Supramolecular networks through second-sphere coordination based on 1D metal-4,4′-dipyridyldisulfide coordination polymers and hydrogenfumarate or sulfonate anions

Polyhedron 31 (2012) 118–127

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Supramolecular networks through second-sphere coordination based on 1D metal-4,40 -dipyridyldisulfide coordination polymers and hydrogenfumarate or sulfonate anions Rosa Carballo ⇑, Nuria Fernández-Hermida, Ana B. Lago, Sabina Rodríguez-Hermida, Ezequiel M. Vázquez-López Departamento de Química Inorgánica, Facultade de Química, Edificio de Ciencias Experimentais, Universidade de Vigo, E-36310 Vigo, Galicia, Spain

a r t i c l e

i n f o

Article history: Received 16 June 2011 Accepted 6 September 2011 Available online 16 September 2011 Keywords: Coordination polymers Metallosupramolecular chemistry Hydrogenfumarate Pyridine-3-sulfonate 4,40 -Dipyridyldisulfide

a b s t r a c t Four hydrogen-bonded assemblies of formula [M(dpds)2(OH2)2]A2nH2O (A = anion) are described. These assemblies result from the second-sphere coordination interactions between the 1D coordination polymers [M(dpds)2(OH2)2]2+, M = Zn(II) and Cu(II), dpds = 4,40 -dipyridyldisulfide, and the pyridine-3-sulfonate (3pySO3) or hydrogenfumarate (Hfum) anions. Significantly, supramolecular structural variations are observed depending on the presence of water lattice molecules, which formed discrete aggregates when the Hfum anion was used. The effects of geometrical variations in the building blocks are also evident on using Jahn–Teller-distorted divalent Cu(II) ions or regular octahedral species based on Zn(II) ions. The second-sphere effects on the stabilization of the compounds are illustrated by TGA experiments. Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction Research into crystal engineering follows two main directions: coordination networks and molecular materials [1]. In the engineering of coordination networks the use of divergent polydentate ligand–metal coordination extends the coordination network through space in 1D, 2D or 3D architectures [2]. On the other hand, in molecular crystal engineering the interactions of interest are mainly of the non-covalent type: i.e., van der Waals, hydrogen bonds, p-stacking, etc. A network material can also be constructed from a combination of coordination bond linkages, which can give rise to discrete coordination compounds or low dimensionality coordination polymers, and non-covalent interactions, which increase the dimensionality of the resulting metallosupramolecular network [3]. In this field, a synthetic strategy that has received little attention is the application of second-sphere coordination to build hydrogen-bonded supramolecular architectures from one-dimensional coordination polymers. Second-sphere coordination refers to any interaction with the primary or first coordination sphere of a ligated metal ion [4] and these systems are particularly important for biological receptors and supramolecular assemblies [4a]. To achieve such metallosupramolecular second-sphere coordination

⇑ Corresponding author. E-mail address: [email protected] (R. Carballo). 0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2011.09.008

systems, some groups in the first-sphere should not only coordinate to the metal center but also bind non-covalently with the external ions [4b–d]. The water molecule can be involved in this type of dual function. Regarding the anions in the second-sphere, the carboxylate and the sulfonate groups are appropriate because they can act as efficient proton acceptors in hydrogen bonding. In the solid state, these kinds of ions can form an intricate network of hydrogen bonds that stabilize the entire lattice. We describe here the formation of metallosupramolecular networks through second-sphere coordination in the four compounds of formula [M(dpds)2(OH2)2]A2nH2O, which contain the one-dimensional cationic coordination polymers [M(dpds)2(OH2)2]2+, M = Zn(II) and Cu(II), dpds = 4,40 -dipyridyldisulfide, and the organic anions (A), 3-pyridine-sulfonate (3pySO3) or hydrogenfumarate (Hfum) (Scheme 1). 4,40 -Dipyridyldisulfide (dpds) is a twisted ligand of the 4,40 -bipyridine type and this has proven to be an interesting tool in the preparation of coordination polymers [5–7], in some cases yielding metallomacrocyclic structures [6,7]. These kind of flexible ligands are of interest for the construction of coordination polymers [8]. A previous investigation into the Zn(II)/dpds/fumaric acid system yielded the neutral coordination polymer [Zn(dpds)(fum)] [7], which contains the dianionic fumarate in the first coordination sphere and the metal center in a tetrahedral coordination geometry. It is interesting to note that one of the preparative methods for the copper(II) compound with hydrogenfumarate involved the metal-assisted intramolecular dehydration of malate.

R. Carballo et al. / Polyhedron 31 (2012) 118–127

119

Scheme 1. Compounds in this work.

