Porphyrin-containing polymacrocycles: synthesis and evaluation as fluorescent detectors of metal cations Текст научной статьи по специальности «Химические науки»

Porphyrins Порфирины

Макрогэтэроцмклы

http://macroheterocycles.isuct.ru

Paper Статья

DOI: 10.6060/mhc180276a

Porphyrin-Containing Polymacrocycles: Synthesis and Evaluation as Fluorescent Detectors of Metal Cations

Alexei A. Yakushev,a Alexei D. Averin,a'b@ Olga A. Maloshitskaya,b Oskar I. Koifman,c Sergei A. Syrbu,d and Irina P. Beletskayaab

aA.N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 119991 Moscow, Russia hLomonosov Moscow State University, Department of Chemistry, 119991 Moscow, Russia cIvanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia dG.A. Krestov Institute of Solution Chemistry RAS, 153045 Ivanovo, Russia @Corresponding author E-mail: alexaveron@yandex.ru

Using Pd(0)-catalyzed amination reaction of zinc 5,15-bis(4-bromophenyl)porphyrinate with diazatrioxamacrocy-cle - derivative of 3,3'-disubstituted biphenyl - a series of polymacrocyclic compounds was obtained. The investigation of their fluorescence in the presence of 18 metal cations revealed that two of them can act as molecular probes for Cu(II), Al(III) and Cr(III) by the fluorescence quenching. Tri- and tetramacrocyclic compounds of another structure were synthesized by the Pd(0)-catalyzed arylation of cryptands comprising central diazacrown ether moieties using zinc 5-(4-bromophenyl)porphyrinate. One of these compounds was characterized as a fluorescent chemosensor for Cu(II).

Keywords: Porphyrins, diazacrown ethers, polymacrocycles, Pd catalysis, amination, fluorescence, detection.

Порфирин-содержащие полимакроциклы: синтез и оценка в качестве флуоресцентных детекторов катионов металлов

А. А. Якушев,а А. Д. Аверин,^ O. А Малошицкаяь О. И. Койфман,с С. А. Сырбу^ И. П. Белецкая^

21Институт физической химии и электрохимии им. А.Н. Фрумкина РАН, 119991 Москва, Россия

ьМосковский государственный университет им. М.В. Ломоносова, Химический факультет, 119991 Москва, Россия

сИвановский государственный химико-технологический университет, 153000 Иваново, Россия

АИнститут химии растворов им. Г.А. Крестова РАН, 153045 Иваново, Россия

@Е-таИ: alexaveron@yandex.ru

С использованием Pd(0)-катализируемой реакции аминирования цинкового комплекса 5,15-бис(4-бромфенил) порфирина с диазатриоксамакроциклом - производным 3,3'-дизамещенного бифенила - получена серия полимакроциклических соединений. Исследование их флуоресценции в присутствии катионов 18 металлов показало, что два из них могут выступать в качестве молекулярных проб на катионы Си(11), А1(Ш) и Сг(Ш) за счет тушения флуоресценции. Три- и тетрамакроциклические соединения другого строения синтезированы Pd(0)-катализируемым аминированием криптандов, содержащих центральный фрагмент диазакраун-эфира с использованием цинкового комплекса 5-(4-бромфенил)порфирина. Одно из этих соединений охарактеризовано как флуоресцентный хемосенсор на катионы Си(11).

Ключевые слова: Порфирины, диазакраун-эфиры, полимакроциклы, Pd катализ, аминирование, флуоресценция, детектирование.

