Synthesis and X-ray structure of the Monofunctionulized Amide-Terminated Phenylsulfide iron(ii) clathrochelates Текст научной статьи по специальности «Химические науки»

Clathrochelates

Клатрохелаты

Макрогэтероцмклы

http://macroheterocycles.isuct.ru

Paper

Статья

DOI: 10.6060/mhc171147v

Synthesis and X-Ray Structure of the Monofunctionulized Amide-Terminated Phenylsulfide Iron(II) Clathrochelates

Serhii V. Vakarov,a Oleg A. Varzatskii,a,b Alexander S. Belov,c Alexander A. Pavlov,c Yan V. Zubavichus,d Anna V. Vologzhanina,c and Yan Z. Voloshinc,e@

Dedicated to Academician Aslan Yu. Tsivadze on the occasion of his 75th Birthday

aVernadskii Institute of General and Inorganic Chemistry NASU, 03080 Kyiv, Ukraine

bSC Princeton Biomolecular Research Labs, 01042 Kyiv, Ukraine

cNesmeyanov Institute of Organoelement Compounds RAS, 119991 Moscow, Russia

dKurchatov Complex for Synchrotron and Neutron Investigations, National Research Centre "Kurchatov Institute ", 123182 Moscow, Russia

eKurnakov Institute of General and Inorganic Chemistry RAS, 119991 Moscow, Russia @Corresponding author E-mail: voloshin@ineos.ac.ru

The monoamide-terminated cage complexes FeBd2(X-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2 (where Bd2- is a-benzyldioxime dianion, Gm is glyoxime residue, X is ortho- or meta-, or para-substituent) were obtained using one-pot two-step synthetic procedure that includes (i) the reaction of its monocarboxyl-terminated clathrochelate precursor with 1,1'-carbonyldiimidazole (CDI), giving the corresponding azaheterocycle-terminated intermediate, and (ii) its cleavage with R(+)-phenylethylamine leading to the target iron(II) clathrochelate with terminal optically active amide group. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass-spectrometry, IR, UV-Vis, 1H and 13C{1H} NMR spectra, and by single crystal X-ray diffraction (for a meta-substituted constitutional isomer). The number, position and integral intensities of the signals in their 1H NMR spectra confirmed the composition of the macrobicyclic molecules. The number of the signals in their 13C NMR spectra suggests the absence of the C2 symmetry axes passing through the middles of the chelate C-C bonds and of the symmetry plane also passing through these points and the encapsulated iron(II) ion as well. As follows from X-ray diffraction data, the encapsulated iron(II) ion in the molecule FeBd2((meta-R(+)-PhCH(CH3)NHOCC 6H4S)GmH)(BF)2 is situated in the centre of its FeN-coordination polyhedron with Fe-N distances falling in the range 1.8904(4)-1.9404(7) Â. This polyhedron possesses the geometry intermediate between a trigonal prism and a trigonal antiprism with the average distortion angle p of 24.2°; its height h is equal to 2.34 Â and the average bite (chelate) angle a is approximately 78.2°. The terminal PhCH(CH)NH group of the above clathrochelate molecule is equiprobably disordered over two sites with opposite orientation of its methyl and phenyl substituents; the N-H...F-bonded clathrochelate dimers are formed in its X-rayed crystal.

Keywords: Macrocycles, clathrochelates, cage complexes, iron complexes, ligand reactivity.

Introduction

Tra-dioximate metal clathrochelates[1,2] are the three-dimentional macrobicyclic complexes with an encapsulated metal ion, possessing the specific geometry of their MN6-coordination polyhedra that is intermediate between a trigonal prism (TP, the distortion angle j= 0°) and a trigonal anti-prism (TAP, j=60°). Due to such TP-TAP-distorted geometry, these polyhedra have no inversion centre and possess an inherent chirality. On the other hand, an equiprobability of their left(^)- and right(^)-handed distortions, and a rapid transition between them cause the absence of an optical activity of these cage complexes. Hence, a selective fixation of one of these C3-distorted conformations may result in an appearance of a CD signal in their spectra in the range of the visible metal-to-ligand charge transfer (MLCT) bands

(400-600 nm). Indeed, we have recently found[3] an ability of the above quasiaromatic polyazomethine complexes to give a CD response upon their supramolecular interactions with or covalent binding to the chiral inductors, such as biomacromolecules, or low-molecular optically active compounds, respectively. To observe an effect of the low-molecular chiral inductor, the CD spectra of the dicarbo-xyphenylsulfide iron(II) clathrochelates upon their covalent binding to R(+)-1-phenylethylamine, giving the corresponding diamide-functionalized cage complexes, have been measured.[3] In this paper, we report the synthesis, X-ray structure and spectral characteristics of their monofunction-alized macrobicyclic analogs, the molecules of which bear the single optically active amide group and, therefore, are prospective optically active compounds and CD probes for biomacromolecules.

