 °C; UVꢀvis (CHCl₃): λ_max(log ε) 309 (4.38), 345

(4.19), 406 (4.58), 516 (3.54), 707 (3.47), 778 nm (3.38); ¹H NMR

(500 MHz, CDCl₃): δ 1.40 (6H, t, J = 7.7 Hz), 1.45 (6H, t, J = 7.7 Hz),

2.63 (6H, s), 2.97ꢀ3.04 (8H, 4 overlapping quartets), 7.35 (2H, s),

7.71 (1H, t, J = 7.4 Hz), 7.72 (2H, s), 8.12 (2H, d, J = 7.4 Hz); ¹³C

NMR (CDCl₃): δ 10.5, 15.4, 16.7, 18.6, 18.9, 95.5, 125.7, 126.8,

132.4, 138.6, 141.2, 142.3, 144.0, 144.5, 153.4, 156.8; HR MS (EI):

Calcd for C₃₂H₃₃N₃Pd: 565.1709. Found: 565.1699.

3 basic alumina, eluting with chloroform, and the product was collected as a

reddish/brown band. The solvent was evaporated to dryness and the

residue recrystallized from chloroformꢀmethanol to yield the palladium-

(II) complex (8.6 mg, 0.014 mmol, 37%) as dark-purple crystals, mp

>300 °C; UVꢀvis (CHCl₃): λ_max(log ε) 273 (4.71), 319 (sh, 4.45), 421

(4.51), 518 (3.80), 562 (3.82), 599 (3.85), 680 (3.36), 740 nm (3.45); ¹H

NMR (500 MHz, CDCl₃): δ 1.37ꢀ1.47 (12H, 4 overlapping triplets),

2.58 (3H, s), 2.72 (3H, s), 2.94 (2H, q, J = 7.7 Hz), 2.98ꢀ3.05 (6H, 3

overlapping quartets), 7.27 (1H, s), 7.39 (1H, s), 7.55 (1H, t, J = 7.3 Hz),

7.64 (1H, s), 7.68 (1H, t, J = 7.6 Hz), 8.02 (1H, d, J = 7.5 Hz), 8.50 (1H, s),

8.82ꢀ8.84 (2H, overlapping singlet and doublet); ¹³C NMR (CDCl₃): δ

10.4, 10.7, 15.3, 15.6, 16.7, 17.6, 18.6, 18.7, 18.9, 19.0, 95.5, 95.7, 118.3,

124.1, 125.5, 126.8, 128.3, 130.1, 130.7, 133.1, 138.3, 138.7, 139.3, 140.5,

141.5, 142.3, 143.2, 143.4, 144.1, 144.3, 145.6, 152.2, 153.3, 155.3, 157.0;

HR MS (EI): Calcd for C₃₆H₃₅N₃Pd: 615.1866. Found: 615.1849

2,4-Dibromo-1-methoxynaphthalene (21). Bromine (20.9 g,

0.13 mol) in acetic acid (40 mL) was added dropwise over a period of 30

min to a stirred solution of 1-methoxynaphthalene (10.31 g, 65.2 mmol)

in acetic acid and the resulting mixture was stirred for a further 1 h at

room temperature and a further 2 h under reflux. The solution was

poured into iceꢀwater and the resulting precipitate suction filtered and

washed well with water. Recrystallization from ethanol gave the dibromo

derivative (19.45 g, 61.5 mmol, 94%) as an off-white solid, mp 51ꢀ52 °C

9,13,14,18-Tetraethyl-8,19-dimethylnaphthiporphyrin (11).

Tripyrrane dicarboxylic acid 13a^24,25(100 mg, 0.22 mmol) was stirred with

TFA (1 mL) under nitrogen for 2 min. The mixture was diluted with

dichloromethane (99 mL) and naphthalene-1,3-dicarboxaldehyde²⁶

(44 mg, 0.24 mmol) was immediately added in a single portion. The

resulting solution was stirred overnight under nitrogen in the dark and then

oxidized by stirring with DDQ (100 mg, 0.44 mmol) for 1 h. The mixture

was then washed with water, followed by saturated sodium bicarbonate (the

aqueous solutions were back-extracted with chloroform at each stage in the

extractions). The solvent was removed under reduced pressure and the

residue chromatographed on grade 3 basic alumina, eluting with dichlor-

omethane, to give a dark turquoise band. The solvent was removed under

reduced pressure and recrystallized from chloroformꢀmethanol to yield

naphthiporphyrin (27 mg, 0.053 mmol, 24%) as dark-green crystals, mp

>300 °C; UVꢀvis (CHCl₃): λ_max(log ε) 329 (4.73), 410 (4.80), 521 (sh,

3.64), 556 (3.69), 601 (3.66), 652 (3.66), 700 (3.63), 767 nm (3.36);

UVꢀvis (50 eq TFA-CHCl₃): λ_max(log ε) 333 (4.51), 413 (4.55), 609

(3.99), 708 nm (4.27); UVꢀvis (10% TFA-CHCl₃): λ_max(log ε) 330

1

(lit. mp⁴³54ꢀ55 °C); H NMR (500 MHz, CDCl₃): δ 4.00 (3H, s),

7.58ꢀ7.65 (2H, m), 7.91 (1H, s), 8.13ꢀ8.15 (1H, m), 8.17ꢀ8.19

(1H, m); ¹³C NMR (CDCl₃): δ 61.8, 112.3, 118.3, 122.8, 127.8, 127.9,

128.1, 130.0, 132.4, 133.2, 153.4.

