Molecular engineering of boryl oxasmaragdyrins through peripheral modification: Structure-efficiency relationship

DOI: 10.1002/chem.201405856

Full Paper

&

Dye-Sensitized Solar Cells

Molecular Engineering of Boryl Oxasmaragdyrins through

Peripheral Modification: Structure–Efficiency Relationship

[

a]

Sandeep B. Mane and Chen-Hsiung Hung*

Abstract: Expanded porphyrins with the absorption profile

down to the infrared region through increased p-conjuga-

tion are suitable candidates for a low energy sensitizer. Oxa-

smaragdyrin boron complexes, a class of aromatic-core-

modified expanded porphyrin with 22p-electrons, have

been recently utilized as an efficient low energy sensitizer in

dye-sensitized solar cells. In this paper, we have prepared

a series of eight novel boryl oxasmaragdyrins through mo-

lecular engineering on the periphery and their overall photo-

voltaic performances in dye-sensitized solar cells are evaluat-

ed. With the help of photophysical, electrochemical, and

photovoltaic studies, it is revealed that molecular structure,

especially the number and position of the donor–acceptor

groups play a pivotal role in their photovoltaic performance.

Presence of the two well-separated split Soret bands in the

400–500 nm region of UV/Vis spectrum ensures broader cov-

erage of absorption wavelengths. Even though the two-an-

choring-group dyes (SM5–SM8) bind strongly to TiO com-

2

pared to one-anchoring-group dyes (SM1–SM4), the latter

have superior photovoltaic performance than the former.

Dye SM1, with two hexyloxyphenyl donors and one carbox-

ylic acid anchor showed the best overall conversion efficien-

ꢀ

2

cy of 4.36% (J =10.91 mAcm ; V_O_C=0.59 V; FF=0.68).

SC

This effective modulation of photovoltaic performance

through structural engineering of the dyes will serve as

a guideline for the future design of efficient low energy

light-harvesting sensitizers.

Introduction

studied extensively. A D–p–A-type porphyrin sensitizer that

has long alkyl chains on the ortho-position of meso phenyl

rings to overcome the aggregation, obtained the overall con-

Huge dependence on fossil fuels is not only causing geopoliti-

cal tensions but also damaging the environment severely.

These economic and environmental concerns have encouraged

researchers to explore alternative renewable sources of energy

that could replace fossil fuels. Solar energy is the most lavish,

clean, and renewable energy source that could also be har-

nessed in remote areas. The dye-sensitized solar cell (DSSC), in-

[5]

version efficiency of 13% with cobalt electrolyte. Although

[5–6]

these porphyrins gave the best efficiencies,

the longer syn-

thetic steps and very low overall yields are the major disadvan-

tages that hinder their commercial applications. Therefore, to

find the best porphyrin sensitizer, other porphyrinoids, such as

[

7]

[8]

[9]

chlorins (8%), bactriochlorins (6.6%), corroles (1.6%),

[

1]

[10]

[11]

vented by Grꢀtzel and co-workers in 1991, is one of the most

studied solar energy alternatives for this purpose due to its ad-

vantages like low production cost, easy fabrication, and com-

parable overall conversion efficiencies with conventional silicon

solar cells. Several factors such as sensitizer properties, elec-

trode materials, and the electrolyte determine the photovoltaic

phthalocyanines (5.5%),

subphthalocyanines (1.3%), and

[12]

core-modified porphyrins (1.7%) have also been screened.

Recently, we have shown that boron–oxasmaragdyrin SM0

(Figure S1 in the Supporting Information), an aromatic core-

modified expanded porphyrin can serve as an efficient sensitiz-

[13]

er for DSSCs with an overall conversion efficiency of 5.7%.

[

2]

performance of DSSCs. Among these factors, the sensitizer

plays a very important role, particularly in the overall power

conversion and cell stability. A large number of organic mole-

cules have been synthesized and used as sensitizers in DSSCs.

One of the advantages of this expanded porphyrin is that it

can be prepared just in three steps from readily available start-

ing compounds in an 18% overall yield that is much higher

than the reported yield for push–pull porphyrins (~1%). In this

paper we report our efforts to modify the oxasmaragdyrin ring

with long alkoxy chains on the meso-position, different donor

and linker groups, and reversal of the electron flow by chang-

ing the position of carboxylic acid anchors. We have designed

and synthesized eight boryl oxasmaragdyrin molecules with

various substituents on the periphery, and their structures are

presented in Scheme 1. The dyes SM1 and SM2 consist of

p-hexyloxyphenyl and hexyl thiophene groups, whereas dye

SM3 is decorated with an electron-donating triphenylamine

(TPA) group and one p-carboxyphenyl group on the meso-posi-

[

2]

[3]

Among them, ruthenium dyes, organic dyes, and porphyri-

[

4]

noids are top performers with overall efficiencies in the range

of 11–13%. Out of the various porphyrinoids used in DSSCs,

the regular porphyrins with a push–pull structure have been

[a] Dr. S. B. Mane, Dr. C.-H. Hung

Institute of Chemistry, Academia Sinica

Nankang, Taipei, 11529 Taiwan (Taiwan)

E-mail: chhung@gate.sinica.edu.tw

Supporting information for this article is available on the WWW under

http://dx.doi.org/10.1002/chem.201405856.

Chem. Eur. J. 2015, 21, 1 – 18

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Scheme 1. Boryl oxasmaragdyrin sensitizers with varied donor and anchor groups for DSSCs.

tion. In the dye SM4, p-conjugation of the oxasmaragdyrin

ring was extended with an ethynylphenyl bridging unit at the

meso-position between the oxasmaragdyrin ring and the termi-

nal carboxylic acid anchoring group. The concept of reversal of

electron flow was materialized by swapping the positions of

donor and anchor groups in dye SM1. The dyes SM5, SM6,

and SM7 were prepared with two p-carboxyphenyl groups as

anchors and thiophene carbazole, p-hexyloxyphenyl, and tolyl

groups as donors on the meso-positions. The possibility of up-

surge in electron transport on replacing the electron-withdraw-

ing fluoride atoms with electron-rich ethoxy groups on the

boron atom was examined in dye SM8.

that were further reacted with excess pyrrole in the presence

of boron trifluoride–diethyl etherate as the catalyst to yield

meso-aryl-16-oxatripyrranes 5–7. The oxasmaragdyrins were

prepared by the “3+2” MacDonald-type condensation of meso-

carbonylphenyldipyrromethane 1 with meso-aryl-16-oxatripyr-

ranes 5–7 under mild acidic conditions followed by subse-

quent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoqui-

none (DDQ) to afford the meso-substituted oxasmaragdyrins

8–10. These free-base oxasmaragdyrins were further treated

with excess triethylamine (NEt ) followed by boron trifluoride–

3

diethyl etherate (BF ·OEt ) at room temperature to give boron-

3

2

chelated oxasmaragdyrins 11–13. After basic workup these

boryl oxasmaragdyrins were chromatographed to the purest

possible form at this stage so as to avoid the purification in

the last step. These monoester boryl oxasmaragdyrins were hy-

drolyzed with an aqueous solution of KOH to yield analytically

pure oxasmaragdyrins as green solids in decent yields. To pre-

pare SM4 (Scheme 3), one equivalent of paraformaldehyde

was treated with excess pyrrole in the presence of TFA to

obtain the meso-unsubstituted dipyrromethane 14. The meso-

tolyl-16-oxatripyrrane 16 was prepared by following the syn-

thetic pathway for oxatripyrrane 5. The meso-unsubstituted

oxasmaragdyrin is assembled by treating the dipyrromethane

14 and the tripyrrane 16 under acidic conditions followed by

subsequent oxidation with DDQ which was further treated

with excess NEt and BF ·OEt at room temperature to give

Results and Discussion

Syntheses of SM dyes

SM dyes are synthesized in the least possible steps with mini-

mum application of tedious coupling reactions starting with

the key precursors dipyrromethane and 16-oxatripyrrane. The

assembly of the oxasmaragdyrins SM1–SM3 and their boron

chelation is displayed in Scheme 2. One equivalent of methyl-

4-formylbenzoate was treated with excess pyrrole in the pres-

ence of trifluoroacetic acid (TFA) as an acid catalyst to obtain

the meso-carbonylphenyldipyrromethane 1 in good yield. For

oxatripyrrane, furan was treated with the corresponding alde-

hydes in the presence of nBuLi to get symmetrical furan diols

3

2

boron-chelated oxasmaragdyrin 17 in 3% yield as shown in

&

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Scheme 2. Synthesis of oxasmaragdyrin dyes SM1–SM3: i) TFA; ii) nBuLi, TMEDA, hexane/THF; iii) pyrrole, BF

BF ·OEt , dichloromethane; vi) KOH (aq.), THF.

3

·OEt

2

3

; iv) TFA, DDQ, dichloromethane; v) NEt ,

3

2

Scheme 3. After standard workup and chromatographic purifi-

cation, the oxasmaragdyrin 17 was isolated as green solid. This

meso-unsubstituted oxasmaragdyrin 17, is then brominated

with N-bromosuccinamide (NBS) at low temperature to give

the bromo-substituted boryl oxasmaragdyrin 18. This meso-

bromo boryl oxasmaragdyrin was reacted with 4-ethynylbenzo-

ic acid at 608C under Sonogashira coupling protocol to give

the desired SM4 in good yield. The boryl oxasmaragdyrins

SM5–SM8 were prepared following the same synthetic path-

way used for SM1–SM3 as presented in Scheme 4. The meso-

aryldipyrromethanes 19–21 were prepared in decent yield by

treating one equivalent of corresponding aldehydes with

excess pyrrole in the presence of TFA as the catalyst. Furan

was treated with methyl-4-formylbenzoate in the presence of

nBuLi to get a symmetrical diol that was further reacted with

excess pyrrole in the presence of BF ·OEt to yield meso-(4-me-

ragdyrins were purified by column chromatography to afford

the pure product. These diester oxasmaragdyrins were hydro-

lyzed with an aqueous solution of KOH to yield analytically

pure oxasmaragdyrins SM5–SM8 as green solids in decent

yield. All these boryl oxasmaragdyrins along with their inter-

mediates were thoroughly characterized by common analytical

1

13

11

19

techniques, such as H, C, B, F NMR spectroscopy, UV/Vis

spectroscopy, cyclic voltammetry, HRMS spectroscopy, and ele-

mental analysis.

Optical properties

The UV/Vis peak positions of the Soret and Q bands and the

molar extinction coefficients (e) of the oxasmaragdyrins in THF

are summarized in Table 1. The absorption spectra of these

oxasmaragdyrins display split Soret bands in the 445–500 nm

region and Q bands in the 550–750 nm region as shown in

Figure 1. Evidently, the split Soret band covers a broader range

of absorption wavelengths than regular porphyrins and

BODIPY dyes. Additionally, the Q bands, which are more in-

tense than those for typical porphyrins are mainly contributed

from the HOMO to LUMO transition. The absorption wave-

lengths of these oxasmaragdyrins depend largely on the

nature of the substituents. In monocarboxylic acid substituted

oxasmaragdyrins, the addition of an electron-donating hexyl-

thiophene group in SM2 and triphenylamine group in SM3

3

2

thoxyphenyl)-16-oxatripyrrane 23. The oxasmaragdyrins 24–26

were prepared by following the “3+2” MacDonald-type con-

densation protocol of meso-aryldipyrromethanes 19–21 with

the 16-oxatripyrrane 23 under mild acidic conditions followed

by succeeding oxidation with DDQ. These free-base oxasmar-

agdyrins were further treated with excess NEt and BF ·OEt at

3

2

room temperature to give boron-chelated oxasmaragdyrins

7–29. The BF oxasmaragdyrin 29 was further treated with

2

excess ethanol in the presence of AlCl to give the B(OEt) -che-

3

2

lated oxasmaragdyrin 30. After regular workup, the oxasma-

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Scheme 3. Synthesis of oxasmaragdyrin dyes SM4: i) TFA; ii) nBuLi, TMEDA, hexane/THF; iii) pyrrole, BF

BF ·OEt , dichloromethane; v) NBS, THF; vi) 4-ethynylbenzoic acid, [Pd (dba) ], AsPh , toulene/NEt

3

·OEt

2

3

; iv) a) TFA, DDQ, dichloromethane; b) NEt ,

3

2

3

.

Scheme 4. Synthesis of oxasmaragdyrin dyes SM5–SM8: i) TFA; ii) nBuLi, TMEDA, hexane/THF; iii) pyrrole, BF

BF ·OEt , dichloromethane; vi) EtOH, AlCl , dichloromethane; vii) KOH (aq.), THF.

3 2 3

·OEt ; iv) TFA, DDQ, dichloromethane; v) NEt ,

3

2

3

redshifted the absorption wavelengths by 3–6 nm compared

to SM1, while the coupling of ethynylphenyl linker in SM4 ex-

hibited the highest bathochromic shift of 15 nm for the Soret

band compared to SM1. The absorption onset in dye SM4

reached beyond 750 nm, which indicates that the light har-

vesting for this dye might be high in visible as well as in the

near IR (NIR) region. In dicarboxylic acid substituted oxasma-

ragdyrins, the substitution of electron-donating thiophene car-

bazole unit on the oxasmaragdyrin ring in SM5, bathochromi-

cally shifted the absorption in Soret as well as Q band region,

extending the absorption onset beyond 750 nm. The broad-

ened absorption is beneficial as increased light harvesting can

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nature of ethoxy group has negligible influence on the optical

properties of this dye. The high molar extinction coefficients

Table 1. Photophysical and electrochemical data for SM dyes.

