Antiaromatic molecules are known for their intriguing physical properties and high reactivity, which arise from their unique electronic structures. While the properties of individual antiaromatic molecules have been extensively studied, research on their assembled structures is still in the early stages. In this work, we synthesized a hydrogen-bonded organic framework, named Nor-HOF, using a stable antiaromatic molecule, Ni(II) norcorrole, as a building block. Single-crystal X-ray structure analysis revealed that Nor-HOF possesses a one-dimensional columnar structure of infinitely stacked Ni(II) norcorroles with permanent porosity. Theoretical calculations indicated that the norcorroles in Nor-HOF interact through their molecular orbitals while retaining their antiaromaticity. Furthermore, we demonstrated that the oxidation of the norcorrole columns by adsorption of I2 into the pores enhances the electrical conductivity of Nor-HOF by approximately 1000-fold. This work opens a new perspective on exploiting the periodic structure of antiaromatic molecules for the development of advanced functional materials.

Quasi-one-dimensional halogen-bridged metal complexes (MX-chains) have structures in which metal ions, such as Pt, Pd, and Ni, are alternately linked with bridging halogen atoms. The distance between the metal ions and the halogen atoms is a reliable indicator for assessing their electronic states. In this study, we report a new Pt-I MX-chain with an anion possessing long alkyl chains, in which all hydrogen atoms are replaced by deuterium. We elucidated the effects of deuteration of the alkyl chains in the assembled anions on the chemical pressure effect. Deuteration of long alkyl chains in the anions resulted in a shortened Pt-I distance. Consequently, the cell volume was reduced by approximately 2.8%. Furthermore, improved crystallization during compound synthesis led to larger and more stable crystals.

Abstract The structural flexibility of metal–organic frameworks (MOFs) is influenced not only by composition and topology but also by particle aggregation states. Here we investigate the flexibility of MOF assemblies fabricated by a simple surfactant-assisted method without specialized equipment. The structural changes of [Cu(NMe2-ipa)] upon CO2 adsorption were suppressed in a regularly oriented monolayer assembly, whereas those in a randomly oriented multilayer assembly were similar to those of bulk powders, demonstrating that particle assembly is a practical technique for tuning MOF flexibility.

Mn-PCy3 showed the highest H 2 /D 2 separation ability among known materials due to a large difference in ZPVE. D 2 separation with pressure swing adsorption using Mn-PCy3 could be achieved with ∼1/10 of the energy cost for distillation.

Water adsorbents are essential in our daily lives and in various industrial fields. The water adsorption rate is one of the most important properties of water adsorbents and should be improved to implement high-throughput devices. In this study, we focused on enlarging the pore size of MIL-101(Cr) by defect engineering for a faster water diffusion. MIL-101(Cr) terephthalate linkers were substituted with formate to create the defects. We investigated how the formate substitution influenced the pore size of MIL-101(Cr) and its water adsorption rate. Thermogravimetric measurements and pore size distribution analysis confirm the defect formation. In the evaluation of the water adsorption rate, we confirm three distinct adsorption processes with different adsorption rates, corresponding to water adsorption on the pore surface, into middle pores, and into large pores, respectively. In particular, defects in MIL-101(Cr) obviously influence the third water adsorption process into large pores, in which the water adsorption rate increases by up to 25%. It is suggested that the defect formation promotes water diffusion through an available pathway and condensed water transfer from other pores by the enlargement of windows between pores. These results can help us develop dehumidification devices with higher throughput.

A two-dimensional Kagomé-type MOF (Azln-KGM) incorporating 1,3-azulenedicarboxylate ligands was synthesized. Compared with reported isomorphous MOFs featuring a benzene motif, Azln-KGM exhibited an enhanced maximum adsorption capacity and gate-opening behavior accompanied by larger structural changes.

Herein, we report a reusable UiO-67-Pd catalyst for additive-free transfer hydrogenation of epoxides at room temperature using ammonia borane as the hydrogen source. The protocol enables selective conversion of aromatic and aliphatic epoxides into the corresponding alcohols and can be readily applied to the reduction of other unsaturated functionalities, including α,β-unsaturated ketones, N-heterocycles, azoarenes, and nitroarenes. A series of mechanistic investigations were carried out to understand the catalytic process.

A new approach for hydrogen isotope separation using an unsaturated organometallic complex was proposed. Adsorption measurements of [Mn(dppe)2(CO)(N2)](BArF24) (Mn-dppe) (dppe = 1,2-bis(diphenylphosphino)ethane, BArF24 = B[C6H3(3,5-CF3)2]4) using H2 and D2 revealed a significant difference in the adsorption enthalpy of H2/D2 at much higher room temperatures than in previous studies, with D2 molecules being more strongly adsorbed on unsaturated metal sites. Mixed gas adsorption isotherms were calculated at each temperature using IAST, and it was predicted that D2 uptake was much larger than H2 uptake. Column chromatographic separation using the difference in adsorption enthalpy indicated that deuterium could be concentrated, and DFT calculations suggest that this difference in adsorption force is due to the difference in vibrational potentials involved in metal-dihydrogen bonding. This study introduces a new separation approach that could enable hydrogen isotope separation in the ambient temperature range.

