Coordination Complexes

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Co-Crystallization of Achiral Components into Chiral Network by Supramolecular Interactions: Coordination Complexes - Organic Radical Yan-Li Gao, Kseniya Yu. Maryunina, Sayaka Hatano, Sadafumi Nishihara, Katsuya Inoue, and Mohamedally Kurmoo Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b00847 • Publication Date (Web): 01 Aug 2017 Downloaded from http://pubs.acs.org on August 5, 2017

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Crystal Growth & Design

Co-Crystallization of Achiral Components into Chiral Network by Supramolecular Interactions: Coordination Complexes - Organic Radical Yan-Li Gao,† Kseniya Yu Maryunina,† Sayaka, Hatano,† Sadafumi Nishihara,† Katsuya Inoue,†,‡,* Mohamedally Kurmoo‡,£,* †

Department of Chemistry, Hiroshima University, 1-3-1, Kagamiyama, HigashiHiroshima, Hiroshima 739-8526, Japan.

‡

Center for Chiral Science, Hiroshima University, 1-3-1, Kagamiyama, HigashiHiroshima, Hiroshima 739-8526, Japan.

£

Institut de Chimie de Strasbourg, CNRS-UMR7177, Université de Strasbourg, 4 rue Blaise Pascal, 67070 Strasbourg, France.

KEYWORDS Co-crystallization, Organic Radical, Chiral, Achiral, Magnetic Properties

ACS Paragon Plus Environment

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ABSTRACT

Co-crystallization is an important aspect of crystal engineering that has found major applications in the development and manufacture of pharmaceutical drugs but is rarely invoked in the development of magnetic materials. Co-crystals have been serendipitously obtained instead of the usual coordination polymers from the organic radical, 2,2-pentamethylene-4,4,5,5tetramethylimidazolidine-l-oxyl, and coordination complexes, cis-MII(hfac)2(H2O)2, where M = Co or Mn and hfac = hexafluoroacetylacetonato,. The extensive intramolecular H-bond is the cause for the segregation of the two entities but the supramolecular interactions between these two neutral building blocks resulted in a rare chiral co-crystal system. The directional properties of the supramolecular interactions, N-O···OH2, N-H···OH2, N-O···CH3, N-O···CH2, F···CH3, F···CH2, have been identified as working in tandem to generate the chirality from achiral components in achiral solvents. The absence of charge or proton transfer as suggested by X-ray structural analyses (bond lengths and angles), values of the magnetic moments and lack of magnetic exchange between the metal spin and that of the organic radical are characteristics to define these two solids as genuine co-crystals. We therefore proposed that these solids be more effective as biomarkers than the pure radical. A comparison of their properties to related radicals is provided.


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INTRODUCTION Among the numerous success stories in the field of molecular magnetism, the concept of using paramagnetic metals and organic radicals remains a key approach in the synthesis and design of magnets.1-6 This is because it has been proven in (a) enhancing the critical ordering temperatures from the average low limit of 2 K for purely organic radicals to several tens of Kelvin,7-9 (b) bringing the moment carriers closer to each other through metal-nitroxide bonds,10-12 (c) producing different structural and magnetic dimensionalities and in particular, giving rise to the realization of single-chain-magnetism formerly predicted in the theory of Glauber,13-15 (d) allowing the introduction of other properties into real magnets, for example one which is close to our own work is chirality,16-20 and (e) introducing magnetic anisotropy of the metals into the magnetic organic systems.21-23 These advances have had major impact in the field and is now a fast developing area of research.24 We have been involved in this area from its very first conception to now and in particular we have focused on the introduction of chirality in the search for new physics combining structural chirality with magnetic ordering in a number of different systems.17-20, 25-27 The use of radicals is an integral part of this research activity and numerous mono-, bi- and tri-radicals of varying stereochemistry have been employed in the designs for controlling the dimensionality for example. In general, polymeric coordination compounds are obtained whereby the organic ligands act as bridges between paramagnetic coordination building blocks.28,29 The radicals have sp2-C spaced imino-nitroxide and nitronyl-nitroxide. However, C(sp3)-spaced bi-radicals of the type dinitroxide imidazolidine have not been explored even though the C(sp3)-coupled nitroxide moieties can have major chemical influence on the bonding of the nitroxide oxygen atoms as well as the packing because of the important steric hindrance due to the proximity of large


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groups.30 We have therefore reproduced the three radicals, reported by Keana et al., which were obtained from the oxidation of 2,2,4,4,5,5-hexasubstituted imidazolidines and study their crystal chemistry and in particular, their reaction with metal complexes (Scheme 1). Following a full study of the structures and magnetism of the radicals and their binary metal-radical compounds, it was surprising to note that the latter compounds were not polymeric or cluster but more interestingly 2:1 radical:metal complex co-crystals.31-34 Further analyses reveal that considerable intra- and inter-molecular interactions existed within the structures of the purely organic radicals and their complexes.35

