Mixed Coordination Research Articles

Three-dimensional vibration analysis of multilayered composite and functionally graded piezoelectric plates and shells

In the present paper, a coupled 3D exact electro-elastic shell model for Functionally Graded (FG) and composite piezoelectric structures is proposed. Primary variables of the electro-elastic model are the electric potential and the three displacement components. The model allows to evaluate the piezoelectric effect in terms of frequencies and vibration modes. Both closed and open circuit configurations are analyzed and compared. The 3D equilibrium equations and the 3D divergence electric displacement equation for spherical shells give the set of partial differential equations for the electro-elastic problem. The proposed model for spherical shells automatically degenerates into simpler models for plates and cylindrical shells via properly considerations on radii of curvature along in-plane directions. The orthogonal mixed curvilinear coordinates α, β and z are employed. The partial differential governing equations have constant coefficients considering fictitious layers and they are solved using the Navier harmonic form and the exponential matrix method. These features lead to an exact solution for simply-supported boundary conditions. Free vibration analyses are conducted and circular frequencies for the first three thickness vibration modes are computed. After a global assessment phase to verify the correctness of the developed model, new benchmarks are proposed: different thickness ratios and material configurations are investigated. The present work can be intended as a reference general solution for those scientists interested in the study of piezoelectric structures via 2D analytical and numerical formulations.

Synthesis and characterization of the Cu(II)-quinoxaline, 3,3-thiodipropionate mixed ligand coordination polymer for the removal of methylene blue from aqueous solution

Herein, we report the removal of methylene blue (MB) dye from water by Cu(II)-quinoxaline, 3,3-thiodipropionate mixed ligand coordination polymer synthesized as [Cu2(TDPH)4(QNX)]·DMF. Characterization of the synthesized material was carried out by elemental analysis, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and UV–visible spectroscopy. ν(C = O) and ν(C–O) absorption bands were detected at 1735 and 1093 cm−1, respectively, while ν(C = N) was observed at 1608 cm−1 in the synthesized compound. The synthesized material was used as adsorbent for the removal of MB dye from aqueous solution using batch adsorption technique. The maximum adsorption capacity was found to be 7.9745 mg/g, while the maximum decolorization efficiency for the adsorbent was observed to be 99.04%. Adsorption data from the study fitted the Langmuir isotherm with an R 2 value of 0.9815, while the adsorption kinetics followed the pseudo-second-order kinetic model with an R 2 value of 0.9953. The results obtained from the study, therefore showed that the synthesized materials could be used as adsorbents in wastewater treatment.

Promoting the Anticancer Activity with Multidentate Furan-2-Carboxamide Functionalized Aroyl Thiourea Chelation in Binuclear Half-Sandwich Ruthenium(II) Complexes.

A new set of binuclear arene ruthenium complexes [Ru2(p-cymene)2(k4-N2OS)(L1-L3)Cl2] (Ru2L1-Ru2L3) encompassing furan-2-carboxamide-based aroylthiourea derivatives (H2L1-H2L3) was synthesized and characterized by various spectral and analytical techniques. Single-crystal XRD analysis unveils the N^O and N^S mixed monobasic bidentate coordination of the ligands constructing N, S, Cl/N, O, and Cl legged piano stool octahedral geometry. DFT analysis demonstrates the predilection for the formation of stable arene ruthenium complexes. In vitro antiproliferative activity of the complexes was examined against human cervical (HeLa), breast (MCF-7), and lung (A549) cancerous and noncancerous monkey kidney epithelial (Vero) cells. All the complexes are more efficacious against HeLa and MCF-7 cells with low inhibitory doses (3.86-11.02 μM). Specifically, Ru2L3 incorporating p-cymene and -OCH3 fragments exhibits high lipophilicity, significant cytotoxicity against cancer cells, and lower toxicity on noncancerous cells. Staining analysis indicates the apoptosis-associated cell morphological changes expressively in MCF-7 cells. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) analyses reveal that Ru2L3 can raise ROS levels, reduce MMP, and trigger mitochondrial dysfunction-mediated apoptosis. The catalytic oxidation of glutathione (GSH) to its disulfide form (GSSG) by the complexes may simultaneously increase the ROS levels, alluding to their observed cytotoxicity and apoptosis induction. Flow cytometry determined the quantitative classification of late apoptosis and S-phase arrest in MCF-7 and HeLa cells. Western blotting analysis confirmed that the complexes promote apoptosis by upregulating Caspase-3 and Caspase-9 and downregulating BCL-2. Molecular docking studies unfolded the strong binding affinities of the complexes with VEGFR2, an angiogenic signaling receptor, and BCL2, Cyclin D1, and HER2 proteins typically overexpressed on tumor cells.