2. Experimental 2.1. Materials and physical measurements All starting materials and solvents were obtained commercially and were used as supplied. Elemental analyses (C, H and N) were carried out on a Fisons EA-1108 microanalyser. IR spectra were recorded from KBr discs (4000–400 cm1) on a Bruker Vector 22 spectrophotometer. A Shimadzu UV-3101PC spectrophotometer was used to obtain electronic spectra in the solid state. Magnetic susceptibility measurements were performed at room temperature using a Johnson Matthey Alfa MSB-MK1 Gouy balance. TGA analysis was carried out using a TA Instruments Hi-Res TGA2950 Thermobalance coupled to an FT-IR Bruker Tensor 27 apparatus. Powder X-ray diffraction data were obtained using Cu Ka radiation and were collected on a Siemens D-5000 diffractometer over the range 5.0–30.0° in steps of 0.20° (2h) with a count time per step of 5.0 s. 2.2. Synthesis of the precursors 2.2.1. [Cu(Hfum)2(H2O)2] To a solution of Cu(AcO)2H2O (0.299 g, 2.5 mmol) in H2O (15 mL) was slowly added a solution of fumaric acid (H2fum) (0.580 g, 5 mmol) in MeOH (15 mL). The mixture was stirred for 2 days. The resulting blue precipitate was filtered off, washed with portions of H2O and dried under vacuum. Data: yield: 79%. Anal. Calc. for C8H10O10Cu (329.71): C, 29.1; H, 3.1. Found: C, 28.8; H, 3.1%. 2.2.2. [Cu(Hmal)]2H2O To a suspension of CuCO3Cu(OH)2 (18.410 g, 0.08 mol) in ethanol (20 mL) was slowly added a solution of malic acid (H3mal; 21.454 g, 0.16 mol) in water (28 mL). The mixture was heated under reflux for 11.5 h and was left to cool down to room temperature. The resulting green precipitate was filtered off, washed with water and dried under vacuum. The mother liquor was used as a precursor of copper(II) malate because the green precipitate proved to be highly insoluble. Data: yield: 72%. Anal. Calc. for C4H7O7Cu (230.64): C, 20.8; H, 3.1. Found: C, 19.9; H, 3.1%. 2.2.3. [Zn(fum)(H2O)4]H2O This compound has been described previously in the literature [9] but was obtained by a different synthetic procedure. To a sus-

pension of ZnCO3 (0.629 g, 5 mmol) in H2O (20 mL) was slowly added a solution of fumaric acid (H2fum; 1.161 g, 5 mmol) in MeOH (25 mL). The resulting mixture was stirred at room temperature for several days. The resulting white precipitate was filtered off, washed with water and dried under vacuum. Data: yield: 65%. Anal. Calc. for C4H12O9Zn (269.51): C, 17.8,; H, 4.5. Found: C, 18.5; H, 4.1%. 2.3. Synthesis of the complexes 2.3.1. [Cu(dpds)2(H2O)2](3pySO3)2 (1) A solution of pyridine-3-sulfonic acid (3pySO3H; 0.079 g, 0.50 mmol) in water (2 mL) was slowly added to solution of Cu(AcO)2H2O (0.050 g, 0.25 mmol) in water (3 mL). This mixture was placed in a test tube and a solution of 4,40 -dipyridyldisulfide (dpds; 0.055 g, 0.25 mmol) in ethanol (2 mL) was carefully added. The reagents were allowed to mix slowly by diffusion to form blue crystals of 1. Data: yield: 21%. Anal. Calc. for C30H28N6O8S6Cu (856.49): C, 42.1; H, 3.3; N, 9.8; S, 22.5. Found: C, 41.8; H, 3.3; N, 9.7; S, 22.1%. IR (KBr, cm1): 3452vs,b; 3263s 1593s, 1489w, 1419m, 1231m, 1191s, 1146m, 1045m, 1011m, 814w, 714m, 629m, 497m. UV–Vis at solid state (kmax, cm1): 15 100. l(R.T.): 1.71 lB. 2.3.2. [Zn(dpds)2(H2O)2](3pySO3)22H2O (22H2O) To a suspension of ZnCO3 (0.126 g, 1 mmol) in hot water (10 mL) was slowly added a solution of pyridine-3-sulfonic acid (3pySO3H; 0.318 g, 2 mmol) in water (10 mL). To the resulting solution was added a solution of dpds (0.440 g, 2 mmol) in ethanol (10 mL) and the mixture was stirred at room temperature for 1 week. Colorless single crystals were obtained after the slow evaporation (15 days) of the solution. Data: yield 70%. Anal. Calc. for C30H32S6O10N6Zn (894.36): C, 40.3; H, 3.6; N, 9.4; S, 21.5. Found: C, 40.1; H, 3.4; N, 9.3; S, 21.0%. IR (KBr, cm1): 3421s, 3252s, 1593vs, 1489m, 1420s, 1234s, 1184vs, 1065m, 1042s,1007s, 810s, 714s, 629s, 567m. 2.3.3. [Cu(dpds)2(H2O)2](Hfum)24H2O (34H2O) To a suspension of [Cu(Hfum)2(H2O)2] (0.197 g, 0.6 mmol) in H2O (10 mL) was slowly added a solution of dpds (0.264 g, 1.2 mmol) in ethanol (8 mL). The resulting mixture was heated under reflux for 1 h and was left to cool down to room temperature. The resulting blue precipitate was filtered off, washed with water and dried under vacuum.