Scheme 1. Molecular building blocks used: (top) organic radicals 1, 2, and 3 and (bottom) inorganic complexes, cis-MII(hfac)2(H2O)2, M = Co and Mn. The unexpected co-crystallization of these entities is derived from the several Coulombic forces that exist within the structures. The co-crystallization process in this case is accompanied by the rare formation of a chiral crystal system from achiral components in a mixture of achiral solvents.36,37 Thus the results can be of major interest for the pharmaceutical industries where the


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information can be of used in the realization of active chiral drugs. Although, the field of cocrystallization has found major application in drug manufacturing obtaining chiral drugs has been rarely reported.38-42 Here we report the syntheses, crystal structures and magnetic properties of the organic radicals and their co-crystals with cis-MII(hfac)2(H2O)2, where M = Co or Mn and hfac = hexafluoroacetylacetonate. We provide a full account of the structures because the co-crystals were found to be chiral and are assembled from achiral components, revealing the importance of supramolecular interactions, involving H2O···ON, H2O···HN, CF3···CH3 and CF3···CH2 which drive the formation of such 3D chiral crystals.

EXPERIMENTAL SECTION Materials. All reagents were obtained from commercial sources and used as received. Crystal Structure Determinations. The X-ray diffraction intensities were collected for selected single crystals using Bruker diffractometers−SMART-APEX II with a CCD and D8QUEST with a CMOS area detector. Both employed graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Data reduction were made using SAINT and intensities were corrected for absorption by SADABS.43,44 The structures were solved by direct methods using SHELXS-97 and refined by full-matrix least-squares against F2 using SHELXL.45-46 Hydrogen atoms were located from difference Fourier maps for all the compounds. The crystals and refinements data are summarized in table 1. Further details can be obtained from the cif files deposited at the Cambridge Crystallographic Data Centre and can be obtained free of charge on request via http://www.ccdc.cam.ac.uk/data_request/cif. The CCDC reference numbers are 1557048 1557054.


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General Characterizations. Infrared spectra were recorded on a JASCO FT/IR-660 PLUS by transmission through KBr pellets in the range 400−4000 cm−1. X-band (∼9 GHz) EPR spectra were recorded using a Bruker ELEXSYS E500 equipped with a continuous flow cryostat operating in the temperature range 3.5 to 300 K. The magnetization measurements on the crystalline solids were carried out using Quantum Design MPMS-5S and MPMS-2 SQUID magnetometers. The magnetic field can be varied from –50 to 50 kOe and the temperature in the range 2−300 K. The data were corrected for the sample diamagnetism using Pascal’s constants.46 Syntheses of organic radicals. The syntheses reported by Keana et al. were reproduced with only

little

modifications.30

The

mono-radical

2,2-pentamethylene-4,4,5,5-

tetramethylimidazolidine-l-oxyl (1) was first synthesized and purified by recrystallization and then

transformed

to

the

mono-radical

l-hydroxy-2,2-pentamethylene-4,4,5,5-

tetramethylimidazolidine-oxyl (2). The orange crystals of 1 and 2 were recrystallized from hexane. 2 was further oxidized with O2 in tBuOH - 0.11M tBuOK to the biradical 2,2pentamethylene-4,4,5,5-tetramethylimidazolidine-1,3-dioxyl (3). The crude orange dinitroxide radical was purified by recrystallization from pentane at low temperature. HRESI-MS for 1: m/z = 212.18823 (calc. for C12H23N2O+H+ = 212.18831). HRESI-MS for 3: m/z = 227.17531 (calc. for C12H23N2O2+H+ = 227.17540). Syntheses of [12•M(hfac)2(H2O)2] (1.Co, M = Co and 1.Mn, M = Mn). 1 (1 mmol) in 2 mL of CH2Cl2 was added to a stirred solution of cis-MII(hfac)2(H2O)2 (1 mmol) in 20 mL of hot nhexane. The solution was refluxed for 15 minutes, filtered and kept in air at room temperature. After several days, cubic-shaped light orange crystals of 1.Mn and red-brown crystals of 1.Co were obtained in ca. 55% yield.


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HRESI-MS: m/z = 212.18823 (1.Mn), 212.18825 (1.Co), calc. 212.18831 for C12H23N2O+H+; m/z = 423.36951 (1.Mn and 1.Co), calc. 423.3772 for 2(C12H23N2O)+H+; m/z = 473.10695 (1.Mn), 477.10187 (1.Co), calc. 473.10716 (1.Mn), 477.10231 (1.Co), correspond to M(C5HF6O2)(C12H23N2O)+H+; m/z = 711.97156 (1.Mn), 715.96674 (1.Co), calc. 711.97102 (1.Mn), 715.96617 (1.Co) for M(C5HF6O2)3(NH4)2+.

