Synthesis and Photophysical, Electrochemical and Theoretical Study of Thiazole-Annelated Phthalocyanines

FULL PAPER

DOI: 10.1002/ejoc.201500785

Synthesis and Photophysical, Electrochemical and Theoretical Study of

Thiazole-Annelated Phthalocyanines

[a]

[b]

[c]

ˇ

Mária Necedová, Peter Magdolen, Veronika Novakova, Marek Cigán,

[d]

[a]

ˇ

Silvia Vlcková, Pavol Zahradník, and Andrea Fülöpová*

Keywords: Phthalocyanines / Benzothiazole / Electrochemistry / Aggregation / Density functional calculations

Phthalocyanines with annelated thiazole rings were synthe-

sised by cyclotetramerisation of benzothiazoledicarbonitriles.

Three types of these dicarbonitriles with ortho-configuration

were prepared from disubstituted anilines and their cycli-

sation led to all possible patterns of annelation in the phthalo-

cyanine skeleton. Further substitution at the periphery of

Q-bands were shifted to higher wavelengths (712–729 nm)

because of the higher delocalisation, and fluorescence quan-

tum yields increased compared with isoelectronic naphthalo-

cyanines. Aggregation properties of the studied phthalo-

cyanines were dependent on the type of isomer. The effects

of the annelation pattern on the redox potentials were also

the macrocycle by methyl or tert-butyl substituents was real- investigated. Experimental data are compared with theoreti-

ised to improve the solubility or to allow further derivatis-

ation of target molecules. The characteristic UV/Vis spectral

cal values obtained by DFT calculations.

the molecular properties is by extending the π-electron sys-

tem by peripheral linear or angular annelation with an aro-

matic or heteroaromatic ring. Especially heteroannelation

can change the electronic properties of phthalocyanines

considerably. This results from the synergy of properties

coming from both the heterocyclic ring and the phthalo-

cyanine skeleton.

There is a large range of heterocyclic analogues of

phthalocyanines annelated mainly with six-membered, ni-

trogen-containing heterocycles. Of the phthalocyanines

with five-membered heterocyclic rings only analogues with

imidazole rings have been studied in detail.^[4]Phthalocyan-

ines with annelated heterocycles are commonly prepared

through the use of appropriately substituted precursors,

namely iminoisoindoles, phthalimides, and phthalonitrile

derivatives. Although there are many synthetic protocols

available for the preparation of substituted Pcs,^[5–7]cyclo-

tetramerisation of substituted phthalonitriles under basic

conditions is generally preferred.

Introduction

The electronic structure of phthalocyanines (Pcs) is char-

acterised by the highly delocalised planar 18-π-electron sys-

tem. Such compounds exhibit advantages like exceptional

stability, versatility and processability and they are investi-

gated intensively as materials of extraordinary technological

importance (use in semiconductor devices, solar cells,

photosensitisers, nonlinear optics, etc.).^[1–3]These and other

emerging uses are conditioned by the absorption and emis-

sion wavelength, quantum yields of photophysical processes

and necessary stability of the compounds. The structural

flexibility of Pcs is demonstrated by the large number of

metallic complexes as well as by the huge variety of substit-

uents that can be attached to the periphery of the Pc core.

All these chemical variations alter the electronic structure

of the macrocyclic core, and allow the physicochemical

properties of the system to be tuned. Another way to adjust

[a] Department of Organic Chemistry, Faculty of Natural Sciences,

Comenius University,

In the presented work, we report a series of Pcs aug-

mented with thiazole units. Taking into account the number

of π-electrons involved in the formation of the aromatic

macrocyclic π-system, these derivatives can be considered

Mlynská dolina, Ilkovicˇova 6, 84215 Bratislava, Slovak

Republic

E-mail: fulopovaa@fns.uniba.sk

http://staryweb.fns.uniba.sk/index.php?id=zahradnik

[b] Department of Biophysics and Physical Chemistry, Faculty of to be heterocyclic analogues of naphthalocyanines (Ncs).

Pharmacy in Hradec Kralove, Charles University in Prague,

The fusion of heteroaromatic rings with phthalocyanines

Heyrovskeho 1203, 50005 Hradec Kralove, Czech Republic

produces a significant bathochromic shift in absorption

maximum and higher fluorescence (compared to Ncs) and

hence influences their physical and optical properties.^[8]

Heterocyclic annelation to the phthalocyanine skeleton also

results in an improvement in the thermic, chemical, and

photochemical stability of the macrocycle.^[9]Another aspect

is the modification of the Pc unit caused by the electron-

[c] Institute of Chemistry, Faculty of Natural Sciences, Comenius

University,

Mlynská dolina, Ilkovicˇova 6, 84215 Bratislava, Slovak

Republic

[d] Institute of Chemistry, Slovak Academy of Sciences,

Dubravska cesta 9, 84538 Bratislava, Slovak Republic

Supporting Information and ORCID(s) from the author(s) for

this article are available on the WWW under http://dx.doi.org/

10.1002/ejoc.201500785.

Eur. J. Org. Chem. 2015, 7053–7068

7053

A. Fülöpová et al.

FULL PAPER

Figure 1. Possibilities of structural modification of benzothiazole dicarbonitriles in relation to the target annelated Pcs.

donating and/or electron-withdrawing effects of the hetero- lower symmetry. Herein, we report the synthesis of three

cycle.

dicyanobenzothiazole isomers substituted at the 2-position

Benzothiazole derivatives are important heterocyclic of the thiazole ring by a methyl group (compounds 1a–3a)

compounds because of their chemical and biological signifi- or by a tert-butyl group (compounds 1b–3b) as precursors

cance.^[10]We also chose to focus on this type of heterocycle of the thiazole-annelated Pcs. The peripherally substituted

because of their high synthetic potential for peripheral deri- phthalocyanines 4–6 can be obtained as a mixture of four

vatisation, which can affect the stability, solubility and elec- isomers with different types of symmetry (C_4h, C_2v, C_sand

tron structure of the molecule. The diverse range of poten- D_2h). Structures of the studied Pc regio- and symmetry-iso-

tial refinements in benzothiazoledicarbonitriles as the start- mers with the starting dicyanobenzothiazoles are presented

ing material for Pc synthesis is presented in Figure 1.

in Figure 2 (only the C_4hsymmetry), all other types of sym-

Until now, Pcs containing an annelated thiazole ring metry are included in Figure S1 (see the Supporting Infor-

have not been prepared; to our knowledge, only Pcs with a mation).

benzothiazole moiety as a peripheral substituent have been

reported.^[11]Herein, we discuss the main features associated

with the photophysics and electrochemistry of a set of new

benzothiazole derivatives and present the results of a DFT

Synthesis of Benzothiazoledicarbonitriles

study. The influence of annelated rings on these properties

Heterocyclic dinitriles with the appropriate pattern of

is also discussed.

substitution as the key precursors for annelated Pcs were

prepared by two different routes from either 2-alkyl-5-nitro-

benzothiazole or 4-aminophthalonitrile. First strategy was

employed for the synthesis of 2-methylbenzothiazole-4,5-di-

Results and Discussion

Whereas the unsubstituted Pc represents a highly sym- carbonitrile (1a) and the 2-tert-butyl derivative (1b). The

metrical compound, unsymmetrical substitution on the pe- starting 2-methyl-5-nitrobenzothiazole (9a) was prepared

riphery of the macrocycle gives rise to derivatives with through a previously reported two-step procedure from

Figure 2. The structure of starting benzothiazoledicarbonitriles 1–3 and studied phthalocyanines 4–6 with C_4hsymmetry.

7054

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

2-bromo-5-nitroaniline (7).^[12]A similar procedure was also described above to give dinitriles 2a and 2b. In a similar

applied to the synthesis of 2-tert-butyl derivative (9b). way, the second isomer 17 was converted either into 2-meth-

Herein, the acylation of 2-bromo-5-nitroaniline with pivalic ylbenzothiazole-6,7-dicarbonitrile (3a) or into 2-tert-butyl

anhydride forewent the next simultaneous thionation and analogue 3b. All the reaction steps used in this route were

cyclisation, which led to the required nitrobenzothiazole. obtained in moderate or good yields (Scheme 2).

The common route for target dinitriles 1a and 1b then in-

Dinitriles show a typical band for the nitrile groups in

volved the reduction of nitrobenzothiazoles to amines by the IR spectra at 2232–2228 cm^–1. Furthermore, a typical

using iron dust and applying ultrasound irradiation. Benzo- pattern for a tetrasubstituted benzene ring can be observed

thiazole amines 10a and 10b were acetylated with Ac₂O, in the region 900–700 cm^–1.^[13]The electron-withdrawing

brominated and deacetylated to afford 4-bromo-5-amino- character of the CN groups shifts these bands to higher

benzothiazoles 13a and 13b. The acetylation was necessary wavenumbers (819 and 824 cm^–1, 896 and 902 cm^–1, 848

to achieve the required regioselectivity of bromination. and 849 cm^–1for 1a–b, 2a–b and 3a–b, respectively). The

Amines were further diazotized with tert-butyl nitrite in the calculated vibrational frequencies for all starting dinitriles

presence of CuBr, providing dibromobenzothiazoles 14a (Figure S2) show good agreement with the obtained experi-

and 14b in a moderate yield. Finally, dinitriles 1a and 1b mental spectra. These computed C–H wagging vibrations

were obtained by the Rosenmund–von Braun reaction with are at 844, 917 and 939 (each hydrogen has its own vi-

CuCN under microwave conditions (Scheme 1).

bration) and 867 cm^–1for 1a–3a and 843, 918, 936 and

The second route starting from 4-aminophthalonitrile 15 866 cm^–1for 1b–3b, respectively. Other characteristic bands

was used to prepare dinitriles 2 and 3. Phthalonitrile 15 for methyl and tert-butyl groups are calculated to absorb at

was first brominated with N-bromosuccinimide (NBS) to 1467–1462 cm^–1and at 1497–1467 cm^–1, whereas the experi-

produce a mixture of monobromo derivatives 16 and 17. mental values are 1374 and 1365 cm^–1, respectively. Vi-

The mixture was chromatographically separated and isomer brations for CϵN groups are calculated to absorb at 2371–

16 was further acylated and cyclised by using the procedure 2364 cm^–1.

Scheme 1. Synthesis of the benzothiazole-4,5-dicarbonitriles 1a and 1b.

Scheme 2. Synthesis of the benzothiazoledicarbonitriles 2a–b and 3a–b.

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7055

A. Fülöpová et al.

FULL PAPER

Synthesis of Phthalocyanines

stantially lower yield. The reason for the low yield of tetra-

merisations in tert-butyl and the failure in methyl benzo-

thiazoles with cyano groups in the 4,5-positions of benzo-

thiazole can be explained by unsuitable conformations of

intermediates, which were calculated by DFT methods and

are discussed below.

Similarly to Pcs and related macrocycles, the synthesis of

4, 5 and 6 was performed by cyclotetramerisation of the

corresponding ortho-dicarbonitriles 1, 2 and 3 in the pres-

ence of nHexOLi, according to published procedures

(Scheme 3).^[14]

Based on DFT calculations (computational details can

be found in the Experimental Section) we determined the

total energy differences between the twelve isomers with

methyl groups (Table 1). The C_4hisomer turned out to be

the most energetically favourable in all three studied re-

gioisomers. The 4a isomers have far higher relative energies

than the two other regioisomer groups, because, except for

the C_4hisomer, their structures are not planar. There is a

steric conflict between the peripheral heterocyclic fragments

in which the thiazole nitrogen atoms are situated close to

each other. Given that the synthesis of derivative 4a was

unsuccessful and that derivative 4b had the lowest yield in

the tert-butyl series, we investigated the cyclotetrameri-

sation process in more detail through the use of quantum

chemical calculations. Two reaction pathways for the

mechanism of cyclotetramerisation have been described.^[15]

After nucleophilic attack of the nHexO^–anion on one of

the nitrile carbon atoms, an alkoxyiminoisoindolenine in-

termediate is formed that reacts with a second benzothi-

azoledicarbonitrile to give a dimeric intermediate. Subse-

quent formation of a trimeric intermediate, which reacts

further with the fourth dicarbonitrile or undergoes a self-

condensation process of the two dimers, yields the tetra-

meric intermediate. Ring-closure follows, in which the imide

group attacks the carbon with the alkoxy group. According

to the optimal geometry DFT calculations for the dimeric

intermediates, in the case of derivative 1a there is a dihedral

angle of 112.4° between the subunits, whereas correspond-

ing angle for 2a and 3a is 60.6° and 63.8°, respectively (Fig-

ure S4). The cyclotetramerisation process in the case of

metal-free Pcs follows the sequential formation of the tetra-

mer, but seemingly is not carried out until the end because

the geometry of the trimer and tetramer is clearly even more

twisted than that of the dimer, and ring-closure is not pos-

sible. In addition to the steric restrictions of phthalonitrile

dimers, electronic effects also play an important part in the

formation of Pcs and substituents may activate or deacti-

vate dicarbonitriles towards a nucleophilic attack.