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A few single crystals of 34H2O were obtained by slow diffusion of the mother liquor of [Cu(Hmal)]2H2O (3 mL) into a solution of four dpds (0.25 mmol) in ethanol. The spectroscopic data and the powder X-ray diffraction showed that the single crystals are representative of the bulk material. Data: yield 69%. Anal. Calc. for C28H34S4O14N4Zn (842.38): C, 40.0; H, 4.1; N, 6.6; S, 15.2. Found: C, 39.1; H, 3.8; N, 6.1; S, 14.1%. IR (KBr, cm1): 3380m,b; 1637m, 1591s, 1481m, 1416s, 1261m, 1060m, 820m, 717m, 502w. UV–Vis at solid state (kmax, cm1): 15 300. l(R.T.): 2.05 lB. 2.3.4. [Zn(dpds)2(H2O)2](Hfum)25H2O (45H2O) A mixture of [Zn(fum)(H2O)4]H2O (0.136 g, 0.75 mmol) and dpds (0.165 g, 0.75 mmol) in water (6 mL) and dimethylformamide (3 mL) was sealed in a Teflon-lined stainless steel autoclave and heated at 90 °C for 3 h under autogenous pressure and then cooled at a rate 5.83 °C h1. Colorless crystals were isolated after slow evaporation of the solution obtained by filtering off the unidentified white precipitate. Data: yield 14%. Anal. Calc. for C28H36S4O15N4Zn (862.23): C, 39.0; H, 4.2; N, 6.5; S, 15.2. Found: C, 39.1; H, 4.1; N, 6.5; S, 14.5%. IR (KBr, cm1): 3456vs, 1632s, 1589vs, 1483m, 1412m, 1317m, 1259m, 1213m, 1060w, 1001m, 818m, 712m, 497w. 2.4. Crystallography Crystallographic data were collected on a Bruker Smart 1000 CCD diffractometer at 293 K using graphite monochromated Mo Ka radiation (k = 0.71073 Å) and were corrected for Lorentz and polarization effects. The frames were integrated with the Bruker SAINT [10] software package and the data were corrected for absorption using the program SADABS [11]. The structures were solved by direct methods using the program SHELXS97 [12]. All non-hydrogen atoms were refined with anisotropic thermal parameters by full-matrix least-squares calculations on F2 using the program SHELXL97 [13]. Hydrogen atoms were inserted at calculated positions and constrained with isotropic thermal parameters. The hydrogen atoms of the water molecules were located from a difference Fourier map and refined isotropically. In 22H2O and 34H2O the hydrogen atoms for the crystallization water molecules could not be located. In these cases the hydrogen-bonding was inferred by considering the O  O close contacts of water molecules involved [14]. For 45H2O, which crystallized in the polar non-centrosymmetric space group Aba2, refinement of the Flack parameter yielded a value of 0.000(14) [15]. Drawings were produced with MERCURY [16] and special computations for the crystal structure discussions were carried out with PLATON [17]. Crystal data and structure refinement data are listed in Table 1. 3. Results and discussion 3.1. Synthesis The complexes shown in Scheme 1 were obtained by different synthetic procedures. Compound 1H2O was prepared at room temperature by slow diffusion of an ethanol solution of dpds (4,40 -dipyridyldisulfide) into aqueous solutions of pyridine-3-sulfonic acid and Cu(AcO)2H2O in a 1:2:1 molar ratio. The one-pot reaction of ZnCO3 and pyridine-3-sulfonic acid with dpds in a 1:2:2 molar ratio in a H2O/EtOH solution and slow evaporation of the resulting mother liquor yielded compound 22H2O. The preparation of 45H2O could be achieved by a solvothermal procedure at 90 °C, using [Zn(fum)(H2O)4]H2O and dpds in dmf and water. Compound 34H2O was synthesized by reaction of [Cu(Hfum)2(H2O)2] and dpds in a 1:2 molar ratio in H2O/EtOH under reflux,

