Guest Driven Structural Correlations in DPDS [Di(4-pyridyl)disulfide

Article pubs.acs.org/crystal

Guest Driven Structural Correlations in DPDS [Di(4-pyridyl)disulfide]Based Coordination Polymers Noelia De la Pinta,†,‡ Luz Fidalgo,§ Gotzon Madariaga,‡ Luis Lezama,† and Roberto Cortés*,† †

Departamento de Química Inorgánica and ‡Departamento de Física de la Materia Condensada, Fac. de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain § Departamento de Química Inorgánica, Fac. de Farmacia, Universidad del País Vasco UPV/EHU, Apartado 450, 01080 Vitoria-Gasteiz, Spain S Supporting Information *

ABSTRACT: Three novel coordination polymers have been obtained by the reaction of M(NO3)2·6H2O (M = MnII and CoII) or FeCl2·4H2O with KNCS and DPDS [di(4-pyridyl)disulfide] ligand, [Mn(NCS)2(DPDS)2]2·DPDS·H2O (1), [Fe(NCS)2(DPDS)2]·3H2O (2), and [Co(NCS)2(DPDS)2]·2H2O (3). The three complexes exhibit infinite linear chain structures, where the metal ions are connected by double N,N′-DPDS bridges, that are further connected through hydrogen bonding to give pseudo-3D structures which contain channels where solvent and/or free DPDS molecules are located. The number and type of these guest molecules will have a determining influence in the final crystal system and space groups adopted for every compound obtained, which will be analyzed. H-bonding promotes interpenetrated 3D networks in 1− 3. Characterization by IR, UV−vis, X-ray diffraction, ESR spectroscopy, and magnetic measurements is developed. Slight antiferromagnetic interactions are observed, essentially in the Fe(II) and Co(II) compounds, that are associated with the double DPDS bridges.

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ligand6 has an intermediate rigidity associated with the S−S bond, allowing a characteristic twisted shape and giving rise, in combination with the geometry of the metal ion, to a structural diversity of coordination polymers. This ligand also possesses two enantiomer forms (M and P) and even has potential biological applications in their broken conformations.7 Furthermore, the DPDS ligand is known to transform in the DPS (di(4-pyridyl)sulfide) one and others under solvothermal conditions at temperatures higher than 100 °C via in situ disulfide cleavage reactions.1b,8 On the other hand, the molecule chosen to reach electroneutrality in this case has been the thiocyanate (NCS) pseudohalide.9 The ability of this anion to act as terminal or bridging ligand opens a wide range of possibilities to give different structural conformations in the compounds it forms. In this work, three DPDS-based compounds are presented, [Mn(NCS)2(DPDS)2]2·DPDS·H2O (1), [Fe(NCS)2(DPDS)2]·3H2O (2), and [Co(NCS)2(DPDS)2]·2H2O (3). Although they are one-dimensional polymers, a pseudosupra dimensional structure is achieved through hydrogen bonding. The resulting network of channels accommodates different amounts and types of disordered guest molecules, which determine the final crystal system and space group.

INTRODUCTION The quick development in the very recent years of the research on the formerly known 4,4′-dipyridine type of ligands is related to their use in very important present fields of investigation, such as metal organic frameworks (MOFs),1 coordination polymers (CPs),2 spin crossover (SCO) systems,3 and others. These ligands are well-known to be excellent different-size spacers in order to connect chains or sheets, increasing their dimensionality, increasing the structural flexibility, and generating voids of a quadrangular type. The 4,4′-relative position of the N donor atoms provides the extension of these polymers, with the rigidity being a limiting factor for a selfassembly strategy. The design and synthesis of coordination polymers are of great interest for crystal engineering. The structural motifs in the CPs range from zero to threedimensional, and their infinite network topologies are interesting for the development of host−guest functional materials such as multiferroics,4 since many of these types of compounds present some kind of magnetic ordering. In particular, porous MOFs are increasingly being studied for potential storage of different kinds of molecules.5 Structures and, therefore, the properties of these materials may be controlled by choosing appropriate bridging ligands and metal ions. Among this kind of ligands, one of the less studied groups is that where the extreme pyridine rings are connected through sulfur atoms. In particular, the di(4-pyridyl)disulfide (DPDS) © 2012 American Chemical Society

Received: July 19, 2012 Revised: August 23, 2012 Published: August 28, 2012 5069

dx.doi.org/10.1021/cg3010135 | Cryst. Growth Des. 2012, 12, 5069−5078

Crystal Growth & Design

Article

Characterization by different spectroscopies (IR, UV−vis, ESR), X-ray single-crystal structures, and magnetic measurements is also provided.