4-Methoxynaphthalene-1,3-dicarbaldehyde (22). n-Butyl-

lithium in hexanes (24 mL, 1.6 M) was added dropwise over a period

of 25 min to a stirred solution of dibromonaphthalene 21 (3.60 g,

11.4 mmol) in anhydrous ether (180 mL) at room temperature. The

resulting mixture was stirred for a 3 h at ambient temperature, DMF

(3.2 g, 44 mmol) was added dropwise and the mixture was stirred for a

further 2 h. Hydrochloric acid (10%, 60 mL) was then added cautiously

and the resulting mixture was extracted with ether, washed with 5%

sodium bicarbonate and dried over magnesium sulfate. Recrystallization

from ethanol gave the dialdehyde (1.32 g, 6.17 mmol, 54%) as fluffy

yellow needles, mp 137ꢀ138 °C; ¹H NMR (500 MHz, CDCl₃): δ 4.24

(3H, s), 7.67ꢀ7.72 (1H, m), 7.82ꢀ7.85 (1H, m), 8.34 (1H, d, J =

8.4 Hz), 8.41 (1H,s), 9.37(1H, d, J=8.5 Hz), 10.30(1H, s), 10.60 (1H,s);

¹³C NMR (CDCl₃): δ 66.4, 123.9, 124.1, 126.3, 128.2, 128.57,

128.65, 132.5, 134.8, 135.8, 167.1, 188.4, 192.7. Anal. Calcd for

C₁₃H₁₀O₃: C, 72.89; H, 4.70. Found: C, 72.43; H, 4.61.

1-Hydroxynaphthalene-1,3-dicarbaldehyde (20). Boron tri-

bromide in dichloromethane (1.0 M, 2 mL) was added to a stirred

solution of dialdehyde 22 (214 mg, 1.00 mmol) in dichloromethane

(10 mL) and the mixture was stirred for 1 h at room temperature. The

solution was washed with 10% hydrochloric acid and water, and dried

over sodium sulfate. Recrystallization from ethanolꢀwater gave the

naphthol (157 mg, 0.78 mmol, 78%) as small yellow needles, mp

148.5ꢀ149.5 °C (lit. mp⁴⁴137 °C); ¹H NMR (500 MHz, CDCl₃): δ

7.66ꢀ7.70 (1H, m), 7.86ꢀ7.89 (1H, m), 8.07 (1H, s), 8.54 (1H, d, J =

8.3 Hz), 9.31 (1H, d, J = 8.6 Hz), 10.07 (1H, s), 10.24 (1H, s), 13.25

(1H, s); ¹³C NMR (CDCl₃): δ 113.5, 124.6, 124.7, 125.3, 127.4, 133.5,

134.4, 139.7, 166.5, 191.1, 195.6.

1

(4.62), 400 (4.75), 571 (4.08), 617 (4.27), 731 nm (3.77); H NMR

(500 MHz, CDCl₃):δ1.28 (6H, q, J= 7.7 Hz), 1.35 (6H, t, J= 7.6 Hz), 2.45

(3H, s), 2.54 (3H, s), 2.74ꢀ2.87 (8H, m), 6.54 (1H, s), 6.56 (1H, s), 7.37

(1H, s), 7.60 (1H, t, J = 7.6 Hz), 7.73 (1H, t, J = 7.6 Hz), 8.06 (1H, d, J =

7.7 Hz), 8.08 (1H, s), 8.21 (1H, s), 8.51 (1H, s), 8.76 (1H, d, J = 8.5 Hz),

9.30 (1H, br s); ¹H NMR (500 MHz, trace TFA-CDCl₃): δ 1.32ꢀ1.39

(12H, 4 overlapping triplets), 2.74 (3H, s), 2.78 (3H, s), 2.97ꢀ3.03 (8H,

m), 4.44 (1H, s), 7.20 (1H, s), 7.22 (1H, s), 7.77 (1H, t, J = 7.5 Hz), 7.95

(1H, t, J = 7.7 Hz), 8.18 (1H, d, J = 8.0 Hz), 8.31 (1H, s), 8.46 (1H, d, J =

8.4 Hz), 8.62 (1H, br s), 8.73 (1H, br s), 8.83 (1H, s), 8.97 (1H, s), 9.09

(1H, s); ¹H NMR (500 MHz, TFA-CDCl₃): δ 1.31ꢀ1.39 (12H, 4

overlapping triplets), 2.73 (3H, s), 2.77 (3H, s), 2.96ꢀ3.02 (8H, m),

4.50 (1H, br d), 6.64 (1H, v br), 7.17 (1H, s), 7.20 (1H, s), 7.76 (1H, t, J =

7.5 Hz), 7.92ꢀ7.96 (1H, m), 8.17 (1H, s), 8.29 (1H, s), 8.45 (1H, d, J =

8.4 Hz), 8.73 (1H, br s), 8.81 (1H, s), 8.95 (1H, s), 9.20 (1H, br s); ¹³C

NMR (CDCl₃): δ 10.6, 10.8, 15.4, 15.5, 16.16, 16.17, 18.2, 18.6, 95.1, 93.2,

115.7, 122.7, 123.3, 126.3, 128.5, 130.0, 130.3, 131.6, 134.8, 135.2, 139.3,

140.4, 140.5, 141.0, 141.2, 141.3, 141.9, 147.8, 148.1, 157.1, 157.2, 169.0,

169.5; ¹³C NMR (TFA-CDCl₃): δ 10.8, 10.9, 14.5, 15.38, 15.40, 18.29,

18.34, 18.5, 93.9, 94.2, 107.0, 122.8, 126.4, 127.4, 128.8, 129.3, 129.7, 132.4,

133.4, 135.9, 136.0, 136.0, 141.4, 141.5, 143.1, 143.7, 145.3, 146.4, 146.6,

147.5, 148.1, 153.2, 153.3, 161.1, 161.2; HR MS (EI): Calcd for C₃₆H₃₇N₃

þ 2H: 513.3144. Found: 513.3134. Anal. Calcd for C₃₆H₃₇N₃.¹/₂₀CHCl₃:

C, 83.64; H, 7.21; N, 8.12. Found: C, 83.52; H, 7.19; N, 8.16.