Porphyrin-Containing Polymacrocycles Introduction

Catalytic approaches to polymacrocyclic compounds based on porphyrins are well documented. The vast majority of such molecules are porphyrin dyads, triads and parent compounds, while the conjugates with other nitrogen-containing macrocycles are still enough rare. The synthesis of directly meso-meso -linked porphyrins without any spacer can be achieved via Ni(II)-catalyzed oxidative coupling of meso-bromoporphyrins[1] or using Suzuki coupling.[2,3] The chemistry of porphyrin oligomers built using various aromatic, heteroaromatic or other unsaturated linkers is much more explored as they can bring additional structural and physicochemical properties to a molecule. For this purpose Suzuki,[4-6] Stille,[78] Heck,[9] and Sonogashira[1011] couplings were successfully applied. Triazolyl linker can be easily introduced in the porphyrin dyads and triads by еру so-called click reactions,[12-14] and the application of Buchwald-Hartwig amination reactions was reported for the synthesis of bisporphyrin compounds in which two macroheterocyles were linked with a simple NH fragment,[15] a series of di- an polyporphyrin compounds was obtained by a similar approach in which diamines or diazacrown ether moieties served as linkers.[1617] While porphyrins possess extremely interesting photophysical properties together with their unique binding of metal cations, they have not yet become a widespread platform for creating colorimetric or fluorimetric chemosensors. The examples are still scarce, to mention the porphyrin-terpyridine conjugate which can detect Cd(II) with moderate selectivity,[18] tetrafo's(4-methoxyphenyl)porphyrin for sensing Ag(I),[19] and another detector of the same cation employing the combination of the porphyrin and quinoline moieties.[20] Recently we have described the catalytic synthesis of porphyrin conjugates with azacrown ethers and tested them as fluorimetric detectors of metal cations.[2122] In continuation of this research here we report the synthesis of the polymacrocyclic derivatives of porphyrin comprising biphenyl-based diazatrioxa-macrocycle and cryptands with diazacrown ether moieties.

Experimental

NMR spectra were registered using Bruker Avance 400 spectrometer, MALDI-TOF spectra were obtained with Bruker Autoflex II spectrometer using 1,8,9-trihydroxyanthracene as matrix and PEGs as internal standards. UV-Vis spectra were recorded with Agilent Cary 60 spectrophotometer in MeCN, spectra of fluorescence were obtained with Hitachi 2700 spec-trofluorometer in acetonitrile (UHPLC grade). Rac-BINAP and DavePhos ligands, sodium tert-butoxide, were purchased from Sigma-Aldrich Co and used without further purification, Pd(dba)2 was synthesized according to the method described.[23] Macrobicycle 3 was obtained according to the described method,[24] macrobicycles 12-14 were synthesized according to a published proce-dure,[25] zinc porphyrinates 4, 15 and 18 were obtained by method described in ref.[26] Column chromatography was carried out using silica gel 40-63 nm (Fluka). Acetonitrile of UHPLC grade was used without additional purification, dioxane was successively distilled over NaOH and sodium. Dichloromethane was distilled over CaH2, methanol was used freshly distilled.

Method for the synthesis ofpolymacrocycles 5-8, 16, 17, 19, 20. A two-neck flask equipped with a magnetic stirrer and reflux

condenser, flushed with dry argon, was charged with corresponding amounts of Pd(dba)2, DavePhos, zinc porphyrinates 4 or 18, macrocyclic compound 3 or cryptands 12-14, absolute dioxane and sodium ferf-butoxide. The reaction mixture was stirred under reflux for 24h, cooled down to ambient temperature, the residue was filtered off, washed with CH2Cl2 (5 ml), the combined organic fractions were evaporated in vacuo and the residue was chromato-graphed on silica gel using a sequence of eluents: CH2Cl2, CH2Cl2 - MeOH 500:1 - 3:1.

Trismacrocyclic compound 5. Obtained from zinc porphy-rinate 4 (0.1 mmol, 102 mg), macrocycle 3 (0.2 mmol, 74 mg) in the presence of Pd(dba)2 (16 mol %, 9 mg), DavePhos (18 mol %, 7 mg), fBuONa (0.3 mmol, 29 mg) in 2 ml dioxane. Eluent: CH2Cl2-MeOH 100:1. Yield 14 mg (9 %), dark-red crystalline powder. M.p. 195-200 0C. m/z (MALDI-TOF) found: 1596.9069. C100H124N8O6Zn requires 1596.8935 [M]+. UV-Vis (CH3CN) Xmax (lge) nm: 416 (5.29). 1H NMR (CDCl3, 298 K) SH ppm: 1.00 t (12H, 3J=7.3 Hz), 1.54-1.61 m (12H), 1.78 quintet (8H, 3J=7.4 Hz), 2.17-2.26 m (12H), 2.63 s (12H), 3.24 br.t (4H, 3Jo)s=4.7 Hz), 3.31 br.s (4H), 3.33-3.63 m (16H), 3.67 br.t (4H, 3Jo)s=4°.9 Hz), 4.00 br.s (8H), 4.21 t (4H, 3J=6.1 Hz), 5.70 br.s (2H), 6°.i2 br.s (2H), 6.90 d (2H, 3J=7.2 Hz), 7.00 t (2H, 3J=7.1 Hz), 7.16 d (2H, 3J=7.3 Hz), 7.28 d (2H, 3J=8.5 Hz), 7.36-7.43 m (8H), 7.87 d (4H, 3J=7.6 Hz), 10.14 s (2H) (NH protons were not assigned). 13C NMR (CDCl3, 298 K) Sc ppm: 14.2 (4C), 15.4 (4C), 22.9 (4C), 26.9 (4C), 27.8 (2C), 27.9 (2C), 32.7 (4C), 33.2 (4C), 42.9 (2C), 49.1 (2C), 68.5 (2C), 70.5 (2C), 70.7 (2C), 70.8 (2C), 70.9 (2C), 80.0 (2C), 97.2 (2C), 111.2 (2C), 113.1 (2C), 116.9 (2C), 118.9 (2C), 120.2 (4C), 120.4 (2C), 129.0, 129.1, 134.1 (4C), 137.2, 137.9, 141.9, 143.1, 146.3, 147.2, 147.5, 148.1, 149.3 (6 quaternary carbon atoms of the biphenyl moieties were not assigned, carbon atoms of the porphyrin moiety were not integrated).