Chemical CO2 fixation using a cyanido bridged heterometallic Zn(II)-Mn(II) 2D coordination polymer.

A new cyanido bridged Zn(II)-Mn(II) mixed-metal coordination polymer, {[Zn(μ-L)(μ-CN)2Mn0.5]·(CH3OH)}n (1), has been synthesized by the reaction of Zn(CN)2, Mn(II) salts and a hydrazone ligand (HL = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide) in methanol. Compound 1 was characterized using various analytical methods (including elemental analysis, photoluminescence, FT-IR, XRD, SEM, and EDX analyses, and TGA), and its structure was determined by X-ray analysis. These analyses confirmed the formation of a mixed metal Zn(II)-Mn(II) coordination polymer containing both cyanide and hydrazone bridging ligands. This mixed metal coordination polymer exhibits interesting emission spectra by having several emissions via excitation at 230, 270, 375 and 385 nm. The catalytic activity of compound 1 in chemical CO2 fixation was investigated in the presence of epoxides, and the effects of various parameters on its catalytic performance were evaluated. The results of catalytic studies show that compound 1 can efficiently catalyze the chemical CO2 fixation reaction under mild conditions. The amount of co-catalyst, temperature of the reaction, nature of the solvent and also the substituent connected to the epoxide ring are some of the important parameters that have considerable effects on the catalytic activity of 1.

Spectroscopic and thermal studies of mixed ligand coordination compounds of cobalt (II) with aspartic and dicarboxylic acids

The synthesis of complex compounds of cobalt (II) ion in the presence of aspartic and dicarboxylic acids has been studied by thermal and spectroscopic methods. Thermal decomposition processes of these compounds are studied on the basis of thermal analysis, and endo- and exoeffects are determined. The decomposition products of the compounds were studied on the basis of mass reduction by the thermogravimetric method. Based on the results of spectroscopic studies, the structural formulas of the synthesized coordination compounds are established.

Evidence for Mixed Mg Coordination Environments in Silicate Glasses: Results from 25Mg NMR Spectroscopy at 35.2 T.

The Mg-O coordination environment of silicate glasses of composition CaMgSi2O6, Na2MgSi3O8, and K2MgSi5O12 is probed using ultrahigh-field (35.2 T) 25Mg magic angle spinning nuclear magnetic resonance (MAS NMR) and triple-quantum MAS NMR spectroscopy. These spectra clearly reveal the coexistence of 4-fold- (MgIV) and 6-fold- (MgVI) coordinated Mg in all glasses. The MgIV/MgVI ratio implies an average Mg-O coordination number of ∼5 for CaMgSi2O6 glass, bringing NMR results for the first time in good agreement with those reported in previous studies based on diffraction and X-ray absorption spectroscopy, thus resolving a decade-long controversy regarding Mg coordination in alkaline-earth silicate glasses. The Mg-O coordination number decreases to ∼4.5 in the alkali-Mg silicate glasses, indicating that Mg competes effectively with the low field strength alkali cations for the nonbridging oxygen in the structure to attain tetrahedral coordination. This work illustrates the promise of ultrahigh-field NMR spectroscopy in structural studies involving nuclides with low gyromagnetic ratio.

On the experimental dynamic substructuring of rotating machine foundations

The dynamic behavior of a rotating machine consists not only of the response of the shaft, but it also contains information of all supporting structures and equipment interacting with the rotor. These support structures, also named foundations, can add substantial influence on the machine operational behavior, hence it becomes necessary to dynamically characterize its components. This study presents the application of substructuring techniques in assembling a supporting structure model for a rotating machine and presents a novel formulation of the mixed coordinates method, which is used to connect rotor and foundation. This foundation model is validated against the actual physical foundation and provides an efficient way to analyze and optimize the behavior of such systems. The robustness of the substructuring technique is demonstrated by comparing the responses of the global system solved with both the dynamically assembled and experimentally measured supporting structures in free-free and clamped conditions. The simulations reveal important phenomena of the complete system, including the presence of structural modes in the Campbell diagrams and in displacement responses. The technique allows flexibility in the design of numerical foundations without requiring physical mounting and measurements.