9,18-Diethyl-8,19-dimethyl-13,14-diphenyl-2-oxybenzipor-

phyrin (17b). Tripyrrane dicarboxylic acid 13b^6b(100 mg, 0.18 mmol)

was stirred under nitrogen with TFA (1 mL) in a 50 mL pear shaped

flask at room temperature for 10 min. The solution was diluted with

dichloromethane (39 mL), 5-formylsalicylaldehyde (27 mg, 0.18 mmol)

was added and the resulting mixture stirred at room temperature for 2 h.

The solution was neutralized by the dropwise addition of triethylamine,

DDQ (98%, 42 mg, 0.18 mmol) was added, and the mixture was stirred

for an additional 1 h. The solution was washed with water and the solvent

[9,13,14,18-Tetraethyl-8,19-

dimethylnaphthiporphyrinato]palladium(II) (16). Palladium-

(II) acetate (20 mg, 0.089 mmol) was added to a solution of naphthipor-

phyrin 11 (20 mg, 0.039 mmol) in acetonitrile (40 mL), and the solution

was stirred under reflux for 30 min. The solution was cooled, diluted with

chloroform, washed with water, and the organic layer separated and then

evaporated to dryness. The residue was chromatographed with grade

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The Journal of Organic Chemistry

ARTICLE

removed on a rotary evaporator. The residue was purified on a grade 3

neutral alumina column, eluting initially with dichloromethane. After a

pink band had been collected, the solvent was switched to chloroform

and the product eluted as a dark-green band. Recrystallization from

chloroformꢀmethanol gave the oxybenziporphyrin (47 mg, 0.082

mmol, 45%) as a dark-purple solid, mp >300 °C; UVꢀvis (CHCl₃):

λ_max(log ε) 343 (4.42), 432 (5.25), 453 (4.87), 594 (4.47), 641 (3.96),

704 nm (3.82); UVꢀvis (80 equiv TFA-CHCl₃): λ_max(log ε) 328

(4.41), 433 (5.23), 470 (4.77) 613 (4.26), 696 nm (3.85); UVꢀvis (20%

TFA-CHCl₃): λ_max(log ε) 355 (4.71), 437 (4.92), 560 (3.89), 607

128.8, 132.1, 132.7, 133.4, 134.0, 135.3, 136.6, 137.1, 137.8, 138.7, 140.6,

144.6, 144.7, 154.3, 154.8, 187.3; ¹³C NMR (TFA-CDCl₃): δ 11.7, 16.1,

17.1, 19.67, 19.71, 92.8, 93.8, 113.2, 117.3, 122.1, 123.4, 127.5, 129.0,

129.3, 131.7, 135.3, 139.0, 140.0, 140.5, 140.7, 141.4, 142.1, 143.3, 143.7,

144.9, 186.7; HR MS (EI): calcd for C₃₆H₃₇N₃O: m/z 527.2937; found:

527.2932. Anal. Calcd for C₃₆H₃₇N₃O.¹/₁₀CHCl₃: C, 80.35; H, 6.93; N,

7.79. Found: C, 80.56; H, 6.99; N, 7.87.

9,18-Diethyl-8,19-dimethyl-13,14-diphenyl-2-oxynaphthi-

porphyrin (23b). Tripyrrane 13b^6b(212 mg, 0.38 mmol) and

dialdehyde 22 (82.7 mg, 0.38 mmol) were reacted under the fore-

going conditions. Recrystallization from chloroformꢀmethanol gave

the oxynaphthiporphyrin (88 mg, 0.14 mg, 36%) as purple crystals,

mp 240 °C, dec; UVꢀvis (CHCl₃): λ_max(log ε) 406 (sh, 4.70), 431

(5.35), 446 (5.02), 540 (3.90), 584 (4.59), 625 (4.14), 686 nm (3.74);