Bismacrocycle 6 was isolated as the second compound in the synthesis of frismacrocycle 5. Eluent: CH2Cl2-MeOH 500:1. Yield 20 mg (16 %), dark-red crystalline powder. M.p. 148-150 0C. m/z (MALDI-TOF) found: 1228.6770. C78H96N6O3Zn requires 1228.6835 [M]+. UV-Vis (CH3CN) Xmax (lge;)) nm: 414 (5.28). 1H NMR (CDCl3, 298 K) SH ppm: 0.98 t (6H, 3J=7.1 Hz), 0.99 t (6H, 3J=7.1 Hz), 1.52-1.60 m (10H), 1.70-1.80 m (8H), 2.16-2.25 m (10H), 2.45 s (6H), 2.61 s (6H), 3.13 br.t (2H, 3Jo)s=4.5 Hz), 3.23 br.s (2H), 3.33-3.60 m (8H), 3.65 br.t (2H, 3Jo)j=5.Yhz), 3.93-4.02 m (8H), 4.20 t (2H, 3J=6.1 Hz), 5.49 br.s (1H) 5.91 br.s (1H), 6.87 d (1H, 3J=7.3 Hz), 6.93 t (1H, 3J=7.3 Hz), 7.14 d (1H, 3J=7.2 Hz), 7.27 d (1H, 3J=8.7 Hz), 7.31-7.40 m (5H), 7.70-7.80 m (2H), 7.84 d (2H, 3J=8.0 Hz), 8.08 d (2H, 3J=8.0 Hz), 10.14 s (2H) (NH protons were not assigned).

Teframacrocycle 7 was isolated as the third compound in the synthesis of frismacrocycle 5. Eluent: CH2Cl2-MeOH 200:1. Yield 11 mg (9 %), dark-red solid. m/z (MALDI-TOF) found: 2455.42. C156H190N12O6Zn2 requires 2455.35 [M]+. 1H NMR (CDCl3, 298 K) SH ppm: 0.96 t (6H, 3J=7.1 Hz), 0.98 t (18H, 3J=6.9 Hz), 1.56 br.s (16H), 1.75 br.s (16H), 1.84-1.94 m (6H), 2.20 br.s (18H), 2.63 s (12H), 2.67 s (12H), 3.22 t (2H, 3J=5.6 Hz), 3.40-3.78 m (24H), 3.92 br.s (4H), 3.99 br.s (12H), 4.22 br.s (6H), 6.50 d (2H, 3J=7.8 Hz), 6.60 d (2H, 3J=7.3 Hz), 6.82 s (2H), 6.90 t (2H, 3J=7.8 Hz), 7.02 s (2H), 7.19 t (2H, 3J=7.5 Hz), 7.21 t (2H, 3J=7.7 Hz), 7.32-7.52 m (11H), 7.89-8.10 m (8H) (NH protons were not assigned). 13C NMR (CDCl3, 298 K) SC ppm: 14.04 (2C), 14.18 (6C), 15.45 (4C), 15.52 (4C), 22.84 (8C), 26.81 (8C), 27.55 (2C), 28.26 (1C), 28.74 (1C), 32.52 (2C), 32.59 (6C), 33.10 (8C), 42.61 (1C), 47.66 (1C), 52.79 (1C), 53.40 (1C), 68.73 (1C), 70.55 (4C), 70.78 (2C), 70.94 (4C), 71.12 (1C), 97.45 (4C), 110.53, 110.81, 111.20, 112.31, 115.31, 115.98, 116.41, 120.19-120.47 m, 129.24, 129.34, 129.49, 133.31, 134.02, 134.11, 134.28, 138.13, 142.63, 143.01, 143.34-143.46 m, 144.82, 146.38, 147.71, 148.18, 148.88, 149.21 (aromatic carbon atoms are not enough characteristic as they possess very close chemical shifts and form complicated multiplets).