RESULTS AND DISCUSSION Table 1. Crystallographic data of the organic radicals and co-crystals at 296 K. 3

1.Co

1.Mn

1

2

formula

C12H23N2O

C12H22N2O2 C24H44N4O4 C17H26Co0.5F6N2O4 C17H26Mn0.5F6N2O4

fw

211.32

227.32

452.63

465.86

463.87

cryst syst Orthorhombic Monoclinic

Triclinic

Rhombohedral

Rhombohedral

space group

P bca

P 21/c

P -1

P 3121

P 3121

a (Å)

9.051(1)

8.613(1)

6.519(1)

16.585(3)

16.689(1)

b (Å)

11.059(1)

13.446 (1)

14.343(1)

16.585(3)

16.689(1)

c (Å)

24.838(1)

11.976(1)

14.707(1)

13.565(3)

13.602(1)

α (˚)

90.00

90.00

74.27 (1)

90.00

90.00

β (˚)

90.00

107.54 (1)

81.64 (1)

90.00

90.00

γ (˚)

90.00

90.00

83.87(1)

120.00

120.00

V (Å3)

2486.2(2)

1322.5(2)

1306.2(1)

3231.2(1)

3280.8(5)

Z

8

4

2

6

6

Refls. Total

37293

8712

33325

17499

49508

Unique

3082

2289

6477

5342

5445

Param.

140

152

297

327

327


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Rint

0.0253

0.0357

0.0369

0.0448

0.0485

R1/wR2

0.0568

0.0599

0.0648

0.0585

0.0519

[I>2σ(I)] 0.1652

0.1604

0.1620

0.1361

0.1274

R1/wR2

0.0665

0.0775

0.0965

0.1139

0.0878

(all data)

0.1756

0.1734

0.1817

0.1573

0.1445

GoF

1.097

1.056

1.022

1.023

1.027

1 Figure

1.

Structures

2 of

the

tetramethylimidazolidine-l-oxyl),

molecular 2

3 entities

of

1

(2,2-pentamethylene-4,4,5,5-

(l-hydroxy-2,2-pentamethylene-4,4,5,5-

tetramethylimidazolidine-oxyl) and 3 (2,2-pentamethylene-4,4,5,5-tetramethylimidazolidine 1,3-dioxyl). Crystal Structure of 1. As expected and from the reported crystal structure of 3 the five membered ring containing the N-O• radical is almost orthogonal to the boat conformed cyclohexane because of the sp3-C at the joint (Figure 1).30 Furthermore, the saturated ring of three carbon and two nitrogen atoms of the imidazolidine is non-planar. The carbon tetrahedron is slightly strained from being regular due to the short distances of the two bonded nitrogen atoms imposed by the ethane bridge where the N-C-N tetrahedral angle is reduced to 102.3° compared to the range of the other three angles 109.3-112.5°. The slight asymmetry of CH2-C-N angles is associated with the H-bond, N-O···CH2(hexane). The removal of an anti-bonding


8

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electron to form the radical led to a short N2-O1 bond length of 1.270 Å. Several intra- and one inter-molecular H-bonds are present in this molecule and within its packing (Figure 2). The oxygen atom interacts with the methyl hydrogen atoms (O···CH3 = 2.847 and 3.090 Å) and with the cyclohexane (O···CH2 = 2.943 and 3.032 Å). H-bond between the N-H···O-N (3.198 Å) produces a regular one-dimensional S = ½ magnetic chain along the b-axis.

(a)

(b)

Figure 2. Structure of 1 highlighting the intra- (dashed red) and inter-molecular (dashed black) H-bonds (a) within the molecules and (b) that in the formation of the chain along the b-axis. Crystal Structure of 2. Apart from the replacement of the N-H by N-OH the structural characteristics of 2 is similar to those of 1 (Figure 1). The sp3-C has an N-C-N angle of 99.8° reduced from a normal tetrahedral angle and three normal ones (109.0-110.5°). The imidazolidine is non-planar. The notable point is the difference of the N-O bond lengths for the N-Oxyl (1.275 Å) and the N-hydroxyl (1.437 Å). The arrangement of the molecules within 2 is also similar to that of 1, leading to two divergent groups involved in H-bond (O···HO = 2.772 Å) to give regular one-dimensional S = ½ magnetic chains along the c-axis (Figure 3). In contrast to 1, there are twice as many C···O interactions within the molecule which are in pairs {O···CH3 = [2.852, 3.081], [2.745, 3.033] Å and O···CH2(hexane) = [2.770, 3.349] and [2.893, 2.987] Å. In


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addition there are two slightly longer intermolecular O···CH2(hexane) interactions (3.409 and 3.492 Å) which bridge the chains into layers (Figure S1).