UVꢀvis (80 equiv TFA-CHCl₃): λ_max(log ε) 324 (4.47), 435 (5.32),

462 (4.94), 553 (sh, 3.88), 578 (sh, 4.07), 603 (4.35), 622 (4.39),

675 nm (3.87); UVꢀvis (50% TFA-CHCl₃): λ_max(log ε) 338 (4.46),

376 (4.66), 416 (sh, 4.65), 446 (4.89), 465 (4.85), 645 (4.48), 699

(4.10), 775 nm (3.93); ¹H NMR (500 MHz, CDCl₃): δ ꢀ7.26 (1H, s),

ꢀ3.76 (2H, br s), 1.68 (3H, t, J = 7.7 Hz), 1.71 (3H, t, J = 7.7 Hz), 3.50

(3H, s), 3.58 (3H, s), 3.78ꢀ3.86 (4H, 2 overlapping quartets),

7.59ꢀ7.63 (2H, m), 7.67ꢀ7.71 (4H, m), 7.74 (1H, t, J = 7.5 Hz),

7.93ꢀ7.96 (4H, m), 7.95ꢀ7.99 (1H, m), 8.91 (1H, dd, J = 1.4,

7.7 Hz), 9.01 (1H, d, J = 8.2 Hz), 9.603 (1H, s), 9.605 (1H, s), 10.14

(1H, s), 10.73 (1H, s); ¹H NMR (500 MHz, TFA-CDCl₃): δ ꢀ5.69

(1H, s), ꢀ4.10 (1H, br s), ꢀ1.42 (1H, br s), ꢀ0.98 (1H, br s), 1.50

(3H, t, J = 7.7 Hz), 1.52 (3H, t, J = 7.7 Hz), 3.47 (6H, s), 3.82 (4H, q,

J= 7.7 Hz), 7.67ꢀ7.75 (6H, m), 7.78 (1H, t, J= 7.5 Hz), 7.90ꢀ7.94 (4H, m),

8.07ꢀ8.10 (1H, m), 8.81 (1H, dd, J = 1.3, 7.8 Hz), 8.96 (1H, d, J = 8.1 Hz),

9.80 (1H, s), 9.86 (1H, s), 10.60 (1H, s), 10.88 (1H, s);¹³C NMR (CDCl₃):

δ 12.0, 17.06, 17.11, 19.6, 98.0, 98.5, 103.0, 104.8, 113.4, 121.1, 123.5, 125.1,

127.5, 128.0, 128.7, 128.8, 132.5, 132.7, 133.0, 133.9, 135.6, 136.3, 137.3,

137.7, 137.9, 138.1, 138.7, 140.5, 144.5, 144.6, 152.9, 153.4, 187.5; ¹³C NMR

(TFA-CDCl₃): δ 12.0, 12.1, 16.3, 19.9, 95.6, 96.8, 111.2, 111.7, 120.1, 124.4,

127.6, 129.27, 129.29, 129.39, 129.40, 132.29, 132.34, 132.73, 132.77, 133.0,

135.0, 137.4, 138.2, 138.3, 139.4, 139.5, 140.0, 140.1, 140.5, 140.8, 141.0,

141.2, 142.5, 190.0; HR MS (EI): Calcd for C₄₄H₃₇N₃O: 623.2937. Found:

623.2921. Anal. Calcd for C₄₄H₃₇N₃O.¹/₂₀CHCl₃: C, 84.01; H, 5.93; N, 6.67.

Found: C, 84.01; H, 5.93; N, 6.62.

[9,13,14,18-Tetraethyl-8,19-dimethyl-2-oxybenzipor-

phyrinato]silver(III) (26a). A suspension of silver(I) acetate (40 mg)

in methanol (10 mL) was added to a solution of 9,13,14,18-tetraethyl-8,19-

dimethyl-2-oxybenziporphyrin (17a, 20.0 mg) in chloroform (20 mL) and

the resulting mixture stirred at room temperature for 16 h. The mixture was

washed with water and evaporated under reduced pressure. The residue was

purified by column chromatography on grade 3 alumina, eluting with

chloroform and then 1% methanol-chloroform. Evaporation of the green

fractions afforded a dark residue. Recrystallization from chloroformꢀ

methanol gave the silver derivative (23.5 mg, 96%) as a dark-purple powder,

mp >300 °C; IR (KBr): ν 1641 (s), 1619 cm^ꢀ1(s, CdO str.); UVꢀvis

(CHCl₃): λ_max(log ε) 336 (4.51), 456 (4.94), 524 (3.55), 608 (4.40),

629 nm (4.20); ¹H NMR (400 MHz, CDCl₃): δ 1.60 (3H, t, J = 8 Hz),

1.64ꢀ1.73 (9H, 3 overlapping triplets), 3.10 (3H, s), 3.31 (3H, s), 3.62

(2H, q, J = 8 Hz), 3.67ꢀ3.75 (6H, 3 overlapping quartets), 7.32 (1H, d, J =

8.4 Hz), 8.44 (1H, d, J = 8.4 Hz), 8.69 (1H, s), 9.01 (1H, s), 9.13 (1H, s),

10.23 (1H, s); HRMS (EI): calcd for C₃₂H₃₂N₃OAg: 581.1610; found:

581.1608. Anal. Calcd for C₃₂H₃₂N₃OAg.¹/₈CHCl₃: C, 64.51; H, 5.37; N,

7.02. Found: C, 64.56; H, 5.38; N, 6.95.

1

(4.29), 707 (3.88), 778 nm (4.04); H NMR (500 MHz, CDCl₃):

