Structural Chemistry and Properties of Metal Oxalates Containing a

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Structural Chemistry and Properties of Metal Oxalates Containing a Long-Spanning Dipyridyl Ligand: Chain, Interpenetrated Diamondoid, Threaded-Loop Layer, and Self-Penetrated Topologies Margaret E. Robinson, Jessica E. Mizzi, Richard J. Staples, and Robert L. LaDuca Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00040 • Publication Date (Web): 16 Apr 2015 Downloaded from http://pubs.acs.org on April 20, 2015

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Crystal Growth & Design

Structural Chemistry and Properties of Metal Oxalates Containing a Long-Spanning Dipyridyl Ligand: Chain, Interpenetrated Diamondoid, Threaded-Loop Layer, and Self-Penetrated Topologies

Margaret E. Robinson, Jessica E. Mizzi, Richard J. Staples, and Robert L. LaDuca*

Lyman Briggs College and Department of Chemistry, Michigan State University, East Lansing, MI 48825 USA

* mailing address: Lyman Briggs College, E-30 Holmes Hall, 919 East Shaw Lane, Michigan State University, East Lansing, MI 48825 USA, email: [email protected]

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Abstract Hydrothermal reaction of metal oxalate (ox) salts and bis(4-pyridylmethyl)piperazine (bpmp) afforded a series of coordination polymers that were structurally characterized by single-crystal X-ray diffraction. {[Cd(H2O)4(bpmp)](ox)}n (1) and {[Co(H2O)4(bpmp)](ox)}n (2) shows isostructural cationic one-dimensional (1D) coordination polymer chain motifs with unligated ox anions. A higher temperature polymorph of 2, {[Co(ox)(bpmp)]•3H2O}n (3), possesses a system of three-fold interpenetrated three-dimensional (3D) diamondoid nets. {[Mn(H2O)4(bpmp)] [Mn2(ox)3]•5H2O}n (4) manifests a unique 1D + 2D 3D polyrotaxane coordination polymer structure with 1D cationic [Mn(H2O)4(bpmp)]n chains threaded through apertures coursing through parallel stacks of anionic [Mn2(ox)3]n two-dimensional (2D) hexagonal layers. {[Cu2(ox)2(bpmp)]•6H2O}n (5) possesses 2D [Cu2(ox)2]n layers pillared by bpmp ligands into a 3D [Cu2(ox)2(bpmp)]n coordination polymer network with an unprecedented 4,4-connected selfpenetrated (5383)2(5482) topology. Variable temperature magnetic susceptibility studies showed weak antiferromagnetic coupling along [Co(ox)]n chain submotifs in 3 with concomitant zerofield splitting (J = –4.1(7) cm–1, D = 34.5(6) cm–1), weak antiferromagnetic coupling within the [Mn2(ox)3]n hexagonal layers in 4 (J ~ –0.5 cm–1), and strong antiferromagnetic coupling within the 2D [Cu2(ox)2]n layers in 5 (J = –220(6) cm–1).


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Introduction Largely due to applications in hydrogen storage,1 molecular separations,2 carbon dioxide sequestration,3 heterogeneous catalysis,4 and explosives trace residue detection,5 metal-organic framework/coordination polymer synthetic investigations have continue unabated over the past decade. The enormous scope of possible anionic dicarboxylate ligands and neutral dipodal coligands, along with a variety of divalent metal coordination environments, provide access to myriad and diverse coordination polymer structural topologies.6 Carboxylate bridges between closely spaced paramagnetic ions can cause spin communication and temperature- and fielddependent magnetic properties in these phases.7 While most research in this genre of materials has focused on aromatic dicarboxylate and tricarboxylate ligands,8 there have been several studies examining the structure and magnetic properties of divalent metal coordination polymers containing oxalate (ox, Scheme 1), the shortest possible dicarboxylate ligand.9–22 These reports have revealed that ox ligand can adopt a variety of possible binding modes, resulting in different topologies containing metal oxalate chain and layer submotifs with divergent magnetic properties. In the absence of a dipyridyl coligand, metal oxalate solids often display structure types consisting of anionic [M2(ox)3] layers or networks with cationic components resting within the layer or net apertures, or in interlamellar regions.9 For example, (NBu4)2[Cr2(ox)3] exhibits graphitic honeycomb type metal oxalate layers,10 while {[Ru(2,2′-bipyridine)3][Mn2(ox)3]} shows optically active complex cations embedded within apertures in a chiral (10,3) 3D metal oxalate network.11 Incorporation of a dipyridyl coligand can result in materials in which both the oxalate ligand and dipodal tether can be responsible for extending the coordination polymer dimensionality. For example, both [Co(ox)(bpy)]n and [Co(ox)(dpe)]n (bpy = 4,4′-bipyridine; dpe



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= 1,2-di(4-pyridyl)ethane) display [Co(ox)]n straight chains pillared by the dipyridyl tethers into (4,4) rectangular grid topologies.12,13 Variable temperature magnetic studies of the former compound revealed weak antiferromagnetic coupling along the [Co(ox)]n straight chains motif, with a Neel temperature of 13 K.12 Use of the tetrapyridyl ligand 1a,4a-dihydroxy-1e,2e,4e,5etetra(4-pyridyl)cyclohexane (dchtpy) afforded the multifunctional material [Co2(ox)2(dchtpy)] ·9H2O}n.14 The tetranodal dchtpy ligand fostered a rare 3D mog net, which manifested both gated absorption and release of CO2 and antiferromagnetic coupling along twisted [Co(ox)]n chain motifs. Few cadmium oxalate dipyridyl coordination polymers have been reported, but hexagonal grid (6,3) hcb layers tend to be prevalent within this limited class of materials.15–16 Both [Cd(ox)(dpp)]n (dpp = 1,3-di(4-pyridyl)propane)15 and [Cd(ox)(pptp)]n (pptp = 2-(3-(4(pyridin-4-yl)phenyl)-1H-1,2,4-triazol-5-yl)pyridine)16 have this hcb topology. In the latter case, two supramolecular isomers with flat and wavy hexagonal layer motifs could be obtained.16 [Cu(ox)(bpy)]n also displayed a (4,4) grid structure like its cobalt analog, with weak ferromagnetic coupling fostered by axial-equatorial bridged ox carboxylate groups within [Cu(ox)]n chain motifs.17 A longer spanning dipyridyl ligand, 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) afforded a 3D [Cu(ox)(bpo)]n phase with a rare 4,4-connected (53627)2(5482) NiP2 zeolite topology. This [Cu(ox)(bpo)]n phase possessed equatorial-equatorial bridging of oxalate carboxylate groups, resulting in extremely significant antiferromagnetic coupling.18 Reaction of manganese salt precursors with an oxalate source and 1,2-bis(4-pyridyl)ethylene (bpee) resulted in numerous different 2D and 3D coordination polymer phases depending on synthetic conditions.19 The structure of {(Hbpee)2[Mn2(ox)3]3·0.8(C2H5OH)3·0.4(H2O)}n displayed Hbpee cations intercalated between anionic hexagonal [Mn2(ox)3]3 layers, while {[Mn(ox)(bpee)]·xH2O}n possessed a three-fold interpenetrated diamondoid network structure.19


