Paddlewheel Dimers Research Articles

Synthesis, characterization and properties of four dimeric ZnII–BMP coordination polymers modulated by a series of aromatic polycarboxylate acid

To systematically explore the influence of aromatic polycarboxylate ligands on building ZnII–BMP (1,5-bis(2-methylbenzimidazol) pentane) coordination polymers, four coordination polymers, namely {[Zn2(BMP)(PHSA)2]·H2O}n (1), [Zn4(BMP)2(BTEC)2(H2O)]n (2), [Zn2(BMP)(BTRC)(OH)]n (3), {[Zn3(BMP)(TCI)2(H2O)]·H2O}n (4) (H2PHSA=2-phenylsuccinic acid, H4BTEC=benzene-1,2,4,5-tetracarboxylic acid, H3BTRC=benzene-1,3,5-tricarboxylic acid, H3TCI=Tris (2-carboxyethyl) isocyanurate) are synthesized by varying aromatic polycarboxylate ligands. Systematic structure analysis shows that 1–4 are comprised by one or more ZnII dimer in which carboxylate ligands bridge two metal ions forming dinuclear cores, and BMP links these cores. In 1, PHSA2− bridges ZnII ions to generate paddle-wheel dimer [Zn2(η1-COO)4] and these dimers are further linked by BMP to form 2D structure. 2 exhibits a layer with two different dimers: [Zn2(η1-BTEC4−)2] and [Zn2(η1-BTEC4−)(μ2-H2O)] indicating that bridge water have subtle influences on the coordination geometry. [Zn2(η1-BTRC3−)(μ2-OH)] dimers in 3 are further linked by two kind of wavelike layers constructing the 2-fold interpenetrated 3D architecture. 4 shows a 2-fold interpenetrated 3D architecture with dimeric centre. Notably, besides ZnII dimer [Zn2(η1-TCI3−)3], a monuclear ZnII ion exists as a terminal of ligand BMP enhancing photoluminescence intensity of 4 subtlely.

Perfect Statistical Symmetrization of a Heterofunctional Ligand Induced by Pseudo-Copper Trimer in an Expanded Matrix of HKUST-1

The rare coexistence of the copper monomer and paddle-wheel dimer in the same crystal framework creates an apparent linear pseudocopper trimer configuration that induces an unprecedented equalization of pyridyl and carboxyl functionality in a heterofunctional pyridyl dicarboxylate ligand, leading to an intriguing assembly into a highly symmetrical porous framework, despite the low symmetry of the ligand. The material shows a total CO2 uptake of 55 cm3/g at 1 atm and 273 K.

Varied Layer Topologies in Luminescent Zinc Coordination Polymers with Flexible Aromatic ortho‐Dicarboxylate and Dipyridyl Ligands

AbstractHydrothermal synthesis has afforded four divalent zinc flexible‐arm aromatic ortho‐dicarboxylate coordination polymers containing dipyridyl coligands. According to X‐ray crystallography, all four show layered coordination polymer structures. Nevertheless there is significant ligand influence on the nature of zinc atom aggregation and overall topology. In both {[Zn2(hmph)2(dpa)2]·2H2O}n (1) (hmph = homophthalate, dpa = 4, 4′‐dipyridylamine), and {[Zn2(hmph)2(dpe)2](ClO4)2·H2dpe·4H2O}n (2) [dpe = bis(4‐pyridyl)ethane], large {Zn2(hmph)2} dimeric units are evident, along with an overall herringbone (6, 3) layer topology. The longer span of the dpe ligands results in larger incipient channels, which can accommodate protonated dpe dications and perchlorate counterions. In {[Zn2(hmph)2(3‐pna)]·H2O}n (3) (3‐pna = 3‐pyridylnicotinamide), {Zn2(OCO)2} anti‐syn bridged dimers and {Zn2(OCO)4} syn‐syn paddlewheel dimers coexist and are linked together by hmph and 3‐pna ligands into decorated (4, 4) grid coordination polymer layers. {[Zn(1, 2‐phda)(3‐pina)]·2H2O}n (4) (1, 2‐phda = 1, 2‐phenylenediacetate, 3‐pina = 3‐pyridylisonicotinamide) manifests an undulating (4, 4) grid structure with isolated zinc atoms; the “wavelength” of the layers measures over 40 Å. Luminescent properties of these materials are also reported.

