Dipyridyl Ligands Research Articles

Structure and properties of coordination polymers containing hydrogen-bonding capable and conformationally flexible dipyridyl ligands: an introductory undergraduate research program at Lyman Briggs College at Michigan State University

Structure and properties of coordination polymers containing hydrogen-bonding capable and conformationally flexible dipyridyl ligands: an introductory undergraduate research program at Lyman Briggs College at Michigan State University

Palladium- and/or Copper-Catalyzed Cross-Coupling Reactions of Paramagnetic Vinyl Bromides and Iodides

A series of new 3-substituted-4-iodo-(2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yl)oxidanyl compounds is synthesized to achieve NH2- and SH-specific spin labels. The new vinyl iodides are tested in Sonogashira and Buchwald–Hartwig cross-coupling reactions to produce a paramagnetic β-amino acid ester, pyrroline nitroxide-condensed­ heterocycles, including a paramagnetic α,α′-dipyridyl ligand and a spin-labeled sulfonamide.

Structures, physicochemical and cytoprotective properties of new oxidovanadium(IV) complexes -[VO(mIDA)(dmbipy)]·1.5H2O and [VO(IDA)(dmbipy)]·2H2O

New oxidovanadium(IV) complexes with a modification of the ligand in the VO2+ coordination sphere were synthesized. [VO(mIDA)(dmbipy)]∙1.5H2O and [VO(IDA)(dmbipy)]∙2H2O were obtained as dark green crystals and grey-green powder, respectively (mIDA = N-methyliminodiacetic anion, IDA = iminodiacetic anion, dmbipy = 4,4′-dimethoxy-2,2′-dipyridyl). The crystal structure of [VO(mIDA)(dmbipy)]·1.5H2O has been determined by the X-ray diffraction method. The studies of structure of [VO(mIDA)(dmbipy)]∙1.5H2O have shown that this compound occurs in the crystal as two rotational conformers. Furthermore, the stability constants of [VO(mIDA)(dmbipy)]∙1.5H2O and [VO(IDA)(dmbipy)]∙2H2O complexes in aqueous solutions were studied by using the potentiometric titration method and, consequently, determined using the Hyperquad2008 program. Moreover, the title complexes were investigated as antioxidant substances. The impact of the structure modification in the VO2+ complexes on the radical scavenging activity has been studied. The ability to scavenge the superoxide radical by two complexes - [VO(mIDA)(dmbipy)]·1.5H2O and [VO(IDA)(dmbipy)]·2H2O was studied by cyclic voltammetry (CV) and nitrobluetetrazolium (NBT) methods. The title complexes were also examined by the spectrophotometric method as scavengers of neutral organic radical - 1,1-diphenyl-2-picrylhydrazyl (DPPH∙) and radical cation - 2,2'-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS∙+). Furthermore, the biological properties of two oxidovanadium(IV) complexes were investigated in relation to its cytoprotective properties by the MTT and LDH tests based on the hippocampal HT22 neuronal cell line during the oxidative damage induced by hydrogen peroxide. Finally, the results presented in this paper have shown that the both new oxidovanadium(IV) complexes with the 4,4′-dimethoxy-2,2′-dipyridyl ligand can be treated as the cytoprotective substances.

Multicomponent Platinum(II) Cages with Tunable Emission and Amino Acid Sensing.

The syntheses, characterization, and emission properties of three tetragonal prismatic cages, 4a-4c, constructed from eight 90° Pt(II) acceptors, four linear dipyridyl ligands, and two tetraphenylethene (TPE)-based sodium benzoate ligands, are described. These cages are emissive in dilute solutions due to the metal-coordination-induced partial restriction of intramolecular rotation of their TPE units, while the dipyridyl moieties, which act as the pillars as well as the solvents, strongly influence these emissions. Specifically, cages 4a and 4b, bearing a 4,4'-dipyridine and a 1,2-di(4-pyridyl)ethylene as their pillar parts, respectively, display good emissions in common organic solvents at 485-493 nm that are derived from the TPE units. In contrast, cage 4c, with its BODIPY-based dipyridyl unit, exhibits two emission bands at 462-473 and 540-545 nm, originating from the TPE and BODIPY fluorophores, respectively. Moreover, cage 4b has been employed as a turn-on fluorescent sensor for thiol-containing amino acids via a self-destructive reaction, while the cage can also be regenerated via the addition of Pt(II) acceptors. The studies described herein not only enrich the ongoing research on fluorescent materials but also pave the way to prepare stimuli-responsive supramolecular coordination complexes.