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EXPERIMENTAL SECTION

Materials. All solvents and starting materials for synthesis were purchased commercially and were used as received. Metal(II) nitrate hydrates (Aldrich), di(4-pyridyl)disulfide (Aldrich), and potassium thiocyanate were used without further purification. Synthesis of [Mn(NCS)2(DPDS)2]2·DPDS·H2O (1). This compound was obtained by mixing of KNCS (0.048 g, 0.5 mmol) and Mn(NO3)2·6H2O (0.072 g, 0.25 mmol) in an aqueous solution (20 mL). After stirring (about 30 min), a methanol solution (20 mL) of di(4-pyridyl)disulfide (DPDS) (0.055 g, 0.25 mmol) was added. The resulting solution was filtered off the precipitate and was left to stand at room temperature. Several days later, yellow prismatic X-ray quality crystals were obtained. Anal. Calcd for Mn2C54H40N14S14O: C 44.43, H 2.76, N 13.43, S 30.75; found C 43.86, H 2.64, N 13.74, S 31.45. Synthesis of [Fe(NCS)2(DPDS)2]·3H2O (2). This compound was synthesized by slow diffusion of a water solution (10 mL) containing KNCS (0.097 g, 1 mmol) and FeCl2·4H2O (0.050 g, 0.25 mmol) with a methanol solution (10 mL) of DPDS (0.055 g, 0.25 mmol) in a tube glass vessel. After a few days, yellow-orange prisms were isolated as single crystals suitable for X-ray diffraction. Anal. Calcd for FeC22H22N6O3S6: C 39.63, H 3.33, N 12.60, S 28.86; found C 40.87, H 3.20, N 12.41, S 29.06. Synthesis of [Co(NCS)2(DPDS)2]·2H2O (3). This compound was synthesized by the same method as that for 2, but using Co(NO3)2·6H2O (0.073 g, 0.25 mmol). Red prismatic crystals appeared several weeks later. Anal. Calcd for CoC22H20N6O2S6: C 40.54, H 3.09, N 12.89, S 29.52; found C 40.16, H 2.92, N 12.75, S 29.19. Thermoanalytical data for 1−3 are shown in Table S1 of the Supporting Information. General Methods. Microanalyses were performed with a LECO CHNS-932 analyzer. Infrared spectroscopy was performed on a MATTSON FTIR 1000 spectrophotometer as KBr pellets in the 400− 4000 cm−1 region. Diffuse reflectance spectra were registered at room temperature on a CARY 2415 spectrometer in the range 5000−45000 cm−1. ESR spectroscopy was performed on powdered samples at the X-band frequency, with a BRUKER ESR 300 spectrometer equipped with a standard OXFORD low-temperature device, which was calibrated by the NMR probe for the magnetic field. The frequency was measured with a Hewlett-Packard 5352B microwave frequency computer. The magnetic susceptibility measurements of polycrystalline samples of the complexes were carried out in the temperature range 4.2−300 K at a value of the magnetic field of 1000 G, using a Quantum Design SQUID magnetometer, equipped with a helium continuousflow cryostat. The complex (NH4)2Mn(SO4)2.6H2O was used as a susceptibility standard. The experimental susceptibilities were corrected for the diamagnetism of the constituent atoms (Pascal tables).10 Crystal Structure Determination. Single-crystal X-ray measurements for compounds 1 and 2 were taken, at room temperature, on an Oxford Diffraction Xcalibur 2 diffractometer (graphite-monochromated Mo Kα radiation, λ = 0.71073 Å) fitted with a Sapphire CCD detector. Data frames were processed (unit cell determination, intensity data integration) using the CrysAlis11 software package. In the case of compound 3, single-crystal X-ray measurements were also taken at room temperature on a STOE IPDS I (Imaging Plate Diffraction System) diffractometer with graphite monochromated Mo Kα radiation. Intensity data were collected in the θ ranges 2.93−25.06° (1), 3.34−25.00° (2), and 2.58−26.00° (3). An analysis of the diffraction pattern of compound 2 (see Figure 1) showed the existence of twinning. All the reflections can be explained in terms of two domains of almost equal volume, related by a 2-fold axis along c*. The structures were solved by direct methods using the program SIR9712 and refined by a full-matrix least-squares procedure on F2 using SHELXS97.13 In Table 1, crystallographic data and processing parameters for compounds 1−3 are listed.

Figure 1. Reconstruction of the (h0l) reciprocal plane of compound 2 showing the twinning present in the sample. The twin law is a 2-fold rotation around c*.

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RESULTS AND DISCUSSION Crystal Structures Refinement and Results. A glance at the cell parameters and symmetry of the compounds indicates that the structure of compound 2 is slightly distorted with respect to that of compound 3, whereas compound 1 suffers more drastic changes and apparently it is totally uncorrelated with compounds 2 and 3. The positions of the metal ions and the covalent backbone can be found straightforwardly. The lattices of compounds 2 and 3, being essentially identical, are closely related (see Figure 2) to that of compound 1. Moreover the space groups follow the group−subgroup chain: ⎛1 1 ⎞ ⎛1 0 0⎞ 2 ⎟ ⎜ 2 0 ⎜ ⎟ ⎜ ⎟ Ccc 2 > Cc ⎜ 0 1 0 ⎟ > P 21 1 ⎜ 2 0 − 1 2⎟ ⎝0 0 1⎠ ⎜ ⎟ ⎝0 2 0 ⎠

