Unsubstituted and substituted copper malonate coordination polymers with isomeric dipyridylamide ligands: Chain, layer, diamondoid, and self-penetrated topologies

Inorganica Chimica Acta 446 (2016) 176–188

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Unsubstituted and substituted copper malonate coordination polymers with isomeric dipyridylamide ligands: Chain, layer, diamondoid, and self-penetrated topologies Brandon S. Stone, Richard J. Staples, Robert L. LaDuca ⇑ Lyman Briggs College and Department of Chemistry, Michigan State University, East Lansing, MI 48825 USA

a r t i c l e

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Article history: Received 26 January 2016 Received in revised form 7 March 2016 Accepted 11 March 2016 Available online 19 March 2016 Keywords: Copper Crystal structure Coordination polymer Self-penetration Ferromagnetism

a b s t r a c t Six dual-ligand divalent copper malonate coordination polymers have been prepared via solvent diffusion methods, and structurally characterized by single-crystal X-ray diffraction. The resulting dimensionality and topology depend crucially on the steric bulk of the malonate ligand and the nitrogen donor disposition within the dipyridylamide coligand. {[Cu(mal)(3-pina)(H2O)]
2H2O}n (1, mal = malonate, 3pina = 3-pyridylisonicotinamide) possesses a simple 1-D chain structure, while the isomeric 4-pyridylnicotinamide (4-pna) ligand afforded a two-fold interpenetrated (6,3) grid layer structure in {[Cu(mal) (4-pna)(H2O)]
3H2O}n (2). Employing copper dimethylmalonate (dmmal) in the synthetic regime permitted synthesis of the (4,4) grid layered phase {[Cu2(dmmal)2(4-pna)2(H2O)3]
7H2O}n (3) and {[Cu2(dmmal)2(3-pina)2]
9.5H2O}n (4), which exhibited a three-fold interpenetrated diamondoid net with large water-filled incipient channels, built from [Cu4(dmmal)4] tetranuclear clusters. {[Cu2(Hdmmal)2(dmmal) (4-pina)2]
0.5H2O}n (5, 4-pina = 4-pyridylisonicotinamide) manifested a unique 5-connected self-penetrated 3D network with 42678 topology. {[Cu(emal)(4-pna)(H2O)]
3H2O}n (6, emal = ethylmalonate) is another simple 1-D chain phase. Ferromagnetic coupling (J = 11(3) cm1) was observed within the tetranuclear clusters in 4. Thermal properties of these materials are also presented. Ó 2016 Elsevier B.V. All rights reserved.

1. Introduction The exploratory synthesis and structural characterization of crystalline coordination polymers remain under intense study because of their intrinsic basic research appeal in addition to their numerous capabilities in hydrogen storage [1], molecular separations [2], ion exchange [3], heterogeneous catalysis [4], non-linear optics [5], and magnetic applications [6]. Although aromatic dicarboxylate ligands are frequently used as linkers in this class of materials, more recent attention has been focused on aliphatic dicarboxylate coordination polymers in order to probe the structural effects of ligands with greater conformational degrees of freedom [7–10]. Complicated, synergistic interactions between aliphatic ligand conformation, carboxylate binding mode, metal coordination geometry preference, and the presence of any neutral dipyridyl-type linkers have been shown to result in a plethora of possible molecular topologies during coordination polymer selfassembly. ⇑ Corresponding author at: Lyman Briggs College, E-35 Holmes Hall, 919 East Shaw Lane, Michigan State University, East Lansing, MI 48825 USA. E-mail address: [email protected] (R.L. LaDuca). http://dx.doi.org/10.1016/j.ica.2016.03.015 0020-1693/Ó 2016 Elsevier B.V. All rights reserved.

Divalent copper malonate (mal, Scheme 1) coordination polymers containing ancillary tethering ligands have proven to be an especially rich system both in terms of topological diversity and magnetic properties, very often critically depending on the length and hydrogen-bonding facility of the dipyridyl component [7–10]. The layered phase [Cu2(mal)2(H2O)2(bpy)]n (bpy = 4,40 -bipyridine) manifests ferromagnetic [Cu4(mal)4] tetrameric squares with anti-syn bridging carboxylates, linked by rigid-rod bpy tethers [7]. The related, kinked ‘‘V-shaped” tethering ligand 4,40 -dipyridylamine (dpa) resulted another 2-D phase, {[Cu2(mal)2(dpa)(H2O)2]
H2O}n [8]. This material possessed crystallographically distinct [Cu (mal)]n chain motifs, with anti-anti carboxylate bridging in one and anti-syn in the other. Net weak ferromagnetism was observed, although the magnetic effect of each chain motif could not be appropriately separated. Use of the longer-spanning ligand 1,2-di (4-pyridyl)ethane (dpe) afforded the coordination polymer [{Cu3(mal)2(dpe)3(H2O)2}(NO3)2
2H2O]n, which displayed a 4,6connected 3-D topology and weak ferromagnetic coupling between anti-syn carboxylate bridged copper ions [9]. In contrast, {[Cu(dpp) (mal)(H2O)]
4H2O}n (dpp = 1,3-di(4-pyridyl)propane) had a simple chain structure with bridging dpp ligands and non-bridging 1,3chelating capping malonate ligands [10].

B.S. Stone et al. / Inorganica Chimica Acta 446 (2016) 176–188

Scheme 1. Ligands used in this study.

Compared to divalent copper malonate/dipyridyl coordination polymers, those containing substituted malonate ligands such as methylmalonate (mmal), dimethylmalonate (dmmal, Scheme 1) or ethylmalonate (emal, Scheme 1) are less common [11–14]. In some cases, these ligands can induce synthetic condition-dependent structural and magnetic diversity. {[Cu(bpy)2] [Cu(bpy)2(mmal) (NO3)(H2O)](NO3)
3.5H2O}n exhibits [Cu(bpy)2]n2n+ square grid motifs pillared by mmal ligands into a 3-D 41263 pcu net [11]. Net antiferromagnetism was observed, produced by concomitant ferromagnetic and antiferromagnetic interactions across different mmal carboxylate binding modes. A chain polymer [Cu(bpy)2(mmal) (H2O)]
H2O}n showed extremely weak antiferromagnetic coupling via the full span of the mmal ligands instead of a single carboxylate group [11]. A third analog, [Cu2(bpy)(mmal)2(H2O)2]n, has a 3-D structure built from Cu(mmal) corrugated layers linked by bpy rigid rod tethers [12]; this material exhibits ferromagnetic coupling mediated by anti-syn carboxylate bridges. Deliberate use of sterically bulky substituted malonate ligands also greatly altered the resulting coordination polymer topology in dpa-containing phases. In contrast to the layered topology seen with the unsubstituted malonate ligand, {[Cu(mmal)(Hmmal) (Hdpa)]
H2O}n displays chain motifs containing antiferromagnetically coupled anti-syn briged [Cu(OCO)]n linkages [13]. Here the pendant, monodentate protonated dipyridyl ligands do not provide access to higher dimensionality. The dmmal derivative {[Cu3(dmmal)2(dpa)3](ClO4)2
2H2O}n has a structure built from antiferromagnetically coupled trimeric units, connected by the kinked dipyridyl tethers into a (4,5)-connected (4462)(4664)2 gaf network topology [13]. The longer, more flexible tethering ligand 1,3-di(4-pyridyl)propane (dpp) afforded three copper malonate phases whose topology depended critically on the steric bulk of the dicarboxylate backbone [14]. With the unsubstituted parent mal ligand, {[Cu(dpp)2 (H2O)] [Cu(mal)2(dpp)][Cu(mal)(dpp)(H2O)]
12H2O}n was obtained [14]. The structure of this phase shown an interweaving of cationic layer, anionic chain, and neutral chain motifs in a rare 2D + 1D + 1D ? 3D topology. The sterically bulkier dmmal ligand afforded [Cu(dmmal)(dpp)(H2O)]
3H2O}n, which exhibited a standard (4,4) grid topology. The emal derivative [Cu(dpp)2][Cu(emal)2]
6H2O}n manifests cationic 1-D ribbon motifs and coordination complex counteranions. To date no copper unsubstituted or substituted malonate coordination polymer phases have been reported, that contain any of the series of isomeric dipyridylamides depicted in Scheme 2: 3-pyridylnicotinamide (3-pna), 3-pyridylisonicotinamide (3-pina), 4-pyridylnicotinamide (4-pna), or 4-pyridylisonicotinamide (4-pina). Unlike bpy, dpe, or dpp, these dipyridylamide ligands