(a)

(b)

Figure 3. Structure of 2 highlighting the H-bonds (a) within the molecules (dashed red) and (b) that (dashed black) in the formation of the chain along the c-axis. Crystal Structure of 3. The structure of 3 is similar to that reported, so we will give information that have not been mentioned before but relevant to the present work.30 The absence of any hydrogen atoms associated with the imidazolidine nitrogen atoms prevents the formation of H-bonded chains (Figure 1). Therefore the molecules appear completely isolated. Since both N-Oxyl are radicals the bond lengths (1.259-1.267 Å) are very similar to each other and for the pair of independent molecules with the unit cell. Within the molecules the O···CH3 interactions range is 2.801-3.130 Å and for the O···CH2(hexane) it is 2.935-3.114 Å. The key feature of the packing arrangement is the near orthogonal alignment of the N-O bonds of the two crystallographically independent molecules (Figure 4).


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Figure 4. Structure of 3 highlighting the H-bonds (dashed red) within the molecules. Crystal Structures of 1.Co and 1.Mn. The two compounds, 1.Co and 1.Mn, have the same structure but with slight differences associated with the different ionic radii of the metals (Figure 5). Therefore we will focus on 1.Co for the description and highlight the difference where appropriate. The key feature is the formation of a chiral crystal system, space group P 3121, from purely achiral components dissolved in achiral solvents. There are two neutral radicals per metal complex that are packed effectively within the unit cell. The asymmetric unit consists of half of the coordination complex and one radical (Z = 6). The Co(hfac)2(H2O)2 retains the cisconfiguration so that the complex has a strong dipolar field with a high concentration of fluorine at one end and the two water molecule at the other.47,48 For the radical intramolecular interactions of the N-oxyl with the methyl and hexane (N-O···CH3 = 2.849 and 2.998 Å; N-O···CH2 = 2.910 and 3.060 Å) are observed. Due to the strong H-bonds between the radical and the water molecule, N-O···OH2 (2.695 Å) and N-H···OH2 (2.878 Å), the radicals are aligned to the one side of the complex. On the other side the fluorine atoms interact with the methyl and hexane (F···CH3 = 3.338 Å; F···CH2 = 3.316 Å, Figure S2). The links between the Co(hfac)2(H2O)2 and radicals result in the formation of helices along the c-axis which are responsible for the generation a chiral crystal system. The packing arrangement is most unexpected and contrary to our aim to synthesize metal-radical networks. The reason for this failure appears to be due to the


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presence of considerable intramolecular H-bonding that also provides steric hindrance around the coordinating oxygen atoms preventing the propagation needed for network formation. The unit cell contracts by ca. 3% on lowering the temperature from 296 to 173 K but very little difference in the packing arrangement (Table S1).

(a)

(b)

Figure 5. View of the structure of 1.Co showing (a) the intramolecular O···O (dashed black) and O···N (dashed blue) H-bonds (left) and (b) the packing of 1.Co in the unit cell (right). The chirality of the structure in the P 3121 space group can be seen both in the ab-plane and along the c-axis but is most pronounced along the latter (Figure 6). Representing the sublattices by the metal atoms and by the N and O atoms with their bond as another, the pitch can be seen to be a unit cell along the c-axis. As mentioned above, the supramolecular interactions N-O···OH2, N-H···OH2, N-O···CH3, N-O···CH2, F···CH3, and F···CH2 work in tandem to generate the chirality.


12

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Figure 6. View of the chirality of the structure of 1.Co displaying the helical sublattices represented by the Co atoms and the N-O moiety of the radical. It is important to note that the distances and angles found in this co-crystal are close to those in the independent crystal structures of the radical and Co(hfac)2(H2O)2 suggesting there is no charge or proton transfer. Although the positions of hydrogen atoms X-ray diffraction are normally not so precise, in the present case we have located all the hydrogen atoms in each of the complexes from difference Fourier maps. These characteristics are signature of genuine cocrystals.49,50 Infrared

Spectroscopy.

Because

the

molecules

contain

the

common

fragments,

tetramethylethane and cyclohexanyl, the infrared spectra have common bands though their intensities and multiplicity depend on the crystal symmetries (Figures 7a and S3). This is clearly seen for the numerous C-H vibrations in the range 2800-3100 cm-1. But they differ in the central part containing the nitroxide radical. The imidazolidine-monooxyl has a hydrogen on the nitrogen atom resulting in a sharp ν(N-H) band at 3292 cm-1 and a bending mode at 812 cm-1. The dinitroxide has no hydrogen associated with it and is therefore IR silent in this region. In contrast, the imidazolidine with the hydroxylamine displays two peaks at 3342 and 3400 cm-1,


13


associated with the symmetric and antisymmetric vibrations, respectively, and an overlapped pair of bands centered at 670 cm-1 due to bending modes involving the hydrogen atoms (Figure S3). 1

2

Co-hfac Intensity (arb. units)

1

Intensity (arb. units)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Mn-hfac 1.Co 1.Mn

3

26

28

30

32

34

36 38 40

2

-1

Wavenumber (10 cm )