The transformation matrices relate the monoclinic direct bases to that of the orthorhombic one in the form am,i = ao,jMji: i, j = 1, 2, 3. In the case of compound 1, notice that the lattice parameters derived from the transformation matrix are a′m ≈ 12.28 Å, b′m ≈ 21.82 Å, c′m ≈ 12.28 Å, and β′ ≈ 110.8°, which are of the order of the values found experimentally. At the most basic level of the structure, the metal atoms are located on two interpenetrated networks that from now on will be labeled as blue and as orange, given the colors used in Figure 3. Whereas compounds 2 and 3 show an essentially identical metal distribution, in compound 1 at least one of the networks appears to be very distorted. The edge length of each network is determined by the tilt of the molecules that coordinate the metal ions (see Figure 3). In the case of compound 2, the edge lengths are 8.741(4) Å [and 9.037(4) Å owing to the small monoclinic distortion] for the blue lattice and 11.540(4) [11.530(4) Å] for the orange one. For compound 3 the corresponding lengths are 8.853(4) Å and 11.487(4) Å, respectively. Compound 1 is a bit more difficult to describe. The orange lattice defines alternatively identical sheets of Mn1 and Mn2 atoms with edges of 10.8883(16) Å and 11.3297(11) Å similar to that of compounds 2 and 3. However, the blue lattice is a very distorted honeycomb distribution of 5070



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Table 1. Crystallographic Collection and Refinement Parameters for Compounds 1−3 1

2

3

formula Mr cryst syst space group a (Å) b (Å) c (Å) β (deg) V (Å3) Z F(000) ρcalc(g cm−3) μ(Mo Kα)/mm−1 θ range (deg) reflns cltd/reject unique reflns Rint reflns (Io > 2σ(Io) refined twin fraction exp twin fraction twin law

Mn2C54H40N14S14O 1459.86 monoclinic P21 10.8883(3) 29.2108(7) 11.3297(4) 118.486(4) 3167.2(2) 2 1488 1.531 0.912 2.93−25.06 15764/28 9213 0.034 6840

CoC22H20N6O2S6 651.79 orthorhombic Ccc2 13.946(8) 20.218(7) 10.911(3) 90 3077(2) 4 1332 1.407 0.994 2.58−26.00 11958/375 1573 0.066 1573

Flack parameter parameters R1 (F0) wR2(F02) GOF

0.02(2) 902 0.0469 0.1084 0.991

FeC22H22N6O3S6 666.68 monoclinic Cc 14.026(2) 20.318(3) 10.9270(15) 91.966(14) 3112.2(8) 4 1344 1.410 0.920 3.34−25.00 17333/8851 8482 0.16 2981 0.518(2) 0.52 ⎛− 1 0 0 ⎞ ⎜ ⎟ ⎜ 0 −1 0 ⎟ ⎝ 0 0 1⎠ 0.05(3) 385 0.0691 0.1806 0.870

0.00(2) 200 0.0312 0.0743 0.836

common structural feature for the three compounds is the existence of channels along the c axis (see Figure 4). An analysis of the residual electron density within the channels (Figure 5) indicates the origin of the different structural distortions and the corresponding symmetry decrease. The guest molecules used to model the different residual electron density are DPDS and H2O, in the case of compound 1, and water in different proportions for the Fe (2) and Co (3) compounds. Water molecules are distributed in zigzag chains with two equally probable dispositions, whereas the DPDS guest molecules appear in the two possible enantiomer configurations (M and P), in agreement with the usual achiral distribution of DPDS.6c In compounds 2 and 3, the set of lattice planes belonging to the orange network, which are parallel to the (b,c) plane, define the average positions of the DPDS ligands, whereas the lattice planes parallel to the (a,c)

Figure 2. Relation between the lattices of compounds 1 {a′m, b′m, c′m}, 2 {am, bm, cm}, and 3 {ao, bo, co}.

Mn1 and Mn2 atoms (Figure 3a and 4b) whose edges have lengths of 7.2257(14) Å, 8.9437(15) Å, and 9.6014(12) Å. A

Figure 3. Distribution of the metal ions in two interpenetrated networks for 1, 2, and 3. 5071



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Figure 4. (a) Projection along the c axis of the two interpenetrated networks for compound 3 (almost identical to that of compound 2) showing the distribution of organic ligands. (b) Same for compound 1, indicating the labels of each atomic site. In both cases the structures exhibit continuous channels along c.

Table 2. Details of the Coordination Environment for Compounds 1, 2, and 3a Mn (1) Mn1 min distance max. distance Lav (Å) volume (Å3) D λ σ2 (deg2)

Mn2

Fe (2)

Co (3)

N15 = 2.148(6) N14 = 2.328(5) 2.2643 15.4484

N26 = 2.139(7) N24 = 2.324(5) 2.2582 15.3201

N6 = 2.005(12) N2 = 2.250(11) 2.1439 13.0877

N12 = 2.058(3) N3 = 2.198(4) 2.1691 13.5359

0.03245 1.0025 0.3209

0.03322 1.0027 0.6186

0.02685 1.0035 6.4267

0.03720 1.0053 6.9550

a

Lav = average bond length; D14 = distortion index (bond length) D = (1/n)∑ni=1|li − lav|/lav, where l0 = center to vertex distance of a regular polyhedron of the same volume; λ15 = quadratic elongation, ⟨λ⟩ = (1/ n)∑ni=1(li)/(l0)2, where li = distance from the central atom to the ith coordinating atom; σ2 = bond angle variance; σ2 = 1/(m − 1)∑mi=1(ϕi − ϕ0)2, where m = 3/2(the no. of faces in the polyhedron) = no. of bond angles, ϕi = the ith bond angle, ϕ0 = the ideal bond angle for a regular polyhedron.

