SYNTHESIS AND PROPERTIES OF SULFO AND ALKYLSULFAMOYL SUBSTITUTED PHTHALOCYANINES AND THEIR COPPER (II) COMPLEXES BEARING 1-BENZOTRIAZOLYL AND 4-CYCLO-HEXYLPHENOXY GROUPS Текст научной статьи по специальности «Химические науки»

UDC 532.783+547

S. A. Znoiko1, N. V. Bumbina2, O. B. Akopova2, G. R. Berezina1, A. I. Smirnova2, N. V. Usol'tseva2, V. E. Maizlish1, G. P. Shaposhnikov1

SYNTHESIS AND PROPERTIES OF SULFO AND ALKYLSULFAMOYL SUBSTITUTED PHTHALOCYANINES AND THEIR COPPER (II) COMPLEXES BEARING 1-BENZOTRIAZOLYL AND 4-CYCLOHEXYLPHENOXY GROUPS

'Research Institute of Macroheterocydic Compounds, Ivanovo State University of Chemistry and Technology, 7 Sheremetievsky Pr., Ivanovo, 153000, Russia. E-mail: [email protected] 2Nanomaterials Research Institute, Ivanovo State University, 39 Ermak St., Ivanovo, 153025, Russia. E-mail: [email protected]

New sulfo and alkylsulfamoyl substituted 2,9,16,23-tetrakis(1-benzotriazolyl)3,10,17,24-tetrakis(4-cyclohexylphenoxy)phthalocyanines and their Cu(II) complexes were synthesized. Their physicochemical properties such as electronic absorption, solubility in organic solvents, thermostability and mesomorphism were investigated. It was established that introduction of sulfo group into cyclohexylphenoxy fragment of the studied phthalocyanines causes bathochromic shift of long wave band s in both DMF and concentrated sulfuric acid solutions. In contrast, introduction of octadecylsulfamoyl substituentsdoes not influence the position of Q band in DMF, but shifts this band hypsochromically. The performed synthesis revealed that introduction of bulky fragments into ortho-position with respect to the oxygen atom of aryloxy group excludes manifestation of liquid crystalline properties. While substitution by the same substituent in para-position leads to formation of mesophase. This fact can be connected with the sterical hindrance of liquid crystalline molecular packing. Thus, it was established that the presence of donor and acceptor fragments in mix-substituted phthalocyanines is important but not determining factor for their mesophase formation. The forecast data on the absence of mesomorphism of new phthalocyanine derivatives with sulfo and alkylsulfamoyl groups are in a good agreement with the experimental data, which is the evidence of the applicability of the method used to identify mesogen / non-mesogen structures for this class of compounds.

Key words: phthalocyanines, synthesis, mesomorphism, solubility, thermostability, mesomorphism prognosis.

DOI: 10.18083/Appl.2017.1.56

С. А. Знойно1', Н. В. Бумбина2, О. Б. Акопова2, Г. Р. Березина1, А. И. Смирнова2, Н. В. Усольцева2, В. Е. Майзлиш1, Г. П. Шапошников1

СИНТЕЗ И СВОЙСТВА СУЛЬФОКИСЛОТ И АЛКИЛСУЛЬФАМОИЛ-ЗАМЕЩЕННЫХ ФТАЛОЦИАНИНОВ И ИХ КОМПЛЕКСОВ С МЕДЬЮ, СОДЕРЖАЩИХ 1-БЕНЗОТРИАЗОЛЬНЫЕ И 4-ЦИКЛОГЕКСИЛФЕНОКСИ ГРУППЫ

:НИИ Макрогетероциклических соединений, Ивановский государственный химико-технологический университет, Шереметевский пр., 7, 153000 Иваново, Россия. E-mail: [email protected] 2НИИ Наноматериалов, Ивановский государственный университет, ул. Ермака, 39, 153025 Иваново, Россия. E-mail: [email protected]

Взаимодействием 2,9,16,23-тетра(1-бензотриазолил)-3,10,17,24-тетра(4-циклогексилфенокси) фталоцианина и его комплекса с медью со смесью тионилхлорида и хлорсульфоновой кислоты получены соответствующие сульфохлориды. Гидролизом сульфохлоридов синтезированы новые сульфокислоты

© Знойко С. А., Бумбина Н. В., Акопова О. Б., Березина Г. Р., Смирнова А. И., Усольцева Н. В., Майзлиш В. Е., Шапошников Г. П., 2017