26

28

30

32

34

36 2

38

40

-1

Wavenumber (10 cm )

(a)

(b)

Figure 7. Infrared spectra of the (a) radicals 1, 2, and 3 and (b) cis-M(hfac)2(H2O)2 and cocrystals 1.Co and 1.Mn. The spectra were recorded for a fixed concentration of compound in solid KBr and plotted without any normalization but offset from each other for clarity. For the co-crystals (Figure 7b) there are additional bands corresponding to the different components, for example the water stretching vibration centered at 3390 – 3400 cm-1 and a shoulder at higher frequencies as well as the bending modes centered at 1650 cm-1. The CF3 groups contribute to a range of peaks for their stretching modes (1450-1600 cm-1), bending modes (1100-1300 cm-1) and three torsion modes at 585, 670 and 790 cm-1. The peaks are slightly shifted to the low energy side from 1.Co to 1.Mn due to the slight difference in the metal masses. The spectrum of the radical is overlaid on top with slightly different frequencies but noticeably lower intensities than those of the M(hfac)2(H2O)2 vibrational modes. For example, the ν(N-H) band at 3292 cm-1 is shifted to 3312 cm-1 (1.Co) and 3304 cm-1 (1.Mn).


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The observed superposition of the two spectra of the components forming the co-crystals is clear indication of the negligible proton transfer and absence of ionization. Thus, these two solids are co-crystals in the true and absolute sense given by the definition.49,50 Magnetic Properties. The magnetic susceptibilities of the organic radicals and the co-crystals were measured on polycrystalline samples in an applied field of 5 kOe and the data were corrected for the diamagnetism of the contents.51 The temperature dependence of the susceptibility suggests paramagnetic behavior with weak coupling between the nearest neighbors. Considering the one-dimensional H-bonded chain structure of equally spaced moment carriers of S = ½ for 1 and 2, we fitted the data using the Bonner-Fisher relation (Figure 8).52 The fits were of good quality in each case with antiferromagnetic coupling of slightly different magnitudes, g = 2.066(2) and J = –2.24(1) K for 1 and g = 1.999(2) and J = –4.61(1) K for 2. Surprisingly, the exchange is stronger for the long N-O···HO-N connection than for the short NO···H-N. This suggests that the angular overlap may be the key to the difference rather than the distance.53 The ESR spectrum of the monoradical (1) is characterized by three lines suggesting a slight anisotropy, gxy = 2.0035 and gz = 2.002 (Figure S4). 0.10

0.8

1 2

1

0.08

0.6

2

0.04

3 B

3

M (Nµ )

0.06

3

χ (cm / mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.4

0.2

0.02

0.0

0.00 1

10

100

0

10

Temperature (K)

(a)

20

30

40

50

Field (kOe)

(b)


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Figure 8. Temperature dependence of the (a) magnetic susceptibilities and (b) isothermal magnetizations of 1 and 2 and 3. The solid lines for the susceptibilities are the theoretical fits to the experimental data (see text for details). The magnetic susceptibility of the biradical (3) is surprisingly more complex due to an anomaly centered around 20 K (Figure 8). Since the biradical is isolated from each other we only need to consider the coupling of the two spin carriers across the sp3-C within each crystallographically independent molecule. Since there are two independent radical dimers per unit cell, the data were fitted to the Bleaney-Bowers equation for two pairs, in the whole temperature regimes assuming they have different gaps, giving a large gap (∆ = 2J = 49.2(5) K) and a small gap (∆ = 8.53(4) K).54 The considerable difference indicates the strong dependence of the magnetic exchange interaction on the subtle change in geometry within each radical. As theoretically expected application of high field should populate the triplet state and the susceptibility will be enhanced below the maximum but should be independent of field at higher temperatures (Figure S5). In addition isothermal magnetization well below the maximum will have the signature of a gap but this will slowly lead to a linear field-dependence paramagnetic behavior as the sample temperature is increased (Figure S6). The ESR spectra of the solution in 2-methyl tetrahydrofuran, recorded as a function of temperature, are very similar to those reported by Keana et al. and the resolution is improved marginally at very low temperature to allow hyperfine splitting of the ms = 2 resonance.30 Although the pattern of the spectra already indicates coupling of the two radicals within the molecule, the temperature dependence of the intensity suggests the coupling is fairly weak in comparison to that estimated for the solid.