Figure 5. Difference Fourier maps along the c axis for the following: (a) compound 1 x-range [0, 0.5], y-range [0.13, 0.26], electron density levels at 0.35 e/Å3, 0.60 e/Å3, and 1 e/Å3; (b) compound 2 x-range [0.4, 0.6], y-range [0.4, 0.6], electron density levels at 0.43 e/Å3, 0.60 e/Å3, and 0.8 e/Å3; (c) compound 3 x-range [0.4, 0.6], y-range [0.4, 0.6], electron density levels at 0.23 e/Å3, 0.50 e/Å3, and 0.75 e/Å3. The atomic model is also shown. Water hydrogens could not be determined for compound 2.

plane (blue network) contain the average positions of the NCS molecules. In compound 1 the average positions of all the DPDS molecules lie on planes that are parallel to (a,c) and belong to (or are parallel to those of) the orange network. The (a,b) planes of the blue network contain the average positions of the NCS ligands, but owing to the peculiar geometry of the network, they are distributed following a zigzag arrangement (Figure 4a). Table 2 shows the minimum and maximum distances and details of their octahedral coordination environment for every compound 1−3. The structure of compound 1 contains two crystallographically independent metal centers, Mn1 and Mn2. At a higher level of complexity, it can be described as consisting of chains (Figure 6) extending along the [1 0 0] direction, where the Mn(II) ions are double linked through N,N′-coordinated DPDS ligands (dihedral angles, C134−S13−S14−C141 = 87.6(3)° and C121−S12−S11−C111 = 87.2(3)° for Mn1; C211−S21−S24−C241 = 87.1(3)° and C221−S22−S23−

Figure 6. MnII chains extending along the [1 0 0] direction.

C231 = 86.5(3)° for Mn2); the Mn···Mn intrachain distance for both units has the same value (10.88 Å for one of the edges of the orange network). The octahedral coordination of these cations is completed by two thiocyanate groups in the axial positions, which exhibit a quasi linear conformation (N15− C151−S151 = 178.4(6)° and N16−C161−S161 = 179.4(8)° for Mn1; N25−C251−C251 = 179.0(6)° and N26−C261− S261 = 178.1(8)° for Mn2). These chains are interconnected by intermolecular H-bonds [the most important being C235···S151 = 3.604(6) Å, where C235−H235 = 0.930(7) Å, H235···S151 = 3.161(2) Å, and 5072



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Figure 7. (a) Packing of the chains on the xy plane to give layers Mn(2)−Mn(1); (b) sites of the guest molecules in the channels between the layers. The H-bonds and hydrogen atoms are omitted for clarity.

of the space based on a great number of intermolecular Hbonds (see table 4). The disordered description of guest molecules through their two possible enantiomer configurations makes the structure achiral. The lack of chirality is a common feature of all DPDS-containing compounds reported up to now.6c The covalent architectures of compounds of FeII (2) and CoII (3) are almost iso-structural, and therefore, they will be described together. These structures consist of chains extending along the [0 0 1] direction (Figure 9), where the metal ions are connected by double N,N′-coordinated DPDS bridging ligands, which site in the equatorial plane. The octahedral coordination sphere of these ions is completed by two terminal N-bonded disordered thiocyanate groups (in axial positions), with their average conformation being quasi linear (Figure 9). Due to the slightly different C−S−S−C torsion angles [C21−S2−S1−C11 = 91.8(6)° and C41−S4−S3−C31 = 91.4(7)° for compound 2; C5−S1−S6−C6 = 91.32(19)° for compound 3], the intermetallic distance through DPDS-bridges slightly modifies from 10.927 Å to 10.911 Å for compounds 2 and 3, respectively. The most important H-bonds responsible for connecting M(DPDS)2-M chains [M = Fe (2) or Co (3)], located in the xz and yz planes, are listed in Table 5. Whereas Figure 10 shows the packing of these chains in the plane xy, which leads to the formation of corrugated layers extending in the [1 0 0] and [0 1 0] directions. In the same way, the disposition of these layers, also linked by H-bonds, originates channels along c (11.530 Å × 8.741 Å for compound 2 and 11.487 Å × 8.854 Å for compound 3) in which water guest molecules connected by H bonds are located (see Figures 10 and 11). In both compounds, the water guest molecules stack along the [0 0 1] direction (Figure 11), the same as that for extending of the chains. Infrared Spectra. A summary of the most important IR bands corresponding to compounds 1−3, together with their tentative assignment, is given in Table 6. On the other hand, the frequencies of the IR bands related to the DPDS ligand in the compounds are slightly higher than their positions in the free ligand, showing that the pyridyl rings behave similarly in the complexes. The frequency values and the non split observed in the νas(C−N)NCS band for compounds 2 and 3, agree well

C235−H235−S151 = 111.3(4)°], giving rise to the formation of layers Mn1−Mn2 along the xy planes (Figure 7a). The disposition of these layers, that are linked by intermolecular Hbonds too (Table 3), produces channels (size 11.371 Å × 10.888 Å) where the lattice molecules (DPDS and H2O) are located (Figures 4b and 7b). Table 3. Selected Most Important Intermolecular H-Bonds between the Layers (Maximum = Sum of vdW Radii + 0.5 Å) for Compound 1 C214···H214 0.929(6) C215···H215 0.93(7) C112···H112 0.931(7) C113···H113 0.930(6)

