Influence of Humidity on Layer-by-Layer Growth and Structure in Coordination Networks.

Metal-organic frameworks (MOFs) are promising materials because of their high designability of pores and functionalities. Especially, MOF thin films and their properties have been investigated toward applications in nanodevices. Typically, MOF thin films are fabricated by using a bottom-up method such as layer-by-layer (LbL) growth in air. Because the water molecules can coordinate and be replaced with organic linkers during synthesis, humidity conditions will be expected to influence the LbL growth processes. In this study, we fabricated MOF thin films composed of Zn2+, tetrakis-(4-carboxyphenyl)-porphyrin (TCPP), and 4,4'-bipyridyl (bpy) at 10 and 40% relative humidity (RH) conditions. Then, we investigated the humidity effects on chemical compositions of TCPP and bpy, periodic structure, orientation, and surface morphology. At high RH, coordination replacement of water with the organic linkers becomes more competitive than that at low RH, resulting in a different TCPP/bpy composition ratio between the two RH conditions. Also, more frequent coordination replacements of water with the organic linkers at high RH led to the formation of phases other than that observed at low RH, loss of growth orientation, and rough surface. The findings clarified the importance of controlling the RH condition during LbL growth to obtain the desired coordination networks.

Cycle Threshold (Ct) Values of SARS-CoV-2 Detected with the GeneXpert® System and a Mutation Associated with Different Target Gene Failure.

SARS-CoV-2 nucleic acid detection tests enable rapid virus detection; however, it is challenging to identify genotypes to comprehend the local epidemiology and infection routes in real-time qRT-PCR. At the end of June 2022, our hospital experienced an in-hospital cluster of COVID-19. When examined using the GeneXpert® System, the cycle threshold (Ct) value of the N2 region of the nucleocapsid gene of SARS-CoV-2 was approximately 10 cycles higher than that of the envelope gene. Sanger sequencing revealed a G29179T mutation in the primer and probe binding sites. A review of past test results revealed differences in Ct values in 21 of 345 SARS-CoV-2-positive patients, of which 17 cases were cluster-related and 4 were not. Including these 21 cases, 36 cases in total were selected for whole-genome sequencing (WGS). The viral genomes in the cluster-related cases were identified as BA.2.10, and those in the non-cluster cases were closely related and classified as being downstream of BA.2.10 and other lineages. Although WGS can provide comprehensive information, its use is limited in various laboratory settings. A measurement platform reporting and comparing Ct values of different target genes can improve test accuracy, enhance our understanding of infection spread, and be applied to the quality control of reagents.

Cell-growth phase-dependent promoter replacement approach for improved poly(lactate-co-3-hydroxybutyrate) production in Escherichia coli.

Escherichia coli is a useful platform for producing valuable materials through the implementation of synthetic gene(s) derived from other organisms. The production of lactate (LA)-based polyester poly[LA-co-3-hydroxybutyrate (3HB)] was carried out in E. coli using a set of five other species-derived genes: Pseudomonas sp. 61-3-derived phaC1STQK (for polymerization), Cupriavidus necator-derived phaAB (for 3HB-CoA generation), and Megasphaera elsdenii-derived pct (for LA-CoA generation) cloned into pTV118NpctphaC1ps(ST/QK)AB. Here, we aimed to optimize the expression level and timing of these genes to improve the production of P(LA-co-3HB) and to manipulate the LA fraction by replacing the promoters with various promoters in E. coli. Evaluation of the effects of 21 promoter replacement plasmids revealed that the phaC1STQK-AB operon is critical for the stationary phase for P(LA-co-3HB) production. Interestingly, the effects of the promoters depended on the composition of the medium. In glucose-supplemented LB medium, the dps promoter replacement plasmid resulted in the greatest effect, increasing the accumulation to 8.8 g/L and an LA fraction of 14.1 mol% of P(LA-co-3HB), compared to 2.7 g/L and 8.1 mol% with the original plasmid. In xylose-supplemented LB medium, the yliH promoter replacement plasmid resulted in the greatest effect, with production of 5.6 g/L and an LA fraction of 40.2 mol% compared to 3.6 g/L and 22.6 mol% with the original plasmid. These results suggest that the selection of an appropriate promoter for expression of the phaC1STQK-AB operon could improve the production and LA fraction of P(LA-co-3HB). Here, we propose that the selection of cell-growth phase-dependent promoters is a versatile biotechnological strategy for effective intracellular production of polymeric materials such as P(LA-co-3HB), in combination with the selection of sugar-based carbon sources.

