Porphyrins fused with unactivated polycyclic aromatic hydrocarbons

Article

pubs.acs.org/joc

Porphyrins Fused with Unactivated Polycyclic Aromatic

Hydrocarbons

Vyacheslav V. Diev,^†Cody W. Schlenker,^†Kenneth Hanson,^†Qiwen Zhong,^†Jeramy D. Zimmerman,^‡

Stephen R. Forrest,^‡and Mark E. Thompson*^,†

^†Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States

^‡Department of Electrical Engineering and Computer Science, and Physics, University of Michigan, Ann Arbor, Michigan 48109,

United States

S

* Supporting Information

ABSTRACT: A systematic study of the preparation of

porphyrins with extended conjugation by meso,β-fusion with

polycyclic aromatic hydrocarbons (PAHs) is reported. The

meso-positions of 5,15-unsubstituted porphyrins were readily

functionalized with PAHs. Ring fusion using standard Scholl

reaction conditions (FeCl₃, dichloromethane) occurs for

perylene-substituted porphyrins to give a porphyrin β,meso annulated with perylene rings (0.7:1 ratio of syn and anti isomers).

The naphthalene, pyrene, and coronene derivatives do not react under Scholl conditions but are fused using thermal

cyclodehydrogenation at high temperatures, giving mixtures of syn and anti isomers of the meso,β-fused porphyrins. For pyrenyl-

substituted porphyrins, a thermal method gives synthetically acceptable yields (>30%). Absorption spectra of the fused porphyrins

undergo a progressive bathochromic shift in a series of naphthyl (λ_max= 730 nm), coronenyl (λ_max= 780 nm), pyrenyl (λ_max= 815

nm), and perylenyl (λ_max= 900 nm) annulated porphyrins. Despite being conjugated with unsubstituted fused PAHs, the β,meso-

fused porphyrins are more soluble and processable than the parent nonfused precursors. Pyrenyl-fused porphyrins exhibit strong

fluorescence in the near-infrared (NIR) spectral region, with a progressive improvement in luminescent efficiency (up to 13%

with λ_max= 829 nm) with increasing degree of fusion. Fused pyrenyl-porphyrins have been used as broadband absorption donor

materials in photovoltaic cells, leading to devices that show comparatively high photovoltaic efficiencies.

method to extend the porphyrin π-system has been to construct

oligomers coupled through unsaturated bridges¹¹or by β-fusion

of meso-linked oligomers into so-called porphyrin “tapes”.¹²

While these materials lead to red-shifted absorbance (beyond

2000 nm), such oligomeric compounds typically require

multistep synthesis with low overall yields.^11,12Moreover,

these oligomers show pronounced aggregation in solution and

poor processability unless substituted with bulky solubilizing

groups.^11,12Very short S₁excited state lifetimes for the

porphyrin tapes also limits their application in a number of

areas that exploit luminescence in the NIR.^12d,13We have

chosen to explore the π-extension of porphyrins by fusing

polycyclic aromatic hydrocarbons (PAHs) at the β and meso

positions to create materials related to molecular graphenes.¹⁴

A schematic illustration of the direct fusion reaction studied is

shown in Scheme 1, along with the PAHs used in this study.

Advantages of the target porphyrin-PAH hybrids include their

precisely defined structures, significant π-extension with

relatively low mass and the potential for large-scale

preparation.¹⁴

INTRODUCTION

■

Porphyrins have been used in a broad range of organic

electronic applications,¹⁻⁶such as solar cells,^2,3photodetec-

tors,⁴light-emitting diodes,⁵and thin-film transistors,⁶because

of their intense absorbance in the visible region, chemical

stability and tunable optoelectronic properties.¹Among these

applications, organic photovoltaics (OPVs) have attracted a

great deal of recent interest as potentially low-cost options for

efficient solar energy conversion.⁷While the intense absorption

bands exhibited by simple porphyrins are a benefit for use in

OPVs, the comparatively narrow widths of these bands and the

absence of absorption in the near-infrared (NIR) limit their

utility in OPV applications. More than 50% of all solar radiation

lies in the NIR and IR portions of the solar spectrum (λ > 700

nm), so collecting light in this spectral region is critically

important to improve organic solar cell performance.^2a

Organic dyes with strong absorption and emission in the

NIR spectral region are also interesting for other potential

applications. The NIR region between 700−900 nm is known

as the optical window for biological imaging and therapeutic

applications, as this is where light has its maximum depth of

penetration into tissue.⁸Large, π-conjugated macrocycles,

including porphyrins, are also good candidates for two-photon

dyes because of their high transition dipole moments.⁹

Fusion of meso-bound polycyclic aromatic rings has attracted

significant attention recently, with both β,meso and β,meso,β

modes for fusion reported.¹⁵⁻¹⁷Fusion in the β,meso,β mode,

Extending the π-system can markedly red shift the absorption

Received: August 1, 2011

Published: November 13, 2011

of porphyrins relative to unsubstituted derivatives.^1,10−12One

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fusion of aromatic rings leads to red-shifted absorption and

markedly increases line widths of the Soret and Q bands.

The precursors for β,meso fusion can be easily obtained by

substitution with aromatic rings via well-developed methods

(e.g., halogenation and Pd-catalyzed couplings).^11e,24The

methods described here allow for the synthesis of fused

materials without added activating and solubilizing groups

on the aromatic rings, or by metalation of porphyrin with

nickel(II). Despite their large and unhindered π-systems, the

porphyrin−PAH materials obtained have improved solubility

and processability relative to their nonfused precursors. Strong

NIR fluorescence is observed for the doubly fused pyrenyl

derivatives, in marked contrast to poor luminescent efficiency

seen in most known porphyrinoids, including porphyrin tapes.¹

Finally, we report the use of doubly fused porphyrins as NIR-

absorbing donor components in organic photovoltaic cells with

higher photovoltaic efficiencies compared to other reported

devices that employ π-extended porphyrins.

Scheme 1

as shown by Anderson et al. in the fusion of up to four

anthracene rings to a porphyrin core, leads to porphyrins with

absorption shifted up to 1417 nm and with narrow line widths

(full width at half-maximum (fwhm) = 284 cm⁻¹).^15gSynthesis

of porphyrins with fused PAH groups requires activation of the

porphyrin by metalation with nickel(II) and/or activation of

the singly connected aromatic rings with bulky electron

donating alkoxy, aryloxy or amino groups.^15h,16fZinc metalated

monoporphyrins with unsubstituted aromatic rings at meso

positions have previously failed to give fused products.^15a,d

Unfortunately, metalation of porphyrins with nickel(II) causes

fast deactivation of the porphyrin excited states through low-

lying metal-based d-d states¹⁸limiting their application in a

range of optoelectronic and photovoltaic applications.^15j,19In

addition, demetalation of nickel porphyrins with extended

conjugation often leads to extensive decomposition,^15h,16eor

low yields of the demetalated free-base product.^15cFor these

reasons we have sought synthetic approaches to β,meso fused

porphyrin systems that require neither nickel metalation nor

donor groups on the aromatic moiety to activate the system

for fusion.

Development of routes to soluble graphene-like porphyrins

may improve some of the material properties important in

OPVs. Increasing the size of fused aromatic rings increases the

relative ratio of C−C versus C−H bonds, which may impact

the intermolecular interactions of the compounds in the solid

state. The preference for the common herringbone packing

decreases in favor of a π-stacking motif in crystal structures

having a lower relative number of C−H contacts.²⁰Using

noncovalent π−π interactions between aromatic systems is

beneficial for optoelectronic devices. Intermolecular charge

transport in this case is expected to take place by a band-like,

rather than hopping mechanism,²¹increasing charge carrier

mobility and potentially giving improved exciton diffusion

lengths in the film.²²Depending on the spatial orientation of

molecules with such a π−π overlap, significant line broadening

and bathochromic shifts of the thin film absorption is also

expected.²³The presence of bulky groups is necessary for

solubilizing previously reported β,meso fused porphyrins, but is

deleterious to other materials properties such as efficient charge

carrier transport²¹since the bulky group prevents π−π overlap

between molecules.^15e,g,21a

RESULTS AND DISCUSSION

■

Synthesis. The starting building block for our fused PAH

porphyrin synthesis is a 5,15-unsubstituted porphyrin with two

meso positions open for PAH functionalization. This building

block was obtained in relatively large quantities (>30 g) using

methods well-developed by Lindsey et al., starting from

dipyrromethane and 3,5-di-tert-butyl-benzaldehyde (Scheme 2).²⁵

Functionalization of meso-H positions of the porphyrins was

achieved by bromination with 1 equiv of N-bromosuccinimide

(NBS) per meso position (Scheme 2).²⁴Suzuki coupling

reactions of the dibromoporphyrin and pinacol boronate esters

of PAHs were accomplished by the use of Pd(PPh₃)₄/Cs₂CO₃

in toluene (Scheme 2). Yields of the bis-substituted derivatives

1−4 varied from up to 90% for bis-pyrenyl derivative 2 to 30−

40% for bis-perylenyl porphyrin 3. Preparation of pyrenyl

porphyrin 2 is scalable to several grams with easy purification

by crystallization. Both naphthyl (1) and pyrenyl (2)

derivatives have good solubility in organic solvents (e.g.,

toluene, dichloromethane), whereas the solubility of the

perylenyl (3) and coronenyl (4) derivatives is more limited.

Tetrakis-pyrenyl porphyrin 5 was obtained in 30−45% yield by

formation of the bis-pyrenyl porphyrin using commercially

available pyrenecarboxaldehyde, followed by subsequent

bromination of the remaining meso positions with NBS (2 equiv)

and coupling with pyrenyl pinacol boronate ester (Scheme 3).

Porphyrin 5 can also be obtained by direct condensation of

pyrenecarboxaldehyde and pyrrole, albeit in lower yields than

from the bis-pyrenyl-porphyrinic precursor.²⁶The boronate

ester of coronene has not previously been reported and was

obtained in this study by bromination of coronene with 2−3

equiv Br₂(affording an insoluble mixture of bromocoronenes),

followed by borylation using HB(pin) under standard

conditions and purification by column chromatography. The

coronene ring has properties of extended aromatic [18]-

annulenes (chemical shift in ¹H NMR spectra, calculated

magnetic susceptibilities) due to electronic delocalization of the

outer 18-membered ring.²⁷Although the aromaticity of

porphyrin rings is still under debate, most data suggests that

porphyrin can also be described as [18]-annulene.²⁸Thus, bis-

coronenyl derivative 4 provides an unusual example of three

coupled [18]-annulene units. Various metalated bis-pyrenyl

derivatives 2-M (M = Mg, Cu, Pb, Pd or Pt) can also be easily

obtained by demetalation of 2, followed by remetalation with

the corresponding metal salts (Scheme 4).

Here we present a new method for β,meso fusion (Scheme 1)

of Zn porphyrins using direct thermal cyclodehydrogenation to

effect C−H activation of meso-bound aromatic rings in a single

step. We have investigated π-extension through β,meso fusion

with such representative PAHs as naphthalene, pyrene,

perylene and coronene via a preparative route that can be

extended to any number of molecular graphenes. Such β,meso

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Scheme 2

Scheme 3

Scheme 4

linked PAHs can be achieved via the Scholl reaction if the

appropriate oxidant is used in conjunction with aromatic rings

that are activated by electron-donating substituents.²⁹The

corresponding β,meso,β fusion of two or more porphyrins by

Osuka et al. to form triply linked porphyrin tapes has been

carried out using related oxidative fusion conditions.¹²There

are only a few reports of the direct fusion of an unactivated

aromatic group to a porphyrin core, all of which involve

nickel(II)-based porphyrins.^15b,c,hIn most cases, activation of

an aromatic ring by substitution with donor alkoxy or amino

groups is required^15a,d−gin addition to metalation of the

porphyrin ring with nickel(II).^{15a−c,e,g,h}The use of bulky donor

substituents on the aromatic ring and the presence of nickel(II)

significantly limits the scope of such reactions and is

undesirable for applications in photovoltaics.¹⁹Unfortunately,

the use of zinc(II)−metalated porphyrins and unactivated

aromatic rings fails to give any fusion products under oxidative

Scholl-type conditions.^15a,d

The key step in the synthesis of fused porphyrins is a C−C

fusion reaction of a meso-bound polycyclic aromatic ring to the

β position of the porphyrin core. The fusion of covalently

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Figure 1. Scheme representing the products of the Scholl fusion reaction for 3 (top) and the success of polycyclic aromatic ring fusion to a porphyrin

core by the Scholl reaction and under thermal conditions as a function of first oxidation potential of the aromatic ring (E^ox,1) versus Fc⁺/Fc. A + sign

indicates that the fusion reaction proceeds under the given conditions and a − sign indicates that no fused product was observed.

Previously, we reported the first example of fusion of

unactivated pyrene rings to a porphyrin dimer metalated with

zinc(II).¹⁷For this particular compound, the reaction is most

likely favored by the low oxidation potential of the porphyrin

dimer,¹²since the reaction cannot be extended to derivatives

with a monoporphyrin core. Only the perylene rings in por-

phyrin 3 leads to a PAH fused porphyrin when 1−4 are treated

to Scholl-type oxidative reaction conditions (FeCl₃/CH₂Cl₂)

used for the fusion of unactivated pyrene rings to a porphyrin

dimer (Figure 1).¹⁷Porphyrin 3 also undergoes demetalation

during the oxidation process, so treatment with Zn(OAc)₂is

required to obtain the Zn(II) doubly fused porphyrin. This

reaction gives an overall yield of 65−75%, affording a mixture

of syn and anti regioisomeric porphyrins 3d in a ca. 0.7:1 ratio

(Figure 1). A number of reaction conditions have been used to

attempt β,meso fusion of 2, including FeCl₃,^15,17FeCl₃/

AgOTf,^15d,eSc(OTf)₃/DDQ,^15a,d−fPhI(OTf)₂/BF₃OEt₂,^15a

(p-BrPh)₃NSbCl₆,^12aand K/Na,^15ahowever, none of these

methods led to fused products.