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all possess internal hydrogen bonding donor and acceptor groups at their central linkages, providing another potential avenue for structure direction during self-assembly. There have been relatively few reports of coordination polymers containing these isomeric dipyridylamides, but these can show great variance in topology across the series while retaining the same metal and carboxylate component [15–18]. For instance, [Cd(suc)(4-pina)]n displays a 3-D self-penetrated 446108 mab topology, while {[Cd(suc) (3-pna)]
2.5H2O}n (2, 3-pna = 3-pyridylnicotinamide) has a simple 3-D non-interpenetrated 41263 pcu network [15]. While both {[Cd(suc)(4-pna)(H2O)]
2H2O}n and {[Cd(suc)(3-pina)(H2O)]
3.5H2O}n have 2-D topologies, the former is an extremely rare example of a 4-connected 66 self-penetrated layer topology, while the latter has a common (4,4) grid layer structure [15]. We thus sought to prepare a series of copper malonate coordination polymers containing 3-pna, 3-pina, 4-pna, and 4-pina, hoping to probe structure-directing trends imparted by both the nitrogen donor disposition within the dipyridylamide component and the steric load borne by the malonate component. Our synthetic explorations resulted in the successful preparation and structural characterization of six new crystalline solids: {[Cu(mal)(3-pina)(H2O)]
2H2O}n (1), {[Cu(mal)(4-pna)(H2O)]
3H2O}n (2), {[Cu2(dmmal)2(4-pna)2 (H2O)3]
7H2O}n (3), {[Cu2(dmmal)2(3-pina)2]
9.5H2O}n (4), {[Cu2 (Hdmmal)2(dmmal)(4-pina)2]
0.5H2O}n (5), and {[Cu(emal)(4-pna) (H2O)]
3H2O}n (6). The variable temperature magnetic properties of 4, along with the thermal properties of all six new phases, are also reported herein. 2. Experimental 2.1. General considerations Copper carbonate, malonic acid, dimethylmalonic acid, and ethylmalonic acid were purchased commercially. Copper malonate was prepared by a published procedure [19]; the other copper dicarboxylate precursors were prepared similarly by employing the requisite dicarboxylic acid instead of malonic acid. The dipyridylamides 3-pina, 4-pna, and 4-pina were prepared by a published procedure [20]. Water was deionized above 3 MX-cm in-house. IR spectra were recorded on powdered samples using a Perkin Elmer Spectrum One instrument. Thermal degradation analysis was performed under flowing N2 on a TA Instruments Q50 Thermogravimetric Analyzer with a heating rate of 10 °C/min up to 600 °C. Variable temperature magnetic susceptibility data for 4 (2–300 K) were collected on a Quantum Design MPMS SQUID magnetometer at an applied field of 0.1 T. After each temperature change the sample was kept at the new temperature for five minutes before magnetization measurement to ensure thermal equilibrium. The susceptibility data was corrected for diamagnetism using Pascal’s constants [21], and for the diamagnetism of the sample holder. Elemental Analysis was carried out using a Perkin Elmer 2400 Series II CHNS/O Analyzer. 2.2. Preparation of {[Cu(mal)(3-pina)(H2O)]
2H2O}n (1) Copper malonate (15 mg, 0.091 mmol) was dissolved in 3 mL water in a 15 mL glass vial. A 2 mL aliquot of a 1:1 water:ethanol solution was placed on top of the copper malonate solution via pipette, followed by a solution of 3-pina (19 mg, 0.095 mmol) in 3 mL ethanol. The vial was allowed to stand undisturbed at 25 °C for 14 d. Blue blocks of 1 (32 mg, 84% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. Anal. Calc. for C14H17CuN3O8 1: C, 40.15; H, 4.09; N, 10.03. Found: C, 40.21; H, 3.67; N, 9.96%. IR (cm1): 3199 (w), 1674 (m), 1644 (m), 1612 (s), 1553 (s), 1487 (s), 1420 (s), 1339 (m), 1314 (m),

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1272 (m), 1237 (m), 1195 (m), 1159 (w), 1110 (w), 1064 (w), 1031 (w), 962 (w), 944 (w), 921 (w), 909 (w), 828 (w), 811 (m), 757 (w), 717 (w), 696 (s).

(m), 1416 (m), 1334 (m), 1311 (m), 1211 (m), 1119 (m), 1059 (m), 1027 (m), 953 (m), 842 (m), 794 (m). 3. X-ray crystallography

2.3. Preparation of {[Cu(mal)(4-pna)(H2O)]
3H2O}n (2)

The synthesis of 3 proceeded similarly to that of 2, with the use of copper dimethylmalonate (18 mg, 0.094 mmol) as the metal carboxylate component. Blue blocks of 3 (25 mg, 57% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. Anal. Calc. for C32H50Cu2N6O20 3 (with loss of three molar equivalents of water on standing): C, 42.15; H, 4.86; N, 9.22. Found: C, 42.61; H, 4.74; N, 8.93%. IR (cm1): 3411 (w), 1622 (m), 1601 (s), 1586 (s), 1533 (m), 1519 (m), 1467 (m), 1431 (m), 1401 (m), 1349 (m), 1326 (s), 1307 (s), 1281 (m), 1213 (m), 1119 (m), 1060 (w), 885 (w), 839 (s), 765 (w).