Copper glutarate coordination polymers with dipyridylamide ligands: Effect of donor disposition and steric bulk on structure

A structurally diverse series of divalent copper glutarate coordination polymers incorporating dipyridylamide ligands has been prepared and structurally characterized. {[Cu2(glu)2(3-pina)]·3.5H2O}n (1, glu=glutarate, 3-pina=3-pyridylisonicotinamide) manifests a 3D pcu network constructed from [Cu(glu)]n layers containing {Cu2(OCO)4} paddlewheel dimers. Increasing the steric bulk of the glutarate ligand afforded [Cu2(dmg)2(3-pina)]n (2, dmg=3,3-dimethylglutarate), which shows a (4,4) grid structure based on linked [Cu(dmg)]n chains containing similar {Cu2(OCO)4} paddlewheel dimers. {[Cu(glu)(3-pna)(H2O)]·H2O}n (3, 3-pna=3-pyridylnicotinamide) has a simple (4,4) grid-like layer structure with isolated copper atoms, while {[Cu(glu)(4-pna)(H2O)]·H2O}n (4, 4-pna=4-pyridylnicotinamide) possesses a 2-fold parallel interpenetrated (6,3) herringbone lattice. Increased steric bulk and counterion inclusion in [Cu3(Hmg)2(4-pna)4(SO4)2(H2O)4]n (5, meg=2-methylglutarate) results in a 1D ribbon structure. Thermal properties are also investigated.

Copper 1D coordination polymers and dimers: Role of the carboxylate and the ammonium cation, crystal structures and magnetic studies

The 1D coordination polymers [Cu2(syn,syn-η1:η1:μ-RCOO)4(anti,anti-η1:η1:μ-RCOO)(Et3NH)]n, R=Me (1) and H (2), and the dimer [Cu2(syn,syn-η1:η1:μ-PhCOO)4(anti-η1-PhCOO)2(Et3NH)2] (3) are formed by reaction of copper carboxylates with the corresponding carboxylic acid and NEt3. Moreover, the compound [Cu2(syn,syn-η1:η1:μ-MeCOO)4(anti-η1-MeCOO)2(Et2NH2)2] (4) can be obtained with the use of NHEt2. The crystal structures of 1·CH3CN and 2 comprise linear anionic 1D chains of paddle-wheel copper carboxylates [Cu2(RCOO)4], bridged together by anti,anti-η1:η1:μ acetato or formato ions. The negative charges are balanced by hydrogen-bonded triethylammonium countercations, and in compound 1 acetonitrile molecules are hosted in the voids between the chains. In compounds 3 and 4, two anti-η1-benzoato or -acetato anions occupy the apical positions of the paddle-wheel dimers [Cu2(RCOO)4], with Et3NH+ or Et2NH2+ cations balancing the negative charges, without the formation of coordination polymer chains. In compound 4, the dimeric units are held together in a 1D network by hydrogen bonds between the apical carboxylates and the diethylammonium cations. In order to evaluate the effect of the simultaneous presence of syn,syn- and anti,anti-η1:η1:μ acetato ions on the Cu–Cu magnetic communication, the magnetic susceptibility of 1 has been measured. Data were fitted to a model based on an alternating chain of copper dimers based on the Heisenberg–Zeeman Hamiltonian (−2JŜ1·Ŝ2 convention). The results show the presence of a strong antiferromagnetic coupling within the dimer 2J1=−(310.8±0.1)cm−1 and a weak antiferromagnetic coupling between dimers 2J2=−(25±1)cm−1. The latter coupling is significant since its introduction in the fit model leads to a well-behaved error surface and to a ∼35% decrease of the sum of squared residuals. The electron paramagnetic resonance (EPR) spectra of powder sample of 1 have been recorded between 5 and 295K, and they are typical of the triplet state of an antiferromagnetic copper dimer (zero field splitting |D|=0.34cm−1).

Cadmium and zinc chain and cluster-based layered coordination polymers prepared from flexible-arm aromatic ortho-dicarboxylic acids and 4-pyridylnicotinamide

Hydrothermal reaction of a d10-metal nitrate salt, a flexible-arm aromatic ortho-dicarboxylic acid, and 4-pyridylnicotinamide (4-pna) afforded four new crystalline coordination polymers, which were characterized by single-crystal X-ray diffraction. [Cd(Hhmph)(nic)(H2O)2]n (1, hmph=homophthalate, nic=nicotinate) is a 1-D coordination polymer chain compound whose nic ligands were generated in situ via 4-pna hydrolysis. Addition of base and a shorter reaction duration afforded [Cd(hmph)(4-pna)]n (2), which has dinuclear [Cd2(hmph)2] dimers linked into a 1-D ladder polymer via 4-pna ligands. A similar chain structure, albeit with a different hmph binding mode, is seen in [Zn(hmph)(4-pna)]n (3). {[Zn2(phda)2(4-pna)2(H2O)]⋅H2O}n (4, phda=1,2-phenylenediacetate) has both anti-syn bridged [Zn2(OCO)2] ring dimers and [Zn2(OCO)4] paddlewheel dimers, linked into a layered coordination polymer by dipodal 4-pna ligands. Luminescent properties of these new materials are also presented.