[

a]

[b]

[c]

[d]

[e]

5

ꢀ1

Dye

l

max [nm]

l

em [nm]

Eox [V]

E

(0,0) [eV]

E* [V]

(1.65–4.38ꢂ10 m cm ) for SM1–SM8 also supports the prop-

osition of a good light harvesting nature of these dyes. To

better comprehend the adsorption behavior of the dyes on

ox

3

ꢀ1

(

e [10 m cm ])

SM1

SM2

SM3

SM4

SM5

SM6

SM7

SM8

446 (438), 474

719

723

743

726

705

710

0.82

0.88

0.86

0.88

0.90

0.87

0.88

0.73

1.75

1.74

1.68

1.72

1.77

1.76

ꢀ0.93

ꢀ0.87

ꢀ0.88

ꢀ0.80

ꢀ0.82

ꢀ0.90

ꢀ0.89

ꢀ1.03

(

181), 706 (57)

452 (261), 477

108), 704 (23)

449 (186), 477

103), 708 (31)

461 (186), 497

51), 737 (44)

452 (165), 478

100), 712 (38)

446 (254), 473

118), 699 (33)

445 (271), 472

124), 698 (32)

449 (228), 477

104), 700 (27)

TiO , absorption spectra of these dyes as thin films were stud-

2

ied and the results are displayed in Figure 2. To obtain the ab-

(

[

a] In THF. [b] Emission maximum measured in THF by exciting at Soret

+

band. [c] First oxidation potential vs. NHE in THF calibrated with Fc/Fc

couple. [d] Estimated from the intersection of the absorption and emis-

sion spectra. [e] Approximated from Eox and E(0,0)

.

Figure 2. UV/Vis spectra of SM dyes adsorbed on TiO . a) c: SM1; a:

2

SM2; g: SM3; d: SM4; b) c: SM5; a: SM6; g: SM7; d: SM8.

sorption spectra on TiO₂films, the films with approximately

3

mm thickness were immersed in 0.1 mm THF solution of the

SM dyes at room temperature. The adsorption spectra were re-

corded by reflectance measurements using an integrated

sphere. The absorption spectra of dyes show significant broad-

ening and slight redshifts upon adsorption on the TiO surface

2

compared to their UV/Vis spectra in THF with threshold of ab-

sorption around 800 nm. This broadening and significant red-

shifts in the UV/Vis spectra after adsorption on TiO films sug-

2

gest highly efficient charge collection in Soret and Q band

region which in turn may result in higher efficiency in DSSCs.

The steady-state fluorescence spectra of these dyes were mea-

sured in THF by excitation at Soret band wavelengths and is

shown in Figure S2 (see the Supporting Information). It re-

vealed a similar trend to the UV/Vis spectra with slight redshift

in the wavelengths due to the increased p-conjugation

through donor and linker variations.

Figure 1. UV/vis spectra of SM dyes in THF. a) c: SM1; a: SM2; g:

SM3; d: SM4; b) c: SM5; a: SM6; g: SM7; d: SM8.

improve the photocurrent density. Changing the number and

position of the hexyloxyphenyl and carboxylic acid in SM6

compared to SM1 did not have any effect on the absorption

spectrum. Ethoxy substitution on the boron atom in case of

dye SM8 as compared to dye SM7 slightly red-shifted the ab-

sorption spectrum. This suggests that the electron-donating

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Electrochemical properties

tives. It is also observed from the energy level diagram that

the difference between the ground-state oxidation potential of

SM8 and the redox potential of the electrolyte is 0.29 V, which

is not sufficient to regenerate the oxidized dye. The LUMOs for

all of the oxasmaragdyrins are more negative than the TiO₂

conduction band (>0.3 V), which ensures the adequate driving

Suitable matching of HOMOs with the electrolyte for a prompt

regeneration of oxidized dye and the LUMOs with the conduc-

tion band of TiO for an efficient electron injection is impor-

2

tant. The cyclic voltammetry measurements of all the boryl

oxasmaragdyrins were carried out in degassed THF containing

force for the electron injection from dye to the TiO conduc-

2

0

.1m tetrabutylammonium hexafluorophosphate as the sup-

tion band. The HOMO of all the oxasmaragdyrins except SM8

are more positive (>0.3 V) than the redox electrolyte, which

confirms the efficient dye regeneration. This might be one of

the reasons for the inferior efficiency of dye SM8. Overall, the

band gap analysis suggests that the energy gaps and the

HOMO–LUMO potentials of these dyes are suitable for DSSC

application.

porting electrolyte under a scan rate of 50 mV to obtain the

first oxidation potentials. As depicted in Figure S3 (see the

Supporting Information), two reversible oxidation couples and

one reversible reduction couple were observed for SM1, SM2,

and SM5, whereas one reversible oxidation and one reversible

reduction couple was observed for SM3, SM4, SM6, SM7, and

SM8. In monocarboxylic acid substituted oxasmaragdyrins, the

oxidation potentials for SM2, SM3, and SM4 are more positive

than that of the SM1, which indicates that they are harder to

be oxidized. The oxidation potentials of the dicarboxylic acid

substituted oxasmaragdyrins SM5, SM6, and SM7 are larger by

DFT calculations

To correlate the molecular structures of dyes with the per-

formance of DSSCs, we carried out DFT as well as time-depen-

dent DFT (TD-DFT) calculations at the B3LYP/6-31G level of

theory using a suite of Gaussian 9 software. The results from

theoretical calculations show planar macrocycles for all studied

dyes as depicted in Figure 4. From the MO analyses, the fluo-

ride and ethoxy substituents, which lie on opposite sides of

the boryl oxasmaragdyrin ring do not affect the electron distri-

bution along the ring. The planar ring ensures the effective

coupling of the electron between the donor and acceptor

groups. In the HOMO of all the SM dyes, the electron density is

largely located on the oxasmaragdyrin ring, while a small part

of it is distributed over donor unit. This also indicates the insig-

nificant influence of the donor groups on the p-conjugation of

the oxasmaragdyrin ring. In the LUMO of the monocarboxylic

acid substituted oxasmaragdyrins SM1–SM4, the electron den-

sity is equally distributed over the oxasmaragdyrin ring and

the carboxyphenyl anchor, revealing effective charge separa-

tion in these molecules. Whereas in the LUMO of the dicarbox-

ylic acid substituted oxasmaragdyrins SM5–SM8, the electron

density is still mainly located over the oxasmaragdyrin ring,

which suggests the charge separation is less efficient. Negligi-

ble charge delocalization in the LUMO orbital, even with the

push–pull system in dyes SM5–SM8, which suggests inefficient

electron injection from the LUMO level. In LUMO+2 of all the

SM dyes, the electron density is completely localized on the

carboxyphenyl anchoring group highlighting the probability of

electron injection from higher excited states involving LUMO+

5

0–80 mV than that of SM8 and larger by 90 mV than that of

SM1. The ethoxy substitution on boron center in SM8 resulted

in a negative shift in the oxidation potential by 150 mV com-

pared with SM7, consistent with the similar observation report-

[

13]

ed previously. The zero–zero excitation energies, E₍₀_,₀₎were

calculated from the intersection of the normalized absorption

and emission spectra at the Q (0,0) band and are shown in

Table 1. The excited-state oxidation potentials were estimated

from the first oxidation potentials and the zero–zero excitation

energies and are listed in Table 1. The systematic energy level

diagram for the studied oxasmaragdyrin dyes is displayed in

the Figure 3. As evident from the energy level diagram, for the

monocarboxylic acid substituted boryl oxasmaragdyrins, the

addition of hexylthiophene group did not change the band

gap, while the TPA (SM3) donor unit lowered the band gap

slightly. An obvious decrease in the band gap is observed for

SM4 due to the increased conjugation through the ethynyl-

phenyl linker. However in dicarboxylic acid substituted oxa-

smaragdyrins, incorporation of an electron-rich thiophene–car-

bazole unit reduced the energy gap compared to other deriva-

2. These quantum mechanical calculations again emphasize

that, the molecular design with two donors and one anchoring

group is more effective than the reverse, with two anchoring

groups and one donor. From the comparison between the ox-

asmaragdyrins with and without ethynylphenyl, it is observed

that the population of electron density on the carboxyphenyl

acceptor group in LUMO is decreased when the distance be-

tween the oxasmaragdyrin ring and the acceptor group is in-

creased. The TD-DFT results obtained for the studied boryl oxa-

smaragdyrins are summerized in Table S1 (see the Supporting

Information). For all the compounds, the lowest energy transi-

tion (S !S ) is approximately 72–85% of the HOMO!LUMO

Figure 3. Energy level diagram for SM dyes.

0

1

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and listed in Table 2. Significant-

ly higher molecular dipole

moment was observed for SM1

than the rest of the dyes. The

higher polarizability is expedi-

ent to accelerate the intramo-

lecular photoinduced charge

transfer. We also carried out

Mullikan charge analysis for

three representative molecules

namely, SM1, SM4, and SM7, to

understand the reason behind

the best performance of SM1

than the other dyes. We calcu-

lated the amount of electron

density located on carboxy-

phenyl anchor (CA) and rest of

the boryl oxasmaragdyrin (Sm)

and summerized them in

Tabel S2 in the Supporting In-

formation. The electron density

localized on CA anchor in the

LUMO orbital of SM1 is way

much higher than SM4 and

SM7, which means that due to

higher electron density available

on the anchoring group of SM1

in the LUMO orbital, the charge

injection might be higher.

ATR-FTIR measurements

To probe the number and mode

of attachment of carboxylate

groups onto TiO₂, ATR-FTIR

spectroscopy has been utilized

as one of the imperative

[14]

tools. The ATR-FTIR spectra of

neat oxasmaragdyrins are con-

trasted with spectra of oxasmar-

agdyrins adsorbed on TiO₂for

comparison. Comparative spec-

tra of representative samples

are shown in Figure 5. The spec-

tra of neat SM1, with one an-

choring group show a strong

ꢀ

1

n(C=O) stretch at n=1687 cm ,

ꢀ

whereas n

(COO ) and n

sym

asym

ꢀ

(

COO ) stretches are likely to be

observed at about n=1413 and

ꢀ

1

603 cm , respectively. The

spectra of neat SM6, which has

two anchoring groups show

strong n(C=O) stretches at n=

Figure 4. Molecular orbital diagram for SM dyes.

ꢀ

1

ꢀ

transition, thus confirming its donor to acceptor charge-trans-

fer character. The dipole moments for the oxasmaragdyrins

under study were estimated from the theoretical calculations

1685 and 1730 cm , whereas n

(COO ) and n

(COO )

asym

sym

stretches are likely to be observed at about n=1423 and

ꢀ

1

1605 cm , respectively. In the comparative spectra of SM1/

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TiO₂and SM6/TiO , the n(C=O) stretches completely disap-

2

Table 2. Photovoltaic characteristics of DSSCs incorporating the boryl

oxasmaragdyrin dyes.

peared, accompanied by a noticeable rise in the stretching

ꢀ

peaks of n (COO ) and n

(COO ) at about n=1400 and

asym

sym

ꢀ

2

Dye

J

SC [mAcm

]

V

OC [V]

FF [%]

h [%]

Dipole moment

ꢀ1

1

600 cm . The observation noted above indicates that for

SM1

SM2

SM3

SM4

SM5

SM6

SM7

SM8

10.91

7.16

5.16

4.65

3.95

6.22

5.67

2.32

0.59

0.56

0.52

0.49

0.53

0.54

0.53

0.47

68

67

65

66

71

69

68

61

4.36

2.74

1.79

1.49

1.48

2.33

2.05

0.66

6.6132

5.1484

5.2209

6.5527

3.9259

4.7692

6.0501

5.5281

SM1, anchoring onto TiO is achieved through one carboxyl

group while in SM6, both p-carboxyphenyl groups at the cis

2

positions are used for anchoring onto TiO . Based on the

2

above analyses, the single-anchoring mode for SM1–SM4 and

dual-anchoring mode for SM5–SM8 are proposed for the at-

tachment of the oxasmaragdyrins onto TiO₂.

Dye-loading measurements

To better comprehend the adsorption behavior and measure

the amount of adsorbed dye, we calculated the dye densities

adsorbed on TiO₂surface. The oxasmaragdyrin densities (G)

were determined by measuring the absorbance of the oxa-

smaragdyrins desorbed from the sensitized TiO₂films after

being immersed in 0.1m KOH solution in THF. The dye densi-

ties for two carboxyphenyl-substituted oxasmaragdyrins were

higher than their one carboxyphenyl-substituted counterparts.