Single crystal X-ray diffraction was performed using a BrukerAXS ApexII CCD instrument at 173 K. Reflection data were acquired using graphite–monochromated Mo Ka radiation (k = 0.71073 Å) with the exception of the data for 5, which was acquired using graphite–monochromated Cu Ka radiation (k = 1.54178 Å). The data was integrated via SAINT [22]. Lorentz and polarization effect and empirical absorption corrections were applied with SADABS [23]. The structures were solved using direct methods and refined on F2 using SHELX [24] subroutines within the OLEX2 crystallographic suite [25]. The crystal of 2 was non-merohedrally twinned; its twin law was found using CELL NOW [26]. For 2, the structure was refined using only the reflections from the major twin component. All non-hydrogen atoms were refined anisotropically. Due to the loss of water molecules of crystallization of 4 upon standing, the crystal of 4 used for single crystal diffraction was harvested directly out of its mother liquor. Hydrogen atoms bound to carbon, nitrogen, or oxygen atoms were placed in calculated positions and refined isotropically with a riding model. The central amide group of the 4-pina ligands in 5 is disordered across two sets of positions in a 75:25 ratio. Disordered water molecules were treated with partial occupancies; not all hydrogen atoms on these water molecules could be reliably calculated or found. The ethylmalonate ligand in 6 was disordered equally over two sets of positions and were acceptably modeled using partial occupancies. Relevant crystallographic data for 1–6 are listed in Table 1.

2.5. Preparation of {[Cu2(dmmal)2(3-pina)2]
9.5H2O}n (4)

4. Results and discussion

The synthesis of 4 proceeded similarly to that of 3, with the use of 3-pina (19 mg, 0.095 mmol) as the dipyridylamide component. Blue blocks of 4 (12 mg, 28% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. Anal. Calc. for C32H49Cu2N6O19.5 4 (with loss of 8.5 molar equivalents of water on standing for 30 d): C, 46.82; H, 4.01; N, 10.46. Found: C, 47.26 H, 3.45; N, 9.89%. IR (cm1): 3264 (w), 1281 (w), 1671 (w), 1624 (w), 1613 (w), 1547 (s), 1480 (m), 1459 (m), 1426 (m), 1368 (m), 1325 (m), 1293 (m), 1246 (m), 1227 (m), 1193 (m), 1110 (w), 1064 (m), 1006 (w), 962 (w), 942 (w), 895 (m), 862 (w), 846 (w), 807 (m), 753 (m), 693 (s).

4.1. Synthesis and spectral characterization

The synthesis of 2 proceeded similarly to that of 1, with the use of 4-pna (19 mg, 0.095 mmol) as the dipyridylamide component. Blue blocks of 2 (12 mg, 30% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. The resulting crystals turn to a blue powder upon standing for 24 h. Anal. Calc. for C14H19CuN3O9 with loss of two molar equivalents of water 2: C, 41.95; H, 3.77; N, 10.48. Found: C, 42.09; H, 3.64; N, 10.73 %. IR (cm1): 3071 (w), 1679 (w), 1595 (s), 1561 (s), 1516 (s), 1429 (s), 1380 (m), 1334 (s), 1302 (s), 1210 (m), 1117 (m), 1071 (w), 1057 (w), 1030 (m), 959 (w), 897 (w), 830 (w), 730 (m), 698 (s). 2.4. Preparation of {[Cu2(dmmal)2(4-pna)2(H2O)3]
7H2O}n (3)

2.6. Preparation of [Cu2(Hdmmal)2(dmmal)(4-pina)2]
0.5H2O}n (5) The synthesis of 5 proceeded similarly to that of 3, with the use 4-pina (18 mg, 0.095 mmol) as the dipyridylamide component. Blue blocks of 5 (12 mg, 29% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. Anal. Calc. for C37H39Cu2N6O14.5 5: C, 47.53; H, 4.21; N, 8.99. Found: C, 47.55; H, 4.16; N, 9.14%. IR (cm1): 3547 (w), 2963 (w), 1684 (m), 1550 (s), 1519 (s), 1445 (m), 1427 (m), 1385 (m), 1335 (m), 1306 (m), 1289 (s), 1213 (m), 1124 (m), 1069 (m), 1031 (m), 989 (w), 906 (w), 845 (s), 815 (s), 758 (s), 707 (m), 691 (m).

Compounds 1–6 were prepared as crystalline products by slow diffusion of ethanolic solutions of the requisite dipyridylamide isomer into aqueous solutions of copper malonate (1–2), copper dimethylmalonate (3–5), or copper ethylmalonate (6). The infrared spectra of 1–6 were consistent with their structural characteristics as determined by single-crystal X-ray diffraction. Medium intensity bands in the range of 1600 cm1 to 1200 cm1 can be ascribed to stretching modes of the pyridyl rings within the ligands. Puckering modes of the pyridyl rings in the dipyridylamide ligands are evident in the region between 820 cm1 and 600 cm1. Asymmetric and symmetric C–O stretching bands were evident at 1553 cm1 and 1420 cm1 (for 1), 1595 cm1 and 1429 cm1 (for 2), 1586 cm1 and 1401 cm1 (for 3), 1547 cm1 and 1426 cm1 (for 4), 1550 cm1 and 1385 cm1 (for 5), and 1568 cm1 and 1416 cm1 (for 6). The carbonyl stretching bands for the dipyridylamide ligands were seen as a sharp features at 1674 cm1 (1), 1679 cm1 (2), 1700 cm1 (3), 1671 cm1 (4), 1684 cm1 (5), and 1687 cm1 (6). Broad features in the vicinity of 3200 cm1 in all cases represent the O–H stretching bands for the aqua ligands and water molecules of crystallization (and the protonated carboxylate groups in 5) and also the N–H bonds within the dipyridylamide ligands.

2.7. Preparation of {[Cu(emal)(4-pna)(H2O)]
3H2O}n (6) 4.2. Structural description of {[Cu(mal)(3-pina)(H2O)]
2H2O}n (1) The synthesis of 6 proceeded similarly to that of 3, with copper ethylmalonate used as the metal carboxylate component. Blue blocks of 6 (18 mg, 43% yield based on Cu) were isolated after washing with distilled water and acetone and drying in air. Anal. Calc. for C16H23CuN3O9 6: C, 41.33; H, 4.99; N, 9.04. Found: C, 41.01; H, 4.57; N, 8.76%. IR (cm1): 3264 (m), 1687 (m), 1568

The asymmetric unit of compound 1 contains a divalent copper atom, a mal ligand, a 3-pina ligand, an aqua ligand, and two water molecules of crystallization, one of which is disordered over two sets of positions. The copper coordination environment is a {CuN2O3} square pyramid (Fig. 1a), with a slight distortion from idealized

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B.S. Stone et al. / Inorganica Chimica Acta 446 (2016) 176–188 Table 1 Crystal and structure refinement data for 1–6. Data

1

2

3

Empirical formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) l (mm1) Minimum/maximum trans. hkl ranges

C14H17CuN3O8 418.85 monoclinic P21/c 11.7155(9) 11.3774(19) 12.223(2) 90 95.290(2) 90 1622.2(5) 4 1.715 1.398 0.8907 14 6 h 6 14, 13 6 k 6 13, 13 6 l 6 14 13 016 2990 0.0842 251 0.0958 0.0590 0.1596 0.1407 0.827/0.463 1.049

C14H19CuN3O9 436.86 monoclinic C2/c 18.451(3) 8.7146(16) 21.401(4) 90 91.554(3) 90 3440.0(11) 8 1.687 1.327 0.8846 22 6 h 6 22, 0 6 k 6 10, 0 6 l 6 25 41 866 3170 0.1047 254 0.0665 0.0414 0.0904 0.0898 0.380/0.373 1.043