бензотриазолилзамещенных фталоцианинов. Реакцией сульфохлорида 2,9,16,23-тетра(1-бензо-триазолил)-3,10,17,24-тетра(4-циклогексилфенокси)фталоцианина меди с октадециламином в ацетоне получено соответствующее октадецил октадецилсульфамоилпроизводное. Изучены спектральные свойства целевых соединений, их термическая устойчивость, растворимость в органических растворителях и мезоморфизм. Установлено, что при введении сульфогрупп в циклогексилфенокси фрагмент исследуемых фталоцианинов в спектрах поглощения наблюдается батохромный сдвиг длинноволновых полос как в ДМФА, так и в концентрированной серной кислоте. Введение октадецилсульфамоильных заместителей не оказывает влияние на положение Q полосы в ДМФА, но приводит к гипсохромному сдвигу этой полосы в концентрированной серной кислоте. Показано, что введение объемных сульфо- и алкилсульфамоил фрагментов в орто-положение по отношению к атому кислорода арилокси группы производных фталоцианина, исключает проявление мезоморфных свойств, в то время как аналогичное замещение в пара-положении приводит к формированию мезофазы. Данный факт объяснен стерическими влияниями на возможность межмолекулярного взаимодействия данных соединений, оптимального для формирования мезофаз. Проведенные исследования впервые позволили установить, что наличие донорных и акцепторных групп в смешанно-замещенных фталоцианинах является важным, но не решающим фактором в проявлении ими мезоморфных свойств. Полученные по прогнозу данные об отсутствии мезофаз у новых производных фталоцианина с сульфо- и алкилсульфамоил группами находятся в хорошем согласии с экспериментом, что свидетельствует о применимости использованного метода к выявлению мезоген /немезогенных структур у подобного класса соединений.

Ключевые слова: фталоцианины, синтез, мезоморфизм, растворимость, термогравиметрия, прогноз мезоморфизма.

Introduction

Study of the relationship between structure and properties of phthalocyanine derivatives and their mesomorphism is the fundamental task of physical chemistry of condensed matter.

At present time, experimental data on mesomorphism of bifunctionally substituted phthalocyanines are limited. The expansion of the number of such compounds will help to come closer to solve the problem of the dependence of liquid crystal properties on the structure of organic compound [1].

In this work, we continue investigations concerning synthesis of sulfo- and alkylsulfamoyl derivatives of aryloxy-substituted phthalocyanines [2-3]. We have previously shown that the presence of donor and acceptor substituents imparts the ability for non-mesogenic compounds to show thermotropic mesomorphism [4-7]. While the introduction of sulfo or alkylsulfamoyl fragments into para-position with

respect to the oxygen atom of aryloxy group of mix-substituted phthalocyanines does not affect the ability of these compounds to exhibit mesomorphism. Such substitution shifts the mesophase existence region to higher temperatures [3]. We have studied compounds with 1-methyl-1-phenylethyl substituents in phenyloxy groups, these are the fragments in which sulfo and sulfonamide moieties are located [3]. In contrast to the previously investigated compounds, the new target phthalocyanines 1-2, due to presence of cyclohexyl group in para-position of phenoxy groups, contain sulfo and alkylsulfamoyl groups in ortho-positions with respect to oxygen atom of phenoxy fragment (Fig. 1). Such change should significantly influence physicochemical and mesomorphic properties.

The aim of this work is the synthesis and investigation of physicochemical properties of sulfonic acids 1 and alkylsulfamoyl derivatives 2 of the mix-substituted phthalocyanines containing 1-benzotriazolyl and 4-cyclohexylphenoxy fragments.

so3h

n

ho3s.

H37C18HNO2;S N

O-CkK)

fx

so3h

.1—m—n'j^t'

i n .^vs

n ho3s

1a,b

h37c18hno2s.

so2nhc18h37

so2nhc18h37

M = HH, Cu

2a,b

Fig. 1. Structural formulas of the studied compounds

Experimental

UV-Vis spectra of solutions of the synthesized phthalocyanines in DMF and chloroform were obtained on HITACHI U-2001 spectrophotometer at a room temperature on the spectral range of 325900 nm. IR spectra were recorded on Avatar 360 FT-IR ESP spectrophotometer at a room temperature. NMR spectra of 1a, 2b in DMSO[D6] and CDCl3 with TMS as internal standard were carried out on «Bruker DRX-500». Elemental analysis was performed on Flash EATM 1112 instrument. Spectral studies and elemental analysis were carried out on the equipment of the Centre for Collective Use (Ivanovo, ISUCT).