Pentamacrocycle 8 was isolated as the fourth compound in the synthesis of trismacrocycle 5. Eluent: CH2Cl2-MeOH 100:1. Yield 13 mg (9 %), dark-red solid. m/z (MALDI-TOF) found: 2823.64. C178H218N14O9Zn2 requires 2823.56 [M]+. 'H NMR (CDCl3, 298 K) SH pjpm: 1.00 t (24H, 3J=7.1 Hz), 1.51-1.65 m (20H), 1.72-1.83 m (16H), 2.17 br.s (8H), 2.13-2.28 m (16H), 3.07 br.s (4H), 3.30-3.48 m (24H), 3.57 br.t (4H, 3Joiu=4.4 Hz), 3.64 t (8H, 3J=5.4 Hz), 4.00 br.s (16H), 4.20 br.s (8H)° 5.80 s (2H), 6.06 s (1H), 6.07 s (1H), 6.33 s (2H), 6.87 d (2H, 3J=8.5 Hz), 7.05 t (2H, 3J=7.5 Hz), 7.13 d (2H, 3J=7.6 Hz), 7.27-7.52 m (20H), 7.86 d (4H, 3J=7.6 Hz), 7.97 d (4H, 3J=7.5 Hz), 10.15 s (4H) (NH were not assigned). 13C NMR (CDCl3, 298 K) SC ppm: 14.22 (8C), 15.41 (4C), 15.51 (4C), 22.86 (8C), 26.88 (8C), 27.44 (2C), 27.87 (2C), 28.32 (2C), 32.66 (8C), 33.25 (8C), 42.96 (2C), 49.06 (2C), 49.46 (2C), 68.7 (2C), 70.3-70.9 m (16C), 97.14 (4C) 111.61, 111.88, 113.36, 116.47, 117.27, 118.80, 118.88, 119.34, 119.68, 119.98, 120.46, 120.61, 120.87, 121.17, 128.61, 128.87, 129.42, 136.81, 137.56, 137.99, 141.45, 141.82, 143.14, 143.20, 143.41, 146.31, 147.49, 147.84, 148.05, 148.20, 149.15 (signals of aromatic carbon atoms are not enough characteristic due to line broadening of some signals and impossibility of the identification of some quaternary carbon atoms).

Tetramacrocyclic compound 16. Obtained from zinc porphy-rinate 15 (0.3 mmol, 226 mg), cryptand 12 (0.15 mmol, 92 mg) in the presence of Pd(dba)2 (16 mol%, 14 mg), BINAP (18 mol%, 17 mg), tBuONa (0.45 mmol, 43 mg) in 5 ml of dioxane. Eluent: CH2Cl2-MeOH 10:1. Yield 68 mg (23 %), dark-red solid. m/z (MALDI-TOF) found: 1955.05. C118H146N12O6Zn2 requires 1955.01 [M]+. 'H NMR (CDCl3, 298 K) SH ppm: 0.97 t (12H, 3J=6.8 Hz), 1.49 sextet (8H, 3J=7.0 Hz), 1.63 quintet (8H, 3J=6.2 Hz), 2.01-2.14 m (12H), 2.34 br.s (8H), 2.56 s (12H), 3.15-3.46 m (24H), 3.31 s (12H), 3.36 s (12H), 3.47-3.65 m (16H), 6.76-6.80 m (4H), 7.30-7.85 m (10H), 7.90-7.96 m (4H).