Synthesis and characterized three Zn(II)-based mixed geometry coordination polymers and photocatalytic activity against dyes

Three novel Zn(II)-based CPs (coordination polymers) with formula [Zn3(μ3-OH)(L)(H2O)5]n (1), [Zn5(L)2(bpz)2(H2O)2]n (2) and [Zn2(HL)(bip)(H2O)2·H2O]n (3) (H5L = 3,5-di(2ʹ,4ʹ -dicarboxyphenyl)benozoicacid, bpz = 3,3ʹ,5,5ʹ-tetramethyl-4,4ʹ-bipyrazole and bip = 3,5-bis(1-imidazoly)pyridine have been synthesized hydrothermally by O and N donor ligands. The single x-ray diffraction reveals that CPs are mixed geometry. In CP 1, Zn1 is square pyramidal geometry and Zn3 is distorted octahedral. In CP 2, Zn1 is tetrahedral; Zn2 is distorted octahedral and Zn3 is square pyramid geometry. In CP 3, Zn metals are distorted octahedral. By interacting with intra- and intermolecular hydrogen bonds, all CPs are stable. The nature of these CPs is semiconducting. Methyl blue (MB), Methyl orange (MO), Methyl violet (MV), and Rhodamine B (RhB) are examples of organic pollutants against which the photocatalytic activity of CPs is studied. CP 3 (25 mg) have higher photocatalytic activity against MV (20 ppm) under pH 6 condition.

Ice rule breakdown and frustrated antiferrotoroidicity in an artificial colloidal Cairo ice

We combine experiments and numerical simulations to investigate the low energy states and the emergence of topological defects in an artificial colloidal ice in the Cairo geometry. This type of geometry is characterized by a mixed coordination (z), with coexistence of both z = 3 and z = 4 vertices. We realize this particle ice by confining field tunable paramagnetic colloidal particles within a lattice of topographic double wells at a one to one filling using optical tweezers. By raising the interaction strength via an applied magnetic field, we find that the ice rule breaks down, and positive monopoles with charge accumulate in the z = 4 vertices and are screened by negative ones () in the z = 3. The resulting, strongly coupled state remains disordered. Further, via analysis of the mean chirality associated to each pentagonal plaquette, we find that the disordered ensemble for this geometry is massively degenerate and it corresponds to a frustrated antiferrotoroid.

Unusual large pore copper silicate for CO2 adsorption

The variable ratio of tetrahedrally coordinated atoms with different valences in the zeolite framework determines the amount and distribution of extraframework cations, thereby regulating properties such as adsorption, separation, and catalysis. However, similar control is not possible for stoichiometric microporous mixed coordination polyhedra silicates. Here we identify synthesis conditions that reduce or completely eliminate the alkali cations in the 12-ring channels of a copper silicate while preserving the original framework stoichiometry that enables CO2 adsorption. Furthermore, despite the absence of cation positions, the emptied channels can undergo ion exchange and accommodate substantial amounts of Cs+ and Sr2+ ions. These results introduce a pioneering example of cation-free large pores in transition metal silicates and demonstrate how the same framework heteropolyhedral silicates can exhibit significantly distinct pore composition and adsorption properties controlled by the synthesis.

Track-before-detect for bistatic radar based on pseudo-spectrum

Track-Before-Detect (TBD) is an efficient method to detect dim targets for radars. Conventional TBD usually follows an approximate motion model of the target, which may cause an inaccurate integration of the target energy. A TBD technique on basis of pseudo-spectrum in mixed coordinates adopting an accurate motion model for bistatic radar system is developed in this paper. The predicted position in bistatic polar plane is derived according to a nonlinear function that exactly describes the constant Cartesian velocity motion. Then around the predicted position, a pseudo-spectrum is formulated and its samples are accumulated to the integration frame for energy integration. The evolution of the state and the procedure of accumulation of the target energy are derived elaborately. The superior performance of the proposed method is demonstrated by some simulations.