For one acceptor series, the dye loadings were found as 109(ꢁ

ꢀ

2

3

), 113(ꢁ6), 153(ꢁ8), and 119(ꢁ3) nmolcm for SM1, SM2,

SM3, and SM4, respectively. Even though SM1 has lower dye

loading compared to other three derivatives, the better solubil-

ity and the larger charge separation due to higher dipole

moment may be responsible for its increased short circuit cur-

rent density and consequently the higher overall conversion

efficiency. Whereas for SM3, higher dye loading was observed,

but lower dipole moment and therefore lower charge separa-

tion may be the reason for its lower efficiency. For two accept-

or series, the dye densities were found as 168(ꢁ9), 183(ꢁ7),

ꢀ

2

1

73(ꢁ6), and 114(ꢁ4) nmolcm for SM5, SM6, SM7, and

SM8, respectively. Even though SM7 has higher dipole

moment than SM6, the higher solubility of SM6 due to alkoxy

chain and the similar dye loading may be responsible for its in-

creased short-circuit current density and consequently the

higher overall conversion efficiency. The dye loading trends in

these two acceptor series are alike with higher dye loading re-

sulting in increased power conversion efficiency.

Photovoltaic measurements

The boryl oxasmaragdyrins shown in Scheme 1 were evaluated

as sensitizers in DSSC devices, assembled with the opaque

active TiO layer on FTO glass as photoanode using iodide/

2

triiodide as electrolyte and tested under standard AM 1.5 illu-

mination conditions. The detailed information about the

device preparation was described in general techniques. The

best photovoltaic performances for each oxasmaragdyrin dye

are summarized in Table 2. The Jsc refers to short-circuit photo-

current density, Voc is open-circuit photo-voltage, FF is fill

factor and h is solar-to-electrical conversion efficiency. The op-

timized I–V characteristics of the devices measured under stan-

dard AM 1.5G simulated solar conditions are displayed in

Figure 6. As seen from the I–V curves, the device prepared

with SM1 obtained highest short-circuit current of

Figure 5. ATR-FTIR spectra of a) SM6 (c) and SM6/TiO

b) SM1 (c) and SM1/TiO

yrins on TiO are normalized for comparison. c) Possible modes of attach-

ment of oxasmaragdyrins onto TiO . For demonstration purposes only, the

nanoparticles are not correlated in

2

(d) and

2

(d); the ATR-FTIR spectra of the oxasmaragd-

2

relative sizes of the molecules and TiO

real dimensions.

2

&

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device performance assembled with the dye SM1. The finest

photovoltaic performance among the two carboxyphenyl

series was displayed by SM6, with an overall photon-to-current

ꢀ

2

conversion efficiency of 2.33% along with J_S_Cof 6.22 mAcm ,

V_O_Cof 0.54 V, and fill factor of 69%. The effect of electron-do-

nating thiophenecarbazole group is well evident in the optical

spectrum of SM5 but the dipole moment is only 3.9 D, which

indicates that the electron donors near the boron center are

not very effective.

Also the same effect is observed from the dipole moments

of other oxasmaragdyrins SM6 (4.7 D) and SM7 (6 D). The

stronger the electron-donating substituent at meso-position

near the boron center, the lower is the dipole moment. The

dye SM5 provided the overall photon-to-current conversion ef-

ꢀ

2

ficiency of 1.48% along with J_S_Cof 3.95 mAcm , V of 0.53 V,

OC

and fill factor of 71%, whereas the oxasmaragdyrin SM7 ach-

ieved the photon-to-current conversion efficiency of 2.05%

ꢀ

2

alongside the J_S_Cof 5.67 mAcm , V of 0.53 V, and fill factor

OC

of 68%. Superior solubility due to the addition of long alkoxy

chains and higher dye loading of SM6 might be responsible

for its increased photovoltaic conversion than dye SM7, in

spite of having higher dipole moment. We also tuned the elec-

tronic environment near the boron center to check its conse-

quence on the photovoltaic performance with replacement of

the electron-withdrawing fluoride atoms attached to boron

with electron-donating ethoxy groups. This alteration resulted

in decreased device performance for dye SM8, which attained

Figure 6. I–V characteristics of SM dyes under 1 sun illumination. a) c:

SM1; a: SM2; g: SM3; d: SM4; b) c: SM5; a: SM6; g: SM7;

d: SM8.

ꢀ

2

a minimal efficiency of 0.66% with J_S_Cof 2.32 mAcm , V of

OC

ꢀ

2

1

0.91 mAcm , in combination with an open-circuit voltage of

.59 V and fill factor of 68%, collectively corresponding to the

0.47 V, and fill factor of 61%.

0

best photon-to-current conversion efficiency of 4.36%. Under

similar experimental conditions the dye SM0 with tolyl substi-

tution gave the overall efficiency of 4.26% based on Jsc of

ꢀ

2

1

2.19 mAcm , V of 0.51 V and fill factor of 68%. The cell as-

OC

sembled with SM2 attained the overall conversion efficiency of

ꢀ2

2

.74%, well reinforced by J_S_Cof 7.16 mAcm , V of 0.56 V and

OC

fill factor of 67%. The DSSC assembled with SM3 exhibited an

ꢀ

2

efficiency of 1.79% with Jsc of 5.16 mAcm , V of 0.52 V and

OC

fill factor of 65%. The donor TPA group substitution resulted in

inferior J_S_Cand V_O_Cvalues signifying its insignificant effect on

the efficiency of SM3 compared with SM1. In SM4, incorpora-

tion of the ethynylphenyl linker between the oxasmaragdyrin

ring and the acceptor group did not show any improvement

in the DSSC performance, which might be due to the increased

distance of the anchoring group from the oxasmaragdyrin

ring. The redshifted absorption profile and the near equal

dipole moments compared with SM1 were also not helpful for

the efficiency improvement for SM4, which gained overall effi-

ꢀ

2

ciency of 1.49% supported with J_S_Cof 4.65 mAcm , V of

OC

0.49 V and fill factor of 66%. The two-acceptor derivatives with

the reversed molecular design were evaluated for the DSSC

performance and compared with SM1. We assumed that the

direction of electron flow away from the boron center with the

aid of two acceptors and the strong p-conjugation of the oxa-

smaragdyrin ring shall contribute to enhance the photovoltaic

performance. To our disappointment the best performance of

these two-anchoring group dyes reached merely half of the

Figure 7. IPCE characteristics of SM dyes under 1 sun illumination. a) c:

SM1; a: SM2; g: SM3; d: SM4; b) c: SM5; a: SM6; g: SM7;

d: SM8.

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The trends in the J_S_Cfor these oxasmaragdyrins

can be observed from the variation of incident

photon-to-current conversion efficiency (IPCE) plots

of these dyes as shown in Figure 7.

The IPCE spectra of all the dyes are in qualitative

agreement with the corresponding absorption spec-

tra of the dyes on TiO which shows intense absorp-

2

tion in both Soret as well as Q band regions. The su-

perior performance of SM1 can be understood from

its IPCE spectrum, which exhibits a high plateau in

the l=380 to 550 nm region with IPCE reaching

30% at l=425 nm, whereas it also displayed another

intense peak in the l=550 to 750 nm region with

the IPCE value of 25% at l=703 nm. The intensity of

the dip between l=550–600 nm for SM1 is still

higher than other oxasmaragdyrins with an IPCE

value of 15%. The dye SM1 shows panchromatic ab-

sorption feature covering whole l=380–750 nm

region. The other oxasmaragdyrins follow the parallel

pattern in the IPCE spectra but with inferior IPCE

values. The IPCE spectrum for oxasmaragdyrin SM6

exhibits a high plateau in the l=380 to 550 nm

region, with IPCE reaching 19% at 425 nm. It also dis-

played another intense peak in the l=550 to

Figure 8. Electrochemical impedance spectra (Nyquist plots) of DSSCs based on SM dyes

measured in the dark. a)

: SM8.

&

: SM1; *: SM2; ~: SM3; !: SM4. b) : SM5; *: SM6; ~: SM7;

&

!

7

50 nm region with the IPCE value of 12% at l=

00 nm. Interestingly, the IPCE spectra of SM5 cover

7

extended absorption region with the onset reaching

around 800 nm, but its lower IPCE values in the

higher energy region results in lower conversion effi-

ciency. Collectively, higher charge separation due to

larger dipole moment, higher charge density local-

ized in LUMO orbitals, panchromatic absorption fea-

ture, higher IPCE and higher J_S_Chave contributed to

the higher efficiency of dye SM1 compared to other

SM dyes.

EIS measurements

The DSSCs based on the boryl oxasmaragdyrins were

Figure 9. Electrochemical impedance spectra (Nyquist plots) of DSSCs based on SM dyes

further characterised by electrochemical impedance measured under 1 sun illumination. a)

&

: SM1; *: SM2; ~: SM3; !: SM4. b)

: SM5; *:

&

SM6; ~: SM7; !: SM8.

spectroscopy (EIS) to reveal important interfacial

charge-transfer processes in DSSCs. The impedence

spectroscopy was carried out by subjecting the cells

to both dark and illumination conditions. Figure 8 shows the

EIS Nyquist plot (i.e., minus imaginary part of the impedance,

the recombination resistance. Figure 9 shows the EIS Nyquist

ꢀ

2

plot upon illumination of 100 mWcm under open-circuit con-

ditions. The radius of the intermediate frequency semicircle in

the Nyquist plot under illumination conditions reflects the

ꢀ

Z“, versus the real part of the impedance, Z”, when sweeping

the frequency in the range of 0.1 Hz to 1 MHz) under a forward

bias of ꢀ0.55 V in the dark. For all the studied cells we ob-

served one semicircle in the intermediate frequency range.

This semicircle in the Nyquist plot in dark condition represents

[15]

electron-transport resistance, which means the smaller the

radius of the semicircle, the smaller is the electron-transport re-

sistance. The electron transport resistance for the oxasmarag-

dyrins with one anchoring group decreases in the order,

SM4>SM2>SM3>SM1, while for the oxasmaragdyrins with

two anchoring groups, it decreases in the order SM8>SM5>

SM6ꢂSM7. These EIS results are more or less consistant with

the overall efficiencies of these boryl oxasmaragdyrin dyes.

the charge-transfer phenomenon between the TiO surface

2

[

2]

and the electrolyte, that is, recombination resistance. The re-

combination resistance (size of the semicircle) for the oxasma-

ragdyrins with one anchoring group decreases in the order

SM1>SM4>SM3>SM2, while for the oxasmaragdyrins with

two anchoring groups, it decreases in the order SM7>SM6>

SM5>SM8. The larger the size of the semicircle, the smaller is

&

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standard and the potential values obtained in reference to the

silver electrode were converted to NHE. The DFT and TD-DFT calcu-

lations were performed with Gaussian 09 package to study the

electron distribution of the frontier molecular orbitals and the pho-

toexcitation transitions. All ground-state geometries of oxasmarag-

dyrins were optimized in the gas phase by the hybrid B3LYP func-

tional and the 6-31G basis set, and the TD-DFT calculation were

based on the same functional and basis set. The molecular orbitals

were visualized by the Chem-office software. The EIS instrument in-

volves the chemical electric impedance analyser (CHI 621B electro-

chemical analyser) with applied AC voltage and bias potential on

the cells and measured the corresponding current and voltage

under the white LED lamp with various neutral density filters to

change the illumination white light intensity in order to change

the fermi level of DSCs. In addition, we used the Z-view program

to analyze the data.

Conclusions

We have engineered the molecular structure of boryl oxasmar-

agdyrins in an attempt to enhance their photovoltaic perform-

ances. We have synthesized eight novel boryl oxasmaragdyrins

decorated with different number and position of donor and

anchor groups and evaluated their performance as sensitizers

in DSSCs. All eight boryl oxasmaragdyrins displayed good ab-

sorption features in both Soret as well as Q band regions. Al-

though the substitution of electron-donating groups and ex-

tension of p-conjugation through ethynylphenyl group obvi-

ously resulted in redshifted and broadened absorption wave-

lengths, it has insignificant effect on their photovoltaic per-

formance. The swapping of position and increased number of

anchoring groups resulted in stronger binding with TiO but

2

exhibited very minor influence on their DSSC outcomes. Cyclic

voltammetry measurements and DFT calculations confirmed

the viability of electron injection and intramolecular charge

transfer. Among these dyes, one anchor dye SM1-sensitized

cell gave the finest DSSC performance with an overall photon-

to-current conversion efficiency of 4.36%, while the device

made from two anchor dye SM6 obtained an efficiency of

Synthesis

General procedure A for dipyrromethane: A mixture of aldehyde

(1 equiv) and pyrrole (100 equiv) was degassed with N for 15 min.

2

at room temperature. TFA (0.1 equiv) was then added and the mix-

ture was stirred at room temperature for 3 h. After completion of

the reaction, NaOH (3 equiv) was added and mixture was stirred

for 1 h and then filtered. The filtrate was concentrated and pyrrole

was removed under vacuum. The crude obtained after removing

pyrrole was subjected to silica gel column chromatography using

dichloromethane/hexanes (4:6) as the eluting solvent to obtain the

desired dipyrromethane.

2.33%. From these photovoltaic results it is clear that the mo-

lecular design of SM1 still prevails over all other modifications.