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The former phase was prepared via a solvent diffusion method in the presence of oxalic acid, while the latter required potassium oxalate for successful synthesis and isolation. In light of the interesting structural diversity in previously reported metal oxalate coordination polymers, we set about attempts to prepare crystalline divalent metal oxalate coordination polymers containing the easily prepared dipyridine ligand bis(4pyridylmethyl)piperazine (bpmp, Scheme 1). This long-spanning tethering ligand has been successfully employed by our group23–25 and other groups26–27 to construct divalent metal dicarboxylate coordination polymers with very rare or unique topologies. Among the more intriguing examples are the threaded-loop self-catenated polyrotaxane 2D layered phase {[Zn3(tricarballylate)2(bpmp)(Hbpmp)2](ClO4)2 •5H2O}n,23 and the complicated 3D 8-connected 4451767 self-penetrated topology in [Co3(oxybisbenzoate)3(bpmp)2]n.24 We herein report the single-crystal structural characterization and thermal decomposition studies of five new metal oxalates containing the bpmp ligand: {[Cd(H2O)4(bpmp)](ox)}n (1),{[Co(H2O)4(bpmp)](ox)}n (2), {[Co(ox)(bpmp)]•3H2O}n (3), {[Mn(H2O)4(bpmp)] [Mn2(ox)3]•5H2O}n (4), and {[Cu2(ox)2(bpmp)]•6H2O}n (5). Variable temperature magnetic susceptibility analysis was carried out for 3–5 due to the presence of closely spaced spin carriers.

Experimental Section General Considerations Bis(4-pyridylmethyl)piperazine28 (bpmp) and K2[M(ox)2] salts (M = Cd, Co, Mn, Cu)29 were prepared via published procedures. Water was deionized above 3 MΩ-cm in-house. IR spectra were recorded on powdered samples using a Perkin Elmer Spectrum One instrument. Variable temperature magnetic susceptibility data for 3–5 (2 K to 350 K) were collected on a Quantum



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Design MPMS SQUID magnetometer at an applied field of 0.1 T or 1.0 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,30 and for the diamagnetism of the sample holder. Thermogravimetric analysis was performed on a TA Instruments Q50 thermal analyzer under flowing N2. Elemental Analysis was carried out using a Perkin Elmer 2400 Series II CHNS/O Analyzer.

Preparation of {[Cd(H2O)4(bpmp)](ox)}n (1) K2[Cd(ox)2]•2H2O (103 mg, 0.37 mmol) and bpmp (48 mg, 0.18 mmol) were placed into 5 mL distilled H2O in a 23 mL Teflon-lined acid digestion bomb. The bomb was sealed and heated at 120°C in an oven for 24 h. The bomb was then allowed to air cool to 25°C. Colorless blocks of 1 (81 mg, 83 % yield based on bpmp) were isolated after washing with distilled water and acetone, and drying in air. Anal. Calc. for C18H28CdN4O8 1: C, 39.97; H, 5.21; N, 10.36 %; Found: C, 39.71; H, 4.96; N, 10.17 %. IR (cm–1): 3208 (s, br), 2957 (w), 2887 (w), 2828 (m), 2812 (m), 2786 (w), 2695 (w), 2251 (w, br), 1957 (w), 1563 (s), 1459 (m), 1429 (m), 1399 (w), 1373 (w), 1354 (w), 1339 (w), 1295 (s), 1267 (w), 1232 (m), 1152 (m), 1131 (m), 1070 (w), 1011 (m), 996 (m), 943 (w), 836 (m), 749 (m).

Preparation of {[Co(H2O)4(bpmp)](ox)}n (2) K2[Co(ox)]2•2H2O (52 mg, 0.18 mmol) and bpmp (48 mg, 0.18 mmol) were placed into 5 mL distilled H2O in a 23 mL Teflon-lined acid digestion bomb. The bomb was sealed and


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heated at 100°C for 24 h. The bomb was then allowed to air cool to 25°C. Pink blocks of 2 (10 mg, 11 % yield based on Co) were isolated after washing with distilled water and acetone, and drying in air. Anal. Calc. for C18H28CoN4O8 2: C, 44.35; H, 5.79; N, 11.50 %; Found: C, 44.10; H, 5.43; N, 11.19 %. IR (cm–1): 3241 (br, m), 3078 (br, m), 2952 (w), 2887 (w), 2830 (m), 2812 (m), 2789 (w), 1621 (w), 1566 (s), 1459 (m), 1429 (m), 1397 (w), 1355 (w), 1341 (m), 1305 (s), 1267 (w), 1234 (m), 1152 (m), 1126 (m), 1069 (w), 1023 (m), 1010 (m), 995 (m), 851 (w), 839 (m), 789 (w), 756 (s), 665(w).

Preparation of {[Co(ox)(bpmp)]•3H2O}n (3) K2[Co(ox)2]•2H2O (87 mg, 0.37 mmol) and bpmp (48 mg, 0.18 mmol) were placed into 5 mL distilled H2O in a 23 mL Teflon-lined acid digestion bomb. The bomb was sealed and heated at 120°C for 24 h. The bomb was then allowed to air cool to 25°C. Pink blocks of 3 (57 mg, 67 % yield based on bpmp) were isolated after washing with distilled water and acetone, and drying in air. Anal. Calc. for C36H52Co2N8O14 3: C, 46.06; H, 5.58; N, 11.94 %; Found: C, 45.67; H, 5.39; N, 11.55 %. IR (cm–1): 3366 (m, br), 2917 (w), 2817 (m, br), 1672 (m), 1611 (s), 1560 (w), 1504 (w), 1457 (w), 1426 (m), 1359 (m), 1313 (s), 1221 (w), 1205 (w), 1146 (w), 1130 (w), 1074 (w), 1023 (w), 1007 (w), 901 (w), 857 (w), 817 (m), 795 (m), 780 (m), 752 (w), 682 (m), 668 (w)

Preparation of {[Mn(H2O)4(bpmp)][Mn2(ox)3]•5H2O}n (4) K2[Mn(ox)2]•2H2O (123 mg, 0.57 mmol) and bpmp (43 mg, 0.18 mmol) were placed into 5 mL distilled H2O in a 23 mL Teflon-lined acid digestion bomb. The bomb was then allowed to air



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cool to 25°C. The bomb was sealed and heated at 120°C for 24 h. The resulting off-white crystals were filtered, washed with water and acetone and air dried to give 41 mg of 4 (79 % yield based on Mn). Anal. Calc. for C22H38Mn3N4O21 4: C, 30.75; H, 4.46; N, 6.52% Found: C, 30.44; H, 4.10; N, 6.18%. IR (cm-1): 3075 (s, br), 1603 (s), 1456 (w), 1427 (m), 1365 (w), 1302 (s), 1213 (w), 1141 (w), 1119 (w), 1071 (w), 1011 (w), 995 (w), 893 (w), 836 (w), 792 (m), 729 (m).