but a few single crystals of 34H2O were also unexpectedly obtained by slow diffusion of the mother liquor of [Cu(Hmal)]2H2O into an ethanol solution of 4dpds. Such a transformation of malate to fumarate through a copper(II)-assisted dehydration under mild synthetic conditions has not been described frequently in the literature. To the best of our knowledge, only three compounds that show this malate to fumarate transformation have been reported previously: [V(phen)3] (fum)(OH)210H2O [18a] and [Pb2(phen)4(fum)](NO3)2 [18c], both prepared by hydrothermal methods, and [Ag(bpe)]2(fum)9H2O [18b], which was obtained under reflux conditions. 3.2. Spectroscopic studies Infrared spectra of the complexes were recorded in the region 4000–400 cm1 and tentative assignments are made on the basis of earlier reports in the literature [19,20]. The spectra of the four complexes show broad bands in the 3500–3250 cm1 region and these are assigned to overlapping OH stretching vibrations of the coordinated and crystallization water molecules and to m(C–H) bands of the aromatic rings. The presence of the SO3 group in complexes 1 and 22H2O was confirmed by the appearance of characteristic bands close to 1190 cm1, which are assigned to masym (SO2), and around 1010 cm1, which are attributed to msym(SO2). IR spectra of complexes 34H2O and 45H2O show, respectively, strong bands at 1591 and 1589 cm1 and medium intensity bands at 1416 and 1412 cm1, which can be assigned to masym(OCO) and msym(OCO) of the carboxylate group. Other bands in the spectrum in the 1600–1300 cm1 region were tentatively assigned to m(C@C) and m(C@N) of the pyridine ring. The reflectance spectra of copper(II) complexes 1 and 34H2O show a similar pattern and this is consistent with their equivalent coordination sites. Both electronic spectra show an asymmetric broad band centered around 15 000 cm1 and this is attributed to d–d transitions, as expected for octahedral copper(II) complexes. At room temperature the magnetic moment values (1.71 and 2.05 lB) are typical of copper(II) species in which a Cu–Cu interaction does not occur. 3.3. Structural studies The four metal complexes of general formula [M(dpds)2(OH2)2]A2nH2O are based on 1D cationic coordination polymers and an organic anion (pyridine-3-sulfonate or hydrogenfumarate) in the second coordination sphere. Compounds 22H2O, 34H2O and 45H2O also contain lattice water molecules. Selected interatomic distances and angles for the [M(dpds)2(OH2)2]2+ cations are listed in Table 2. A drawing of the coordination environment of the metal cation in 22H2O is shown in Fig. 1, together with the atom numbering scheme used. In all compounds the metal cation is bonded to two trans aqua ligands and four pyridyl nitrogen atoms of two dpds ligands in a slightly distorted octahedral coordination geometry for the Zn(II) compounds and in a tetragonal-bipyramidal geometry for the Cu(II) compounds. The Cu–N and Zn–N distances are in the range 2.020–2.056 Å and 2.159–2.219 Å, respectively. In the two copper(II) compounds the long axial Cu–O distances (2.584 and 2.444 Å, Table 1) are due to the Jahn–Teller effect. In all cases the metal cation is bridged by four dpds ligands to form a doublestranded chain (Fig. 1) that runs along the crystallographic b axis. In this way the two metal cations and two dpds ligands form a metallacycle in which the distances between the metal atoms coincide with the b length of the corresponding unit cell. Each chain and the corresponding metallacyclic cavities are chiral and contain either the M- or the P-form of the enantiomers of dpds. The torsion angles formed by the disulfide moieties are close to 90° (9.3° in 1

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R. Carballo et al. / Polyhedron 31 (2012) 118–127 Table 1 Crystal and structure refinement data. Compound

1

22H2O

34H2O

45H2O

Empirical formula Formula weight Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) b (°) V (Å3) Z T (K) qcalc (g cm3) Absorption coefficient (mm1) F(0 0 0) Crystal size (mm) h Range (°) Reflections collected Independent reflections (Rint) Maximum/minimum transmission Data/restraints/parameters Final R indices [I > 2r(I)]

C30H28N6O8S6Cu 856.48 Monoclinic C2/c

C30H28N6O10S6Zn 890.31 Monoclinic C2/c

C28H28O14N4S4Cu 836.32 Monoclinic C2/c

C28H36O15N4S4Zn 862.22 Orthorhombic Aba2

22.744(2) 10.7218(12) 17.5243(19) 122.457(2) 3605.9(7) 4 293(2) 1.578 1.011 1756 0.32  0.27  0.10 2.12–28.04 11417 4276 (0.0638) 1.0000/0.8538 4276/0/239 R1 = 0.0456 wR2 = 0.0896

17.1425(17) 10.8029(11) 20.442(2) 95.795(2) 3766.2(6) 4 293(2) 1.570 1.047 1824 0.28  0.25  0.16 2.00–28.01 12089 4475 (0.0737) 1.0000/0.8609 4475/0/248 R1 = 0.0538 wR2 = 0.1405

24.729(4) 10.767(2) 16.196 125.779(3) 3498.5(11) 4 293(2) 1.588 0.935 1716 0.22  0.16  0.14 2.03–28.23 9557 3932 (0.0835) 1.0000/0.7140 3932/0/243 R1 = 0.0563 wR2 = 0.0990

21.1044(16) 10.9531(8) 16.1799(12)

68

68

71

Flack parameter KPI (%)

3740.1(5) 4 293(2) 1.531 0.952 1784 0.15  0.25  0.16 1.93–27.98 11563 4354 (0.0430) 1.0000/0.8843 4354/1/270 R1 = 0.0397 wR2 = 0.0725 0.000(14) 69

Table 2 Selected interatomic bond lengths (Å) and angles (°) for the [M(dpds)2(OH2)2]2+ cations. Compound

1 (M = Cu)

22H2O (M = Zn)

34H2O (M = Cu)

45H2O (M = Zn)

M–N1 M–N2 M–O1 M–O2

2.039(3) 2.020(3) 2.584(4)

2.159(4) 2.160(4) 2.146(4)

2.041(4) 2.056(4) 2.444(5)

2.219(3) 2.165(3) 2.126(4) 2.129(4)