Control of dimensionality and topology in nickel and cobalt coordination polymers containing adamantane-based dicarboxylate and long-spanning dipyridyl ligands

Hydrothermal reaction of a metal nitrate, an adamantane-based dicarboxylic acid, and a long-spanning dipyridyl ligand produced six coordination polymers that were structurally characterized by single-crystal X-ray diffraction. [Ni2(adc)2(μ-H2O)(4-bpfh)2]n (1, adc=1,3-adamantanedicarboxylate, 4-bpfh=bis(4-pyridylformyl)homopiperazine) displays 1D coordination polymer ribbons based on [Ni2(OCO)2(μ-H2O)] dimeric units. {[Ni(adc)(4-bpfp)2(H2O)2]·H2O}n (2, 4-bpfp=bis(4-pyridylformyl)piperazine) shows a simple stacked (4,4) layer structure. {[Ni2(adc)2(3-bpmp)2(H2O)2]·15H2O}n (3, 3-bpmp=bis(3-pyridylmethyl)piperazine) also possesses stacked (4,4) grids, but with two different types of infinite water tapes in the interlamellar regions. {[Ni2(adc)2(4-bpmp)2(H2O)2]·3H2O}n (4, 4-bpmp=bis(4-pyridylmethyl)piperazine) again exhibits (4,4) layers, but with two-fold 2D+2D→2D parallel interpenetration. [Co(adc)(4-bpmp)]n (5) displays carboxylate bridged {Co2(OCO)2} cluster units pillared by adc and 4-bpmp ligands into an 8-connected 42464bcu topology. Use of the longer 1,3-adamantanediacetate (ada) ligand afforded {[Ni2(ada)2(4-bpmp)2(H2O)]·2H2O}n (6), which possesses dinuclear {Ni2(OCO)2(μ-H2O)} cluster units linked into [Ni2(ada)2(H2O)] ribbons, further connected by 4-bpmp ligands into a rare 6-connected self-penetrated 4867msw net. Variable temperature magnetic studies were undertaken in cases where dimeric units were evident; antiferromagnetic coupling was observed for 1 and 5, while ferromagnetic coupling with low temperature spin canting was observed for 6. Thermal properties of all new materials were also investigated.

Ligand-Controlled Regiodivergence in the Copper-Catalyzed [2,3]- and [1,2]-Rearrangements of Iodonium Ylides.

Despite the importance of allylic ylide rearrangements for the synthesis of complex molecules, the catalyst control of [2,3]- and [1,2]-rearrangements remains an unsolved problem. We developed the first regiodivergent [2,3]- and [1,2]-rearrangements of iodonium ylides that are controlled by copper catalysts bearing different ligands. In the presence of a 2,2'-dipyridyl ligand, diazoesters and allylic iodides react via a [2,3]-rearrangement pathway. Alternatively, a phosphine ligand favors the formation of the [1,2]-rearrangement product. A series of α-iodoesters containing a broad range of functional groups were obtained in high yields, regioselectivities, and diastereoselectivities. Deuterium-labeling studies suggest distinct mechanisms for the regioselective rearrangements.