Scheme 3. Synthesis of annelated phthalocyanines 4–6.

When cyclisation reactions of 2-methylbenzothiazole de-

rivatives 1a, 2a and 3a were accomplished by this lithium

method, the products were obtained as insoluble dark-green

powders. Although the desired molecular ion at m/z 798.1

(m/z calcd. for C₄₀H₂₂N₁₂S₄798.1) was detected by

MALDI-TOF-MS for 5a and 6a, the compounds could not

be fully characterised because of their poor solubility and

strong tendency to aggregate (as can be seen from the UV/

Vis spectra presented in Figure S3). The synthesis of anne-

lated Pc from 2-methylbenzothiazole-4,5-dicarbonitrile (1a)

by using different conditions and bases failed. Pc analogues

with tert-butyl groups with improved solubility were syn-

thesised by using the same procedure with yields of 30–

50%. The metal-free annelated phthalocyanines were ob-

tained as a mixture of structural isomers. Products 4b–6b

showed the expected parent-ion peaks [M + H]⁺at m/z

967.2917, 967.2911 and 967.2901, respectively (m/z calcd.

for C₅₂H₄₆N₁₂S₄967.2924 [M + H]⁺), in high-resolution

ESI-TOF-MS. Strong intermolecular interactions also ob-

structed the purification and characterization of these com-

Infrared spectra of Pcs (Figure S5) also show the typical

pounds. The required tert-butyl derivatives were prepared in bands for tetrasubstituted benzene ring similar to those of

moderate yields with the exception of Pc synthesised from dinitriles. However, this pattern is shifted back to the char-

starting 4,5-dicarbonitrile precursor 1b, which gave sub- acteristic region (878, 821, 810, 883 and 821 cm^–1for 5a,

Table 1. Stability comparison of the possible phthalocyanine regioisomers.

Compound

Symmetry

group

E^[a]

[kJ/mol]

Compound

Symmetry

group

E^[a]

[kJ/mol]

Compound

Symmetry

group

E^[a]

[kJ/mol]

4a

C_2v

C_4h

C_s

60.6

52.5

60.6

68.3

5a

C_2v

C_4h

C_s

12.9

12.5

13.0

13.3

6a

C_2v

C_4h

C_s

1.7

0.0

1.8

3.3

D_2h

[a] Relative total energy calculated by DFT (PBE0/def2-TZVP).

7056

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

6a, 4b, 5b and 6b, respectively). Other significant bands in- all isomers. Theoretical DFT calculations were carried out

clude a strong absorbance at 2959–2864 cm^–1and at around for the most stable C_4hisomer. UV/Vis spectra together

1360 cm^–1for the tert-butyl group and weaker bands for with theoretical absorption spectra are shown in Figure 3.

methyl derivatives in the same regions. Furthermore, a Typical absorptions for the phthalocyanine system with two

number of features that are characteristic for the phthalo- strong absorption bands can be observed, corresponding to

cyanine system can be identified.^[16]Each of the phthalo- the B (Soret) band around 350 nm and Q-band between 650

cyanines exhibits N–H stretching vibrations in the range and 670 nm. All compounds exhibit a splitting of the Q-

3295–3284 cm^–1, absorptions due to N–H deformations be- band into two peaks (Q_xand Q_y), similar to other metal-

tween 1150–1029 cm^–1and between 746–741 cm^–1, and aro- free Pcs, and the splitting decreases with increased Q-band

matic C–H stretching vibrations at about 3000 cm^–1.

wavelength.^[18]This phenomenon arises from a loss of sym-

The thermal behaviour of the methyl phthalocyanines metry compared with that of metallated Pcs. The known

was investigated by simultaneous thermogravimetric and effect of the condensed ring that results in a bathochromic

differential thermal analysis (TGA-DTA). The TGA and shift of the Q-band for angular and linear benzene rings in

DTA curves of these new compounds have a similar pattern Ncs (ca. 20–30 nm in angular and 60–100 nm in linearly

to those of known unsubstituted phthalocyanine (Pc). fused Ncs)^[19]was also observed for thiazole-fused Pc, al-

Phthalocyanines 5a and 6a were stable up to 450 °C, and though the redshift is smaller than that of the correspond-

started to decompose at 467 and 515 °C, respectively ing Ncs. Similar to Ncs, linear thiazole annelation leads to

(Table 2). The initial decomposition temperatures decreased more pronounced λ_Aredshift.

in the order 6a Ͼ Pc Ͼ 5a. This result shows that the angu-

lar structure presents higher stability whereas the linear

structure is less thermally stable than the corresponding un-

substituted phthalocyanine.

Table 2. Thermal properties of Pc derivatives 5a and 6a.

Compound

Onset temp. [°C]^[a]

T_max[°C]

Pc^[b]

Pc

460

480

467

515

510

569

605

622

5a

6a

[a] Denotes the temperature at which the weight loss begins. [b] Val-

ues are from ref.^[17]

Clearly resolved NMR spectra were obtained only for

nonaggregated derivative 4b and these spectra were typical

for Pc congeners. The spectrum indicated that only three

possible regioisomers are present. This is also evident from

TLC analysis (three different spots with R_f1= 0.19, R_f2

=

0.25 and R_f3= 0.31; eluent chloroform) as well as from

calculations, which show that the isomer with D_2hsymmetry

has the highest relative energy (Table 1). The α-benzo pro-

ton signals appear as several doublets at 9.61–9.06 ppm due

to the ring current of the central core. The same reason

caused the downfield shift of the tert-butyl proton signals,

which were found at 2.05–1.70 ppm. Inner NH protons are

localised at notably high field –0.30 and –1.33, –1.41 ppm.

¹H NMR spectra for 5b indicate partial aggregation but this

is stronger for 6b, which results in broadening of the peaks

and also in position changes (see chapter 3 in the Support-

ing Information).

Optical and Photophysical Properties

Absorption and Fluorescence Spectra

Figure 3. Experimental (black) and calculated (green) absorption

spectra with TD-DFT (M06/def2-TZVP) of (a) 4b, (b) 5b and (c) 6b

in THF.

The newly prepared thiazole-annelated phthalocyanines

4b–6b exist as a mixture of four inseparable isomers (C_4h,

C_2v, C_sand D_2h) that exhibit nearly identical electronic ab-

sorption and emission spectra. Therefore, experimental ab-

The experimental spectroscopic data and the results of

sorption and emission spectra correspond to a mixture of the DFT calculations related to longwave band and frontier

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7057

A. Fülöpová et al.

FULL PAPER

Table 3. Experimental spectroscopic data measured in CH₂Cl₂and THF.

[a]

[b]

[c]

[d]

[f]

[g]

Compound

Solvent

λ_A

Q_x– Q_y

[nm]

λ_F

E_S

Δν^[e]

Φ_F

Φ_Δ

[nm]

[kJmol^–1]

[cm^–1]

4b

5b

THF

CH₂Cl₂

THF

CH₂Cl₂

THF

CH₂Cl₂

CCl₄

677, 712

683, 718

703, 729

704, 730

683, 719

650

35

26

36

35

39

14

715

724

734

736

724

726

705

790

168

166

163

167

170

152

39

135

93

112

272

824

101

81

0.15

0.35

0.34

0.22

0.04

0.43

0.19

0.12

–

0.11

–

6b^[h]

0.074

–

tBu-Pc^[20]

661, 700

771, 785

tBu-Nc-lin^[20]

[a] Maxima of main longwave absorption band. [b] Difference of the two maxima of the Q-band. [c] Maxima of the fluorescence band.

[d] Energy of the excited singlet state S₁. [e] Stokes shift. [f] Quantum yield of fluorescence using integrating sphere. [g] Singlet oxygen

quantum yield. [h] Partially aggregated.

orbital energy analysis for phthalocyanines 4b–6b are pre- fluorescence measurements for derivatives 4b–6b clearly

sented in Table 3 and Table 4. Absorption spectra were indicate the presence of two fluorescence lifetimes in both

measured in tetrahydrofuran (THF) and in CH₂Cl₂. Tetra- solvents; the first is in the range of 4.1 to 6.2 ns and the

hydrofuran as a coordinating solvent was used to suppress second unusually long lifetime is in the range of 12.1 to

the strong aggregation of macrocycles involved in the study. 16.8 ns (ca. 20% contribution to the overall fluorescence).

The experimental data obtained with tert-butyl-phthalo- This atypical fluorescence lifetime does not correlate with

cyanine (tBu-Pc) and benzofused tert-butyl linear aggregate formation and we assign it to the conformational

(2,3-)naphthalocyanine (tBu-Nc-lin)^[20]are also included for changes in the excited state. We anticipate that laser flash

comparison. As part of the DFT study we also calculated photolysis and time-resolved emission studies should ex-

the desired properties for the angular (1,2-)naphthalocyan- plain this phenomenon in more detail.

ine (Nc-ang).

Singlet oxygen generation of these phthalocyanine com-

pounds was also investigated. The quantum yields (Φ_Δ)

were determined in THF by a comparative method with

zinc phthalocyanine as a reference. Compounds 4b and 5b

showed similar values (0.11 and 0.12, respectively), whereas

the singlet oxygen quantum yield of 6b showed a low value

of less than 0.08, probably because of partial aggregation.

The Φ_Δvalues of these compounds are not affected by sub-

stitution pattern and are in the range for metal-free

phthalocyanines; generally the higher values are typical for

zinc phthalocyanines.

Table 4. TD-DFT (M06/TZVP, solvent THF) calculations of long-

wave absorption bands (λ_A), frontier orbital energies (E_HOMO

E_LUMO) and energy difference (ΔE_(H–L)) of the studied compounds.

,

Compound

λ_A

E_HOMOE_LUMOΔE_(H–L)

[nm]

[eV]

4b

5b

6b

Pc

Nc-lin

Nc-ang

658, 661

682, 698

668, 670

639, 642

732, 775

648, 656

1.87, 1.88

1.78, 1.82

1.85, 1.86

1.93, 1.94

1.60, 1.69

1.89, 1.91

–5.46

–5.31

–5.58

–5.50

–5.08

–5.64

–3.14

–3.29

–3.16

–3.11

–3.27

2.32

2.17

2.29

2.34

1.97

2.37

To enhance our understanding of the peripheral annel-

ation effect of the thiazole ring on the electronic structure

and spectral properties of Pcs, a molecular orbital study

All the studied phthalocyanine derivatives show similar within the framework of the DFT method was carried out.

fluorescence behaviour. The fluorescence band is redshifted Theoretical Q-band λ_Avalues of the studied compounds

beyond 700 nm (Table 3, Figure S6). Compared with tBu- (Figure 3) and their starting dinitriles (Figure S8) are in

Pc, the fluorescence maximum (λ_F) of all thiazole-fused good agreement with experimental data. Especially the cal-

phthalocyanines is shifted to longer wavelengths, which re- culated position of the Q-band reproduces well the ten-

sults from increased conjugation. Thus, the maximal λ_Fred- dency of the experimental results; that is, the wavelength of

shift can be seen in linear annelated derivative 5b. The the absorption maximum decreases in order 5b Ͼ 6b Ͼ 4b.

Stokes shift (Δν) of 4b and 5b is comparable with tBu-Pc, As shown in Table S1, the HOMO–LUMO transition pre-

but compound 6b shows a remarkable higher Δν value. The vails in production of the longwave Q-band. As expected,

high Δν value for 6b in CH₂Cl₂(but smaller in THF) results because both HOMO and LUMO energy decreases for lin-

from the H-aggregate formation, which can be seen in the ear thiazole-fused Pc 5b, the calculated HOMO–LUMO en-

absorption spectra (Figure S7). Compared with tBu-Pc, thi- ergy gap (ΔE_(H–L)) for 5b is lower than for both angular

azole annelation diminishes the fluorescence quantum yield thiazole derivatives 4b and 6b (similar to the ΔE_(H–L)differ-

(Φ_F). Determined Φ_Fvalues correlate quite well with the ence between linear and angular Ncs) (Table 4). For practi-

previously found Φ_Fdependence on emission wavelength cal application of phthalocyanines, not only the λ_Aredshift,

(λ_F) for metal-free Pcs in THF, although the Φ_Ffor linear but also HOMO orbital stability is desirable because this

5b is approximately three times higher than for metal-free increases their tendency to undergo oxidation.^[21]This is

or zinc Pcs with similar λ_Fvalue.^[18]Interestingly, dynamic one of the main disadvantages of Pc benzoannelation. From

7058

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

Figure 4. Calculated frontier orbitals and their energies (M06/TZVP) for the studied compounds.

this point of view, 4b and 6b showed HOMO energy com-

parable to that of Pc (Figure 4; Table 4) but the Q-band

was shifted to longer wavelengths. The energy of the

HOMO orbital of 5b was also lower than that of Nc.