The propensity for the aromatic ring to undergo β-fusion

with the porphyrin using FeCl₃can be correlated with the

oxidation potential of the particular PAH. Perylene has the

lowest oxidation potential among studied PAHs (0.61 V),³⁰

while the other extended aromatic systems studied here have

higher oxidation potentials (≥0.89 V) (all potentials referenced

to the ferrocenium/ferrocene couple).³⁰For comparison, the

oxidation potential of porphyrin 2 is 0.41 V. Thus, the ability of

PAHs to fuse onto a porphyrin core in the Scholl reaction

appears to depend on the oxidation potential of the aromatic

groups, with the upper limit lying between the oxidation

potential of perylene and pyrene rings. Alkoxy or amino

activating groups act to lower the oxidation potentials of meso-

aromatic groups and make them amenable to Scholl-type fusion

reactions. The previous known example of fusion of a single

perylene ring to a porphyrin core required the presence of an

activating amino functionality,^15fwhile our data demonstrates

that fusion of two unsubstituted perylene rings can occur

without the need of such an activating group.

has been extensively studied as an efficient means to directly

prepare polycyclic aromatics without the use of added reagents

and solvents,³¹but such high temperature C−C bond forming

reactions have not been studied in porphyrin chemistry.

Porphyrins are thermally stable and relatively inert compounds;

for example, 2 can be sublimed without decomposition at 430 °C

in vacuum (10⁻⁵Torr). However, when sublimation is

suppressed under an atmosphere of nitrogen, 2 undergoes

thermal ring closure at elevated temperatures (500−530 °C) to

afford singly (2m) or doubly fused (2d) porphyrins (Scheme 5).

The product ratio (2m:2d) and reaction yield can be controlled

by varying the reaction time. This reaction has also proven to

be scalable, in excess of several grams, albeit with lower yields of

2d (25−35%) and 2m (7%). The major side product in large-

scale reactions, comprising 35−40% of the porphyrinic material,

involves the loss of either one or both of the di-tert-butylphenyl

groups from 2d depending on the reaction time. While the loss

of the di-tert-butylphenyl group(s) reduces the yields of 2d, the

optical properties of the fused compounds are unaffected (see

experimental part). To ensure that cyclodehydrogenation is not

caused by the remaining impurities of palladium catalysts from

the previous steps, a sample of 2 was extensively purified by

column chromatography, crystallization and sublimation. The

resultant high purity material undergoes thermal fusion under

the same reaction conditions as the porphyrin purified by

standard methods. Similarly, all of the attached aromatic rings

can be fused in tetrakis(pyrenyl)porphyrin 5 to form the

quadruply fused product 5t as illustrated in Scheme 5, where

only two isomers of the four possible isomers of 5t are shown.

Thermal reactions in thin films of precursor materials have

shown promise for scalable, efficient and inexpensive routes to

electronic applications since it eliminates many preparation

steps.³²Usually, this is achieved by converting solution

processable small molecule to insoluble organic semiconductor

materials by thermal removal of leaving groups after fabrication

of the film. This approach favors a face-to-face orientation of

π-conjugated molecules, especially in such PAHs as the acenes,

preventing formation of herringbone structures with undesired

edge-to-face orientation. In practice, such reactions must be

reliable, furnish high yields of the desired products, and proceed

in the absence of external reagents and solvents. A good

Thermal activation of two or more C−H bonds in aromatic

systems for direct C−C bond formation is known to proceed

under the conditions of flash vacuum pyrolysis.³¹This reaction

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Scheme 5

Figure 2. In situ fusion of porphyrin 2. Film of compound 2 (500 Å) spin-cast on ITO from toluene solution and the same films after thermal

annealing at 530 °C for 5 min.

example of such a process is the thermally promoted retro

Diels−Alder reaction of soluble β,β-substituted porphyrin

precursors to form an insoluble thin film of pure β,β-

benzannulated tetrabenzopophyrin and four equivalents of

ethylene gas.³³This process was applied to thin film OPVs with

various architectures.³²Thermal cyclodehydrogenation of

porphyrins substituted with meso-bound polycyclic aromatic

rings represents a new approach for in situ preparation of

materials that show good spectral coverage for applications

where absorption in the NIR region is required, such as for

OPVs and nonlinear optics.⁹Thermally annealing thin films or

small amounts (50−100 mg) of 2 leads to complete conversion

of the strong Soret band of the singly connected precursor into

absorption peaks corresponding to only the doubly fused-

products. Since the thermal fusion reaction proceeds in thin

film form as it does in the bulk, the process is potentially

suitable for in situ formation of graphene-like porphyrins on

substrates (e.g indium−tin oxide) for applications in organic

electronics (Figure 2). The formation of 2d in the film can be

monitored by the growth of a strong absorption band with

λ_max= 860 nm that is a signature of the fused product (vide infra).

Thin films of 5t were also obtained using a similar approach

(Supporting Information). While this method can cleanly afford

fused porphyrins, the resulting films have nanoscale pin-holes

making them poor candidates for electronic devices. Further

optimization of the conditions for thermal annealing as well as

choice of the appropriate substrate may lead to pin-hole-free

films.

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The thermal cyclodehydrogenation reaction is not limited to

porphyrins appended with meso-pyrenyl groups. Fusion can also

be accomplished for meso-naphthalene and meso-coronenyl

groups giving the doubly fused products 1d and 4d (Scheme 5),

although yields are lower (10−13%) than for 2d, due to losses

during chromatographic separation and the formation of side

products with the loss of di-tert-butyl-phenyl groups similar to

those obtained in the thermal reaction of 2. This data suggests

that a thermal reaction should be possible for fusion of other

PAHs to the porphyrin core as well.

consistent with the fact that this compound requires a higher level

of laser power to volatilize the compound than any of the other

compounds reported here. The higher laser power is needed to

overcome the cohesive forces in the films of 4d due to strong

intermolecular π−π interactions between the pendent coronenes.

An important criterion in the design of appropriate

candidates for thin film applications such as OPVs is the ease

of processing (either by vacuum or solution deposition). Both

¹H NMR data and molecular modeling (Figure 3; Supporting

The other metalated pyrene porphyrins 2-M undergo similar

fusion (Scheme 6), forming 2d-M, (M = Mg, Cu, Pd, Pt),

except for 2-Pb, which leads to demetalated fused product.

Scheme 6

Figure 3. Structures of model porphyrins anti-2d′ and syn-2d′

calculated at B3LYP/6-31G*/LANL2DZ level.

Information) suggest an out-of-plane distortion occurs in the

β,meso fused porphyrins due to unfavorable interactions between

α protons of the fused polycyclic aromatic ring and neighboring

β-pyrrolic protons of the porphyrin rings (Figure 3). Such a

structural distortion is known to improve solubility and

processability in conjugated aromatics.³⁴As a result, all fused

porphyrins studied here are readily soluble in common organic

solvents (benzene, toluene, etc.) and have high solubility in

nonpolar solvents such as cyclohexane (ca. 1 mg/mL for 2d).

Even quadruply fused porphyrin 5t is sufficiently soluble for

NMR characterization. Bis-coronenyl fused porphyrin 4d has

the lowest solubility and the tendency to aggregate in solutions

is similar to that of previously studied nondistorted porphyrin

tapes.¹²Such high solubility is atypical for extensively fused

aromatic compounds, even when appended with multiple

solubilizing groups.^12,15

Characterization. The nonfused porphyrin precursors

(1−4 and 2-M) and fused products (1d−4d, 2m, 5t and 2d-M)

were characterized using mass and NMR spectroscopy. The

formation of ring fusion products is supported by the mass

spectral data. For example, 2 gives a mass for the parent ion of

1149.4834 Da (MH⁺), a loss of two hydrogens for 2m ([M]⁺=

1146.4581 Da), and a loss of four hydrogens for 2d ([M]⁺=

1144.4418 Da). Porphyrin 5 ([MH]⁺= 1173.2915 Da) shows a

loss of eight hydrogens for 5t ([M]⁺= 1164.32 Da) after

thermal fusion. MALDI-TOF mass spectra of porphyrins 2m,

2d and 3d obtained for samples without use of any matrices

show the formation of molecular ions without significant

fragmentation in the 20−5000 Da range indicating stability of

the obtained fused porphyrins toward laser irradiation. The

mass spectrum for fused porphyrin 4d contains peaks of the

molecular ion together with fragmentation products indicating

the presence of fused products with the loss of one or both di-

tert-butyl-phenyl groups. Both thermal (for 1−4) and Scholl-

type (for 3) oxidative fusion leads to mixtures of syn and anti

regioisomers. Regioisomers of doubly fused pyrenyl porphyrins

anti-2d and syn-2d (1:1 ratio) can be separated using column

chromatography. The regioisomers were structurally assigned

using NMR spectroscopy on the basis of the number of

equivalent di-tert-butylphenyl (Ar) groups. Regioisomer anti-2d

has equivalent Ar groups (only one set of signals in NMR

spectra), whereas the compound with inequivalent Ar groups

(two independent sets of signals) is assigned to the syn-2d

regioisomer. The size of π-system of porphyrin 4d is close to

that of the previously reported triply linked porphyrin trimers,

Electrochemical and Theoretical Characterization. The

electrochemical properties of zinc porphyrins 2, 2m and 2d

(syn/anti mixture) were analyzed using cyclic voltammetry

(Table 1). Consistent with previous data,¹⁵the fused

Table 1. Electrochemical Potentials and Energy Levels³⁵for

the HOMO and LUMO Energies of Pyrene-functionalized

a

Porphyrins 2, 2m and 2d

compound

E^ox

E^red

ΔE^ox‑red

E^HOMO

E^LUMO

2

0.41

0.18

0.01

−1.92

−1.52

−1.44

2.33

1.70

1.45

5.2

4.8

4.6

2.5

3.0

3.1

2m

2d

a

Potentials were determined by cyclic voltammetry referenced to an

internal ferrocenium/ferrocene potential. Each compound shows two

oxidations and two reductions, but only the first oxidation and

reduction values are listed.

which give extensive aggregation in solution.¹²The H NMR

1

porphyrins show a significant decrease in the separation

between E^oxand E^redpotentials (ΔE^ox‑red). Compounds 2, 2m

and 2d give ΔE^ox‑redvalues of 2.33, 1.70, and 1.45 V,

respectively. The highest occupied (HOMO) and lowest

unoccupied molecular orbital (LUMO) energy levels relative

to vacuum for pyrenyl porphyrins 2, 2m, 2d can be estimated

spectra of porphyrin 4d contain only broad signals due to aggre-

gation in solution, making its use for structural assignment im-

possible. The MALDI-TOF mass spectrum shows the parent ion

as the base peak and subsequent peaks for loss of methyls from the

di-tert-butyl-phenyl groups. Compound 4d gives a higher level of

fragmentation in its mass spectrum than other fused porphyrins,

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from these electrochemical redox potentials, and are listed in

Table 1.³⁵

transitions observed in fluid solution (vide infra). In particular,

coronenyl derivative 4d′ has a larger energy gap compared with

both 2d′ and 3d′ porphyrins. These calculations predict a

progressive decrease in the HOMO−LUMO gap upon further

increase in the size of the fused polycyclic aromatic, up to 16

condensed benzene units of the fused polycycle (see

Supporting Information).

Theoretical calculations (B3LYP/6-31G*/LANL2DZ) per-

formed on the model pyrenyl porphyrins without the di-tert-

butylphenyl groups (2′, 2 m′, syn-2d′ and anti-2d′) also predict

a decrease in the HOMO−LUMO gap (ΔE_HL) with increasing

degree of fusion. The calculated HOMO−LUMO gap for 2′

(ΔE_HL= 2.93 eV) decreases upon monofusion (2 m′, ΔE_HL

2.19 eV), declines further upon double fusion (syn-2d′, ΔE_HL

=

Electronic Spectroscopy. The absorption spectra for

nonfused and fused porphyrins in solution are shown in

Figures 6a−d, data are listed in the Experimental Section. The

Soret bands in the parent porphyrins 1, 2 and 4 appear as intense

peaks at λ_max= 430 nm (Figure 6a) with the Soret band of 4 split

by 5 nm. Coronene itself has a relatively weak S₀−S₁transition at

420 nm that is forbidden due to the D_6hsymmetry of a coronene

core.²⁷However, the lower symmetry of the coronene π-system in

4 causes this transition to be partially allowed. Compound 3

displays broad absorption bands centered at 425 and 460 nm,

consistent with the Soret band and perylene π−π* transitions.

Upon pyrene ring fusion, the Soret bands in porphyrins 2m,

2d and 5t undergo red-shifts to λ_max= 490, 500−540, and 620

nm, respectively. The Soret bands in 2d and 5t also display

peak splitting and broadening. Significant spectral changes are

also observed for the Q bands (Figure 6b). The increased

conjugation in porphyrins 2m, syn-2d, anti-2d, and 5t results in

large bathochromic shifts of the Q-band to λ_max= 706, 811, 815,

and 890 nm, respectively, from λ_max= 551 nm in 2. Thus, the

overall effect of multiple pyrene ring fusion in 5t is a red shift

of ca. 400−450 nm relative to 2 and 5. Fusion with multiple pyrene

rings also causes significant enhancement in the intensity of the

Q-band relative to 2 (ca. 4 times in 2d). Increased π-conjugation

in perylenyl-fused porphyrin 3d causes the Q-band to red-shift

further up to λ_max= 900 nm (Figure 6d). The absorption

maximum of the Q-band in the various metalloporphyrins

2d-M covers a significant portion of the NIR region, and

undergoes a progressive blue-shift from λ_max= 830 nm for

2d-Mg to 740 nm for 2d-Pt (Figure 6e).