C214···S161 3.500(6) C215···S161 3.589(7) C112···S261 3.609(7) C113···S261 3.583(7)

H214···S161 3.058(3) H215···S161 3.251(4) H112···S261 3.292(5) H113···S261 3.213(3)

C214−H214···S161 111.0(74) C215−H215···S161 103.8(4) C112−H112···S261 102.4(4) C113−H113···S261 106.0(4)

As can be seen in Figure 8, the guest groups are disposed along the [0 0 1] direction between the layers, which are arranged in the yz plane. In this case, the torsion angles of DPDS guests are C11−S1−S2-C21 = 108(1)° and C31−S3− S4-C41 = 107(2)°. The resulting arrangement provides a filling

Figure 8. Stacking of the guest molecules (water and DPDS) along the [0 0 1] direction in 1. 5073



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Table 4. Selected Most Important Intermolecular H-Bonds between the Layers and the Guest Molecules (Maximum = Sum of vdW Radii + 0.5 Å) for Compound 1 C14···H14 0.94(3) C24···H24 0.93(2) C113···H113 0.930(6) C142···H142 0.930(7) C143···H143 0.930(6) C23···H23 0.92(3) N2···O1W 2.43(3) C143···H143 0.930(6) C245···H245 0.929(6)

DPDS(1) guest (50%) with the layers C14···S261 H14···S261 C14−H14···S261 3.67(2) 3.250(4) 110(2) C24···S261 H24···S261 C24−H24···S261 3.29(3) 2.515(5) 141(2) C113···N1 H113···N1 C113−H113···N1 3.44(2) 2.88(2) 120.5(7) C142···N2 H142···N2 C142−H142···N2 3.66(3) 2.88(3) 142.1(7) C143···N1 H143···N1 C143−H143···N1 3.52(3) 2.89(3) 126.3(7) H2O(1) with the DPDS (1) guests (50%) C23···O1W H23···O1W C23−H23···O1W 1.98(5) 1.39(4) 116(2)

H2O(1) with the layers C143··O1W H143···O1W 3.66(2) 2.94(2) C245···O1W H245···O1W 3.66(3) 2.83(3)

C43···H43 0.93(4) C142···H142 0.930(7) C143···H143 0.930(6) C244···H244 0.930(7)

DPDS(2) (50%) with the layers C43···S161 H43···S161 3.47(3) 2.796(4) C142···N4 H142···N4 3.60(6) 3.12(6) C143···N4 H143···N4 3.62(6) 3.12(5) C244···S3 H244···S3 3.64(2) 3.70(1)

C43−H43···S161 130(3) C142−H142···N4 114(1) C143−H143···N4 116(1) C244−H244···S3 79.4(5)

H2O(2) with the DPDS (2)(50%) N4···O2W 2.49(6)

C143−H143···O1W 134.6(7) C245−H245···O1W 149.0(7)

spectrum shows a band associated with a charge transfer. The values calculated from these transitions are Dq = 880 cm−1 and B = 673 cm−1. The value of B is indicative of 69.3% of covalence of the Co−N bonds in this compound. ESR Spectroscopy. ESR measurements were carried out at several temperatures in the range 4.2−300 K. For compound 1, the thermal variation of the ESR spectra (Figure S3 of the Supporting Information (SI)) shows apparently isotropic signals at g = 2, being very wide [more than 600 G “peak-topeak” (ΔHpp) at room temperature] and with almost imperceptible shoulders to both sides of the main signal. A much weaker half-field signal (spin forbidden ΔMs = 2 transition) can also be observed. On the other hand, the intensity of the mean signal strongly increases upon cooling, but its line-width remains practically constant. Besides, slight modifications of the form of this signal are also observed (Figure S3). The ESR spectrum at 4.2 K (Figure 13) can be described as that corresponding to an isotropic g tensor. After considering different effects (hyperfine interaction, ZFS, g anisotropy, and dipolar interactions), the best fit for the signal was obtained by taking into account both the effect of hyperfine interaction and the zero field splitting (ZFS) associated with the S = 5/2 spin state. Under this hypothesis, the simulation shown in Figure 13 was obtained with the following values: g = 1.995, ΔHpp = 260 G, A = 85 G, D = 150 G, and E = 40 G, showing an excellent agreement between the experimental and calculated spectra, with the half-field signal (forbidden) not being considered. These values are similar to that found for Mn(II) ions in an octahedral environment having a small distortion.19 Due to observation of both effects, hyperfine coupling and ZFS, the magnetic interactions can be predicted to be extremely weak, but not negligible, due to the Lorentzian lines observed. In the case of compound 3, the ESR spectra at low temperatures show very wide signals, and above 125 K, the ESR signal is not yet detected. By decreasing from this temperature, the spectrum shows an isotropic appearance down to 20 K, where an axial component appears. As can be observed in

Figure 9. FeII (up) and CoII (down) chains extending along the [0 0 1] direction.