O1–M–O1i/O2 N1–M–O1 N1–M–O1i/O2 N2–M–O1 N2–M–O1i/O2 N1–M–N1i N2–M–N1i N2–M–N1 N2–M–N2i

163.38(17) 99.76(13) 92.20(12) 82.78(12) 85.55(13) 88.10(18) 174.63(13) 90.88(12) 90.61(17) i = x, y, z + 1/2

177.8(2) 87.42(17) 91.08(15) 93.97(15) 87.56(17) 91.7(2) 174.89(15) 89.42(14) 90.0(2) i = x, y, z + 1/2

173.1(3) 90.13(18) 85.04(17) 88.66(18) 96.30(18) 91.5(2) 173.43(17) 90.38(16) 88.5(2) i = 1  x, y, z  1/2

180.000(1) 87.48(8) 92.52(8) 91.73(9) 88.27(9) 174.95(17) 90.52(7) 89.63(7) 176.54(18) i = 2  x, 1  y, z

Fig. 1. View of the coordination environment and the one-dimensional structure of [M(dpds)2(OH2)2]2+ in 22H2O.

and 22H2O, 92.2° in 34H2O and 91.5° in 45H2O). Although there are numerous reports on the coordination behavior of dpds [5–7], including some metallacyclic cases [6], we only found a few examples that concern the presence of a similar 1D aqua-metallacycle: [Zn(dpds)2(OH2)2](ClO4)22dpds [6a], [Zn(dpds)2(OH2)2](NO3)2 MeOHH2O [6a] and [Cu(dpds)2(OH2)2](C8H5O4)2H2O, C8H5O4 = hydrogenphthalate, [5]. In the packing of such ionic supramolecular networks the strongest interaction between the cationic units and the anions is the

Coulomb attraction [21]. In the following sections we analyze the main weak interactions in the corresponding supramolecular networks. 3.3.1. Crystal packing in [Cu(dpds)2(H2O)2](3pySO3)2 (1) and [Zn(dpds)2(H2O)2](3pySO3)22H2O (22H2O) The main hydrogen bond distances and angles are listed in Table 3. An initial analysis of the structures of 1 and 22H2O shows the different orientation adopted by the 3pySO3 anions with

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respect to the space defined by the metallacycles in the coordination polymers (Fig. 2). In 1, the pyridine ring of the anion is oriented towards the cavity in the metallacycle in such a way that the cavity is covered on both sides with pyridine rings from two 3pySO3 anions. The interactions involved in this arrangement are weak CHdpds  O and CHdpds  N hydrogen bonds [D  A distances: 3.238(5) and 3.423(6) Å, Table 3]. In 22H2O, the sulfonate groups of the anions are oriented towards the cavity of the metallacycle by means of weak CHdpds  O interactions [D  A distances: 3.423(6) and 3.547(7) Å, Table 3] and anion–p interactions [22] between the sulfonate oxygen atoms O12 and O13 and two pyridine rings from the two dpds ligands in the metallacycle (Fig. 2, top right), with O  centroid distances of 3.231 Å (O13) and 3.636 Å (O12). In 1, the 3pySO3 anions are connected to cationic chains of opposite chirality by means of hydrogen bonds between the aqua ligands and two sulfonate oxygen atoms (Fig. 3, top right), giving rise to a 2D metallosupramolecular organization. The O  O distances for these hydrogen bonds are 2.751(5) and 2.854(5) Å (Table 3). The 3D network is achieved by two CH  O hydrogen bonds: one weak bond (C14–H14  O11) links the 3pySO3 anions in a chain (Fig. 3, bottom left) and the stronger second bond (C7– H7  O13) occurs between the cationic chain and the sulfonate oxygen atom, which is only involved in this interaction. The resulting packing index (KPI) [23] is 68%. Compound 22H2O has lattice water molecules and this changes the packing pattern with respect to that described for 1. The first difference is that the Ow  O hydrogen bonds between the coordinated and uncoordinated water molecules and the sulfonate oxygen atoms (Fig. 4, top right) do not link the cationic chains. The 2D metallosupramolecular organization presents several CH   O and anion–p interactions: the CH  O and anion–p interactions described above, which are responsible for the orientation of the sulfonate group towards the metallacycle cavity, and a third interaction (C15–H15  O11), which organizes the 3pySO3 anions in a chain (Fig. 4, bottom right and Table 3). In this way, each 3pySO3 anion is connected by Ow  O hydrogen bonds to a cationic chain, by CH  O and anion–p interactions with a neighboring cationic chain, and by CH  O hydrogen bonds with two other anions. The resulting 2D arrangement is chiral since the cationic double-chains have the same chirality. The sheets of opposite chirality are further packed by an unusual lone pair–p interaction [24] between the disulfide S2 atom and a pyridine ring of the dpds ligand (Fig. 4, bottom left), with an S2  centroid distance of 3.795 Å and a distance of 3.281 Å separating the S2 atom from the plane of the p ring. The resulting packing index is, as in 1, 68%.

