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Ultramicropore-enriched single-wall carbon nanotube (SWCNT) sheet was prepared by a filtration process after acid treatment using HNO3/H2SO4 solution. Field emission scanning electron microscopic observation showed that a highly dense entangled structure of SWCNT bundles was formed by acid treatment. The pore structure of the SWCNT sheet was evaluated from adsorption isotherms of N-2 at 77 K and CO2 at 273 K. The SWCNT sheet gave remarkably developed uniform ultramicroporosity and reduced mesoporosity through formation of the highly packed sheet. The acid treatment remarkably increased the adsorption amount of supercritical hydrogen at 77 K by about three times. The enhancement of hydrogen adsorption by acid treatment came mainly from the increase in the ultramicropores because the increase in isosteric heat of hydrogen adsorption by acid treatment was only 0.1-0.2 kJ mol(-1).

Adsorption from toluene solution of phenanthrene and tetracene on single wall carbon nanotubes (SWCNT) is measured. Comparison of adsorbents such as laser ablation and HipCO samples reveals multiple factors influencing the adsorption mechanism. Acid functionalized carbon nanotubes have shown markedly increased adsorbability for the polyaromatic molecules. The linear tetracene molecule's adsorption is more promoted on nanotubes with increasing diameter, but also additionally with presence of the carboxylic groups. The adsorption mechanisms on carboxylic sites and on the bold, non-functionalized lame-diameter nanotubes are suggested and supported by detailed characterization of the SWCNTs applied. (c) 2007 Published by Elsevier Inc.

The synthesis, structural changes, and nitrogen gas sorption isotherm of a porous metal-organic framework (PMOF) comprising stacked two-dimensional sheets are reported. This compound easily loses guest molecules and shrinks its interlayer distance. The guest-free species show a unique double-step sorption isotherm. Sorption and X-ray structural analyses have clarified that the first uptake is a micropore filling, while the second uptake originates from a clathrate formation. This explains the total sorption amount corresponding to about the double of the original void volume of the crystals.

A controlled procedure leads to formation of pure anatase nanoparticles from titanium alkoxide near room temperature, without using any organic solvent by the peroxotitanic acid approach. The nanoparticles are highly mesoporous, with the surface covered by peroxo groups, and have excellent photode-composition activity as compared to those prepared from ordinary procedures.

Conductive and mesoporous single-wall carbon nanohorn/resorcinol-formaldehyde aerogel composites were fabricated by embedding organic resorcinol-formaldehyde aerogels with single-wall carbon nanohorns. Samples were characterized with transmission electron microscopy, field emission scanning electron microscopy, nitrogen adsorption at 77 K, and direct-current volume electrical conductivity measurement. It was demonstrated that these composites have important properties, such as controllable nanoporosity and high electrical conductivity in the range of 10(-4) S m(-1), which enables many potential applications.

The temperature and magnetic field dependences of magnetic characteristics of an organic radical (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL)) adsorbed on oxidized single-wall carbon nanohorn (ox-NH) were studied with a SQUID magnetometer and an electron spin resonance (ESR) spectrometer. TEMPOL molecules adsorbed on ox-NH do not form any ordered structures, but the formation of disordered clusters was suggested because of intensive restriction by nanoconfinement. Exchange interaction of TEMPOL adsorbed on ox-NH was weaker than that of bulk TEMPOL. Slow relaxation phenomena of magnetization and paramagnetic behaviors were observed by confinement of TEMPOL in nanospace.

Fluorinated activated carbon fibers (F-ACFs) were prepared by direct thermal fluorination of pristine activated carbon fibers. By the pyrolysis of F-ACFs at 1073 K under nitrogen gas flow, fluorine was subsequently eliminated and the sp(2)-bonded ACF structures were recovered. The micropore widths were 1.1 and 0.8 nm, and the isosteric heats of adsorption of nitrogen were 11.3 and 12.8 kJ/mol for pristine and defluorinated ACFs, respectively. These results strongly suggest that changes occurred in the structural properties of micro-pores in defluorinated ACFs. The hydrogen adsorption isotherms showed that the defluorinated ACFs adsorbed more hydrogen gas than pristine ACFs at 77 K, suggesting that the potential for interaction between hydrogen molecules and the defluorinated slit nanospaces was increased due to the changes in the pore structural properties and/or to the induced polarization of the pore walls making up the modified pi-electron systems. (c) 2007 Elsevier Ltd. All rights reserved.