Experimental Section

General procedure B for furan diol: Furan (1 equiv) was added to

a solution of nBuLi (2.5 equiv) and tetramethylethylenediamine

General techniques and materials

(

TMEDA) (2.5 equiv) in dry hexane (40 mL) under N . The reaction

2

All chemicals were obtained from commercial sources and used as

received without further purification. All the reactions were carried

out under a nitrogen atmosphere. Solvents used in reactions were

dried by PureSolv MD 5 system (Innovative Technology, Inc). Flash

chromatography was carried out by using basic alumina (63–

mixture was heated at reflux temperature for 1 h and then cooled

to 08C. A precooled solution of the corresponding aldehyde

(

sion. After the addition was complete, the mixture was warmed up

to room temperature while stirring for 30 min. Saturated NH Cl so-

lution was added to quench the reaction. The organic phase was

extracted with H O, brine, and then dried over MgSO . The crude

product was subjected to silica gel column chromatography using

ethyl acetate/hexanes (3:7) as the eluting solvent to give the de-

sired furan diol.

2 equiv) in dry THF (60 mL) was added dropwise to this suspen-

4

2

00 mm, Merck) and silica gel (40–63 mm, Merck). Analytical TLC

1

13

was performed on Merck silica gel plates. H and C NMR spectra

were recorded on a Bruker 400 MHz spectrometer and performed

2

4

in CDCl (d=7.26 ppm) and [D8]THF (d=1.73, 3.58 ppm) solutions.

3

11

19

B and F NMR spectra were recorded on a DRX 500 MHz spec-

trometer. Chemical shifts are reported in ppm. Coupling constants

J are reported in Hz. The signals are described as s: singlet; d: dou-

blet; dd: doublet of doublet. The ESI ion trap mass spectra were

measured by a Finnigan MAT LCQ mass spectrometer. The HR-FAB

spectra were conducted on a JMS-700 double focusing mass spec-

trometer. MALDI-mass spectra were conducted on an Applied Bio-

systems 4800 Proteomics Analyzer (Applied Biosystem, Foster City)

equipped with an Nd/YAG laser (335 nm). Transmittance and reflec-

tion UV/Vis absorption spectra of the oxasmaragdyrins in THF and

adsorbed on TiO₂electrodes, respectively, were recorded on

a JASCO V-670 UV/Vis/NIR spectrophotometer. Steady-state fluores-

cence spectra were acquired by using a Varian Cary Eclipse fluores-

cence spectrophotometer. The cyclic voltammetry measurements

of all oxasmaragdyrins were carried out on CHI 621B electrochemi-

cal analyser (CH Instruments, Austin, TX, USA) in degassed THF

containing 0.1m tetrabutylammonium hexafluorophosphate

General procedure C for 16-oxatripyrrane: Furan-diol (1 equiv)

was dissolved in pyrrole (40 equiv) under N . BF ·OEt (1 equiv) was

2

3

2

added to this solution. The mixture was stirred for 30 min at room

temperature. After completion of reaction as confirmed by TLC

analysis, the reaction was quenched by adding aq. NaOH (0.1n,

2

0 mL). The mixture was extracted with dichloromethane and

washed with water. The organic layer was dried over MgSO and

4

excess pyrrole was removed under vacuum. The crude oil was puri-

fied by column chromatography on silica using dichloromethane/

hexanes (3:7) as the eluting solvent to give pure oxatripyrrane.

General procedure D for “3+2” Macdonald condensation: Dipyr-

romethane (1 equiv) and 16-oxatripyrrane (1 equiv) were dissolved

in dichloromethane (700 mL) and stirred under nitrogen for

10 min. The reaction was initiated by adding TFA (0.1 equiv) and

the stirring was continued for 90 min. DDQ (3 equiv) was then

added and the reaction mixture was stirred in open-air for an addi-

tional 90 min. The solvent was removed and the crude compound

was purified by basic alumina column chromatography eluted with

dichloromethane/hexanes (3:7) to get the desired free-base ox-

asmaragdyrin as a green solid.

(

Bu NPF ) as the supporting electrolyte. The cell assembly consists

4 6

of a glossy carbon as the working electrode, a silver wire as the

pseudo-reference electrode, and a platinum wire as the auxiliary

electrode. The scan rate for all measurements was fixed at

ꢀ1

+1/0

5

0 mVsec . A ferrocene

redox couple was used as the internal

Chem. Eur. J. 2015, 21, 1 – 18

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General procedure E for BF chelation: Oxasmaragdyrin (1 equiv)

HRMS-ESI: m/z: calcd for C H N O : 577.3430; found: 577.3434

[MꢀH] .

2

38 45

2

3

ꢀ

was dissolved in CH Cl (80 mL) and triethylamine (40 equiv) was

2

added at room temperature. After 10 min, BF ·OEt (50 equiv) was

3

2

5

,10-Di(5-hexylthiophen-2-yl)-16-oxatripyrrane (6): Oxatripyrrane

added and the stirring was continued for 30 min. Completion of

the reaction was confirmed by TLC analysis. The reaction mixture

was washed thoroughly with 0.1m NaOH solution and water. The

6

was prepared from furan diol 3 by following general procedure C

(

1.28 g, 46% yield). R =0.32 (DICHLOROMETHANE/hexanes 3:7);

f

1

H NMR (400 MHz, CDCl ) d=0.91 (m, 6H, CH ), 1.34 (m, 12H, CH ),

3

2

organic layers were combined, dried over MgSO , filtered, and the

4

1

2

.65 (m, 4H, CH ), 2.75 (m, 4H, -CH ), 5.60 (s, 2H, meso-CH), 6.05 (s,

2 2

H, b-pyrrole), 6.09 (d, 2H, b-furan), 6.15 (m, 2H, b-pyrrole), 6.60

solvent was removed. The crude compound was purified by silica

gel column chromatography, using dichloromethane/hexanes (3:2)

to afford the desired compound as a green solid.

(

m, 4H, b-thiophene), 6.67 (m, 2H, a-pyrrole), 8.16 ppm (brs, 2H,

13

NH); C NMR (100 MHz, CDCl ): d=14.05, 22.54, 28.82, 30.20,

3

General procedure F for hydrolysis: BR -oxasmaragdyrin (1 equiv)

was dissolved in THF (50 mL). KOH (20 equiv) dissolved in water

31.53, 31.59, 39.69, 106.80, 107.52, 108.15, 108.19, 117.35, 123.34,

125.03, 125.09, 130.57, 141.34, 141.54, 145.41, 154.27, 154.35 ppm.

2

(

1 mL) was added and the resulting mixture was refluxed for 12 h.

5

,10-Di[4-(diphenylamino)phenyl]-16-oxatripyrrane (7): Oxatri-

After cooling, the solvent was removed under vacuum. To the

crude product, dichloromethane was added and extracted with 1n

HCl. The organic layer was dried over MgSO₄and concentrated.

Crude product was purified by silica gel column chromatography

using CH Cl /MeOH (9.5:0.5) as the eluent to give the desired prod-

pyrrane (7) was prepared from furan diol 4 by following general

procedure C (0.65 g, 46% yield). R =0.26 (dichloromethane/hex-

f

1

anes 3:7); H NMR (400 MHz, CDCl ): d=5.37 (s, 2H, meso-CH), 5.95

3

(s, 2H, b-pyrrole), 6.01 (s, 2H, b-furan), 6.15 (m, 2H, b-pyrrole), 6.67

2

(

m, 2H, a-pyrrole), 7.00 (m, 8H, Ar), 7.06 (m, 12H, Ar), 7.23 (m, 8H,

uct as a green solid.

13

Ar), 8.05 ppm (brs, 2H, NH); C NMR (100 MHz, CDCl ): d=43.66,

3

5

-(p-Methoxycarbonylphenyl) dipyrromethane (1): Dipyrrome-

107.10, 107.81, 108.22, 117.24, 122.77, 123.82, 124.19, 128.99,

129.21, 131.14, 134.84, 146.68, 147.70, 154.99 ppm.

thane 1 was prepared from methyl-4-formylbenzoate by following

general procedure A (4.8 g, 86% yield). R =0.2 (dichloromethane/

f

1

9-(p-Methoxycarbonylphenyl)-5,10-di(p-hexyloxyphenyl)-25-

1

hexanes 4:6); H NMR (400 MHz, CDCl ): d=3.91 (s, 3H, CH ), 5.53

3

oxasmaragdyrin (8): 5-(p-methoxycarbonylphenyl)dipyrromethane

and 5,10-di(p-hexyloxyphenyl)-16-oxatripyrrane were reacted by

following the general procedure D (350 mg, 41% yield). R =0.31

(

6

s, 1H, meso CH), 5.89 (s, 2H, b-pyrrole), 6.16 (m, 2H, b-pyrrole),

.72 (m, 2H, a-pyrrole), 7.28 (m, 2H, Ph), 7.98 ppm (m, 4H, Ph,

f

1

3

NH); C NMR (100 MHz, CDCl ): d=43.97, 52.08, 107.50, 108.57,

1

3

(dichloromethane/hexanes 3:7); H NMR (400 MHz, CDCl ): d=1.01

3

1

17.54, 128.41, 129.91, 131.58, 147.34 ppm.

,5-Bis(p-hexyloxyphenyl)furandiol (2): Furan diol 2 was prepared

from p-hexyloxybenzaldehyde by following general procedure B

(m, 6H, CH ), 1.48 (m, 8H, CH ), 1.66 (m, 4H, CH ), 2.01 (m, 4H,

3

2

CH ), 4.11 (s, 3H, -OMe), 4.28 (m, 4H, -OCH ), 7.33 (d, 4H, J=

2 2

8.24 Hz, Ar), 8.11 (d, 4H, J=8.20 Hz, Ar), 8.50 (m, 6H, Ar, b-pyrrole),

8.84 (s, 2H, b-furan), 8.94 (d, 2H, J=4.28 Hz, b-pyrrole), 9.43 (d, 2H,

J=4.28, b-pyrrole), 9.58 ppm (d, 2H, J=4.24 Hz, b-pyrrole);

1

(

8.68 g, 65% yield). R =0.22 (ethyl acetate/hexanes 3:7); H NMR

f

(

400 MHz, CDCl ) d=0.91 (m, 6H, CH ), 1.34 (m, 8H, CH ), 1.45 (m,

3

2

13

4

H, CH ), 1.78 (m, 4H, CH ), 2.66 (brs, 2H, -OH), 3.95 (m, 4H,

C NMR (100 MHz, CDCl ): d=14.13, 22.72, 25.94, 29.51, 31.74,

3

2

-

OCH ), 5.72 (s, 2H, meso-CH), 5.94 (d, 2H, J=3.84 Hz, b-furan), 6.87

52.37, 68.38, 105.01, 113.67, 115.74, 118.98, 119.72, 123.30, 124.21,

124.98, 127.56, 128.75, 129.29, 129.75, 134.40, 134.70, 135.70,

138.09, 145.23, 149.25, 159.18, 167.50 ppm; HRMS-ESI: m/z: calcd

2

13

(

m, 4H, Ar), 7.31 ppm (m, 4H, Ar); C NMR (100 MHz, CDCl ): d=

3

1

4.01, 22.58, 25.70, 29.21, 31.57, 68.04, 69.73, 107.94, 107.99,

14.36, 127.95, 132.59, 156.24, 158.99 ppm.

,5-Bis(5-hexylthiophene-2-yl)furandiol (3): Furan diol 3 was pre-

+

for C H N O : 851.4172; found: 851.4169 [M+H] .

55

4

5

2

19-(p-Methoxycarbonylphenyl)-5,10-di(5-hexylthiophen-2-yl)-25-

oxasmaragdyrin (9): 5-(p-methoxycarbonylphenyl)dipyrromethane

and 5,10-di(5-hexylthiophen-2-yl)-16-oxatripyrrane were reacted

pared from 5-hexylthiophene-2-carbaldehyde by following general

procedure B (9.95 g, 78% yield). R =0.21 (ethyl acetate/hexanes

3

f

1

:7); H NMR (400 MHz, CDCl ): d=0.89 (m, 6H, CH ), 1.33 (m, 12H,

following the general procedure D (250 mg, 30% yield). R =0.31

3

f

CH ), 1.65 (m, 4H, CH ), 2.77 (m, 4H, CH ), 2.85 (brs, 2H, ꢀOH), 5.93

(dichloromethane/hexanes 3:7); this crude oxasmaragdyrin was

used for the next reaction without further purification and data

collection.

2

(

s, 2H, meso-CH), 6.22 (s, 2H, b-furan), 6.62 (m, 2H, Ar), 6.81 ppm

1

3

(

m, 2H, Ar); C NMR (100 MHz, CDCl ): d=14.02, 22.53, 28.76,

3

1

0.18, 31.52, 31.56, 66.38, 107.98, 108.00, 123.44, 123.46, 125.21,

41.23, 141.26, 146.54, 155.09 ppm.