Study of solubility of 2,9,16,23 -tetrakis-(1 -benzotriazolyl)-3,9,17,24-tetrakis(4-cyclohexylphe-noxy)phthalocyanines and its copper complexes as well as their sulfonic acids was carried out according to the known procedure [8] at 298 K by isothermal saturation with spectrophotometric control of concentration. The systematic error in the solubility's value due to an error in the determination of the molar extinction coefficient was 5 %. The absorption bands with maxima at 684 (4a), 685 (4b), 683 (1a), 685 (1b) in DMF and 688 (4a), 692 (4b) in chloroform were selected as analytical bands.

Mesomorphism of sulfo- (1a, b) and octadecylsulfamoyl- (2b) phthalocyanine derivatives

was studied by optical polarizing microscopy (polarizing microscope «Leitz Laborlux 12 Pol» equipped with «Mettler FP 82» heating stage, heating/cooling rate 10 °C/min). Lyotropic mesomorphism of binary systems of the studied compounds with organic solvents (DMF, DMSO, toluene, CHCls) and aqueous solutions was tested by contact preparation technique on the equipment of the Nanomaterials Research Institute (Ivanovo State University).

Prediction of columnar mesomorphism for compounds 1-2 was performed using the original program CMP ChemCard [9]. The program gives the possibility to calculate the molecular parameters (MP) of individual molecule and to predict whether the compound can be potential discotic mesogen. Among the advantages of this method is the simplicity of use, low cost of machine time and sufficiently high degree of reliability of the prediction (70-90 %). Prior the prediction, geometry optimization of molecular structures was performed by HyperChem software package (method MM+).

Synthesis of 2,9,16,23-tetrakis(1-benzotriazo-lyl)-3,10,17,24-tetrakis [4-cyclohexylphenoxy] phtha-locyanine and its copper complex (4a,b) was performed according to the known procedure [10].

Synthesis of sulfonic acids of 2,9,16,23-tetrakis(1-benzotriazolyl)-3,10,17,24-tetrakis[4-cyclohexylphe-noxy] phthalocyanine and its copper complex (1a,b)

0.1 mmol of compounds 4a,b reacted with a mixture of 2 ml (18 mmol) of chlorosulfonic acid and 2 ml (18 mmol) of thionyl chloride at room temperature and stirred during 1 hour (in the case of metal-free phthalocyanine) or 2 hours (in the case of the corresponding copper complex). After stirring, the reaction mixture was poured onto ice and treated with sodium chloride. The precipitate was collected on a sinter and dried in a desiccator over sulfuric acid for 3 days. The resultant sulfonic chloride was extracted with acetone, the solvent was evaporated under reduced pressure. The crude product was boiled in water until it was completely dissolved. The resultant sulfonic acid was extracted with DMF, the solution was filtered through a paper filter and the solvent was evaporated. The obtained products were dark green solids, soluble in water, ammonia and aqueous alkaline solutions.

The final purification was performed by column chromatography on silica gel (M 60) using DMF as the eluent. The desired products were dried in the air at 80-90 °C.

2,9,16,23-Tetrakis(1-benzotriazolyl)-3,10,17,24-tetra-kis(2-sulfo-4-cyclohexylphenoxy)phthalocyanine (1a) was synthesized according to the main procedure from 174 mg of compound 4а. (Yield 191 mg, 92 %). Found, %: С 62.45, Н 4.33, N 14.01, S 6.41; C112H78N20O16S4. Requires: С 61.94, Н 4.70, N 14.29, S 6.54; Vmax (KBr)/cm-1: 3418 (-OH), 2925, 2850 (CH2, CH3), 1358 (Ar-O-Ar), 1330 (S=O asymm), 1091 (C-S), 1047 (N=N), 1024 №Pc), 747 (C-N). 5h ([D6]DMSO, numeration of protons is presented in Scheme 3): 9.22 (s, 4^ SO3H); 8.70 (t, 4^ m); 8.38. (s, 4^ m); 8.29 (s, 4^ TO); 8.20-8.10 (m, 4^ TO); 7.83-7.90 (m, 4^ m); 7.62 (s, 4^ TO); 7.48-7.53 (m, 4^ TO); 7.28 (t, 4^ TO); 2.18 (m, 4^ m0); 1.66; 1.54-1.51 (m, 10^ m1,12).