C32H50Cu2N6O20 965.86 monoclinic C2/c 11.9270(11) 14.1906(14) 24.610(2) 90 93.059(1) 90 4159.3(7) 4 1.542 1.109 0.9333 12 6 h 6 14, 17 6 k 6 17, 29 6 l 6 28 19 361 3802 0.0470 292 0.0428 0.0330 0.0855 0.0803 0.383/0.357 1.052

4

5

6

C32H49Cu2N6O19.5 956.85 monoclinic C2/c 39.900(4) 9.9925(9) 28.728(3) 90 133.799(1) 90 8267.2(13) 8 1.538 1.114 0.8783 46 6 h 6 48, 12 6 k 6 11, 34 6 l 6 34 36 009 7630 0.0407 575 0.0640 0.0506 0.1309 0.1222 1.104/0.601 1.067

C37H39Cu2N6O14.5 926.82 monoclinic C2/c 15.6449(2) 21.5544(3) 13.2606(2) 90 90.815(1) 90 4471.24(11) 4 1.377 1.766 0.8895 19 6 h 6 19, 26 6 k 6 26, 16 6 l 6 16 27 875 4359 0.0505 297 0.0702 0.0595 0.1874 0.1772 1.038/0.457 1.125

C16H23CuN3O9 464.91 orthorhombic Pbca 11.3072(5) 17.6841(9) 19.5718(9) 90 90 90 3913.5(3) 8 1.578 1.171 0.8898 13 6 h 6 13, 21 6 k 6 21, 23 6 l 6 23 38 000 3582 0.1055 283 0.0806 0.0411 0.1027 0.0852 0.439/0.405 1.009

Total reflections Unique reflections Rint Parameters R1 (all data) R1 (I > 2r(I)) wR2 (all data) wR2 (I > 2r(I)) Maximum/minimum residual(e/Å3) Goodness-of-fit (GOF)

Empirical formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) l (mm1) Minimum/maximum trans. hkl ranges Total reflections Unique reflections Rint Parameters R1 (all data) R1 (I > 2r(I)) wR2 (all data) wR2 (I > 2r(I)) Maximum/minimum residual (e/Å3) Goodness-of-fit (GOF)

geometry as marked by a s factor [27] of 0.096. A mal ligand with a 1,3-chelating binding mode occupies two cis basal positions. The other two cis basal sites are taken up by a 3-pyridyl nitrogen donor atoms from one 3-pina ligand and an isonicotinamide pyridyl nitrogen donor atom from another. The aqua ligand occupies the Jahn–Teller elongated axial position. Bond lengths and angles within the square pyramidal coordination sphere are listed in Table 2. Dipodal 3-pina ligands connect [Cu(mal)(H2O)] fragments into [Cu(mal)(3-pina)(H2O)]n coordination polymer chains (Fig. 1b), aligned along the b crystal direction. The Cu


Cu distance spanned by the 3-pina ligands measures 11.611 Å. The sharp sawtooth

perspective of the chain is caused by the cis disposition of the pyridyl donor atoms at each Cu atom. The next nearest neighbor Cu


Cu through-space distance, defining the ‘‘wavelength” of the sawtooth pattern, is 11.377 Å. Chain motifs are aggregated into supramolecular layers oriented parallel to the ac crystal planes (Fig. 2) by hydrogen bonding donation from aqua ligands to unligated mal carboxylate oxygen atoms (Table S1). Isolated water molecules of crystallization are located in channels within each chain motif totaling 9.9% of the unit cell volume according to PLATON [28]. These are anchored to the coordination polymer chain motifs by accepting hydrogen bonds from N–H groups within the 3-pina amide moieties, and by donating hydrogen bonds to C@O

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Fig. 1. (a) Coordination environment of 1, with thermal ellipsoids at 50% probability and partial atom numbering scheme. (b) [Cu(mal)(3-pina)(H2O)]n 1D coordination polymer chain in 1.

Table 2 Selected bond distance (Å) and angle (°) data for 1. Cu1–O3 Cu1–O1 Cu1–N3#1 Cu1–N1 Cu1–O6 O3–Cu1–O1 O3–Cu1–N3#1 O1–Cu1–N3#1

1.933(4) 1.944(3) 2.016(5) 2.027(5) 2.269(4) 91.99(16) 87.80(17) 170.43(17)

O3–Cu1–N1 O1–Cu1–N1 N3#1–Cu1–N1 O3–Cu1–O6 O1–Cu1–O6 N3#1–Cu1–O6 N1–Cu1–O6

Table 3 Selected bond distance (Å) and angle (°) data for 2. 164.60(17) 87.13(16) 90.53(17) 99.03(15) 94.28(14) 95.21(17) 96.37(16)

Symmetry code for equivalent positions: #1 x + 2, y  1/2, z + 1/2.

Cu1–N3#1 Cu1–O3 Cu1–O5 Cu1–O1 Cu1–N1 O3–Cu1–O1 O3–Cu1–N3#1 O1–Cu1–N3#1

2.010(3) 1.940(2) 2.316(2) 1.941(2) 2.044(2) 93.95(9) 171.47(11) 88.69(10)

O3–Cu1–N1 O1–Cu1–N1 N3#1–Cu1–N1 O3–Cu1–O5 O1–Cu1–O5 N3#1–Cu1–O5 N1–Cu1–O5

83.80(10) 173.44(11) 92.68(10) 99.59(10) 91.16(9) 88.45(10) 95.29(10)

Symmetry code for equivalent positions: #1 x, y + 1, z + 1/2.

4.3. Structural description of {[Cu(mal)(4-pna)(H2O)]
3H2O}n (2)

Fig. 2. Supramolecular layer motif in 1. Hydrogen bonding between aqua ligands and unligated malonate carboxylate oxygen atoms are shown as dashed lines.

carbonyl units within other 3-pina ligands. Supramolecular layers stack in a direct AAA pattern along the a direction by means of hydrogen bonding donation from aqua ligands to ligated mal carboxylate oxygen atoms (Fig. S1).

The asymmetric unit of compound 2 contains a divalent copper atom, a mal ligand, a 4-pna ligand, an aqua ligand, and three water molecules of crystallization. As in 1, the copper coordination environment is a {CuN2O3} square pyramid (Fig. 3a), with a smaller deviation from ideality as marked by its s factor of 0.033. The specific donor atom pattern is the same as in 1, with cis disposed pyridyl nitrogen atoms from two 4-pna ligands in the basal plane along with a 1,3-chelating mal ligand, and an aqua ligand in the elongated axial position. Bond lengths and angles within the coordination sphere are listed in Table 3. Dipodal 4-pna ligands connect adjacent [Cu(mal)(H2O)] fragments into sawtooth [Cu(mal)(4-pna)(H2O)]n 1D coordination polymer chains (Fig. 3b) aligned along the b crystal direction, with a through-ligand Cu


Cu distance of 11.813 Å. This slight lengthening when compared to the related distance in 1 provokes a much longer sawtooth ‘‘wavelength” of 17.429 Å, as measured by nextnearest neighbor Cu


Cu through-space distances. Additionally, the longer ‘‘wavelength” of the chain motifs in 2 is instilled by the wider N–Cu–N angle within the coordination sphere (92.70 (10)° for 2 as opposed to 90.54(18)° for 1).

Fig. 3. (a) Coordination environment of 2, with thermal ellipsoids at 50% probability and partial atom numbering scheme. (b) [Cu(mal)(4-pna)(H2O)]n 1D coordination polymer chain in 2.