δ ꢀ7.27 (1H, br d, J = 2.0 Hz), ꢀ3.67 (2H, br s), 1.62ꢀ1.68 (6H,

2 overlapping triplets), 3.30 (3H, s), 3.45 (3H, s), 3.68ꢀ3.75 (4H,

2 overlapping quartets), 7.27 (1H, d, J = 9.4 Hz), 7.59ꢀ7.63 (2H, m),

7.69 (4H, t, J = 7.5 Hz), 7.89ꢀ7.92 (4H, m), 8.42 (1H, dd, J = 2.0, 9.4

Hz), 8.91 (1H, s), 9.37 (1H, s), 9.41 (1H, s), 10.25 (1H, s); ¹H NMR

(500 MHz, TFA-CDCl₃): δ 1.32ꢀ1.36 (6H, 2 overlapping triplets),

2.96 (3H, s), 2.97 (3H, s), 3.15ꢀ3.20 (4H, 2 overlapping quartets), 5.29

(1H, s), 5.48 (1H, br s), 5.51 (1H, br s), 7.54ꢀ7.57 (4H, m), 7.58ꢀ7.62

(7H, m), 8.09 (1H, s), 8.13 (1H, s), 8.61 (1H, dd, J = 1.8, 8.7 Hz), 8.87

(1H, s), 9.47 (1H, s); ¹³C NMR (CDCl₃): δ 11.5, 11.8, 16.9, 17.0, 19.39,

19.43, 97.2, 99.1, 105.5, 110.9, 111.9, 122.0, 126.3, 127.61, 127.62, 128.7,

130.3, 132.2, 132,4, 134.5, 135.5, 136.0, 137.4, 138.01, 138.03, 138.2,

140.1, 144.7, 145.2, 147.0, 153.5, 154.8, 187.9; ¹³C NMR (TFA-

CDCl₃): δ 11.2, 14.9, 15.0, 18.8, 96.8, 98.0, 120.0, 120.5, 122.0, 124.4,

127.7, 129.6, 130.29, 130.32, 130.35, 131.0, 141.2, 141.8, 141.9, 142.2,

143.6, 144.1, 147.4, 148.3, 148.5, 149.3, 149.6, 155.3, 156.8, 171.2; HR

MS (FAB): calcd for C₄₀H₃₅N₃O þ H: m/z 574.2858; found: 574.2860.

Anal. Calcd for C₄₀H₃₅N₃O.¹/₄CHCl₃: C, 80.10; H, 5.89; N, 6.96.

Found: C, 80.17; H, 5.89; N, 7.01.

9,13,14,18-Tetraethyl-8,19-dimethyl-2-oxynaphthiporphyrin

(23a). Tripyrrane dicarboxylic acid 13a^24,25(100.2 mg) was stirred

with TFA (1 mL) under an atmosphere of nitrogen for 5 min. The

solution was diluted with dichloromethane (19 mL), followed

immediately by the addition of 4-methoxynaphthalene-1,3-dicarbal-

dehyde (22; 44.5 mg), and the mixture was stirred under nitrogen, in

the dark, for a further 3 h. After neutralization by the dropwise

addition of triethylamine, DDQ (51 mg) was added and the resulting

solution was stirred in the dark for an additional 1 h. The mixture was

washed with water and chromatographed on grade 3 neutral alumina,

eluting first with dichloromethane and then with chloroform. A deep

green fraction was collected with chloroform and recrystallized from

chloroformꢀmethanol to give the porphyrin analogue (39.4 mg;

35%) as sparkling purple needles, mp 283ꢀ284 °C; IR (KBr): ν 3343

(w, NH str.), 1630 cm^ꢀ1(s, CdO str.); UVꢀvis (CHCl₃): λ_max(log

ε) 404 (infl, 4.68), 429 (5.30), 447 (4.94), 537 (4.01), 579 (4.49), 619

(4.14), 683 nm (3.67); UVꢀvis (20 equiv TFA-CHCl₃): λ_max(log ε)

406 (infl, 4.65), 431 (5.31), 460 (4.97), 550 (sh, 4.01), 571 (sh, 4.08),

596 (4.36), 614 (4.38), 667 nm (3.75); UVꢀvis (50% TFA-CHCl₃):

λ_max(log ε) 331 (4.54), 368 (4.68), 441 (4.79), 460 (4.79), 635

(4.47), 689 (4.08), 760 nm (3.99); ¹H NMR (400 MHz, CDCl₃): δ

ꢀ7.42 (1H, s), 1.69 (3H, t, J = 7.6 Hz), 1.74ꢀ1.80 (9H, 3 overlapping

triplets), 3.40 (3H, s), 3.57 (3H, s), 3.74ꢀ3.81 (4H, 2 overlapping

quartets), 3.84 (2H, q, J = 7.6 Hz), 3.93 (2H, q, J = 7.7 Hz), 7.73 (1H,

3

4

t, J = 7.5 Hz), 7.96ꢀ8.00 (1H, m), 8.92 (1H, dd, J = 7.6 Hz, J =

1.4 Hz), 8.96 (1H, d, J = 8.1 Hz), 9.27 (1H, s), 9.33 (1H, s), 9.94 (1H,

s), 10.65 (1H, s); ¹H NMR (400 MHz, 1 drop TFA-CDCl₃;

monocation): δ ꢀ5.69 (1H, s), ꢀ4.41 (1H, br s), ꢀ1.42 (1H, br s),

ꢀ0.98 (1H, br s), 1.54ꢀ1.60 (6H, 2 overlapping triplets), 1.78ꢀ1.85

(6H, 2 overlapping triplets), 3.46 (3H, s), 3.47 (3H, s), 3.89ꢀ4.01

(8H, m), 7.76 (1H, t, J = 7.6 Hz), 8.04ꢀ8.08 (1H, m), 8.82 (1H, d, J =

7.8 Hz), 8.94 (1H, d, J = 8.0 Hz), 9.71 (1H, s), 9.78 (1H, s), 10.55

(1H, s), 10.86 (1H, s); ¹³C NMR (CDCl₃): δ 11.8, 11.9, 17.2, 18.4,

19.5, 19.6, 19.9, 94.2, 94.6, 103.0, 113.6, 120.1, 123.0, 124.9, 127.7,

[9,18-Diethyl-8,19-dimethyl-13,14-diphenyl-2-oxybenzipor-

phyrinato]silver(III) (26b). A suspension of silver(I) acetate (40 mg) in

methanol (10 mL) was added to a solution of 17b (20.0 mg) in chloroform

(20 mL) and the resulting mixture stirred at room temperature for 16 h. The

mixture was washed with water and evaporated under reduced pressure.