1

9-(p-Methoxycarbonylphenyl)-5,10-di[4-(diphenylamino)phen-

yl]-25-oxasmaragdyrin (10): 5-(p-methoxycarbonylphenyl) dipyrro-

methane and 5,10-di[4-(diphenylamino)phenyl]-16-oxatripyrrane

were reacted following the general procedure D (270 mg, 27%

2

,5-Bis[4-(diphenylamino)phenyl]furandiol (4): Furan diol 4 was

prepared from triphenylamine aldehyde by following general pro-

cedure B (3.86 g, 23% yield). R =0.32 (ethyl acetate/hexanes 3:7);

yield). R =0.34 (dichloromethane/hexanes 3:7); this crude oxasmar-

agdyrin was used for the next reaction without further purification

and data collection.

f

1

H NMR (400 MHz, CDCl ): d=5.77 (s, 2H, meso-CH), 6.10 (d, 2H,

3

J=2.84 Hz, b-furan), 7.07 (m, 20H, Ar), 7.28 ppm (m, 8H, Ar);

1

3

C NMR (100 MHz, CDCl ): d=69.89, 108.03, 122.97, 123.47, 124.42,

3

BF -[19-(p-methoxycarbonylphenyl)-5,10-di(p-hexyloxyphenyl)-

2

1

27.71, 129.26, 134.53, 147.66, 147.78, 156.24 ppm.

2

5-oxasmaragdyrin] (11): Boryl oxasmaragdyrin 11 was prepared

5

,10-Di(p-hexyloxyphenyl)-16-oxatripyrrane (5): Oxatripyrrane 5

from oxasmaragdyrin 8 by following general procedure E (508 mg,

64% yield). R_f=0.42 (dichloromethane/hexanes 3:2); H NMR

1

was prepared from furan diol 2 by following general procedure C

1

(

1.4 g, 58% yield). R =0.28 (dichloromethane/hexanes 3:7); H NMR

(400 MHz, CDCl ): d=ꢀ3.96 (t, 2H, ꢀNH), 1.03 (m, 6H, CH ), 1.51 (s,

f

3

(

400 MHz, CDCl ): d=0.91 (m, 6H, CH ), 1.34 (m, 8H, CH ), 1.46 (m,

8H, CH ), 1.68 (m, 4H, CH ), 2.04 (m, 4H, CH ), 4.17 (s, 3H, OMe),

2 2 2

3

2

4

H, CH ), 1.77 (m, 4H, CH ), 3.93 (m, 4H, ꢀOCH ), 5.34 (s, 2H, meso-

4.32 (m, 4H, OCH ), 7.41 (d, 4H, J=7.48 Hz, Ar), 8.30 (d, 4H, J=

2

CH), 5.89 (m, 2H, b-pyrrole), 5.93 (d, 2H, J=2.12 Hz, b-furan), 6.12

7.40 Hz, Ar), 8.64 (d, 2H, J=7.56 Hz, Ar), 8.70 (d, 2H, J=7.68 Hz,

Ar), 9.05 (d, 2H, b-pyrrole), 9.54 (s, 2H, b-furan), 9.57 (d, 2H, b-pyr-

role), 10.24 (d, 2H, b-pyrrole), 10.33 ppm (d, 2H, b-pyrrole);

(

m, 2H, b-pyrrole), 6.63 (m, 2H, a-pyrrole), 6.82 (m, 4H, Ar), 7.09

13

(

m, 4H, Ar), 7.97 ppm (brs, 2H, NH); C NMR (100 MHz, CDCl ): d=

3

1

13

1

4.02, 22.59, 25.73, 29.25, 31.58, 43.48, 68.04, 106.99, 107.69,

08.16, 114.45, 117.11, 129.31, 131.48, 132.61, 155.22, 158.17 ppm;

B NMR (160.4 MHz, CDCl₃): d=ꢀ12.78 ppm (brs);

C NMR

(125 MHz, CDCl ): d=14.14, 22.74, 25.96, 29.52, 31.76, 52.46, 68.43,

3

&

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

12

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ÝÝ These are not the final page numbers!

Full Paper

1

06.82, 113.56, 117.01, 120.43, 120.95, 122.14, 123.80, 123.87,

25.04, 129.47, 129.56, 130.41, 130.94, 131.41, 134.55, 134.82,

35.36, 144.04, 150.12, 159.37, 167.45 ppm; F NMR (470.5 MHz,

91% yield). R_f=0.2 (dichloromethane/MeOH 9.5:0.5); H NMR

(400 MHz, [D ]THF): d=ꢀ3.79 (t, 2H, NH), 1.03 (m, 6H, CH ), 1.52

8

3

19

(m, 8H, CH ), 1.69 (m, 4H, CH ), 2.07 (m, 4H, CH ), 3.26 (m, 4H,

2 2 2

CDCl₃): d=ꢀ149.22 ppm (brs); HRMS-FAB+: m/z: calcd for

CH ), 7.38 (d, 2H, J=3.24 Hz, b-thiophene), 7.99 (d, 2H, J=3.32 Hz,

2

+

C H BF N O : 898.4077; found: 898.4084 [M] .

b-thiophene), 8.66 (d, 2H, J=8.00 Hz, Ar), 8.74 (d, 2H, J=8.00 Hz,

Ar), 9.28 (d, 2H, J=3.96 Hz, b-pyrrole), 9.63 (d, 2H, J=4.40 Hz, b-

pyrrole), 9.83 (s, 2H, b-furan), 10.42 (d, 2H, J=3.16 Hz, b-pyrrole),

5

53

2

4

5

BF -[19-(p-methoxycarbonylphenyl)-5,10-di(5-hexylthiophene-2-

2

yl)-25-oxasmaragdyrin] (12): Boryl oxasmaragdyrin 12 was pre-

pared from oxasmaragdyrin 9 by following general procedure E

1

[

0.51 ppm (d, 2H, J=4.48 Hz, b-pyrrole); B NMR (160.4 MHz,

13

D ]THF): d=ꢀ10.79 ppm (brs); C NMR (125 MHz, [D ]THF): d=

(

300 mg, 62% yield). R =0.42 (dichloromethane/hexanes 3:2);

8

f

1

14.56, 23.67, 30.08, 31.36, 32.77, 33.08, 100.51, 119.14, 121.71,

H NMR (400 MHz, CDCl ): d=ꢀ3.85 (t, 2H, NH), 1.03 (m, 6H, CH ),

3

1

23.58, 124.76, 125.10, 125.38, 125.85, 130.59, 131.79, 132.17,

32.73, 134.15, 135.69, 141.61, 144.24, 149.61, 151.46, 167.98 ppm;

1

.51 (s, 8H, CH ), 1.67 (m, 4H, CH ), 2.05 (m, 4H, CH ), 3.23 (m, 4H,

2 2 2

CH ), 4.17 (s, 3H, OMe), 7.31 (d, 2H, J=3.28 Hz, b-thiophene), 7.95

2

1

9

F NMR (470.5 MHz, [D ]THF): d=ꢀ147.53 ppm (brs); UV/Vis (THF):

(

d, 2H, J=3.24 Hz, b-thiophene), 8.64 (d, 2H, J=8.20 Hz, Ar), 8.68

d, 2H, J=8.24 Hz, Ar), 9.05 (m, 2H, b-pyrrole), 9.55 (d, 2H, J=

8

3

ꢀ1

l

max

(e)=452 (261), 477 (108), 704 nm (23·10 m cm ); HRMS-

MALDI: m/z: calcd for C H BF N O S : 864.3151; found: 864.3176

4

1

.48 Hz, b-pyrrole), 9.82 (s, 2H, b-furan), 10.23 (m, 2H, b-pyrrole),

50 47

2

4

3 2

+

11

[M] ;

elemental

analysis

calcd

(%)

for

0.30 ppm (d, 2H, J=4.44 Hz, b-pyrrole); B NMR (160.4 MHz,

13

C H BF N O S ·0.2C H 0.8CH Cl : C 65.75, H 5.43, N 5.89; found:

CDCl ): d=ꢀ12.59 ppm (brs); C NMR (125 MHz, CDCl ): d=14.18,

50 47

2

4

3

2

6

13

2

3

C 65.59, H 5.49, N 5.85.

BF -{19-(p-carboxyphenyl)-5,10-di[4-(diphenylamino)phenyl]-25-

oxasmaragdyrin} (SM3): Dye SM3 was prepared by hydrolysis of

BF -oxasmaragdyrin 13 by following general procedure F (2 mg,

61% yield). R

(400 MHz, CDCl

2

1

2.72, 29.08, 30.63, 31.74, 31.94, 52.47, 99.89, 117.65, 120.52,

20.97, 122.35, 123.58, 123.97, 124.28, 125.24, 129.50, 129.72,

30.89, 131.07, 131.63, 133.01, 134.76, 140.56, 143.83, 148.83,

50.59, 167.41 ppm; F NMR (470.5 MHz, CDCl ): d=ꢀ149.04 ppm

2

1

9

3

2

1

(

brs); HRMS-MALDI: m/z: calcd for C H BF N O S : 878.3307;

f

=0.35 (dichloromethane/MeOH 9.5:0.5); H NMR

) d=ꢀ3.97 (t, 2H, NH), 7.20 (m, 4H, Ar), 7.49 (m,

6H, Ar), 7.60 (d, 4H, J=8.28 Hz, Ar), 8.28 (d, 4H, J=8.32 Hz, Ar),

51

49

2

4

3 2

+

found: 878.3331 [M] .

3

1

BF -{19-(p-methoxycarbonylphenyl)-5,10-di[4-(diphenylamino)-

2

8

4

.76 (s, 4H, Ar), 9.18 (d, 2H, J=3.52 Hz, b-pyrrole), 9.62 (d, 2H, J=

.36 Hz, b-pyrrole), 9.68 (s, 2H, b-furan), 10.29 (dd, 2H, J=2.96, b-

phenyl]-25-oxasmaragdyrin} (13): Boryl oxasmaragdyrin 13 was

prepared from oxasmaragdyrin 10 by following the general proce-

11

pyrrole), 10.38 ppm (d, 2H, J=4.44 Hz, b-pyrrole);

B NMR

C NMR (100 MHz,

dure E (380 mg, 64% yield). R =0.47 (dichloromethane/hexanes

f

13

1

(160.4 MHz, CDCl₃) d=ꢀ12.72 ppm (brs);

3

:2); H NMR (400 MHz, CDCl ): d=ꢀ3.93 (t, 2H, NH), 4.18 (s, 3H,

3

CDCl ): d=106.98, 116.84, 120.54, 121.02, 122.01, 122.30, 123.44,

3

OMe), 7.21 (m, 4H, Ar), 7.50 (m, 16H, Ar), 7.58 (d, 4H, J=8.32 Hz,

Ar), 8.24 (d, 4H, J=8.36 Hz, Ar), 8.64 (d, 2H, J=8.28 Hz, Ar), 8.68 (d,

1

23.93, 125.03, 128.60, 129.59, 130.14, 130.43, 130.78, 131.45,

35.01, 135.26, 136.08, 144.96, 147.92, 148.01, 150.07, 170.96 ppm;

2

1

H, J=8.28 Hz, Ar), 9.15 (dd, 2H, J=1.80 Hz, b-pyrrole), 9.56 (d,

H, J=4.48 Hz, b-pyrrole), 9.64 (s, 2H, b-furan), 10.24 (dd, 2H, J=

.91 Hz, b-pyrrole), 10.32 ppm (d, 2H, J=4.44 Hz, b-pyrrole);

1

9

F NMR (470.5 MHz, CDCl ): d=ꢀ149.19 ppm (brs); UV/Vis (THF):

3

ꢀ1

l

max

(e)=449 (186), 477 (103), 708 nm (31·10 m cm ); HRMS-

11

13

MALDI: m/z: calcd for C H BF N O : 1018.3615; found: 1018.3642

66 45 2 6 3

B NMR (160.4 MHz, CDCl₃): d=ꢀ12.62 ppm (brs);

C NMR

+

[

M] ;

elemental

analysis

calcd

(%)

for

(

125 MHz, CDCl ): d=52.45, 106.92, 117.12, 120.44, 120.90, 122.01,

3

C H BF N O ·0.9C H 1CH Cl : C 73.66, H 5.01, N 7.11; found: C

66

45

2

6

3

6

13

2

1

22.17, 123.42, 123.91, 125.01, 129.47, 129.58, 130.47, 130.73,

31.46, 134.81, 135.23, 136.08, 144.01, 147.91, 147.97, 150.04,

7

3.66, H 5.11, N 7.06.

1

9

67.43 ppm; F NMR (470.5 MHz, CDCl ): d=ꢀ149.12 ppm (brs);

Di(1H-pyrrol-2-yl)methane (14): Dipyrromethnae (14) was pre-

pared from paraformaldehyde by following general procedure A at

3

HRMS-MALDI: m/z: calcd for C H BF N O : 1032.3771; found:

1

67

47

2

6

3

+

032.3798 [M] .