Naphthalene was adsorbed on single wall carbon nanotubes (SWNT) from trichloroethylene solution. The adsorbed state of naphthalene on dry SWNT samples was studied with X-ray photoelectron spectroscopy and Raman spectroscopy. Adsorption of naphthalene molecules on SWNTs in trichloroethylene provide a uniform coating of external surface of individual SWNTs. Also, a technique of the liquid phase adsorption of naphthalene succeeded to control the assembly structure of the SWNTs, leading to an explicit adsorption hysteresis in the nitrogen adsorption isotherm at 77 K. (C) 2006 Elsevier B.V. All rights reserved.

The adsorption isotherms of supercritical hydrogen on [Cu-2(bz)(4)(pyz)](n) were measured at 77 K up to 10 MPa. The amount of supercritical hydrogen adsorbed on [Cu-2(bz)(4)(pyz)](n) at 77 K was 1.4 wt % at 10 MPa. The adsorption isotherms of supercritical hydrogen on [Cu-2(bz)(4)(pyz)](n) showed a stepwise adsorption that suggests clathrate formation between [Cu-2(bz)(4)(pyz)](n) and hydrogen molecules. The adsorption isotherms of supercritical hydrogen on [Cu-2(bz)(4)(pyz)](n) were measured at 77 K up to 10 MPa. The amount of supercritical hydrogen adsorbed on [Cu-2(bz)(4)(pyz)](n) at 77 K was 1.4 wt % at 10 MPa. The adsorption isotherms of supercritical hydrogen on [Cu-2(bz)(4)(pyz)](n) showed a stepwise adsorption that suggests clathrate formation between [Cu-2(bz)(4)(pyz)](n) and hydrogen molecules.

The structure of single-wall carbon nanohorn (SWNH) was analyzed with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The considerably strong peak due to single bonding carbons was observed in C1s XPS spectrum of SWNH. This peak intensity increases with oxidation treatment, coinciding with the decrease in Raman G/D intensity ratio. It is concluded that the presence of a considerable amount of single bonding carbons is the reason for the unique assembly structure accompanying with a strong D-band in Raman spectrum of SWNH.

The dispersion process of single-wall carbon nanotube (SWNT) by using sodium dodecylbenzene sulfortate (NaDDBS) was studied by means of surface tension measurements, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and transmission electron spectroscopy (TEM). The critical micelle concentration (CMC) and the concentration where the surface tension begins to drop increase by the presence of SWNT. The isotherm of NaDDBS amount adsorbed on SWNT shows the plateau region at 0.2-6 mM and the saturated region above 40 mM. The external surface of SWNT bundle is fully covered with adsorbed NaDDBS at the plateau region, showing that SWNTs can be dispersed with the bundle form. On the other hand, SWNTs are dispersed in individual tubes at the saturated region, where the adsorption amount corresponds to coating of individual tube surfaces with NaDDBS. This dispersion state was confirmed by SEM and TEM observations. The effect of the dispersion state of SWNTs on radial breathing mode in Raman spectrum gave inherent peak shifts, being the in situ evidences on the g step-wise dispersion mechanism of the SWNT bundle to the individual tubes. (c) 2006 Elsevier Inc. All rights reserved.

The radial breathing mode (RBM) frequency in Raman spectra of single-wall carbon nanotubes (SWNTs) is upshifted (3-9 cm(-1)) by immersion of the SWNTs in various alcohols and water. However, the immersion in the solvents does not cause any visible variation in the tangential mode frequency. The degree of this RBM frequency upshift induced by the solvent adsorption corresponds to that caused by applying a high pressure of 1 GPa (6-10 cm(-1)/GPa) in the literature. The degree of the RBM frequency upshift increases with increases in the molecular weight of the solvents. RBM frequency upshift caused by immersion of SWNTs in water is much larger than that by the molecular weight of alcohols, indicating the cluster formation of water molecules.