with equivalent N-terminal dispositions for this ligand. The split of this band observed in 1 is associated to the existence of nonequivalent terminal NCS groups in this compound. The corresponding spectra have been grouped and can be observed in Figure S2 of the Supporting Information. UV−Vis Spectroscopy. The diffuse reflectance spectra for compounds 2 and 3 can be observed in Figure 12, and the results have been listed in Table 7. The spectra have been interpreted following Tanabe-Sugano diagrams.17 Results are in good agreement with the values found in the literature for each ion in their respective coordination environment.18 The diffuse reflectance spectrum for the FeII compound (2) exhibits a single allowed transition (5T2g to 5Eg), split due to the Jahn−Teller effect (5Eg is split into 5A1 + 5B1), in agreement with high-spin slightly distorted octahedral FeII. At high wavenumbers, the spectrum shows a charge-transfer band overlapping with the triplet states. The values of Dq and the 8 /3dσ are 916 cm−1 and 1700 cm−1, respectively. The diffuse reflectance spectrum for the CoII compound (3) exhibits three spin-allowed transitions from the ground state 4 T1g to the excited states 4T2g, 4A2g, and 4T1g, respectively, as corresponds to high-spin octahedral CoII. At 35000 cm−1, the 5074



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Table 5. Selected Most Important Intermolecular H-Bonds between the Chains (Maximum = Sum of vdW Radii +0.5 Å) for Compounds 2 and 3 C13···H13 0.93(1) C35···H135 0.93(2) C14···H14 0.93(1) C15···H15 0.93 C22···H22 0.93(1) C22···H22 0.93 C23···H23 0.93 C32···H32 0.93(1) C45···H45 0.93(1) C13···H13 0.93 C4···H4 0.93(1) C15···H15 0.93(1) C4···H4 0.93(1)

Fe compd (2) C13···S1 H13···S1 3.54(1) 3.097(4) C35···S3 H35···S3 3.68(1) 3.361(4) C14···S5 H14···S5 3.68(2) 3.08(2) C15···S5′ H15···S5′ 3.564 2.875 C22···S6 H22···S6 3.57(2) 3.03(2) C22···S6′ H22···S6′ 3.689 2.989 C23···S6 H23···S6 3.556 2.977 C23···S6 H32···S6 3.65(2) 3.00(2) C45···S5′ H45···S5′ 3.64(2) 3.17(2) Co compd (3) C13···S1 H13···S1 3.58(1) 3.239(1) C4···S3 H4···S3 3.50(1) 2.94(1) C15···S3 H15···S3 3.58(1) 3.03(1) C4···S3′ H4···S3′ 3.66(1) 2.91(1)

chain with the molecules of water C13−H13···S1 111.3(9) C35−H35···S3 103(1) C14−H14···S5 124.3(9) C15−H15···S5′ 133.71(1) C22−H22···S6 118.6(8) C22−H22···S6′ 133.25(1) C23−H23···S6 121.80(1) C32−H32···S6 128.6(9) C45−H45···S5′ 113.6(9)

O5···S6′ 3.21(4)

C13−H13···S1 104.1(3) C4−H4···S3 120.2(3) C15−H15···S3 119.0(3) C4−H4···S3′ 138.9(3)

O1W···H1W2 0.9839 O2W···H2W1 0.9(39)

between the molecules of water O2···O7 2.62(5) O7···O5 2.59(5) O5···O2 2.58(5) O1···O3 2.60(5) O3···O4 2.59(6)

O2W···H2W1 0.9(3)

chain with the molecules of water O1W···S3′ H1W2···S3′ 3.39(2) 2.8(3) O2W···S3′ H2W1···S3′ 3.39(2) 2.6(4) between the molecules of water O2W···O1W H2W1···O1W 2.61(5) 2.4(5)

O1W−H1W2···S3′ 131(30) O2W−H2W1···S3′ 140(32)

O2W−H2W1···O1W 92(27)

Figure 10. Representation of the layers of compounds 2 (left) and 3 (right) in the xy plane.

K. The value of the χmT product for compound 1 remains practically constant (4.02 cm3·K·mol−1 at RT) in all the temperature range, with a minor decrease at low temperature. So, in good agreement with the ESR spectroscopy results, this compound should show very weak magnetic interactions due to the zero field splitting and the hyperfine coupling. The value of χm for compound 2 increases upon cooling from 10.9 × 10−3 cm3·mol−1 at room temperature, being exponential at the low temperature (Figure S5 of the SI). As can be observed in Figure 16, the variation of χm−1 is well described by the Curie−Weiss law within the whole temperature range, with

Figure 14, the signal at 4.2 K shows a g-tensor with an axial symmetry, common in Co(II) ions with S = 1/2. Despite the line-width at this temperature, the g∥ and g⊥ acquire the values 6.80 and 3.05, respectively. Magnetic Measurements. Magnetic susceptibility measurements were performed on powdered samples in the 300−4.2 K temperature range for all compounds. Thermal variations of χm for 1−3 are shown in Figures S4, S5, and S6 of the SI. As can be observed in Figure 15, the variation of χm−1 is well described by the Curie−Weiss law within the whole temperature range, with values of Cm = 4.24 cm3·K·mol−1 and θ = 0.24 5075



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Figure 12. UV−vis spectra of compounds 2 and 3.

Table 7. UV−Vis Bands (cm−1) and Assignments for Compounds 2 and 3 transition

band

ν (cm−1)

T2g → A1 T2g → 5B1g 4 T1g(F) → 4T2g 4 T1g(F) → 4A2g 4 T1g(F) → 4T1g(P)

ν1A ν1B ν1 ν2 ν3

9160 10860 9600 18400 20500

compd

Figure 11. View of the channels in the xy and yz planes, including water guest molecules, for 2 and 3.