The residue was purified by column chromatography on grade 3 alumina,

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ARTICLE

eluting with chloroform and then 1% methanol-chloroform. Evaporation of

the green fractions afforded a dark residue. Recrystallization from chlor-

oformꢀmethanol gave the silver complex (22.5 mg, 95%) as a dark-green

powder, mp >300 °C; IR (KBr): ν 1639 (s), 1618 cm^ꢀ1(s, CdO str.);

UVꢀvis (CHCl₃): λ_max(log ε) 344 (4.59), 458 (4.96), 526 (3.57), 614

(4.48), 638 nm (4.31); ¹H NMR (400 MHz, CDCl₃): δ 1.67ꢀ1.74 (6H, 2

overlapping triplets), 3.30 (3H, s), 3.43 (3H, s), 3.72ꢀ3.79 (4H, 2

overlapping quartets), 7.31 (1H, d, J = 8.0 Hz), 7.65 (2H, t, J = 7.6 Hz),

7.73 (4H, t, J = 7.4 Hz), 7.99ꢀ8.02 (4H, m), 8.47 (1H, d, J = 8.0 Hz), 8.87

(1H, s), 9.69 (1H, s), 9.71 (1H, s), 10.32 (1H, s); ¹H NMR (400 MHz, d₄-

MeOH-CDCl₃, 50 °C): δ 1.56 (3H, t, J = 7.6 Hz), 1.63 (3H, t, J = 7.6 Hz),

3.02 (3H, s), 3.24 (3H, s), 3.55 (2H, q, J = 7.6 Hz), 3.62 (2H, q, J = 7.6 Hz),

7.04 (1H, d, J = 8.4 Hz), 7.60 (2H, t, J = 7.6 Hz), 7.66ꢀ7.71 (4H, m),

7.92ꢀ7.96 (4H, m), 8.02 (1H, d, J = 8.8 Hz), 8.28 (1H, s), 9.43 (1H, s),

9.46 (1H, s), 9.92 (1H, s); ¹³C NMR (d₄-MeOH-CDCl₃, 50 °C): δ 11.2,

11.6, 16.7, 16.8, 20.1, 20.3, 29.8, 99.9, 101.2, 113.5, 115.9, 113.5, 115.9,

125.7, 127.9, 128.8, 132.5, 135.3, 139.1 (due to the very low solubility of the

silver complex, not all of the carbon-13 resonances could be identified);

HRMS (EI): calcd for C₄₀H₃₂N₃OAg: 677.1596; found: 677.1592. Anal.

Calcd for C₄₀H₃₂N₃OAg: C, 70.80; H, 4.75; N, 6.19. Found: C, 70.83; H,

4.65; N, 6.22.

[9,13,14,18-Tetraethyl-8,19-dimethyl-2-oxynaphthipor-

phyrinato]silver(III) (27a). A suspension of silver(I) acetate (40.5 mg)

in methanol (10 mL) was added to a solution of 23a (20.1 mg) in

chloroform (20 mL) and the resulting mixture stirred at room temperature

under nitrogen for 16 h. The mixture was washed with water (ꢁ2), dried

over sodium sulfate, and evaporated under reduced pressure. The greenish-

purple residue was purified by column chromatography on grade 3 alumina,

eluting with dichloromethane and then chloroform. Evaporation of the

green fractions and recrystallization from chloroform-hexanes gave the silver

chelate (21.1 mg, 87%) as dark greyish-green crystals, mp 274ꢀ275 °C; IR

(KBr): ν 1642 (s), 1619 cm^ꢀ1(s, CdO str.); UVꢀvis (CHCl₃): λ_max

(log ε) 456 (4.975), 522 (3.70), 593 (4.39), 616 nm (4.075); ¹H NMR

(500 MHz, CDCl₃): δ 1.58 (3H, t, J = 7.7 Hz), 1.68ꢀ1.75 (9H, 3

overlapping triplets), 3.07 (3H, s), 3.36 (3H, s), 3.56 (2H, q, J = 7.7 Hz),

3.66ꢀ3.75 (6H, 3 overlapping quartets), 7.72 (1H, t, J= 7.8 Hz), 7.85ꢀ7.88

(1H, m), 8.35 (1H, d, J = 7.9 Hz), 8.75 (1H, dd, J = 1.3, 7.7 Hz), 9.02 (1H,

s), 9.16 (1H, s), 9.29 (1H, s), 9.95 (1H, s); ¹³C NMR (CDCl₃): δ 11.4,

11.8, 17.2, 17.3, 18.2, 19.7 (2), 20.1, 20.3, 95.7, 95.8, 107.5 (d, J = 3.1 Hz),

109.9 (d, J = 3.4 Hz), 110.7, 113.5, 126.9, 127.7, 128.4, 131.6, 132.4, 132.8,

133.4 (m), 135.1 (d, J = 2.8 Hz), 136.8, 138.0, 138.4, 138.9, 141.1, 141.2 (d,

J = 3.1 Hz), 141.4, 142.4 (d, J = 3.3 Hz), 142.9, 163.2 (dd, J= 50.1, 56.4 Hz),

191.6; FD MS: m/z (rel. int.) 635.2 (7.3), 634.2 (35), 633.2 (90), 632.1

(40), 631.2 (100, M^þ). Anal. Calcd for C₃₆H₃₄N₃OAg: C, 68.36; H, 5.42;

N, 6.64. Found: C, 68.30; H, 5.44; N, 6.57.