Liquid-phase adsorption of tetracene and phenanthrene on a single-walled carbon nanotube (SWCNT) was examined. Tetracene adsorption was more than six times greater than that of phenanthrene. X-ray photoelectron spectroscopic examination clearly showed that tetracene and phenanthrene molecules efficiently coated the SWCNT external surfaces. The remarkable difference between the adsorption amounts of tetracene and phenanthrene was caused by the nanoscale curvature effect of the tube surface, resulting in a difference in the amount of contact between the molecule and the tube surface. The adsorption of tetracene and phenanthrene caused a significant higher frequency shift in the radial breathing mode (RBM) of the Raman band of the SWCNT, indicating an intensive pi-pi interaction between these polycyclic aromatic hydrocarbons and the external SWCNT surface.

Novel nanostructured carbon material was synthesized by applying zeolite LTA as a template and using methanol as a carbon source. X-ray diffraction (XRD) revealed that the higher the decomposition temperature, the more graphitic and ordered the structure. The optimum pyrolytic temperature for addition of microporosity was below 1273 K by analysis of N-2 adsorption isotherm. The resultant carbons have the long-range periodic structure of a nanoscale curvature according to XRD and Raman spectroscopic examinations. The morphological similarity between zeolite LTA and synthesized carbon was evidenced by scanning electron microscopic observation. Grand canonical Monte Carlo simulation of N-2 adsorption isotherm indicates that synthesized nanoporous carbon has a hollow hemispherical structure of which diameter is less than 0.7 nm.

The supercritical N-2, O-2, and CH4 adsorption isotherms on a Cu-based metal-organic framework, [Cu(4,4'-bipyridine) (2)(BF4)(2)](n), over the temperature range of 196-303 K were measured by a gravimetric method. The N-2 and O-2 adsorption isotherms at 196 K showed a vertical adsorption accompanied by a rectangular hysteresis loop. A method of evaluating the absolute adsorption amount of these gases was developed taking into account the intermolecular interactions for the buoyancy-mediated method. The isotherms of the absolute adsorption amount were obviously different from the isotherms of the surface-excess mass adsorption at 196 K. We also obtained isotherms of the absolute adsorption amount of CH4 at different temperatures. The isosteric heat of adsorption from the isotherms of the absolute adsorption amount of CH4 is larger than the liquefaction heat of CH4 at its boiling point by more than 3 kJ mol(-1).

New nanoporous materials and fundamental concepts on molecule solid interaction are introduced. The nanopore structures of single wall carbon nanotube (SWCNT), single wall carbon nanohorn (SWCNH), double wall carbon nanotube (DWCNT), and highly flexible Cu-complex crystals as a representative of metal organic frameworks (MOFs) are explained. Adsorption properties of SWCNT, SWCNH, and DWCNT for supercritical CH4, and H-2, and Cu-complex crystals for supercritical CH4, are shown. DWCNT has a better adsorption potential for supercritical H-2, than SWCNT. The Cu-complex crystals form very quickly a new clathrate compound with CH4, molecules on adsorption of CH4, the reproducible clathrate formation is sensitive to temperature.

One-dimensional metal-organic compounds with cis, trans symmetry-controlled counter anions were synthesized (cis compound {[Cu(azpy)(H2O)(2)(OTs)(2)]center dot 2H(2)O center dot(acetone)} (1) and trans compound {[Cu(H2O)(4)Cu(azpy)(2)(OTs)(2)(H2O)(2)]center dot 2(OTs)center dot 2H(2)O center dot 2EtOH} (2)). Only 2, having trans conformation, exhibited a complete structure-restoration effect with a mechanism involving layering of molecular "bricks" of water and solvent molecules.

Crystal-to-crystal transformation from a 3D interpenetrated-type MOF {[Cu(BF4)(2)(bpy)(H2O)(2)](bpy)}(1) to a 2D square-grid-type [Cu(BF4)(2)-(bpy)2](2)(bpy=4,4'-bipyridine) was observed. It was derived from dehydration and confirmed by in situ FT-IR, TG, and elemental analysis. Moreover, we elucidate the novel expansion/shrinkage dynamic modulation of 2 triggered by clathrate formation with gas molecules.

A soft chemical method was used to insert silica bridging species between the layers of a graphite oxide precursor to form nanoporous graphitic composites (NPGC) and the effect of various synthetic conditions including colloidal dispersion, interlayer pre-expansion, and hydrolysis of silica source on the pore formation of NPGC was examined. It was found that an optimal alkali concentration for GO dispersion and surfactant concentration for pre-expansion exists for obtaining NPGC with very high porosity. Water content in surfactant-pre-expanded GO and the tetraethoxysilane hydrolyzing time and temperature influence the porosities of NPGC. The pore formation mechanism of NPGC is discussed based on these examinations, indicating the important roles of those conditions giving higher Si content and good composition state of carbon layers and silica in NPGC porosities. (c) 2006 Elsevier Ltd. All rights reserved.