3.3.2. Crystal packing in [Cu(dpds)2(H2O)2](Hfum)24H2O (34H2O) and [Zn(dpds)2(H2O)2](Hfum)25H2O (45H2O) The main hydrogen bond distances and angles are listed in Table 4. The 3D metallosupramolecular networks of the hydrated compounds 34H2O and 45H2O are the result of several hydrogen bonding interactions established between the 1D [M(dpds)2(OH2)2]2+ cations and the corresponding 2D hydrogen-bond-driven water– Hfum anionic layers: {[(Hfum)24H2O]2}n in 34H2O (Fig. 6) and {[(Hfum)25H2O]2}n in 45H2O (Fig. 7). As shown in Fig. 5, in both compounds the water lattice molecules are oriented toward the space defined by the metallacycles and are involved in weak CHdpds  Ow hydrogen bonds with C  O distances between 3.392 and 3.538 Å. Two main differences can be observed between the two cases. Firstly, in 45H2O the coordinated water molecule O2 is hydrogen bonded to the lattice molecule O2w but in 34H2O there is no interaction between the coordinated and the lattice water molecules. Secondly, the water aggregate in 34H2O is linked to cationic chains of opposite chirality whereas in 45H2O a different water aggregate is linked to chains of the same chirality. In both compounds, the water–Hfum anionic layers can be described as the result of the hydrogen bonding association between hydrogenfumarate chains and discrete water aggregates (Figs. 6 and 7). The Hfum anions are arranged in zig-zag chains by means of strong O–H  O hydrogen bonds, with d(O  O) values of 2.521(5) and 2.503(3) Å (Table 4), between the carboxylic and carboxylate groups of the hydrogenfumarate molecules. Closer inspection of the connectivity of the solvent water molecules reveals the presence of different discrete water aggregates in each compound. The study of the structures of the possible water aggregates hosted in coordination compounds is of current interest [21,25]. In 34H2O, the lattice water molecules are associated in isolated R4 [26] cyclic planar tetramers by hydrogen bonding. The O  O distances within the tetramer are 2.645(14) and 2.760(12) Å (average value of 2.703 Å), which are shorter than the value of 2.759 Å in ice Ih at 90 °C [27a]. The intracyclic O  O  O angles are 83.3° and 97.7°. However, in 45H2O the lattice water molecules arrange in discrete D5 [26] acyclic pentamers with O  O distances of 2.706(5) and 2.890(6) Å (average value of 2.798 Å), which are longer than the distances observed in 34H2O but shorter than the value observed in liquid water (2.854 Å) [27b]. In both complexes the discrete water aggregates, which establishes moderate Ow  O hydrogen bonds between the water molecules and the carboxylate groups of the anions, connect the hydrogenfumarate chains to produce water–Hfum layers. The O  O distances range between 2.833 and 3.034 Å in 34H2O and

Table 3 Main hydrogen bond distances (Å) and angles (°) in [Cu(dpds)2(H2O)2](3pySO3)2 (1) and [Zn(dpds)2(H2O)2](3pySO3)22H2O (22H2O). Compound

d(DA)

\(DHA)

O1–H1A  O12i 0.92(5) 1.95(6) O1–H1B  O11ii 0.75(6) 2.02(6) C7–H7  O13iii 0.93 2.32 iv C14–H14  O11 0.93 2.67  Interactions of 3pySO3 with the metallacycle ii C5–H5  O11 0.93 2.52 C9–H9  N12v 0.93 2.69 i = x, y, z + 1/2; ii = x, 2  y, z  1/2; iii = 1/2  x, 3/2  y, 1  z; iv = 1/2  x, 1/2 + y, 3/2  z; v = x, 1  y, 1  z

D–HA

d(D–H)

d(HA)

2.854(5) 2.751(5) 3.211(5) 3.465(6)

167(4) 163(6) 161.4 143.9

3.238(5) 3.423(6)

133.9 136.3

22H2O

2.710(6) 2.723(6) 2.857(7) 3.537(7)

161(5) 170(7) 158

3.423(6) 3.547(7)

140.3 151.8

1

O1–H1A  O1w 0.85(6) 1.89(6) O1–H2A  O11i 0.77(6) 1.97(6) O1w  O12i iii C15–H15  O11 0.93 2.66 Interactions of 3pySO3 with the metallacycle C8–H8  O13 0.93 2.66 C4–H4  O13ii 0.93 2.70 i = x + 1/2, y  1/2, z + 1/2; ii = x, y  1, z + 1/2; iii = ½  x, 1/2 + y, 1/2  z; iv = x, 1  y, z  1/2

R. Carballo et al. / Polyhedron 31 (2012) 118–127

123

Fig. 2. Main interactions of 3PySO3 anions with the metallacycles in [Cu(dpds)2(H2O)2](3pySO3)2 (1) and [Zn(dpds)2(H2O)2](3pySO3)22H2O (22H2O). Top view for each compound shows the interactions with only one anion.