1.77; anti-2d′, ΔE_HL= 1.73 eV), and the values are consistent

with the redox gaps determined electrochemically for 2, 2m and

2d. As can be seen in a qualitative frontier molecular orbital

diagram (Figure 4), the HOMO of the fused pyrenyl porphyrin

Figure 4. Qualitative frontier molecular orbital diagram of fused porphyrin

anti-2d′ as derived by B3LYP/6-31G*/LANL2DZ calculation.

Among the doubly fused compounds reported here, the

coronenyl-fused porphyrin 4d has the largest degree of π-

extension, however, its absorption peak at 780 nm is significantly

blue-shifted relative to the perylenyl porphyrin 3d and also pyrenyl

derivative 2d (Figure 6d). The degree of orbital overlap between

the PAH and the porphyrin core as well as the symmetries of the

PAH orbitals in contact with the porphyrin core are the same for

1d−4d. The ordering of the absorption band energies of the four

fused porphyrin materials (i.e., 1d−4d) appears to be related to

the energies of the HOMO and LUMO orbitals of the PAH

relative to those of the porphyrin core. Compound 2 is a good

model for the porphyrin core frontier orbital energies, E^ox= 0.41 V

and E^red= −1.92 V versus ferrocene; see Table 1. The oxidation

and reduction potentials of the PAHs are given in Table 2 along

with the energies of the Q bands for 1d−4d. It is anticipated that

PAHs with a frontier orbitals that lie closer in energy to those of

the porphyrin core will undergo a greater degree of orbital mixing

and thus destabilization for the HOMO and stabilization for

LUMO in the fused porphyrin and will also display a larger

bathochromic shift. Indeed, this is observed for 1d−4d.

Porphyrin 3d has the best energy match for the porphyrin

core and PAH frontier orbitals, and thus, the lowest energy Q-

band. The energies of the frontier orbitals of coronene fall

between those of naphthalene and perylene, and thus the

energy of the Q-band in 4d falls between 1d and 3d.

consists of an out-of-phase combination of the corresponding

HOMOs of pyrene and unsubstituted porphyrin rings, whereas

the LUMO of the fused porphyrin is comprised of an in-phase

combination of the corresponding LUMOs of the pyrene and

porphyrin rings. This arrangement in the fused porphyrins

leads to destabilization of the HOMO, stabilization of the

LUMO, and a net decrease in the HOMO−LUMO gap.

AM1 method was used to calculate the structures and

energies of model Zn porphyrins doubly fused with PAHs

(Figure 5). The predicted HOMO−LUMO gaps for naphthyl

Figure 5. Energy diagram showing the LUMO and HOMO orbitals of

different model Zn fused porphyrins calculated at the AM1 method.

Structures of model porphyrins used for geometry optimizations have

phenyl groups in place of the 3,5-di-tert-butylphenyl groups of 1d−4d,

and are abbreviated 1d′−4d′.

1d′, pyrenyl 2d′, perylenyl 3d′ and coronenyl 4d′ model

porphyrins are consistent with the lowest-energy electronic

The relative intensities of the Soret and Q bands for the

β,meso-fused porphyrins 1d−4d appear to depend on the

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Figure 6. UV−vis absorption spectra of CH₂Cl₂solutions of (a) porphyrins with meso-bound polycyclic aromatic rings 1−4; (b) fused pyrenyl-

porphyrins 2m, anti-2d, syn-2d, and 5t with 5% added pyridine; (c) metalated bis-pyrenyl-porphyrins 2-M; (d) doubly fused porphyrins 1d−3d, and

4d with 5% added pyridine; (e) metalated doubly fused pyrenyl porphyrins 2d, Mg-2d, dissolved directly after fusion at 530 °C and Cu-2d, Pd-2d,

Pt-2d dissolved directly after fusion at 560 °C; (f) Absorption spectra of porphyrin 2 and fused porphyrins 2m, 2d and 3d in spin-cast thin films.

difference in energies between the HOMO of the porphyrin

ring and that of the respective PAHs. A close match between

frontier orbital energies of the porphyrin and fused PAH give

rise to Soret: Q-band intensities that approach 1:1 (Table 2).

The intensity ratio of the Soret: Q-band for the aryl porphyrins

is 17:1 for 2, drops to 4:1 for the naphthyl fused porphyrin 1d,

and further to 1.1:1 for 3d. Having Soret and Q bands of similar

intensity is beneficial in designing OPVs or optical detectors,

since this will give similar absorbance for both bands at any

given film thickness.

The absorption spectra for neat thin films of 2, 2m, 2d and

3d are shown in Figure 6f. The π-systems of the fused

polycyclic aromatic moieties of the β,meso-fused porphyrins are

not sterically hindered, making them accessible for π−π

interactions.^14,36These π−π interactions lead to significantly

red-shifted absorptions in thin films of the fused porphyrins

relative to their solution spectra (e.g., for the Q-band, the red

shift is 85 nm for 2d and 70 nm for 3d). The bathochromic

shift for the fused porphyrin 2d is markedly larger (0.144 eV)

than the shifts observed for thin films of unfused porphyrin 2

(0.024 eV), and also larger than for neat films of the previously

reported pyrene-fused porphyrin dimer (0.078 eV).¹⁷This

Table 2. Photophysical Data for Porphyrins 1d−4d and 2

and Electrochemical Data for Their Respective Polycyclic

a

Aromatic Hydrocarbons (PAH)

compound

2

1d

4d

2d

3d

Q-band

wavelength (nm)

550 730

780

815

900

Soret: Q-band

intensity

17:1 4:1

2.8:1

1.6:1

1.1:1

E^ox/E^redof PAH³⁰

1.35/−2.99 0.92/−2.53 0.89/−2.53 0.61/−2.14

a

Electrochemical values are referenced to an internal ferrocenium/

ferrocene couple in 0.1 M Bu₄NPF₆in dichloromethane.

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bathochromic shift becomes more pronounced with increasing

degree of fusion for a given PAH, for example, comparing the

Q-band shifts of unfused porphyrn 2 (0.024 eV), to monofused

2m (0.053 eV), to doubly fused 2d (0.144 eV). This large

bathochromic shift pushes absorption bands further into NIR

than the π-extension alone, by utilizing π−π interactions

between fused PAHs with unhindered π-system. These shifts

are also larger than what is observed in films of β,β annulated

tetrabenzo- and tetranaphthoporphyrins PtTPBP (0.039 eV)

and PtTPNP (0.041 eV) (Scheme 7).

offsets between 2d and fullerene C₆₀provide sufficient driving

force for exciton separation for 2d to act as donor material in

an OPV using a C₆₀acceptor layer (Figure 8b, inset). Thus,

Scheme 7

Porphyrins 2, 2m, 2d exhibit room temperature emission that

undergoes red-shift with extending conjugation from 596 nm for

2 to 721, 829, and 839 nm for 2m, syn-2d and anti-2d,

respectively (Figure 7). The fluorescence quantum efficiencies

Figure 7. Fluorescence spectra of 2, 2m, anti-2d and syn-2d in CH₂Cl₂

at room temperature.

Figure 8. (a) I−V characteristics and performance metrics of ITO/

donor/C₆₀(400 Å)/BCP(100 Å)/Al (1000 Å): donor layer =

porphyrin 2d (100 Å, red line, filled circles) and CuPc (400 Å, blue

line, open circles); BCP = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthro-

line, CuPc = copper phthalocyanine. (b) External quantum efficiency

(EQE) as a function of wavelength for photovoltaic cells using

porphyrin 2d (red, filled circle) and CuPc (blue, open circle) donors.

(Inset) Energy levels of 2d and CuPc versus energy levels of fullerene

as an acceptor. Energy levels for fullerene taken from ref 3a. HOMO

level for 2d calculated from electrochemical oxidation potentials.³⁵

(Φ_f) increase from 3.3% for the starting nonfused porphyrin 2,

to 8% for the monofused porphyrin 2m, to 8 and 13% for the

doubly fused porphyrins anti-2d and syn-2d, respectively. This

behavior is in contrast to what is expected from the energy gap

law, which states that the nonradiative deactivation rate

increases for related molecules as the S₀−S₁energy gap

decreases.³⁷Such unexpected behavior may be due to the

hindrance of vibrational deactivation modes by ring fusion.

Many twisted acenes are known to exhibit strong fluorescence,^34b

suggesting that the distortion in fused porphyrins may also

contribute to the increased fluorescence efficiency. The

fluorescence efficiencies are comparable to those of the most

efficient NIR-fluorescent porphyrin oligomers^11fIn contrast,

closely related porphyrin tapes or directly linked β,meso-

porphyrins have very low fluorescent efficiencies in the NIR

(Φ_f= 10⁻⁵)^12ddue to very short S₁excited state lifetimes.^12d,13

OPV Devices using 2d. Porphyrins have been shown to

act as donor and hole transporting materials in heterojunction

OPVs.²Taking into account the energies and intensities of the

absorption bands along with ease of synthesis, the doubly fused

pyrenyl porphyrin 2d was chosen as the best candidate for our

initial OPV studies. The HOMO and LUMO of 2d (Table 1)

lie ca. 1.6 and 0.4 eV above the respective values of the fullerene

acceptor C₆₀(E_HOMO= 6.2 eV, E_LUMO= 3.5 eV).^3aThe energy

solar cells incorporating 2d were fabricated using a structure:

ITO/2d(100 Å)/C₆₀(400 Å)/BCP(100 Å)/Al(1000 Å), similar

to that used for a copper phthalocyanine (CuPc)/C₆₀reference

cell and related porphyrin based cells.^3a,bThe current density

versus voltage (J−V) characteristics were measured in the dark

(dashed lines) and under simulated 1 sun (1 kW/m²) AM1.5G

illumination (circles).³⁸Efficiencies were determined after

correction for spectral mismatch between the xenon source

lamp and ASTM G173−03 global.³⁹Overall, thin layers (100 Å)

of thermally evaporated porphyrin 2d yield a power conversion

efficiency (PCE = 1.04%), which is close to that of the

reference (CuPc, 400 Å/C₆₀) device (PCE = 1.08%).

Surprisingly, even though the ΔE_DAvalues suggest the OPVs

based on 2d should give a lower open circuit voltage (V_oc) than

those with a CuPc donor, the open circuit voltage of porphyrin

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4,4,5,5-tetramethyl-2-(coronen-1-yl)-1,3,2-dioxaborolane were ob-

tained from the corresponding bromides and pinacolborane (Method

A, vide infra). Moisture or air sensitive reactions were performed under

an inert atmosphere of nitrogen. Flash chromatography was carried

out with silica gel (60−200 mesh) and alumina (neutral, activity grade

I). ¹H NMR spectra were measured at either 400 or 600 MHz and are

reported with chemical shifts as the delta scale in ppm relative to the

residual nondeuterated solvent CHCl₃(δ 7.26 ppm) or C₆H₆(δ 7.15

ppm). Coupling constants (J) are given in Hz. ¹³C NMR spectra were

proton wide-band decoupled and chemical shifts were reported as the

delta scale in ppm relative to CHCl₃(δ 77.0 ppm) or C₆D₆(δ 128.02

ppm). MALDI-TOF mass spectra were recorded using a positive-

MALDI-TOF method with/without α-cyano-4-hydroxycinnamic acid

(CHCA) matrix. All spectra were measured as solutions in the

indicated solvents at room temperature using a 1 cm cell. Absorption

maxima (λ_max) are reported in nm and extinction coefficients (ε) in

M⁻¹cm⁻¹. Quantum efficiency measurements were carried out using a

system equipped with a xenon lamp, calibrated integrating sphere and

photonic multichannel analyzer. Redox potentials were measured by

the cyclic voltammetry method and differential pulse voltammetry

method. 0.1 M n-Bu₄NPF₆in CH₂Cl₂was used as the supporting

electrolyte (degassed with nitrogen), a Pt wire was employed as the

counter electrode, an Ag wire used as the pseudoreference electrode

and a glassy carbon electrode was used as the working electrode.

Ferrocene (Fc) or decamethylferrocene (dmfc) was added as an

internal reference, and the potentials were measured relative to the

Fc/Fc⁺couple. CV was used to determine electrochemical reversibility,

while all redox potentials were found using DPV.

2d/C₆₀based OPV (V_oc= 0.42 V) and CuPc/C₆₀based OPV

(V_oc= 0.43 V) are very close. Studies of OPVs with the other

fused-PAH porphyrins reported here are beyond the scope of

this paper and will be reported elsewhere.

CONCLUSIONS

■

Functionalization of the meso positions of porphyrins with

polycyclic aromatic rings can be accomplished in relatively large

scale by Suzuki coupling starting from available building blocks.

Fusion of the resulting porphyrins using Scholl-type oxidative

conditions has been extensively studied for further ring closure

of the aromatic systems to the porphyrin core. Prior literature

examples of such fusion to a monoporphyrin core require either

substitution of PAHs with donor alkoxy or amino- groups or

metalation of porphyrins with nickel. Here we demonstrate that

neither donor groups at PAHs nor metalation with nickel is

needed to for the formation of porphyrins β,meso-fused with

PAHs. To overcome limitations of the Scholl reaction in fusing

unactivated aromatic rings, a new thermal method has been

developed. We have shown that β,meso-fusion of aromatic

groups at one, two or all four meso positions of a porphyrin core

can be accomplished using a thermal ring-closure reaction. For

pyrenyl-substituted porphyrins thermal method gives syntheti-

cally acceptable yields of fused porphyrins (>30%). Further

optimization of thermal conditions by surface assisted cyclo-

dehydrogenation can potentially lead to higher yields of fused

porphyrins. This fusion reaction does not require activation of

the porphyrins using an appropriate metal or an aromatic group

with donor substituents and has significant potential for further

development of high-temperature reactions involving porphyr-

ins and potentially other porphyrinoid macrocycles.