Direct alpha-hydroxylation of ketones using molecular oxygen was accomplished by organic-inorganic hybrid polymers. A newly prepared Cu-piperazine hybrid polymer was tolerant to the basic conditions, and with employment of lithium hydroxide smoothly catalyzed the alpha-hydroxylation of ketones. In the present catalytic process not only tetralone derivatives, but also acyclic ketones were converted to the alpha-hydroxy ketones in good yield.

ZSM-5 zeolites with SiO2/Al2O3 molar ratio of 24 were treated in 0.05 M aqueous sodium hydroxide solution at 325 K in different periods. The samples were characterized by means of nitrogen adsorption at 77 K, field emission scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectroscopy. Analysis of the experimental results showed that the alkaline treatment periods have influence on the developments and structures of mesopores in the alkaline-treated ZSM-5 zeolites. Alkaline treatment initially develops mesopores mainly from the boundary portion of MFI zeolites to the bulk, while prolonged treatment destroys the mesopores, and an optimum mesoporosity is obtained by the treatment for 1.5 h. On the other hand, crystallinities and short-range order in alkaline treated zeolites have remained virtually unchanged according to the examination from X-ray diffractometry and Fourier transform infrared spectroscopy.

Predominant mesopores were added to pitch-based activated carbon fiber (0.7 nm of average pore width) by Ca(NO3)(2)-impregnated chemical activation. The influence of the concentration of calcium nitrate solution, reactivation temperature and reactivation time on the mesopore development of ACF were examined. The development of mesopores in the reactivated ACF was evidenced by an explicit hysteresis of N-2 adsorption isotherm at 77 K. The pore volume ratio of mesopores to micropores reached to 3-4. The addition of predominant mesopores to ACF enhanced the liquid phase adsorption rate of methylene blue by more than 10 times. (c) 2006 Elsevier Ltd. All rights reserved.

Phenanthrene was adsorbed from ethanol solution to the surface of single wall carbon nanotubes, which were previously physically and chemically characterized. Different anionic surfactants were added in the solutions to enhance the phenanthrene solubility and apparently have also improved the dispersion of two respective nanotube samples used. Adsorbed amount was determined through the concentration difference measured by UV-visible spectrophotometry. Results suggest that adsorption of phenanthrene is extremely improved in the case of nanotube purified with higher quality. These findings were confirmed by X-ray photoelectron spectroscopy. The influence of the surfactant on the adsorption kinetics of phenanthrene is suggested to be significant as well.

We present significant electrical conductivity responses of the pelletized as-prepared and oxidized (ox-) single-wall carbon nanohorns (SWNHs) on adsorption of CO2 and O-2. The morphological and pore structures of both pelletized SWNHs were examined by transmission electron microscopy (TEM) and nitrogen adsorption isotherm, leading to explicit evidences of the formation of nanoscale windows on the wall by oxidation. The SWNH and ox-SWNH induced a semiconducting behavior, strongly responded to CO2 and O-2 adsorptions, and each exhibited n-type- and p-type-like conductivities. The electrical conductivity increase and decrease for CO2 and O-2 adsorption, respectively, were observed for SWNH, whereas ox- SWNH showed a marked electrical conductivity drop on CO2 adsorption and almost no change on O-2 adsorption. The dramatically different electrical conductivity response of ox- SWNH is presumed to be ascribed to the annihilation of pentagons in the single graphene wall by oxidation.

Quantum sieving of activated carbon fibers (ACFs) and their fluorides was observed for H-2 and D-2 adsorption at 20 K. Fluorination reduced the slit-shaped pore width of ACFs by 0.2 nm. The activated carbon fibers can act as highly efficient quantum sieves for H-2 and D-2, because the effective size of an H2 molecule is larger than that of a D-2 molecule due to the uncertainty principle and the molecular size difference between H2 and D-2 is significant in the micropore space. The D-2/H-2 selectivity of ACFs evaluated by ideal adsorption solution theory was larger than that of the fluorinated ACFs.