To meet the growing demand for hydrogen isotopes, the development of efficient and practical methods for isotope separation for dihydrogen is essential to replace the current cryogenic distillation method operating at 20 K. One of the most promising alternatives is chemical affinity quantum sieving (CAQS), which exploits differences in adsorption enthalpy (|Delta Delta H degrees|) arising from variations in zero-point vibrational energy (ZPVE) between isotopologues. However, low |Delta Delta H degrees| values of materials have prevented effective separation under ambient conditions. In addition, designing materials with a high |Delta Delta H degrees| value is challenging. Herein, we report the largest |Delta Delta H degrees| value of 5.0 kJ mol-1 observed in the solid-state dihydrogen complex [Mn(PCy3)2(CO)3][BARF], exceeding that of all previously known materials. Quantum chemical calculations and statistical analyses were employed to elucidate the origin of this separation ability. Furthermore, we demonstrated H2/D2 separation at ambient temperature using gas chromatography. This work presents a novel strategy to enhance the efficiency of isotope separation, thereby enabling H2/D2 separation at room temperature.

Quadruple stacking topology with an unusual threefold stacking periodicity among four honeycomb sheets was realized in a flexible, wavy honeycomb-sheet MOF (PMC-20).

It is expected that single-molecule magnets (SMMs) containing Lanthanoids play an important role in high-density magnetic devices. In this work, we synthesized new conductive Ln(III) SMMs, (TMTSF)4[Ln(NCS)6](CH3CN)2(CH2Cl2)0.5 (H2O)0.5 (TMTSF = (tetramethyltetraselenafulvalene), Ln(III) = Dy (1) and Tb (2)), which have organic TMTSF pi donors as the conducting part. The crystal structure has high symmetry, and lanthanoid complexes form a lattice-like structure with the TMTSF donor. [Ln(NCS)6]3- forms a distorted octahedron due to SSe contact with the TMTSF. The compound undergoes fast magnetic relaxation in the low-temperature region, and its relaxation time tau is almost independent of the temperature. The change in rate is nearly linear. The compounds show semiconductive behavior and a weak magnetoresistance effect at ambient and high pressure at the low temperatures.

Through-space electrical conduction in paddlewheel-type homovalent dinuclear complexes remains poorly understood, despite the numerous reports on these complexes. Herein, the electrical conduction of new Ru2(II,II) complexes with 2-pyrenecarboxylate (pyrCOO-) ligands, [Ru2(pyrCOO)4X2] ⋅ n(X) (where X=DMF (Ru-DMF), NMP (Ru-NMP), DMA (Ru-DMA)), was investigated. The dimensionality of π-stacking interactions between discrete molecules in Ru-DMA is higher (two-dimensional) than in Ru-DMF and Ru-NMP (stair-like one-dimensional). Nevertheless, Ru-DMF, which contains a slight amount of organic radicals, exhibited the highest electrical conductivity. This suggests that the large overlap and high dimensionality of π-stacking interactions among the complexes, along with a slight organic radical impurity, contribute to the increased electrical conductivity.

The fabrication of heterostructures from low-dimensional materials is very challenging, particularly the creation of low-dimensional heterojunctions that can be characterized at an atomic resolution. In a previous work, a two-dimensional (2D) heterostructure made from halogen-bridged metal complexes (MX-Chains), [Ni(chxn)2Br]Br2 (chxn = 1R,2R-diaminocyclohexane) and [Pd(chxn)2Br]Br2, has been synthesized, and the nature of the electronically 1D heterojunction at an atomic resolution was revealed. In the work reported here, we have successfully fabricated double core-shell crystals (Ni-Pd-Ni) from these MX-Chains, using a stepwise electrochemical epitaxial method. Upon cleavage of the heterostructure along the van der Waals layers, a double heterojunction surface is observed. The MX-Chains are aligned in the heterostructure and exhibit anisotropic optical properties based on their 1D electronic systems, as measured using UV-vis-NIR polarized reflectance microscopy. Current-voltage curves at different temperatures are recorded using three probes attached to different areas of the heterostructure and reveal the presence of ohmic conduction through the double 1D heterojunctions. The ohmic contact between the two types of MX-Chains arises from the atomic-scale connection of the MX-Chains at the heterojunction. This work represents the first example of a molecule-based heterostructure that has electronic conductivity and demonstrates electrical conduction through a 1D heterojunction.