Синтез и рентгеновская структура монофункционализированных фенилсульфидных клатрохелатов железа(П) с терминальной амидо - группой

С. В. Вакаров,а О. А. Варзацкий,аЬ А. С. Белов,с А. А. Павлов,с Я. В. Зубавичус,й А. В. Вологжанина,с Я. З. Волошинсе@

Посвящается академику А.Ю. Цивадзе по случаю его 75-летнего юбилея

aИнститут общей и неорганической химии им. В.И. Вернадского НАН Украины, 03680 Киев, Украина ъПринстонские лаборатории биомолекулярных исследований, 01042 Киев, Украина cИнститут элементоорганических соединений им. А. Н. Несмеянова, 119991 Москва, Россия Курчатовский комплекс синхротронно-нейтронных исследований, Национальный исследовательский центр "Курчатовский институт", 123182Москва, Россия

еИнститут общей и неорганической химии им. Н.С. Курнакова РАН, 119991 Москва, Россия @E-mail: voloshin@ineos.ac.ru

С использованием двухстадийной синтетической процедуры без выделения интермедиата методики были получены моноамидные комплексы FeBd2(X-R(+)-PhCH(CH3)NHOCC6H4¿S)GmH)(BF)2 (где Bd2- - дианион а-бензилдиоксима, Gm - остаток глиоксима, X- орто-, мета- или пара-заместитель). Процедура включает: (1) реакцию исходного клатрохелата с терминальной карбоксильной группой с 1,1'-карбонилдиимидазолом, приводящую к соответствующему интермедиату с азагетероциклической группой; (2) её расщепление под действием R(+)-фенилэтиламина, приводящее к целевому клатрохелату железа(П) с терминальной оптически активной амидной группой. Полученные комплексы были охарактеризованы методом элементного анализа, MALDI-TOF масс-спектрометрии, ИК, ЭСП, 1Н и 13С(1Н} ЯМР-спектроскопии и рентгеноструктурного анализа (для мета-замещенного конституционального изомера). Количество, положение и интегральные интенсивности сигналов в 1Н ЯМР спектрах подтвердили состав макробициклических молекул. Число сигналов в 13С ЯМР спектрах указывает на отсутствие осей С2 симметрии, проходящих через середины хелатных связей С—С, а также плоскости симметрии, проходящей через эти же точки и инкапсулированный ион железа(П). По данным РСА, инкапсулированный ион железа(П) в молекуле FeBd2(X-R(+)-PhCH(CH3)NHOCC6H4S)GmH) (ВР)2 находится в центре его FeN -координационного полиэдра с расстояниями Fe-N в диапазоне 1.8904(4) -1.9404(7) А. Этот полиэдр имеет геометрию, промежуточную между тригональной призмой и тригональной антипризмой с средним углом искажения ф равному 24.2°; его высота h составляет а средний хелатный

угол а приблизительно равен 78.2°. Терминальная PhCH(CH3)NH группа этой клатрохелатной молекулы равновероятно разупорядочена по двум положениям с противоположной ориентацией её метильного и фенильного заместителей; в кристалле обнаружено образование ^Н..^-связанных клатрохелатных димеров.

Ключевые слова: Макроциклы, клатрохелаты, клеточные комплексы, комплексы железа, реакционная способность лиганда.

Experimental

The reagents used, sorbents, organic bases and solvents were obtained commercially (Sigma-Aldrich®). The monocarboxyl-containing clathrochelate precursors FeBd2(X-HOOCC6H4S)GmH) (BF)2 (where Bd2- is a-benzyldioxime dianion, Gm is glyoxime residue, X is ortho- or meta-, or />ara-substituent) were prepared as described in.[4]

'H, 13C^H} and 2D NMR spectra were recorded from CD2Cl2 solutions with a Bruker Avance 600 spectrometer. The measurements were done using the residual signals of CD2Cl2: 'H 5.32 ppm (CDHCl2), 13C 54.00 ppm.

Analytical data (C, H, N contents) were obtained with a Carlo Erba model 1106 microanalyzer.