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5

1.2

0.6

1.Co

1.Mn

1.Mn

2

0.4 1

0.2 0.0

0 0

100 200 Temperature (K)

300

5.0 B

1.Co

3

M (Nµ )

0.8

3

3

6.0

4

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7.0

χT (cm K / mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4.0 3.0 1.Co 2.0 1.Mn

1.0 0.0 0

(a)

10

20

30

40

50

Field (kOe)

(b)

Figure 9. (a) Temperature dependence of χ and χT and (b) isothermal magnetization at 2 K for 1.Co and 1.Mn. The temperature dependence of χ and χT for the co-crystals (Figure 9) suggests very weak exchange interaction between the moment carriers. Curie-Weiss fit of the data (50-300 K) for 1.Mn gives a Curie constant of 5.036(5) cm3 K mol-1 and Weiss constant of –3.4(2) K. The Curie constant is consistent with the sum of one Mn (4.375 cm3 K mol-1) and two radicals (2 × 0.375 cm3 K mol-1) assuming g = 2 in each case.55 The weak interaction is reasonable for mediation through H-bond with the coordinated water molecule. Similar analysis for 1.Co between 100 and 300 K gives C = 3.864(4) cm3 K mol-1 and θ = –12.0(3) K. The Curie constant is again consistent to the sum of the individual carriers and considering the orbital contribution in the case of the Co(II). However, the Weiss constant of –12.0 K reflects the effects of both exchange and spinorbit for Co(II).6,55 It is generally difficult to separate the two from susceptibility measurements. Isothermal magnetizations at 2 K for the two compounds behave as a sum of the Brillouin functions for moments of the building units. The saturation value (6.8 NµB) for 1.Mn is close to


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that expected (7 NµB) whereas 3.9 NµB is slightly lower than expected (4.3 NµB) for 1.Co (Figure 9). CONCLUSION Attempt to synthesize magnetic coordination polymers from the organic radical, 2,2pentamethylene-4,4,5,5-tetramethylimidazolidine-l-oxyl with coordination complexes, cisMII(hfac)2(H2O)2, M = Co or Mn, resulted unexpectedly to a pair of co-crystals. These cocrystals turn out to be chiral while the building components are both achiral as are the solvents used. The X-ray structures of the component radical and the co-crystals reveal an extensive set of supramolecular interactions, N-O···OH2, N-H···OH2, N-O···CH3, N-O···CH2, F···CH3, F···CH2, working in tandem to generate the chirality. From X-ray structural analyses, infrared spectroscopy and magnetization data it is evident that these supramolecular interactions have very little electronic influence to induce charge or proton transfer and magnetic coupling, allowing one to describe these solids as genuine co-crystals. It is important to highlight that chiral co-crystals are rather rare and the realization of chiral crystalline form from achiral components can be very beneficial for the pharmaceutical industries.

ASSOCIATED CONTENT Supporting Information. List of crystallographic data, figures of structures, figures of IR, EPR and magnetic data. The following files are available free of charge. brief description (file type, i.e., PDF)

AUTHOR INFORMATION


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Corresponding Author * Dr Mohamedally Kurmoo: [email protected] * Prof. Katsuya Inoue: [email protected] Author Contributions YLG performed all the experiments as part of her PhD under the guidance of KI and MK. SH and YLG performed the ESR measurements. The data were analyzed by YLG, KI and MK. The manuscript was written by MK and verified by YLG and KI. KYM, SH and SN were involved in discussions and read and approved the content. Funding Sources Grant-in-Aid for Scientific Research (S) (No. 25220803) "Toward a New Class Magnetism by Chemically-controlled Chirality", Chirality Research Center (CResCent) in Hiroshima University (MEXT program for promoting the enhancement of research universities, Japan) and JSPS Core-to-Core Program, A. Advanced Research Networks. ACKNOWLEDGMENT This work was supported by a Grant-in-Aid for Scientific Research (S) (No. 25220803) "Toward a New Class Magnetism by Chemically-controlled Chirality", Chirality Research Center (CResCent) in Hiroshima University (the MEXT program for promoting the enhancement of research universities, Japan) and JSPS Core-to-Core Program, A. Advanced Research Networks. MK is supported by the CNRS (France). ABBREVIATIONS


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1, 2,2-pentamethylene-4,4,5,5- tetramethylimidazolidine-l-oxyl; 2, l-hydroxy-2,2pentamethylene-4,4,5,5- tetramethylimidazolidine-oxyl; 3, 2,2-pentamethylene-4,4,5,5tetramethylimidazolidine-1,3-dioxyl; 1.Co, (1)2.CoII(hfac)2(H2O)2; 1.Mn, (1)2.MnII(hfac)2(H2O)2. REFERENCES 1. Itoh, K.; Kinoshita, M. (Eds.), Molecular Magnetism, New Magnetic Materials, Gordon Breach-Kodansha:Tokyo, 2000. 2. Blundell, S. J.; Pratt, F. L. J. Phys.: Condens. Matter, 2004, 16, R771-R828. 3. Gatteschi, D.; Sessoli, R.; Villain, J. Molecular Nanomagnets, Oxford University Press: Oxford, UK, 2006 4. Sorace, L.; Benelli, C.; Gatteschi, D. Chem. Soc. Rev., 2011, 40, 3092-3104. 5. Gutlich, P.; Garcia, Y.; Goodwin, H. A. Chem. Soc. Rev., 2000, 29, 419-427. 6. Kurmoo, M. Chem. Soc. Rev., 2009, 38, 1353-1379. 7. Lahti, P. M. (Ed.), Magnetic Properties of Organic Materials; Marcel Dekker: New York, 1999. 8. Inoue, K.; Hayamizu, T.; Iwamura, H.; Hashizume, D.; Ohashi, Y. J. Am. Chem. Soc., 1996, 118, 1803–1804. 9. Goss, K.; Gatteschi, D.; Bogani, L. Phys.Chem.Chem.Phys., 2014, 16, 18076-18082. 10. Luneau, D.; Rey, P. Coord. Chem. Rev., 2005, 249, 2591-2611.