Fig. 3. 3D metallosupramolecular network in 1. View of the main hydrogen bonding interactions involving the 3pySO3 anion.

between 2.781 and 2.819 Å in 45H2O. The hydrogen bonding interactions in the water–Hfum layers produce different sizes of cycles in each case: in 34H2O 26-membered cycles and 9-membered cycles can be described (Fig. 6) whereas in 45H2O three small kinds of cycles with 8, 10 and 12 members are observed. Another difference between the two water–Hfum layers was found on analyzing their linkage with the cationic chains: in 34H2O the R4 aggregate does not interact with the coordinated water molecules but in 45H2O the D5 aggregate does establish this kind of interaction – as mentioned earlier. The structural diversities of the water aggregates could be due to the differences in the octahedral coordination geometries in each case. The more regular octahedron around Zn(II) in 45H2O seems to promote a linear water array, thus allowing the formation of coordinated water–lattice water hydrogen bonding, whereas the

tetragonal-bipyramid around Cu(II) in 34H2O facilitates the hydrogen bonding interaction of the coordinated water molecule with the deprotonated carboxylate group of the hydrogenfumarate anion, a situation that leads the lattice water molecules to form a cyclic array that is entrapped in the dianionic layer. The linkage between the cationic chains and the dianionic layers is based on OH  OHfum hydrogen bonds between the coordinated water molecules and the deprotonated carboxylate group of the hydrogenfumarate anions. In 45H2O there is also an OH(coordinated water)  Owlattice interaction. In both compounds the resulting 3D networks are also stabilized by the contribution of several CH  O hydrogen bonds involving the CHdpds as donors and the lattice water molecules, the carboxylate and the carboxylic groups of the hydrogenfumarate anions as acceptors. The C  O distances for these interactions are in the range 3.213–3.538 Å (Table

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Fig. 4. 3D metallosupramolecular network in 22H2O. View of the main interactions.

Table 4 Main hydrogen bond distances (Å) and angles (°) in [Cu(dpds)2(H2O)2](Hfum)24H2O (34H2O) and [Zn(dpds)2(H2O)2](Hfum)25H2O (45H2O). Compound

D–HA

34H2O

Interactions in 2D {[(Hfum)24H2O]2}n O1w  O2w O1w  O2wiv Ow1  O1w O2w  O13 O1w  O13iv O12–H12A  O14vi 0.89(6)

d(D–H)

d(HA)

d(DA)

\(DHA)

1.64(6)

2.760(12) 2.645(14) 2.906(9) 3.034(10) 2.833(9) 2.521(5)

169(6)

2.810(7) 2.813(6) 3.392(10) 3.538(11) 3.213(6) 3.471(7)

161(6) 175(8) 145.4 160.5 110.4 151.7

2.706(5) 2.890(6) 2.819(4) 2.781(4) 2.803(4) 2.503(3) 3.430(4)

158(4) 157(6) 171(5) 167(4) 161(4) 162(5) 156.0

Interactions between the cationic chain and 2D {[(Hfum)24H2O]2}n O1–H1A  O13v 0.74(5) 2.10(5) O1–H1B  O14i 0.76(6) 2.06(6) C4–H4  O2wvi 0.93 2.59 vi C5–H5  O1w 0.93 2.65 v C2–H2  O11 0.93 2.77 vii C9–H9  O14 0.93 2.62 i = 1  x, y, z  ½; iv = 1  x, 2  y, z  1; v = x, 1  y, z + 1/2; vi = x + 3/2, y + 1/2, z  1/2; vii = x, y, z + 1/2 45H2O

Interactions in 2D {[(Hfum)25H2O]2}n O2w–H2wA  O1wii 0.85(4) O3w–H3wA  O2w 0.76(5) iii O2w–H2wB  O6 0.91(6) O1w–H1wA  O4iv 0.92(4) O1w–H1wB  O3 0.99(4) O5–H5A  O4iii 0.89(5) C12–H12  O6vi 0.93

1.90(4) 2.17(5) 1.92(6) 1.88(5) 1.85(5) 1.64(5) 2.56

Interactions between the cationic chain and 2D {[(Hfum)25H2O]2}n O2–H2A  O2w 0.81(3) 1.93(4) 2.734(4) O1–H1A  O3i 0.77(3) 1.98(3) 2.744(3) v C4–H4  O5 0.93 2.59 3.420(4) i C5–H5  O4 0.93 2.63 3.486(5) C9–H9  O3wv 0.93 2.56 3.430(4) i = x + 3/2, y + 1, z  1/2; ii = x + 1/2, y + 1/2, z; iii = x + 3/2, y + 1/2, z; iv = x + 1, y  1, z; v = x, y + 1/2, z  1/2; vi = x + 3/2, y  1/2, z

170(4) 172(4) 148.9 152.5 156.0

R. Carballo et al. / Polyhedron 31 (2012) 118–127

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Fig. 5. View of the interactions of the lattice water molecules with the metallacycles in [Cu(dpds)2(H2O)2](Hfum)24H2O (34H2O) and [Zn(dpds)2(H2O)2](Hfum)25H2O (45H2O).

Fig. 6. 3D metallosupramolecular network in 34H2O. View of the {[(Hfum)24H2O]2}n layer and R4 water aggregate and the main interactions.