2,9,16,23-Tetrakis(1-benzotriazolyl)-3,10,17,24-tetra-kis(2-sulfo-4-сyclohexylphenoxy)phthalocyanine copper complex (1b) was obtained according to the main procedure from 188 mg of compound 4b. (Yield 178 mg, 80 %). Found, %: C 59.98, N 13.26, H 4.30, S 6.00; C104HmCuN20O16S4. Requires: C 60.59, N 13.59, H 4.11, S 6.22; Vmax (KBr)/cm-1: 3386 (OH), 2924, 2849, 2781 (CH2, CH3), 1395, 1349 (S=O asymm), 1206 (Ar-O-Ar), 1175 (S=O symm), 1088 (C-S), 1058 (N=N), 745 C-N.

Synthesis of 2,9,16,23-tetrakis(1-benzotriazolyl) 3, 10, 17,24-tetrakis-(2-octadecylsulfamoyl-4-cyclohexyl-phenoxy)phthalocyanine copper complex (2b)

Compound 4b (172 mg, 0.1 mmol) reacted with a mixture of chlorosulfonic acid 2 ml (18 mmol) and thionyl chloride 2 ml (18 mmol) at room temperature for 2 hours. After stirring, the reaction mixture was poured onto ice and treated with sodium chloride. The precipitate was collected on a sinter and dried in a desiccator over sulfuric acid for 3 days. The target sulfochloride was extracted with acetone. An 8-fold molar excess of octadecylamine (0.22 g, 0.8 mmol) was added to the obtained acetone solution and the mixture was heated at 60 °C for 1-1.5 hours. The process was controlled by the completeness of the dissolution of the reaction mixture in chloroform. After the reaction was finished, the acetone was distilled off. The desired product was extracted from the reaction mixture with chloroform. Final purification was performed by column chromato-graphy on silica gel (M 60) using chloroform as eluent. The resulting product was dark green solid, partially soluble in DMF, highly soluble in benzene, acetone and chloroform. (Yield 233 mg, 77 %). Found, %: C 68.35, N 10.55, H 8.38, S 4.07; C176H232CuN24O12S4. Requires: C 68.91, N 10.96, H 7.62, S 4.18. Vmax (KBr)/cm-1: 2920, 2851 (-CH2, -CH3), 1617 (-NHsec, def.), 1533 (NHsec. val), 1388 (S=O asymm), 1242 (Ar-O-Ar), 1088 (C-S), 1050 (N=N), 746 (C-N); 5h (CDCl3, numeration of protons is presented in Scheme 3): 8.71 (t, 4^ m); 8.23 (t, 4^ H3); 8.12 (m, 4^ H2); 8.03-8.05 (m, 4^ H6); 7.87-7.77 (m, 4^ H4); 7.49 (t, 4^ H5); 7.26 (H8); 6.90 (m, 4^ H7); 5.40 (s, 4^ NH); 3.15 (m, 4^ H9); 2.98-2.91 (H10); 1.36 (H11,12); 1.89, 1.79, 1.44 (-CH2 in NHC18H37); 0.91 (s, 12^ -CH3).

Results and discussions

Synthesis

Synthesis of the target compounds was carried out starting from the corresponding bifunctionally substituted phthalocyanines 4a,b. These were obtained according to the known procedure [10] using "nitrile" method, consisting in heating the phthalonitrile 3 with copper acetate or anhydrous potassium carbonate (Scheme 1).

Then phthalocyanine derivatives 4a,b were separated from the reaction mixture and treated with a mixture of thionyl chloride and chlorosulfonic acid according to the method described in [2-3] (Scheme 2).

"oa:

i, a

M = HH (a), Cu (b) i: Cu(OAc)2*2H2O, 210 oC ii: K2CO3, (NH2)2CO, 210 oC

Scheme 1

4a,b

M = HH (a), Cu (b) i: HSO3Cl + SOCl2, T = 25 oC,1hour - 4a, 2hours - 4b 5a,b

ClO2S

Scheme 2

3

The interaction time was determined by the nature of the coordination center: in the case of copper complex it was 2 hours, for metal-free phthalocyanine - 1 hour. The resulting sulfonyl chlorides 5a,b were isolated by pouring reaction mixture onto ice. The formed precipitate was filtered off and dried thoroughly.