Understanding the structure–property relationships in electrically conductive metal–organic frameworks (MOFs) is critical for their rational design toward practical applications. Since single crystals of MOFs with through‐space conductive π‐stacked columnar structures are relatively easy to obtain, their structures can be determined with high accuracy. However, elucidating those structure–property relationships without interference from carrier scattering and variations in carrier concentration remains challenging. Herein, we synthesized three isostructural porous molecular conductors (denoted as PMC‐3 ) via electrocrystallization using a redox‐active N,N’ ‐di(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxdiimide (NDI‐py) ligand and ZnX 2 (X = Cl, Br, I). Single crystals of PMC‐3 exhibit high electrical conductivity (∼10 −3 S cm −1 ), comparable to the highest values reported for NDI‐based crystalline materials. Moreover, PMC‐3 serves as a model system for probing structure–property relationships in through‐space conductive MOFs, offering three key advantages. First, the absence of counterions, eliminating carrier scattering; second, identical carrier concentrations across the series, allowing isolation of the effects of π ‐stacking geometry on transport properties; and third, tunable π ‐stacking geometries via halide ligand substitution. As a result, a linear correlation between the lattice parameter along the stacking axis and intrinsic charge transport properties is revealed, representing a significant advance in understanding charge transport in through‐space conductive MOFs.

The structural flexibility of metal-organic frameworks (MOFs), which undergo structural changes upon gas adsorption, has been reported to depend on factors such as crystal structure, defects, and crystal size. On the other hand, MOFs are used as assemblies of crystals, such as pellets or membranes, but few studies have reported the effect on the flexibility in the assembly structure. In this study, we prepared assemblies of [Cu(NMe2-ipa)] (NMe2-KGM, NMe2-ipa = 5-dimethylamino isophthalate). NMe2-KGM with different packing densities and arrangements was used to compare the magnitude of structural changes during gas adsorption. It was found that structural changes of the MOFs in the regular assembly are suppressed compared to random assembly. The results of this study are expected to lead to new strategies for controlling flexibility through the design of crystal array structures.

This research focuses on enhancing H2 adsorption by using the [Mo(PCy3)2(CO)3] complex supported on porous materials such as silica gel and mesoporous carbon. The study reports a significant increase in hydrogen adsorption capacity, reaching up to 9.3 times that of the bulk complex. This improvement suggests that using mesoporous materials as supports for the [Mo(PCy3)2(CO)3] complex enhances the accessibility of H2 gas to its open-metal sites.

While metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been widely investigated as porous conductive materials, the research on the electrical properties of HOF materials has been limited. Moreover, the electrical conductivity of HOF materials is typically several orders of magnitude lower than that of MOFs and COFs. In this work, a HOF material based on naphthalene diimide is designed and achieved a remarkable electrical conductivity of 2.9 x 10-2 S cm-1 after hydrazine doping, which represents the highest value reported in the HOF system to date. In addition, this material exhibits a reversible change of its electrical conductivity under exposure to ammonia which is promising for gas-sensor applications. The demonstration reveals a new dimension of HOFs as conductive materials and opens up possibilities for new HOF-based devices. In recent years, porous materials have gained significant interest as functional materials. This study introduces a novel hydrogen-bonded organic framework (HOF) based on naphthalene diimide, which, following chemical reduction, exhibits the highest electrical conductivity reported among HOF systems to date. Additionally, this framework demonstrates electrical reversibility during repeated ammonia doping and de-doping cycles, suggesting its potential as a gas sensor. image

Dinitrogen complexes have garnered significant attention due to their potential applications across various fields. The synthesis and characterization of novel dinitrogen complexes are essential to advancing this area of research. In this study, we report the bulk synthesis and first successful single crystal X-ray structure analysis of [Cr(PCy3)2(CO)3(N2)] using high-pressure nitrogen at 50 atm. The presence of the nitrogen ligand was confirmed by infrared (IR) spectroscopy and elemental analysis, and the interesting disorder phenomenon between N2 and CO ligands was also observed. The elimination process of the N2 ligand was monitored by a combination of thermogravimetry (TG) and temperature-programmed desorption (TPD), and the changes in the color, IR spectrum, and UV-vis spectrum of the complexes before and after elimination were investigated. These experimental results agree well with the results of density functional theory (DFT) calculations.

Significant effort has been devoted to the development of materials that combine high electrical conductivity and permanent porosity. This paper discloses a diazaporphyrin-based hydrogen-bonded organic framework (HOF) with porosity and n-type semiconductivity. A 5,15-diazaporphyrin Ni(ii) complex with carboxyphenyl groups at the meso positions afforded a HOF due to hydrogen-bonding interactions between the carboxy groups and meso-nitrogen atoms. The thermal and chemical stabilities of the HOF were examined using powder X-ray diffraction analysis, and the charge-carrier mobility was determined to be 2.0 x 10-7 m2 V-1 s-1 using the flash-photolysis time-resolved microwave conductivity (FP-TRMC) method. An analogous diazaporphyrin, which does not form a HOF, exhibited mobility that was 20 times lower. The results presented herein highlight the crucial role of hydrogen-bonding networks in achieving conductive pathways that can tolerate thermal perturbation. A Ni(ii) diazaporphyrin with carboxy groups afforded a stable HOF through intermolecular hydrogen-bonding interactions, which exhibited high semiconductivity as well as stability toward heating and various solvents.