Preparation of {[Cu2(ox)2(bpmp)]•6H2O}n (5) K2[Cu(ox)2]•2H2O (123 mg, 0.57 mmol) and bpmp (43 mg, 0.18 mmol) were placed into 5 mL distilled H2O in a 23 mL Teflon-lined acid digestion bomb. The bomb was sealed and heated at 120°C for 24 h, and was then allowed to air cool to 25°C. The resulting green crystals were filtered, washed with water and acetone and air dried to give 32 mg of 5 (52 % yield based on bpmp). Anal. Calc. for C20H32Cu2N4O14 5: C, 35.35; H, 4.75; N, 8.24% Found: C, 35.21; H, 4.44; N, 7.95%. IR (cm-1): 3615 (w), 3420 (m, br), 2959 (w), 2844 (w), 1702 (m), 1595 (s), 1562 (m), 1455 (w), 1425 (m), 1351 (m), 1303 (s), 1226 (m), 1147 (m), 1122 (m), 1065 (m), 1036 (w), 1008 (m), 936 (m), 842 (m), 797 (s).

X-ray Crystallography Single crystal X-ray diffraction was performed on crystals of 1–5 using a Bruker-AXS ApexII CCD instrument at 173 K. Diffraction data were acquired using graphite–monochromated MoKα radiation (λ = 0.71073 Å). The data was integrated via SAINT.31 Lorentz and polarization


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effect and empirical absorption corrections were applied with SADABS (1, 2, 4, 5) or TWINABS (3).32 The structures were solved using direct methods and refined on F2 using SHELXTL.33 The twin law for the non-merohedrally twinned crystal of 3 was determined using CELL NOW;34 reflections from both twin components were used in the refinement. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms bound to carbon atoms were placed in calculated positions and refined isotropically with a riding model. The hydrogen atoms of the ligated and unligated water molecules were found via Fourier difference maps, and then restrained at fixed positions and refined isotropically. One of the carbon atoms within the piperazinyl ring of the bpmp ligands in 1 was disordered equally over two sets of symmetry equivalent positions. Relevant crystallographic data for 1–5 is listed in Table 1. Topological analyses were carried out using TOPOS software,35 while PLATON was used for calculating solvent-accessible void space volumes.36 Results and Discussion Synthesis and Spectral Characterization Compounds 1–5 were prepared via hydrothermal reaction of the requisite potassium metal oxalate salt with bpmp. Compounds 4–5 could also be prepared, albeit in lower yield, as crystalline products by slow diffusion of aqueous solutions of the requisite potassium metal oxalate salt with a methanolic solution of bpmp. The infrared spectra of 1–5 were consistent with their structural characteristics as determined by single–crystal X–ray diffraction. Weak and medium intensity bands in the range of ~1600 cm–1 to ~1200 cm–1 can be ascribed to stretching modes of the pyridyl rings of nitrogen–base ligands. Puckering modes of the pyridyl rings are evident in the region between 820 cm–1 and 600 cm–1. Asymmetric and symmetric C–O stretching modes of the carboxylate groups of fully deprotonated oxalate ligands correspond to



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the strong, broadened features at 1563 cm–1 and 1429 cm–1 (for 1), 1566 cm–1 and 1305 cm–1 (for 2), 1577 cm–1 and 1313 cm–1 (for 3), 1605 cm–1 and 1303 cm–1 (for 4), and 1595 cm–1 and 1425 cm–1 (for 5). Broad yet weak bands in the region of ~3400 cm–1 to ~3200 cm–1 represent O–H bonds within ligated or unbound water molecules in 1–5. The broadness of these higher energy spectral features is caused by the hydrogen bonding present in all cases.

Structural Description of {[Cd(H2O)4(bpmp)](ox)}n (1) and {[Co(H2O)4(bpmp)](ox)}n (2) As both 1 and 2 are isostructural, only compound 1 will be discussed in detail. The asymmetric unit of compound 1 contains a divalent cadmium atom on the Wyckoff special position a in C2/m space group, which lies at the intersection of a crystallographic mirror plane and a perpendicular two-fold rotation axis. An aqua ligand, a quarter of a bpmp ligand with its nitrogen atoms and some of its carbon atoms resting on the crystallographic mirror plane, and one carbon and one oxygen atom belonging to an ox dianion comprise the rest of the asymmetric unit. Operation of the crystallographic symmetry at cadmium reveals a symmetrical {CdO4N2} octahedral coordination environment, a complete splayed-open conformation bpmp ligand with N•••N•••N•••N torsion angle of 180°, and a complete but non-ligating ox dianion (Fig. 1a). Bond lengths and angles within the coordination spheres for 1 and 2 are listed in Table 2. The bond lengths in 2 are shorter, consistent with standard ionic radius trends.37 The dipodal bpmp ligands link [Cd(H2O)4]2+ coordination fragments into 1-D cationic [Cd(H2O)4(bpmp)]n coordination polymer chains, with a Cd•••Cd distance of 16.657 Å. Arranged along the [1 0 –1] crystal direction, the chain motifs are aggregated into supramolecular layers parallel to ac by hydrogen bonding donation (Table S1) from the aqua


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ligands to the unligated ox dianions (Fig. 1b). In turn, the supramolecular layers aggregate into the 3-D crystal structure of 1 by another O–H•••O hydrogen bonding pathway between the aqua ligands and free ox dianions (Fig. S1). The chain structure of 1 contrasts with the hexagonal layer structures observed in the few previous examples of cadmium oxalate phases containing dipyridyl tethers.15–16 In contrast to previously reported crystalline cobalt oxalates with embedded dipyridyl ligands,12–14 the ox dianions in 2 do not bind to cobalt, instead forming a bpmp-linked chain isostructural with its cadmium congener 1.

Structural Description of {[Co(ox)(bpmp)]•3H2O}n (3) The asymmetric unit of compound 3 contains two divalent Co atoms (Co1, Co2), two ox ligands, one complete bpmp ligand, halves of two other bpmp ligands whose central piperazinyl rings are located over crystallographic inversion centers, and six water molecules of crystallization. A distorted octahedral {CoO4N2} coordination environment exists at each cobalt atom, with cis pyridyl nitrogen donor atoms belonging to bpmp ligands, and 1,2-chelating carboxylate groups from two oxalate anions. Bond lengths and angles within the coordination spheres are listed in Table 3, with a thermal ellipsoid plot shown in Fig. 2a. Crystallographic distinction between the Co1 and Co2 atoms is enforced by slightly different bond parameters. The Co1 and Co2 atoms are conjoined by bis(chelating) ox anions, resulting in undulating [Co(ox)]n chain motifs (Fig. 2b) formed by pairs of anti-syn carboxylate bridges. Due to the crystallographic distinction between the oxalate ligands, the Co•••Co distances along the chain alternate between 5.443 Å and 5.430 Å. All of the [Co(ox)]n chains are arranged parallel to the a crystal axis. Cobalt atoms in 3 are also connected by the dipodal bpmp tethers, constructing [Co(bpmp)]n chain motifs (Fig. 2c) oriented parallel to the [2 4 1] crystal direction.