For the synthesis of the corresponding sulfonic acids 1a,b the sulfonyl chlorides were extracted with acetone. The obtained solution was filtered and the

acetone was distilled off. After that, the crude product was refluxed in water until its complete dissolution, and then the water was removed (Scheme 3).

For the synthesis of the octadecylsulfamoyl derivatives an 8-fold molar excess of octadecylamine was added into the acetone extract. The resulting solution was refluxed until the test showed complete dissolution of the reaction mixture in chloroform (Scheme 3). The attempt to obtain metal-free alkyl-

sulfamoyl phthalocyanine 4a by this method failed.

Identification of the synthesized compounds was performed by elemental analysis, :H NMR-, IR- and electron spectroscopy. In the :H NMR spectrum of the sulfonic acid 1a the appearance of four protons of sulfo groups at 9.07 ppm as well as a new signal at 8.38 ppm, which was absent in the spectrum of the original phthalocyanine 4a, were detected in the weak field region. The signal at 8.04 ppm, which was observed in the spectrum of the "parent"

phthalocyanine 4a [10] and corresponded to the proton in the 2-position, was absent. This fact confirms the introduction of sulfo group into aryl fragment exactly in the ortho-position to the oxygen bridge. A similar change in the :H NMR spectrum was observed in the case of the previously studied 2,9,16,23-tetrakis(1-benzotriazolyl)-3,10,17,24-tetrakis(1,6-disulfo-2-na-phtoxy)phthalocyanine [2], which also contains sulfo group in the ortho-position to the oxygen bridge in the phenyloxy fragment.

2b

or2

7 8 9 10

Scheme 3

In the 1H NMR spectrum of alkylsulfamoyl derivative 2b the intense signals of methylene groups belonging to octadecyl substituents were observed in strong field region at 3.2-1.2 ppm. The signal of the protons of methyl groups of alkyl chains were detected at 0.92 ppm. In the strong field region (at 2.903.15 ppm) there were signals of methylene groups of cyclohexyl substituents, which were previously found in the spectra of the starting compounds [10]. The signal of protons of the secondary amino groups of the octadecylsulfamoyl substituents was detected in lower field (at 5.40 ppm).

Introduction of sulfo groups into the molecule of 2,9,16,23-tetrakis(1-benzotriazolyl)-3,10,17,24-tetra-kis(4-cyclohexylphenoxy)phthalocyanine 1a or its copper complex 1b causes the appearance in the IR spectrum of symmetric (at 1175 cm-1) and asymmetric (at 1330-1349 cm-1) vibrations characteristic of S=O bonds and stretching vibrations of C-S bonds (at 1088-1091 cm-1). In the IR spectrum of compound 1a the band specific to metal-free phthalocyanine (usually

Fig. 2. Electronic absorption spectra in aqueous NH4OH (5 %) (C = 0.6-10-5 mol/l): 1 - 1a, 2 - 1b

Table 1. UV-Vis spectroscopy data for c<

observed at 1005 cm-1) was shifted to the region of higher frequency (1024 cm-1). Introduction of alkyl-sulfamoyl fragments was accompanied in the IR spectrum by the appearance of stretching bands (1533 cm-1) and deformation oscillations (1617 cm-1) of the secondary amino groups.

Since sulfo groups of sulfonic acids 1a,b were introduced into sterically closed position of phenyloxy substituent and shielded from interaction with water molecules by hydrophobic cyclohexyl fragments, both compounds were insoluble in the water, but soluble in aqueous-alkaline solutions and DMF. Octa-decylsulfamoyl derivative 2b is highly soluble in acetone and chloroform, but low soluble in DMF.

Electronic absorption spectra

By analyzing spectra of sulfonic acids 1a,b in 5 % aqueous ammonium hydroxide solution, it was found that the presence of copper atom in the coordination center of phthalocyanine molecule reduces its tendency to association (Fig. 1).