Arene–perfluoroarene interactions for crystal engineering of metal complexes: Controlled self-assembly of paddle-wheel dimers

We show a new approach to control the self-assembly of paddle-wheel dimers by intermolecular multipoint arene–perfluoroarene interactions. Two types of complexes, I-shaped Rh2(O2CCF3)2(L)2(3-pentanone)2 (1) and cross-shaped Cu2(L)4(THF)2 (2) were synthesized to afford 1D chain and 2D square-grid sheet structures, respectively.

Diverse Topologies in Chiral Divalent Metal Camphorate Coordination Polymers Containing 4,4′-Dipyridylamine

Hydrothermal synthesis has afforded six chiral divalent metal coordination polymers containing d-camphorate (d-cmph) and 4,4′-dipyridylamine (dpa) ligands, whose topologies depend largely on metal coordination geometry preference. Both cadmium derivatives {[Cd(dpa)(d-cmphH)2(H2O)]·0.875H2O}n (1) and {[Cd(d-cmph)(dpa)(Hdpa)]ClO4}n (1a) exhibit one-dimensional (1-D) chains with protonated pendant ligands; 1 possesses sinusoidal chains with a “wavelength” of over 67 Å. [Zn2(d-cmph)2(dpa)(H2O)]n (2) exhibits a two-dimensional (2-D) 3,4-connected binodal net with (53)2(5482) topology. {[Ni(d-cmph)(dpa)]·3H2O}n (3) and {[M2(d-cmph)2(dpa)]·H2O}n (M = Co, 4; M = Cu, 5) manifest three-dimensional (3-D) networks. The nickel derivative has an uncommon 2-fold interpenetrated 4-connected 4284lvt topology, while the isostructural cobalt and copper complexes possess 6-connected pcu topologies based on {M2(OCO)4} paddlewheel dimers. Complexes 1/1a and 2 undergo visible light emission upon ultraviolet excitation. Variable temperature magnetic susceptibility experiments indicate weak (J = −3.6(2) cm–1) and strong (J = –202(5) cm–1) antiferromagnetic coupling for 4 and 5, respectively.

Zinc Paddlewheel Dimers Containing a Strong π···π Stacking Supramolecular Synthon: Designed Single-Crystal to Single-Crystal Phase Changes and Gas/Solid Guest Exchange

The ligand 4-(1,8-naphthalimido)benzoate, L(C4)(-), containing a linear link between the strong π···π stacking 1,8-naphthalimide supramolecular synthon and the carboxylate donor group, reacts with Zn(O(2)CCH(3))(2)(H(2)O)(2) in the presence of dimethylsulfoxide (DMSO) to yield [Zn(2)(L(C4))(4)(DMSO)(2)]·2(CH(2)Cl(2)). This compound contains the "paddlewheel" Zn(2)(O(2)CR)(4) secondary building unit (SBU) that organizes the rigid phenylene and naphthalimide rings of the carboxylate ligands in a square arrangement. The supramolecular architecture is dominated by π···π stacking interactions between naphthalimide rings of one dimer with four adjacent dimers, essentially at right angles, forming an open three-dimensional network structure. Two symmetry equivalent networks of this type interpenetrate generating overall a densely packed three-dimensional, 2-fold interpenetrated architecture in which the CH(2)Cl(2) solvate molecules are trapped in isolated pockets. Upon cooling, single crystals of [Zn(2)(L(C4))(4)(DMSO)(2)]·2(CH(2)Cl(2)) undergo two distinct crystallographic phase transitions, as characterized by X-ray diffraction at different temperatures, without loss of crystallinity. These two new phases have supramolecular structures very similar to the room temperature structure, but changes in the ordering of the CH(2)Cl(2) solvate cause shifting of the naphthalimide rings and a lowering of the symmetry. Crystals of [Zn(2)(L(C4))(4)(DMSO)(2)]·2(CH(2)Cl(2)) undergo a single-crystal to single-crystal gas/solid guest exchange upon exposure to atmospheric moisture, or faster if placed under vacuum or heated under dry gas to 100 °C, followed by atmospheric moisture, to yield [Zn(2)(L(C4))(4)(DMSO)(2)]·3.9(H(2)O). The molecular and supramolecular structures of this new compound are very similar to the dichloromethane adduct, with now the water molecules encapsulated into the framework. The remarkable feature of both the phase changes and exchange of solvates is that this robust network is not porous; local distortions (ring slippage and tilting changes) of the π···π stacking interactions of the naphthalimide rings that organize these structures allow these changes to take place without the loss of crystallinity. The complexes [Zn(2)(L(C4))(4)(DMSO)(2)]·2(CH(2)Cl(2)) and [Zn(2)(L(C4))(4)(DMSO)(2)]·3.9(H(2)O) show green emission in the solid state.