Tetramacrocyclic compound 17. Obtained from zinc porphyrinate 15 (0.348 mmol, 262 mg), cryptand 13 (0.174 mmol, 115 mg) in the presence of Pd(dba)2 (16 mol %, 16 mg), DavePhos (18 mol %, 12 mg), tBuONa (0.522 mmol, 50 mg) in 3.5 ml of dioxane. Eluent: CH2Cl2-MeOH 10:1. Yield 70 mg (20%), dark-red crystalline powder, m.p. 145-1500C. m/z (MALDI-TOF) found: 1998.99. C120H150N12O7Zn2 requires 1999.03 [M]+. UV-Vis (CH3CN) Xmax nm (lge): 409 (5.429). 'H NMR (CDCl3, 298 K) SH ppm: 0.97 t"(12H, 3J=7.2 Hz), 1.52 sextet (8H, 3J=7.1 Hz), 1.67 quintet (8H, 3J=6.9 Hz), 2.11 quintet (8H, 3J=6.6 Hz), 2.19 quintet (4H, 3J=6.4 Hz), 2.34 br.s (8H), 2.50 s (12H), 2.87 br.s (8H), 3.00 br.s (8H), 3.23-3.51 m (12H), 3.35 s (24H), 3.69 br.s (4H), 3.79 br.s (4H), 3.86 t (4H, 3J=7.6 Hz), 6.70 br.s (4H), 6.96 br.s (4H), 7.32-7.40 m (4H), 7.47-7.57 m (4H), 9.35 s (2H), 9.70 s (4H). 13C NMR (CDCl3, 298 K) SC ppm: 11.4 (4C), 12.0 (4C), 14.1 (4C), 15.3 (4C), 22.7 (4C), 26.3 (4C), 27.8 (2C), 32.3 (4C), 32.9 (4C), 49.1 (2C), 53.2 (4C), 58.4 (2C), 68.0 (2C), 68.2 (4C), 69.1 (4C), 69.6 (2C), 70.0 (2C), 95.8 (2C), 96.6 (4C), 113.3, 119.6, 121.7, 125.5, 126.0, 127.8, 129.9, 135.4, 137.7, 140.8, 145.0, 146.6, 147.4, 147.6 (6 quaternary carbon atoms were not assigned, not all quaternary carbon atoms of the porphyrin moiety were integrated).

Tetramacrocyclic compound 19. Obtained from zinc porphyrinate 18 (0.316 mmol, 238 mg), cryptand 14 (0.158 mmol, 100 mg) in the presence of Pd(dba)2 (16 mol%, 15 mg), DavePhos (18 mol %, 11 mg), tBuONa (0.5 mmol, 48 mg) in 2 ml of dioxane. Eluent: CH2Cl2-MeOH 10:1. Yield 33 mg (11 %), dark-red solid. m/z (MALDI-TOF) found: 1971.03. C118H146N12O7Zn2 requires 1971.00 [M]+. 1H NMR (CDCl3, 298 K) SH ppm: 0.99 t (12H, 3J=7.1 Hz), 1.52 br.sextet (8H, 3J=6.0 Hz), 1.65 br.s (8H), 2.04 br.s (8H), 2.37 br.s (8H), 2.60 s (12H), 3.08 br.s (8H), 3.27-3.60 m (24H), 3.33 s (12H), 3.35 s (12H), 3.66 br.s (8H), 3.78 br.s (4H), 6.46 br.s (2H), 6.85 br.s (2H), 6.93 br.s (2H), 7.13 br.s (2H), 7.29 br.d (2H, 3Jobs=7.8 Hz), 7.41 br.s (2H), 7.54-7.62 m (2H), 7.71 br.d (2H, 3Jobs=7°.^Hz), 9.65 s (4H), 9.77 s (2H). 13C NMR (CDCl3, 298 K) SC ppm: 11.3 (4C), 12.0 (4C), 14.1 (4C), 15.3 (4C), 22.7 (4C), 26.1 (4C), 32.3 (4C), 32.9

(4C), 51.9 (2C), 52.5 (4C), 58.2 (2C), 67.9-70.6 m (14C), 95.6 (2C), 96.6 (4C), 119.1, 120.2, 121.3, 122.2, 126.7, 127.8, 129.0, 135.3, 137.3, 137.6, 140.7, 145.0, 146.3, 146.5, 146.7, 147.4, 147.7, 148.0 (6 quaternary carbon atoms were not assigned, not all quaternary carbon atoms of the porphyrin moiety were integrated).