4). The resulting packing indexes (KPI) [23] are 71% for 34H2O and 69% for 45H2O. 4. Thermal studies In an effort to understand the thermal stability of the title complexes, thermogravimetric analyses (TGA) were carried out. In com-

pounds 1, 22H2O and 34H2O the thermal decomposition occurs in three steps, whereas in 45H2O there are four stages. The initial weight loss temperature for 34H2O and 45H2O, which contain the water aggregates, is somewhat lower than those for 1 and 22H2O, which does not contains lattice water (1) or contains isolated lattice water (22H2O). For compound 1 the initial mass loss of 4.5% between room temperature and 146 °C corresponds to the

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Fig. 7. 3D metallosupramolecular network in 45H2O. View of the {[(Hfum)25H2O]2}n layer and D5 water aggregate and their main interactions.

release of the two aqua ligands (calc. 4.2%). The second weight loss of 37.3%, which ends at 327 °C, is consistent with the loss of the two 3pySO3 anions (calc. 36.9%). The final step, which extends up to 585 °C, involves the decomposition of the dpds ligand. The first step for 22H2O (8.3%, R.T. to 147 °C) involves the loss of all coordinated and lattice water molecules (calc. 8.1%). The release of only one 3pySO3 anion (calc. 17.7%) occurs in a second step (18.4%, 292 °C) and the other 3pySO3 anion, together with dpds, is lost in a final step, which ends at 742 °C. In the fumarate complexes, the first step (9.9%, R.T. to 131 °C for 34H2O and 13%, R.T. to 120 °C for 45H2O) corresponds to the loss of the four lattice water molecules in 34H2O (calc. 8.5%) and to the loss of all the lattice water molecules and most of the aqua ligands in 45H2O (calc. for 6.5 water molecules, 13.5%). The second step in 34H2O (32.7%, 196 °C) is consistent with the loss of two hydrogenfumarate anions and the two coordinated water molecules (calc. 31.4%), whereas in 45H2O (13.9%, 188 °C) this corresponds to the release of one hydrogenfumarate anion and the remaining water molecules (calc. 14.4%). The last stage for 34H2O, which ends at 740 °C, involves total decomposition of the sample. In 45H2O, a third step (24.4%, 263 °C) is consistent with the loss of the second hydrogenfumarate anion and half a dpds molecule (calc. 26%), while total decomposition occurs in a fourth stage that ends at 702 °C. 5. Conclusions Four metallosupramolecular networks have been constructed by the combination of 1D copper(II) and zinc(II) cationic coordination polymers containing the bridging ligand 4,40 -dipyridyldisulfide and a second-sphere coordination based on pyridine-3-sulfonate or hydrogenfumarate anions. The pyridin-3-sulfonate compounds do not contain lattice water or only isolated lattice water molecules. The anions are CH  O hydrogen bonded to give chains in such a way that the anion guides the pyridine part or the sulfonate group towards the metallacycle in the cationic polymers in a different way depending on the presence of lattice water molecules. The hydrogenfumarate compounds contain discrete lattice water molecules and these form aggregates, R4 or D5, that are

hydrogen bonded to the hydrogenfumarate anions to give dianionic {[(Hfum)2nH2O]2}n layers. The different degree of distortion of polyhedron around the Cu(II) or Zn(II) ions seems to be determinant in the crystal packing. For example, the tetragonal-bipyramidal polyhedra around the Cu(II) ions facilitate the interactions of the coordinated water molecules with the 3pySO3 or Hfum anions whereas the regular octahedron around the Zn(II) ions promotes the interaction between the coordinated and lattice water molecules. The contribution of the weak interactions in all cases leads to efficient packing and thermally stable systems. These complexes illustrate the utility of second-sphere effects, both as an assembly tool and to stabilize metal complexes in the solid state. Acknowledgements Financial support from the Xunta de Galicia (Spain) (research project 10TMT314002PR) is gratefully acknowledged. A.B.L. thanks the Xunta de Galicia for a post-doctoral contract under the ‘‘Ángeles Alvariño’’ Program. Appendix A. Supplementary data CCDC 829905–82998 contain the supplementary crystallographic data for 1, 22H2O, 34H2O and 34H2O. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/ retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336033; or e-mail: [email protected]. References [1] (a) D. Braga, L. Brammer, N.R. Champness, CrystEngComm 7 (2005) 1; (b) C.B. Aakeröy, N.R. Champness, C. Janiak, CrystEngComm 12 (2010) 22. [2] S.R. Batten, J. Solid State Chem. 178 (2005) 2475. [3] (a) C.-L. Chen, A.M. Beatty, J. Am. Chem. Soc. 130 (2008) 17222; (b) A-C. Chamayou, C. Janiak, Inorg. Chim. Acta 363 (2010) 2193. [4] (a) S.J. Loeb, in: J.L. Atwood, J.E.D. Davies, D.D. MacNicol, F. Vögtle (Eds.), Comprehensive Supramolecular Chemistry, vol. 1, Elsevier Science, New York, 1996, p. 733; (b) M. Botta, Eur. J. Inorg. Chem. (2000) 399;

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