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Page 21 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11. Inoue, K.; Iwahori, F.; Markosyan, A. S.; Iwamura, H. Coord. Chem. Rev., 2000, 198, 219229. 12. Stumpf, H. O.; Ouahab, L.; Pei, Y.; Grandjean, D.; Kahn, O. Science, 1993, 261, 447-449. 13. Clérac, R.; Miyasaka, H.; Yamashita, M.; Coulon, C. J. Am. Chem. Soc., 2002, 124, 1283712844. 14. Bogani, L.; Vindigni, A.; Sessoli, R.; Gatteschi, D. J. Mater. Chem., 2008, 18, 4750-4758. 15. Coulon, C.; Miyasaka, H.; Clérac, R. Struct. Bonding, 2006, 122, 163–206. 16. Train, C.; Gheorghe, R.; Krstic, V.; Chamoreau, L.-M.; Ovanesyan, N. S.; Rikken, G. L. J. A.; Gruselle, M.; Verdaguer, M. Nat. Mater., 2008, 7, 729-734. 17. Numata, Y.; Inoue, K.; Baranov, N.; Kurmoo, M.; Kikuchi, K. J. Am. Chem. Soc., 2007, 129, 9902-9909. 18. Yoshida, Y.; Inoue, K.; Kikuchi, K.; Kurmoo, M. Chem. Mater., 2016, 28, 7029-7038. 19. Kumagai, H.; Inoue, K. Angew. Chem. Int. Ed., 1999, 38, 1601-1603. 20. Imai, H.; Inoue, K.; Kikuchi, K.; Yoshida, Y.; Ito, M.; Sunahara, T.; Onaka, S. Angew. Chem. Int. Ed., 2004, 43, 5618-5621. 21. Kurmoo, M. Phil. Trans. A, 1999, 357, 3041-3061. 22. Kurmoo, M.; Kumagai, H.; Green, M. A.; Lovett, B. W.; Blundell, S. J.; Ardavan, A.; Singleton, J. J. Solid State Chem., 2001, 159, 343-351. 23. Okamura, Y.; Ishii, N.; Nogami, T.; Ishida, T. Bull. Chem. Soc. Jpn., 2010, 83, 716-725.


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24. Rajca, A.; Wongsriratanakul, J.; Rajca, S. Science, 2001, 294, 1503–1505. 25. Abe, M. Chem. Rev., 2013, 113, 7011–7088. 26. Hosokoshi, Y.; Katoh, K.; Nakazawa, Y.; Nakano, H.; Inoue, K. J. Am. Chem. Soc., 2001, 123, 7921–7922. 27. Masuda, Y.; Kurtasu, M.; Suzuki, S.; Kozaki, M.; Shiomi, D.; Sato, K.; Takui, T.; Hosokoshi, Y.; Lan, X.-Z.; Miyazaki, Y.; Inaba, A.; Okada, K. J. Am. Chem. Soc., 2009, 131, 4670–4673. 28. Hicks, R. (Ed.) Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds; John Wiley & Sons: West Sussex, 2010. 29. Veciana, J.; Rovira, C.; Amabilino D. B. (Eds.) Supramolecular Engineering of Synthetic Metallic

Materials:

Conductors

and

Magnets,

Kluwer

Academic,

Dordrecht/Boston/London, 1999. 30. Keana, J. F. W.; Norton, R. S.; Morello, M.; van Engen, D.; Clardy. J. J. Am. Chem. Soc., 1978, 100, 934-937. 31. Fleischman, S. G.; Kuduva, S. S.; McMahon, J. A.; Moulton, B.; Walsh, R. B.; RodriguezHornedo, N.; Zaworotko, M. J. Cryst. Growth Des., 2003, 3, 909-919. 32. Stahly, G. P. Cryst. Growth Des., 2007, 7, 1007-1026. 33. Sommerdijk N. Angew. Chem. Int. Ed., 2003, 42, 3572–3574. 34. ter Horst, J. H.; Deij, M. A.; Cains. P. W.; Cryst. Growth Des., 2009, 9, 1531-1537.