As can be seen from Figure 4, the HOMOs of all com-

pounds are located on the carbon atoms of the tetraaza-

porphyrazin core and on the neighbouring benzene rings.

The LUMO and LUMO+1 energies are almost degenerate,

with the orbitals located on the nitrogen atoms and par-

tially on the opposite benzene rings. When comparing the

orbitals of Pc, Nc-lin and Nc-ang with those of thiazole-

annelated Pcs 4b–6b, a very close similarity between Pc, Nc-

ang and the angular derivatives 4b and 6b can be seen, as

well as between Nc-lin and the linear derivative 5b.

Aggregation Properties

Generally, the extent of aggregation depends on the con-

centration, temperature, nature of solvent, the substituents

and the type of the central metal ions.^[22]Larger π systems

usually have a higher tendency to aggregate.^[23]The aggre-

gation properties were studied because they may influence

the determination of photophysical parameters (singlet oxy-

gen and fluorescence quantum yields, excited-state lifetime)

and thus lead to erroneous conclusions. In this study, the

impact of the annelated thiazole rings localised on different

parts of the Pc core on the aggregation behaviour of the

studied compounds was investigated.

The changes in the visible part of absorption spectrum

of 4b–6b in THF with concentration are shown in Figure 5.

The increase in the Q-band molar absorptivity of 5b and 6b

with decreased concentration and the blueshift of this band

in THF solution clearly indicate the presence of H-aggre-

gates (mainly dimers).^[24]As expected, strong H-aggregation

of 6b in CH₂Cl₂results in a significant decrease in Φ_F(from

0.17 in THF to 0.04), whereas both monomer lifetimes re-

main unchanged.

Figure 5. Changes in the absorption spectra of (a) 4b, (b) 5b and

(c) 6b in THF upon dilution from 100 μm (dotted line) to 1.56 μm

shows a typical very intense Q-band with two well-resolved (4b), 1 μm (5b) and 0.2 μm (6b) (darkest line).

As can be seen in Figure 5, the spectrum of the monomer

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7059

A. Fülöpová et al.

FULL PAPER

vibronic bands, whereas the spectrum of the H-dimeric spe- 6b is minimal and therefore the dimerisation of 6b is most

cies exhibits a relatively weak hypsochromically shifted ab- probable.

sorption band at 600–700 nm. Surprisingly, the spectrum of

a concentrated solution of 4b is very similar to that of pure

Electrochemical Properties

The effect of thiazole annelation was also studied by

using cyclic voltammetry and square wave voltammetry.

The redox potential data were recorded for annelated

phthalocyanines only with tert-butyl groups because of the

limited solubility of analogous methyl derivatives. All vol-

tammograms contained three reduction peaks and one

oxidation peak, with similar shapes (Figure S9). The value

for second oxidation potential was observed only for 5b

(Figure S10). Notably, the potential differences between the

first and second reduction potentials for all compounds are

almost the same. The redox potentials vs. SCE are summa-

rised in Table 6 and the reported half-wave redox potentials

for tBu-Pc and tBu-Nc are given for comparison. The lim-

ited solubility of target compounds at the concentration

needed for electrochemical measurements meant that cyclic

voltammograms could not be used to clearly determine the

reversibility/irreversibility of the processes observed. Never-

theless, the recorded half-wave potentials were used for

thermodynamic calculations discussed below.

monomer and its shape remains practically unchanged at

all concentrations measured. In contrast, the aggregation of

6b is so strong that a considerable amount of H-dimers is

still present even at the lowest measurable concentration. In

this case, the Pc–Pc π–π interactions are stronger than the

Pc–solvent interactions. The aggregation thus decreases sig-

nificantly in the order: 6b Ͼ 5b Ͼ 4b. Determined dimeri-

sation constants are collected in Table 5.

Table 5. Monomer–dimer equilibrium and dimerisation constants.

4b

5b

6b

Monomer

K_d[dm³mol^–1]^[a]

n/a

712

1.67

8.6ϫ10⁴

729

1.49

2.4ϫ10⁷

719

1.47

λ_max[nm]^[b]

ε

_maxϫ10⁵[dm³mol^–1cm^–1]^[b]

Dimer

λ_max[nm]^[b]

n/a

664

0.43

624

0.40

_maxϫ10⁵[dm³mol^–1cm^–1]^[b]

[a] Dimerisation constants were calculated according to the mathe-

matical method explained in the Experimental Section. [b] Data

were obtained from the absorption spectra in THF.

Table 6. Half-wave redox potentials^[a]of the compounds [V] vs.

SCE in THF.

[b]

Compound

Red₃

Red₂

Red₁

Oxd₁

Oxd₂

In an effort to explain the large differences in aggregation

behaviour of the isomers, quantum chemical calculations of

the charges on nitrogen and sulfur atoms were performed.

Given that the thiazole rings in 4b and 6b are annelated at

the same positions, the only difference that can cause

changes in aggregation is the position of the S and N atoms.

The charges based on electrostatic potential are presented

in Figure 6. In compound 4b, the nitrogen atoms have large

negative charges (regions marked with blue) and are local-

4b

5b

–1.91

–1.95

–1.83

–1.47

–1.44

–1.22

–1.21

–1.06

–1.23

–1.17

–0.63

–0.69

–0.57

–0.80

–0.89

0.82

0.68

0.86

0.95

0.65

–

1.12

–

1.27

1.03

6b

tBu-Pc^[c]

tBu-Nc^[c]

[a] For details of the conditions, see the Experimental Section.

[b] Potentials were recorded by using SW voltammetry. [c] Mea-

sured in CH₂Cl₂, data obtained from ref.^[25]

There are two effects of the thiazole rings fused to the

ised very close to each other, which can hinder the forma- phthalocyanine core that contribute to the redox behaviour.

tion of dimer species. This may explain why there is no ag- First, enhanced conjugation, which leads to positive shifts

gregation in the solution of this isomer. The nitrogen atoms of the first reduction and negative shifts for the first oxid-

in 5b are more remote and formation of dimers is possible. ation potentials when compared with the parent tert-butyl-

The repulsion between charges on the nitrogen atoms in ated phthalocyanine (tBu-Pc). These shifts result in lower

Figure 6. Calculated ESP maps (PBE0/def2-TZVP) of 4b–6b. Negatively charged areas are marked with blue, positively charged areas are

shown in red.

7060

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

Table 7. HOMO and LUMO energy level values determined from experimental cyclic voltammetry (cv) and theoretical calculations (th),

and band gap energy values found from UV/Vis measurements. All values are given in eV.

Compound

Electrochemistry

Theoretical calculations

UV/Vis absorption band edge

cv[a]

th[b]

opt[c]

HOMO_cv

LUMO_cv

E_g

HOMO_th

LUMO_th

E_g

4b

5b

6b

–5.06

–4.92

–5.10

–3.61

–3.55

–3.67

1.45

1.37

1.43

–5.46

–5.31

–5.58

–3.14

–3.29

2.32

2.17

2.29

1.74

1.70

1.72

[a] Potential difference between the first oxidation and the first reduction processes. Measurements in THF solution. [b] The difference

between the calculated energies (M06/def2-TZVP, solvent THF) of HOMO and LUMO. [c] Optical band gap, calculated from the intersec-

tion of normalised absorption and emission spectra recorded in THF solution.

potential differences corresponding to the HOMO–LUMO extension) on the electrochemistry of metal-free Pcs can be

gap, and are in line with the general trend in the tetraaza- reasonably explained by considering the frontier molecular

porphyrin, Pc and Nc series.^[25]The obtained values for the orbital energy levels of the corresponding compounds ob-

studied compounds are smaller than ΔE for analogous tained by DFT calculations. The values of the band gap

phthalocyanine even for naphthalocyanine. Low potential energy (E_g^cv) obtained from cyclic voltammetry were in ac-

differences caused by an extension of the π-conjugated sys- cordance with the values determined from the absorption

tem in metal-free Pcs can be reasonably explained by con- spectra (E_g^opt). The order of the HOMO–LUMO gaps

sidering the energy levels of frontier molecular orbitals of (E_g^cv) for 4b, 5b and 6b decreases linearly with increasing

corresponding compounds, which were obtained by DFT position of the Q-band maxima (712, 729 and 719 nm,

calculations. The second effect can be assigned to the elec- respectively). Although the PCM model (see Computa-

tron-withdrawing character of the thiazole ring. This fea- tional Details) was used for theoretical calculations, in

th

ture is expressed in more positive values for both first oxid- which the impact of solvent is included, the E_gabsolute

ation and first reduction potentials in comparison with tert- values differ from the electrochemical values. On the other

butyl-substituted naphthalocyanines.

hand, the order of the computed HOMO–LUMO energy

When the different modes of annelation were compared, gaps correlates well with the trends in E_g^cvand E_g^opt. Long-

the linear pattern in 5b showed significantly higher cathodic wave absorption bands (λ_A) calculated by TD-DFT (see

shift for both first oxidation as well as for first reduction Computational details), summarised in Table 4, represent

potential. Given that the shift for oxidation is more notable, the lowest excitation energies that are needed for electron

the potential difference expressed also as the HOMO– transfer from HOMO to LUMO; that is, the energy gap.

LUMO gap is smaller. The order of the HOMO–LUMO These values are in better agreement with E_g^opt, with the

gaps for 4b, 5b and 6b is in accord with the wavelengths of differences being only 0.08–0.13 eV.

the Q-band absorption and correlates well with the results

of the calculations. The angular pattern of annelation ob-

served in 4b and 6b isomers can be considered as a substitu-

tion in the α-position of the Pc core. This indicated that the

Conclusions

introduction of either N or S atoms at the α-position had a

Two sets of macrocyclic compounds were prepared from

smaller effect than annelation at the β-position, although benzothiazoledicarbonitriles either with methyl or with tert-

the substitution at the non-peripheral positions generally butyl substituents on the thiazole ring. Required dicarbo-

affords a more significant effect on the electrochemistry.

nitrile precursors were synthesised through two multistep

For potential applications of the studied compounds, routes starting either from nitroaniline or from phthalo-

valuable information can be deduced from molecular or- nitrile derivatives. Tetramerizations of benzothiazoledi-

bital energy levels and HOMO–LUMO energy gaps. These carbonitriles proceeded with moderate yields when nitrile

data can be determined from electrochemical measure- groups were in the 5,6- or 6,7-positions on the benzothi-

ments, from the UV/Vis absorption band or by theoretical azole. The failure of the 4,5-dicarbonitrile isomer to cyclise

calculations.^[26]Each of these methods represents a slightly because of unfavourable formation of the dimeric interme-

different approach. Whereas the optical gap represents the diate was explained by DFT calculations. The effect of the

transition of an electron from HOMO to LUMO of a position of the annelated thiazole rings attached to the

molecule without changing its electric charge, the electro- phthalocyanine skeleton on the optical and electronic prop-

chemical gap denotes the disproportionation reaction of the erties was examined. Characteristic electronic absorption

molecule in which two ions of opposite charges are gener- spectra of the prepared annelated phthalocyanines showed

ated. Given that the electrochemical measurements are car- bathochromic shift of the Q-band from 20 to 40 nm in rela-

ried out in a solvent, the free energies of solvation of the tion to the parent phthalocyanine. The positions of the ab-

neutral molecule and its anion have to be taken into ac- sorption maxima are in good agreement with theoretical

count, as explained by Parker.^[27]The attained data for Pcs values obtained by DFT calculations because they reflect

4b–6b are summarised in Table 7 and in Figure S11.

the energy levels between HOMO and LUMO in the sur-

Low potential differences caused by thiazole ring anne- veyed molecules. All isomeric thiazole annelated macro-

lation and changes in the ring size (π-conjugated system cycles exhibit lower fluorescence quantum yields compared

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7061

A. Fülöpová et al.

FULL PAPER

was as follows: A stock solution of DPBF in THF (5ϫ10^–5m,

2.5 mL) was transferred into a 10ϫ10 mm quartz optical cell and

bubbled with oxygen for 1 min. A defined amount of concentrated

stock solution of the tested compound in THF (usually 20 μL) was

added. Absorbance of the final solution in Q-band maximum was

always ca. 0.1. The solution was stirred and irradiated for defined

times with a xenon lamp (100 W, ozone free XE DC short arc lamp,

Newport). Incident light was filtered through a water filter (6 cm)

and cut-off filter OG530 to remove heat and light under 523 nm,

respectively. Decrease of DPBF in solution with irradiation time

with unsubstituted phthalocyanine. On the other hand, the

quantum yields of the prepared phthalocyanines are higher

than those of the isoelectronic naphthalocyanines. The elec-

trochemical behaviour of the studied compounds proved

the high levels of conjugation; this was expressed by the

difference of the first redox potentials, which were lower

than the analogous redox potentials of naphthalocyanine.