[5,15-Bis-(3,5-di-tert-butylphenyl)porphyrinato(2-)]zinc(II).⁴⁰Tri-

fluoroacetic acid (3 mL) was added to a stirred solution of 3,5-di-tert-

butylbenzaldehyde (8.72 g, 39.8 mmol) and dipyrromethane (5.85 g,

39.8 mmol) in dichloromethane (5 L) under nitrogen atmosphere and

the reaction mixture was stirred at ambient temperature for 3 h. After

that, DDQ (13.4 g, 60.4 mmol) was added and stirring continued for

additional 30 min. The reaction mixture was quenched with

triethylamine (15 mL) and passed through filter (2 L) filled with

silica gel (800 g) washing with dichloromethane. All purple fractions

were collected, dichloromethane was evaporated to a volume of

500 mL. To this solution of the corresponding free-base porphyrin,

30 mL of saturated solution of zinc(II) acetate in methanol was added

and the resulting mixture was stirred for 3 h at ambient temperature.

The reaction mixture was washed with water, and dichloromethane

solution was passed through filter filled with silica gel (200 g) washing

with dichloromethane. The residue after evaporation of solvents was

crystallized from dichloromethane by adding methanol to give [5,15-

bis-(3,5-di-tert-butylphenyl)porphyrinato(2-)]zinc(II) (7.46 g, 9.95

mmol, 50%). Characterization is given in reference 40.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-naphthyl)-

porphyrinato(2-)]zinc(II) 1. (A) NBS (5 g, 28 mmol, 2.1 equiv.)

was added to a stirred solution of [5,15-bis-(3,5-di-tert-butylphenyl)-

porphyrinato(2-)]zinc(II) (10 g, 13.33 mmol) in dichloromethane (700 mL)

and pyridine (20 mL) at −10 °C (NaCl/ice bath) under nitrogen

atmosphere. The reaction mixture was stirred at the same temperature for

10 min, after that allowed to warm to 0 °C (ca. 5 min, water bath) and then

quenched with acetone (20 mL). The crude reaction mixture was passed

through short silica gel column, eluting with dichloromethane−pyridine

mixture (100:1). All green-purple fractions were collected, the solvents

were evaporated, the residue was dissolved in dichloromethane−pyridine

mixture (95:5, 100 mL) and 200 mL of methanol was added to precipitate

bromoporphyrin. All crystals were collected by filtration after 30 min to give

[10,20-bis-(3,5-di-tert-butylphenyl)-5,15-bis-bromo-porphyrinato(2-)]zinc-

(II)^11e,24a(10.5 g, 11.6 mmol, 87%).

Porphyrin 2d has a high extinction and emits with a quantum

efficiency of 13% within biological window. All of the fused

porphyrins reported exhibit enhanced solubility relative to their

nonfused precursors, making them promising for organic

electronics applications. The π-systems of the fused polycyclic

aromatic moieties of the β,meso-fused porphyrins are not

sterically hindered, allowing for accessibility to π−π interactions

with a large bathochromic shift of the Q-band up to 0.144 eV

for 2d. Based on a number of material criteria, pyrene porphyrin

2d was chosen for use in OPVs. Devices incorporating 2d as a

donor show high EQE response in the NIR (up to 950 nm),

resulting in high J_SC, while having open-circuit voltages com-

parable to that of analogous CuPc devices. Our results suggest

that these systems will be of broad interest as NIR dyes for

organic photovoltaic devices, two-photon absorption, nonlinear

optics, bioimaging and photodynamic therapy.

EXPERIMENTAL SECTION

■

1. General. All reagents and solvents are commercial reagent grade

and were used without further purification including anhydrous iron(II)

chloride, dry dichloromethane, coronene, perylene, naphthalene-1-

boronic acid, pyrene-1-boronic acid, 1-pyrenecarboxaldehyde. Starting

[5,15-bis-(3,5-di-tert-butylphenyl)porphyrinato(2-)]zinc(II)⁴⁰was pre-

pared from dipyrromethane^25cand 3,5-di-tert-butylbenzaldehyde⁴¹by

known methods. [10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-bromo-

porphyrinato(2-)]zinc(II) was prepared by bromination of [5,15-bis-

(3,5-di-tert-butylphenyl)porphyrinato(2-)]zinc(II) with NBS in 5%-

pyridine/dichloromethane according to literature. Starting 4,4,5,5-

tetramethyl-2-(naphth-1-yl)-1,3,2-dioxaborolane⁴²and 4,4,5,5-tetra-

methyl-2-(pyren-1-yl)-1,3,2-dioxaborolane⁴³were obtained from the

corresponding boronic acids and pinacol (Method B, vide infra).

Starting 4,4,5,5-tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane,⁴³

4,4,5,5-tetramethyl-2-(perylen-1-yl)-1,3,2-dioxaborolane⁴⁵and

(B) A mixture of the above dibromoporphyrin (1.13 g, 1.25 mmol),

cesium carbonate (4.2 g, 12.9 mmol, 11 equiv.), Pd(PPh₃)₄(130 mg,

10 mol %), pyridine (3 mL) and 4,4,5,5-tetramethyl-2-(naphth-1-yl)-

1,3,2-dioxaborolane⁴²(0.73 g, 2.87 mmol, 2.3 equiv) in toluene (200 mL)

was degassed and refluxed under nitrogen for 12 h. Reaction mixture was

cooled and passed consecutively through pads of silica gel and neutral

alumina washing with toluene. Toluene was distilled off in vacuum,

the residue was separated by crystallization from dichloromethane by

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adding methanol to afford [10,20-bis-(3,5-di-tert-butylphenyl)-5,

15-bis-(naphth-1-yl)porphyrinato(2-)]zinc(II) 1 (*MeOH complex,

(5% pyridine-d₅in CDCl₃, 500 MHz): 1.415 and 1.422 (s, 36H), 6.84

(dd, 2H, J¹= 8.5 Hz, J²= 18 Hz), 8.92 (dd, 2H, J¹= 8.5 Hz, J²= 16 Hz),

7.50 (t, 2H, J = 8 Hz), 7.56 (t, 2H, J = 7.5 Hz), 7.60 and 7.67 (t, 2H, J

= 1.5 Hz, atropoisomers), 7.73 (t, 4H, J = 8.5 Hz), 7.93, 8.00, and 8.05

(d, 4H, J = 1.5 Hz, atropoisomers), 8.10−8.12 (m, 2H), 8.22−8.26 (m,

2H), 8.42 (d, 2H, J = 7.5 Hz), 8.51 (d, 2H, J = 7.5 Hz), 8.69 (dd, 4H,

J¹= 2 Hz, J²= 4.5 Hz), 8.80 (d, 4H, J = 4.5 Hz). ¹³C NMR could not be

acquired due to low solubility of 3. UV/vis (CH₂Cl₂) λ, nm, (ε): 257

(53872), 424 (152871), 459 (123061), 552 (23698), 591 (6611).

HRMS: 1248.5001 (M⁺and MH⁺), calcd. 1248.5043 for C₈₈H₇₂N₄Zn.

4,4,5,5-Tetramethyl-2-(coronen-1-yl)-1,3,2-dioxaborolane.

A) Coronene (1.9 g, 6.33 mmol) was dissolved in 600 mL of chloro-

benzene in dark at 70−80 °C. Higher temperature is required to

completely dissolve coronene. Bromine (5.5 g, 34.8 mmol, 5 equiv)

was added at once and the mixture stirred for 5−10 min. After that,

reaction mixture was cooled down and the precipitate was filtered and

washed with chlorobenzene to afford a mixture of bromocoronenes

(2 g). MALDI TOF: bromocoronene, 378.17 (M⁺), requires 378.00

for C₂₄H₁₁Br; dibromocoronene, 456.08 (M⁺), requires 455.91 for

C₂₄H₁₀Br₂. This mixture was used for the next step without further

purification.

B) The mixture of bromocoronenes (2 g) from the previous step,

HB(pin) (6 mL), Cl₂Pd(PPh₃)₂(0.4 g) in toluene (150 mL) and

triethylamine (25 mL) was refluxed overnight, cooled down to room

temperature and the excess of HB(pin) quenched with slow addition

of methanol (2 mL). The residue after evaporation of solvents in

vacuum was subjected to column chromatography on silica gel by

using mixture of dichloromethane−hexanes as eluent. The first

fraction (dichloromethane−hexanes = 1:9) contained 4,4,5,5-tetra-

methyl-2-(coronen-1-yl)-1,3,2-dioxaborolane, the second fraction

(dichloromethane−hexanes = 1:9) contained a mixture of isomeric

bis-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)coronenes.

1

1.08 g, 1.047 mmol, 93%). H NMR (CDCl₃, 500 MHz): 1.52 and

3.05 (s, 36H), 7.11 (t, 2H, J = 7.5 Hz), 7.20 (dd, 2H, J¹= 8.5; J²=

14.5 Hz), 7.49 (t, 2H, J = 7.5 Hz), 7.78 (s, 2H), 7.88 (t, 2H, J = 7.5

Hz), 8.07 and 8.11 (s, 4H, atropoisomers), 8.29 (d, 2H, J = 8.5 Hz),

8.33 (dd, 2H, J¹= 3 Hz, J²= 6 Hz). ¹³C NMR (CDCl₃, 125 MHz): 29.7,

31.7, 35.0, 118.2, 120.7, 122.4, 124.1, 125.5, 126.0, 127.8, 128.3,

128.87, 128.90, 129.6, 129.8, 129.9, 131.7, 132.4, 132.5, 132.6, 132.8,

136.9, 140.3, 141.7, 148.47, 148.49, 148.51, 150.52, 150.7. UV/vis

(CH₂Cl₂) λ, nm, (ε): 308 (8073), 345 (6074), 423 (345474), 511

(1472), 549 (14142), 588 (1595). HRMS: 1000.4419 (M⁺and MH⁺),

calcd. 1000.4417 for C₆₈H₆₄N₄Zn.

4,4,5,5-Tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane.^17,43

(Method A) To a ca. 0.1 M solution of 1-bromopyrene in toluene

10 mol % of Cl₂Pd(PPh₃)₂, 5 equivalents of pinacolborane and 10

equivalents of triethylamine were added. Reaction mixture was degassed

with nitrogen and refluxed overnight. Reaction mixture was quenched

with water, toluene was distilled off and the residue was subjected to

column chromatography on silica gel (gradient elution with hexanes −

ethyl acetate mixtures from 1:0 to 1000:5) to give 70−80% of 4,4,5,5-

tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane. ¹H NMR (CDCl₃, 400

MHz): 1.51 (s, 12H), 8.02 (t, 1H, J = 7.7 Hz), 8.07−8.24 (m, 6H),

8.56 (d, 1H, J = 9.7 Hz), 9.09 (d, 1H, J = 9.7 Hz). MALDI TOF: 328

(M⁺), requires 328.16 for C₂₂H₂₁BO₂.

(Method B). According to reference 44. A mixture of commercially

available 1-pyreneboronic acid (10 g, 40.7 mmol) and pinacol (5.8 g,

49 mmol, 1.2 equiv) in ether (200 mL) and dichloromethane (600

mL) was stirred at ambient temperature for 1 day. Evaporation of

solvents gave crude 4,4,5,5-tetramethyl-2-(pyren-1-yl)-1,3,2-dioxabor-

olane which was used for the next step without further purification.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)]zinc(II).¹⁷2. A mixture of the above dibromopor-

phyrin (6.33 g, 6.98 mmol), cesium carbonate (23.5 g, 70 mmol,

10 equiv.), Pd(PPh₃)₄(800 mg, 10 mol %), pyridine (10 mL) and the

4,4,5,5-tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane (5.26 g, 16.03

mmol, 2.3 equiv) in toluene (800 mL) was degassed and refluxed

under nitrogen for 12 h. Reaction mixture was cooled and passed

consecutively through pads of Celite, silica gel and neutral alumina

washing with toluene. Toluene was distilled off in vacuum, the residue

was separated by crystallization from dichloromethane by adding

methanol to afford [10,20-bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-

pyrenyl)porphyrinato(2-)]zinc(II) 2 (*MeOH complex, 6.2 g, 5.25

4,4,5,5-Tetramethyl-2-(coronen-1-yl)-1,3,2-dioxaborolane. Yield

140 mg (0.33 mmol, 7%). The yield depends on the ratio of

monobromocoronene in the mixture of bromocoronenes and can be

increased to 15% by using less amount of bromine, however separation

of the products turned to be more difficult due to the presence of

unreacted coronene in the mixture. ¹H NMR (CDCl₃, 500 MHz): 1.66

(s, 12H), 8.76−8.79 (m, 7H), 8.87 (dd, 2H, J¹= 2 Hz, J²= 8.5 Hz), 9.48

(s, 1H), 9.80 (d, 1H, J = 8.5 Hz). ¹³C NMR (CDCl₃, 100 MHz): 25.2,

84.2, 122.20, 122.22, 122.3, 122.4, 122.5, 124.1, 125.7, 125.9, 125.92,

126.0, 126.1, 126.2, 126.46, 126.52, 126.9, 127.6, 128.3, 128.4, 128.5,

129.3, 132.2, 136.1. HRMS: 426.1781 (M⁺), calcd. 426.1786 for

C₃₀H₂₃BO₂.