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The three crystallographically distinct bpmp ligands span internuclear Co•••Co distances of 16.230, 16.425, and 16.820 Å. The two different chain motifs in 3 construct a 4-connected [Co(ox)(bpmp)]n diamondoid net (Fig. 3a), with significant apertures (~24 Å x ~24 Å) oriented along the a direction. These are filled by two identical [Co(ox)(bpmp)]n diamondoid nets, resulting in net three-fold interpenetration (Fig. 3b). Residual incipient solvent-accessible void space comprising 16.6 % are occupied by isolated water molecules and water molecule trimers. These are anchored to the interpenetrated coordination polymer framework by donating hydrogen bonds to oxalate oxygen atoms or bpmp piperazinyl nitrogen atoms (Table S1). The three-fold interpenetrated diamondoid network of 3 is similar to that observed in the previously reported complex {[Mn(ox)(bpee)]·xH2O}n.19 Nevertheless, significant structural contrast is observed with previously reported layered or non-interpenetrated 3-D cobalt oxalate dipyridyl phases,12–14 although these and 3 do contain [Co(ox)]n chain motifs. Structural Description of {[Mn(H2O)4(bpmp)][Mn2(ox)3]•5H2O}n (4) The asymmetric unit of compound 4 contains two divalent Mn atoms (Mn1, Mn2), one of which (Mn1) rests on a crystallographic two-fold rotation axis, along with two aqua ligands, halves of three crystallographically distinct ox ligands, one-half of a bpmp molecule, and three water molecules of crystallization, one of which (O3W) sits on a crystallographic two-fold rotation axis. The centroids of all of the oxalate and bpmp ligands rest on crystallographic inversion centers. Operation of the crystallographic symmetry reveals {MnO4N2} and {MnO6} distorted octahedral coordination environments at Mn1 and Mn2, respectively. The Mn1 atoms are coordinated by four aqua ligands in their equatorial planes, and trans axial bpmp pyridyl nitrogen donor atoms, while the Mn2 atoms are bound by three ox ligands in a 1,2-chelating binding mode. Bond lengths and angles within the octahedral coordination environments in 4


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are given in Table 4, while a thermal ellipsoid model of the coordination environments is shown in Fig. 4a. All of the ox ligands in 4 bridge two Mn2 atoms with a bis(1,2-chelating) µ2κ4O,O′′:O′,O′′′ binding mode (Scheme 1), affording anionic [Mn2(ox)3]n2n– honeycomb layers arranged parallel to the ab crystal planes (Fig. 4b). The Mn•••Mn through-ligand contact distances within the layer motifs measure 5.67 Å, while the through-space Mn•••Mn distances across the hexagonal apertures within the [Mn2(ox)3]n2n– honeycomb layers range between 11.20 Å and 11.45 Å. Parallel [Mn2(ox)3]n2n– layers stack in an ABAB pattern along the c crystal direction. The bpmp ligands possess a symmetry enforced anti conformation (N•••N•••N•••N torsion angle = 180°) and conjoin [Mn1(H2O)4]2+ complexes into cationic 1-D [Mn(H2O)4(bpmp)]n2n+ coordination polymer chains similar to the cadmium chain motifs in 4 (Fig. 4c), with a Mn•••Mn through-ligand contact distance of 16.106 Å. These chains are oriented parallel to the [–1 0 1] crystal direction, and thereby penetrate through the apertures in parallel [Mn2(ox)3]n2n– honeycomb layers (Fig. 5a). Thus 4 represents a rare example of threaded-loop 1D + 2D 3D polyrotaxane coordination polymer.38–39 Notably, the [Mn(H2O)4(bpmp)]n2n+ chains do not penetrate directly stacked apertures in neighboring [Mn2(ox)3]n2n– honeycomb layers. Instead they penetrate through apertures offset by +a or –a in adjacent layer motifs, making a 29° angle with respect to the layer planes. The piperazinyl rings of the bpmp ligands in the chain motifs are locked directly within the apertures of the honeycomb layers, anchored via unligated isolated water molecules that engage in mutual hydrogen bonding donation between the bpmp piperazinyl nitrogen atoms and ox carboxylate oxygen atoms (Fig. 5b). Water molecule trimers aggregate near the [Mn1(H2O)4]2+



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complexes within the [Mn(H2O)4(bpmp)]n2n+ chains, engaging in hydrogen bonding with the aqua ligands and ox carboxylate groups within the layer motifs. The water molecules of crystallization in 4 occupy 9.9 % of the unit cell volume. Hydrogen bonding information is listed in Table S1. To the best of our knowledge, there are two previously reported 1D + 2D 3D polyrotaxane coordination polymers. {[Zn(2-sulfoterephthalate)(bpy)(H2O)(H2O)0.25]2 [Zn(bpy)(H2O)4]•4H2O}n has cationic [M(H2O)4L]n type chains similar to those in 4, but these penetrate through stacked anionic (4,4) square grid motifs.38 A more direct structural analog to 4 is the polyrotaxane phase [Ag(bpp)][Ag2(bpp)2(ox)]NO3 (bpp = 1,3-bis(4-pyridyl)propane), which has cationic chains passing through stacked neutral honeycomb layer components.39 Nevertheless, compound 4 is unique in that it has features of both prior 1D + 2D 3D polyrotaxanes, with cationic chains passing through apertures in anionic hexagonal grids without the need for charge balancing counteranions (Fig. 5c). Compound 4 has similar [Mn2(ox)3]n2n– anionic honeycomb layers hexagonal grid layers as {(Hbpee)2[Mn2(ox)3]3·0.8(C2H5OH)3·0.4(H2O)}n,19 with the threaded [Mn(H2O)4(bpmp)]n2n+ chains serving as countercations instead of protonated, intercalated Hbpee moieties. It may also be seen that the [Mn(H2O)4(bpmp)]n2n+ chain motifs in 4 are similar to the [Cd(H2O)4(bpmp)]n2n+ and [Co(H2O)4(bpmp)]n2n+ chain motifs in 1 and 2, with the [Mn2(ox)3]n2n– layers serving as the counteranionic component instead of unligated ox dianions.

Structural Description of {[Cu2(ox)2(bpmp)]•6H2O}n (5) The asymmetric unit of compound 5 consists of a divalent Cu atom, halves of two crystallographically distinct oxalate ligands (ox-A, ox-B), one-half of a bpmp ligand, and three