According to the values for the first oxidation potentials,

the most stable isomer appears to be the angular isomer

with sulfur atoms in nonperipheral positions. The electro- was monitored at 414 nm. The Φ_Δof the tested compound was

calculated from Equation (3).

chemical data correlate well with the results of the DFT

calculations. Thermal stability studies showed that the

angular isomer is more stable than the linear derivative.

(3)

where k is a slope of the plot of the dependence of ln(A₀/A_t) on

irradiation time t, with A₀and A_tbeing the absorbances of DPBF

at 414 nm before irradiation and after irradiation time t, respec-

tively. I_aTis the total amount of light absorbed by the tested com-

pound. Superscripts R and S indicate reference and sample, respec-

tively. I_aTis calculated as a sum of intensities of the absorbed light

I_aat wavelengths from 523 to 850 nm (step 0.5 nm). Light under

523 nm is completely filtered off by using a OG530 filter and light

above 850 nm is not absorbed by the tested compound. I_aat given

wavelength is calculated from Beer’s law, see Equation (4).

Experimental Section

General Methods: Reagents were purchased from commercial

sources and used without further purification unless stated other-

wise. Solvents were purified and dried using common methods.

Column chromatography was carried out on silica gel Merck-60

(230–400 mesh, 60 Å), and TLC on aluminium sheets pre-coated

with silica gel 60 F₂₅₄(E. Merck). Melting points were measured

with a Kofler apparatus Electrothermal IA-9200. Simultaneous

TGA-DTA was carried out with a sdt 2960 (T. A. Instruments),

from ambient temperature to 900 °C with a heating rate of

20 °Cmin^–1in an atmosphere of air. The standard software pack-

age of T. A. Instruments was used for analysis and interpretation

of both TGA and DTA data of each studied probe. UV/Vis spectra

were obtained with a HP 8452A diode array spectrophotometer

(Hewlett–Packard, USA). Solution fluorescence was measured in a

1 cm cuvette with a FSP 920 (Edinburgh Instruments, UK) spectro-

fluorimeter in a right-angle arrangement. Fluorescence quantum

yield (Φ_F) was determined from Equations (1) and (2) by using an

integrating sphere (Edinburgh Instruments).

I_a= I₀(1 – e^–2.3A

)

(4)

where I₀is a transmittance of the filter at the given wavelength and

A is the absorbance of the tested compound at this wavelength. All

experiments were performed three times and data presented in the

paper represent a mean of these three experiments. The estimated

error was Ϯ15%.

IR spectra were recorded with a Thermo Scientific Nicolet iS10

spectrometer (Smart iTR diamond ATR) at room temperature.

MALDI-MS spectra were acquired with an UltrafleXtreme

MALDI-TOF/TOF mass spectrometer (Bruker Daltonics) in re-

flector mode with positive polarity using a smartbeam-II laser

working at 250 Hz. HRMS analyses were performed with an

ORBITRAP VELOS PRO instrument, Thermo Scientific with

APPI ionisation by using a krypton lamp and methanol/water (1:1)

solution as dopant. ¹H and ¹³C NMR spectra were recorded with a

Varian NMR System 300 (300 MHz) spectrometer or with a Varian

NMR System 600 (600 MHz) in CDCl₃or [D₆]DMSO with tet-

ramethylsilane (TMS) as internal standard. Elemental analyses

were measured with a Carlo–Erba instrument, model 1106 SCI-

ENCE and Vario MICRO CUBE analyser (Elementar). Dimeris-

ation constants were calculated according to a nonlinear fitting

method.^[29]UV/Vis spectra of the chosen samples were recorded in

THF at different concentrations ranging from 10^–5to 10^–8m using

a 1 cm quartz cell. Pcs are known to exist in solutions in the form

of monomers, dimers, trimers and oligomers. We assumed that in

such dilute solutions (under 10^–4m) no higher aggregates than

dimers are formed. In this case, the dimerisation constant (K_d) of

monomer–dimer equilibrium, total concentration (C_t) and ab-

sorbance (A) measured at concentration C_tcan be expressed as

shown in Equation (5).

(1)

(2)

where L_Samis the area under the detected spectrum in the part of

the spectrum where sample emission occurs, E_Refis area under the

reflection part of the detected spectrum using pure solvent as refer-

ence material (diffuse reflectance), E_Samis area under the reflection

part of the detected spectrum after absorption by sample and a

is reabsorbed area. Time-resolved fluorescence measurements were

performed with a FSP 920 (Edinburgh Instruments, UK) spectro-

fluorimeter with

(TCSPC) module and a red-sensitive high-speed photomultiplier in

peltier housing, featuring Hamamatsu H5773–04 detector

a

time-correlated single-photon counting

a

(R928P detector; Edinburgh Photonics, UK). Excitation source

was a 402.8 nm picosecond pulsed diode laser (Model EPL-405;

Pulse Width: 60.5 ps; Edinburgh Photonics, UK). Reconvolution

fit analysis software (F900, Edinburgh Instruments) was used for

lifetime data analysis. Singlet oxygen quantum yields (Φ_Δ) were de-

termined in THF by using the decomposition of 1,3-diphenyliso-

benzofuran (DPBF) with unsubstituted zinc phthalocyanine

(ZnPc) as reference (Φ_Δ(THF)= 0.53).^[28]In detail, the procedure

(5)

where ε_mis the extinction coefficient (dm³mol^–1cm^–1) of the mono-

mer at

a given wavelength, ε_dis the extinction coefficient

7062

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

(dm³mol^–1cm^–1) of the dimer at a given wavelength. In Equa- N-(2-Bromo-5-nitrophenyl)pivalamide (8b):

A suspension of 2-

tion (5), A and C_tare measurable quantities and parameters ε_m, ε_d

and K_dwere determined by nonlinear regression using the series of

concentrations and corresponding absorbances at maximum of the

Q-band of the monomer of each sample measured. Nonlinear re-

gression was computed in the Microsoft Office Excel 2013 environ-

ment by using the Solver add-in.

bromo-5-nitroaniline (7; 5 g, 0.023 mol) in excess pivalic anhydride

(30 mL) was vigorously stirred and a catalytic amount of concen-

trated sulfuric acid was added. The reaction mixture was heated to

170 °C under a nitrogen atmosphere for 1 h. The residue was tritu-

rated with diethyl ether/hexane (1:1) after cooling, filtered off, and

dried to give 8b as white crystals. The product can be crystallised

from cyclohexane, yield 5.97 g (86%); m.p. 187.5–188 °C (cyclohex-

1

The electrochemical measurements (i.e., cyclic voltammetry and

square wave voltammetry) were performed at room temperature

with an Autolab PGSTAT101 potentiostat. The measurements

were carried out with a three-electrode setup consisting of a Pt

working electrode, a Pt counter electrode, and an Ag/AgCl/Cl^–ref-

erence electrode separated from the bulk solution by an integrated

salt bridge. Reference electrode consisted of an inner compartment

containing 3 m KCl in water and an outer compartment with 0.1 m

Bu₄NPF₆in acetonitrile. The detailed procedure was as follows:

0.1 m solution of tetrabutylammonium hexafluorophosphate

(Bu₄NPF₆) in anhydrous THF (5 mL), serving as a supporting elec-

trolyte, was added to the cell and bubbled with nitrogen for 5 min

to remove residual oxygen. The studied compound (5 mg) was

added and bubbling was continued for 5 min. Half-wave potentials

were recorded from square wave voltammetry with a potential step

of 5 mV and a scan rate of 100 mVs^–1. Ferrocene as an internal

standard was then added and the measurements repeated and used

to determine half-wave potentials. The obtained data listed in

Table 6 are referenced to SCE; they were corrected according to

the reported value for ferrocene vs. SCE in the given solvent

{E_(Fc/Fc+)= 0.56 V vs. SCE [THF/Bu₄NPF₆]}.^[30]HOMO and

LUMO energy levels of compounds were calculated by using the

HOMO level of ferrocene at –4.8 eV and the first oxidation and

first reduction values of 4b–6b in THF. Equation (6) and Equa-

tion (7) were used to calculate HOMO and LUMO energy levels,

respectively:

ane). H NMR (300 MHz, CDCl₃): δ = 9.35 (d, J = 2.7 Hz, 1 H,

H-C6), 8.14 (br. s, 1 H, NH), 7.84 (dd, J = 8.8, 2.7 Hz, 1 H, H-

C4), 7.72 (d, J = 8.8 Hz, 1 H, H-C3), 1.38 (s, 9 H, CH₃) ppm. ¹³C

NMR (75 MHz, CDCl₃): δ = 177.1, 148.0, 137.0, 132.7, 119.9,

119.2, 116.2, 40.6, 27.6 (3ϫ C) ppm. C₁₁H₁₃BrN₂O₃(301.14):

calcd. C 43.87, H 4.35, N 9.30; found C 43.69, H 4.14, N 8.72. IR

(ATR): ν = 3405 (N-H), 3126 (C-H Ar), 2959 (C-H), 1702 (C=O),

˜

1538, 1416, 1370, 1339 (C-H), 1311, 1239, 1148, 1030, 920, 899,

826 cm^–1.

2-tert-Butyl-5-nitrobenzothiazole (9b): To a solution of 8b (5.9 g,

19.6 mmol) in ethanol (75 mL), a mixture of sulfur (0.63 g,

19.6 mmol) and sodium sulfide nonahydrate (4.7 g, 19.6 mmol) was

added. The crimson-coloured suspension was stirred and heated to

reflux for 3 h and then filtered off while still hot. The mixture was

cooled to ambient temperature and then diluted with water

(100 mL) and made slightly acidic with concentrated HCl to cause

precipitation. The resulting suspension was boiled for 5 min and

then cooled. The pale-yellow precipitate was washed with water

1

and dried, yield 4.5 g (97%); m.p. 72–73 °C. H NMR (300 MHz,

CDCl₃): δ = 8.85 (d, J = 2.2 Hz, 1 H, H-C4), 8.23 (dd, J = 8.8,

2.2 Hz, 1 H, H-C6), 7.97 (d, J = 8.8 Hz, 1 H, H-C7), 1.54 (s, 9 H,

CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 185.8, 153.2, 146.8,

141.9, 122.0, 119.3, 118.4, 39.0, 30.7 (3ϫ C) ppm. HRMS (ESI):

m/z calcd. for C₁₁H₁₂N₂O₂S [M + H]⁺237.0692; found 237.0693.

IR (ATR): ν = 3100 (C-H Ar), 2975 (C-H), 1598, 1505, 1420, 1345

˜

(C-H), 1307, 1246, 1145, 1071, 1009, 890, 818, 740 cm^–1.

E_HOMO= –[(E_ox– E_{1/2 (ferrocene)}) + 4.8]

E_LUMO= –[(E_red– E_{1/2 (ferrocene)}) + 4.8]

(6)

(7)

2-tert-Butylbenzothiazol-5-amine (10b): To a solution of 9b (2.1 g,

8.9 mmol) in 80% ethanol (70 mL), hydrochloric acid (1.15 mL,

0.013 mol, 1.5 equiv.), and carbonyl-iron powder (1.49 g,

0.027 mol, 3 equiv.) were added. The reaction mixture was soni-

cated (power 80%) for 2ϫ 30 min. The solid part was removed by

filtration through Celite and washed with ethanol. Ethanol was

evaporated and the residue was dissolved in CHCl₃(150 mL). The

precipitate that formed after neutralisation with a saturated solu-

tion of Na₂CO₃was filtered off. The organic layer was separated

and again extracted with a saturated solution of Na₂CO₃and brine.

The organic layer was dried with Na₂SO₄and concentrated under

vacuum to obtain the crude product (1.65 g), which was purified

by column chromatography on silica gel (hexane/ethyl acetate, 4:1)

to afford a pale-brown solid, yield 1.43 g (78%); m.p. 109–110 °C.