Symmetrical and Unsymmetrical Dicopper Complexes Based on Bis-Oxazoline Units: Synthesis, Spectroscopic Properties and Reactivity

Copper–oxygen adducts are known for being key active species for the oxidation of C–H bonds in copper enzymes and their synthetic models. In this work, the synthesis and spectroscopic characterizations of such intermediates using dinucleating ligands based on a 1,8 naphthyridine spacer with oxazolines or mixed pyridine-oxazoline coordination moieties as binding pockets for copper ions have been explored. On the one hand, the reaction of dicopper(I) complexes with O2 at low temperature led to the formation of a µ-η2:η2 Cu2:O2 peroxido species according to UV-Vis spectroscopy monitoring. The reaction of these species with 2,4-di-tert-butyl-phenolate resulted in the formation of the C–C coupling product, but no insertion of oxygen occurred. On the other hand, the synthesis of dinuclear Cu(II) bis-µ-hydroxido complexes based on pyridine–oxazoline and oxazoline ligands were carried out to further generate CuIICuIII oxygen species. For both complexes, a reversible monoelectronic oxidation was detected via cyclic voltammetry at E1/2 = 1.27 and 1.09 V vs. Fc+/Fc, respectively. Electron paramagnetic resonance spectroscopy (EPR) and UV-Vis spectroelectrochemical methods indicated the formation of a mixed-valent CuIICuIII species. Although no reactivity towards exogeneous substrates (toluene) could be observed, the CuIICuIII complexes were shown to be able to perform hydroxylation on the methyl group of the oxazoline moieties. The present study therefore indicates that the electrochemically generated CuIICuIII species described herein are capable of intramolecular aliphatic oxidation of C–H bonds.

Geometrical control of topological charge transfer in Shakti-Cairo colloidal ice

Lattice transformations that preserve the system topology, but not its geometry, are common in condensed matter systems. However, how geometric constrains influence the topological properties of the lattices is still unclear. Here we show that a geometric transformation between two mixed coordination lattices, from Shakti to Cairo in an artificial colloidal ice, leads to a breakdown of the ice rule in all but one specific geometry. We observe a transfer of topological charge among sublattices which can be controlled in sign and intensity, vanishing at the ice-rule point. These unusual topological effects are absent in magnetic spin ices and they are due to collective, non-local geometric frustration in the particle ice. By merging numerical simulations, theory and experiments, we demonstrate how the charge transfer occurs in the Cairo geometry. The broader implication of our results is that we demonstrate how geometric constraints can control the topological properties of a mesoscopic colloidal system.

Hygro-Elastic Coupling in a 3D Exact Shell Model for Bending Analysis of Layered Composite Structures

In this work, a 3D fully coupled hygro-elastic model is proposed. The moisture content profile is a primary variable of the model’s displacements. This generic fully coupled 3D exact shell model allows the investigations into the consequences arising from moisture content and elastic fields in terms of stresses and deformations on different plate and shell configurations embedded in composite and laminated layers. Cylinders, plates, cylindrical and spherical shells are analyzed in the orthogonal mixed curvilinear reference system. The 3D equilibrium equations and the 3D Fick diffusion equation for spherical shells are fully coupled in a dedicated system. The main advantage of the orthogonal mixed curvilinear coordinates is related to the degeneration of the equations for spherical shells to simpler geometries thanks to basic considerations of the radii of curvature. The exponential matrix method is used to solve this fully coupled model based on partial differential equations in the thickness direction. The closed-form solution is related to simply supported sides and harmonic forms for displacements and the moisture content. The moisture content amplitudes are directly applied at the top and bottom outer faces through steady-state hypotheses. The final system is based on a set of coupled homogeneous second-order differential equations. A first-order differential equation system is obtained by redoubling the number of variables. The moisture field implications are evaluated for the static analysis of the plates and shells in terms of displacement and stress components. After preliminary validations, new benchmarks are proposed for several thickness ratios, geometrical and material data, lamination sequences and moisture values imposed at the external surfaces. In the proposed results, there is clearly accordance between the uncoupled hygro-elastic model (where the 3D Fick diffusion law is separately solved) and this new fully coupled hygro-elastic model: the differences between the investigated variables (displacements, moisture contents, stresses and strains) are always less than 0.3%. The main advantages of the 3D coupled hygro-elastic model are a more compact mathematical formulation and lower computational costs. Both effects connected with the thickness layer and the embedded materials are included in the conducted hygro-elastic analyses.