Accumulation of Sulfonic Acid Groups Anchored in Covalent Organic Frameworks as an Intrinsic Proton-Conducting Electrolyte.

Covalent organic frameworks (COFs) are a novel class of crystalline porous polymers, which possess high porosity, excellent stability, and regular nanochannels. 2D COFs provide a 1D nanochannel to form the proton transport channels. The abovementioned features afford a powerful potential platform for designing materials as proton transportation carriers. Herein, the authors incorporate sulfonic acid groups on the pore walls as proton sources for enhancing proton transport conductivity in the 1D channel. Interestingly, the sulfonic acid COFs (S-COFs) electrolytes being binder free exhibit excellent proton conductivity of ≈1.5 × 10-2 S cm-1 at 25 ℃ and 95% relative humidity (RH), which rank the excellent performance in standard proton-conducting electrolytes. The S-COFs electrolytes keep the high proton conduction over the 24 h. The activation energy is estimated to be as low as 0.17 eV, which is much lower than most reported COFs. This research opens a new window to evolve great potential of structural design for COFs as the high proton-conducting electrolytes.

Cooperative phenomenon of vapochromism and proton conduction of luminescent Pt(ii) complexes for the visualisation of proton conductivity.

The luminescent and proton conductive Pt(ii) complex [PtCl(tpy-o-py)]Cl and its HCl adduct [PtCl(tpy-o-pyH)]Cl2 (o-Pt and o-Pt·HCl, respectively; tpy-o-py = 2,2':6',2''-terpyridine-6',2'''-pyridine) were synthesised and their crystal structures, vapochromic behaviour, and proton conduction, were investigated and compared to those of the para isomers [PtCl(tpy-p-py)]Cl and [PtCl(tpy-p-pyH)]Cl2 (p-Pt and p-Pt·HCl, respectively; tpy-p-py = 2,2':6',2''-terpyridine-4',4'''-pyridine). X-ray structure analysis revealed that the intermolecular metallophilic (PtPt) interaction was negligible in o-Pt but effective in o-Pt·HCl. Reversible transformation between o-Pt and o-Pt·HCl coupled with significant colour and luminescence changes was achieved by four different external stimuli, namely: exposure of o-Pt to humid HCl gas to form o-Pt·HCl, heating, exposure to MeOH vapour, and finally drying in air to regenerate the original o-Pt. The intraligand π-π* orange emission observed for o-Pt exhibited negligible dependence on the relative humidity (RH). Conversely, o-Pt·HCl exhibited red metal-metal-to-ligand charge-transfer (MMLCT) phosphorescence at 725 nm, originating from effective intermolecular Pt-Pt interactions, and interesting vapochromic behaviour that was dependent on the RH. Notably, o-Pt·HCl presented higher conductivity than the p-Pt·HCl isomer at RH < 80%. This trend was reversed at RH values > 80%, probably owing to the second water-adsorption-induced transformation of p-Pt·HCl. The cooperative phenomenon between the proton conduction and vapochromic behaviour observed for both o-Pt·HCl and p-Pt·HCl should allow the visualisation of the proton-conducting pathway, without the need for a bulk electrode, via the absorption and emission colours at both macroscopic and microscopic levels.

Editing Light Emission with Stable Crystalline Covalent Organic Frameworks via Wall Surface Perturbation.

The ordered π skeletons of covalent organic frameworks make them viable light-emitting materials but their limited tunability has precluded further implementation. Here we report the synthesis of hydrazone-linked frameworks which are stable in water, acid, and base, and demonstrate their utility as a platform for light emission. The polygonal backbone is designed to be luminescent and partially π conjugated while the pore wall is docked with single atom or unit to induce resonance, hyperconjugation, and tautomerization effects. These effects can be transmitted to the backbone, so that the framework can emit three primary colors of light. The wall can be perturbated with multiple surface sites, rendering the material able to edit diverse emission colors in a predesignable and digital way. The systems show high activity, stability, tunability, and sensibility: a set of features attractive for light-emitting and sensing applications.

Cross-correlated humidity-dependent structural evolution of Nafion thin films confined on a platinum substrate.