¹H NMR (300 MHz, CDCl₃): δ = 7.57 (d, J = 8.5 Hz, 1 H, H-C7),

7.29 (d, J = 2.2 Hz, 1 H, H-C4), 6.75 (dd, J = 8.5, 2.3 Hz, 1 H, H-

C6), 3.50 (br. s, 2 H, NH₂), 1.49 (s, 9 H, CH₃) ppm. ¹³C NMR

(75 MHz, CDCl₃): δ = 182.9, 154.8, 145.2, 125.0, 121.8, 114.5,

107.9, 38.4, 30.8 (3ϫ C) ppm. C₁₁H₁₄N₂S (206.31): calcd. C 64.04,

H 6.84, N 13.58, S 15.54; found C 63.90, H 6.83, N 13.32, S 15.76.

Computational Details: The optimal geometries for each compound

in vacuo were calculated with the Turbomole 6.6 program,^[31]using

the DFT method^[32]and the PBE0 exchange-correlation func-

tional.^[33]The def2-TZVP basis set^[34]was employed for all atoms.

Optimal geometries were confirmed by calculating infrared spectra

with no negative frequencies. To calculate the ESP charges a para-

metrisation very close to that used by Kollman^[35]was used. Lowest

transition energies [λ_A(calc.)], oscillator strengths (f) and molec-

ular orbital energies (E_HOMO, E_LUMO, ΔE_(H–L)) using the time-de-

pendent DFT (TD-DFT) method^[36]were calculated with Gaussian

09 program^[37]applying M06 functional^[38]and TZVP basis set^[39]

(for phthalocyanine derivatives) or B3-LYP functional^[40]and 6-

31+G(d) basis set^[41](for benzothiazoledicarbonitriles). The polar-

izable continuum model (PCM)^[42]was used to perform the compu-

tations with the inclusion of tetrahydrofuran or chloroform as sol-

vent. Absorption spectra experimental peak values of 4b–6b were

determined with the help of the curve fitting program Fityk

v.0.9.8.^[43]

IR (ATR): ν = 3459, 3331 (NH ), 3218 (C-H Ar), 2956 (C-H),

˜

2

1735, 1629, 1601 (NH₂), 1499, 1471, 1431, 1366 (C-H), 1316, 1254,

1222, 1081, 1012, 852, 799 cm^–1.

Remarks About Nomenclature: The name benzothiazole was used

for benzo[d]thiazole throughout the whole article.

N-(2-tert-Butylbenzothiazol-5-yl)acetamide (11b): Amine 10b (4.9 g,

0.024 mol) was dissolved in dried THF (14 mL). Acetanhydride

(3.8 mL, 0.04 mol, 1.7 equiv.) and a catalytic amount of 4-dimethyl-

aminopyridine (DMAP) (0.31 g, 10 mol-%) were added and the

mixture was stirred at room temperature for 24 h. THF was evapo-

Compounds 8a–11a were prepared and purified according to re-

ported procedures.^[12]Melting points and spectroscopic data are in

accordance with reported values.

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7063

A. Fülöpová et al.

FULL PAPER

rated and the residue was crystallised from cyclohexane to give 11b

4-Bromo-2-tert-butylbenzothiazol-5-amine (13b): A mixture of acet-

as a white solid, yield 4.35 g (74%); m.p. 148–149 °C (cyclohexane). amide 12b (3 g, 9.17 mmol) and concentrated HCl (16 mL) in eth-

¹H NMR (300 MHz, CDCl₃): δ = 8.07 (d, J = 1.1 Hz, 1 H, H-C4),

7.75 (d, J = 8.6 Hz, 1 H, H-C7), 7.58 (dd, J = 8.6, 1.5 Hz, 1 H, H-

C6), 7.43 (br. s, 1 H, NH), 2.21 (s, 3 H, COCH₃), 1.51 (s, 9 H,

CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 183.4, 168.7, 153.9,

136.4, 130.7, 121.7, 118.0, 113.8, 38.5, 30.8 (3ϫ C), 24.7 ppm.

C₁₃H₁₆N₂OS (248.34): calcd. C 62.87, H 6.49, N 11.28, S 12.91;

anol (30 mL) was stirred and heated to reflux for 1.5 h. After cool-

ing, the reaction mixture was poured into water and neutralised

with K₂CO₃. The precipitate was extracted with CHCl₃(3ϫ

50 mL), dried with Na₂SO₄and concentrated under vacuum. The

product was purified on silica gel column (hexane/ethyl acetate, 5:1)

to give a beige solid, yield 2.48 g (95%); m.p. 71.5–73 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 7.52 (d, J = 8.5 Hz, 1 H, H-C7), 6.81 (d,

J = 8.5 Hz, 1 H, H-C6), 4.21 (br. s, 2 H, NH₂), 1.51 (s, 9 H,

CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 183.3, 152.5, 142.9,

125.0, 120.5, 114.3, 102.0, 38.7, 30.9 (3ϫ C) ppm. C₁₁H₁₃BrN₂S

(285.20): calcd. C 46.32, H 4.59, N 9.82, S 11.24; found C 46.80,

found C 62.89, H 6.51, N 11.24, S 12.89. IR (ATR): ν = 3261 (N-

˜

H), 3083, 3053 (C-H Ar), 2962 (C-H), 1658 (C=O), 1582, 1533,

1503, 1460, 1364 (C-H), 1287, 1248, 1048, 1018, 880, 820, 689 cm^–1.

N-(4-Bromo-2-methylbenzothiazol-5-yl)acetamide (12a): Acetamide

11a (1.6 g, 7.76 mmol) was dissolved in glacial acetic acid (30 mL).

The mixture was gently heated and Br₂(0.4 mL, 1.24 g, 7.76 mmol)

in glacial acetic acid (7 mL) was added dropwise. The reaction was

stirred for 2 h at room temperature, then the solution was diluted

with water (100 mL) and neutralised with ammonia. The resulting

precipitate was filtered off, washed with water and dried. The prod-

uct was purified on silica gel column (hexane/ethyl acetate, 1:1) to

give a white solid, yield 1.83 g (83%); m.p. 170.5–171.5 °C. (cyclo-

H 4.78, N 9.79, S 11.28. IR (ATR): ν = 3474, 3374 (NH ), 3196

˜

2

(C-H Ar), 2961 (C-H), 1612, 1594 (NH₂), 1471, 1407, 1359 (C-H),

1313, 1226, 1100, 1047, 1012, 984, 802, 619 cm^–1.

4,5-Dibromo-2-methylbenzothiazole (14a): A mixture of copper(I)

bromide (0.32 g, 2.22 mmol, 1.2 equiv.) in anhydrous acetonitrile

(10 mL) was stirred under a nitrogen atmosphere. tert-Butyl nitrite

(0.33 mL, 0.29 g, 2.78 mmol, 1.5 equiv.) was added in one portion

and heated to 60 °C. After 10 min, amine 13a (0.45 g, 1.85 mmol)

1

hexane). H NMR (300 MHz, CDCl₃): δ = 8.37 (d, J = 8.8 Hz, 1

H, H-C6), 7.77 (s, 1 H, NH), 7.73 (d, J = 8.8 Hz, 1 H, H-C7), 2.87 was added and the mixture was stirred for 1 h at 60 °C. After cool-

(s, 3 H, CH₃), 2.29 (s, 3 H, COCH₃) ppm. ¹³C NMR (75 MHz, ing, the reaction mixture was dissolved in CHCl₃(50 mL). The or-

CDCl₃): δ = 169.3, 168.4, 151.6, 134.3, 131.1, 120.5, 119.0, 106.4,

ganic layer was washed with 1 m hydrochloric acid (50 mL) and

24.9, 20.4 ppm. C₁₀H₉BrN₂OS (285.16): calcd. C 42.12, H 3.18, N brine (50 mL), and dried with Na₂SO₄. After evaporation of the

9.82, S 11.24; found C 41.97, H 3.12, N 9.74, S 11.23. IR (ATR): solvent, the crude product was purified by chromatography on sil-

ν = 3281 (N-H), 3062 (C-H Ar), 2921, 1656 (C=O), 1557, 1519, ica gel (hexane/ethyl acetate, 7:1) to afford a white solid, yield

˜

1

1400, 1369 (C-H), 1305, 1256, 1158, 1095, 1039, 982, 805, 785 cm^–1.

0.38 g (67%); m.p. 157–159 °C. H NMR (300 MHz, CDCl₃): δ =

7.63 (d, J = 8.5 Hz, 1 H, H-C7), 7.57 (d, J = 8.5 Hz, 1 H, H-C6),

2.88 (s, 3 H, CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 169.5,

153.4, 134.8, 129.4, 122.9, 121.2, 119.0, 20.5 ppm. C₈H₅Br₂NS

(307.00): calcd. C 31.30, H 1.64, N 4.56, S 10.44; found C 31.37,

N-(4-Bromo-2-tert-butylbenzothiazol-5-yl)acetamide (12b): Acet-

amide 11b (4.22 g, 0.017 mol) was dissolved in glacial acetic acid

(50 mL). The mixture was gently heated and Br₂(2.72 g, 0.017 mol)

in glacial acetic acid (15 mL) was added dropwise. The reaction

was stirred for 4 h at room temperature, then the solution was di-

luted with water (100 mL) and neutralised with ammonia. The re-

sulting precipitate was filtered off, washed with water and dried.

The product was purified on silica gel column (hexane/ethyl acetate,

2:1) to give a white solid. Isomeric o-bromoderivative was also ob-

tained (0.83 g, 15%) and part of the starting material was recovered

(1.12 g, 27%), yield 3.07 g (55%); m.p. 145.5–147 °C (diethyl ether).

¹H NMR (300 MHz, CDCl₃): δ = 8.35 (d, J = 8.8 Hz, 1 H, H-C),

7.78 (br. s, 1 H, NH), 7.73 (d, J = 8.8 Hz, 1 H, H-C), 2.28 (s, 3 H,

H 1.59, N 4.43, S 10.67. IR (ATR): ν = 3073 (C-H Ar), 2993, 2922,

2851, 1870, 1729, 1517, 1415, 1372 (C-H), 1289, 1166, 1089, 995,

˜

887 cm^–1.

4,5-Dibromo-2-tert-butylbenzothiazole (14b): A mixture of cop-

per(I) bromide (1.63 g, 11.4 mmol, 1.2 equiv.) in anhydrous aceto-

nitrile (25 mL) was stirred under a nitrogen atmosphere. tert-Butyl

nitrite (1.7 mL, 1.46 g, 14.2 mmol, 1.5 equiv.) was added in one

portion and heated to 60 °C. After 10 min, amine 13b (2.7 g,

9.47 mmol) was added and the mixture was stirred for 1 h at 60 °C.

COCH₃), 1.52 (s, 9 H, CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ After cooling, the reaction mixture was dissolved in CHCl₃

= 183.8, 168.5, 151.6, 134.3, 130.9, 120.6, 118.9, 107.1, 38.9, 30.9 (100 mL). The organic layer was washed with 1 m hydrochloric acid

(3ϫ C), 25.1 ppm. C₁₃H₁₅BrN₂OS (327.24): calcd. C 47.71, H 4.62,

N 8.56, S 9.80; found C 47.32, H 4.64, N 8.45, S 9.76. IR (ATR):

(120 mL) and brine (120 mL), and dried with Na₂SO₄. After evapo-

ration of the solvent, the crude product was purified by chromatog-

raphy on silica gel (hexane/chloroform, 10:1) to afford a yellow oil,

ν = 3255 (N-H), 3056 (C-H Ar), 2964 (C-H), 1659 (C=O), 1562,

˜

1519, 1506, 1397, 1364 (C-H), 1305, 1259, 1051, 1004, 808 cm^–1.

yield 1.7 g (52%). H NMR (300 MHz, CDCl₃): δ = 7.64 (d, J =

1

8.5 Hz, 1 H, H-C7), 7.55 (d, J = 8.5 Hz, 1 H, H-C6), 1.53 (s, 9 H,

CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 183.9, 153.3, 134.3,

129.1, 122.5, 121.2, 119.5, 38.9, 30.8 (3ϫ C) ppm. HRMS (ESI):

m/z calcd. for C₁₁H₁₁Br₂NS [M + H]⁺347.9051; found 347.9059.

4-Bromo-2-methylbenzothiazol-5-amine (13a): Acetamide 12a

(1.53 g, 5.4 mmol) and concentrated HCl (10 mL) in ethanol

(15 mL) were stirred and heated to reflux for 2 h. The reaction

mixture was cooled, poured into water and neutralised with

K₂CO₃. The precipitate was collected, washed with water and dried

to give 13a as a pale-yellow solid, yield 1.13 g (87%); m.p. 129.5–

IR (ATR): ν = 3075 (C-H Ar), 2961 (C-H), 1505, 1467, 1417, 1389,

˜

1365 (C-H), 1288, 1257, 1176, 1051, 1009, 898, 792, 708, 641 cm^–1.