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Fig. 4. (a) Two-fold parallel interpenetration of supramolecular layers in 2. (b) Schematic representation of the interpenetrated (6,3) graphitic layers in 2.

Fig. 5. (a) Coordination environments of 3, with thermal ellipsoids at 50% probability and partial atom numbering scheme. (b) [Cu2(dmmal)2(4-pna)2(H2O)3]n (4,4) grid layer in 3.

Neighboring [Cu(mal)(4-pna)(H2O)]n coordination polymer chains are connected through pairwise long-range Cu–O ‘‘5 + 1” interactions (2.759 Å) between Cu atoms in one chain and mal carboxylate oxygen atoms (O2) in another. [Cu2(mal)2(H2O)2] dinuclear units, featuring eight-membered {CuOCOCuOCO} circuits with equatorial-axial anti-syn carboxylate bridges, are thereby formed (Fig. 3c). The Cu


Cu through-space separation within each [Cu2(mal)2(H2O)2] dinuclear unit is 5.039 Å. The 4-pna ligands then connect these into supramolecular layers parallel to the bc planes (Fig. S2) with through-space Cu


Cu distances of 18.372 and 17.429 Å. Apertures within each layer permit interpenetration of

another identical supramolecular layer (Fig. 4a), with stabilization provided by N–H


O hydrogen bonding between 4-pna ligands in one layer and mal O2 oxygen atoms in the other (Table S1). Treating the pairwise mal bridges as single linkers between two Cu atoms allows simplification of the layer system in 2 as a two-fold interpenetrated (6,3) graphitic net (Fig. 4b). Neighboring sets of interpenetrated layer motifs stack in an offset ABAB pattern along the a crystal direction (Fig. S3), aggregated via hydrogen bonding patterns involving aqua ligands and isolated interlamellar water molecules of crystallization. Water molecule pairs are also anchored into the interlayer regions by hydrogen

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Table 4 Selected bond distance (Å) and angle (°) data for 3. Cu1–O1 Cu1–O1#1 Cu1–O7 Cu1–N2#1 Cu1–N2 Cu2–O4#2 Cu2–O4 Cu2–N1#3 Cu2–N1#4 Cu2–O6#2 Cu2–O6 O1–Cu1–O1#1 O1#1–Cu1–O7 O1–Cu1–O7 O1–Cu1–N2#1 O1#1–Cu1–N2#1 O1#1–Cu1–N2 O1–Cu1–N2

1.9575(17) 1.9575(17) 2.210(3) 2.0040(19) 2.0039(19) 1.9584(16) 1.9584(16) 2.0518(19) 2.0518(19) 2.4973(18) 2.4973(18) 171.07(11) 94.47(6) 94.46(6) 88.68(8) 90.75(8) 88.68(8) 90.75(8)

N2#1–Cu1–O7 N2–Cu1–O7 N2–Cu1–N2#1 O4#2–Cu2–O4 O4#2–Cu2–N1#4 O4#2–Cu2–N1#3 O4–Cu2–N1#3 O4–Cu2–N1#4 O4#2–Cu2–O6#2 O4#2–Cu2–O6 O4–Cu2–O6#2 O4–Cu2–O6 N1#3–Cu2–N1#4 N1#4–Cu2–O6 N1#3–Cu2–O6#2 N1#4–Cu2–O6#2 N1#3–Cu2–O6 O6#2–Cu2–O6

93.70(5) 93.70(5) 172.60(11) 180.0 89.75(7) 90.25(7) 89.75(7) 90.25(7) 96.81(6) 83.18(6) 83.18(6) 96.81(6) 180.0 90.80(7) 90.80(7) 89.20(7) 89.20(7) 180.0

Symmetry codes for equivalent positions: #1 x + 2, y, z + 3/2; #2 x + 3/2, y + 3/2, z + 1; #3 x + 1/2, y + 3/2, z; #4 x + 1, y, z + 3/2.

bonding donation to 3-pina C@O amide moieties. The water molecules of crystallization in 2 occupy sheet like regions comprising 10.6% of the unit cell volume.

4.4. Structural description of {[Cu2(dmmal)2(4-pna)2(H2O)3]
7H2O}n (3) The asymmetric unit of compound 3 contains a divalent copper atom on a crystallographic two-fold rotation axis (Cu1), a divalent copper atom on a crystallographic inversion center (Cu2), a dmmal ligand, a 4-pna ligand, an aqua ligand on a two-fold rotation axis, another aqua ligand, and four water molecules of crystallization, one of which rests on the two-fold rotation axis. Operation of the crystallographic symmetry results in a nearly ideal {CuN2O3} square pyramidal coordination environment at Cu1 (s = 0.026), and a {CuN2O4} octahedral environment at Cu2 (Fig. 5a). At Cu1, pyridyl nitrogen donor atoms from two 4-pna ligands fill trans basal positions, as do carboxylate oxygen donor atoms from two dmmal ligands. The apical site at Cu1 is taken up by an aqua ligand. For Cu2, two pyridyl nitrogen donor atoms from 4-pna ligands are situated trans to each other, as are oxygen donor atoms from two

different dmmal ligands. The Jahn-Teller distorted trans elongated positions at Cu2 are filled by two aqua ligands. Bond length and angle information for the disparate coordination environments in 3 are given in Table 4. Bis(monodentate) dmmal ligands connect Cu1 and Cu2 atoms to afford zigzag [Cu2(dmmal)2(H2O)3]n chain motifs that are oriented parallel to [1 0 1], with a Cu


Cu distance of 6.698 Å. These are pillared by 4-pna ligands to construct [Cu2(dmmal)2(4-pna)2 (H2O)3]n (4,4) grid coordination polymer layers (Fig. 5b) that are arranged parallel to the ac crystal planes. The Cu


Cu throughligand distance across the 4-pna ligands is 11.127 Å. Two different grid apertures are evident in the layer motif. The concave apertures have Cu1


Cu1 through-space distances of 13.957 Å and Cu2


Cu2 distances of 11.927 Å. For the convex apertures, bracketed by pairs of 4-pna ligands engaging in mutual p–p interactions (centroid-to-centroid distance = 3.708 Å), the Cu2


Cu2 distances measure 13.957 Å while the Cu1


Cu1 distances are 11.927 Å. Neighboring {[Cu2(dmmal)2(4-pna)2(H2O)3]n layers stack in an offset ABAB pattern along the b crystal direction (Fig. S4), with hydrogen bonding between aqua ligands and 4-pna C@O moieties providing the supramolecular impetus (Table S1). Water molecules of crystallization situated in the interlamellar regions also serve to anchor the layer motifs to one another, via dmmal carboxylate oxygen atoms. Some of these water molecules form arc-like D(5) classification [29] discrete pentameric chains (Fig. S5), while others lie detached in an isolated fashion. The water molecules of crystallization in 3 occupy solvent accessible voids comprising 19.3% of the unit cell volume. 4.5. Structural description of {[Cu2(dmmal)2(3-pina)2]
9.5H2O}n (4) The asymmetric unit of compound 4 contains two divalent copper atoms (Cu1, Cu2), two fully deprotonated dmmal ligands (dmmal-A, dmmal-B), two 3-pina ligands (3-pina-A, 3-pina-B), and net nine and one-half water molecules of crystallization. Both Cu1 and Cu2 adopt a {CuN2O3} square pyramidal coordination environment (Fig. 6a), but with different levels of distortion from idealized geometry (s = 0.156 for Cu1, s = 0.014 for Cu2). For both Cu1 and Cu2, pyridyl nitrogen donor atoms from two 3-pina ligands are oriented in a cis fashion, one in the basal plane and the other in the elongated apical position. A dmmal-A ligand in a 1,3-chelating binding mode occupies two cis basal positions at

Fig. 6. (a) Coordination environments of 4, with thermal ellipsoids at 50% probability and partial atom numbering scheme. (b) [Cu4(dmmal)4] tetranuclear unit in 4. (c) [Cu4(dmmal)4(3-pina)2]n ribbon in 4.