Fig. 3. Electronic absorption spectra in DMF (C = 0.85-10-5 mol/l): 1 - 1a, 2 - 1b

Is 1a,b, 2b and 4a,b in different solvents

№ R M UV-Vis spectra, Xmax, nm

NH4OH (5%) DMF CHCls H2SO4

1a HO3S HH 664 694 - 803

1b Cu 642, 697 692 - 769, 791

2b SO2NHC18H37 Cu - 684 684 767, 790

4a --^ ^ [10] HH - 684 689 795, 836

4b Cu - 685 675, 710 802

Considering the character of electronic absorption spectra in DMF, one can conclude that the sulfonic acids 1a,b were unassociated (Fig. 3). In the spectrum of alkylsulfamoyl copper phthalocyanine 2b in chloroform, a broadening of absorption bands located in the visible region, and disobedience to the Lambert-Bouguer-Beer law were observed, which indicate the association processes (Fig. 4). According to the nature of its absorption spectrum, compound 2b in DMF solution was in unassociated form (Fig. 4), but due to poor solubility of this phthalocyanine in DMF it was not possible to determine its extinction coefficient.

The change of organic solvent for the concentrated sulfuric acid, as expected, causes a bathochromic shift of the absorption bands in the electronic absorption spectra, but this shift is smaller in comparison with "parent" compounds 4a,b (Table 1 [10]). As in the case of 4a,b, the spectral curves are diffuse.

2,01,5 Q 1,00,5-

0,0

400

500

600 X, нм 700

800

900

Fig. 4. Electronic absorption spectra for compound 2b in organic solvents (C = 1.0 ■ 10-5 mol/l): 1 - DMF, 2 - CHCl3

0,7 0,60,5 Q 0,4

0,3 0,2 0,1

0,0

400

500

600

700

800

900

Fig. 5. Electronic absorption spectra in H2SO4: 1 - 4a, 2 - 1a, 3 - 1b

1-■-1

800 X, нм 900

Fig. 6. Electronic absorption spectra in H2SO4: 1 - 4b, 2 - 2b

X, нм

Comparing the "parent" compound 4a with its sulfonic acid 1a a hypsochromic shift of Q-band at 33 nm was detected. Introduction of copper atom into the molecule 1a causes a hypsochromic shift of Q-band for further 12 nm (Fig. 5). The transition from copper phthalocyanine 4b to its octadecylsulfamoyl derivative 2b is also accompanied by a hypsochromic shift of Q-band at 14 nm (Fig. 6).

Solubility study

Solubility of macroheterocyclic compounds has its own specificity, which is generally determined by two factors: the strength of the crystal lattice of these compounds and solvation by solvent molecules. The

complexity and diversity of phthalocyanine structures define the specific behavior of these compounds in chemical reactions and physicochemical processes that take place in solutions [11].

It is known that the unsubstituted phthalocyanine and its complexes at normal conditions are unsoluble in either water or in organic solvents [12]. The modification of the phthalocyanine molecule by introduction of functional substituents of different nature can impart solubility in organic solvents by introducing the centers of specific solvation and loosening the molecular lattice. Changing the structure of the molecule and its effective volume should be accompanied by a change in the crystal lattice

strength due to intermolecular interactions in crystal and, as a consequence, different inclinations of compound to undergo transition into solution. The solubility study of bifunctionally substituted phthalocyanines in various solvents is of interest. Therefore, the solubility of compounds 1a,b and 4a,b in DMF and chloroform has been investigated.

The presence of bulky substituents affects the strength of the crystal lattice due to its loosening, thereby makes compounds soluble in organic solvents. Solubility of 2,9,16,23-tetrakis(1-benzotriazolyl)-3, 10,17,24-tetrakis(4-cyclohexylphenoxy)phthalocya-nine 4a and its copper complex 4b as well as their sulfonic acids 1a,b in DMF at 298 K is 10-2 mol/l (Table. 2).

The experimental data on solubility of compounds 4a,b in DMF and chloroform at 298 K show that solubility in chloroform is lower than in DMF. This fact can indirectly indicate a decrease in the strength of the molecular lattice, as well as an

Thermogravimetry

The thermal oxidative degradation process of metal-free phthalocyanines 1a and 4a was studied. The results are given in Table 3.