1

130.5 °C. The product can be recrystallised from cyclohexane. H

2-Methylbenzothiazole-4,5-dicarbonitrile (1a): To a solution of

NMR (300 MHz, CDCl₃): δ = 7.50 (d, J = 8.5 Hz, 1 H, H-C7), benzothiazole derivative 14a (0.5 g; 1.6 mmol) in 1-methylpyrrol-

6.83 (d, J = 8.5 Hz, 1 H, H-C6), 4.24 (br. s, 2 H, NH₂), 2.84 (s, 3

idin-2-one (3 mL), copper cyanide (0.58 g, 6.5 mmol, 4 equiv.) was

added and the reaction mixture was exposed to microwave irradia-

H, CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 168.8, 152.7,

143.1, 125.3, 120.5, 114.4, 101.4, 20.5 ppm. C₈H₇BrN₂S (243.12): tion for 2ϫ 20 min at 210 °C. The reaction was monitored by TLC.

calcd. C 39.52, H 2.90, N 11.52, S 13.19; found C 39.62, H 2.88, After irradiation, the mixture was cooled to room temperature, di-

N 11.43, S 13.17. IR (ATR): ν = 3426, 3328 (NH ), 3197 (C-H Ar), luted with ice water (150 mL) and stirred for 30 min. The dark

˜

2

2919, 1612 (NH₂), 1508, 1468, 1406, 1367 (C-H), 1324, 1312, 1219,

precipitate was filtered off and washed with ammonia and water.

The crude product was washed out from the precipitate several

1186, 1163, 1090, 967, 802, 659 cm^–1.

7064

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

times with CH₂Cl₂. After removing the solvent under reduced pres-

sure, the product was purified by silica gel column chromatography

(chloroform/ethyl acetate, 96:4) to give 1a as a pale-yellow solid,

acetic acid (7 mL) was heated to reflux for 2 h. After cooling, the

reaction mixture was diluted with water (30 mL) and the resulting

precipitate was filtered off, washed with water, and dried. The crude

product was purified by column chromatography on silica gel (hex-

ane/ethyl acetate, 1:1) to give 18a as a pale-yellow solid, yield 0.44 g

1

yield 0.18 g (56%); m.p. 260–261.5 °C. H NMR (300 MHz, [D₆]-

DMSO): δ = 8.65 (d, J = 8.4 Hz, 1 H, H-C7), 8.08 (d, J = 8.4 Hz,

1 H, H-C6), 2.95 (s, 3 H, CH₃) ppm. ¹³C NMR (75 MHz, [D₆]- (80%); m.p. 178–181 °C. ¹H NMR (300 MHz, [D₆]DMSO): δ =

DMSO): δ = 175.7, 153.3, 141.4, 128.5, 128.1, 116.3, 114.4, 112.5,

9.93 (s, 1 H, NH), 8.58 (s, 1 H, H-C6), 8.46 (s, 1 H, H-C3), 2.19

107.7, 20.2 ppm. C₁₀H₅N₃S (199.23): calcd. C 60.29, H 2.53, N (s, 3 H, COCH₃) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ = 169.6,

21.09, S 16.09; found C 60.24, H 2.54, N 20.95, S 16.06. IR (ATR): 141.4, 138.4, 128.7, 120.6, 115.5, 114.9, 114.2, 110.5, 23.7 ppm.

ν = 3100 (C-H Ar), 2928 (C-H), 2228 (CϵN), 1784, 1579, 1547,

Melting point is in accordance with literature.^[44]

˜

1506, 1401, 1374 (C-H), 1276, 1176, 1028, 824 cm^–1.

N-(2-Bromo-4,5-dicyanophenyl)pivalamide (18b): A suspension of

16 (0.45 g, 2 mmol) in pivalic anhydride (7 mL) and a catalytic

amount of concentrated sulfuric acid (2 drops) was stirred and

heated to 170 °C under a nitrogen atmosphere for 2 h. The pivalic

anhydride was evaporated from the cooled solution under reduced

pressure and the residue was purified by column chromatography

2-tert-Butylbenzothiazole-4,5-dicarbonitrile (1b): Prepared as de-

scribed for 1a with benzothiazole derivative 14b (0.8 g, 2.3 mmol),

CuCN (0.82 g, 9.2 mmol, 4 equiv.), 1-methylpyrrolidin-2-one

(8 mL). MW irradiation for 2ϫ 10 min at 210 °C. The product was

purified by silica gel column chromatography (hexane/ethyl acetate,

1

5:1) to give a white solid, yield 0.34 g (62%); m.p. 149–150 °C. H

on silica gel (hexane/ethyl acetate, 4:1) to give white crystals, yield

1

NMR (300 MHz, CDCl₃): δ = 8.17 (d, J = 8.3 Hz, 1 H, H-C7), 0.44 g (73%); m.p. 220–221 °C. H NMR (300 MHz, [D₆]DMSO):

7.69 (d, J = 8.3 Hz, 1 H, H-C6), 1.56 (s, 9 H, CH₃) ppm. ¹³C NMR δ = 9.30 (s, 1 H, NH), 8.60 (s, 1 H, H-C3), 8.32 (s, 1 H, H-C6),

(75 MHz, CDCl₃): δ = 188.7, 154.0, 140.8, 127.4, 126.4, 115.7, 1.26 (s, 9 H, CH₃) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ =

113.7, 113.6, 110.1, 39.3, 30.5 (3ϫ C) ppm. C₁₃H₁₁N₃S (241.31):

176.7, 141.8, 138.2, 130.5, 123.9, 115.3, 114.9, 114.2, 111.5, 39.4,

calcd. C 64.7, H 4.59, N 17.41, S 13.29; found C 64.57, H 4.61, N

26.9 (3ϫ C) ppm. C₁₃H₁₂BrN₃O (306.16): calcd. C 51.00, H 3.95,

17.14, S 13.68. IR (ATR): ν = 3087 (C-H Ar), 2968, 2869 (C-H), N 13.72; found C 49.96, H 3.87, N 13.53. IR (ATR): ν˜ = 3404

˜

2230 (CϵN), 1577, 1547, 1498, 1403, 1365 (C-H), 1276, 1259, 1150,

(NH), 3122, 2971, 2234 (CϵN), 1697 (C=O), 1561, 1509, 1390 (C-

1064, 1020, 819 cm^–1.

H), 1311, 1254, 1147, 990, 916 cm^–1.

N-(2-Bromo-3,4-dicyanophenyl)acetamide (19a): A solution of 17

(0.75 g, 3.38 mmol), acetic anhydride (0.45 g, 4.39 mmol, 0.41 mL)

and a catalytic amount of concentrated sulfuric acid (2 drops) in

glacial acetic acid (10 mL) was heated to reflux for 2 h. The pale-

yellow solid was filtered off from the cooled reaction mixture,

thoroughly washed with water and dried. The crude product was

purified by column chromatography on silica gel (hexane/ethyl

acetate, 1:1) to give 19a as a pale-yellow solid, yield 0.77 g (86%);

m.p. 215–216 °C (crystallised from acetic acid/water). ¹H NMR

(300 MHz, [D₆]DMSO): δ = 9.97 (s, 1 H, NH), 8.23 (d, J = 8.7 Hz,

1 H, H-C6), 8.09 (d, J = 8.7 Hz, 1 H, H-C5), 2.18 (s, 3 H,

COCH₃) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ = 169.4, 142.0,

133.2, 129.0, 120.0, 119.1, 115.5, 115.1, 111.8, 23.7 ppm.

C₁₀H₆BrN₃O (264.08): calcd. C 45.48, H 2.29, N 15.91; found C

4-Amino-5-bromophthalonitrile (16) and 4-Amino-3-bromophthalo-

nitrile (17): N-Bromosuccinimide (0.62 g, 3.5 mmol) was added in a

single portion to a stirred solution of 4-aminophthalonitrile (0.5 g,

3.5 mmol) in glacial acetic acid (20 mL) at room temperature. The

mixture was vigorously stirred for 45 min, then poured into water

(200 mL). The pale-yellow precipitate, which appeared immedi-

ately, was filtered off and dried. The crude product was purified by

flash chromatography on silica gel (hexane/tetrahydrofuran, 3:2) to

give 4-amino-5-bromophthalonitrile (16) followed by 4-amino-3-

bromophthalonitrile (17) as a white solid. Compound 16 can be

further separated from the dibromo by-product by using column

chromatography on SiO₂(chloroform + 0.5% triethylamine).

4-Amino-5-bromophthalonitrile (16): Yield (0.23 g, 29.5%); m.p.

207–210 °C. ¹H NMR (300 MHz, [D₆]DMSO): δ = 8.17 (s, 1 H,

H-C3), 7.19 (s, 1 H, H-C6), 6.91 (br. s, 2 H, NH₂) ppm. ¹³C NMR

(75 MHz, [D₆]DMSO): δ = 150.4, 137.9, 118.1, 116.2, 116.0, 114.5,

110.2, 99.3 ppm. Melting point is in accordance with literature.^[43]

45.62, H 2.34, N 15.63. IR (ATR): ν = 3312 (NH), 3126, 2231

˜

(CϵN), 1683 (C=O), 1506, 1389 (C-H), 1301, 1235, 1125, 1019,

854 cm^–1.

N-(2-Bromo-3,4-dicyanophenyl)pivalamide (19b): Prepared as de-

scribed for 18b with 16 (0.44 g, 1.98 mmol), excess pivalic an-

hydride (7 mL), and concentrated sulfuric acid (2 drops) at 170 °C,

2 h. The crude product was purified by column chromatography on

silica gel (hexane/ethyl acetate, 5:1) to afford white crystals, yield

0.48 g (80%); m.p. 240–241.5 °C. ¹H NMR (300 MHz, [D₆]-

DMSO): δ = 9.39 (s, 1 H, NH), 8.13 (d, J = 8.5 Hz, 1 H, H-C6),

8.04 (d, J = 8.5 Hz, 1 H, H-C5), 1.27 (s, 9 H, CH₃) ppm. ¹³C NMR

(75 MHz, [D₆]DMSO): δ = 176.7, 142.4, 133.3, 131.0, 123.1, 118.9,

115.4, 115.1, 112.8, 39.4, 26.9 (3ϫ C) ppm. C₁₃H₁₂BrN₃O (306.16):

calcd. C 51.00, H 3.95, N 13.72; found C 51.13, H 3.98, N 13.52.

4-Amino-3-bromophthalonitrile (17): Yield 0.46 g (60%); m.p. 213–

216 °C. H NMR (300 MHz, [D₆]DMSO): δ = 7.70 (d, J = 8.7 Hz,

1 H, H-C5), 7.04 (d, J = 8.7 Hz, 1 H, H-C6), 6.94 (br. s, 2 H,

NH₂) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ = 151.0, 133.4,

118.5, 117.6, 116.8, 115.6, 109.2, 100.8 ppm. C₈H₄BrN₃(222.04):

calcd. C 43.27, H 1.82, N 18.92; found C 43.73, H 1.67, N 18.97.

1

IR (ATR): ν = 3477, 3366 (NH ), 3092 (C-H Ar), 2217 (CϵN),

˜

2

1607 (NH₂), 1579, 1484, 1349, 1321, 1236, 1118, 829 cm^–1.

4-Amino-3,5-dibromophthalonitrile (By-product): M.p. 259–261 °C

1

(ethanol). H NMR (300 MHz, [D₆]DMSO): δ = 8.27 (s, 1 H, H-

C6), 6.96 (br. s, NH₂) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ =

148.3, 136.6, 117.9, 115.6, 115.4, 110.5, 109.8, 101.8 ppm.

C₈H₃Br₂N₃(300.94): calcd. C 31.93, H 1.00, N 13.96; found C

IR (ATR): ν = 3412 (NH), 3099 (C-H Ar), 2961, 2232 (CϵN),

˜

1698 (C=O), 1510, 1388 (C-H), 1309, 1144, 972, 847 cm^–1.

2-Methylbenzothiazole-5,6-dicarbonitrile (2a): To a solution of 18a

(0.44 g, 1.67 mmol) in ethanol (15 mL), a mixture of sulfur (0.05 g,

1.67 mmol, 1 equiv.) and sodium sulfide nonahydrate (0.2 g,

0.83 mmol, 0.5 equiv.) was added. The crimson-coloured suspen-

sion was stirred and heated to reflux for 1.5 h and then filtered off

while still hot. The yellow solution was cooled to room temperature

and then diluted with water (25 mL) and made slightly acidic with

31.94, H 0.87, N 13.82. IR (ATR): ν = 3474, 3359 (NH ), 3069 (C-

˜

2

H Ar), 2224 (CϵN), 1613 (NH₂), 1469, 1307, 1235, 1148, 1001,

907 cm^–1.