B.S. Stone et al. / Inorganica Chimica Acta 446 (2016) 176–188 Table 5 Selected bond distance (Å) and angle (°) data for 4. Cu1–O1#1 Cu1–O2#1 Cu1–O4 Cu1–N5 Cu1–N4#2 Cu2–O5 Cu2–O6 Cu2–N2#3 Cu2–N6 Cu2–O12 O1#1–Cu1–O2#1 O1#1–Cu1–O4 O1#1–Cu1–N5 O1#1–Cu1–N4#2 O2#1–Cu1–O4

1.957(2) 1.960(3) 1.980(2) 2.235(3) 2.024(3) 1.958(3) 1.977(3) 2.017(3) 2.218(3) 1.955(3) 89.69(10) 174.60(11) 93.79(11) 90.97(12) 90.33(10)

O2#1–Cu1–N5 O2#1–Cu1–N4#2 O4–Cu1–N5 O4–Cu1–N4#2 N4#2–Cu1–N5 O5–Cu2–O6 O5–Cu2–N2#3 O5–Cu2–N6 O6–Cu2–N2#3 O6–Cu2–N6 N2#3–Cu2–N6 O12–Cu2–O5 O12–Cu2–O6 O12–Cu2–N2#3 O12–Cu2–N6

100.31(11) 165.21(12) 91.52(11) 87.64(11) 94.38(12) 90.01(10) 164.37(12) 99.21(11) 87.12(11) 91.37(11) 96.22(12) 89.70(10) 173.78(11) 91.50(12) 94.82(11)

Symmetry codes for equivalent positions: #1 x + 1, y, z + 1/2; #2 x + 1/2, y + 5/2, z; #3 x, y + 1, z + 1/2.

Cu1 with the remaining coordination site occupied by a single oxygen atom donor from a dmmal-B ligand. Similarly, a dmmal-B ligand occupies two cis basal positions at Cu2 via a 1,3-chelating binding mode, while the remaining basal position is filled by a dmmal-A carboxylate oxygen atom. Bond lengths and angles within the distinct coordination environments in 4 are listed in Table 5. The dmmal-A and dmmal-B ligands, which exhibit a l2-j3-O, 00 O :O000 binding mode, construct [Cu4(dmmal)4] tetranuclear units (Fig. 6b) wherein the copper atoms are connected by carboxylate groups in an anti-syn bridging mode across basal positions. The Cu


Cu distances through the dmmal-A and dmmal-B bridges

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are 4.872 and 4.887 Å, respectively. The tetrameric unit approaches an idealized rhombus in geometry, with Cu


Cu


Cu angles of 89.50° and 89.89°; the through-space Cu


Cu distances across the tetramer measure 6.870 and 6.892 Å. Tetranuclear [Cu4(dmmal)4] units are connected into [Cu4(dmmal)4(3-pina)2]n ribbons (Fig. 6c) by pairs of dipodal 3-pina-A ligands that span Cu1


Cu2 distances of 12.135 Å. Ribbon motifs are then connected by pairs of 3-pina-B ligands into a 3-D coordination polymer network with overall stoichiometry of [Cu4(dmmal)4(3-pina)4]n (Fig. 7a). The Cu1


Cu2 distances through the 3-pina-B ligands is 12.149 Å. Large void spaces within a single [Cu4(dmmal)4 (3-pina)4]n network allows interpenetration of two identical networks, resulting in a three-fold interpenetrated network in 4 (Fig. 7b). Supramolecular stabilization for the interpenetration is provided by hydrogen bonding donation from 3-pina amide N–H groups to the unligated dmmal carboxylate oxygen atoms (Table S1). The remaining incipient channels in the three-fold 3D network of 4 measure approximately 20 Å in diameter and comprise 26.3% of the unit cell volume. They are insufficient in size for inclusion of a fourth network, but instead contain the numerous water molecules of crystallization. These aggregate into infinite hydrogenbonded water tapes with a T6(5)A(1) classification (Fig. 7c) [29], in which six-membered water molecule rings share two water molecules with one adjacent ring and three water molecules with another. Associated single water molecules engage in hydrogen bonding to some of the water molecules shared between the sixmembered rings. There are also isolated water molecules that are anchored to the coordination polymer framework by donating hydrogen bonding to 3-pina carbonyl groups. Considering each

Fig. 7. (a) [Cu4(dmmal)4(3-pina)4]n 3-D coordination polymer network in 4. (b) Three-fold interpenetrated network in 4, highlighting solvent-accessible incipient channels. (c) Hydrogen-bonded water tape with a T6(5)A(1) classification in 4.

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Fig. 8. (a) Coordination environment of 5, with thermal ellipsoids at 50% probability and partial atom numbering scheme. (b) [Cu2(Hdmmal)2(dmmal)]n ribbon in 5. (c) View down c of the [Cu2(Hdmmal)2(dmmal)]n ribbon motif in 5.

tetranuclear unit as a tetrahedral 4-connected node results in simplification of the topology of 4 as a three-fold interpenetrated 66 diamondoid network (Fig. S6). 4.6. Structural description of {[Cu2(Hdmmal)2(dmmal)(4-pina)2]
0.5H2O}n (5) The asymmetric unit of compound 5 contains a divalent copper atom, half of a fully deprotonated dmmal ligand situated across a crystallographic rotation axis, a singly protonated Hdmmal ligand, a 4-pina ligand disordered over two sets of positions, and a partial occupancy water molecule of crystallization. A rather distorted square pyramidal coordination environment is observed at copper (s = 0.289), with trans 4-pina pyridyl nitrogen donor atoms in the basal plane (Fig. 8a). The other two trans basal positions are filled by oxygen atom donors from a dmmal ligand carboxylate group, and an Hdmmal ligand at its deprotonated carboxylate group. In the apical site rests an oxygen atom donor from the protonated carboxylate group of an Hdmmal ligand. Bond lengths and angles within the square pyramidal coordination environment are listed in Table 6. Copper atoms in 5 are linked by bis(monodentate) Hdmmal ligands into [Cu(Hdmmal)]n+ n cationic zigzag coordination polymer chains aligned along the c crystal axis, with a Cu


Cu distance of 8.003 Å. In turn these are connected into [Cu2(Hdmmal)2(dmmal)]n ribbons (Fig. 8b) by bis(monodentate) dmmal ligands. These dmmal ligands span a Cu


Cu distance of 7.122 Å, and result in each copper atom being a 3-connected node within the ribbon motif. Hydrogen bonding between the protonated carboxylate oxygen atoms of the Hdmmal ligands and unligated dmmal carboxylate oxygen atoms serves to stabilize the ribbon motifs

Table 6 Selected bond distance (Å) and angle (°) data for 5. Cu1–N4 Cu1–O4#1 Cu1–O5 Cu1–O6 Cu1–N2#2 N4–Cu1–O4#1 O5–Cu1–N4 O5–Cu1–O4#1

2.022(3) 2.326(3) 1.933(3) 1.965(3) 2.017(3) 87.41(12) 90.23(13) 118.40(12)

O5–Cu1–O6 O5–Cu1–N2#2 O6–Cu1–N4 O6–Cu1–O4#1 O6–Cu1–N2#2 N2#2–Cu1–N4 N2#2–Cu1–O4#1

159.30(13) 92.04(12) 89.21(12) 82.25(11) 89.54(12) 176.64(14) 89.32(12)

Symmetry codes for equivalent positions: #1 x, y, z  1/2; #2 x  1/2, y  1/2, z.