Mesoporous activated carbon fibres (ACFs) were prepared from pitch-based microporous carbon fibres by additional chemical activation using calcium nitrate [Ca(NO3)(2)] and disodium hydrogen phosphate (Na2HPO4) as activation agents. The porosity change was examined by performing N-2 adsorption measurements at 77 K. The nitrogen adsorption isotherm varied as a result of re-activation with Na2HPO4 or Ca(NO3)(2) at 1123 K or 1173 K for I h or 2 h, with that of the re-activated ACFs exhibiting explicit H4 or H I hysteresis. The use of Ca(NO3)(2) for chemical activation produced more mesopores than Na2HPO4, the maximum mesopore volume being 0.92 ml/g. The largest volume ratio of mesopores to micropores was greater than three and the surface areas were greater than 1000 m(2)/g.

Accurate particle densities of the Cu-based metal organic framework [Cu(4,4'-bipyridine)(2)(BF4)(2)](n) for He, N-2 and CH4 molecules using the high-pressure buoyancy method have been determined. A smaller probe molecule gave a larger particle density (1.70 g/ml from He, 1.66 g/ml from N-2 1.60 g/ml from CH4). The effect of particle density on the evaluation of the surface excess mass for supercritical gas adsorption was examined; the above particle density difference gave rise to a 2-4% difference in the surface excess mass.

ZSM-5 zeolites having SiO2/Al2O3 molar ratios of 23.8 and 200 were treated in 0.05 M NaOH solutions at 325 K. The pore structure changes were investigated by low temperature nitrogen and argon adsorption. The mesopores with broad mesopore size distributions were developed after alkaline treatment of ZSM-5 with a low SiO2/Al2O3 molar ratio 23.8. Alkaline treatment of ZSM-5 with a high SiO2/Al2O3 molar ratio 200 gave no mesopores from both nitrogen and argon adsorption measurements. Formation of defect-cluster associated pores in ZSM-5 zeolite upon alkaline post-treatment is discussed.

The relationships between the enhanced interaction potential and intensive confinement effect of slit-shaped and cylindrical nanospaces are shown. The structures of water molecules and aqueous ions confined in nanospaces of activated carbon fiber (ACF) and single wall carbon nanohorn (SWNH)s were studied by adsorption, in situ small angle X-ray scattering(SAXS), GCMC simulation, and EXAFS spectroscopy. Water molecules are associated with each other to form the clusters, being stabilized in the carbon nanospaces. This stabilization mechanism of water in carbon nanospaces were evidenced by the interaction potential calculation, GCMC simulation, and the density fluctuation analysis of in situ SAXS. The Ornstein-Zernike analysis of in situ SAXS profiles lead to the conclusion that the critical size of water clusters for predominant water adsorption in hydrophobic carbon nanospaces is about 0.5 nm corresponding to the octomer to decamer. The adsorption hysteresis of water adsorption isotherm of nanoporous carbon was interpreted by the cluster growth, which is confirmed by the density fluctuation analysis. The Rb and Br ions confined in the carbon nanospaces were examined by EXAFS spectroscopy. The remarkable decreases in the hydration number and the water-Rb ion distance of the solution confined in the nanospaces were observed. In particular, the hydration number of the Rb ion in the nanospaces of SWNH is less than 3, being much smaller than the hydration number (6) of the bulk solution. The electrical double layer structure in the nanospaces should be quite different from that in the bulk solution. © 2005 Springer Science + Business Media, Inc.

The structure of RbBr aqueous solution confined in the interstitial nanospaces of single-wall carbon nanohorn (SWNH) assemblies was elucidated by using extended X-ray absorption fine structure (EXAFS) technique. The decrease of hydration number around a Rb ion is clearly observed. The EXAFS analysis indicates that the highly distorted and dehydrated structure around ions of aqueous solution confined in the nanospace (nanosolution: NSN) to form quasi one-dimensional structure in the interstitial nanospaces of SWNH assemblies. This unique hydration structures formed in nanospaces of SWNH is quite different from that not only of the bulk aqueous solution, but also confined in the slit-shaped nanospaces of activated carbon fiber (ACF).