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water molecules of crystallization. Centroids of the oxalate and bpmp ligands rest on crystallographic inversion centers. The coordination environment at copper is a Jahn-Teller distorted {CuO5N} octahedron (Fig. 6a), with an ox-A ligand in a 1,2-chelating binding mode occupying cis sites in the equatorial plane. A pyridyl nitrogen donor from a bpmp ligand also takes up an equatorial position. An ox-B ligand with a 1,2-chelating binding mode spans the last equatorial position and an axial position, while a single oxygen donor atom from a second ox-B ligand fills the remaining axial position. Bond lengths and angles within the coordination sphere are listed in Table 5. The Cu atoms in 5 are connected into [Cu2(ox)2]n coordination polymer layers (Fig. 6b) situated parallel to the bc crystal planes through a variety of oxalate binding and bridging modes (Scheme 1). The bidentate ox-A ligands connect Cu atoms as simple linkers with a µ2κ4O,O′′:O′,O′′′ binding mode, where each supplies a pair of anti-anti carboxylate bridges between adjacent Cu atoms. These connect equatorial sites on adjacent Cu atoms, and furnish a Cu•••Cu distance of 5.200 Å. In contrast the ox-B ligands conjoin four Cu atoms in an exotetradentate µ4-κ4O:O,O′′:O′,O′′′:O′′′ binding mode (Scheme 1). Bridging µ2-O single oxygen atoms belonging to ox-B span axial coordination sites on neighboring Cu atoms to form [CuO]n chain motifs within the [Cu2(ox)2]n layers, oriented parallel to the c crystal axis with a Cu•••Cu distance of 4.127 Å. The full span of the ox-B ligands joins Cu atoms in an equatorial/axial fashion via pairs of anti-anti carboxylate bridges with a Cu•••Cu distance of 5.952 Å. The ox-B ligands also provide anti-syn carboxylate bridges in an equatorial/axial fashion, giving a Cu•••Cu distance of 5.539 Å. Neighboring [Cu2(ox)2]n coordination polymer layers stack along the a crystal direction, and are pillared by bpmp ligands to afford a 3-D [Cu2(ox)2(bpmp)]n coordination polymer



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network (Fig. 7). The closest distance between Cu atoms in neighboring [Cu2(ox)2]n layers is 16.379 Å. This gap is too short to be spanned straight across by the bpmp ligands, which instead connect Cu atoms in adjacent [Cu2(ox)2]n layers in an offset fashion with a Cu•••Cu distance of 16.502 Å. Co-crystallized infinite water molecule chains (Fig. S2) occupy incipient 1-D channels bracketed by bpmp ligands, which comprise 26.4 % of the unit cell volume. These water molecule chains have a C(4)A(2) classification according to the notation developed by Infantes;40 every other water molecule in the chain has an associated isolated water molecule hydrogen bonded to it. The water molecule aggregations are stabilized by hydrogen bonding within the chains (Table S1) and to bpmp piperazinyl nitrogen atoms and ox carboxylate oxygen atoms within the coordination polymer framework. A topological analysis of the 3-D net of 5 was undertaken by treating the ox-A and bpmp ligands as simple linkers and the Cu atoms and exotetradentate ox-B ligands as 4-connected nodes. The Cu nodes connect to other Cu nodes through ox-A and bpmp linkers, and are bound to two ox-B nodes, in an extended pseudo-tetrahedral arrangement. The ox-B nodes act as square planar nodes within a single [Cu2(ox)2]n sublayer. From this perspective, the resulting 4,4connected binodal net has a relatively simple yet unprecedented self-penetrated (5383)2(5482) topology (Fig. 8a), where the first term represents the copper atom nodes and the second represents the exotetradentate ox-B ligands. The extended point symbol is [5.82.5.82.5.84]2[5.5.5.5.84.86]. A close-up view of the self-penetration of a pair of 8-membered circuits is shown in Fig. 8b. The network in 5 has a similar connectedness as the (53627)2(5482) NiP2 zeolite topology in [Cu(ox)(bpo)]n, but the longer bpmp tethers enforce self-penetration and an altered topology at the copper atom nodes in the present case.18 The structure of 5 greatly


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contrasts with the (4,4) grid topology promoted by the shorter rigid-rod tether bpy in [Cu(ox)(bpy)]n.17

Magnetic properties of 3–5 Variable temperature magnetic susceptibility studies were carried out to investigate spin interactions in 3–5. Due to the very long separation between cobalt ions in 2, magnetic studies were not carried out for this material. For the cobalt derivative 3, the data fit the Curie-Weiss law (Fig. S3) from 20 K to 350 K, with Θ = –63.3 K and C = 3.06 cm3-K mol–1. The negative Weiss constant is indicative of antiferromagnetic coupling, with likely presence of single ion effects such as zero-field splitting common for divalent cobalt ions in distorted octahedral environments. The higher than expected value of C is ascribed to the presence of spin-orbit coupling. The χmT value was 2.52 cm3-K mol Co–1 at 300 K, higher than expected for the S = 3/2 spin-only with g = 2 due to spin-orbit coupling. This value decreases to 2.38 cm3-K mol–1 at 200 K, 1.37 cm3-K mol–1 at 60 K, and 0.02 cm3-K mol–1 at 2 K. The overall shape of the curve is consistent with antiferromagnetic coupling between cobalt atoms via the pairs of anti-syn carboxylate bridges provided by each oxalate ligand along the [Co(ox)]n chain motifs. The bpmp ligands are far too long-spanning to promote any appreciable magnetic superexchange. The χmT data for 3 were fit to the phenomenological expression proposed by Rueff (eq. 1).41 The best-fit values (Fig. 9) to this expression were: J = –4.1(7) cm–1, D = 34.5(6) cm–1, A = 2.71(2) and B = 0.24(3) (giving g = 2.51) with R = {Σ[(χm T)obs – (χmT)calc]2}1/2 = 3.9 × 10–4. The higher than expected g value is indicative of spin-orbit coupling. The fit reveals the presence of concomitant weak antiferromagnetic coupling (small, negative J value) and single-ion effects such as zero-field splitting and formation of Kramers doublets (positive D parameter).



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χ mT = A exp(–D / kT ) + B exp(J / kT ) (eq. 1) where A + B = C = (5Ng 2 β 2 / 4k) The inverse susceptibility data for 4 fit the Curie-Weiss Law (Fig. S4) with Θ = –11.8 K and C = 13.85 cm3-K mol–1, roughly consistent with three uncoupled S = 5/2 spins per formula unit. The negative Weiss constant portends a modicum of antiferromagnetic coupling within 4. The χmT value was 13.10 cm3-K mol–1 at 300 K, then slowly decreased to 12.37 cm3-K mol–1 at 100 K, 9.38 cm3-K mol–1 at 30 K, and 4.74 cm3-K mol–1 at 2 K. The shape of the χmT vs T curve (Fig. 10) indicates weak antiferromagnetic coupling within the graphitic [Mn2(ox)3]n sublattice, with residual paramagnetic isolated S = 5/2 spins from the divalent manganese ions in the chain motifs spanned by the very long bpmp ligands. Unsuccessful attempts were made to model the susceptibility data using published expressions for a hexagonal S = 5/2 layer42–43 with the additional of a term for additional isolated S = 5/2 spins, likely due to interference of single-ion effects among the isolated manganese ions in the chain motifs. The exchange parameter J can be roughly estimated from the theta value via the expression J = 3kΘ/2Z(S(S+1)).44 With Z = 3 because each ion in the graphitic sublattice has three nearest neighbors, a maximum value for J was estimated at –0.5 cm–1. The small negative value of J corroborates the presence of weak antiferromagnetic coupling through the oxalate ligands in the graphitic net sublattice of 4. For compound 5, the χmT value was 0.758 cm3-K mol–1 at 300 K, which decreased rapidly to 0.509 cm3-K mol–1 at 200 K, 0.206 cm3-K mol–1 at 100 K, and 0.0067 cm3-K mol–1 at 2 K. The shape of the temperature-dependent χmT curve indicates strong antiferromagnetic coupling within the [Cu(ox)]n layer motifs. By analogy to previously reported copper oxalate complexes, the equatorial-axial carboxylate bridges and axial-axial oxygen atom bridges will


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provide weak antiferromagnetic or weak ferromagnetic coupling pathways, which would be overpowered by the strong antiferromagnetic interactions provided by the equatorial-equatorial bridging ox-A ligands.18 As a result, the magnetic data for 5 were fit to the Bleaney-Bowers expression45 for isotropically interacting pairs of S = 1/2 ions, incorporating a term to account for any paramagnetic impurities (eq. 2). The best fit to the data (Fig. 11) was given by g = 2.27(3), J = –220(6) cm–1, and ρ = 0.012(1) with R = 9.87 × 10–4. The large negative value of J is corroborative of strong antiferromagnetic coupling within the [Cu(ox)]n layer motifs.