1

mmol, 75%). H NMR (CDCl₃, 400 MHz): 1.47, 1.477 and 1.481 (s,

36H, atropoisomers), 7.50 (dd, 2H, J = 9.3, 10.6 Hz), 7.71−7.74 (m,

4H, atropoisomers), 8.04−8.14 (m, 8H), 8.33 (t, 4H, J = 7.2 Hz), 8.42

(d, 2H, J = 9.1 Hz), 8.54 (d, 2H, J = 7.7 Hz), 8.63 (dd, 4H, J = 0.8, 4.7

Hz), 8.86 (dd, 2H, J = 2.8, 7.7 Hz), 8.92 (d, 4H, J = 4.7 Hz). ¹³C NMR

(CDCl₃, 100 MHz): 31.7, 35.0, 118.9, 120.8, 122.7, 122.8, 124.1,

124.7, 125.2, 125.5, 126.2, 127.4, 127.5, 127.7, 127.9, 129.6, 129.8,

129.9, 130.8, 131.3, 131.8, 132.0, 132.5, 132.6, 132.64, 133.4, 133.5,

137.9, 141.6, 148.6, 150.7, 151.0. UV/vis (CH₂Cl₂) λ, nm, (ε): 235

(84899), 243 (120670), 264 (48136), 275 (69032), 308 (34871), 323

(47186), 337 (54350), 427 (432531), 517 (6415), 551 (24905), 590

(5614). HRMS: 1149.4834 (M⁺and MH⁺), calcd. 1149.4808 for

C₈₀H₆₉N₄Zn. MALDI TOF: 1150 (M⁺and MH⁺), requires 1149.48

for C₈₀H₆₉N₄Zn. Elemental analysis for C₈₀H₆₈N₄Zn*MeOH: calcd C

82.25, H 6.14, N 4.74; found C 82.45, H 6.25, N 4.65.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(perylen-1-yl)-

porphyrinato(2-)]zinc(II) 3. A mixture of the above dibromoporphyr-

in (3.4 g, 3.75 mmol), cesium carbonate (12.6 g, 39 mmol, 10 equiv),

Pd(PPh₃)₄(430 mg, 10 mol %), pyridine (5 mL) and 4,4,5,5-

tetramethyl-2-(perylen-1-yl)-1,3,2-dioxaborolane⁴⁵(3.12 g, 8.25 mmol,

2.2 equiv) in toluene (200 mL) was degassed and refluxed under

nitrogen for 15 h. Reaction mixture was cooled and passed con-

secutively through pads of silica gel and neutral alumina washing with

dichloromethane. Solvents were distilled off in vacuum, the residue

was separated by crystallization from dichloromethane to afford

[10,20-bis-(3,5-di-tert-butylphenyl)-5,15-bis-(perylen-1-yl)-

porphyrinato(2-)]zinc(II) 3 (1.54 g, 1.23 mmol, 33%). ¹H NMR

1,7-Bis-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)coronene. The

mixture of bis-B(pin)coronenes (the second fraction after column

chromatography) was separated further by fractional crystallization

from dichloromethane by adding methanol. The first collected portion

of crystals can be identified as symmetric 1,7-bis-B(pin)-coronene due

to simplicity of H NMR spectrum. Yield, 300 mg (0.54 mmol). H

NMR (CDCl₃, 500 MHz): 1.63 (s, 24H), 8.90−8.95 (m, 6H), 8.53

(s, 2H), 9.88 (d, 2H, J = 8.5 Hz). HRMS: 552.2654 (M⁺), calcd.

552.2638 for C₃₆H₃₄B₂O₄.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(coronen-1-yl)-

porphyrinato(2-)]zinc(II) 4. A mixture of the above dibromoporphyr-

in (140 mg, 0.155 mmol), cesium carbonate (520 mg, 10 equiv),

Pd(PPh₃)₄(30 mg, 17 mol %), pyridine (1 mL) and 4,4,5,5-tetramethyl-

2-(coronen-1-yl)-1,3,2-dioxaborolane (132 mg, 0.301 mmol, 2 equiv)

in toluene (100 mL) was degassed and refluxed under nitrogen for

20 h. Toluene was distilled off in vacuum, the residue was separated on

silica gel column by using a mixture of dichloromethane−hexanes as

eluent. The first fraction (dichloromethane−hexanes = 1:9) contained

mono-coronenylporphyrin [10,20-bis-(3,5-di-tert-butylphenyl)-5-(cor-

onen-1-yl)porphyrinato(2-)]zinc(II). The second fraction (dichloro-

methane−hexanes = 3:9 to dichloromethane−pyridine = 100:1) contained

[10,20-bis-(3,5-di-tert-butylphenyl)-5,15-bis-(coronen-1-yl)-

porphyrinato(2-)]zinc(II) 4. Each fraction was crystallized from

dichloromethane by layered addition of methanol.

1

[10,20-Bis-(3,5-di-tert-butylphenyl)-5-(coronen-1-yl)-

1

porphyrinato(2-)]zinc(II). Yield 15 mg (0.0144 mmol, 9%). H NMR

153

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The Journal of Organic Chemistry

Article

(CDCl₃, 500 MHz): 1.51 (s, 18H), 1.512 (s, 18H), 7.77 (t, 2H, J = 1.5

Hz), 8.13 (t, 2H, J = 1.5 Hz), 8.16 (t, 2H, J = 1.5 Hz), 8.21 (d, 1H, J =

9 Hz), 8.50 (d, 1H, J = 9 Hz), 8.70 (d, 2H, J = 4.5 Hz), 8.81 (d, 1H,

J = 9 Hz), 8.93 (d, 2H, J = 4.5 Hz), 8.95 (d, 1H, J = 8.5 Hz), 8.99−

9.08 (m, 5H), 9.11 (d, 1H, J = 8.5 Hz), 9.20 (d, 2H, J = 4.5 Hz), 9.48

(d, 2H, J = 4.5 Hz), 9.75 (s, 1H), 10.37 (s, 1H). ¹³C NMR (CDCl₃,

150 MHz): 29.7, 31.73, 35.0, 106.3, 118.9, 120.8, 122.0, 122.3, 122.8,

122.9, 123.1, 126.2, 126.3, 126.34, 126.42, 126.49, 126.50, 126.6,

127.0, 127.2, 128.4, 129.0, 129.1, 129.7, 129.9, 131.7, 132.1, 132.5,

132.59, 132.61, 133.0, 134.3, 139.9, 141.5, 148.62, 148.64, 149.9,

150.8, 151.37, 151.4. HRMS: 1047.4358 (M⁺and MH⁺), calcd.

1047.4339 for C₇₂H₆₃N₄Zn.

2H, J = 9 Hz), 7.71 (s, 2H), 8.03−8.13 (m, 8H), 8.30−8.33 (m, 4H),

8.41 (d, 2H, J = 9 Hz), 8.50 (d, 2H, J = 8 Hz), 8.53 (d, 4H, J =

4.5 Hz), 8.84 (d, 4H, J = 4.5 Hz), 8.88 (t, 2H, J = 8 Hz). ¹³C NMR

(CDCl₃, 75 MHz): 31.7, 35.0, 119.2, 120.4, 122.5, 123.3, 124.1, 124.7,

125.0, 125.3, 126.1, 127.1, 127.7, 127.8, 129.9, 130.0, 130.1, 131.1,

131.8, 132.5, 132.7, 132.8, 133.4, 133.5, 139.0, 142.4, 148.1, 148.2,

150.3, 150.7. UV/vis (CH₂Cl₂) λ, nm, (ε): 275 (67301), 338 (55958),

433 (468074), 525 (5750), 566 (22856), 606 (13367). HRMS:

1108.5298 (M⁺), calcd. 1108.5289 for C₈₀H₆₈N₄Mg.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)]lead(II) 2-Pb. A mixture of porphyrin 2-H (100 mg,

0.092 mmol) and Pb(OAc)₂*3H₂O (100 mg) in pyridine (5 mL) was

refluxed for 1 h. Reaction mixture was diluted with dichloromethane

and passed though a short plug of alumina washing with dichloro-

methane. Dichloromethane was evaporated in vacuum and the residue

crystallized from dichloromethane by adding methanol. Yield 95 mg

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(coronen-1-yl)-

1

porphyrinato(2-)]zinc(II) 4. Yield 117 mg (0.0869 mmol, 56%). H

NMR (5% pyridine-d₅in CDCl₃, 600 MHz): 1.38, 1.39, and 2.71 (s,

36H, atropoisomers), 7.62 (br s, 2H), 8.00, 8.06, and 8.11 (br s, 4H,

atropoisomers), 8.05 and 8.12 (d, 1H, J = 9 Hz, atropoisomers), 8.40

and 8.43 (d, 2H, J = 9 Hz, atropoisomers), 8.57−8.59 (m, 6H), 8.78

(t, 2H, J = 9 Hz), 8.80−8.81 (m, 4H), 8.92−8.94 (m, 2H), 8.97−9.11

(m, 10H), 9.78 and 9.80 (s, 2H, atropoisomers). ¹³C NMR (5%

pyridine-d₅in CDCl₃, 150 MHz): 29.6, 31.6, 34.8, 118.1, 120.4,

121.8, 122.35, 122.37, 122.5, 122.7, 122.72, 122.8, 123.6, 125.88,

125.95, 126.14, 126.16, 126.2, 126.29, 126.34, 126, 41, 126.47, 126.9,

127.1, 127.2, 127.3, 128.24, 128.26, 128.9, 129.0, 129.4, 129.7, 129.8,

131.6, 132.3, 132.6, 135.8, 139.6, 140.3, 142.2, 148.0, 148.1, 149.8,

150.6, 151.1. UV/vis (CH₂Cl₂) λ, nm, (ε): 304 (239778), 342

(45247), 427 (472969), 434 (359453), 513 (6346), 551 (30874),

588 (7212). HRMS: 1344.5046 (M⁺and MH⁺), calcd. 1344.5043 for

C₉₆H₇₂N₄Zn.

1

(0.073 mmol, 80%). H NMR (CDCl₃, 500 MHz): 1.44−1.51 (m,

36H), 7.08 and 7.20 (d, 1H, J = 8 Hz), 7.05−7.61 (m, 2H), 7.73−7.75

(m, 2H), 7.87−8.68 (m, 22H), 8.82−9.07 (m, 5H). ¹³C NMR

(CDCl₃, 75 MHz): 31.7, 31.8, 35.0, 117.8, 119.8, 119.83, 119.85,

120.8, 121.0, 121.8, 122.5, 122.7, 122.8, 124.0, 124.1, 124.6, 124.8,

125.2, 125.24, 125.29, 125.4, 125.5, 126.21, 126.25, 127.3, 127.4,

127.5, 127.55, 127.64, 127.7, 127.8, 127.9, 128.0, 129.3, 129.4, 129.5,

129.7, 129.9, 130.0, 130.3, 130.4, 130.6, 130.8, 130.9, 131.2, 131.3,

131.4, 131.7, 131.8, 131.96, 131.98, 132.1, 132.6, 132.7, 132.75, 133.5,

133.6, 133.8, 133.9, 137.3, 138.1, 138.2, 140.9, 141.8, 148.3, 148.5,

148.7, 149.6, 149.62, 149.66, 149.9, 150.0, 150.1, 150.2. UV/vis

(CH₂Cl₂) λ, nm, (ε): 276 (80104), 340 (81161), 426 (90864), 472

(236200), 556 (5565), 612 (9467), 662 (16969). HRMS: 1292.5243

(M⁺), calcd. 1292.5205 for C₈₀H₆₈N₄Pb.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)porphyrin

2-H. Porphyrin 2 (950 mg, 0.826 mmol) was dissolved in dichloro-

methane (100 mL). Concentrated hydrochloric acid (3 mL) was

added and the resulting green solution was vigorously stirred for 30 s.

The reaction mixture was quenched with pyridine, passed though plug

of silica gel washing with dichloromethane. All purple fractions were

collected, solvents were evaporated and the residue was crystallized

from dichloromethane by adding methanol. Yield 850 mg (0.782

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)](II)palladium 2-Pd. A mixture of porphyrin 2-H

(100 mg, 0.092 mmol) and PdCl₂(50 mg) in benzonitrile (25 mL)

was refluxed for 3 h. Benzonitrile was distilled off in vacuum and the

residue passed though a short plug of alumina washing with di-

chloromethane. Dichloromethane was evaporated in vacuum and the

residue crystallized from dichloromethane by adding methanol. Yield

70 mg (0.059 mmol, 64%). ¹H NMR (CDCl₃, 500 MHz): 1.45, 1.456,

1.46, and 1.54 (s, 36H, atropoisomers), 7.41−7.48 (m, 2H), 7.72−7.75

(m, 4H), 8.05 (d, 4H, J = 2 Hz), 8.07 (d, 2H, J = 8 Hz), 8.10 (d, 2H,

J = 8 Hz), 8.31−8.35 (m, 4H), 8.40 (d, 2H, J = 8 Hz), 8.48−8.53 (m,

6H), 8.78 (d, 4H, J = 4.5 Hz), 8.78−8.80 (m, 2H). ¹³C NMR (CDCl₃,

75 MHz): 31.7, 35.0, 119.5, 121.0, 122.8, 123.4, 124.1, 124.6, 125.3,

125.5, 126.3, 127.2, 127.6, 127.7, 128.0, 129.4, 130.8, 130.9, 131.4,

131.6, 131.7, 132.2, 132.3, 133.2, 136.7, 140.6, 141.9, 142.3, 148.7.