Fe (2)

values of Cm = 3.25 cm3·K·mol−1 and θ = −1.40 K. In the same way, the product χmT is practically constant (3.23 cm3·K·mol−1 at RT) down to 50 K, rapidly decreasing upon further cooling. The thermal behavior described for χmT, together with the negative sign of the Weiss constant, is indicative of slight antiferromagnetic coupling between the metallic centers. Equation 1 is the theoretical approach for the magnetic behavior of this compound. In this expression, χm is a function of the J parameter due to the exchange coupling along an infinitive spin20 linear chain scaled to S = 2 and based upon the spin Hamiltonian H = −2J∑SiSi+1. 6Nβ 2g 2 ⎛ 1 − u ⎞ ⎜ ⎟ 3KT ⎝ 1 + u ⎠

5

5

Co (3)

χm =

5

(1)

Where u=

T T − coth ; T0 T0

T0 = 12

J K

According to eq 1, the best fitting parameters are g = 2.08 and J = −0.18 K, where the value of g is a usual one for octahedral Fe(II) ions.21

Figure 13. Experimental (continuous line) and calculated (dashed line) powder ESR spectra for 1 at 4.2 K.

Table 6. IR Bands (cm−1) and Assignments for Compounds 1−3 and Free DPDS Ligand compd bands16

1

2

3

DPDS

ν(C−H)DPDS νas(C−N)NCS ν(CC,CN)DPDS ν(ArC−C)DPDS ν(C−S)NCS δep(ArC−H)DPDS νfp(ArC−S)DPDS ν(S−S)DPDS

2800−3000 2082, 2074 1588 1419 804 1065/1009 712 600

3000 2064 1588 1419 804 1096/1060 712 594

3000 2074 1588 1414 820 1101/1060 717 597

2800−3000

5076

1594 1413 1018/989 700 500



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Figure 16. Thermal variation of χmT (circles), χm−1 (triangles), and the Curie−Weiss law for 2. The solid lines (green) represent the best fits obtained.

Figure 14. Thermal variation of the experimental X-band powder ESR spectra for 3.

Figure 17. Thermal evolution of χmT (circles) and χm−1 (triangles) for compound 3 and the corresponding Curie−Weiss law. The solid line (green) represents the best fit obtained.

The values of χmT for 3 are observed to decrease upon cooling, from 2.95 cm3·K·mol−1 at room temperature to 1.84 cm3·K·mol−1 at 5 K. The thermal behavior of χm−1 and χmT could be interpreted as caused by antiferromagnetic interactions between the Co(II) centers. However, the strong decrease of μeff should be mainly attributed in this case to the spin−orbit coupling effect characteristic of CoII ions. Unfortunately, this effect does not allow calculation of the magnetic exchange coupling constant (J) associated with this compound.

Figure 15. Thermal evolution of χmT (circles) and χm−1 (triangles) for 1 and the corresponding Curie−Weiss line (green), which represents the best fit obtained.

The value of χm for compound 3 (Figure S6 of the SI) increases upon cooling from a value of 10.48 × 10−3 cm3·mol−1 at room temperature, being exponential at low temperature. Figure 17 shows the thermal variation of the χm−1 and χmT magnitudes for this compound. As can be observed, the Curie− Weiss law is obeyed down to 25 K with the values of Cm = 3.15 cm3·K·mol−1 and θ = −18 K.

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CONCLUSIONS The mean structural motif in compounds 1−3 consists of -M(DPDS)2-M- linear chains, which group through hydrogen bonding to give interpenetrated 3D highly flexible networks. The resulting network of channels in compounds 1−3 5077