(Table S1). When the [Cu2(Hdmmal)2(dmmal)]n ribbon motif is viewed down the c axis (Fig. 8c), it can be seen that the 4-pina nitrogen donor atoms project both into the central region of the ribbon, and towards the periphery. Each [Cu2(Hdmmal)2(dmmal)]n ribbon motif connects to four others by means of the dipodal 4-pina ligands, resulting in a 3D [Cu2(Hdmmal)2(dmmal)(4-pina)2]n coordination polymer network (Fig. 9). The Cu


Cu distance through the dipodal dipyridylamide ligands is 13.317 Å. The 4-pina ligands project up through the interior of each [Cu2(Hdmmal)2(dmmal)]n ribbon motif and connect to the periphery of four other [Cu2(Hdmmal)2(dmmal)]n ribbon motifs. These linkages occur in a complicated crossed fashion, wherein 4-pina linkers originating on the interior left side of a ribbon connect to the periphery of two other ribbons located towards the right. Similarly, 4-pina linkers originating on the interior right side of a ribbon connect to the periphery of two other ribbons positioned towards the left (Fig. 10). Including the 4-pina linkers results in each copper atom in 5 serving as a 5-connected node. According to a calculation performed with TOPOS [30], the under-

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Fig. 9. [Cu2(Hdmmal)2(dmmal)(4-pina)2]n 3D coordination polymer network in 5. Individual [Cu2(Hdmmal)2(dmmal)]n ribbon motifs are drawn in red. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 10. Close-up perspective of 4-pina crossed linkages connecting [Cu2(Hdmmal)2(dmmal)]n ribbon motifs in 5. The central ribbon motif and four peripheral copper atoms are shown in red. Individual 4-pina connectors are shown in brown, green, orange, and blue. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

lying 3D network of 5 manifests a simple but heretofore unprecedented 5-connected self-penetrated 42678 topology (Fig. 11). Small solvent-accessible pockets within the highly entangled network of 5, comprising 14.9% of the unit cell volume, contain the water molecules of crystallization. 4.7. Structural description of {[Cu(emal)(4-pna)(H2O)]
3H2O}n (6) The asymmetric unit of compound 6 contains a divalent copper atom, an emal ligand whose central carbon atom and ethyl group are disordered over two sets of positions, an aqua ligand, and a 4-pna ligand, along with three water molecules of crystallization. The copper atom displays a {CuN2O3} distorted square pyramidal coordination geometry (s = 0.129), with the aqua ligand in the Jahn–Teller elongated apical position. Within the basal plane are two cis-disposed pyridyl nitrogen donor atoms from two 4-pna ligands, and two cis-disposed oxygen donor atoms from two emal

ligands (Fig. 12a). Bond lengths and angles within the coordination environment are listed in Table 7. In 6, the emal ligands serve as simple 1,3-chelating capping ligands. Adjacent [Cu(emal)(H2O)] fragments are connected into [Cu(emal)(4-pna)(H2O)]n coordination polymer chains by tethering 4-pna ligands (Fig. 12b); these span a Cu


Cu distance of 10.880 Å. The 1D chain motifs are aligned along the b crystal axis and aggregate into supramolecular slabs (Fig. S7) by hydrogen bonding patterns involving the interstitial water molecules of crystallization (Table S1). The amide N–H moiety in the 4-pna ligands in one chain engage in hydrogen bonding to water molecule trimers, which in turn are hydrogen bonded to unligated emal carboxylate oxygen atoms in a neighboring chain. Supramolecular slabs stack in an offset ABAB pattern along the c crystal direction, via other hydrogen bonding interactions between unligated emal carboxylate groups, water molecules of crystallization, and the aqua ligands (Fig. S8). The water molecules in 6 occupy solvent-accessible pockets totaling 12.0% of the unit cell volume. 4.8. Thermogravimetric analysis Thermogravimetric analyses were undertaken for 1–6 in order to investigate their dehydration and decomposition behavior. Upon removal from the mother liquor and filtration, compound 1 converted from blue single crystals into a pale blue powder, likely indicating crystal degradation due to loss of water molecules of crystallization. The resulting blue powder underwent a 5.1% mass loss between room temperature at 185 °C, corresponding to the loss of the aqua ligands (4.3% calc’d). Ligand decomposition occurred above this temperature. For 2, a mass loss of 13.9% between 25 °C and 200 °C indicates loss of bound and unbound water molecules (16.4% calc’d), followed by combustion above 200 °C. Compound 3 underwent dehydration between 70 and 180 °C in two stages, with a mass loss of 12.1% corresponding to the ejection of the water molecules of crystallization (13.1% calc’d). Ligand combustion and loss of the bound water molecules commenced above 180 °C. Dehydration of compound 4 occurred between 25 and 225 °C, with a mass loss of 10.0%. As the calculated mass loss for the water molecules of crystallization is 17.9%, it is

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Fig. 11. Schematic perspective of the unprecedented 5-connected self-penetrated 42678 topology in 5. The dmmal and 4-pina linkages are shown as red and blue rods, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 12. (a) Coordination environment of 6, with thermal ellipsoids at 50% probability and partial atom numbering scheme. Only one of the disordered ethyl group components is shown. (b) [Cu(emal)(4-pna)(H2O)]n 1D coordination polymer chain in 6.

Table 7 Selected bond distance (Å) and angle (°) data for 6. Cu1–O2 Cu1–O3 Cu1–O6 Cu1–N1 Cu1–N3#1 O2–Cu1–O6 O2–Cu1–N1 O2–Cu1–N3#1

1.952(2) 1.939(2) 2.280(3) 2.009(3) 2.005(3) 91.52(10) 88.89(11) 169.61(11)

O3–Cu1–O2 O3–Cu1–O6 O3–Cu1–N1 O3–Cu1–N3#1 N1–Cu1–O6 N3#1–Cu1–O6 N3#1–Cu1–N1

Symmetry code for equivalent positions: #1 x, y  1/2, z + 1.