(eq. 2)

Thermal Properties Samples of compounds 1–5 were subjected to thermogravimetric analysis to examine their dehydration and thermal degradation behaviors. Compound 1 underwent dehydration between ~60 °C and ~130 °C, with a total mass loss of 13.6 % corresponding to that expected for elimination of the water molecules of crystallization (13.3 % calc’d). Ligand ejection commenced above ~190 °C. Compound 2 lost its aqua ligands between ~100 °C and 150°C, with a total mass loss of 15.0 % (14.8 % calc’d). Between ~325 °C and ~380 °C, the compound underwent ligand combustion. Compound 3 underwent dehydration and possible loss of two equivalents of CO2 due to oxalate decomposition between ~90 °C and ~160 °C, losing 15.0 % of its mass (15.2 % calc’d). Dipyridyl ligand combustion occurred above 160 °C. Compound 4 underwent dehydration between ~110 °C and ~190 °C, losing 10.3 % of its mass (10.5 % calc’d).



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Ligand combustion occurred above 140 °C. Compound 5 underwent dehydration between ~25°C and ~160 °C, losing 9.4 % of its mass. As the expected value for loss of six molar equivalents of water is 15.3 %, it is likely that some of the water molecules of crystallization were lost upon long-term storage (> 90 d). Ligand combustion occurred above 160 °C. TGA traces for 1–5 are shown in Figs. S5–S9, respectively.

Conclusions Divalent metal oxalate coordination polymers with bis(4-pyridylmethyl)piperazine coligands show a rich variety of topologies depending on the particular metal ion employed, and also synthetic conditions. Lower temperature processes afforded simple cationic 1-D chain motifs and unligated oxalate anions in both cadmium and cobalt cases, while higher temperature resulted in a three-fold interpenetrated neutral 3D diamondoid net for cobalt. Similar 1-D chain motifs are seen in the manganese derivative, but instead of simple oxalate counterions, stacked [Mn2(ox)3]n2n– honeycomb layers serve as the anionic components. The manganese derivative thus represents the first known instance of cationic 1-D coordination polymer chains threading through anionic hexagonal layers in a 1D + 2D 3D fashion. In the copper derivative, metal oxalate layers pillared by bpmp generated a unique yet simple 4,4-connected self-penetrated network, due to a length mismatch between the closest metal-metal interlayer spacing and the span of the bpmp tethers. In most cases the structural topologies promoted by the long bpmp tethers are substantially different from previously reported analogous metal oxalate phases with embedded dipyridyl-type ligands. Antiferromagnetic interactions through the oxalate ligands are observed in all of the present cases with closely spaced paramagnetic ions, with equatorial-


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equatorial bridged copper atoms in 5 showing especially strong antiferromagnetic superexchange.

Acknowledgments We acknowledge the donors of the American Chemical Society Petroleum Research Fund and Michigan State University for funding this work. We thank Ms Amy Pochodylo and Mr Sultan Qiblawi for experimental assistance in acquiring the magnetic data.

Supporting Information Available: Crystallographic data files and thermogravimetric analysis graphs. Crystallographic data (excluding structure factors) for 1–5 have been deposited with the Cambridge Crystallographic Data Centre with Nos. 1014533, 1014535, 1014534, 910688, and 910689, respectively. Copies of the data can be obtained free of charge via the Internet at http://www.ccdc.cam.ac.uk/conts/retrieving.html or by post at CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (Fax: 44–1223336033, Email: [email protected]).



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(17) Castillo, O.; Alonso, J.; García-Couceiro, U.; Luque, A.; Román, P. Inorg. Chem. Commun. 2003, 6, 803–806. (18) Du, M.; Zhang, Z.; Li, C.; Ribas-Ariño, J.; Aliaga-Alcalde, N.; Ribas, J. Inorg. Chem. 2011, 50, 6850-6852. (19) García-Couceiro, U.; Castillo, O.; Cepeda, J.; Lanchas, M.; Luque, A.; Pérez-Yáñez, S.; Román, P.; Vallejo-Sánchez, D. Inorg. Chem. 2010, 49, 11346–11361. (20) Yang, Y.; Liu, S.; Li, C.; Li, S.; Ren, G.; Wei, F.; Tang, Q. Inorg. Chem. Commun. 2012, 17, 54–57. (21) Cui, Z.; Wang, S.; Wang, X.; Gao, D.; Sun, Y.; Zhang, G.; Xu, Y. Z. Anorg. Allgem. Chem. 2012, 638, 669–674. (22) Wang, G.; Yang, X.; Liu, Y.; Li, Y.; Du, H.; You, X. Inorg. Chem. Commun. 2008, 11, 814–817. (23) Farnum, G. A.; LaDuca, R. L. Cryst. Growth Des. 2010, 10, 1897–1903. (24) Martin, D. P.; Staples, R. J.; LaDuca, R. L. Inorg. Chem. 2008, 47, 9754–9756. (25) Blake, K. M.; Lucas, J. A.; LaDuca, R. L. Cryst. Growth Des. 2011, 11, 1287–1293. (26) Xu, B.; Zhang, T.; Zhang, L.; Li, C. C. Z. Anorg. Allgem. Chem. 2014, 640, 2503–2507. (27) Xu, B.; Li, J.; Kong, N.; Li, C. Inorg. Chem. Commun. 2014, 47, 119–122. (28) Niu, Y.; Hou, H.; Wei, Y.; Fan, Y.; Zhu, Y.; Du, C.; Xin, X. Inorg. Chem. Commun. 2001, 4, 358–361. (29) Kirschner, S. Inorganic Synthesis; Rochow, E. G., Ed.; McGraw-Hill Book Co.: New York, 1960, Vol. VI. (30) Kahn, O. Molecular Magnetism; VCH Publishers: New York, 1993. (31) SAINT, Software for Data Extraction and Reduction, Version 6.02; Bruker AXS, Inc.: Madison, WI, 2002. (32) (a) SADABS, Software for Empirical Absorption Correction. Version 2.03; Bruker AXS, Inc.: Madison, WI, 2002. (b) TWINABS (33) Sheldrick, G. M. Acta Cryst. 2008, A64, 112–122. (34) G. M. Sheldrick, CELLNOW, University of Göttingen: Göttingen, Germany, 2003.