Thermal and Magnetic Diversity in the Behaviour of the CuII‐bdc‐bpa System: 1D, 2D and Interpenetrated 3D Frameworks

Metal organic frameworks (MOFs) are crystalline materials based on connections between metal ions through organic ligands. The combination of polycarboxylate anions and dipyridyl ligands is an effective strategy for producing extended structures. In this sense, the combination of bpa with m‐bdc [bpa = 1,2‐bis(4‐pyridyl)ethane, m‐bdc = 1,3‐benzenedicarboxylate] has produced three new CuII‐based networks with different dimensionalities, namely the 1D [Cu(m‐bdc)(bpa)0.5(H2O)dmf]·0.5H2O (1, synthesis based on sonication and slow evaporation), the 2D [Cu6(m‐bdc)6(bpa)6(dmf)3]·8dmf (2, microwave synthesis) and the 3D [Cu4(m‐bdc)4(bpa)2dmf]·dmf (3, microwave synthesis). The three compounds have been structurally characterized by means of single‐crystal X‐ray diffraction, IR and UV/Vis spectroscopy and elemental analysis. An unprecedented CuII dimer has been observed for compound 3. The thermal behaviour of the compounds was analysed by thermogravimetry (TG/DSC) and X‐ray thermodifractometry (TDX), and it was concluded that the dimensionality plays an important role in their thermal properties. Electronic paramagnetic resonance and magnetic susceptibility measurements for compounds 1 and 3 showed that antiferromagnetic interactions exist between the metal ions.

Effect of pyridyl donor disposition and ligand flexibility on dimensionality in luminescent and nitrobenzene-detecting cadmium adamantanedicarboxylate coordination polymers

Hydrothermal reaction of cadmium nitrate, 1,3-adamantanedicarboxylic acid (adcH2), and a hydrogen-bonding capable and conformationally flexible dipyridyl ligand has afforded five coordination polymers with differing dimensionalities and topologies. [Cd(adcH)2(4-bpmp)]n (1, 4-bpmp=bis(4-pyridylmethyl)piperazine) exhibits 1-D chain motifs with monodentate and protonated adcH ligands. {[Cd(adc)(4-bpmp)(H2O)]·4.5H2O}n (2) displays a non-interpenetrated 4-connected 658 cds network.[Cd4(adc)4(3-bpmp)(H2O)2]n (3, 3-bpmp=bis(3-pyridylmethyl)piperazine) displays a 3D tetranodal {4462}3{446482} topology network, derived from a primitive cubic net with regularly spaced pillar vacancies. {[Cd2(adc)2(4-bpmt)2]·H2O}n (4, 4-bpmt=bis(4-pyridylmethyl)trimethylenedipiperidine) shows a decorated (4,4) grid 2D structure based on syn–syn bridged {Cd2(OCO)2} dinuclear clusters. [Cd(adcH)2(4-bpfp)]n (5, 4-bpfp=bis(4-pyridylformyl)piperazine) shows a 1-D chain structure similar to that of 1. Thermal and luminescent properties of these new phases are reported, along with surveys of their capability to serve as detectors for nitrobenzene.

Coordination Chemistry and Structural Dynamics of a Long and Flexible Piperazine-Derived Ligand.

A long and highly flexible internally functionalized dipyridyl ligand α,α'-p-xylylenebis(1-(4-pyridylmethylene)-piper-4-azine), L, has been employed in the synthesis of a series of coordination polymer materials with Co(II), Cd(II), and Ag(I) ions. In poly-[Cd(L)(TPA)] 1 and poly-[Co(L)(IPA)], 2, (TPA = terephthalate, IPA = isophthalate) the ligand adopts a similar linear conformation to that seen in the structure of the unbound molecule and provides a long (2.6 nm) metal-metal bridging distance. Due to the mismatch of edge lengths with that provided by the carboxylate coligands, geometric distortions from the regular dia and (4,4) network geometries for 1 and 2, respectively, are observed. In poly-[Ag2(CF3SO3)2(L)], 3, the ligand coordinates through both pyridine groups and two of the four piperazine nitrogen donors, forming a high-connectivity 2-dimensional network. The compound poly-[Ag2(L)](BF4)2·2MeCN, 4, a porous 3-dimensional cds network, undergoes a fascinating and rapid single-crystal-to-single-crystal rearrangement on exchange of the acetonitrile guests for water in ambient air, forming a nonporous hydrated network poly-[Ag2(L)](BF4)2·2H2O, 5, in which the well-ordered guest water molecules mediate the rearrangement of the tetrafluoroborate anions and the framework itself through hydrogen bonding. The dynamics of the system are examined in greater detail through the preparation of a kinetic product, the dioxane-solvated species poly-[Ag2(L)](BF4)2·2C4H8O2, 6, which undergoes a slow conversion to 5 over the course of approximately 16 h, a transition which can be monitored in real time. The reverse transformation can also be observed on immersing the hydrate 5 in dioxane. The structural features and physical properties of each of the materials can be rationalized based on the flexible and multifunctional nature of the ligand molecule, as well as the coordination behavior of the chosen metal ions.