[9,18-Diethyl-8,19-dimethyl-13,14-diphenyl-2-oxynaphthi-

porphyrinato]silver(III) (27b). Oxynaphthiporphyrin 23b (23.0 mg,

0.0369 mmol) was reacted with silver(I) acetate (40 mg) under the

foregoing conditions. Recrystallization from chloroform-hexanes gave the

silver derivative (18.4 mg, 0.0253 mmol, 68%) as green crystals, mp

275ꢀ276 °C; UVꢀvis (CHCl₃): λ_max(log ε) 332 (4.29), 386 (sh,

4.34), 430 (infl, 4.38), 458 (5.00), 521 (3.65), 599 (4.43), 622 nm (sh,

4.18); ¹H NMR (500 MHz, CDCl₃): δ 1.55 (3H, t, J = 7.7 Hz), 1.64 (3H, t,

J = 7.7 Hz), 3.11 (3H, s), 3.34 (3H, s), 3.52 (2H, q, J = 7.7 Hz), 3.65 (2H, q,

J = 7.7 Hz), 7.61ꢀ7.64 (2H, m), 7.67ꢀ7.71 (4H, m), 7.80ꢀ7.84 (1H, m),

7.86ꢀ7.91 (4H, m), 8.23 (1H, d, J = 8.0 Hz), 8.68 (1H, dd, J = 1.4, 7.7 Hz),

9.29 (1H, s), 9.42 (1H, s), 9.52 (1H, s), 9.85 (1H, s); ¹³CNMR(CDCl₃):δ

11.5, 11.8, 17.06, 17.09, 20.2, 20.4, 99.5, 99.7, 107.30, 107.33, 109.22,

109.25, 111.8, 114.2, 127.1, 127.69, 127.71, 128.6, 128.77, 128.78, 131.4,

132.5, 132.6, 133.8, 134.0, 134.4, 135.44, 135.46, 135.55, 135.59, 137.7,

137.8, 138.4, 138.9, 140.3, 140.5, 142.5, 142.9, 143.6, 191.7. HR MS (EI):

Calcd for C₄₄H₃₄N₃OAg: 727.1753. Found: 727.1737. Anal. Calcd for

C₄₄H₃₄N₃OAg: C, 72.53; H, 4.70; N, 5.77. Found: C, 72.46; H, 4.64;

N, 5.77.

1,4-Dibenzoylnaphthalene (36). Thionyl chloride (40 mL) was

added to 1,4-naphthalenedicarboxylic acid (10.00 g, 46.3 mmol) in a

100 mL round-bottom flask. DMF (10 drops) was added and the stirred

mixture was heated under reflux for 1 h. The excess thionyl chloride was

removed on a rotary evaporator to give a pale yellow liquid that solidified

on standing. The diacyl chloride was transferred to a 1 L round-bottom

flask and dissolved in benzene (400 mL). Aluminum chloride (15 g) was

added in several portions to the stirred solution, which initially turned

dark brown but then lightened up to produce an orange solution. The

mixture was stirred under reflux overnight, poured into a mixture of ice

(400 g) and hydrochloric acid (46 mL) and extracted with ether (3 ꢁ

200 mL). The combined ether layers were dried over sodium sulfate and

evaporated under reduced pressure. The residue was recrystallized from

ethanolꢀwater to give the diketone (13.45 g, 40.0 mmol, 86%) as white

1

crystals, mp 101.5ꢀ102 °C (lit. mp⁴⁵106 °C); H NMR (500 MHz,

CDCl₃): δ 7.47ꢀ7.51 (4H, m), 7.52 (2H, AA⁰XX⁰system), 7.60 (2H, s),

7.61ꢀ7.65 (2H, m), 7.89ꢀ7.92 (4H, m), 8.05 (2H, AA⁰XX⁰system);

¹³C NMR (CDCl₃): δ 125.5, 126.3, 127.9, 128.9, 130.6, 131.3, 133.9,

137.9, 139.4, 197.8.

1,4-Bis(phenylhydroxymethyl)naphthalene (37). 1,4-Di-

benzoylnaphthalene (10.00 g, 29.7 mmol) was heated with ethanol

(200 mL) in a 1 L Erlenmeyer flask until it had completely dissolved. The

mixture was allowed to cool to 35 °C and sodium borohydride (2.25 g)

was added. The mixture was stirred for 15 min, water (200 mL) was

added and the mixture was heated on a boiling water bath for 20 min.

The flask was removed from the heat and mixture diluted with water

(400 mL). The flask was cooled in ice, the resulting precipitate was

suction filtered, and the solid dried in vacuo to give the dicarbinol

(9.91 g, 29.1 mmol, 98%) as a white powder, mp 169ꢀ171 °C. As

expected, the NMR data were consistent with the presence of two

1

diastereomers. H NMR (500 MHz, CDCl₃): δ 2.35ꢀ2.38 (2H, 2

overlapping doublets), 6.53 (d, J = 3.3 Hz), 6.54 (d, J = 3.3 Hz) (2H

combined), 7.26ꢀ7.29 (2H, m), 7.31ꢀ7.35 (4H, m), 7.39ꢀ7.42 (6H, m),

7.62 (s), 7.65 (s) (2H combined), 8.05ꢀ8.10 (2H, m); ¹³C NMR

(CDCl₃): δ 73.6, 73.8, 124.1, 124.3, 124.6, 124.8, 125.9, 127.0, 127.1,

127.7, 127.8, 128.57, 128.60, 131.1, 131.2, 138.95, 139.02, 143.02,

143.04. Anal. Calcd for C₂₄H₁₆O₂.¹/₁₀H₂O: C, 84.23; H, 5.95.

Found: C, 84.08; H, 5.91.