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(35) Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Cryst. Growth Des. 2014, 14, 3576– 3586. TOPOS software is available for download at: http://www.topos.ssu.samara.ru (36) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht University: Utrecht, The Netherlands, 1998. (37) Shannon, R. D. Acta Crystallogr. 1976, A32, 751–767. (38) Datta, A.; Das, K.; Lee, J.; Jhou, Y.; Hsiao, C.; Huang, J.; Lee, H. CrystEngComm 2011, 13, 2824–2827. (39) Tong, M.; Wu, Y.; Ru, J.; Chen, X.; Chang, H.; Kitagawa, S. Inorg. Chem. 2002, 41, 4846– 4848. (40) (a) Infantes, L.; Motherwell, S. CrystEngComm 2002, 4, 454-461. (b) Infantes, L.; Chisholm, J.; Motherwell, S. CrystEngComm 2003, 5, 480-486. (41) Rueff, J. M.; Masciocchi, N.; Rabu, P.; Sironi, A.; Skoulios A. Eur. J. Inorg. Chem. 2001, 2843–2848. (42) Brown, H. A.; Luttinger, J. M. Phys. Rev. 1955, 100, 685–692. (43) Sykes, M. F.; Gaunt, D. S.; Roberts, P. D.; Wyles, J. A. J. Phys. A; Gen. Phys. 1972, 5, 624–639. (44) Bramwell, S.T.; Buckley, A.M.; Visser, D.; Day, P. Phys. Chem. Minerals 1988, 15, 465– 469. (45) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London, Ser. A. 1952, 214, 451.


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Table 1. Crystal and Structure Refinement Data for 1–5.

Data Empirical Formula Formula Weight Crystal system Space group a (Å) b (Å) c (Å) α (°) β (°) γ (°) V (Å3) Z Dcalc (g cm–3) µ (mm–1) Min./max. trans. hkl ranges

Total reflections Unique reflections R(int) Parameters R1 (all data) R1 (I > 2σ(I)) wR2 (all data) wR2 (I > 2σ(I)) Max/min residual (e–/ Å3) G.O.F.

1 C18H28CdN4O8

2 C18H28CoN4O8

3 C36H52Co2N8O14

540.86 monoclinic C2/m 10.517(2) 10.231(2) 10.343(2) 90 105.974(2) 90 1069.9(4) 2 1.679 1.074 0.8901/0.9068 –12 ≤ h ≤ 12, –11 ≤ k ≤ 12, –12 ≤ l ≤ 12 4251 1041 0.0437 104 0.0310 0.0286 0.0601 0.0591 0.676/–0.461

487.37 monoclinic C2/m 10.3702(12) 10.1090(12) 10.1846(12) 90 105.221(1) 90 1030.2(2) 2 1.571 0.888 0.9249 –12 ≤ h ≤ 12, –11 ≤ k ≤ 12, –12 ≤ l ≤ 12 4298 1007 0.0213 95 0.0356 0.0340 0.0918 0.0904 0.769/–0.735

938.72 triclinic P1ത 9.498(2) 13.441(3) 18.529(5) 109.804(4) 90.008(4) 107.135(4) 2111.6(9) 2 1.476 0.860 0.8048 –11 ≤ h ≤ 11, –16 ≤ k ≤ 15, 0 ≤ l ≤ 21 25589 7369 0.1914 539 0.2573 0.1188 0.2314 0.1804 0.955/–1.076

1.061

1.133

1.024



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Data Empirical Formula Formula Weight Crystal system Space group a (Å) b (Å) c (Å) α (°) β (°) γ (°) V (Å3) Z Dcalc (g cm–3) µ (mm–1) Min./max. trans. hkl ranges

Total reflections Unique reflections R(int) Parameters/ restraints R1 (all data) R1 (I > 2σ(I)) wR2 (all data) wR2 (I > 2σ(I)) Max/min residual (e–/ Å3) G.O.F. a

4 C22H38Mn3N4O21

5 C20H32Cu2N4O14

859.38 monoclinic C2/c 16.8729(12) 9.8999(7) 21.7246(19) 90 112.248(4) 90 3358.7(4) 4 1.700 1.203 0.7950/0.9535 –20 ≤ h ≤ 20, –11 ≤ k ≤ 11, –26 ≤ l ≤ 26 19825 3082 0.0549 254/15

679.58 monoclinic P21/c 18.0564(13) 9.2594(7) 8.2426(6) 90 100.029(1) 90 1357.03(17) 2 1.663 1.642 0.7274/0.9008 –21 ≤ h ≤ 21, –11 ≤ k ≤ 11, –9 ≤ l ≤ 9 9619 2472 0.0297 199/9

0.0474 0.0323 0.0736 0.0661 0.423/–0.342

0.0311 0.0255 0.0666 0.0637 0.401/–0.323

1.048

1.054

R1 = Σ||Fo| – |Fc||/Σ|Fo|. b wR2 = {Σ[w(Fo2 – Fc2)2]/Σ[wFo2]2}1/2.


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Table 2. Bond lengths (Å) and angles (°) within the coordination environments of 1 and 2. 1 Cd1–O2 Cd1–N1 O2#1–Cd1–O2 O2#2–Cd1–O2 O2–Cd1–O2#3 O2#2–Cd1–N1 O2–Cd1–N1 N1#3–Cd1–N1

2.3070(18) 2.314(3) 89.64(9) 90.36(9) 180.0 90.45(7) 89.55(7) 180.0

2 Co1–O2 Co1–N1 O2–Co1–O2#4 O2–Co1–O2#5 O2–Co1–O2#1 O2–Co1–N1 O2#4–Co1–N1 N1–Co1–N1#5

2.1101(15) 2.143(3) 180.0 89.92(8) 90.08(8) 90.25(6) 89.75(6) 180.0

Symmetry transformations: #1 x, –y + 1, –z; #2 –x + 2, y, –z; #3 –x + 2, –y + 1, –z; #4 –x, –y + 1, –z + 1; #5 –x, y + 1, –z + 1.



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

Table 3. Bond lengths (Å) and angles (°) within the coordination environments of 3. Co1–O1 Co1–O2 Co1–O5 Co1–O6 Co1–N1 Co1–N3 O1–Co1–O2 O1–Co1–O5 O1–Co1–O6 O1–Co1–N1 O1–Co1–N3 O2–Co1–N1 O2–Co1–N3 O5–Co1–O2 O5–Co1–N1 O5–Co1–N3 O6–Co1–O2 O6–Co1–O5 O6–Co1–N1 O6–Co1–N3 N3–Co1–N1

2.059(10) 2.114(10) 2.098(10) 2.094(10) 2.123(11) 2.118(12) 80.5(4) 172.5(3) 96.2(4) 94.6(4) 89.9(4) 91.6(4) 168.8(4) 93.3(4) 89.9(4) 95.8(4) 90.2(3) 79.5(4) 169.3(4) 85.0(4) 95.0(5)

Co2–O3 Co2–O4 Co2–O7#1 Co2–O8#1 Co2–N5 Co2–N7 O3–Co2–N7 O4–Co2–O3 O4–Co2–O7#1 O4–Co2–N5 O4–Co2–N7 O7#1–Co2–O3 O7#1–Co2–N7 O8#1–Co2–O3 O8#1–Co2–O4 O8#1–Co2–O7#1 O8#1–Co2–N5 O8#1–Co2–N7 N5–Co2–O3 N5–Co2–O7#1 N5–Co2–N7

2.124(10) 2.079(9) 2.120(10) 2.059(10) 2.103(12) 2.133(11) 166.4(4) 79.5(4) 92.9(4) 95.6(4) 87.0(4) 89.7(3) 90.5(4) 95.9(4) 171.2(3) 79.6(4) 91.5(4) 97.5(4) 86.8(4) 170.1(5) 95.1(5)

Symmetry transformations: #1 x + 1, y, z.