508C (1.8 g, 62% yield). R

f

=0.34 (dichloromethane/hexanes 4:6);

1

H NMR (400 MHz, CDCl ): d=3.97 (s, 2H, meso-CH ), 6.05 (s, 2H, b-

3

2

BF -[19-(p-carboxyphenyl)-5,10-di(p-hexyloxyphenyl)-25-oxa-

2

pyrrole), 6.16 (s, 2H, b-pyrrole), 6.65 (s, 2H, a-pyrrole), 7.80 ppm

smaragdyrin] (SM1): Dye SM1 was prepared by hydrolysis of BF₂-

1

3

(

brs, 2H, ꢀNH); C NMR (100 MHz, CDCl ): d=26.38, 106.33,

3

oxasmaragdyrin 11 by following general procedure F (177 mg,

1

106.39, 117.21, 129.01 ppm.

9

1% yield). R_f=0.2 (dichloromethane/MeOH 9.5:0.5); H NMR

2

,5-Bis(p-tolyl)furandiol (15): Furan diol 15 was prepared from p-

(

400 MHz, [D ]THF): d=ꢀ3.92 (t, 2H, NH), 1.03 (m, 6H, CH ), 1.53

8

3

tolaldehyde by following general procedure B (2.47 g, 58% yield).

m, 12H, CH ), 2.04 (m, 4H, CH ), 4.35 (m, 4H, OCH ), 7.47 (d, 4H,

2

1

R =0.2 (ethyl acetate/hexanes 3:7); H NMR (400 MHz, CDCl ): d=

J=8.44 Hz, Ar), 8.33 (d, 4H, J=8.36 Hz, Ar), 8.66 (d, 2H, J=7.88 Hz,

Ar), 8.76 (d, 2H, J=7.96 Hz, Ar), 9.04 (d, 2H, J=3.84 Hz, b-pyrrole),

9

2

f

3

2

.36 (s, 6H, Me), 2.42 (brs, 2H, OH), 5.75 (d, 2H, meso-CH), 5.96 (d,

13

b-furan), 7.16 (d, 4H, Ar), 7.30 ppm (d, 4H, Ar); C NMR (100 MHz,

CDCl ): d=21.15, 69.99, 108.04, 108.11, 126.61, 129.12, 137.83,

.59 (s, 2H, b-furan), 9.65 (d, 2H, J=4.44 Hz, b-pyrrole), 10.44 (d,

H, J=3.16 Hz, b-pyrrole), 10.53 ppm (d, 2H, J=4.32 Hz, b-pyr-

3

11

13

1

56.20 ppm.

role); B NMR (160.4 MHz, [D ]THF): d=ꢀ12.69 ppm (brs); C NMR

8

(

125 MHz, [D ]THF): d=14.57, 23.75, 27.05, 30.60, 32.84, 69.08,

5,10-Di(p-tolyl)-16-oxatripyrrane (16): Oxatripyrrane 16 was pre-

pared from furan diol 15 by following general procedure C

8

1

07.71, 114.49, 118.41, 121.60, 121.72, 123.29, 124.91, 124.96,

25.73, 130.60, 131.61, 131.72, 131.83, 132.51, 135.77, 136.24,

(800 mg, 60% yield). R_f=0.4 (dichloromethane/hexanes 3:7);

19

1

44.55, 151.12, 160.76, 168.04 ppm; F NMR (470.5 MHz, [D ]THF):

H NMR (400 MHz, CDCl ): d=2.37 (s, 6H, Me), 5.39 (s, 2H, meso-

8

3

d=ꢀ149.47 ppm (brs); UV/Vis (THF): l (e)=446 (438), 474 (181),

CH), 5.94 (s, 2H, b-pyrrole), 5.98 (d, 2H, b-furan), 6.16 (m, 2H, b-pyr-

max

3

ꢀ1

7

06 nm (57·10 m cm ); HRMS-FAB+: m/z: calcd for

role), 6.65 (s, 2H, a-pyrrole), 7.13 (m, 8H, Ar), 7.98 ppm (brs, 2H,

+

13

C H BF N O : 884.3921; found: 884.3917 [M] ; elemental analysis

NH); C NMR (100 MHz, CDCl ): d=21.01, 43.83, 107.01, 107.76,

5

4

51

2

4

5

3

calcd (%) for C H BF N O ·0.5CH Cl : C 70.59, H 5.66, N 6.04;

108.11, 117.12, 128.17, 129.16, 131.21, 136.57, 137.74, 155.03 ppm.

5

4

51

2

4

5

2

found: C 70.58, H 5.76, N 6.02.

meso-Free BF -oxasmaragdyrin (17): Dipyrromethane 14 and

2

BF -[19-(p-carboxyphenyl)-5,10-di(5-hexylthiophene-2-yl)-25-oxa-

2

5,10-di(p-tolyl)-16-oxatripyrrane 16 were condensed by following

smaragdyrin] (SM2): Dye SM2 was prepared by hydrolysis of BF₂-

oxasmaragdyrin 12 by following general procedure F (177 mg,

the general procedure D. (R =0.35, dichloromethane/hexanes 3:7)

to give the desired oxasmaragdyrin as a green solid. This pure oxa-

f

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

13

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

&

These are not the final page numbers! ÞÞ

Full Paper

smaragdyrin was used for the next reaction without further purifi-

cation and data collection. Boron chelation of this free-base oxa-

phene), 7.02 (d, 1H, b-thiophene), 7.43 (dd, 2H, J=4.36 Hz, Ar),

7.50 (dd, 2H, J=3.51 Hz, Ar), 8.05 (brs, 2H, ꢀNH), 8.11 ppm (d, 2H,

13

smaragdyrin was achieved by the general procedure E (18 mg, 3%

J=1.56 Hz, Ar); C NMR (100 MHz, CDCl ): d=31.97, 34.73, 39.78,

3

1

yield). R =0.52 (dichloromethane/hexanes 3:2); H NMR (400 MHz,

107.33, 108.57, 109.62, 116.14, 117.70, 123.42, 123.60, 123.82,

f

ꢀ

CDCl ): d=ꢀ4.20 (t, 2H, NH), 2.80 (s, 6H, Tol), 7.70 (d, 4H, J=

124.18, 131.45, 138.28, 140.17, 143.52 ppm; HRMS-ESI : m/z: calcd

3

ꢀ

7

9

2

1

.72 Hz, Ar), 8.30 (d, 4H, J=7.80 Hz, Ar), 9.05 (m, 2H, b-pyrrole),

.54 (s, 2H, b-furan), 9.77 (d, 2H, J=4.36 Hz, b-pyrrole), 10.28 (m,

H, b-pyrrole), 10.37 (d, 2H, J=4.36 Hz, b-pyrrole), 10.65 ppm (s,

for C H N S: 504.2473; found: 504.2478 [MꢀH] .

33

34

3

5

-(p-Hexyloxyphenyl)dipyrromethane (20): Dipyrromethnae 20

was prepared from 4-hexyloxybenzaldehyde by following general

11

H, meso-H); B NMR (160.4 MHz, CDCl ): d=ꢀ12.80 ppm (brs);

3

procedure A (5.57 g, 86% yield). R =0.2 (dichloromethane/hexanes

f

1

3

C NMR (125 MHz, CDCl ): d=21.66, 102.75, 106.74, 120.31, 120.80,

1

3

4

:6); H NMR (400 MHz, CDCl ): d=0.95 (t, 3H, ꢀCH ), 1.38 (m, 4H,

3

1

21.84, 123.46, 124.15, 124.84, 128.27, 130.43, 132.25, 134.31,

ꢀ

CH ), 1.49 (m, 2H, ꢀCH ), 1.80 (m, 2H, ꢀCH ), 3.96 (t, 2H, ꢀOCH ),

2

19

37.89, 139.70, 149.67 ppm; F NMR (470.5 MHz, CDCl₃): d=

149.33 ppm (brs); HRMS-FAB+: m/z: calcd for C H BF N O:

5

.41 (s, 1H, meso-CH), 5.93 (m, 2H, b-pyrrole), 6.18 (m, 2H, b-pyr-

ꢀ

37

27

2

4

role), 6.68 (m, 2H, a-pyrrole), 6.87 (d, 2H, Ar), 7.13 (d, 2H, Ar),

+

5

92.2246; found: 592.2238 [M] .

13

7

.87 ppm (brs, 2H, ꢀNH); C NMR (100 MHz, CDCl ): d=13.99,

3

meso-Bromo BF -oxasmaragdyrin (18): A solution of BF -oxasma-

22.56, 25.69, 29.22, 31.55, 43.09, 68.02, 107.00, 108.32, 114.53,

117.03, 129.30, 132.89, 133.93, 158.07 ppm; HRMS-ESI : m/z: calcd

for C H N O: 321.1967; found: 321.1958 [MꢀH] .

2

ꢀ

ragdyrin 18 (60 mg, 0.1 mmol) in dry THF (20 mL) was treated with

NBS (18 mg, 0.1 mmol), and the reaction mixture was allowed to

stir at ꢀ788C for 30 min initially and continued stirring for addi-

tional 1 h at room temperature. The solvent was removed on

a rotary evaporator under vacuum. The crude compound was puri-

fied by silica gel column chromatography using hexanes/dichloro-

ꢀ

21

25

2

5

-(p-Tolyl)dipyrromethane (21): Dipyrromethnae 21 was prepared

from p-tolylaldehyde by following general procedure A (4.1 g, 86%

1

yield). R =0.18 (dichloromethane/hexanes 4:6); H NMR (400 MHz,

f

CDCl ): d=2.34 (s, 3H, ꢀCH ), 5.44 (s, 1H, meso-CH), 5.93 (s, 2H, b-

3

methane (7:3) and afforded the pure compound as a green solid

pyrrole), 6.16 (m, 2H, b-pyrrole), 6.69 (m, 2H, a-pyrrole), 7.12 (m,

1

(

32 mg, 78% yield). H NMR (400 MHz, CDCl ): d=ꢀ4.05 (t, 2H,

13

3

4

2

1

H, tolyl), 7.92 ppm, (brs, 2H, ꢀNH); C NMR (100 MHz, CDCl ): d=

3

NH), 2.80 (s, 6H, Tol), 7.70 (d, 4H, J=7.72 Hz, Ar), 8.28 (d, 4H, J=

1.00, 43.57, 107.05, 108.37, 117.07, 128.25, 129.31, 132.68, 136.57,

39.03 ppm; HRMS-FAB+: m/z: calcd for C H N : 236.1313;

7

2

.80 Hz, Ar), 9.04 (m, 2H, b-pyrrole), 9.52 (s, 2H, b-furan), 9.89 (d,

H, J=4.48 Hz, b-pyrrole), 10.25 (m, 2H, b-pyrrole), 10.34 ppm (d,

16

2

+

found: 236.1313 [M] .

11

H, J=4.40 Hz, b-pyrrole); B NMR (160.4 MHz, CDCl₃): d=

1

3

2,5-Bis(p-methoxycarbonylphenyl)furandiol (22): Furan diol 22 is

prepared from methyl-4-formylbenzoate by following general pro-

ꢀ

12.90 ppm (brs); C NMR (100 MHz, CDCl ): d=21.66, 97.78,

3

1

07.37, 120.77, 121.29, 122.34, 123.73, 124.18, 125.28, 128.34,

19

cedure B (820 mg, 15% yield). R =0.21 (ethyl acetate/hexanes 3:7);

f

30.60, 130.89, 131.76, 134.29, 138.05, 139.42, 150.08 ppm; F NMR

1

H NMR (400 MHz, CDCl ): d=2.74 (brs, 2H, ꢀOH), 3.91 (s, 6H, ꢀ

3

(

470.5 MHz, CDCl ): d=ꢀ149.25 ppm (brs); HRMS-MALDI: m/z:

3

+

OMe), 5.84 (s, 2H, meso-CH), 5.97 (d, J=6.28 Hz, b-furan), 7.48 (d,

calcd for C H BBrF N O: 670.1351; found: 670.1368 [M] .

3

7

26

2

4

1

3

4

H, J=8.24 Hz, Ar), 8.02 ppm (d, 4H, J=8.24 Hz, Ar); C NMR

meso-4-Ethynylcarboxyphenyl BF -oxasmaragdyrin (SM4): 4-

2

(

100 MHz, CDCl ): d=52.17, 69.54, 108.57, 108.64, 126.52, 129.77,

3

Ethynylbenzoic acid (11 mg, 0.07 mmol) was added to a solution of

1

29.89, 145.29, 155.64, 166.82 ppm.

meso-bromo BF -oxasmaragdyrin 18 (40 mg 0.06 mmol) in toluene/

2

5

,10-Di(p-methoxycarbonylphenyl)-16-oxatripyrrane (23): Oxatri-

triethylamine (3:1), and the mixture was stirred for 15 min under

pyrrane 23 was prepared from furan diol 22 by following general

a N atmosphere. The coupling was initiated by the addition of cat-

2

procedure C (992 mg, 58% yield). R =0.3 (dichloromethane/hex-

f

alytic amounts of [Pd (dba) ] (dba=dibenzylideneacetone; 27 mg,

2

3

1

anes 3:7); H NMR (400 MHz, CDCl ): d=3.91 (s, 6H, ꢀOMe), 5.45 (s,

3

0

.03 mmol) and AsPh₃(64 mg, 0.21 mmol). The reaction mixture

2

(

H, meso-CH), 5.89 (s, 2H, b-pyrrole), 6.00 (d, 2H, b-furan), 6.14 (m,

H, b-pyrrole), 6.67 (m, 2H, a-pyrrole), 7.25 (m, 4H, Ar), 7.96 ppm

was stirred at 608C for 4 h. The solvent was removed on rotary

evaporator under vacuum. The crude product was subjected to

silica gel column chromatographic purification using methanol/di-

13

m, 4H, Ar); C NMR (100 MHz, CDCl ): d=44.25, 52.11, 107.58,

3

1

08.42, 117.69, 128.31, 129.05, 129.87, 129.96, 145.78, 154.43,

chloromethane (5%) to afford the pure compound as a green solid

ꢀ

1

166.82 ppm; HRMS-ESI : m/z: calcd for C H N O : 493.1763;

found: 493.1760 [MꢀH] .