MALDI-TOF mass spectra of the monofunctionalized clath-rochelates were recorded with and without the matrix using a MALDI-TOF-MS Bruker Autoflex II (Bruker Daltonics) mass

spectrometer in reflecto-mol mode. The ionization was induced by UV-laser with wavelength 337 nm. The samples were applied to a nickel plate, 2,5-dihydroxybenzoic acid was used as the matrix. The accuracy of measurements was 0.1 %.

UV-Vis spectra of their solutions in dichloromethane were recorded in the range 230-800 nm with a Varian Cary 50 spectrophotometer. The individual Gaussian components of these spectra were calculated using the Fityk program.[5]

Synthesis

General procedure for preparation of the monoamide-termi-

nated clathrochelates FeBd2(X-R(+)-PhCH(CH)NHOCCflS)

GmH)(BF)2 (where X is ortho- or meta-, or para-substituent). The corresponding monocarboxyphenylsulfide clathrochelate FeBd2(X-HOOCC6H4S)GmH)(BF)2 (0.08 g, 0.1 mmol) was dissolved in dry DMSO (2 ml) under argon and a solution of CDI (0.033 g, 0.22 mmol) in DMSO (0.4 ml) was added under the intensive stirring. The reac-

tion mixture was stirred at 50 °C for 40 min, then it was cooled to 20 °C, degassed from CO2 impurities with argon and R(+)-1-phe-nylethylamine (0.036 g, 0.3 mmol) was added. The reaction mixture was stirred at r.t. for 1 h and precipitated with 2 % aqueous hydrochloric acid (25 ml). The precipitate was filtered off, washed with water and extracted with dichloromethane. The extract was precipitated with hexane, giving the crude product with a purity of approximately 90 %. This product was flash-chromatographically separated on silica gel (eluent: dichloromethane - iso-propanol 99:1 mixture) and three elutes were obtained. The second elute was collected and evaporated to dryness. The solid residue was extracted with dichloromethane and the extract was precipitated with hexane. The precipitate was filtered off, washed with hexane and dried in vacuo.

FeBd2 ((para-R (+)-PhCH(CH)NHOCC flJS)GmH)(BF) 2. Yield: 0.06 g (67 %). Found (%): C 57.66, H 3.74, N 10.33. Calculated for C45H35N7B2F2FeO7S (%): C 57.91, H 3.78, N 10.50. MS (MALDI-TOF) m/z (I, %): (positive range) 933 [M]+- (100), 956 [M+Na+]+ (60), 972 [M+K+]+ (85). UV-Vis (CH2Cl2) Xmax nm (e10-3, mol-1l cm-1): 240 (37), 263 (1.4), 283 (1.5), 292 (1.2) 305 (2.4), 350 (2.1), 451 (5.6), 474 (20). 1H NMR (CD2Cl2) SH ppm: 1.60 (d, 3H, CH3), 5.28 (m, 1H, CH), 6.47 (d, 1H, NH), 7.36 (m, 26H, Ph + HC=N), 7.80 (m, 2H, SAr), 7.89 (m, 2H, SAr). 13C{1H} NMR (CD2Cl2) 5 ppm: 22.31 (s, CH3), 50.19 (s, CH), 126.68, 127.96, 128.61, 129.23, 129.28, 129.58, 129.62, 130.82, 130.85, 131.05, 131.14, 135.86, 137.68 (all s, Ar + Ph), 143.83 (s, HC=N), 149.13 (s, SC=N), 156.92, 157.30 (two s, PhC=N), 165.57 (C=O).

FeBd2((meta-R(+)-PhCH(CH3)NHOCC6H p)GmH)(BF)2. Yield: 0.045 g (50 %). Found (%): C 57.65, H 3.63, N 10.30. Calculated for C45H35N7B2F2FeO7S (%): C 57.91, H 3.78, N 10.50. MS (MALDI-TOF) m/z (I, %): (positive range) 933 [M]+- (100), 956 [M+Na+]+ (20), 972 [M+K+]+ (50). UV-Vis (CH2Cl2) Xmax nm (e-10-3, mol-1l cm-1): 228 (35), 264 (1.8), 284 (2.2), 297 (1.7)x 362 (1.2), 452 (5.5), 474 (18). 1H NMR (CD2Cl2) 5H ppm: 1.59 (d, 3H, CH3), 5.27 (m, 1H, CH), 6.47 (d, 1H, NH), 7.34 (m, 26H, Ph + HC=N), 7.61 (m, 1H, SAr), 7.88 (m, 1H, SAr), 7.91 (m, 1H, SAr), 8.19 (s, 1H, SAr). 13C{1H} NMR (CD2Cl2) 5 ppm: 22.26 (s, CH3), 50.23 (s, CH), 126.72, 127.97, 128.07, 128.57, 129.22, 129.56, 129.60, 129.68, 130.77, 130.80, 131.03, 131.08, 131.13, 134.96, 137.38, 138.76, 143.55 (all s, Ar + Ph), 143.72 (s, HC=N), 149.53 (s, SC=N), 156.86, 157.25 (two s, PhC=N), 165.11 (C=O).