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Table 4. Bond lengths (Å) and angles (°) within the coordination environments of 4. Mn1–O1#1 Mn1–O1 Mn1–O2 Mn1–O2#1 Mn1–N1#1 Mn1–N1 O2#1–Mn1–N1#1 O1#1–Mn1–N1 O1–Mn1–N1 O2–Mn1–N1 O2#1–Mn1–N1 N1#1–Mn1–N1 O1#1–Mn1–O1 O1#1–Mn1–O2 O1–Mn1–O2 O1#1–Mn1–O2#1 O1–Mn1–O2#1 O2–Mn1–O2#1 O1#1–Mn1–N1#1 O1–Mn1–N1#1 O2–Mn1–N1#1

2.150(2) 2.1499(19) 2.2389(19) 2.2389(19) 2.254(2) 2.254(2) 84.02(7) 95.94(8) 94.25(8) 84.02(7) 86.99(7) 166.67(12) 80.20(10) 172.52(7) 92.33(7) 92.33(7) 172.52(7) 95.14(10) 94.25(8) 95.94(8) 86.99(7)

Mn2–O7 Mn2–O8#2 Mn2–O3 Mn2–O5 Mn2–O6#3 Mn2–O4#4 O7–Mn2–O8#2 O7–Mn2–O3 O8#2–Mn2–O3 O7–Mn2–O5 O8#2–Mn2–O5 O3–Mn2–O5 O7–Mn2–O6#3 O8#2–Mn2–O6#3 O3–Mn2–O6#3 O5–Mn2–O6#3 O7–Mn2–O4#4 O8#2–Mn2–O4#4 O3–Mn2–O4#4 O5–Mn2–O4#4 O6#3–Mn2–O4#4

2.1749(18) 2.1791(17) 2.1794(18) 2.1799(18) 2.1809(18) 2.1862(18) 75.77(6) 102.04(7) 96.92(7) 92.75(7) 99.18(7) 160.39(7) 163.56(7) 94.07(7) 91.87(7) 75.92(6) 89.46(7) 162.05(7) 75.96(7) 91.54(7) 102.52(7)

Symmetry transformations: #1 –x, y, –z + 1/2; #2 –x + 1/2, –y + 3/2, –z + 1; #3 –x, –y + 2, –z + 1; #4 –x, –y + 1, –z + 1.



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

Table 5. Bond lengths (Å) and angles (°) within the coordination environments of 5. Cu1–O1 Cu1–N1 Cu1–O4#1 Cu1–O3 Cu1–O2#2 Cu1–O2#3 O1–Cu1–N1 O1–Cu1–O4#1 N1–Cu1–O4#1 O1–Cu1–O3 N1–Cu1–O3

1.9846(14) 1.9952(18) 2.0006(14) 2.0061(14) 2.3285(14) 2.4215(14) 93.83(7) 172.74(6) 93.38(7) 89.25(6) 174.85(6)

O4#1–Cu1–O3 O1–Cu1–O2#2 N1–Cu1–O2#2 O4#1–Cu1–O2#2 O3–Cu1–O2#2 O1–Cu1–O2#3 N1–Cu1–O2#3 O4#1–Cu1–O2#3 O3–Cu1–O2#3 O2#2–Cu1–O2#3

83.49(6) 76.98(5) 98.49(6) 102.80(5) 86.22(5) 92.10(5) 87.83(6) 87.29(5) 87.94(5) 167.67(6)

Symmetry transformations: #1 –x + 1, –y + 1, –z; #2 –x + 1, –y + 2, –z; #3 –x + 1, y – 1/2, –z + 1/2.


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Scheme 1. Ligands used in this study.



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Figure 1. (a) Coordination environment in 1. (b) {[Cd(H2O)4(bpmp)](ox)}n supramolecular layer in 1. Hydrogen bonding interactions appear as dashed lines. The coordination environment and supramolecular layer motif in the isostructural cobalt analog 2 appear very similar.


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Figure 2. (a) Coordination environments in 3. (b) [Co(ox)]n chain motif in 3. (c) [Co(bpmp)]n chain motif in 3.



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Figure 3. (a) [Co(ox)(bpmp)]n single diamondoid net in 3. (b) Three-fold interpenetration of nets in 3.


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Figure 4. (a) Coordination environments in 4. (b) [Mn2(oxalate)3]n2n– honeycomb layer in 4. (c) [Mn(H2O)4(bpmp)]n2n+ coordination polymer chain in 4.



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Figure 5. (a) 1D + 2D 3D threaded-loop penetration in 4. (b) Close-up of threaded-loop penetrated of 1D chain motifs through a 2D layer aperture. (c) Schematic perspective viewed down the 1D chain motifs.


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Figure 6. (a) Coordination environments in 5. (b) [Cu2(oxalate)2]n coordination polymer layer in 5. Long axial position bonds are shown as dashed lines.



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Figure 7. [Cu2(oxalate)2(bpmp)]n 3-D coordination polymer net in 5. Water molecules of crystallization are shown in orange.


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Figure 8. (a) Schematic perspective of the 4,4-connected binodal net with self-penetrated (5383)2(5482) topology in 5. The blue and green spheres represent copper atoms and fourconnected ox-B ligands nodes, respectively. The red rods represent oxalate linkages, while the blue rods represent the bpmp ligands. (b) Close-up of self-penetrated rings in 5.



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Figure 9. χmT vs T plot for 3. The dark line represents the best fit to eq. 1.


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Figure 10. χmT vs T plot for 4.



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Figure 11. χmT vs T plot for 5. The dark line represents the best fit to eq. 2.


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Synopsis

Hydrothermal reaction of metal oxalate (ox) salts and bis(4-pyridylmethyl)piperazine (bpmp) afforded a series of structurally diverse coordination polymers. {[Cu2(ox)2(bpmp)]•6H2O}n possesses a 3D network with an unprecedented 4,4-connected self-penetrated topology. {[Mn(H2O)4(bpmp)] [Mn2(ox)3]•5H2O}n (pictured) manifests a unique 1D + 2D 3D polyrotaxane structure with 1D cationic chains threaded through apertures in stacked anionic hexagonal layers.


Structural Chemistry and Properties of Metal Oxalates Containing a

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