93.53(10) 88.80(11) 177.35(11) 87.96(11) 90.06(11) 98.79(11) 89.85(11)

clear that some dehydration had occurred on long term storage (>90 d). Combustion of the residual organic components occurred above 225 °C. The mass of compound 5 remained stable until 100 °C. A 5.1% mass loss between 100 and 120 °C is indicative of loss of the water molecules of crystallization and likely decarboxylation of one of the dimethylmalonate ligands (5.7% calc’d). Compound 6 underwent loss of its water molecules of crystallization between 20 and 100 °C, with a mass loss of 12.1% matching well with the predicted value of 11.7%. Loss of the aqua ligands occurred between 100 and 185 °C, with full decomposition taking place above this temperature. No clear trends between coordination

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5. Conclusions

Fig. 13. Variable temperature magnetic susceptibility plot for 4. The best fit to Eq. (1) is shown as a thin black line.

polymer dimensionality and thermal robustness can be drawn. Thermograms for 1–6 are given in Figs. S9–S14, ESI, respectively. 4.9. Magnetic properties of 4 A variable temperature magnetic susceptibility study was undertaken on a freshly prepared polycrystalline sample of 4 due to the presence of carboxylate group bridged paramagnetic copper atoms. In the case of the other five compounds in this study, the copper atoms are linked by the full span of the dicarboxylate or dipyridylamide ligands, rendering any magnetic communication negligible; thus magnetic studies were not carried out on these materials. The vmT value for 4 at 300 K was 0.772 cm3-K mol1, roughly consistent with two S = 1/2 spins per formula unit. On cooling the vmT value increased slightly, to 0.83 cm3-K mol1 at 150 K and to 0.93 cm3-K mol1 at 50 K. Below this temperature the vmT product increased rapidly, attaining a value of 1.54 cm3K mol1 at 2 K. The overall profile of the curve is consistent with weak ferromagnetic coupling within the divalent copper tetranuclear units. A Curie–Weiss plot (Fig. S15) of the inverse susceptibility with respect to T across the entire temperature range of the experiment afforded C = 0.772 cm3-K mol1, and H = 5.3 K. The positive value of H is indicative of ferromagnetic coupling within the tetranuclear units in 4. For a more quantitative perspective, the susceptibility data was fit to the expression of Ruiz-Perez and Lloret (Eq. (1)) for a square tetramer of S = 1/2 spins [7]. The estimated best fit values were g = 2.03(5) and J = 11(3) cm1 with R = 0.0488 = {R[(vm T)obs  (vmT)calc]2/R[(vmT)obs]2} (Fig. 13). The positive value of J confirms the presence of ferromagnetic coupling within the tetranuclear units, mediated by the dmmal carboxylate groups spanning basal coordination sites on adjacent copper centers. A similar J value of 12.4(1) cm1 was observed in [Cu2(mal)2(H2O)2 (bpy)]n [7], consistent with the similar anti-syn carboxylate bridged square copper tetramers in 4. An increase in the v versus T plot at low temperature (Fig. S16) can also be ascribed to the presence of weak ferromagnetic coupling within the copper tetramers in 4.

vm T ¼



Ng 2 b2 k



W Z






W ¼ 2 þ exp  kTJ þ 5 exp kTJ

2J Z ¼ 7 þ exp  kT þ 3 exp  kTJ þ 5 exp

J kT




ð1Þ

A series of copper malonate coordination polymers with simple isomeric dipyridylamide ligands has been prepared and structurally characterized, revealing a marked dependence of the resulting topology on pyridyl nitrogen donor disposition and steric bulk along the aliphatic dicarboxylate component. Switching of 3-pyridyl and 4-pyridyl donors between 3-pina and 4-pna resulted in a change from a 1-D chain topology in 1 to a two-fold interpenetrated graphitic net in 2, both of which featured the unsubstituted malonate ligand. Interpenetration is avoided in 3, the dimethylmalonate analog of 2, along with an adjustment to a more standard rectangular grid layered motif. Increasing the steric bulk by using a more projecting ethyl substituent resulted in decrease in dimensionality to a 1-D chain in 6, consistent with previously observed structural trends in other coordination polymer systems [31,32]. The isonicotinamide ligands 3-pina and 4-pina both afforded 3-D copper dimethylmalonate coordination polymers (4 and 5), with the longer span of the latter ligand instilling a unique self-penetrated topology in 5. Adjustment of pyridyl nitrogen donor disposition also caused dramatic differences in co-crystallized water molecule aggregations. Acknowledgments We acknowledge Lyman Briggs College and Michigan State University for funding this work. We thank Dr. Shannon Biros of Grand Valley State University for assistance with the crystallography of compound 6. Appendix A. Supplementary material CCDC 1033860–1033865 contains the supplementary crystallographic data for 1–6. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www. ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at http:// dx.doi.org/10.1016/j.ica.2016.03.015. References [1] (a) M.P. Suh, H.J. Park, T.K. Prasad, D. Lim, Chem. Rev. 112 (2012) 782. and references therein; (b) L.J. Murray, M. Dinca, J.R. Long, Chem. Soc. Rev. 38 (2009) 1294. and references therein; (c) S.S. Han, J.L. Mendoza-Cortés, W.A. Goddard, Chem. Soc. Rev. 38 (2009) 1460. and references therein. [2] (a) K. Sumida, D.L. Rogow, J.A. Mason, T.M. McDonald, E.D. Bloch, Z.R. Herm, T. Bae, J.R. Long, Chem. Rev. 112 (2012) 724. and references therein; (b) J.R. Li, R.J. Kuppler, H.C. Zhou, Chem. Soc. Rev. 38 (2009) 1477. and references therein; (c) J. Li, J. Sculley, H. Zhou, Chem. Rev. 112 (2012) 869. and references therein. [3] (a) Q.-R. Fang, G.-S. Zhu, M. Xue, J.-Y. Sun, S.-L. Qiu, Dalton Trans. (2006) 2399; (b) X.-M. Zhang, M.-L. Tong, H.K. Lee, X.-M. Chen, J. Solid State Chem. 160 (2001) 118; (c) O.M. Yaghi, H. Li, T.L. Groy, Inorg. Chem. 36 (1997) 4292. [4] (a) J. Liu, L. Chen, H. Cui, J. Zhang, L. Zhang, C. Su, Chem. Soc. Rev. 43 (2014) 6011; (b) J.Y. Lee, O.K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp, Chem. Soc. Rev. 38 (2009) 1450. and references therein; (c) L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 38 (2009) 1248. and references therein; (d) T. Uemara, N. Yanai, S. Kitagawa, Chem. Soc. Rev. 38 (2009) 1228. and references therein. [5] (a) S. Zang, Y. Su, Y. Li, Z. Ni, Q. Meng, Inorg. Chem. 45 (2006) 174; (b) L. Wang, M. Yang, G. Li, Z. Shi, S. Feng, Inorg. Chem. 45 (2006) 2474; (c) S. Wang, Y. Hou, E. Wang, Y. Li, L. Xu, J. Peng, S. Liu, C. Hu, New J. Chem. 27 (2003) 1144. [6] M. Kurmoo, Chem. Soc. Rev. 38 (2009) 1353. and references therein. [7] Y. Rodriguez-Martín, Catalina Ruiz-Pérez, J. Sanchiz, F. Lloret, M. Julve, Inorg. Chim. Acta 318 (2001) 159. [8] M.R. Montney, R.L. LaDuca, Inorg. Chem. Commun. 10 (2007) 1518.

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