UV/vis (CH₂Cl₂) λ, nm, (ε): 275 (71971), 338 (49029), 424

(323602), 526 (36618), 557 (6234). HRMS: 1190.4529 (M⁺and

MH⁺), calcd. 1190.4473 for C₈₀H₆₈N₄Pd.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)](II)platinum 2-Pt. A mixture of porphyrin 2-H

(100 mg, 0.092 mmol) and PtCl₂(50 mg) in benzonitrile (25 mL) was

refluxed for 3 h. Benzonitrile was distilled off in vacuum and the

residue passed though a short plug of alumina washing with

dichloromethane. Dichloromethane was evaporated in vacuum and

the residue crystallized from dichloromethane by adding methanol.

Yield 80 mg (0.063 mmol, 68%). ¹H NMR (CDCl₃, 400 MHz): 1.446,

1.45, 1.46, and 1.53 (s, 36H, atropoisomers), 7.44 and 7.50 (d, 2H, J =

9 Hz, atropoisomers), 7.72 (t, 2H, J = 2 Hz), 7.73 and 7.76 (d, 2H, J =

10 Hz, atropoisomers), 7.97−8.08 (m, 6H), 8.12 (d, 2H, J = 8 Hz),

8.32 (t, 4H, J = 10 Hz), 8.39 (d, 2H, J = 9 Hz), 8.43 and 8.44 (d,

4H, J = 5 Hz, atropoisomers), 8.52 and 8.54 (d, 2H, J = 8 Hz,

atropoisomers), 8.73 (d, 4H, J = 5 Hz), 8.78 and 8.81 (d, 2H, J = 8 Hz,

atropoisomers). ¹³C NMR (CDCl₃, 125 MHz): 31.7, 35.0, 120.1,

121.1, 122.9, 123.9, 124.2, 124.6, 125.3, 126.3, 127.0, 127.7, 127.72,

128.0, 129.0, 129.1, 129.2, 130.6, 130.9, 131.4, 131.5, 131.7, 132.0,

132.1, 133.1, 133.12, 136.24, 136.26, 140.2, 141.2, 141.6, 148.82,

148.8, 148.9. UV/vis (CH₂Cl₂) λ, nm, (ε): 275 (87028), 339 (57026),

410 (297768), 513 (43155), 542 (10805). HRMS: 1279.5071 (M⁺and

MH⁺), calcd. 1279.5086 for C₈₀H₆₈N₄Pt.

1

mmol, 95%). H NMR (CDCl₃, 400 MHz): 1.47, 1.48, and 1.49 (s,

36H, atropoisomers), 7.52 (t, 2H, J = 9 Hz), 7.73−7.75 (m, 4H),

8.05−8.14 (m, 8H), 8.31−8.36 (m, 4H), 8.41 (d, 2H, J = 8 Hz), 8.52−

8.55 (m, 6H), 8.83 (d, 4H, J = 4.8 Hz), 8.86 (t, 2H, J = 8 Hz). ¹³C

NMR (CDCl₃, 75 MHz): 31.7, 35.0, 117.8, 121.0, 121.8, 122.8, 124.1,

124.6, 125.3, 125.6, 126.3, 127.3, 127.6, 127.7, 128.0, 129.7, 129.9,

130.0, 130.8, 131.4, 131.8, 132.57, 132.63, 133.46, 133.51, 137.3,

140.9, 148.8. MALDI TOF: 1086.0 (M⁺), requires 1086.6 for

C₈₀H₇₀N₄.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)]copper(II) 2-Cu. To a solution of porphyrin 2-H

(100 mg, 0.092 mmol) in dichloromethane (100 mL), solution of

Cu(OAc)₂*2H₂O in methanol (10 mL) was added and the resulting

mixture was refluxed for 1 h. The residue after evaporation of solvents

was passed though a short plug of alumina washing with dichloro-

methane. Dichloromethane was evaporated in vacuum and the residue

crystallized from dichloromethane by adding methanol. Yield 90 mg

(0.078 mmol, 85%).¹H NMR (CDCl₃, 400 MHz): 1.38 (br s, 36H),

7.61, 8.03, 8.16, 8.28 (br s, 32H) broad signals due to the presence of

copper(II) in the structure. ¹³C NMR (CDCl₃, 75 MHz): 31.6, 34.7,

120.5, 122.5, 123.4, 124.4, 125.1, 125.3, 126.3, 127.4, 127.6, 127.8,

130.8, 131.0, 131.7, 133.3, 148.3. UV/vis (CH₂Cl₂) λ, nm, (ε): 275

(74683), 337 (54521), 423 (409921), 541 (29288), 575 (5576).

HRMS: 1147.4761 (M⁺), calcd. 1147.4734 for C₈₀H₆₈N₄Cu.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)]magnesium(II) 2-Mg. A mixture of porphyrin 2-H

(100 mg, 0.092 mmol) and MgI₂(100 mg) in pyridine (10 mL) was

refluxed for 1 h. Reaction mixture was diluted with dichloromethane

and passed though a short plug of alumina washing with dichloro-

methane. Dichloromethane was evaporated in vacuum and the residue

crystallized from dichloromethane by adding methanol. Yield 95 mg

1

(0.086 mmol, 93%). H NMR (CDCl₃, 400 MHz): 1.47, 1.48, and

1.49 (s, 36H), 7.47 (d, 1H, J = 9 Hz), 7.49 (d, 1H, J = 9 Hz), 7.68 (d,

154

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Article

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7,15,17-bis-(1,8-naphthyl)-

porphyrinato(2-)]zinc(II) and [10,20-bis-(3,5-di-tert-butylphenyl)-

3,5,15,17-bis-(1,8-naphthyl)-porphyrinato(2-)]zinc(II) 1d. Bis-naph-

thyl-porphyrin 1*MeOH (0.97 g, 0.937 mmol) in a glass boat was

placed into a glass tube. The tube was purged with nitrogen and kept

under positive nitrogen atmosphere. The tube was placed into furnace

preheated to 530 °C and kept there for 12 min under nitrogen

atmosphere. First, the furnace temperature rose to 530 °C in 1−2 min

and after additional ca. 2 min starting material melted. Reaction

mixture turned brown after 3−4 min and bubbles appeared. After ca.

5 min the tube was taken out from the furnace and cooled to room

temperature under nitrogen. Prolonged heating causes reduced yields

of the doubly fused product 1d. The crude mixture was dissolved in

dichloromethane (100 mL) and separated on alumina column (400 g).

Elution with hexanes:dichloromethane:pyridine = 700:300:5 mixture

gave crude doubly fused porphyrin 1d which was recrystallized from

dichloromethane by layered addition of methanol to give 1d (70 mg,

0.07 mmol, 7%). ¹H NMR contained only broad signals due to

pronounced aggregation or forming oxidized paramagnetic species.

UV/vis (CH₂Cl₂) λ, nm, (ε): 418 (70111), 486 (147059), 648

(25731), 730 (39704). HRMS: 996.4106 (M⁺and MH⁺), calcd.

996.4104 for C₆₈H₆₀N₄Zn. The second fraction (dichloromethane−

pyridine = 1000:5) contained doubly fused product with the loss of

one di-tert-butylphenyl group (100 mg, 13%): MALDI-TOF: 807.27

(M⁺), calcd. 808.25 for C₅₄H₄₀N₄Zn.

[10,20-Bis-(3,5-di-tert-butylphenyl)-3,5-(1,10-pyrenyl)-15-(1-

pyrenyl)porphyrinato(2-)]zinc(II) (2m) and [10,20-bis-(3,5-di-tert-

butylphenyl)-3,5,13,15-bis-(1,10-pyrenyl)-porphyrinato(2-)]zinc(II)

(2d). The above bis-pyrenyl-porphyrin 2*MeOH (1 g, 0.845 mmol)

in a glass boat was placed into a glass tube. The tube was purged with

nitrogen and kept under positive nitrogen atmosphere. The tube was

placed into furnace preheated to 530 °C and kept there for 5 min

under nitrogen atmosphere. First, the furnace temperature rose to

530 °C in 1−2 min and after additional ca. 1−2 min starting material

melted. Reaction mixture turned brown immediately and bubbles

appeared. After ca. 0.5 min the tube was taken out from the furnace

and cooled to room temperature under nitrogen. Prolonged heating

causes reduced yields of the doubly fused product 2d. This cycle was

repeated 5 times (totally, 6 g of porphyrin 2). The crude mixture was

dissolved in dichloromethane (100 mL) with addition of hexanes (300

mL) and pyridine (5 mL) and separated on alumina column (400 g).

Elution with dichloromethane gave first fraction which contained

compound 2m. Elution with hexanes:dichloromethane:pyridine =

700:300:5 mixture gave crude doubly fused porphyrin 2d which was

recrystallized from dichloromethane by layered addition of methanol

to give 2d (ca. 93−95% purity 1.80 g, 30%). Elution with

dichloromethane:pyridine = 1000:5 mixture gave a mixture of doubly

fused porphyrins with the loss of one di-tert-butyl-phenyl group which

were recrystallized from dichloromethane-pyridine by layered addition

of methanol (2.3 g, 38%). Higher purity doubly fused porphyrin 2d

can be obtained by column chromatography on silica gel (gradient

elution with hexanes:dichloromethane mixtures 1000:50 to 800:200).

First fraction containing compound 2m was additionally purified by

silica gel column (gradient elution with hexanes:ethyl acetate mixtures

1000:5 to 1000:15) and crystallized from dichloromethane by layered

addition of methanol to give compound 2m (0.54 g, 9%).

131.2, 131.4, 131.6, 131.8, 131.9, 132.2, 132.3, 132.5, 132.69, 132.75,

132.8, 132.9, 133.0, 133.8, 133.9, 137.4, 138.0, 139.0, 143.4, 143.5,

146.8, 149.08, 149.10, 149.23, 149.26, 150.3, 150.5, 150.6, 151.0,

151.8, 152.0, 152.3. UV/vis (CH₂Cl₂) λ, nm, (ε): 706 (43480), 495

(206480), 386 (40296), 339 (45680), 324 (38374), 275 (51790), 264

(44275). Emission (CH₂Cl₂): λ_max, 722 nm; quantum yield, 8.0%.

HRMS: 1146.4581 (M⁺), calcd. 1146.4573 for C₈₀H₆₆N₄Zn. Elemental

analysis for C₈₀H₆₆N₄Zn*MeOH: calcd C 82.39, H 5.97, N 4.74;

found C 82.69, H 5.91, N 4.86.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7,15,17-bis-(1,10-pyrenyl)-

porphyrinato(2-)]zinc(II) and [10,20-bis-(3,5-di-tert-butylphenyl)-

3,5,15,17-bis-(1,10-pyrenyl)-porphyrinato(2-)]zinc(II) 2d. (1:1 mix-

ture of anti/syn regioisomers). ¹H NMR (5%-pyridine-d₅in C₆D₆,

25 °C, 500 MHz, two regioisomers): 1.53, 1.59, and 1.61 (s, 36H,

regioisomers), 7.81 and 7.82 (d, 2H, J = 8 Hz, regioisomers), 7.91−

8.03 (m, 8H), 8.1 and 8.17 (t, 2H, J = 1.5 Hz, regioisomers), 8.26 and

8.28 (d, 2H, J = 8.5 Hz, regioisomers), 8.40, 8.55, and 8.62 (d, 4H, J =

1.5 Hz, regioisomers), 9.00 and 9.08 (d, 2H, J = 4.5 Hz, regioisomers),

9.07 and 9.12 (s, 2H, regioisomers), 9.28 and 9.36 (d, 2H, J = 4.5 Hz,

regioisomers), 9.33 and 9.35 (d, 2H, J = 8 Hz, regioisomers), 9.78 and

1

9.84 (s, 2H, regioisomers). H NMR (5%-pyridine-d₅in C₆D₆, 75 °C,

500 MHz, two regioisomers): 1.51, 1.57, and 1.60 (s, 36H

regioisomers), 7.08 (t, 2H, J = 8 Hz), 7.92 (t, 2H, J = 9 Hz), 7.99

(d, 4H, J = 8 Hz), 8.04 (s, 2H), 8.06 and 8.15 (s, 2H, regioisomers),

8.02−8.06 (m, 4H), 8.45 and 8.54 (d, 2H, J = 1 Hz, regioisomers),

8.90 and 8.93 (d, 2H, J = 4.5 Hz, regioisomers), 9.11 and 9.13 (s, 2H,

regioisomers), 9.23−9.30 (m, 4H), 9.67 and 9.70 (s, 2H,

regioisomers). ¹³C NMR (5%-pyridine-d₅in C₆D₆, 25 °C, 125 MHz,

two regioisomers): 30.1, 31.84, 31.92, 31.94, 35.20, 114.0, 114.2, 121.1,

121.3, 121.4, 122.7, 124.1, 124.2, 124.8, 125.4, 125.41, 125.8, 126.4,

126.9, 127.4, 127.42, 127.5, 128.9, 129.0, 130.3, 130.5, 130.7, 130.8,

131.8, 132.0, 132.9, 133.0, 133.03, 133.3, 133.4, 133.6, 136.5, 136.6,

138.0, 138.4, 143.3, 143.4, 146.7, 147.4, 149.2, 150.1, 150.4, 150.5,

150.8, 151.1. Emission (CH₂Cl₂): λ_max, 815 nm; quantum yield, 10%.

MALDI TOF: 1143.9 (M⁺), requires 1144.44 for C₈₀H₆₄N₄Zn.