N-(2-Bromo-4,5-dicyanophenyl)acetamide (18a): A solution of 16

(0.47 g, 2.1 mmol), acetic anhydride (0.31 g, 3 mmol, 0.3 mL) and

a catalytic amount of concentrated sulfuric acid (2 drops) in glacial

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7065

A. Fülöpová et al.

FULL PAPER

concentrated HCl to cause precipitation. The resulting suspension

was boiled for 5 min and then cooled. The orange precipitate was

collected after cooling, washed with water, dried and then purified

by silica gel column chromatography (hexane/ethyl acetate, 1:2) to

give the desired product as a yellow solid, yield 0.23 g (70%); m.p.

tion mixture was cooled and poured into methanol containing a

few drops of HCl and the precipitate was filtered off. The green

product was washed several times with distilled water, hot meth-

anol, acetone, acetonitrile, and diethyl ether to remove the remain-

ing organic impurities. The crude product 4b–6b was dissolved in

237–239 °C. ¹H NMR (300 MHz, [D₆]DMSO): δ = 8.96 (d, J = chloroform and purified by silica gel column chromatography using

0.5 Hz, 1 H, H-C4), 8.77 (s, 1 H, H-C7), 2.92 (s, 3 H, CH₃) ppm. an appropriate eluent and finally the product was washed with hot

¹³C NMR (75 MHz, [D₆]DMSO): δ = 175.5, 154.6, 140.6, 129.4, methanol.

127.8, 116.3, 116.2, 111.4, 109.0, 20.3 ppm. C₁₀H₅N₃S (199.23):

calcd. C 60.29, H 2.53, N 21.09, S 16.09; found C 60.21, H 2.64,

2,3,9,10,16,17,23,24-Tetrakis[2Ј-methyl[1Ј,3Ј]thiazolo]phthalocyan-

ine and Other Randomers (5a): Precipitation from concentrated

sulfuric acid into ice water solution, the crude product was washed

with KOH (20 mL) and by extraction on Soxhlet (solvent meth-

anol) to give the product as a dark-green solid, yield 0.052 g (42%);

m.p. 467 °C (decomp.). C₄₀H₂₂N₁₂S₄(798.93): calcd. C 60.13, H

N 20.94, S 16.19. IR (ATR): ν = 3106, 3018 (C-H Ar), 2962 (C-

˜

H), 2230 (CϵN), 1789, 1594, 1497, 1448, 1379 (C-H), 1270, 1197,

1168, 1129, 1026, 896, 804 cm^–1.

2-tert-Butylbenzothiazole-5,6-dicarbonitrile (2b): Prepared as de-

scribed for 2a with 18b (0.44 g, 1.44 mmol), sulfur (0.046 g,

1.44 mmol), Na₂S·xH₂O (0.17 g, 0.72 mmol) and EtOH (25 mL).

The reaction mixture was heated to reflux for 2 h. Purification by

silica gel column chromatography (hexane/ethyl acetate, 5:1) gave

the desired product as pale-yellow, needle-like crystals, yield 0.27 g

2.78, N 21.04; found C 59.75, H 2.94, N 20.61. IR (ATR): ν = 3284

˜

(N-H), 3071, 2920, 2850 (C-H), 1715, 1608, 1521, 1434, 1402, 1369

(C-H), 1324, 1161, 1018, 878, 745 cm^–1. UV/Vis (H₂SO₄): λ_max

=

821, 780 nm. MS (MALDI-TOF): m/z calcd. for C₄₀H₂₂N₁₂S₄[M

+ H]⁺799.1; found 799.1.

1

(77%); m.p. 179.5–181 °C. H NMR (300 MHz, CDCl₃): δ = 8.37

3,4,10,11,17,18,24,25-Tetrakis[2Ј-methyl[1Ј,3Ј]thiazolo]phthalocyan-

ine and Other Randomers (6a): Precipitation from concentrated sul-

furic acid into ice water solution and extraction on Soxhlet (solvent

methanol) gave a dark-green solid, yield 0.056 g (45%); m.p. 515 °C

(decomp.). C₄₀H₂₂N₁₂S₄(798.93): calcd. C 60.13, H 2.78, N 21.04;

(d, J = 0.5 Hz, 1 H, H-C4), 8.32 (d, J = 0.4 Hz, 1 H, H-C7), 1.55

(s, 9 H, CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 189.4, 155.2,

140.1, 128.4, 128.0, 115.8, 115.7, 112.6, 110.4, 39.4, 30.7 (3ϫ

C) ppm. C₁₃H₁₁N₃S (241.31): calcd. C 64.70, H 4.59, N 17.41, S

13.29; found C 64.80, H 4.68, N 16.95, S 13.57. IR (ATR): ν =

˜

found C 59.67, H 3.01, N 20.73. IR (ATR): ν = 3288 (N-H), 3060,

˜

3086 (C-H Ar), 2964, 2931, 2870 (C-H), 2232 (CϵN), 1738, 1497,

1450, 1366 (C-H), 1271 (C–N), 1061, 1005, 902 cm^–1.

2923, 2853 (C-H), 2564, 1719, 1585, 1501, 1420, 1370 (C-H), 1341,

1321, 1228, 1028, 882, 821, 744 cm^–1. UV/Vis (H₂SO₄): λ_max

=

2-Methylbenzothiazole-6,7-dicarbonitrile (3a): Prepared as de-

scribed for 2a with 19a (0.77 g, 2.92 mmol), sulfur (0.09 g,

2.92 mmol), Na₂S·xH₂O (0.35 g, 1.46 mmol) and EtOH (20 mL).

The reaction mixture was heated to reflux for 1.5 h. Purification

by silica gel column chromatography (chloroform) gave the desired

product as a yellow solid, yield 0.48 g (83%); m.p. 208–209 °C

767 nm. MS (MALDI-TOF): m/z calcd. for C₄₀H₂₂N₁₂S₄[M +

H]⁺799.1; found 799.0.

1,2,8,9,15,16,22,23-Tetrakis[2Ј-tert-butyl[1Ј,3Ј]thiazolo]phthalocyan-

ine and Other Randomers (4b): Purified by column chromatography

(SiO₂, chloroform) to give a green crystalline compound, yield

0.046 g (31 %). ¹H NMR (600 MHz, CDCl₃): δ = 9.60 (d, J =

7.6 Hz, 1 H), 9.43 (dd, J = 7.5, 1.8 Hz, 0.55 H), 9.37 (d, J = 7.7 Hz,

0.6 H), 9.31 (d, J = 7.7 Hz, 0.6 H), 9.16 (d, J = 7.8 Hz, 0.6 H),

9.06 (d, J = 7.9 Hz, 0.5 H), 8.57 (d, J = 7.9 Hz, 0.3 H), 8.54 (d, J

= 7.8 Hz, 0.5 H), 8.50 (d, J = 7.8 Hz, 1.4 H), 8.44 (d, J = 7.8 Hz,

0.55 H), 8.41 (d, J = 7.9 Hz, 0.6 H), 8.39 (d, J = 7.8 Hz, 0.5 H),

2.05–1.99 (m, 34 H), 1.70 (s, 2 H), –0.3 (s, 0.3 H), –1.33, –1.41 (br.

s, 2 H) ppm. ¹³C NMR (151 MHz, CDCl₃): δ = 185.1–184.0, 152.1–

149.7, 148.8–148.6, 147.8–147.7, 139.0–138.8, 137.5–135.7, 128.9–

128.2, 123.0–122.7, 119.9–119.3, 39.5–39.4, 31.9–31.5 ppm. IR

1

(crystallised from methanol). H NMR (300 MHz, [D₆]DMSO): δ

= 8.42 (d, J = 8.5 Hz, 1 H, H-C4), 8.18 (d, J = 8.5 Hz, 1 H, H-

C5), 2.95 (s, 3 H, CH₃) ppm. ¹³C NMR (75 MHz, [D₆]DMSO): δ

= 173.6, 155.2, 140.1, 130.9, 127.1, 116.0, 114.7, 111.3, 108.8,

20.4 ppm. C₁₀H₅N₃S (199.23): calcd. C 60.29, H 2.53, N 21.09, S

16.09; found C 60.22, H 2.34, N 20.84. IR (ATR): ν = 3106, 3072

˜

(C-H Ar), 2993 (C-H), 2232 (CϵN), 1506, 1451, 1393, 1374 (C-H),

1310, 1281, 1233, 1156, 1122, 848, 756 cm^–1.

2-tert-Butylbenzothiazole-6,7-dicarbonitrile (3b): Prepared as de-

scribed for 2a with 19b (0.39 g, 1.27 mmol), sulfur (0.04 g,

1.27 mmol), Na₂S·xH₂O (0.15 g, 0.64 mmol) and EtOH (25 mL).

The reaction mixture was heated to reflux for 2 h. Purification by

silica gel column chromatography (hexane/ethyl acetate, 7:1) gave

the desired product as pale-yellow, needle-like crystals, yield 0.24 g

(ATR): ν = 3295 (N-H), 3070, 2957, 2864 (C-H), 1592, 1504, 1462,

˜

1407, 1363 (C-H), 1334, 1256, 1220, 1055, 1032, 1013, 949, 889,

810, 772, 741 cm^–1. UV/Vis (THF): λ_max(logε) = 712 (5.22), 677

(5.17), 648 (4.70), 614 (4.52), 389 (4.81), 364 nm (4.88). MS

(MALDI-TOF): m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺967.3; found

967.7. HRMS (ESI): m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺

967.2924; found 967.2917.

1

(78%); m.p. 128.5–130 °C. H NMR (300 MHz, CDCl₃): δ = 8.25

(d, J = 8.5 Hz, 1 H, H-C4), 7.83 (d, J = 8.5 Hz, 1 H, H-C5), 1.55

(s, 9 H, CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 188.5, 155.8,

140.3, 130.2, 127.3, 115.8, 114.3, 112.2, 110.0, 39.5, 30.7 (3ϫ

C) ppm. C₁₃H₁₁N₃S (241.31): calcd. C 64.7, H 4.59, N 17.41, S

2,3,9,10,16,17,23,24-Tetrakis[2Ј-tert-butyl[1Ј,3Ј]thiazolo]phthalo-

cyanine and Other Randomers (5b): Purified by column chromatog-

raphy (SiO₂, chloroform) twice to give a green crystalline com-

pound, yield 0.07 g (47%). ¹H NMR (600 MHz, CDCl₃): δ = 8.36–

7.41 (br. m, 8 H), 1.84–1.62 (m, 36 H) and –5.6 (br. s, 2 H) ppm.

¹³C NMR (151 MHz, CDCl₃): δ = 183.1–182.9, 154.0–153.7,

146.3–146.0, 136.7–136.4, 133.1, 131.2, 115.7–115.4, 39.2–39.0,

13.29; found C 64.43, H 4.65, N 17.39, S 13.27. IR (ATR): ν =

˜

3104, 3069 (C-H Ar), 3056, 2970, 2926, 2854 (C-H), 2926, 2231

(CϵN), 1505, 1468, 1451, 1398, 1365 (C-H), 1279, 1057, 995,

849 cm^–1.

General Procedure for the Synthesis of Metal-free Phthalocyan-

ines:^[14]To a stirred solution of n-hexanol (4 mL) under an Ar at-

mosphere, Li shot (0.026 g, 3.73 mmol, 6 equiv.) was added and the

reaction mixture was warmed to 100 °C and stirred. After Li shot

was consumed, the starting dicarbonitrile (0.62 mmol) was added

and the reaction mixture was warmed to reflux for 4 h. The reac-

31.3–31.1ppm. IR (ATR): ν = 3289 (N-H), 3070, 2959, 2927, 2865

˜

(C-H), 2562, 1744, 1510, 1462, 1403, 1364 (C-H), 1325, 1267, 1109,

1008, 883, 746 cm^–1. UV/Vis (THF): λ_max(logε) = 729 (5.17), 703

(5.09), 664 (4.55), 635 (4.47), 367 nm (4.66). MS (MALDI-TOF):

m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺967.3; found 967.4. HRMS

7066

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Thiazole-Annelated Phthalocyanines

(ESI): m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺967.2924; found

967.2911.

[7]

[8]

N. P. Farrell, A. J. Murray, J. R. Thornback, D. H. Dolphin,

B. R. James, Inorg. Chim. Acta 1978, 28, 144–146.

M. S. Rodriguez-Morgade, G. De la Torre, T. Torres, in: The

Porphyrin Handbook, vol. 15 (Eds.: K. M. Kadish, K. M.

Smith, R. Guilard), Academic Press, Amsterdam, 2003, p. 125–

160.

S. Angeloni, C. Ercolani, J. Porphyrins Phthalocyanines 2000,

4, 474–483.

a) R. S. Keri, M. R. Patil, S. A. Patil, S. Budagumpi, Eur. J.