Trismacrocycle 20 was isolated as the second compound in the synthesis of tetramacrocycle 19. Eluent: CH2Cl2-MeOH 5:1. Yield 33 mg (16 %), dark-red crystalline powder. M.p. 147-152 0C. m/z (MALDI-TOF) found: 1300.6934. C76H100N8O7Zn requires 1300.7006 [M]+. UV-Vis (CH3CN) Xmax (lge) nm: 411 (5.32). 1H NMR (CDCl3, 298 K) SH ppm: 0.98 t (6H, 3J=7.3 Hz), 1.55 sextet (4H, 3J=7.4 Hz), 1.72 quintet (4H, 3J=7.4 Hz), 2.23 quintet (4H, 3J=7.4 Hz), 2.40 br.s (8H), 2.61 s (6H), 2.90 br.s (8H), 3.08 br.s (8H), 3.15 br.s (4H), 3.33 br.s (4H), 3.35 s (4H), 3.45 s (6H), 3.49 s (6H), 3.62 br.t (4H, 3Jobs=4.6 Hz), 3.89 t (4H, 3J=5.6 Hz), 6.49 br.s (2H), 6.79 br.s (2H), 7.16 br.s (4H), 7.28 d (1H, 3J=7.7 Hz), 7.56 t (1H, 3J=7.6 Hz), 7.64 s (1H), 7.74 d (1H, 3J=6.9 Hz), 9.70 s (1H), 9.84 s (2H) (NH proton was not assigned).

Results and Discussion

At the first step of our research we synthesized the macrocycle 3 comprising 3,3'-disubstituted biphenyl and trioxadiamine moieties. The synthesis was carried out according to a known procedure,[24] starting from 3,3'-dibromobiphenyl (1) and linear trioxadiamine 2, in the presence of a standard catalytic system Pd(dba)2/ BINAP (dba=dibenzylideneacetone, BINAP=2,2'-6is(diphenylphosphino)-1,r-binaphthalene). The target compound was isolated in 40 % yield and introduced in the second catalytic reaction with zinc 5,15-di(4-bromophenyl)porphyrinate 4 (Scheme 1). This coupling was conducted using DavePhos phosphine ligand (DavePhos=2-(dicyclohexylphosphino)-2,2'-dimethylami-nobiphenyl) as special experiment revealed the superiority of this donor ligand over more conventional BINAP in the arylation of the secondary amino groups with bromo-phenyl porphyrinates. It was also important to use Zn(II) complex as free porphyrins often failed to give desired products in similar arylation reactions. The ratio of the starting compounds 3:4 was taken as 2:1, as a result we obtained a series of polymacrocycles: the expected trimacrocycle 5, i.e. the product of the diamination of di(bromophenyl) porphyrin, the product of monoamination 6, and oligomeric tetracyclic and pentacyclic compounds 7 and 8 (Scheme 1). Compounds 6 and 7 were formed in the result of the catalytic amination and catalytic reduction of the C-Br bonds. The isolated yields of all these compounds were small and ranged from 9 to 16 %. The isolation of individual products by chromatography on silica gel was quite tedious and obviously oligomers with higher molecular masses were not obtained in individual state.

Another structural type of porphyrin-containing polymacrocycles is based on the cryptand-like derivatives of diazacrown ethers 12-14. These compounds were obtained by a previously described method[25] in sufficient yields (24-38 %) (Scheme 2), they differ by the size of the central diazacrown moiety as well by the nature of the trioxa-diamine linker and substitution pattern in the benzyl spacers. Cryptands 12 and 13 were introduced in the Pd(0)-catalyzed diarylation reaction with zinc 5-(4-bromophenyl) porphyrinate 15 (2 equiv.) using the same catalytic system

Br h2n

Pd(dba)2/BINAP (8/9 mol%) iBuONa, dioxane, reflux

3, 40%

Am

Am

Am Am

4

Pd(dba)2/DavePhos fBuONa, dioxane, reflux

6,16%

8, 9%

Scheme 1.

Pd(dba)2/DavePhos as in the previous case. As the number of reaction centers decreased in these processes, the target tetramacrocyclic products of diarylation 16 and 17 were isolated in fairly better yields (23 and 20 %, respectively) (Scheme 2). It is interesting that in the case of the reaction of zinc porphyrinate 15 with the cryptand 12 BINAP was found to be also efficient for the coupling.

Next we explored the possibility to introduce an isomeric zinc 5-(3-bromophenyl)porphyrinate 18 in the similar reaction with the cryptand 14 (Scheme 3). Porphyrin derivative 18 possesses less active bromine atom compared to its isomer 15 in which bromine is situated in para-position to a strong electron-withdrawing porphyrin unit. As expected, the reaction with less reactive zinc porphyrinate 18 resulted in a lower yield of the desired )isporphyrin tetramacrocycle 19 (11 %) while the product

of monoarylation, i.e. trimacrocycle 20 was obtained in 16 % yield (Scheme 3).