HRMS: 1144.4410 (M⁺), calcd. 1144.4417 for C₈₀H₆₄N₄Zn. Elemental

analysis for C₈₀H₆₄N₄Zn*MeOH: calcd C 82.53, H 5.81, N 4.75;

found C 82.92, H 5.77, N 4.78.

anti-[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7,15,17-bis-(1,10-pyr-

enyl)-porphyrinato(2-)]zinc(II) anti-2d. anti-2d can be obtained by

separation of a mixture of anti/syn 2d using silica gel column (gradient

elution with benzene:hexanes −1:5 to 2:3) by collecting first fraction

followed by layered crystallization from dichloromethane:methanol

1

mixture. R_f= 0.42 (hexanes−benzene = 1:1). H NMR (5%-pyridine-

d₅in C₆D₆, 25 °C, 500 MHz): 1.59 (s, 36H, t-Bu), 7.83 (t, 2H, J = 8

Hz, H⁷_pyrene), 7.93 (d, 2H, J = 9 Hz, H_pyrene), 7.99 (d, 2H, J = 9 Hz,

H_pyrene), 8.00 (d, 2H, J = 8 Hz, H⁶_pyrene), 8.05 (d, 2H, J = 8 Hz,

H⁸_pyrene), 8.04 (t, 2H, J = 1.5 Hz, p-H of Ar), 8.27 (d, 2H, J = 9 Hz,

H_pyrene), 8.50−8.51 (m, 2H, o-H of Ar), 8.55 (d, 2H, J = 1.5 Hz, o-H of

Ar), 9.00 (d, 2H, J = 4.5 Hz, β-pyrrolic H^7,17_porph), 9.13 (s, 2H, β-

pyrrolic H^2,12_porph), 9.27 (d, 2H, J = 4.5 Hz, β-pyrrolic H^8,18_porph), 9.33

(d, 2H, J = 8 Hz, H_pyrene), 9.84 (s, 2H, H⁹_pyrene).¹³C NMR (5%-

pyridine-d₅in C₆D₆, 125 MHz): 32.0, 35.3, 114.3, 121.3, 122.9, 124.4,

124.5, 125.4, 125.9, 126.4, 126.75, 126.81, 127.4, 129.2, 130.5, 130.8,

131.8, 132.0, 133.0, 133.3, 133.5, 136.7, 138.1, 143.4, 146.8, 149.5,

150.2, 150.4, 151.2. UV/vis (CH₂Cl₂) λ, nm, (ε): 815 (81206), 741

(20628), 656 (5045), 559 (54452), 504 (151197). Emission

(CH₂Cl₂): λ_max, 839 nm; quantum yield, 7.7%.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7-bis-(1,10-pyrenyl)-15-(1-

pyrenyl)porphyrinato(2-)]zinc(II) 2m. ¹H NMR (5%-pyridine-d₅in

C₆D₆, 500 MHz): 1.49, 1.507, 1510, and 1.52 (s, 36H, atropoisomers),

7.39 (d, 1H, J = 9.5 Hz), 7.59 (d, 1H, J = 9.5 Hz), 7.78−7.85 (m, 3H),

7.94−7.96 (m, 2H), 8.01 (s, 1H), 8.02−8.09 (m, 5H), 8.14 (d, 1H, J =

9.5 Hz), 8.24 (d, 1H, J = 8 Hz), 8.32 (d, 1H, J = 8 Hz), 8.39 (t, 1H, J =

1.5 Hz), 8.45 (t, 1H, J = 1.5 Hz), 8.53 (t, 1H, J = 1.5 Hz), 8.55 (d, 1H,

J = 4.5 Hz), 8.56 (t, 1H, J = 1.5 Hz), 8.63 (d, 1H, J = 4.5 Hz), 8.84 (d,

1H, J = 8 Hz), 9.03 (d, 1H, J = 4.5 Hz), 9.09 (d, 1H, J = 4.5 Hz), 9.13

(s, 1H), 9.22 (d, 1H, J = 4.5 Hz), 9.48 (d, 1H, J = 8.5 Hz), 9.53 (d, 1H,

J = 4.5 Hz), 9.98 (s, 1H). ¹³C NMR (5%-pyridine-d₅in C₆D₆, 125

MHz): 30.2, 31.85, 31.86, 31.89, 35.18, 35.20, 114.3, 119.0, 121.00,

121.03, 124.3, 124.6, 124.8, 124.9, 125.0, 125.3, 125.4, 125.7, 125.8,

126.3, 126.4, 126.8, 127.4, 127.7, 129.1, 130.7, 130.86, 130.90, 131.0,

syn-[10,20-Bis-(3,5-di-tert-butylphenyl)-3,5,15,17-bis-(1,10-pyrenyl)-

porphyrinato(2-)]zinc(II) syn-2d. syn-2d can be obtained by

separation of a mixture of anti/syn 2d using silica gel column

(gradient elution with benzene−hexanes= −1:5 to 2:3) by collecting

the last fractions followed by layered crystallization from dichloro-

methane-methanol mixture. R_f= 0.31 (hexanes−benzene = 1:1).

¹H NMR (5%-pyridine-d₅in C₆D₆, 25 °C, 500 MHz): 1.53 (s, 18H, t-Bu),

1.61 (s, 18H, t-Bu), 7.82 (t, 2H, J = 8 Hz, H⁷_pyrene), 7.93 (d, 2H, J = 9

Hz, H_pyrene), 7.99 (d, 2H, J = 9 Hz, H_pyrene), 8.00 (t, 1H, J = 1.5 Hz,

p-H of Ar), 8.00 (d, 2H, J = 8 Hz, H⁶_pyrene), 8.05 (d, 2H, J = 8 Hz,

H⁸_pyrene), 8.17 (t, 1H, J = 1.5 Hz, p-H of Ar), 8.27 (d, 2H, J = 9 Hz,

H_pyrene), 8.40 (2, 2H, J = 1.5 Hz, o-H of Ar), 8.61 (d, 2H, J = 1.5 Hz,

155

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The Journal of Organic Chemistry

Article

o-H of Ar), 9.07 (d, 2H, J = 4.5 Hz, β-pyrrolic H^7,17_porph), 9.08 (s, 2H,

β-pyrrolic H^2,12_porph), 9.36 (d, 2H, J = 4.5 Hz, β-pyrrolic H^8,18_porph),

9.37 (d, 2H, J = 8 Hz, H_pyrene), 9.78 (s, 2H, H⁹_pyrene).¹³C NMR (5%-

pyridine-d₅in C₆D₆, 125 MHz): 30.2, 31.9, 32.0, 114.0, 121.1, 121.4,

122.52, 122.54, 123.3, 123.34, 124.3, 125.0, 125.5, 125.9, 126.3, 126.8,

127.4, 127.5, 128.6, 128.7, 128.8, 129.0, 129.7, 129.85, 129.9, 130.5,

130.80, 130.85, 131.8, 131.9, 132.9, 133.0, 133.7, 136.6, 138.5, 143.3,

143.5, 147.4, 149.2, 149.5, 150.6, 150.8. UV/vis (CH₂Cl₂) λ, nm, (ε):

811 (91461), 736 (26446), 657 (10865), 527 (145812). Emission

(CH₂Cl₂): λ_max, 829 nm; quantum yield, 12.8%.

(65502). HRMS: 1244.4745 (M⁺and MH⁺), calcd. 1244.4730 for

C₈₈H₆₈N₄Zn.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7,15,17-bis-(1,12-coronen-

yl)-porphyrinato(2-)]zinc(II) and [10,20-bis-(3,5-di-tert-butylphen-

yl)-3,5,15,17-bis-(1,12-coronenyl)-porphyrinato(2-)]zinc(II) 4d. Bis-

coronenyl-porphyrin 4 (90 mg, 0.067 mmol) in a glass boat was

placed into a glass tube. The tube was purged with nitrogen and kept

under positive nitrogen atmosphere. The tube was placed into furnace

preheated to 560 °C and kept there for 5 min under nitrogen

atmosphere. First, the furnace temperature rose to 560 °C in 1−2 min

and after additional ca. 1−2 min starting material melted. Once

porphyrin material melted, the tube was taken out from the furnace

and cooled by liquid nitrogen. The crude mixture was dissolved in

dichloromethane (100 mL) and pyridine (3 mL) and separated on

alumina column (50 g). Elution with dichloromethane−pyridine =

1000:5 mixture gave doubly fused porphyrin 4d which was

recrystallized from dichloromethane by layered addition of methanol

anti-[10-(3,5-Di-tert-butylphenyl)-5,7,15,17-bis-(1,10-pyrenyl)-

porphyrinato(2-)]zinc(II), syn-[10-(3,5-di-tert-butylphenyl)-3,5,15,17-bis-

(1,10-pyrenyl)-porphyrinato(2-)]zinc(II) and syn-[20-(3,5-di-tert-butyl-

phenyl)-3,5,15,17-bis-(1,10-pyrenyl)-porphyrinato(2-)]zinc(II). Com-

pounds anti-2d and syn-2d with the loss of one di-tert-butylphenyl

group can be obtained as a mixture of isomers by chromatography

separation on alumina (fractions eluting with dichloromethane−

1

to give 4d (12 mg, 0.009 mmol, 13%). H NMR spectra of porphyrin

pyridine = 1000:5). H NMR (5%-pyridine-d₅in C₆D₆, 25 °C, 500

4d contain only broad signals using different solvents and temper-

atures due to aggregation in solution. Taking into account significant

fragmentation of the product in mass spectra, the chromatographically

pure material may have admixtures of the corresponding fused prod-

ucts with the loss of one or two di-tert-butyl groups. UV/vis (CH₂Cl₂)

λ, nm, (ε): 437 (102102), 494 (220965), 687 (54277), 779 (81911).

MALDI-TOF: 1340.14 (M⁺), calcd. 1340.47 for C₉₆H₆₈N₄Zn; 1152.02

(M⁺− 188 (C₁₄H₂₁= di-tert-butylphenyl group+H)), calcd 1152.32 for

C₈₂H₄₈N₄Zn; 964.34 (M⁺− 376 (C₂₈H₄₂= 2*di-tert-butylphenyl group

+2H)), calcd 964.16 for C₆₈H₂₈N₄Zn.

[5,15-Bis-(1-pyrenyl)porphyrinato(2-)]zinc(II). Trifluoroacetic acid

(2 mL) was added to a stirred solution of 1-pyrenecarboxaldehyde (3.7

g, 15.92 mmol) and dipyrromethane (2.34 g, 15.92 mmol) under

nitrogen in dichloromethane (2 L). The reaction mixture was stirred at

ambient temperature in dark for 48 h. After that DDQ (5.36 g) was

added and stirring continued for an additional hour. The reaction

mixture was quenched with triethylamine (10 mL) and passed through

filter filled with silica gel (50 g) washing with dichloromethane. All

purple fractions were collected, dichloromethane evaporated and the

residue passed through filter filled with alumina (50 g) washing with

dichloromethane. All purple fractions were collected, dichloromethane

was evaporated to a volume 500 mL. To this solution of the free-base

bis-pyrenyl-porphyrin, 30 mL of saturated solution of zinc(II) acetate

in methanol (10 mL) was added and the resulting mixture was stirred

for 3 h at ambient temperature. The reaction mixture was washed with

water and dichloromethane solution was passed through filter filled

with silica gel (50 g) washing with dichloromethane. The residue after

evaporation of solvent was crystallized from dichloromethane by

adding methanol to give [5,15-bis-(1-pyrenyl)porphyrinato(2-)]zinc-

(II) (430 mg, 0.56 mmol, 7%).

MHz, broad signals, isomers): 1.51−1.65 (m, 18H, t-Bu), 7.61−8.70

(m, 17H), 9.02−9.60 (m, 9H), 9.78 and 9.94 (s, 2H, isomers). UV/vis

(CH₂Cl₂) λ, nm: 806, 729, 553sh, 520sh, 501, 369, 345. HRMS:

956.2823 (M⁺), requires 956.2852 for C₆₆H₄₄N₄Zn.

[10,20-Bis-(3,5-di-tert-butylphenyl)-5,7,15,17-bis-(1,12-perylenyl)-

porphyrinato(2-)]zinc(II) and [10,20-bis-(3,5-di-tert-butylphenyl)-

3,5,15,17-bis-(1,12-perylenyl)-porphyrinato(2-)]zinc(II) 3d. Bis-pery-

lenyl porphyrin 3 (380 mg, 0.304 mmol) was dissolved in dry

dichloromethane (600 mL) under nitrogen atmosphere at 20 °C and

to the resulting solution anhydrous FeCl₃(1.2 g) was added at once.

The reaction mixture was vigorously stirred for 15 min and after that

quenched with pyridine (5 mL). The resulting purple solution was passed

through short plugs of alumina (prewashed with dichloromethane−

pyridine = 1000:5) and silica gel (prewashed with dichloromethane-

pyridine =1000:5) eluting with dichloromethane−pyridine = 1000:5.

All purple fractions were collected. MALDI-TOF indicated the

presence of the corresponding free-base porphyrin fused with two

perylene rings: 1182.43 (M⁺), calcd. 1182.56 for C₈₈H₇₀N₄. Solution of

Zn(OAc)₂*2H₂O (1 g) in methanol (30 mL) was added and stirred at

room temperature for 2 h. After that solvents were evaporated in

vacuum and the residue passes through short plug of silica gel

(prewashed with dichloromethane−pyridine = 1000:5) eluting with

dichloromethane−pyridine = 1000:5. Solvents were evaporated in

vacuum and the residue was crystallized from dichloromethane by

layered addition of methanol. Yield of 3d 250 mg (0.200 mmol, 67%).