Salts and double tartratogermanates/stannates of 3d-metals as modifiers of unsaturated oligoesters

The paper presents the results of the systematic research into effects of 3d-metals acetates, acetylacetonates and double tartrategermanates/stannates on the modification of polyglycol maleine phthalate. The copolymerization parameters of the prepared modified oligoesters with methyl methacrylate monomer and threeethyleneglycoldimethacrylate oligomer were determined. Modifiers were added to the reaction mixture before the start of polycondensation of maleic and phthalic anhydrides with ethylene glycol at the temperature of 1750C. The kinetics of copolymerization at the initial stages was determined by the dilatometry at the temperatures of 500C to 600C. It was established that the modification of polyglycol maleinate phthalate with the studied compounds allows significantly increasing the rate and reducing the temperature coefficient of the copolymerization reaction. There advantages of the investigated double multi-metal mixed ligand coordination compounds as modifiers were proved as compared to the standard industrial systems, acetylacetonates and metal acetates. The presented modifiers are able to improve significantly the characteristics of the semi-finished products in the industrial manufacturing of copolymers without the significant change of the technological process.

A Layer-Wise Coupled Thermo-Elastic Shell Model for Three-Dimensional Stress Analysis of Functionally Graded Material Structures

In this work, a coupled 3D thermo-elastic shell model is presented. The primary variables are the scalar sovra-temperature and the displacement vector. This model allows for the thermal stress analysis of one-layered and sandwich plates and shells embedding Functionally Graded Material (FGM) layers. The 3D equilibrium equations and the 3D Fourier heat conduction equation for spherical shells are put together into a set of four coupled equations. They automatically degenerate in those for simpler geometries thanks to proper considerations about the radii of curvature and the use of orthogonal mixed curvilinear coordinates α, β, and z. The obtained partial differential governing the equations along the thickness direction are solved using the exponential matrix method. The closed form solution is possible assuming simply supported boundary conditions and proper harmonic forms for all the unknowns. The sovra-temperature amplitudes are directly imposed at the outer surfaces for each geometry in steady-state conditions. The effects of the thermal environment are related to the sovra-temperature profiles through the thickness. The static responses are evaluated in terms of displacements and stresses. After a proper and global preliminary validation, new cases are presented for different thickness ratios, geometries, and temperature values at the external surfaces. The considered FGM is metallic at the bottom and ceramic at the top. This FGM layer can be embedded in a sandwich configuration or in a one-layered configuration. This new fully coupled thermo-elastic model provides results that are coincident with the results proposed by the uncoupled thermo-elastic model that separately solves the 3D Fourier heat conduction equation. The differences are always less than 0.5% for each investigated displacement, temperature, and stress component. The differences between the present 3D full coupled model and the the advantages of this new model are clearly shown. Both the thickness layer and material layer effects are directly included in all the conducted coupled thermal stress analyses.

Self-template synthesis of CuCo2O4 nanosheet-based nanotube sorbent for efficient Hg0 removal

Adsorption method is an effective way to remove Hg0 from flue gas, and the morphology and active site of sorbents seriously affect the Hg0 removal efficiency. The hierarchical porous nanosheet-based nanotube structure can effectively reduce the mass transfer resistance and provide more active sites. Inspired by this, the organic-inorganic hybrid nanowires of Co-aspartic acid was used as the template, which can hydrolyze in water-alcohol mixed solution and coordinate with Cu2+ based on Kirkendall effect to prepare nanosheet-based nanotube of CuCo2O4 sorbents. By changing the ratio of water to alcohol, the hydrolysis rate of Co-aspartic acid nanowires will be changed resulting in different physicochemical properties for CuCo2O4 sorbents. Characterization results show that when the ratio is 1:2, the sorbent (CuCo2O4-1-2) has the best hierarchical porous nanosheet-based nanotube structure and the best redox properties. CuCo2O4-1-2, which has the widest reaction temperature window, has a high Hg0 removal efficiency of 89 % under a high GHSV of 180 000 h−1 at 250 °C and a good poisoning resistance and stability. The straight nanotube can effectively reduce the gas transfer mass resistance, and the mesoporous nanosheets structure on its surface provide more active sites for the reaction, which improves the ability of CuCo2O4-1-2 sorbent to capture and activate O2. Meanwhile, DFT calculation shows Cu-Co on the surface of CuCo2O4 is the main active site because the bond length of OO can be effectively lengthened when O2 is adsorbed on the Cu-Co site.