Structure and magnetic properties of a decanuclear MnII2MnIII2Dy6 aggregate

Using glycerol (H₃gly) as a primary ligand, the decanuclear aggregate [Mn(II)₂Mn(III)₂Dy₆(μ₃-OH)₂(Hgly)₄(H₂gly)₂-(PhCO₂)₁₆(H₂O)₂]·10CH₃CN (1) has been synthesised; it has a structure built up from two Mn₂Dy₂ heterocubane units linked through a central Dy₂(μ-benzoate)₄ paddle-wheel dimer and shows slow relaxation of its magnetisation.

Azacrown ether–copper(ii)–hexanoate complexes. From monomer to 1-D metal organic polymer

The synthesis and characterisation of two new Cu(ii)-hexanoate-azacrown ether species are described. The first monomeric complex is a "classical" macrocyclic Cu(ii) complex with two monodentate axially coordinated carboxylates serving as counterions. The second is an adduct of the former complex with the copper(ii) hexanoate paddlewheel dimer, Cu(2)(hexanoate)(4), forming an infinite 1-D chain of alternating monomer-dimer units. The electronic and magnetic properties of both species are discussed based on UV-vis, IR, X-ray and EPR studies combined with the DFT calculations. The UV-vis titration results prove that complex and the polymeric species are in equilibrium in toluene solution.

A Planar Carboxylate-Rich Tetrairon(II) Complex and Its Conversion to Linear Triiron(II) and Paddlewheel Diiron(II) Complexes

We report a series of oligonuclear carboxylate-rich high-spin ironII complexes with three different [FeIIn(mu-O2Cbiph)2n(L)m] (n = 2-4; m = 2 or 4) structural motifs, where -O2Cbiph is 2-biphenylcarboxylate and L is an exogenous ligand bound to terminal iron atoms. Solid compounds were isolated and their structural, spectroscopic, and magnetic properties thoroughly investigated. The discrete tetranuclear complexes [Fe4(mu-O2Cbiph)8(L)2] crystallize in a planar tetraironII motif in which two diiron paddlewheel units are linked in an unprecedented manner involving a mu3-1,1,3-bridging mode. X-ray crystallography reveals average Fe-Oanti bond lengths of 2.081[2] A at the dimer-dimer interface. Terminal axial positions are capped by ligands L, where L is tetrahydrofuran (THF) (1), indazole (2), pyrazole (3), 3,5-dimethylpyrazole (4), or acetamide (5). Reaction of 1 with an excess of acetonitrile affords the linear compound [Fe3(mu-O2Cbiph)6(MeCN)4] (6). The acetonitrile ligands in 6 can be replaced by THF or dimethoxyethane at elevated temperatures with retention of the structure to afford 7 and 8, respectively. Reaction of 1 or 6 with pyridine or 1-methylimidazole results in the isolation of paddlewheel dimers 9 and 10, respectively, with [Fe2(mu-O2Cbiph)4(L)2] composition. Mössbauer spectroscopy confirms the presence of high-spin ferrous ions and indicates that the two iron sites of the dimer are geometrically indistinguishable. For the tri- and tetrairon compounds, two quadrupole doublets are observed, suggesting that the iron centers do not have identical geometries. Plots of magnetic susceptibility versus temperature reveal intramolecular antiferromagnetic exchange coupling for all complexes under study. The magnetic data were fit to a theoretical model incorporating exchange coupling, single-ion zero-field splitting, and g-tensor anisotropy. The resulting magnetic parameters reveal in most cases weak antiferromagnetic exchange coupling (J typically <3 cm(-1)) and dominant zero-field-splitting parameters.

A new polymorph of tetra-μ-benzoato-κ8O:O′-bis[(dimethyl sulfoxide-κO)copper(II)

This paper reports a new polymorph of the title compound, [Cu2(C7H5O2)4(C2H6OS)2], a paddlewheel dimer of a tetra­benzoate-bridged dinuclear copper(II) core, with two apically positioned is dordered dimethyl sulfoxide ligands. The Cu—Cu distance is 2.6490 (6)A.

Preparation of a chiral, 2-dimensional network containing metallacrown and copper benzoate building blocks.

Chiral metallacrowns have been fused into layers using neutral copper benzoate paddlewheel dimers and nitrate anions to link each 12-MC-4 molecule. The solid contains approximately 9 Å channels that are filled with solvent and a benzoic acid guest. A related chain structure that is generated by connecting metallacrowns with the copper dimer, but which does not have nitrate bridges in the second dimension, also has channels of similar size. These observations suggest a generalizable strategy for the preparation of microporous chiral solids in bulk quantities.