FeBd2((ortho-R(+)-PhCH(CH)NHOCC HS)GmH) (BF)2. Yield: 0.06 g (67 %). Found (%): C 57.81, H 3.67, N 10.30. Calculated for C45H35N7B2F2FeO7S (%): C 57.91, H 3.78, N 10.50. MS (MALDI-TOF) m/z (I, %): (positive range) 933 [M]+ (100), 956 [M+Na+]+ (25), 972 [M+K+]+ (50). UV-Vis (CH2Cl2) Xmax nm (e-10-3, mol-1l cm-1): 236 (43), 263 (1.9), 285 (2.6), 297 (1.9) 357 (1.9), 385 (0.8), 456 (8.8), 474 (24). 1H NMR (CD2Cl2) 5H ppm: 1.57 (d, J = 6.6 Hz, 3H, CH3), 5.26 (q, J = 6.8 Hz, 1H, CH), 6.33 (d, J = 7.5 Hz, 1H, NH), 7.36 (m, 25H), 7.43 (s, 1H, HC=N), 7.55 (t, J = 7.5 Hz, 1H, SAr), 7.58 (t, J = 7.6 Hz, 1H, SAr), 7.64 (d, J = 7.4 Hz, 1H, SAr), 7.75 (d, J = 7.5 Hz, 1H, SAr). 13C{1H} NMR (CD2Cl2) 5 ppm: 22.27 (s, CH3), 50.34 (s, CH), 125.77, 126.70, 128.02, 128.57, 129.29, 129.68, 130.75, 130.77, 131.10, 131.17, 131.68, 131.88, 137.35, 142.15, 143.49 (all s, Ar + Ph), 144.78 (s, HC=N), 149.46 (s, SC=N), 156.82, 157.23 (two s, PhC=N), 166.93 (C=O).

X-Ray Crystallography

Single crystals of the complex FeBd2((meta-R(+)-PhCH(CH3) NHOCC6H4S)GmH)(BF)2CH2Cl2 were grown from a dichloro-methane-benzene mixture at room temperature. The red block single crystal of C46H37B2Cl2F2FeN7O7S (M=1018.25) is triclinic; at 100.0(1) K: a=12.023(2)2 ¿=12.929(3), c=17.428(4) A, a=89.02(3), P=83.34(3), y=65.18(3)°, F=2440.8(10) A3, space group P-1, Z=2, Dcalcd=1.386 g- cm-3, ^=1.266 mm-1. The intensities of 25419 reflections were measured at BELOK beamline of the Kurchatov Synchrotron Radiation Source (Moscow, Russia) at a wavelength of 0.9699 A using a Rayonix SX-165 CCD detector and merged using

SCALA package.[6] The structure was solved by the direct method and refined by full-matrix least squares against F2. Non-hydrogen atoms were refined in anisotropic approximation except one nitrogen and two carbon atoms: PhCH(CH3)NH group is equiprobably disordered over two sites and non-hydrogen atoms of its CH(CH3) NH moiety were refined isotropically. Positions of the H(C) atoms were calculated. All hydrogen atoms were included in the refinement using the riding model with U.o(H)=nUq(X), where n = 1.5 for methyl groups and 1.2 for other atoms. The refinement converged to R1=0.1316 for 6726 observed reflections with />2a(T); wR2 and GOF were 0.3373 and 1.04 for 9918 independent reflections. Poor reflection ability of the X-rayed crystal did not allow us to solve the structure from the data obtained with laboratory sources, or to obtain the better convergence factors for the data obtained with synchrotron radiation. All calculations were made using the SHELXL-2015[7] and OLEX2[8] program packages. The residual density from one highly disordered solvent molecule was treated using SQUEEZE/PLATON program.[9]

CCDC 1587426 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www. ccdc.cam.ac.uk/conts/retrieving.html.