Fused product 3d can be also obtained by thermal cyclodehydroge-

nation method at 550 °C as evidenced by absorption peaks

corresponding to the doubly fused product at 900 nm in the crude

reaction mixture and peaks of the molecular ion in MALDI-TOF

1

spectrum. H NMR (5% pyridine-d₅in C₆D₆, 500 MHz, syn/anti =

[10,20-Bis-bromo-5,15-bis-(1-pyrenyl)porphyrinato(2-)]zinc(II). NBS

(194 mg, 1.09 mmol, 2.1 equiv.) was added to a stirred solution of the

above 5,15-bis-(1-pyrenyl)porphyrinato(2-)]zinc(II) (402 mg, 0.519

mmol) in dichloromethane (300 mL) and pyridine (5 mL) at −10 °C

(NaCl/ice bath) under nitrogen atmosphere. Reaction mixture was

stirred at the same temperature for 10 min, then was allowed to warm

to 0 °C in 5 min (water bath) and after that reaction mixture was

quenched with acetone (20 mL). Crude reaction mixture was passed

through silica gel column, eluting with dichloromethane−pyridine

mixture (100:1). All green-purple fractions were collected, solvents

were evaporated, the residue was dissolved in dichloromethane−

pyridine mixture (95:5, 100 mL) and 200 mL of methanol was added

to precipitate brominated porphyrin. All crystals were collected by

filtration after 30 min to give [10,20-bis-bromo-5,15-bis-(1-pyrenyl)-

0.75:1): 1.54 (syn), 1.60 (anti) and 1.62 (syn) (s, 36H, t-Bu), 7.55

(anti) and 7.56 (syn) (d, 4H, J = 8 Hz, H_perylene), 8.00 (syn), 8.09 (anti)

and 8.14 (syn) (t, 2H, J = 1.5 Hz, o-H of Ar), 8.15−8.19 (m, 4H), 8.26

(syn) and 8.32 (anti) (d, 2H, J = 8 Hz, H_perylene), 8.37−8.52 (m, 8H),

8.43 (syn), 8.55 (anti) and 8.58 (syn) (d, 4H, J = 1.5 Hz, p-H of Ar),

8.72 (anti) and 8.77 (syn) (d, 2H, J = 8 Hz, H_perylene), 9.02 (anti) and

9.11 (syn) (d, 2H, J = 4.5 Hz, β-pyrrolic H_porph), 9.09 (anti) and 9.21

(syn) (d, 2H, J = 4.5 Hz, β-pyrrolic H_porph), 9.59 (syn) and 9.66 (anti)

(s, 2H, H¹²_perylene). ¹³C NMR (5%-pyridine-d₅in C₆D₆, 125 MHz):

30.2, 31.9 (syn), 31.95 (anti) and 31.99 (syn), 113.1 (syn) and 113.4

(anti), 121.2, 121.56 (anti) and 121.59 (syn), 121.7, 121.8, 121.86,

121.92, 122.0, 122.05, 122.15, 122.3, 123.5, 125.4 (anti) and 125.5

(syn), 125.55 (anti) and 125.6 (syn), 126.0, 126.1, 126.3, 127.1, 127.4,

128.48, 128.52, 129.13, 129.17, 129.4, 129.89, 129.90, 130.48 (syn) and

130.52 (anti), 131.36 (syn) and 131.40 (anti), 131.66, 131.72, 131.9,

132.7 (syn) and 132.9 (anti), 133.2 (anti) and 133.5 (syn), 134.98

(anti) and 135.00 (syn), 135.2, 137.6, 138.4, 139.61 (syn) and 139.71

(anti), 143.42, 143.43, 143.46, 143.2 (anti) and 146.8 (syn), 148.9

(syn) and 149.2 (anti), 149.52 (anti) and 149.64 (syn), 150.2, 150.3,

150.8, 151.4 (syn) and 151.6 (anti). UV/vis (CH₂Cl₂) λ, nm, (ε): 297

(18355), 426 (20215), 469 (21794), 538 (71476), 592 (44671), 901

1

porphyrinato(2-)]zinc(II) (435 mg, 0.47 mmol, 90%). H NMR (5%

pyridine-d₅in CDCl₃, 500 MHz, atropoisomers): 6.93 (t, 2H, J = 8 Hz),

7.19 (d, 2H, J = 10 Hz), 7.61 (d, 2H, J = 10 Hz), 8.06−8.09 (m, 4H),

8.32−8.36 (m, 4H), 8.42 (d, 2H, J = 8 Hz), 8.52 (d, 4H, J = 4.5 Hz),

8.79 (d, 2H, J = 8 Hz), 9.55 (d, 4H, J = 4.5 Hz).

[5,10,15,20-Tetrakis-(1-pyrenyl)porphyrinato(2-)]zinc(II) 5.²⁶

A

mixture of the above [10,20-bis-bromo-5,15-bis-(1-pyrenyl)-

porphyrinato(2-)]zinc(II) (400 mg, 0.429 mmol), cesium carbonate

156

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The Journal of Organic Chemistry

Article

(1.45 g, 10 equiv.), Pd(PPh₃)₄(50 mg, 10 mol %), pyridine (2 mL)

and 4,4,5,5-tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane (310 mg,

0.95 mmol, 2.2 equiv.) in toluene (150 mL) was degassed and refluxed

under nitrogen for 12 h. Reaction mixture was cooled and passed

consecutively through pads of Celite, silica gel and neutral alumina

washing with toluene. Toluene was distilled off in vacuum, the residue

was separated by column chromatography on silica gel (gradient

elution with hexanes−ethyl acetate 1000:10 to 800:200) to afford

[5,10,15,20-tetrakis-(1-pyrenyl)porphyrinato(2-)]zinc(II)²⁶5 (260 mg,

(∼0.2 μTorr). Aluminum (Alfa Aesar; 99.999%) was used as received.

Glass substrates commercially coated with ITO (thickness: 1500

100 Å, sheet resistance: 20 5 Ω/cm², transmission: 84% at 550 nm)

were purchased from Thin Film Devices Inc.

Film Growth and Characterization. Device substrates were

solvent cleansed and placed in an ozone atmosphere for 10 min

immediately before loading into the high vacuum (∼3 μTorr)

deposition chamber. Layer thicknesses and deposition rates were

monitored by a quartz crystal microbalance calibrated using

monochromatic or spectroscopic ellipsometry. Materials were

sequentially grown by vacuum thermal evaporation at the following

rates: C₆₀(2−4 Å/s), BCP (2 Å/s), Al (5 Å/s), porphyrin 2d (1−2 Å/s).

The base pressure during deposition of porphyrin 2d was 1−5 ×

10⁻⁵Torr due to partial decomposition of organic material.

Condensed phase optical measurements were performed on solvent-

cleansed glass, quartz, or polished silicon substrates using an Agilent

8453 spectrophotometer and a Photon Technology International

fluorimeter.

Device Characterization. Current−voltage measurements were

performed in ambient conditions using a SourceMeter in the dark

and under corrected 1000 Wm²⁻white light illumination from a 300

W xenon arc lamp. Spectral mismatch correction was performed as

described in the literature^39,46using a silicon photodiode, calibrated at

the National Renewable Energy Laboratory (NREL), and frequency

modulated illumination (250 Hz) from a Xe source coupled to a 1/4

M monochromator in conjunction with an Lock-In amplifier. This

monochromatic system was also used to collect all external quantum

efficiency data.

1

0.22 mmol, 50%). H NMR (5% pyridine-d₅in CDCl₃, 500 MHz,

mixture of atropoisomers): 7.21−7.30 (m, 2H), 7.35 and 7.39 (d, 2H,

J = 10 Hz, atropoisomers), 7.45−7.63 (m, 6H), 7.91−8.00 (m, 8H),

8.18 and 8.27 (d, 8H, J = 10 Hz, atropoisomers), 8.20−8.23 (m, 4H),

8.35−8.40 (m, 10H), 8.71−8.85 (m, 4H). ¹H NMR (5% pyridine-d₅in

CDCl₃, 125 MHz): (118.56, 118.58, 118.61, 118.63 − atropoisomers);

122.3, 123.6, 124.5, 124.9, 125.2, 126.0; (127.01, 127.04, 127.09,

127.15 − atropoisomers); (127.25, 127.27, 127.33, 127.35 −

atropoisomers); 127.5, 130.6, 130.9, 131.6, 131.88, 131.90, 131.93,

131.97, 132.01, 132.42, 132.46, 132.50, 132.54, 132.60, 133.10, 133.14,

133.20, 133.25, 133,28, 133.35, 138.2; (150.92, 150.94, 150.95, 150.97 −

atropoisomers). UV/vis (5%-pyridine in CH₂Cl₂) λ, nm, (ε): 606

(12286), 566 (29395), 441 (461248), 337 (100582), 323 (93953).

MALDI TOF: 1172.60 (M⁺), requires 1172.29 for C₈₄H₄₄N₄Zn.

HRMS: 1173.2915 (MH⁺), calcd. 1173.2930 for C₈₄H₄₅N₄Zn.

[3,5,8,10,13,15,18,20-Tetrakis-(1,10-pyrenyl)porphyrinato(2-)]-

zinc(II) 5t. (mixture of regioisomers). The above porphyrin 5*MeOH

(50 mg, mmol) in a glass boat was placed into a glass tube. The tube

was purged with nitrogen and kept under positive nitrogen

atmosphere. The tube was placed into furnace preheated to 560 °C

and kept there for 5 min under nitrogen atmosphere. First, the furnace

temperature rose to 560 °C in 1−2 min and after additional ca. 1−2

min starting material melted. Reaction mixture turned dark and the

bubbles appeared. After ca. 0.5 min the tube was taken out from the

furnace and cooled to room temperature under nitrogen. The crude

mixture was dissolved in dichloromethane (100 mL) with addition of

pyridine (10 mL, sonication is required for dissolving crude reaction

mixture) and separated on silica gel column (elution with dichloro-

methane−pyridine 1000:10 mixture). Compound 5t was crystallized

from dichloromethane-pyridine by layered addition of methanol. Yield:

ASSOCIATED CONTENT

■

S

* Supporting Information

¹H and ¹³C NMR and mass spectra for compounds 1−4, 2-H,

2-Mg, 2-Cu, 2-Pb, 2-Pt, 2d, 3d, 5; cyclic voltammetry traces for

2, 2m and 2d, details of molecular modeling studies, including

optimized geometries performed on model compounds 1d′−

4d′ and π-extended analogs. This material is available free of

charge via the Internet at http://pubs.acs.org.

1

15 mg, 30%. H NMR (dilute solution in 5%-pyridine-d₅in C₆D₆,

AUTHOR INFORMATION

75 °C, 600 MHz, signal assignment for possible regioisomers could

not be done, longer acquisition time required, signal broadening due

to aggregation): 7.63 (d, 4H, J = 8 Hz), 7.74−7.84 (m, 12H), 7.88−

7.97 (m, 16H), 8.03 (d, 4H, J = 9 Hz). UV/vis (5% pyridine in

CH₂Cl₂) λ, nm (ε): 1003 (13954), 873 (43861), 813 (30458), 620

(73072), 576 (70842). MALDI-TOF MS (without matrix): 1164.32

(M⁺), requires 1164.22 for C₈₄H₃₆N₄Zn. Peak of the molecular ion

could not be obtained by using ESI/APCI MS. ¹³C NMR (5%

pyridine-d₅in C₆D₆, 125 MHz, weak signals): 124.0, 125.07, 125.10,

125.17, 126.10, 126.15, 126.8, 127.4, 127.5, 128.9, 129.6, 129.9, 131.6.

Thermal Fusion of Metalated Pyrenyl-porphyrins 2-M. The

corresponding porphyrin 2-M in a glass boat was placed into a glass

tube. The tube was purged with nitrogen and kept under positive

nitrogen atmosphere. The tube was placed in a furnace preheated to

530 °C (M = Mg, Cu, Pb) or 560 °C (M = Pt, Pd,) and kept there for

4−10 min. Starting material melts, turns brown with appearance of

bubbles. After additional ca. 0.5 min after melting of the material the

tube was taken out from the furnace and cooled to room temperature

under nitrogen. UV−vis near IR absorption spectra (see main text,

Figure 6e) of crude reaction mixtures demonstrate nearly quantitative

conversion of starting porphyrinic material into doubly fused products.

Mass spectra of the crude mixtures indicated formation of doubly

fused products. 2d-Cu: HRMS: 1143.4449 (MH⁺), calcd. 1143.4500

for C₈₀H₆₅N₄Cu. 2d-Mg: HRMS: 1104.4953 (M⁺), calcd. 1104.4976

for C₈₀H₆₄N₄Mg. 2d-Pd: MADLI TOF: 1186,10 (M⁺), calcd. 1186.42

for C₈₀H₆₄N₄Pd. 2d-Pt: HRMS: 1276.4859 (MH⁺), calcd. 1276.4852

for C₈₀H₆₅N₄Pt.

■

Corresponding Author

*met@usc.edu

ACKNOWLEDGMENTS

■

We acknowledge Drs. Matthew Whited and Peter Djurovich for

helpful discussion. The Department of Energy, Office of Basic

Energy Sciences as part of Energy Frontier Research Center

program, the Center for Energy Nanoscience (DE-SC0001013)

are acknowledged for support of the OPV studies of compound

2d (C.W.S. and J.D.Z.). We also acknowledge the NSF SOLAR

program (Award ID 0934098, S.R.F and Q.Z.), Universal

Display Corporation, Global Photonic Energy Corporation and

the Center for Advanced Molecular Photovoltaics (CAMP)

(KUS-C1-015-21) of the King Abdullah University of Science

and Technology (KAUST) for financial support of the other

science presented here.

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Porphyrins fused with unactivated polycyclic aromatic hydrocarbons

DOI: 10.1021/jo201490y

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