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(4) Zhang, W.; Xiong, R.-G. Chem. Rev. 2012, 112, 1163. (5) (a) Getman, R. B.; Bae, Y.-S.; Wilmer, C. E.; Snurr, R. Q. Chem. Rev. 2012, 112, 703. (b) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Chem. Rev. 2012, 112, 724. (c) Suh, M. P.; Park, H. J.; Prasad, T. K.; Lim, D.-W. Chem. Rev. 2012, 112, 782. (d) Wu, H.; Gong, Q.; Olson, D. H.; Li, J. Chem. Rev. 2012, 112, 836. (6) (a) De Sousa Moreira, I.; De Lima, J. B.; Franco, D. W. Coord. Chem. Rev. 2000, 196, 197. (b) Tabellion, F. M.; Seidel, S. R.; Arif, A. M.; Stang, P. J. J. Am. Chem. Soc. 2001, 123, 7740. (c) Horikosi, R.; Mochida, T. Coord. Chem. Rev. 2006, 250, 2595. (d) Carballo, R.; Covelo, B.; Fernandez-Hermida, N.; Lago, A. B.; Vazquez-Lopez, E. M. CrystEngComm 2009, 11, 817. (e) Li, J.-X.; Guo, W.-B.; Du, Z.-X.; Huang, W.-P. Inorg. Chim. Acta 2011, 375, 290. (7) (a) Akrivos, P. D. Coord. Chem. Rev. 2001, 213, 181. (b) Lobana, T. S.; Sharma, R.; Bermejo, E.; Castiñeiras, A. Inorg. Chem. 2003, 42, 7728. (c) Lobana, T. S.; Sharma, R.; Mehra, S; Castiñeiras, A.; Turner, P. Inorg. Chem. 2005, 44, 1914. (d) Zhang, X.-M.; Fang, R.-Q.; Wu, H.-S. J. Am. Chem. Soc. 2005, 127, 7670. (e) Li, D.; Wu, T.; Zhou, X.P.; Zhou, R.; Huang, X.-C. Angew. Chem., Int. Ed. 2005, 44, 4175. (8) (a) Díaz, C.; Arancibia, A. Polyhedron 2000, 19, 2679. (b) Horikoshi, R.; Mochida, T.; Moriyama, H. Inorg. Chem. 2002, 41, 3017. (c) Sukcharoenphon, K.; Moran, D.; Schleyer, P. V. R.; McDonough, J. E.; Abboud, K. A.; Hoff, C. D. Inorg. Chem. 2003, 42, 8494. (d) Ma, L.-F.; Wang, L.-Y.; Du, M. CrystEngComm 2009, 11, 2593. (9) (a) Rojo, T.; Cortés, R.; Lezama, L.; Mesa, J. L.; Villeneuve, G. Inorg. Chim. Acta 1989, 162, 11. (b) Rojo, T.; Cortés, R.; Lezama, L.; Arriortua, M. I.; Urtiaga, M. K.; Villeneuve, G. J. Chem. Soc., Dalton Trans. 1991, 1779. (c) Real, J. A.; Andrés, E.; Muñoz, M. C.; Julve, M.; Granier, T.; Bousseksou, A.; Varret, F. Science 1995, 268, 265. (d) De Munno, G.; Armentano, D.; Poerio, T.; Julve, M.; Real, J. A. J. Chem. Soc., Dalton Trans. 1999, 1813. (e) De Munno, G.; Cipriani, F.; Armentano, D.; Julve, M.; Real, J. A. New J. Chem. 2001, 25, 1031. (f) Shin, D. M.; Lee, I. S.; Cho, D.; Chung, Y. K. Inorg. Chem. 2003, 42, 7722. (g) Wöhlert, S.; Boeckmann, J.; Wriedt, M.; Näther, C. Angew. Chem., Int. Ed. 2011, 50, 6920. (10) Earnshaw, A. Introduction to Magnetochemistry; Academic Press: London, 1968. (11) CrysAlis CCD171 and RED171 Package of Programs; Oxford Diffraction: Oxford, England, 2007. (12) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarazo, G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidore, G.; Spagna, R. J. Appl. Crystallogr. 1999, 32, 115. (13) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (14) Baur, W. H. Acta Crystallogr., Sect. B: Struct. Sci. 1974, 30, 1195. (15) Robinson, K.; Gibbs, G. V.; Ribbe, P. H. Science 1971, 172, 567. (16) (a) Nakamoto, K. Infrared Spectra of Inorganic and Coordination Compounds; John Willey & Sons, 5th ed.; 1997. (b) Pretsch, E.; Clerc, T.; Seibl, J.; Simon, W. Tablas para la Elucidación Estructural de Compuestos Orgánicos por Métodos Espectroscópicos; Alhambra: Barcelona, 1980. (17) Tanabe, Y.; Sugano, S. J. Phys. Soc. Jpn. 1954, 9, 753. (18) Lever, A. B. P. Inorganic Electronic Spectroscopy; Elsevier: London, 1984. (19) Carlin, R. L. Magnetochemistry; Springer-Verlag: Berlin, 1986. (20) Fisher, M. E. Am. J. Phys. 1964, 32, 343. (21) Mabbs, F. E.; Machin, D. J. Magnetism and Transition Metal Complexes; Chapman and Hall: London, 1973.

accommodates different amounts and types of disordered guest molecules. In the case of [Co(NCS)2(DPDS)2]·2H2O (3) and [Fe(NCS)2(DPDS)2]·3H2O (2), the addition of an extra molecule of water reduces the symmetry from Ccc2 to Cc, respectively. The inclusion of the DPDS guest (in its two enantiomer forms M and P) in 1 provokes more drastic changes, lowering the symmetry to P21. However, this symmetry reduction follows an interesting group−subgroup chain Ccc2 > Cc > P21, which establishes a clear structural correlation for further materials design. The thermal variation of the χm−1 and χmT for the three compounds indicates very weak interactions in the manganese compound (1), while slight antiferromagnetic interactions are observed for the iron compound (2) and the cobalt compound (3), in this latter case associated with the spin orbit coupling.

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ASSOCIATED CONTENT

S Supporting Information *

Figures depicting some views of the structures (S1), IR spectra (S2), ESR spectra (S3), magnetic susceptibility (S4−S6), and thermoanalytical data (Table S1), as well as global X-ray crystallographic files, in CIF and check-cif formats. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +34-4-946 013500. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Universidad del Paiś Vasco UPV/EHU (EHU2010/14), the Basque Government SPRISAIOTEK (Project S-PE11UN040), and the Basque Government (Project IT-282-07). N.D.l.P. thanks UPV/EHU for financial support from “Convocatoria para la concesión de ayudas de especialización para investigadores doctores en la UPV/EHU (2008)”.

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REFERENCES

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Guest Driven Structural Correlations in DPDS [Di(4-pyridyl)disulfide

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