Med. Chem. 2015, 89, 207–251; b) S. J. Kashyap, V. K. Garg,

P. K. Sharma, N. Kumar, R. Dudhe, J. K. Gupta, Med. Chem.

Res. 2012, 21, 2123–2132.

3,4,10,11,17,18,24,25-Tetrakis[2Ј-tert-butyl[1Ј,3Ј]thiazolo]phthalo-

cyanine and Other Randomers (6b): Purified by column chromatog-

raphy (SiO₂, chloroform/toluene/pyridine, 5:5:1) to give a green

crystalline compound, yield 0.051 g (34%). ¹H NMR (600 MHz,

CDCl₃): δ = 1.38 (br. s) ppm. Due to a very high tendency toward

aggregation, the position of pyrrole protons and aromatic protons

could not be determined at high concentrations used in NMR spec-

troscopy. ¹³C NMR (151 MHz, CDCl₃): δ = 183.5, 154.6, 125.8,

[9]

[10]

38.5–37.8, 31.1–30.8 ppm. IR (ATR): ν = 3291 (N-H), 3064, 2959,

˜

[11]

a) A. Nas, G. Dilber, M. Durmus¸, H. Kantekin, Spectrochim.

2923, 2852 (C-H), 2564, 1728, 1505, 1365 (C-H), 1345, 1323, 1258,

1086, 1056, 1030, 878, 821, 743, 686 cm^–1. UV/Vis (THF): λ_max

(logε) = 719 (5.17), 683 (5.20), 653 (4.90), 621 (4.74), 390 nm (4.89).

MS (MALDI-TOF): m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺967.3;

found 967.3. HRMS (ESI): m/z calcd. for C₅₂H₄₆N₁₂S₄[M + H]⁺

967.2924; found 967.2901.

˙

Acta Part A 2015, 135, 55–62; b) A. Aktas¸, M. Durmus¸, I.

Degirmencioglu, Polyhedron 2012, 48, 80–91.

˘

[12]

[13]

[14]

[15]

P. Hrobárik, I. Sigmundová, P. Zahradník, P. Kasák, V. Arion,

E. Franz, K. Clays, J. Phys. Chem. C 2010, 114, 22289–22302.

U. M. Weigel, R. Herges, J. Chem. Inf. Comput. Sci. 1992, 32,

723–731.

A. Muranaka, M. Yonehara, M. Uchiyama, J. Am. Chem. Soc.

2010, 132, 7844–7845.

Supporting Information (see footnote on the first page of this arti-

cle): Copies of IR spectra, ¹H and ¹³C NMR spectra, additional

experimental and calculated absorption spectra, cyclic voltammog-

rams, MALDI-TOF and HRMS spectra.

F. Baumann, B. Bienert, G. Rosch, H. Vollman, W. Wolf, An-

gew. Chem. 1956, 68, 133–168.

[16]

[17]

R. M. Christie, B. G. Freer, Dyes Pigm. 1994, 24, 259–266.

R. Seoudi, G. S. El-Bahy, Z. A. El Sayed, J. Mol. Struct. 2005,

753, 119–126.

N. Kobayashi, H. Ogata, N. Nonaka, E. A. Luk’yanets, Chem.

Eur. J. 2003, 9, 5123–5134.

T. Stoyanova, in: Near-Infrared Applications in Biotechnology

(Ed.: R. Raghavachari), Marcel Dekker Inc., New York, 2000,

p. 77.

W. Freyer, C. N. Neacsu, M. B. Raschke, J. Lumin. 2008, 128,

661–672.

N. Kobayashi, T. Furuyama, K. Satoh, J. Am. Chem. Soc.

2011, 133, 19642–19645.

H. Engelkamp, R. J. M. Nolte, J. Porphyrins Phthalocyanines

2000, 4, 454–459.

M. T. M. Choi, P. P. S. Li, D. K. P. Ng, Tetrahedron 2000, 56,

3881–3887.

Acknowledgments

[18]

[19]

This work has been supported by the Slovak Research and Devel-

opment Agency (grant numbers APVV 0424-10, APVV 0622-12

and APVV-14-0716) and by the Comenius University (grant num-

bers UK/548/2012 and UK/481/2013). This research is also the re-

sult of the project implementation: Comenius University in Bratis-

lava Science Park supported by the Research and Development Op-

erational Programme funded by the ERDF (grant number ITMS

26240220086). Part of the calculations was performed in the Com-

puting Centre of the Slovak Academy of Sciences using the super-

computing infrastructure acquired in projects ITMS 26230120002

and 26210120002 (Slovak infrastructure for high-performance

computing) supported by the Research & Development Opera-

tional Programme funded by the ERDF. The authors thank Assoc.

[20]

[21]

[22]

[23]

[24]

L. T. Bergendahl, M. J. Paterson, Comput. Theor. Chem. 2014,

1040–1041, 274–286.

Prof. RNDr. Milan Drábik, CSc. for performing the Simultaneous [25]

TGA-DTA analyses and Mgr. Juraj Filo, PhD. for accomplishing

the NMR measurements.

R. Li, X. Zhang, P. Zhu, D. K. P. Ng, N. Kobayashi, J. Jiang,

Inorg. Chem. 2006, 45, 2327–2334.

S. Z. Topal, Ü. Is¸ci, U. Kumru, D. Atilla, A. G. Gürek, C. Hi-

˙

[26]

rel, M. Durmus¸, J.-B. Tommasino, D. Luneau, S. Berber, F.

Dumoulin, V. Ahsen, Dalton Trans. 2014, 43, 6897–6908.

V. D. Parker, J. Am. Chem. Soc. 1976, 98, 98–103.

L. Kaestner, M. Cesson, K. Kassab, T. Christensen, P. D. Ed-

minson, M. J. Cook, I. Chambrier, G. Jori, Photochem. Pho-

tobiol. Sci. 2003, 2, 660–667.

M. Kostka, P. Zimcik, M. Miletin, P. Klemera, K. Kopecky, Z.

Musil, J. Photochem. Photobiol. A 2006, 178, 16–25.

N. G. Connelly, W. E. Geiger, Chem. Rev. 1996, 96, 877–910.

TURBOMOLE V6.6 2014, a development of University of

Karlsruhe and Forschungszentrum Karlsruhe GmbH, Ger-

many, 1989–2007, TURBOMOLE GmbH, since 2007; avail-

able from http://ww w .turbomole.com.

O. Treutler, R. Ahlrichs, J. Chem. Phys. 1995, 102, 346–354.

a) P. A. M. Dirac, Proc. R. Soc. London Ser. A 1929, 123, 714–

733; b) J. C. Slater, Phys. Rev. 1951, 81, 385–390; c) J. P. Perdew,

Y. Wang, Phys. Rev. B 1992, 45, 13244–13249; d) J. P. Perdew,

K. Burke, M. Ernzerhof, Phys. Rev. Lett. 1996, 77, 3865–3868;

e) J. P. Perdew, M. Ernzerhof, K. Burke, J. Chem. Phys. 1996,

105, 9982–9985.

a) F. Weigend, M. Häser, H. Patzelt, R. Ahlrichs, Chem. Phys.

Lett. 1998, 294, 143–152; b) F. Weigend, R. Ahlrichs, Phys.

Chem. Chem. Phys. 2005, 7, 3297–3305.

[1] Nonlinear Optics of Organic Molecules and Polymers (Eds.:

H. S. Nalwa, S. Miyata), CRC Press, Boca Raton, FL, 1997.

[2] G. De la Torre, P. Vazquez, F. Agullo-Lopez, T. Torres, J. Ma-

[27]

[28]

ter. Chem. 1998, 8, 1671–1683.

[3] G. De la Torre, T. Torres, F. Agullo-Lopez, Adv. Mater. 1997,

[29]

9, 265–269.

[4] a) E. V. Kudrik, G. P. Shaposhnikov, A. E. Balakirev, Russ. J.

[30]

[31]

Gen. Chem. 1999, 69, 1321–1324; b) A. E. Balakirev, E. V. Kud-

rik, G. P. Shaposhnikov, Russ. J. Gen. Chem. 2002, 72, 1616–

1619; c) V. E. Maizlish, G. P. Shaposhnikov, O. V. Balakireva,

M. A. Zharnikova, I. G. Abramov, S. A. Ivanovskii, A. V.

Smirnov, Russ. J. Gen. Chem. 2004, 74, 787–790; d) N. E. Gal-

anin, E. V. Kudrik, G. P. Shaposhnikov, Russ. J. Org. Chem.

2008, 44, 225–230; e) C. Pardo, M. Yuste, J. Elguero, J. Por-

phyrins Phthalocyanines 2000, 4, 505–509; f) W. J. Youngblood,

J. Org. Chem. 2006, 71, 3345–3356; g) K. Padmaja, J. Young-

blood, L. Wei, D. F. Bocian, J. S. Lindsey, Inorg. Chem. 2006,

45, 5479–492; h) S. Z. Topal, E. Önal, A. G. Gürek, C. Hirel,

Dalton Trans. 2013, 42, 11528–11536.

[32]

[33]

[34]

[5] H. Uchida, P. Y. Reddy, S. Nakamura, T. Toru, J. Org. Chem.

2003, 68, 8736–8738.

[6] N. Safari, P. R. Jamaat, S. A. Shirvan, S. Shoghpour, A. Ebadi,

[35]

M. Darvishi, A. Shaabani, J. Porphyrins Phthalocyanines 2005,

9, 256–261.

U. C. Singh, P. A. Kollman, J. Comput. Chem. 1984, 5, 129–

145.

Eur. J. Org. Chem. 2015, 7053–7068

www.eurjoc.org

7067

A. Fülöpová et al.

A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.

FULL PAPER

[36] a) R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 1996, 256,

454–464; b) G. Scalmani, M. J. Frisch, B. Mennucci, J. Tomasi,

R. Cammi, V. Barone, J. Chem. Phys. 2006, 124, 094107: 1–15.

[37] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,

M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.

Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,

H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-

nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-

gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,

T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M.

Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-

erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,

J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.

Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Ad-

amo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,

A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Mar-

tin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,

J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B.

Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09,

revision A.02, Gaussian, Inc., Wallingford CT, 2009.

[40]

[41]

a) R. Ditchfield, W. J. Hehre, J. A. Pople, J. Chem. Phys. 1971,

54, 724–728; b) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem.

Phys. 1972, 56, 2257–2261; c) P. C. Hariharan, J. A. Pople,

Theor. Chem. Acc. 1973, 28, 213–222; d) P. C. Hariharan, J. A.

Pople, Mol. Phys. 1974, 27, 209–214; e) M. S. Gordon, Chem.

Phys. Lett. 1980, 76, 163–168; f) M. M. Francl, W. J. Pietro,

W. J. Hehre, J. S. Binkley, D. J. DeFrees, J. A. Pople, M. S. Gor-

don, J. Chem. Phys. 1982, 77, 3654–3665; g) R. C. Binning Jr.,

L. A. Curtiss, J. Comput. Chem. 1990, 11, 1206–1216; h) J.-P.

Blaudeau, M. P. McGrath, L. A. Curtiss, L. Radom, J. Chem.

Phys. 1997, 107, 5016–5021; i) T. Clark, J. Chandrasekhar,

G. W. Spitznagel, P. v. R. Schleyer, J. Comput. Chem. 1983, 4,

294–301.

[42]

a) S. Miertusˇ, E. Scrocco, J. Tomasi, Chem. Phys. 1981, 55,

117–129; b) M. Cossi, V. Barone, J. Chem. Phys. 2000, 112,

2427–2435.

[43] M. Wojdyr, J. Appl. Crystallogr. 2010, 43, 1126–1128.

[44] A. E. Balakirev, V. E. Maizlish, G. P. Shaposhnikov, R. P. Smir-

nov, Russ. J. Gen. Chem. 2000, 70, 623–626.

Received: June 12, 2015

[38] Y. Zhao, D. G. Truhlar, Theor. Chem. Acc. 2008, 120, 215–241.

[39] a) A. Schaefer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97,

2571–2577; b) A. Schaefer, C. Huber, R. Ahlrichs, J. Chem.

Phys. 1994, 100, 5829–5835.

Published Online: October 1, 2015

7068

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7053–7068

Article Doi

Synthesis and Photophysical, Electrochemical and Theoretical Study of Thiazole-Annelated Phthalocyanines

DOI: 10.1002/ejoc.201500785

Source and publish data:

Authors:

Article abstract of DOI:10.1002/ejoc.201500785

Full text of DOI:10.1002/ejoc.201500785

Products guided by the article

R&D Labs maybe for 329308-83-0

Relevant to this article

Hot Product