Influence of Interpenetration in Diamondoid Metal–Organic Frameworks on the Photoreactivity and Sensing Properties

The degree of interpenetration is known to influence the gas sorption, catalytic, magnetic and nonlinear optical properties, chirality, and sensing of various molecules but not the solid-state [2 + 2] photocycloaddition reaction. In our previous studies of a solvothermal reaction using dimethylacetamide (DMA) as one of the solvents, a photoreactive 6-fold interpenetrated metal–organic framework with dia topology, [Zn(bpeb)(bdc)] (1) [bpeb = 1,4-bis[2-(4′-pyridyl)ethenyl]benzene; bdc = 1,4-benzenecarboxylate], was isolated. Because of the slip-stacked alignment of a dipyridyl ligand with two conjugated olefin bonds, the [2 + 2] cycloaddition reaction occurs under UV light leading to the formation of an organic polymer ligand fused with a coordination polymer, 2. On the contrary, under similar conditions when diethylformamide was used instead of DMA, a 5-fold interpenetrated structure, 3, with the same dia topology was obtained in this work. This has been found to be photostable as also predicted from the a...

Syntheses, crystal structures and properties of four novel zinc(II) complexes assembled from versatile 1,2,3,5-benzenetetracarboxylic acid and bridging dipyridyl ligands

Four novel metal–organic coordination polymers constructed from 1,2,3,5-benzenetetracarboxylic acid and bridging dipyridyl ligands, namely, [Zn(H2btec)(bpy)0.5] (1), [Zn(H2btec)(bpyE)0.5] (2), [Zn2(btec)(bpye)H2O]·2H2O (3), and [Zn(Hbtec)(Hbpyp)]·H2O (4) (H4btec=1,2,3,5-benzenetetracarboxylic acid, bpy=4,4′-bipyridine, bpyE=1,2-bis(4-pyridyl)ethylene, bpye=1,2-bis(4-pyridyl)ethane, bpyp=1,3-bis(4-pyridyl)propane) have been synthesized with hydrothermal methods and characterized by elemental analysis, IR, TGA, and single crystal X-ray diffraction. All the zinc(II) atoms are four coordinated in the four complexes, the different nitrogen coligands were found to remarkably affect the framework topologies. The zinc(II) atoms are bridged by H2btec2− with adjacent carboxylate groups into a one-dimensional double chain in complexes 1 and 2, the chains are further connected into a two dimensional sheet by the rigid dipyridyl ligands in the two complexes. However, the H4btec ligands are deprotoned into btec4− ligand and act as five-dentated ligands, which connect the zinc(II) atoms into a two-dimensional double layer with the help of flexible bpye ligands in complex 3. Interestingly, the H4btec ligands are deprotoned into Hbtec3− ligand rather than H2btec2− and btec4− in complex 4, and the three adjacent carboxylate groups connected the zinc(II) atoms into another kind of one dimensional double chain. Different from complexes 1, 2, and 3, the bpyp is protonated and acts as a terminal ligand rather than bridging one, the protonated N–H groups form hydrogen bonding interactions with the adjacent chain and thus bridging the chains into a two-dimensional sheet. Besides the coordination mode of the H4btec ligands, the final structures are also influenced greatly by the hydrogen bonding interactions of the H4btec ligands, one-dimensional channel constructed via hydrogen bonding interactions of H4btec ligands in complexes 1, 2, and 4 with dipyridyl ligands as guest molecules. Thermal stabilities and photoluminescent properties of complexes 1–4 were also examined.