30

25

2

5

(

13 mg, 30% yield). H NMR (400 MHz, [D ]THF): d=ꢀ4.27 (t, 2H,

8

ꢀ

NH), 2.79 (s, 6H, Tol), 7.75 (d, 4H, J=7.72 Hz, Ar), 8.34 (d, 8H, J=

7

.92 Hz, Ar), 9.04 (d, 2H, J=4.16 Hz, b-pyrrole), 9.65 (s, 2H, b-

19-(5-tBuCarbazolethiophen-2-yl)-5,10-di(p-methoxycarbonyl-

phenyl)-25-oxasmaragdyrin (24): 5(5-tBuCarbazolethiophen-2-yl)-

dipyrromethane and 5,10-di(p-methoxycarbonylphenyl)-16-oxatri-

pyrrane were condensed by following the general procedure D

furan), 10.15 (d, 2H, J=4.40 Hz, b-pyrrole), 10.54 (m, 2H, b-pyrrole),

1

[

2

1

0.65 ppm (d, 2H, J=4.44 Hz, b-pyrrole); B NMR (128.4 MHz,

13

D ]THF): d=ꢀ13.11 ppm (brs); C NMR (100 MHz, [D ]THF): d=

8

1.73, 92.43, 96.75, 99.07, 108.57, 122.38, 123.00, 123.19, 123.68,

25.90, 129.22, 130.11, 130.96, 131.70, 131.89, 132.64, 135.02,

(338 mg, 34% yield). R =0.32 (dichloromethane/hexanes 3:7);

f

1

H NMR (400 MHz, CDCl ): d=1.55 (s, 18H, tBu), 4.12 (s, 6H, ꢀOMe),

3

1

9

35.27, 139.05, 140.56, 151.10, 167.24 ppm; F NMR (376.5 MHz,

7.68 (d, 2H, J=8.40 Hz, Ar), 7.71 (d, 1H, J=3.68 Hz, b-thiophene),

7.90 (d, 2H, J=8.64 Hz, Ar), 8.13 (d, 1H, J=4.12 Hz, b-thiophene),

8.23 (s, 2H, Ar), 8.31 (d, 4H, J=7.84 Hz, Ar), 8.43 (d, 2H, J=4.24 Hz,

b-pyrrole), 8.49 (d, 4H, J=7.84 Hz, Ar), 8.75 (s, 2H, b-furan), 9.43 (d,

2H, J=4.32 Hz, b-pyrrole), 9.47 (d, 2H, J=4.28 Hz, b-pyrrole),

9.52 ppm (d, 2H, J=4.24, b-pyrrole); HRMS- ESI: m/z: calcd for

[

4

D ]THF): d=ꢀ149.03 ppm (brs); UV/Vis (THF): l (e)=461 (186),

8

max

3

ꢀ1

97 (51), 737 nm (44·10 m cm ); HRMS-FAB+: m/z: calcd for

+

C H BF N O : 736.2457; found: 736.2466 [M] ; elemental analysis

4

6

31

2

4

3

calcd (%) for C H BF N O ·1.4C H 0.9CH Cl : C 71.25, H 5.51, N

4

6

31

2

4

3

6

13

2

6

.01; found: C 71.06, H 5.79, N 6.03.

ꢀ

C H N O S: 990.3689; found: 990.3698 [MꢀH] .

63

52

5

-(5-tBuCarbazolethiophen-2-yl)dipyrromethane (19): Dipyrro-

methnae 19 was prepared from 5-tBucarbazolethiophene-2-carbal-

19-(p-Hexyloxyphenyl)-5,10-di(p-methoxycarbonylphenyl)-25-

dehyde by following general procedure A (1.1 g, 85% yield). R =

oxasmaragdyrin (25): 5-(p-hexyloxyphenyl)dipyrromethane and

f

1

0

1

6

.31 (dichloromethane/hexanes 4:6); H NMR (400 MHz, CDCl ) d=

.48 (s, 18H, tBu), 5.76 (s, 1H, meso-CH), 6.13 (m, 2H, b-pyrrole),

.22 (m, 2H, b-pyrrole), 6.75 (m, 2H, a-pyrrole), 6.90 (d, 1H, b-thio-

5,10-di(p-methoxycarbonylphenyl)-16-oxatripyrrane

were

con-

3

densed by following the general procedure D (322 mg, 20% yield).

1

R =0.36 (dichloromethane/hexanes 3:7); H NMR (500 MHz, CDCl )

f

3

&

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

14

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ÝÝ These are not the final page numbers!

Full Paper

d=1.01 (t, 3H, ꢀCH ), 1.48 (m, 4H, ꢀCH ), 1.65 (m, 2H, ꢀCH ), 2.01

130.15, 131.36, 132.09, 134.41, 134.67, 135.84, 138.25, 147.24,

3

2

19

(

m, 2H, ꢀCH ), 4.11 (s, 6H, ꢀOMe), 4.28 (t, 2H, ꢀOCH ), 7.38 (d, 2H,

148.98, 167.34 ppm; F NMR (470.5 MHz, CDCl ): d=ꢀ149.23 ppm

2

3

J=7.38 Hz, Ar), 8.27 (m, 8H, Ar, b-pyrrole), 8.46 (s, 4H, Ar), 8.62 (s,

(brs); HRMS-FAB+: m/z: calcd for C H BF N O : 770.2572; found:

46

33

2

4

5

+

2

9

H, b-furan), 8.92 (s, 2H, b-pyrrole), 9.28 (s, 2H, b-pyrrole),

770.2529 [M] .

.37 ppm (s, 2H, b-pyrrole); HRMS-MALDI: m/z: calcd for

+

B(OC H ) -[19-(p-Tolyl)-5,10-di(p-methoxycarbonylphenyl)-25-ox-

2

5 2

C H N O : 808.3260; found: 808.3278 [M] .

5

1

44

4

6

asmaragdyrin] (30): BF -oxasmaragdyrin 29 (100 mg, 0.13 mmol)

2

1

9-(p-Tolyl)-5,10-di(p-methoxycarbonylphenyl)-25-oxasmaragd-

was dissolved in dry CH Cl (50 mL) in the presence of aluminum

2

yrin (26): 5-(p-Tolyl)dipyrromethane and 5,10-di(p-methoxycarbo-

nylphenyl)-16-oxatripyrrane were condensed following the general

chloride (104 mg, 0.78 mmol) under nitrogen. The resulting mixture

was refluxed for 10 min and then ethanol (10 mL) was added. The

reaction mixture was stirred for additional 10 min. The reaction

mixture was concentrated and purified by column chromatography

procedure D (434 mg, 30% yield). R =0.34 (dichloromethane/hex-

f

1

anes 3:7); H NMR (400 MHz, CDCl ): d=2.73 (s, 3H, <C->CH ),

3

4

.09 (s, 6H; ꢀOMe), 7.66 (d, 2H, J=7.52 Hz, tolyl), 8.27 (m, 8H, Ar,

on silica gel using hexanes/dichloromethane (1:1, R =0.62) to give

f

tolyl, b-pyrrole), 8.44 (d, 4H, J=7.72 Hz, Ar), 8.64 (s, 2H, b-furan),

1

the desired product as a green solid (100 mg, 93% yield). H NMR

8

9

.92 (d, 2H, J=4.00 Hz, b-pyrrole), 9.28 (d, 2H, J=4.04, b-pyrrole),

(

400 MHz, CDCl ): d=ꢀ3.77 (t, 6H, J=6.96 Hz; ꢀCH ), ꢀ3.39 (q, 4H,

ꢀ

3

.36 ppm (d, 2H, J=3.80 Hz, b-pyrrole); HRMS- ESI : m/z: calcd for

J=7.00 Hz, ꢀOCH ), ꢀ0.65 (s, 2H, ꢀNH), 2.77 (s, 3H, ꢀCH ), 4.16 (s,

ꢀ

2

3

C H N O : 721.2451; found: 721.2452 [MꢀH] .

BF -[19-(5-tBuCarbazolethiophen-2-yl)-5,10-di(p-methoxycarbon-

4

6

33

4

5

6

H, ꢀOMe), 7.76 (d, 4H, J=7.84 Hz; Ar), 8.49 (m, 6H, Ph), 8.55 (d,

2

2H, J=8.20 Hz; Ar), 8.61 (m, 2H, b-pyrrole), 9.42 (s, 2H, b-furan),

yl phenyl)-25-oxasmaragdyrin] (27): Boryl oxasmaragdyrin 27 was

prepared from oxasmaragdyrin 24 by following general proce-

9

1

.42 (d, 2H, J=4.36 Hz; b-pyrrole), 9.87 (m, 2H, b-pyrrole),

11

0.05 ppm (d, 2H, J=4.40 Hz; b-pyrrole); B NMR (128.4 MHz,

13

dure E (170 mg, 48% yield). R =0.34 (dichloromethane/hexanes

f

CDCl ): d=ꢀ12.00 ppm (brs); C NMR (100 MHz, CDCl ): d=11.64,

3

1

3

:2); H NMR (400 MHz, CDCl ): d=ꢀ3.77 (t, 2H, ꢀNH), 1.58 (s, 18H,

3

21.54, 49.02, 52.42, 105.70, 118.50, 118.57, 121.05, 124.24, 124.50,

tBu), 4.18 (s, 6H, ꢀOMe), 7.71 (d, 2H, J=8.68 Hz, Ar), 7.79 (d, 1H,

J=3.44 Hz, b-thiophene), 7.96 (d, 2H, J=8.64 Hz, Ar), 8.29 (d, 3H,

J=4.20 Hz, Ar, b-thiophene), 8.50 (d, 4H, J=7.46 Hz, Ar), 8.60 (d,

1

28.65, 129.02, 129.67, 132.68, 133.06, 134.54, 134.67, 136.39,

37.81, 148.01, 148.79, 167.47 ppm; HRMS-ESI: m/z: calcd for

+

C H BN O : 822.3225; found: 822.3231 [M+H] .

50

43

4

7

4

H, J=7.52 Hz, Ar), 8.95 (d, 2H, J=4.24 Hz, b-pyrrole), 9.43 (s, 2H,

b-furan), 9.99 (d, 2H, J=4.08 Hz, b-pyrrole), 10.23 (d, 2H, J=

.04 Hz, b-pyrrole), 10.34 ppm (d, 2H, J=4.04 Hz, b-pyrrole);

BF -[19-(5-tBuCarbazolethiophen-2-yl)-5,10-di(4-carboxylphenyl)-

2

5-oxasmaragdyrin] (SM5): Dye SM5 was prepared by hydrolysis

4

1

13

of BF -oxasmaragdyrin 27 by following general procedure F

B NMR (160.4 MHz, CDCl₃): d=ꢀ12.58 ppm (brs);

C NMR

2

(

141 mg, 98% yield). R =0.1 (dichloromethane/MeOH 9.5:0.5);

(

125 MHz, CDCl ): d=32.08, 34.90, 52.49, 106.33, 110.03, 111.35,

f

3

1

H NMR (400 MHz, [D ]THF): d=ꢀ3.79 (t, 2H, ꢀNH), 1.55 (s, 18H,

116.47, 120.74, 120.81, 122.41, 123.97, 124.22, 124.76, 128.88,

8

tBu), 7.71 (d, 2H, J=8.64 Hz, Ar), 7.95 (d, 1H, J=3.72 Hz, b-thio-

phene), 7.97 (d, 2H, J=8.64 Hz, Ar), 8.33 (d, 2H, J=1.48 Hz, Ar),

1

29.83, 130.24, 130.78, 131.12, 132.05, 134.45, 137.19, 140.29,

43.76, 144.08, 147.09, 149.10, 167.29 ppm; F NMR (470.5 MHz,

19

8

9

2

.49 (d, 1H, J=3.72 Hz, b-thiophene), 8.55 (d, 4H, J=8.12 Hz, Ar),

.61 (d, 4H, J=8.08 Hz, Ar), 9.01 (dd, 2H, J=2.12 Hz, b-pyrrole),

.57 (s, 2H, b-furan), 10.11 (d, 2H, J=4.52 Hz, b-pyrrole), 10.49 (dd,

H, J=1.91 Hz, b-pyrrole), 10.60 ppm (d, 2H, J=4.48 Hz; b-pyr-

CDCl₃): d=ꢀ149.04 ppm (brs); HRMS-FAB+: m/z: calcd for

+

C H BF N O S: 1039.3750; found: 1039.3752 [M] .