Results and Discussion

The monoamide-terminated cage complexes FeBd2(X-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2 were obtained by Scheme 1 using one-pot two-step synthetic procedure that includes (i) the reaction of its monocarboxyl-terminated clathrochelate precursor with CDI, giving the corresponding azaheterocyclic-terminated intermediate, and (ii) its cleavage with R(+)-phenylethylamine leading to the target iron(II) clathrochelate with terminal optically active amide group.

The complexes obtained were characterized using elemental analysis, MALDI-TOF mass-spectrometry, IR, UV-Vis, 1H and 13C{1H} NMR spectra, and by single crystal X-ray diffraction (for one of these clathrochelates). The most intensive peaks in the positive range of their MALDI-TOF mass spectra belong to the corresponding molecular ions.

1H, 13C{1H} and 2D NMR spectra, typical of the clathrochelates obtained, are shown in Figures 1-5. The number, position and integral intensities of the signals in their 1H NMR spectra confirmed the composition of the macrobicy-clic molecules. The number of the signals in their 13C NMR spectra suggests the absence of the C2 symmetry axes passing through the middles of the chelate C-C bonds and of the symmetry plane also passing through these points and the encapsulated iron(II) ion as well.

Molecular structure of the complex FeBd2((meta-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2 is shown in Figure 6; main geometrical parameters of its clathrochelate framework, as well as those of three fluoroboron-capped monofunctionalized sulfide iron(II) clathrochelates with known X-ray structures,[21011] are listed in Table 1. In all their molecules, the encapsulated iron(II) ion is situated in the centre of its Fe^-coordination polyhedron with Fe-N distances falling in the range 1.8904(4)-1.9404(7) Â. Such coordination polyhedron of the complex FeBd2((meta-R(+^)-PhCH(CH3) NHOCC6H4S)GmH)(BF)2 possesses the geometry intermediate between a TP and a TAP with the average distortion angle ф of 24.2°. This value is very similar to those for its above monofunctionaluzed clathrochelate analogs possesing ф from 23.6 to 25.8°. Other geometrical parameters of their clathrochelate frameworks are also very similar: the heights

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SrJ I SrJ

7.2

6.2

5.2

4.2

3.2

2.2

Figure 1. 1H NMR spectrum of the clathrochelate FeBd2((ortho-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2.

8'H (ppm)

COCNCOCOOTIO IfltOtOtDOlDSOiSWOS

co CN

lOlOtttttttt COCOCOCOCOCOCNCNICNICNCNICNI

S^ ^ I S

170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20

813c (ppm)

Figure 2. 13C{1H} NMR spectrum of the clathrochelate FeBd2((ortho-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2.

J

A.

5I3C (ppm)

- 5.5

5.0

- 6.5

- 7.0

- 7.5

7.3

S'h (ppm)

Figure 3. 'H - 'H COSY NMR spectrum of the complex FeBd2((ortho-R(+>PhCH(CH3)NHOCC6H4S)GmH)(BF)

813c (ppm)

- 125

- 130

- 135

- 140 150 155

|- 160 165 170

1.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0

S'h (ppm)

Figure 4. 'H - 13C HMQC NMR spectrum of the complex FeBd2((ortho-R(+>PhCH(CH3)NHOCC6H4S)GmH)(BF).

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• "в

«

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813с (ppm)

- 125

- 130

- 135

- 140 150 155

- 160

- 165

- 170

8.5 8.0 7.5 7.0 6.5 6.0

5.5 5.0

5'н (ppm)

Figure 5. 'H - 13C HMBC NMR spectrum of the clathrochelate FeBd2((orfho-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2.

Figure 6. General view of the molecule FeBd2((meta-R(+)-PhCH(CH3)NHOCC6H4S)GmH)(BF)2.

Figure 7. Formation of H-bonded clathrochelate dimer in the crystal FeBd2((raefa-^+>PhCH(CH3)NHOCC6H4S)GmH) (BF)2CH2Cl2; the corresponding hydrogen bonds are shown with dashed line. The H(C) atoms are omitted for clarity.

h of the FeN.-polyhedra (2.33-2.40 Â) and the bite (chelate) angles a (78.2-78.8°) are characteristic of the fluoroboron-capped iron(II) clathrochelates.[1,2]

The terminal PhCH(CH3)NH group of the molecule FeBd2((weta-R(+;-PhCH(CH3)NHOCC6H4S)GmH)(BF)2 in the above X-rayed crystal is equiprobably disordered over two sites with opposite orientation of its methyl and phenyl groups. Nevertheless, this disorder does not prevent a formation of the corresponding N-H...F-bonded clathrochelate dimers (Figure 7) through the hydrogen bonding between the terminal amide moiety of the single functionalizing ribbed substituent of one of these

macrobicyclic molecules and the fluorine apical substituent at a clathrochelate framework of the second molecule of this type on the distance r(N...F)=3.0421(8) Â with ZN...H... F=150.4°. Other intermolecular interactions in this crystal include the halogen tonds and weak H^onding C-H...O and C-H... F interactions.