Homochiral and heterochiral Mn(II) coordination frameworks: spontaneous resolution dependent on dipyridyl ligands.

An unsymmetric tetracarboxylic ligand collaborates with 4,4'-bipyridine to induce spontaneous resolution to form homochiral 3D coordination frameworks, while the use of longer dipyridyl ligands instead of 4,4'-bipyridine leads to isoreticular but heterochiral frameworks.

Homochiral coordination polymers from a chiral dicarboxylic acid and dipyridyl ligands: Structural diversity, photoluminescence and magnetic properties

Utilizing the mixed-ligand strategy, six new homochiral coordination polymers based on enantiopure (1R,2R)-1,2-cyclohexanedicarboxylic acid and varied auxiliary bipyridyl ligands, [Zn3(L)2(OH)2] (1), [Cu3(HL)2(L)2(bpy)3]·4H2O (2), [M(L)(bpe)2(H2O)2]·H2O (M=Co, 3; Ni, 4; Cd, 5), [Ni(L)(bpa)(H2O)3]·2H2O (6), [H2L=(1R,2R)-1,2-cyclohexanedicarboxylic acid, bpy=4,4′-bipyridine, bpe=1,2-bis(4-pyridyl)ethylene, bpa=1,2-bis(4-pyridyl)ethane] have been hydrothermally synthesized. Compound 1 shows a 2D 63-hcb network in the absence of any bipyridyl ligand. Compound 2 is a 2D (4,4)-connected grid network in the presence of bpy. Compounds 3–5 are isomorphous and feature 1D staggered-sculls chains by using bpe instead of bpy. Compound 6 possesses a 1D left-handed helical chain sustained by flexible bpa ligand. Each type of these coordination structures is further extended into 3D supramolecular frameworks through different intermolecular interactions. Solid-state circular dichroism (CD) spectra of compounds 1–6 exhibit strong CD signals. Magnetic susceptibility measurement indicates weak antiferromagnetic interactions between the Cu(II) ions in compound 2. Compound 5 displays a strong fluorescent emission at 413nm in solid state at room temperature.

Self‐Assembly of Oxamidato‐Chelated ReI‐ and MnI‐Based Flexible Dinuclear Horse‐Stirrup‐Like Metallacycles

AbstractThe self‐assembly of M2(CO)10 (M = Mn, Re), oxamide ligands [H2L = N,N′‐dibutyloxamide (dbo), N,N′‐dibenzyloxamide (dbno)], and flexible bidentate linkers [L′ = 1,2‐bis(4‐pyridyl)ethane (bpe), 1,3‐bis(4‐pyridyl)propane (bpp)] afforded MnI‐ and ReI‐based dinuclear metallacycles [(CO)3M(μ‐η4‐L)(μ‐L′)M(CO)3] (1–6). The oxidative addition of oxamide ligands to the equatorial sites and the addition of flexible dipyridyl ligands to the axial sites of facial metal tricarbonyl cores resulted in the formation of dinuclear metallacycles under one‐pot reaction conditions. Metallacycles 1–6 were characterized through elemental analysis, IR, UV/Vis, and NMR spectroscopy. The formation of dinuclear compounds 1 and 4 was ascertained by ESI mass spectrometry. The molecular structures of 2, 3, 5, and 6 were elucidated by single‐crystal X‐ray crystallographic methods, which revealed horse‐stirrup‐like dinuclear frameworks in which the metal centers are orthogonally connected by a bridging oxamide ligand through ON∩NO bis(chelation) and a flexible bidentate ligand through M–N coordination. The first one‐step syntheses of self‐assembled neutral MnI‐based dinuclear metallastirrups containing bis(chelating) oxamide ligands and their rhenium analogues are reported herein.