6

3

52

2

5

BF -[19-(p-Hexyloxyphenyl)-5,10-di(p-methoxycarbonyl phenyl)-

2

5-oxasmaragdyrin] (28): Boryl oxasmaragdyrin 28 was prepared

from oxasmaragdyrin (25) by following general procedure E

150 mg, 55% yield). R_f=0.4 (dichloromethane/hexanes 3:2);

11

13

role); B NMR (160.4 MHz, [D ]THF): d=ꢀ12.86 (brs); C NMR

8

(125 MHz, [D ]THF): d=32.47, 35.59, 107.46, 110.92, 111.81, 117.38,

8

(

1

121.74, 122.14, 123.66, 125.01, 125.16, 125.35, 125.51, 125.79,

H NMR (400 MHz, CDCl ): d=ꢀ3.38 (t, 2H, ꢀNH), 1.02 (t, 3H, ꢀ

3

1

25.97, 126.22, 129.97, 130.91, 131.87, 132.18, 132.55, 133.01,

35.33, 138.36, 141.44, 144.82, 147.74, 150.30, 167.94 ppm; F NMR

CH ), 1.50 (m, 4H, ꢀCH ), 1.68 (m, 2H, ꢀCH ), 2.04 (m, 2H, ꢀCH ),

3

2

19

4

8

1

.16 (s, 6H, ꢀOMe), 4.31 (t, 2H, ꢀOCH ), 7.49 (d, 2H, J=8.56 Hz, Ar),

2

(

470.5 MHz, [D ]THF): d=ꢀ149.34 ppm (brs); UV/Vis (THF): l

8

max

.48 (m, 6H, Ar), 8.57 (d, 4H, J=8.08 Hz, Ar), 8.84 (dd, 2H, J=

.96 Hz, b-pyrrole), 9.32 (s, 2H, b-furan), 9.55 (d, 2H, J=4.48 Hz, b-

3

ꢀ1

e)=452 (165), 478 (100), 712 nm (38·10 m cm ); HRMS-FAB+:

+

m/z: calcd for C H BF N O S: 1011.3437; found: 1011.3455 [M] ;

elemental analysis calcd (%) for C61

C 68.92, H 5.02, N 6.19; found: C 68.62, H 5.09, N 6.22.

61

48

2

5

pyrrole), 10.13 (dd, 2H, J=2.01 Hz, b-pyrrole), 10.21 ppm (d, 2H,

1

H48BF N O S·0.5C H13 0.9CH Cl :

2 5 5 6 2 2

J=4.40 Hz, b-pyrrole); B NMR (160.4 MHz, CDCl ): d=ꢀ12.16 ppm

3

1

3

(

brs); C NMR (125 MHz, CDCl ): d=14.12, 22.72, 25.93, 29.47,

3

1

1.73, 52.47, 68.48, 105.97, 114.70, 119.92, 120.10, 120.85, 121.74,

23.81, 124.60, 125.20, 128.86, 129.59, 130.12, 130.83, 131.41,

32.16, 134.38, 135.77, 147.22, 148.99, 159.80, 167.33 ppm; F NMR

BF -[19-(p-Hexyloxyphenyl)-5,10-di(4-carboxylphenyl)-25-oxa-

smaragdyrin] (SM6): Dye SM6 was prepared by hydrolysis of BF₂-

2

19

oxasmaragdyrin 28 by following general procedure F (95 mg, 92%

(

470.5 MHz, CDCl ): d=ꢀ149.19 ppm (brs); HRMS-MALDI: m/z:

1

3

yield). R_f=0.14 (dichloromethane/MeOH 9.5:0.5);

H NMR

+

calcd for C H BF N O : 857.3322; found: 857.3356 [M+H] .

5

1

44

2

4

6

(400 MHz, [D ]THF): d=ꢀ3.38 (t, 2H, ꢀNH), 1.03 (t, 3H, ꢀCH ), 1.52

8

3

BF -[19-(p-Tolyl)-5,10-di(p-methoxycarbonylphenyl)-25-oxasma-

ragdyrin] (29): Boryl oxasmaragdyrin 29 was prepared from oxa-

smaragdyrin 26 by following general procedure E (120 mg, 30%

yield). R =0.59 (dichloromethane/hexanes 3:2); H NMR (400 MHz,

(m, 6H, ꢀCH ), 2.03 (m, 2H, ꢀCH ), 4.35 (t, 2H, ꢀOCH ), 7.56 (d, 2H,

2

J=8.48 Hz, Ar), 8.55 (m, 10H, Ar), 8.89 (dd, 2H, J=2.12 Hz, b-pyr-

role), 9.44 (s, 2H, b-furan), 9.60 (d, 2H, J=4.40 Hz, b-pyrrole), 10.34

(dd, 2H, J=2.16, b-pyrrole), 10.42 ppm (d, 2H, J=4.40 Hz, b-pyr-

1

f

1

13

CDCl ): d=ꢀ3.48 (t, 2H, ꢀNH), 2.78 (s, 3H, ꢀCH ), 4.17 (s, 6H, ꢀ

role); B NMR (160.4 MHz, [D ]THF): d=ꢀ14.00 ppm (brs); C NMR

3

8

OMe), 7.79 (d, 2H, J=7.72 Hz, tolyl), 8.49 (d, 6H, J=8.08 Hz, Ar,

tolyl), 8.58 (d, 4H, J=8.12 Hz, Ar), 8.86 (dd, 2H, J=2.96 Hz, b-pyr-

role), 9.34 (s, 2H, b-furan), 9.58 (d, 2H, J=4.40 Hz, b-pyrrole), 10.16

(125 MHz, [D ]THF): d=14.56, 23.74, 27.00, 30.81, 32.81, 69.13,

8

107.05, 115.62, 120.87, 121.32, 121.59, 122.89, 124.90, 125.56,

125.88, 125.98, 129.96, 130.62, 131.82, 132.02, 132.50, 133.09,

1

9

(

dd, 2H, J=1.95 Hz, b-pyrrole), 10.24 ppm (d, 2H, J=4.40 Hz, b-

135.24, 136.76, 147.89, 150.15, 161.12, 167.91 ppm; F NMR

1

pyrrole);

B NMR (160.4 MHz, CDCl₃): d=ꢀ12.39 ppm (brs);

(470.5 MHz, [D ]THF): d=ꢀ151.36 ppm (brs); UV/Vis (THF): l

8

max

1

3

ꢀ1

C NMR (125 MHz, CDCl ): d=21.57, 52.48, 105.99, 120.05, 120.22,

(e)=446 (254), 473 (118), 699 nm (33·10 m cm ); HRMS-FAB+:

m/z: calcd for C H BF N O : 828.2931; found: 828.2927 [M] ; ele-

3

+

1

20.77, 121.85, 123.83, 124.61, 125.20, 128.87, 129.27, 129.61,

49

39

2

4

6

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

15

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

&

These are not the final page numbers! ÞÞ

Full Paper

mental analysis calcd (%) for C H BF N O : C 71.02, H 4.74, N 6.76;

found: C 71.05, H 4.75, N 6.72.

91195 A, Newport Corp.). Photocurrent-voltage characteristics of

the DSSCs were recorded on a potentiostat/galvanostat (CHI650B,

49

39

2

4

6

ꢀ

2

CH Instruments) at a light intensity of 100 mWcm and calibrated

to an Oriel reference solar cell (Oriel 91150, Newport Corp.). The

monochromatic quantum efficiency was recorded on a monochro-

mator (Oriel 74100, Newport Corp.) under short-circuit conditions.

The intensity of each wavelength was within the range 1–

BF -[19-(p-Tolyl)-5,10-di(4-carboxylphenyl)-25-oxasmaragdyrin]

2

(

SM7): Dye SM7 was prepared by hydrolysis of BF -oxasmaragdyrin

2

9 by following general procedure F (95 mg, 98% yield). R =0.12

f

1

(

dichloromethane/MeOH 9.5:0.5); H NMR (400 MHz, [D ]THF): d=

8

ꢀ

3.52 (t, 2H, ꢀNH), 2.77 (s, 3H, ꢀCH ), 7.82 (d, 2H, J=7.76 Hz,

3

ꢀ2

3

mWcm . Electrochemical impedance spectra (EIS) were recorded

tolyl), 8.53 (d, 6H, J=8.07 Hz, Ar, tolyl), 8.59 (d, 4H, J=8.12 Hz, Ar),

for DSSC under illumination at open-circuit voltage (V ) or in the

8

2

1

.92 (dd, 2H, J=2.16 Hz, b-pyrrole), 9.48 (s, 2H, b-furan), 9.61 (d,

OC

dark at ꢀ0.55 V at RT. The frequencies explored ranged from 0.1 Hz

H, J=4.40 Hz, b-pyrrole), 10.37 (dd, 2H, J=1.97 Hz, b-pyrrole),

11

to 1 MHz.

0.44 ppm (d, 2H, J=4.52 Hz; b-pyrrole); B NMR (160.4 MHz,

13

[

D ]THF): d=ꢀ14.20 ppm (brs); C NMR (125 MHz, [D ]THF): d=

8

2

1

1.64, 107.09, 121.02, 121.32, 121.47, 123.03, 124.94, 125.58,

25.80, 129.95, 130.16, 130.65, 132.04, 132.42, 132.99, 135.27,

Acknowledgements

19

35.67, 137.03, 139.11, 147.89, 150.14, 167.91 ppm; F NMR

(

470.5 MHz, [D ]THF): d=ꢀ151.36 ppm (brs); UV/Vis (THF): l

The authors greatly acknowledge financial support from the

Ministry of Science and Technology (Taiwan) and Academia

Sinica. Mass spectroscopy analyses were performed by Mass

Spectrometry facility of the Institute of Chemistry, Academia

Sinica, Taiwan. The help from Dr. J.-T’suen Lin on the photovol-

taic measurements and instrumentations are greatly

appreciated.

8

max

3

ꢀ1

e)=445 ( 271), 472 (124), 698 nm (32·10 m cm ); HRMS-FAB+:

+

m/z: calcd for C H BF N O : 742.2199; found 742.2197 [M] ; ele-

mental analysis calcd (%) for C H BF N O ·0.6C H 0.2CH Cl : C

7

4

29

2

4

5

44

29

2

4

5

6

13

2

0.75, H 4.70, N 6.91; found: C 70.82, H 4.62, N 6.91.

B(OC H ) -[19-(p-Tolyl)-5,10-di(4-carboxylphenyl)-25-oxasmar-

agdyrin] (SM8): Dye SM8 was prepared by hydrolysis of B(OEt)₂-

oxasmaragdyrin 30 by following general procedure F (83 mg, 87%

yield). R_f=0.14 (dichloromethane/MeOH 9.5:0.5);

2

5 2

1

H NMR

(

400 MHz, CDCl ): d=ꢀ3.85 (t, 6H, J=6.68 Hz; ꢀCH ), ꢀ3.50 (q, 4H,

3

Keywords: dyes and pigments · dye-sensitized solar cells ·

macrocycles · porphyrinoids · sensitizers

J=6.85 Hz, ꢀOCH ), ꢀ0.89 (s, 2H, ꢀNH), 2.75 (s, 3H, ꢀCH ), 7.79 (d,

2

3

4

8

H, J=7.44 Hz; Ar), 8.49 (m, 6H, Ph), 8.56 (d, 2H, J=7.20 Hz, Ar),

.61 (d, 2H, J=4.16 Hz, b-pyrrole), 9.33 (s, 2H, b-furan), 9.44 (d, 2H,

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11

0.23 ppm (d, 2H, J=4.36 Hz, b-pyrrole); B NMR (128.4 MHz,

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13

CDCl ): d=ꢀ13.97 ppm (brs); C NMR (100 MHz, CDCl ): d=12.03,

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ꢀ4

1

0

m oxasmaragdyrin and 3ꢂ10 m CDCA in THF at 308C and

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3

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ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ÝÝ These are not the final page numbers!

Full Paper

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Received: October 28, 2014

Published online on && &&, 0000

2

014 , 50 , 725–727.

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

17

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

&

These are not the final page numbers! ÞÞ

Full Paper

FULL PAPER

Expanded porphyrins in DSSCs: Molec-

ular engineering of the boryl oxasmar-

agdyrins to tune the overall photon-to-

current conversion efficiency in dye-sen-

sitized solar cells (DSSCs) is demonstrat-

ed. The superior performance of boryl

oxasmaragdyrin with one anchoring

group over two anchoring groups is ex-

plained with the aid of DFT calculations,

photophysical, and photovoltaic proper-

ties (see scheme).

&

Dye-Sensitized Solar Cells

S. B. Mane, C.-H. Hung*

& – &&

&

Molecular Engineering of Boryl

Oxasmaragdyrins through Peripheral

Modification: Structure–Efficiency

Relationship

&

Chem. Eur. J. 2015, 21, 1 – 18

www.chemeurj.org

18

ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ÝÝ These are not the final page numbers!

Article Doi

Molecular engineering of boryl oxasmaragdyrins through peripheral modification: Structure-efficiency relationship

DOI: 10.1002/chem.201405856

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Article abstract of DOI:10.1002/chem.201405856

Full text of DOI:10.1002/chem.201405856

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