Pseudo-spectrum-based multi-sensor multi-frame detection in mixed coordinates

Multi-sensor track-before-detect (MS-TBD) can greatly enhance the weak target detection ability due to utilizing multi-frame (MF) data from multiple sensors. However, in the existing MS-TBD methods, when the resolutions of the MS are different, the target echoes obtained by the MS are arranged to the measurement space with unified resolution. This process may remove some valuable information of raw sensor data or introduce additional noise, which may lead to inadequate integration of the echo energy and degradation of the output envelope. For the sake of solving the issues mentioned above, a pseudo-spectrum (PS) method in mixed coordinates is investigated for TBD in MS systems. For each sensor, the conversion of each measurement cell's position from sensor coordinates to Cartesian coordinates is carried out and the prediction of that is conducted with an assumed velocity in Cartesian framework. Then the predicted position is converted back to global sensor coordinates, which takes one of the sensors as the origin. A PS is designed around the predicted global polar position and its samples are added to the integration frame for MF accumulation. This avoids additional spatial alignment and facilitates well-maintained target envelope, leading to effective energy integration and the improvement of estimation accuracy. The procedures of coordinate transformation and MF accumulation in multiple sensors are derived and the analysis of theoretical output SNR is provided. The effectiveness and the superiority of the proposed method is demonstrated by several simulations.

Biofouling-resistant polyamidoxime-based natural hierarchical porous bamboo strips prepared by in-situ polymerization for uranium extraction from seawater

Effectively extracting uranium (VI) [U(VI)] from seawater requires efficient adsorbents. Generally, there are two major factors that affect the adsorption efficiency of adsorbents, including the biofouling around the adsorbents and the relative density of adsorption active sites. To enhance the practical application value of powdered polyamidoxime-based materials, macro-braidable and hierarchical porous bamboo strips (BS) with antibacterial properties are selected to synthetize polyamidoximized bamboo strips (PAOBS) by in-situ polymerization methods. On the one hand, natural BS have a bamboo quinone structure, and their intrinsic structure is not destroyed during the reaction process, which endows PAOBS with excellent antibacterial properties. In addition, PAOBS retains the hierarchical porous structure of BS, providing channels for the adsorption process, which is beneficial to achieve the maximum utilization of adsorption active sites. On the other hand, PAOBS increases the relative density of amidoxime functional groups, and its adsorption capacity (233 mg g−1) is approximately 2.14 times higher than that of pure PAO at pH= 6.0, including electrostatic effect and chelation mechanism. After PAOBS is floated in the Yellow Sea Basin for 30 days, its adsorption capacity for U(VI) reaches 1.03 mg g−1. Importantly, the addition of BS increases the coordination modes with the uranyl ion, and the single coordination mode of CH(NH2)=N-OH from PAO is translated to the three mixed coordination modes of CH(NH2)=N-OH, CH(NH2)=N-OH, and CH(NH2)=N-OH and adjacent CH(NH2)=N-OH from PAOBS. Construction of PAOBS plays a role in the design of novel adsorbents with high relative density of adsorption active sites and biofouling-resistant, laying the steady foundation for further realizing sustainable U(VI) extraction from seawater.

Slow Magnetic Relaxation in Cobalt(II) Complexes with One-Dimensional Hydrogen-Bonded Networks

Two new cobalt(II) complexes with an unsymmetrical bidentate ligand, 2-(1,4,5,6-tetrahydropyrimidin-2-yl)-6-methoxyphenol (H2mthp), were synthesized and crystallographically characterized. Tetra- and hexa-coordinate mononuclear complexes were selectively obtained by adjusting the stoichiometry of the base. The coordination geometry of hexa-coordinated complex was severely distorted from an ideal octahedron, due to the NO5 coordination environment from the mixed coordination of one Hmthp− and two H2mthp ligands. Both complexes formed one-dimensional chain networks by hydrogen-bond and N-H···π interactions. Single-molecule magnet behavior was observed for the tetrahedral complex under zero magnetic field. The relatively short Co···Co distances induced non-zero intermolecular magnetic coupling, which split the ground ±Ms levels to suppress quantum-tunneling of magnetization. In the octahedral complex, by contrast, the distance was not short enough to induce the coupling. As a consequence, single-molecule magnetic behavior was observed for the octahedral complex only in the presence of an external static field.