Palladium complexes bearing the dipyridyl ligand: synthesis, structural studies, and use in the Heck reaction

Two new palladium complexes derived from the di(2-pyridinyl)methanone N-(2-pyridinyl)hydrazone (DPMNPH) ligand are reported. The compounds were characterized by elemental analysis, spectroscopic studies, and, for the DPMNPH ligand, single-crystal X-ray diffraction analysis. The DPMNPH ligand crystallized as orthorhombic with the space group P212121. The H1 atom is intramolecularly bonded to the pyridinic N4 with N1–H1 = 0.92(3) A, H1···N4 = 1.87(2) A, N1···N4 = 2.615(2) A, and N1–H1···N4 = 137(2)°. Both complexes were excellent catalysts in the Heck reaction in the presence of base.

Anticancer Activity and Autophagy Involvement of Self-Assembled Arene–Ruthenium Metallacycles

A suite of six metallacycles (1–6) was generated via coordination-driven self-assembly using the three dicarboxylate-bridged arene–Ru precursors [Ru2(μ-η4-OO∩OO)(η6-p-iPrC6H4Me)2][CF3SO3]2; (OO∩OO = oxalate (A1), 2,5-dihydroxy-1,4-benzoquinonato (dobq) (A2), 5,8-dihydroxy-1,4-naphthoquinonato (donq) (A3); CF3SO3 = triflate) with one of two dipyridyl ligands (L1 and L2). The metallacycles were isolated in excellent yield (86–92%) as triflate salts and characterized by proton (1H) and carbon-13 (13C) nuclear magnetic resonance (NMR) and electrospray ionization–mass spectrometry (ESI-MS) to confirm their structural assignments. Single-crystal X-ray crystal analysis of 1 revealed that two L1 ligands bridged two A1 acceptors to form a rectangular architecture. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was conducted to evaluate the in vitro cytotoxicities relative to two chemotherapeutic agents: namely, cisplatin and doxorubicin. Metallacycles 3 and 6 potently inhibited the growth of HCT-15 human colon and AGS human gastric cancer cells. The hollow fiber (HF) assay was performed to investigate the in vivo antitumor activities of metallacycles 3 and 6. Metallacycle 6 was more effective in inhibiting HCT-15 cells than metallacycle 3 in both in vitro and in vivo studies. Moreover, 3 and 6 induced autophagic activity in HCT-15 cells. These results suggested that the autophagic response elicited by metallacycles 3 and 6 could mediate the anticancer effects observed in human colorectal cancer cells.

Cu-PDC-bpa solid coordination frameworks (PDC=2,5-pyrindinedicarboxylate; bpa=1,2-DI(4-pyridil)ethane)): 2D and 3D structural flexibility producing a 3-c herringbone array next to ideal

Combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce solid coordination frameworks (SCF) which are crystalline materials based on connections between metal ions through organic ligands. In this context, this work is focused on two novel CuII-based SCFs exhibiting PDC (2,5-pyridinedicarboxylate) and bpa (1,2-di(4-pyridyl)ethane), being the first structures reported in literature containing both ligands. Chemical formula are [Cu2[(PDC)2(bpa)(H2O)2]·3H2O·DMF (1), and [Cu2(PDC)2(bpa)(H2O)2]·7H2O (2), where DMF is dimethylformamide. Compounds 1 and 2 have been characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric (TG) analysis, differential thermal analysis (DTA) and dielectric measurements. The crystallographic analysis revealed that compounds 1 and 2 can be described as herringbone-type layers formed by helicoidal Cu-PDC-Cu chains connected through bpa ligands. Solvent molecules are crystallized between the layers, providing the inter-layer connections through hydrogen bonds. Differences between both compounds are attributable to the flexibility of bpa (in 2D) as well as to the 3D packing of the layers which is solvent dependent. This fact results in the fact that compound 2 is the most regular 3-c herringbone array reported so far. The structural dynamism of these networks is responsible for the crystalline to-amorphous to-crystalline (CAC) transformation from compound 1 to compound 2. Crystallochemical features for both compounds have also been studied and compared to similar 3-connected herringbone-arrays.