We investigated the possibilities of polymacrocyclic compounds to act as fluorescent chemosensors for metal cations. In the course of investigation UV-Vis and fluorescent spectra of the polymacrocycles 5, 6, 17 and 20 were recorded in MeCN in the presence of 1, 2, 5 equiv. (in some cases also 10, 20, 30 equiv.) of corresponding metal perchlorates: Li(I), Na(I), K(I), Mg(II), Ca(II), Ba(II), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cr(III), Cu(II), Zn(II), Cd(II), Hg(II), Ag(I), Pb(II). It was found out that the èismacrocyclic compound 6 could serve as the fluorescent molecular probe for Cu(II), Al(III) and Cr(III) cations because the addition of only these metals led to full quenching of emission (Figure S1). To achieve this full quenching, one needs 2 equiv. of Al(III) (Figure S2), 5 equiv.

9: n = 1, m-Br 10: n = 2, m-Br 11: n = 2, p-Br

12: n = 1, m-NH, X = CH2OCH2CH2och2ch2och2, 38% 13: n = 2, m-NH, X = CH2OCH2CH2OCH2CH2och2, 36% 14: n = 2, p-NH, X = 0CH2CH20CH2CH20, 24%

o o

,N NU

H

V

HN NH

O O O

Am

Am

Am

12: n = 1, m-NH 13: n = 2, p-NH

Pd(dba)2/L iBuONa, dioxane, reflux Am^V.

L = BINAP (with 12) L = DavePhos (with 13)

Am

16: n = 1, m-N, 23% 17: n = 2, p-N, 20%

Scheme 2.

Me Me

18, 2 equiv.

Scheme 3.

of Cr(III) (Figure S3) or only 1 equiv. of Cu(II). We carried out both UV-Vis and fluorescent titrations (Figures S4, S5) and calculated the stability constants of two complexes with Cr(III): for (6)-Cr(III) complex lg£=6.20±0.10 and for (6>2Cr(ffl) lg£=12.25±0.07. In UV-Vis spectra Cr(III) and Al(III) caused insignificant decrease in the intensity of the absorption band with bathochromic shift by 12 nm while the addition of Cu(II) salt led to a disappearance of this absorption band.

Emission of the frismacrocycle 5 with one central porphyrin and two peripherical diazatrioxamacrocycles is less susceptible to the addition of Cr(III) as only 10 equiv. led to full quenching (Figure S6). However, Cu(II) and Al(III) quench emission efficiently (Figure S7), thus this molecule can be also regarded as a molecular probe for these three cations. The effect of the metal cations on the UV-Vis spectra are quite similar to that of compound 6 (Figure S8).

Tetramacrocyclic ligand 17 can be seen as a chemo-sensor for Cu(II) cations as only this metal fully quenches its emission upon addition of 10 equiv. (Figures S9, S10). Moreover, this detector is characterized by a low detection limit (0.23 ^M). The stability constant of the complex (17)-Cu(II) was found to be equal lg£=5.15±0.04 by fluo-rimetric titration. Trismacrocyclic compound 20 which includes only one porphyrin structural unit and possesses a slightly shorter trioxadiamine linker though selectively responses for Cu(II) cations, is less efficient in detecting this metal as its emission diminishes only 2.5 times after the addition of 15 equiv. of this metal (Figures S11, S12). This fact implies the necessity of fine tuning of the poly-macrocyclic structures for increasing selectivity and sensitivity of the detector. In UV-Vis spectra of polymacrocycles 17 and 20 the decrease in the intensity of the absorption maxima upon addition of Cu(II) cations without notable shift was observed (Figures S13, S14).

Conclusions

To sum up, our research revealed the possibility to construct polymacrocyclic compounds incorporating porphyrin and oxaazamacrocyclic structural units using Pd(0)-catalyzed amination reactions. They were tested as potential fluorimetric detectors of metal cations and the strong dependence of the emission quenching in the presence of certain cations on the type and number of macrocycles attached to porphyrin units was firmly established. Two of them (monoporphyrin-based bisand trismacrocycles 5 and 6) were found to be prospective fluorescent detectors for Al(III), Cr(III) and Cu(II) while tetramacrocyclic bisporphyrin derivative 17 can serve as the fluorimetric chemosensor for Cu(II).

Acknowledgements. The authors acknowledge the financial support of the RFBR grant 16-29-10685 for the synthesis of starting compounds and spectral investigations and RSF grant 14-23-00186P for the catalytic synthesis of porphyrin-containing polymacrocycles.