The thermal decomposition process of compounds 1a and 4a consists of two stages. The first one occurs in the temperature range 280-360 °C. According to the weight loss value observed on TG curves (27.91 % for 4a and 23.35 % for 1a), the decomposition occurs with the participation of benzotriazolyl substituents, as it was found previously for other phthalocyanines combining on the periphery benzotriazolyl and oxyaryl groups [14]. For example for compounds 4a and 1a, heated up to 290 °C, in the IR spectra there was no band corresponding to the stretching vibrations of N=N bond of benzotriazolyl

increased affinity of large organic molecules to DMF. This difference is due to the nature and the solvating ability of the used solvents. Thus, chloroform is weakly polar, proton-donor non-coordinating solvent, it is practically not associated with proton acceptors and gives a strong hydrogen bond. AN = 23.1, s = 4.80. On the other hand, DMF is dipolar solvent with a strong electron-donating function (DN = 26). Considering the nature in solubility changes of compounds 4a and 4b in chloroform, we may conclude that despite the presence of specific solvation centers, they are sterically shielded from chloroform molecules. Therefore the solubility of compounds 4a,b is slightly different from solubility of similar structure copper phthalocyanine containing unsubstituted phenoxy groups [13]. Reduction of solubility in DMF in the case of sulfonic acids 1a,b in comparison with their "parent" compounds 4a and 4b was also detected.

fragment (1040-1050 cm-1). At the same time, it was found that compound 4a retains solubility in chloroform and compound 1a - in aqueous alkaline solutions. That is, the mass loss at this stage can be caused by the removal of benzotriazole, but not aryloxy fragments.

Table 3. Data of thermogravimetrical study

Compound R AT, ° T °C 1 exo? ^

4a 462-604 563

1a HO3S

423-543 531

U/V7

AT - temperature range corresponding to the maximum weight loss of the sample, Texo - maximum temperature of exo-effect

Table 2. Solubility of compounds 1a,b and 4a,b in organic solvents

Compound M R S ± 0.05 (CHCI3) S ± 0.05 (DMF)

Xmax, nm, (lge) mol/l g/l ^max, nm, (lge) mol/l g/l

4a HH 688 (4.92) 2.1 3.59 684, (4.82) 10.52 17.98

4b Cu 692 (4.92) 3.1 4.81 685, (4.87) 10.29 17.85

1a HH HO3S insoluble 694 (4.78) 7.71 15.90

1b Cu 692 (4.87) 7.72 16.05

S - solubility

Table 3 shows that introduction of sulfo groups into the molecule of 2,9,16,23-tetrakis(1-benzo-triazolyl)-3,10,17,24-tetrakis(4-cyclohexylphenoxy) phthalocyanine causes a decrease in the thermal stability of the corresponding sulfo-derivative on 33 °C.

Introduction of sulfo or alkylsulfamoyl groups into donor fragments of the previously studied mix-substituted phthalocyanines with benzotriazolyl substituents (Table 4) did not lead to the disappearance of mesomorphic properties. Moreover, in comparison with non-mesogenic homosubstituted phthalocyanine with eight benzotriazolyl substituents such substitution induced liquid crystallinity. However, we have found that the behavior of the compounds presented in this work is fundamentally different. Thus, sulfo-substituted copper phthalocyanine 1b melts at 200-220 °C and displays no mesomorphic properties. Compound 2b with

Mesomorphic properties

Phthalocyanine derivatives 1b and 2b were investigated by polarizing microscopy to study possibility to show mesomorphic properties. Previously, it was found that compounds 4a,b form a thermotropic mesophase [15].

octadecylsulfamoyl fragments melts at much lower temperature - 80-85 °C, while it also does not show mesomorphism. Therefore, both compounds showed no inclination to the mesophase formation.

Prognosis of mesomorphism

To explain the difference in mesomorphic behavior, molecular modeling of phthalocyanine derivatives 1-2 was performed with the help of HyperChem software using the method of molecular mechanics (MM+). On the basis of the modeling the molecular parameters (MP) were calculated and analyzed. MPs are the dimensionless parameters

Table 4. Influence of donor fragment structure on mesogenity of mix-substituted phthalocyanines

extracted from the structure of single molecules by comparing the calculated values with the classification series {1} [3, 15-19]:

K = 2-8.5; Kc =1-2.6; Kp = 0.2-0.7; Ks = 0.25-1.00; Mm = 0.2-0.8; Mr = 0.15-0.80; Kar = 0.08-0.30 {1}

Parameter K characterizes anisometry of a molecule as a whole. Parameters Kc and Kp characterize the central part and the periphery of molecule, respectively. Parameter Ks indicates the substitution degree of the central part by the

peripheral substituents. Parameter Mm takes into account the ratio of the central part mass and the periphery mass of the molecule. Parameter Mr takes into account the surrounding degree of the central part of the molecule by the peripheral substituents. Parameter Kar is proposed to take into account the packing density of the peripheral substituents [15-19].