Structure of a Porous Cu2(pzdc)2(bpp) (pzdc: Pyrazine-2,3-dicarboxylate, bpp: 1,3-Bis(4-pyridyl)propane) Coordination Polymer and Flexibility upon Concomitant Hysteretic CO2 Adsorption

A porous coordination polymer was prepared using pyrazine-2,3-dicarboxylate (pzdc) and a dipyridyl ligand that contains −CH2CH2CH2– as a spacer, namely, 1,3-bis(4-pyridyl)propane (bpp). The material was thoroughly tested for determination of textural and adsorption properties in an attempt to elucidate structural flexibility in the absence of a gate opening pressure phenomenon. The periodic framework (monoclinic, P21/c, a = 13.300(3), b = 13.112(7), c = 10.808(5) Å, β = 101.28(4)°) composition is Cu2(pzdc)2(bpp))·4H2O, with an overall structural arrangement similar to those present in other two-dimensional copper + pzdc based coordination polymers, but showcasing a heavily distorted, parallelogram-shaped gallery along c. The structure appears stable up to 510 K based on thermogravimetric analysis and in situ high temperature X-ray diffraction data; complete elimination of water takes place at 373 K. Upon activation, the material effective surface area and pore volume are much smaller than those of other Cu2(pzdc)2 structures, probably because of the constricted void space. Still, a corrected Horvath–Kawazoe pore size distribution analysis method points to a 4.2 Å average pore size. Uptake of CO2 at 194.5 K revealed a hysteretic adsorption–desorption phenomenon, probably due to a concomitant pore width expansion process that is analogous to the one reported for Cu2(pzdc)2(bpy) (bpy: 4,4′-bipyridine). The phenomenon is amplified at 298 K and remains at pressures up to 50 atm of CO2. Furthermore, it appears that the dynamics of structural changes are slower compared to those of the adsorption process; equilibrium seems to take place at an equilibration time interval of at least 120 s. In contrast with isostructural Cu2(pzdc)2(dpyg) (dpyg: 1,2-di(4-pyridyl)-glycol), Cu2(pzdc)2(bpp) appears to have a stronger interaction with CO2 as evidenced by the isosteric heats of adsorption profiles and probably due to the flexibility introduced by the bpp ligand.

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

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) show 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 threefold 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 self-penetrated (5383)2(5482) topology. Variable temperature magnetic susceptibility studies showed weak antiferromagnetic coupling along [Co(ox)]n chain submotifs in 3 with concomitant zero-field 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).

Thermal stability of ionic nets with CuII ions coordinated to di-2-pyridyl ketone: Reversible crystal-to-crystal phase transformation

Supramolecular networks are crystalline materials based on connections between metal ions through organic ligands. In this sense, the combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce extended structures. However, sometimes the 3D arrangement results in an ionic network, and this is the case for the novel compounds [Cu((py)2C(OH)2)2](H2bta) (1) and [Cu((py)2C(OH)2)2](fum) (2) where (py)2C(OH)2 is the gem-diol of di-2-pyridyl ketone ((py)2CO), H2bta2− is the divalent anion of 1,2,4,5-benzenetetracarboxylic acid (H4bta), and fum2− is the divalent anion of fumaric acid (butenedioic acid). Both compounds were synthesized and structurally characterized by means of single crystal X-ray diffraction and IR spectroscopy. The thermal behavior of both compounds was analyzed through TG/DTA and TDX, concluding that the thermal stability is influenced by the dehydration of the coordinated molecules and counter-anions. Additionally, 13C NMR measurements were performed to analyze the reversible crystal-to-crystal phase transformation observed for 1.