Because the chromophoric FeN6-centers of the ofoained macroMcyclic iron(II) tris-dioximates, the constitutional isomers, are almost the same, their solution UV-Vis spectra in the visiWe range are very similar. Their decomposition on the Gaussian components gave a more intensive (e-2-104 mol'Lcm-1) Ъ)М with maximum at approximately

Table 1. Main geometrical parameters of a macrobicyclic cage framework in the fluoroboron-capped monofunctionalized iron(II) clathrochelates.

Parameter FeBd2((meta-R(+)-PhCH(CH3) NHOCC6H4S)GmH)(BF)2 FeBd2((CH3S)GmH(BF)2[12] FeBd2((HSCH2CH2S)GmH)(BF)2[10] FeBd2(PlSGmH)(BF)2 a[11]

Fe - N ( A ) 1.8904(4) - 1.9404(7) av. 1.926 1.900(3) - 1.916(3) av. 1.908 1.891(4) - 1.912(4) av. 1.899 1.907(4) - 1.926(4) av. 1.912

B - O (A) 1.4789(4) - 1.5115(5) av. 1.494 1.475(5) - 1.516(4) av. 1.491 1.465(5) - 1.495(5) av. 1.481 1.492(5) - 1.518(5) av. 1.508

N - O (A) 1.3697(3) - 1.4121(4) av. 1.383 1.363(5) - 1.382(5) av. 1.372 1.366(6) - 1.378(5) av. 1.371 1.352(4) - 1.376(4) av. 1.366

C=N (A) 1.3078(4) - 1.3268(6) av. 1.315 1.312(3) - 1.339(4) av. 1.323 1.284(5) - 1.321(6) av. 1.310 1.301(5) - 1.321(5) av. 1.312

C - C (A) 1.4410(4) - 1.4773(4) av. 1.457 1.436(6) - 1.454(6) av. 1.444 1.418(7) - 1.466(6) av. 1.448 1.412(6) - 1.461(6) av. 1.439

N=C-C=N (°) 8.022(4) - 9.786(5) av. 8.9 5.3(4) - 9.8(5) av. 8.1 5.6(6) - 12.5(6) av. 9.0 7.9(6)-11.6(6) av. 9.6

j (°) 24.2 24.7 25.3 23.9

« (°) 78.2 78.8 78.8 78.2

h(A) 2.34 2.33 2.40 2.33

475 nm and a less intensive (e~(5-9)-103 mol-1-l-cm-1) band at approximately 450 nm assigned to the metal-to-ligand Fed^Lp* charge transfer. The bands in the UV range of these spectra were assigned to p-p* transitions in the a-benzildioximate chelate fragments of their macrobicyclic ligands, and to those of the same nature in the arylsulfide ribbed moiety and in the terminal R(+)-1-phenylethylamine group as well.

Conclusions

Thus, for the first time, we prepared the iron(II) cage complexes with terminal optically active group and characterized them using various spectral techniques and by single crystal X-ray diffraction. These clathrochelates can be regarded as prospective chiroptical CD-active probes for protein structures (in particular, for sensing of their conformational changes).

Acknowledgements. The synthesis of cage complexes was supported by the Russian Science Foundation (grant 1613-10475). The spectral characterizations were performed with a financial support of the EU Research and Innovation Staff Exchange (RISE) (H2020-MSCA-RISE-2017, Project 778245 'CLATHROPROBES'). XRD experiment was performed at the unique scientific facility Kurchatov Synchrotron Radiation Source supported by the Ministry of Education and Science of the Russian Federation (project code RFMEFI61917X0007). Y.Z.V. and A.S.B. thank RFBR (grants 15-03-07509 and 17-03-00587) for the financial support. The contribution of the Center for molecule composi-

tion studies of INEOS RAS is also gratefully acknowledged.

MALDI-TOF mass spectrometric measurements were performed using an equipment of CKP FMI IPCE RAS.

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Received 22.11.2017 Accepted 10.12.2017