Examples of the optimized models are presented in Figure 7.

c d

Fig. 7. Samples of optimized models of molecule of compounds 1a (a), 2a (b), 1b (c) and 2b (d)

Table 5. Calculated molecular parameters (MP) and the prognosis data for phthalocyanines 1a,b and 2a,b

Compound Eopt, kCal/mol Molecular parameter (MP) P E

Mm Mr kp K Kc Kar

1a 246.79 0.40 0.20 0.69 1.73' 1.17 0.27 - -

1b 283.16 0.44 0.22 0.69 1.73' 1.17 0.27 - -

2a 361.60 0.23 0.12* 0.24 1.45' 1.16 0.12 - -

2b 386.17 0.26 0.13* 0.24 1.37' 1.16 0.13 - -

Eopt - optimization energy, Ks = 0.50 for all compounds, P - prognosis of mesomorphism typical for DM; E - result of experiment. * - MP values closed to the boundary of the classification series (1). ' - MP values deviated significantly from the classification series {1}. Description of MPs - see in the text

The data on mesomorphism prognosis characteristic for DM showed that liquid crystalline properties for the synthesized compounds should not be expected (Table 5). In general, the negative prognosis is given for one of MPs, namely the K parameter, which characterizes the flatness of the molecule, i.e. the ratio of the maximum length of the molecule to its thickness. Since the molecules, according to the simulation data, are quite flat, they are located close to each other, thus creating the conditions for effective interaction between their n-systems. At the same time, in order to achieve a "crystal - mesophase" phase transition the system requires more energy, i.e. transition temperature to liquid crystal state is higher than the melting point of the compound. The enhancement of intermolecular interactions at introduction of sulfo groups can explain the decrease in solubility of compounds 1a,b in DMF, in comparison with the "parent" compounds 4a,b.

For octadecylsulfamoyl derivatives 2a,b the molecular parameter K as well as the molecular parameter Mr (Mr takes into account the number of substituents on the periphery) locate beyond the boundaries of the classification series {1}. The value of Mr is less than its lower boundary value in the classification series {1} (Table 5). This indicates the presence of free volume excess in the intermolecular space around molecules that impairs the microsegregation (i.e. it prevents molecules to self-organise and form supramolecular ensembles, which are mesophase structural units).

Conclusions

New sulfo and alkylsulfamoyl derivatives of phthalocyanine combining at the periphery 1-benzo-

triazolyl and cyclohexylphenoxy groups were synthesized. Elemental analysis proved that the studied phthalocyanines contain 4 sulfo or alkylsulfamoyl fragments. 1H NMR spectroscopy revealed that the substitution by sulfo groups occurs in the ortho-position to the oxygen bridge of the phenoxy-substituent. The effect of introduction of sulfo- and octadecylsulfamoyl groups into aryloxy substituents on the location of long-wave absorption bands of the synthesized compounds in concentrated sulfuric acid was found. The effect is expressed in hypsochromic shift of absorption bands in comparison with the starting compounds. It was established that the introduction of sulfo groups into bi-functionally substituted phthalocyanine molecules with 1-benzo-triazolyl and cyclohexylphenyl fragments leads to a decrease of the solubility of the synthesised compounds, decrease of the maximum temperature of the mass loss and the inability of the compounds to form a mesophase. All mentioned above can be explained by strengthening of intermolecular interactions between central parts of the molecules. The introduction of octadecylsulfamoyl substituents also contributes to the absence of mesomorphism, which, in our opinion, can be connected with sterical hindrance of liquid crystalline molecular packing.

The performed work for the first time revealed that introduction of bulky sulfo or alkylsulfamoyl fragments into ortho-position with respect to the oxygen atom of aryloxy group excludes manifestation of liquid crystalline properties. While substitution by the same fragments in para-position leads to formation of mesophase. It was shown that the presence of donor and acceptor fragments in mix-substituted phthalocyanines is important [4] but not determining factor for mesophase formation of disc-like molecules.

The work was supported by the Program of the Ministry of Education and Science of the Russian Federation in the framework of the state task for Ivanovo State University of Chemistry and Technology (Grant № 4.1929.2017/nH) and for Ivanovo State University to carry out research work in 2017-2019 (Grant № 16.1037.2017/n^) and partially supported by the RFBR (Grant № 16-03-00883a).

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nocmynma e peda^um 23.01.2017 г.

Received 23 January 2017