5,10,15,20-Tetraphenyl-1,4-naphthiporphyrin (33). Dicar-

binol 37 (340 mg, 1.00 mmol), pyrrole (208 μL, 201 mg, 3.00 mmol) and

benzaldehyde (204 μL, 212 mg, 2.00 mmol) were dissolved in dichlor-

omethane (900 mL). BF₃.Et₂O in dichloromethane (10% v/v, 1 mL) was

added and the mixture was stirred under nitrogen at room temperature for

2 h. DDQ (680 mg, 3 mmol) was added and the mixture stirred for a

further 10 min. The solvent was removed on a rotary evaporator, and the

residue purified on a grade 2 basic alumina column eluting initially with

dichloromethaneandthenwithchloroform. An impure porphyrinfraction

eluted initially, followed by a green band corresponding to the product.

Recrystallization from chloroformꢀmethanol gave the tetraphenyl-

naphthiporphyrin (24ꢀ31 mg, 0.035ꢀ0.046 mmol, 3.5ꢀ4.6%) as a

dark-green solid, mp >300 °C, darkens at 200 °C; UVꢀvis (CHCl₃):

λ_max(log ε) 353 (4.45), 466 (4.59), 632 (4.26), 663 nm (infl, 4.18);

UVꢀvis (1 equiv TFA-CHCl₃): λ_max(log ε) 368 (4.35), 488 (4.77),

757 nm (4.25); UVꢀvis (10% TFA-CHCl₃): λ_max(log ε) 384 (4.43), 471

1

(4.82), 731 nm (4.45); H NMR (500 MHz, CDCl₃): δ 6.01 (2H,

AA⁰XX⁰system), 6.28 (2H, AA⁰XX⁰system), 6.93 (2H, s), 7.14 (2H, s),

7.22 (2H, d, J = 4.7 Hz), 7.47ꢀ7.50 (6H, m), 7.54ꢀ7.57 (2H, m),

7.58ꢀ7.63 (4H, m), 7.64ꢀ7.68 (4H, m), 7.97 (2H, d, J = 4.7 Hz),

8.08ꢀ8.10 (4H, m); ¹H NMR (500 MHz, TFA-CDCl₃): δ 6.14 (4H, br),

7.26ꢀ7.66 (2H, v br), 7.77 (4H, t, J = 7.5 Hz), 7.81ꢀ7.88 (6H, m),

7.98ꢀ8.06 (8H, m), 8.18 (2H, br), 8.46 (2H, d, J = 7.3 Hz), 8.92 (2H, br);

¹³C NMR (CDCl₃): δ 116.0, 124.1, 124.3, 124.5, 127.46, 127.50, 128.6,

128.9, 130.4, 132.8, 133.3, 133.5, 134.0, 135.1, 136.7, 141.3, 142.1, 144.7,

146.4, 148.6, 159.0, 164.6; ¹³C NMR (TFA-CDCl₃): δ 119.1, 128.7,

5649

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The Journal of Organic Chemistry

ARTICLE

128.8, 130.71, 130.75, 131.6, 134.1, 134.3, 134.5, 135.2, 135.3, 137.8,

138.3, 140.4, 147.4, 148.3, 151.5; HR MS (EI): Calcd for C₅₀H₃₃N₃:

675.2674. Found: 675.2661. HR MS (EI): Calcd for C₅₀H₃₃N₃þ 2H:

677.2831. Found: 677.2815.

Fund, administered by the American Chemical Society. Funding

for a 500 MHz NMR spectrometer was provided by the National

Science Foundation under grant no. CHE-0722385. We thank

Youngstown State University Structure & Chemical Instrumen-

tation Facility’s Matthias Zeller for X-ray data collection. The

diﬀractometer was funded by NSF grant 0087210, Ohio Board of

Regents grant CAP-491, and YSU.

Crystallographic Experimental Details of 16. X-ray quality

crystals of 16 were obtained by slow evaporation of a CDCl₃solution.

The crystals were suspended in mineral oil at ambient temperature and a

suitable crystal was selected. A mineral oil coated black needle thereby

obtained of approximate dimensions 0.55 ꢁ 0.13 ꢁ 0.09 mm³was

mounted on a 50 μm polyimide micromount and transferred to a CCD

equipped X-ray diffractometer. The X-ray diffraction data were collected

at ꢀ173 °C using MoꢀK_R(λ = 0.71073 Å) radiation. Data collection

and cell refinement were performed using SMART and SAINTþ,

respectively.⁴⁶The unit cell parameters were obtained from a least-

squares refinement of 7528 centered reflections. Compound 16 was

found to crystallize in the monoclinic crystal system with the following

unit cell parameters: a = 8.7176(18) Å, b = 10.561(2) Å, c = 17.629(4) Å,

β = 104.079(3)°, Z = 2. The systematic absences indicated the space group

to be P2₁/n (no. 14).⁴⁷A total of 23309 reflections were collected, of which

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2

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=

2

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’ AUTHOR INFORMATION

Corresponding Author

*E-mail: tdlash@ilstu.edu.

’ ACKNOWLEDGMENT

This work was supported by the National Science Foundation

under grant no. CHE-0911699 and the Petroleum Research

5650

dx.doi.org/10.1021/jo200622s |J. Org. Chem. 2011, 76, 5636–5651

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