References

1. Lu X.Q., Guo Y., Chen Q.Y. Synlett 2011, 2011(1), 77-80.

2. Cheng F.Y., Zhang S., Adronov A., Echegoyen L., Diederich F.

Chem. Eur. J. 2006, 12, 6062-6070.

3. Filatov M.A., Guilard R., Harvey P.D. Org. Lett. 2010, 12,

196-199.

4. Hyslop A.G., Kellett M.A., Iovine P.M., Therien M.J. J. Am. Chem. Soc. 1998, 120, 12676-12677.

5. Chung L.L., Chang C.J., Nocera D.G. J. Org. Chem. 2003, 68, 4075-4078.

6. Yu L.H., Lindsey J.S. Tetrahedron 2001, 57, 9285-9298.

7. Sergeeva N.N., Scala A., Bakar M.A., O'Riordan G., O'Brien J., Grassi G., Senge M.O. J. Org. Chem. 2009, 74, 7140-7147.

8. Frampton M.J., Akdas H., Cowley A.R., Rogers J.E., Slagle J.E., Fleitz P.A., Drobizhev M., Rebane A., Anderson H.L. Org. Lett. 2005, 7, 5365-5368.

9. Odobel F., Suresh S., Blart E., Nicolas Y., Quintard J.P., Janvier P., Le Questel J.Y., Illien B., Rondeau D., Richomme P., Haupl T., Wallin S., Hammarstorm L. Chem. Eur. J. 2002, 8, 3027-3046.

10. Fazekas M., Pintea M., Senge M.O., Zawadzka M. Tetrahedron Lett. 2008, 49, 2236-2239.

11. Sato T., Nakagawa T., Okada H., Matsuo Y. J. Porphyrins Phthalocyanines 2015, 19, 451-458.

12. Severac M., Le Pleux L., Scarpaci A., Blart E., Odobel F. Tetrahedron Lett. 2007, 48, 6518-6522.

13. Polevaya Y.P., Tyurin V.S., Beletskaya I.P. J. Porphyrins Phthalocyanines 2014, 18, 20-34.

14. Yaschuk Y.P., Tyurin V.S., Beletskaya I.P. Macroheterocycles 2012, 5, 302-307.

15. Esdaile L.J., Senge M.O., Arnold D.P. Chem. Commun. 2006, 4192-4194.

16. Mikhalitsyna E.A., Tyurin V.S., Khrustalev V.N., Lonin I.S., Beletskaya I.P. Dalton Trans. 2014, 43, 3563-3575.

17. Mikhalitsyna E.A., Tyurin V.S., Beletskaya I.P. J. Porphyrins Phthalocyanines 2015, 19, 874-886.

18. Luo H.-Y., Jiang J.-H., Zhang X.-B., Li Ch.-Y., Shen G.-L., Yu R.-Q. Talanta 2007, 72, 575-581.

19. Li Ch.-Y., Xu F., Li Y.-E. Spectrochim. Acta, Part A 2010, 76,

197-201.

20. Han Z.-X., Luo H.-Y., Zhang X.-B., Kong R.-M., Shen G.-L., Yu R.-Q. Spectrochim. Acta, Part A 2009, 72, 1084-1088.

21. Yakushev A.A., Averin A.D., Maloshitskaya O.A., Syrbu S.A., Koifman O.I., Beletskaya I.P. Mendeleev Commun. 2016, 26, 199-201.

22. Yakushev A.A., Averin A.D., Maloshitskaya O.A., Syrbu S.A., Koifman O.I., Beletskaya I.P. Macroheterocycles 2016, 9, 65-72.

23. Ukai T., Kawazura H., Ishii Y., Bonnet J.J., Ibers J.A. J. Organomet. Chem. 1974, 65, 253-266.

24. Averin A.D., Uglov A.N., Buryak A.K., Beletskaya I.P. Mendeleev Commun. 2010, 20, 1-3.

25. Yakushev A.A., Chernichenko N.M., Anokhin M.V., Averin A.D., Buryak A.K., Denat F., Beletskaya I.P. Molecules 2014, 19, 940-965.

26. Mikhalitsyna E.A., Tyurin V.S., Nefedov S.E., Syrbu S.A., Semeikin A.S., Koifman O.I., Beletskaya I.P. Eur. J. Inorg. Chem. 2012, 36, 5979-5990.

Received 13.02.2018 Accepted 22.02.2018