The exact physical adsorption amounts of supercritical hydrogen on the single-wall carbon nanohorn (SWNH) assemblies were determined at 77, 196, and 303 K. There are two physical adsorption sites of interstitial and internal spaces on SWNH assemblies. The interaction potential depths of interstitial and internal spaces are -1000 and -600 K, respectively. However, both hydrogen densities in interstitial and internal spaces were about 70 g L-1 at 77 K at 5 MPa, though the hydrogen densities in interstitial and internal spaces were 15 and 10 g L-1 at 303 K and 6.5 MPa. The similar enhancement in the internal spaces was observed even at 196 K. The additional stabilization by the strong fluid-fluid interaction due to the cluster formation in the internal spaces. On the other hand, hydrogen molecules adsorbed in the interstitial spaces cannot form the stable cluster owing to the space limitation. The enthalpy of adsorption supports the presence of the stable cluster of hydrogen adsorbed in the internal spaces below 303 K.

HiPco single-walled carbon nanotubes (HPNTs) containing Fe were purified by a one-step process with HCl-washing (D-method) and a two-step process with HCl-washing after air oxidation (GD-method). The HPNT samples before and after purification were characterized using the N-2 adsorption at 77 K, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The TGA results showed a decreased Fe content after purification. In addition, the XPS results provided evidence that oxygen-based functional groups were introduced to the nanotube surface by both purification methods. The purification treatments also altered the N2 adsorption isotherms from type II to type IV; this accompanied the development of microporosity. Thus, purification considerably affects the surface chemistry and pore structures of HPNT aggregates. The effects of purification on the adsorption properties of HPNT aggregates with regard to CH3OH and C2H5OH vapors were examined at 303 K. The purification greatly enhanced the adsorptivity for CH3OH and C2H5OH vapors at 303 K under a low relative pressure. We associated this with the enhanced microporosity and the oxygen-based functional groups introduced on the surface.

NH, adsorptivity of hollandite manganese oxide (H-HolMO), which consists of a [2X2] tunnel structure of [MnO6] octahedral units, was examined using TG-DTA, isothermal adsorption, FT-IR, and TPD-MASS analyses. TG-DTA showed a gradual H2O evolution with increasing temperature in the temperature range of 373 to 573 K. The H2O/Mn mole ratios of the manganese oxide were 0.161, 0.082, and 0.035 for the sample pretreated in vacuo at 393, 473, and 573 K, respectively. N-2 adsorption isotherms of the samples at 77 K showed no micropores irrespective of the pretreatment temperature, indicating that N-2 molecules cannot be inserted into the tunnel of H-HolMO. An NH3 isotherm showed irreversible adsorption by chemisorption. The amount of NH3 chemisorbed correlated well with the H2O/Mn mole ratio. Also, XRD showed the expansion of the lattice by the NH, adsorption. These results indicate that NH3 molecules are inserted and bind to lattice protons in the tunnel structure. Since IR analysis showed a main band at 1402 cm(-1), the adsorbed species was found to be NH4+. Thus, a specific insertion of NH3 into H-HolMnO was shown; NH3 + H-HolMO --> (NH4)HolMO. TPD-MASS analysis showed that NH3 is not only inserted but also reacts with H-HolMO in a redox process generating nitrogen and water; 2NH(3), + 6MnO(2) --> 3Mn(2)O(3) + N(2)up arrow + 3H(2)O up arrow.

The magnetic properties of the divalent metal complexes [ML2(HL)] (M = CoII, NiII, and CuII HL = 2,3-diamino-1,4-diazabuta-1,3-diene-1,4-diol, i.e., diaminoglyoxime) with a slipped-stack structure were examined. The magnetic susceptibilities and the electron spin resonance spectra indicate that [CoL2(HL)] exhibits a ferromagnetic interaction along the stack chain, the strength of which is estimated to be 13.5 K, while [CuL2-(HL)] is paramagnetic and [NiL2(HL)] is diamagnetic. The magnetic behaviors of the [ML2(HL)] complexes can be predicted precisely by comparing the spin splittings of the partially occupied molecular orbitals of the monomer complexes ML2 and the dimer complexes 2ML2 which are equivalent in structure to the relevant moieties in the real stack chains, based on molecular calculations using the DV-Xα method. The modes of the differential spin densities for the dimers 2ML2 strongly suggest that the principal mechanism of superexchange on [CoL2(HL)] may operate through strong interaction of the 3dzx orbitals of Co atoms with the 2pz orbitals of two apical N atoms which form the πz-type systems of the adjacent complex molecules along the stack chain.