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35. Jeffery, G. A. An Introduction to Hydrogen Bonding, Oxford University Press, Oxford, 1997. 36. Wang, X-P.; Chen, W-M.; Qi, H.; Li, X-Y.; Rajnák, C.; Feng, Z-Y.; Kurmoo, M.; Boča, R.; Jia, C-J.; Tung, C-H.; Sun, D. Chem. Eur. J., 2017, 23, 7990-7996. 37. Tanaka, A.; Inoue, K.; Hisaki, I.; Tohnai, N.; Miyata, M.; Matsumoto, A. Angew. Chem. Int. Ed., 2006, 45, 4142 –4145. 38. Bhatt, P. M.; Azim, Y.; Thakur, T. S.; Desiraju, G. R. Cryst. Growth Des., 2009, 9, 951– 957. 39. Shan, N.; Zaworotko, M. J. Drug Discovery Today, 2008, 13, 440-446. 40. Schultheiss, N.; Newman, A. Cryst. Growth Des., 2009, 9, 2950–2967. 41. Rodríguez-Hornedo, N.; Nehm, S. J.; Jayasankar, A.; Cocrystals: design, properties and formation mechanisms, In Encyclopedia of Pharmaceutical Technology, 3rd ed., Taylor & Francis, London, 2007, 615-635. 42. Bolton, O.; Matzger, A. J. Angew. Chem. Int. Ed., 2011, 50, 8960 –8963. 43. SAINT-Plus, version 6.02, Bruker Analytical X-ray System, Madison, WI, 1999. 44. G. M. Sheldrick, SADABS - An empirical absorption correction program; Bruker Analytical X-ray Systems, Madison, WI, 1996. 45. SHELXTL refinement program version 2016/6: G. M. Sheldrick, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 2015, 71, 3-8.


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46. Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Pushmann, H. OLEX2: A complete structure solution, refinement and analysis program, J. Appl. Cryst., 2009, 42, 339-341. 47. Bryant, J. R.; Taves, J. E.; Mayer, J, M. Inorg. Chem., 2002, 41, 2769-2776. 48. Adams, R. P.; Allen Jr., H. C.; Rychlewska, U.; Hodgson, D. J. Inorg. Chim. Acta, 1986, 119, 67-74. 49. Aitipamula, S.; Banerjee, R.; Bansal, A. K.; Biradha, K.; Cheney, M. L.; Choudhury, A. R.; Desiraju, G. R.; Dikundwar, A. G.; Dubey, R.; Duggirala, N.; Ghogale, P. P.; Ghosh, S.; Goswami, P. K.; Goud, N. R.; Jetti, R. R. K. R.; Karpinski, P.; Kaushik, P.; Kumar, D.; Kumar, V.; Moulton, B.; Mukherjee, A.; Mukherjee, G.; Myerson, A. S.; Puri, V.; Ramanan, A.; Rajamannar, T.; Reddy, C. M.; Rodriguez-Hornedo, N.; Rogers, R. D.; Row, T. N. G.; Sanphui, P.; Shan, N.; Shete, G.; Singh, A.; Sun, C. C.; Swift, J. A.; Thaimattam, R.; Thakur, T. S.; Thaper, R. K.; Thomas, S. P.; Tothadi, S.; Vangala, V. R.; Variankaval, N.; Vishweshwar, P.; Weyna, D. R.; Zaworotko, M. J. Cryst. Growth Des. 2012, 12, 2147−2152. 50. Grothe, E.; Meekes, H.; Vlieg, E.; ter Horst, J. H.; de Gelder, R. Cryst. Growth Des. 2016, 16, 3237−3243. 51. Boudreaux, E. A.; Mulay, L. N. Theory and Application of Molecular Paramagnetism, John Wiley & Sons, New York, 1976, p491. 52. Bonner, J. C.; Fisher, M. E. Phys. Rev., 1964, 135, A640. 53. Ruiz, E.; Alvarez, S.; Cano, J.; Polo, V. J. Chem. Phys., 2005, 123, 164110/1-7.


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54. Bleaney, B.; Bowers, K. D. Proc. R. Soc. London, Ser., A 1952, 214, 451-465. 55. Herpin, A. Theorie du Magnétisme, Presse Universitaire de France, Paris, 1968.


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“For Table of Contents Use Only”

Co-Crystallization of Achiral Components into Chiral Network by Supramolecular Interactions: Coordination Complexes - Organic Radical Yan-Li Gao, Kseniya Yu Maryunina, Sayaka, Hatano, Sadafumi Nishihara, Katsuya Inoue, Mohamedally Kurmoo

SYNOPSIS Unexpected chiral co-crystals were generated from achiral organic radical and cisMII(hfac)2(H2O)2 (M = Co or Mn). X-ray diffraction, infrared spectroscopy and magnetization measurements collectively found the superposition of properties of the individual components without any charge or proton transfer confirming the genuine nature of co-crystals. The chirality is associated with the extensive supramolecular interactions in the solids.


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Coordination Complexes

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