Nanometer thin films of Nafion ionomer interfaced with platinum form the functional electrodes in many electrochemical devices including fuel cells and electrolyzers. To impart facile proton conduction in a Nafion ionomer, sufficient hydration of the Nafion ionomer is necessary to create a percolating network of water-filled nanometer-sized hydrophilic domains that manifest as macroscopic swelling. This hydration behavior of the ionomer thin films is poorly understood especially for films confined on electrochemically relevant Pt substrates. In this work, we present the evolution of hydration-dependent microscopic hydrophilic domains and macroscopic expansion of a 55 nm thin Nafion film on a Pt substrate. The cross-correlation among the film macro-expansion from ellipsometry, the micro-expansion from GISAXS, and the water distribution from neutron reflectometry (NR) explains the observed non-affine behavior of the film which can be attributed to the randomly and spatially non-uniform distribution of water domains. A correlation between the macroscopic factor (ε/τ) for protonic conductivity, and the domain size and swelling is presented for the first time. In addition, interfacial water between Pt and the ionomer interface is estimated at 75% and 84% RH, and an increase in domain size with RH is discussed to explain the increased activity and oxygen diffusivity with RH.

Progress on highly proton-conductive polymer thin films with organized structure and molecularly oriented structure.

Several current topics are introduced in this review, with particular attention to highly proton-conductive polymer thin films with organized structure and molecularly oriented structure. Organized structure and molecularly oriented structure are anticipated as more promising approaches than conventional less-molecular-ordered structure to elucidate mechanisms of high proton conduction and control proton conduction. This review introduces related polymer materials and molecular design using lyotropic liquid crystals and hydrogen bond networks for high proton conduction. It also outlines the use of substrate surfaces and external fields, such as pressure and centrifugal force, for organizing structures and molecularly oriented structures.

Two-Step Vapochromic Luminescence of Proton-Conductive Coordination Polymers Composed of Ru(II)-Metalloligands and Lanthanide Cations.

Two proton-conductive and phosphorescent porous coordination polymers, La3-[H5.5RuP]2 and Pr3-[H5.5RuP]2 (H12RuP = [Ru(H4dpbpy)3]2+, H4dpbpy = 2,2'-bipyridine-4,4'-bis(phosphonic acid), composed of Ru(bpy)3-type metalloligands (bpy = 2,2'-bipyridine) functionalized with six phosphonate groups and lanthanide cations (Ln3+ = La3+ or Pr3+) were successfully synthesized. X-ray diffraction studies revealed that six to seven protons of the H12RuP metalloligand were removed in the coordination polymerization reaction to form the porous coordination framework (Ln3-[H5.5RuP]2) with Ln3+ cations (Ln3+ = La3+ or Pr3+). Although their porous structures collapsed on the removal of water molecules from the porous channels, the original porous structures were reconstructed by water adsorption. Interestingly, the triplet metal-to-ligand charge-transfer (3MLCT) emission of Ln3-[H5.5RuP]2 was blue-shifted on increasing the relative humidity (RH) in the low RH region, whereas the inverse red shift was observed in the high RH region, resulting in the highest-energy 3MLCT emission at medium RH. The origin of this two-step vapochromic luminescence (that is, the blue and red shifts of the 3MLCT emission) is ascribable to the water-adsorption-triggered reconstruction of the porous structure and the proton release from the H5.5RuP metalloligand to the water filled channels, respectively. The proton conductivity of Ln3-[H5.5RuP]2 is about 1000-times higher at 20% RH and 10-times higher at 95% RH than that of the carboxylate analog, La7-[RuC]4 (H6RuC = [Ru(H2dcbpy)3]2+; H2dcbpy = 2,2'-bipyridine-4,4'-bis(carboxylic acid)), probably because of the highly acidic phosphonic acid groups.

Light-Emitting Covalent Organic Frameworks: Fluorescence Improving via Pinpoint Surgery and Selective Switch-On Sensing of Anions.

Covalent organic frameworks (COFs) offer ordered π structures that are useful for developing light-emitting materials. However, most COFs are weak in luminescence. Here we report the conversion of less emissive COFs into light-emitting materials via a pinpoint surgery on the pore walls. Deprotonation of the N-H bond to form an anionic nitrogen species in the hydrazone linkage can eliminate the nitrogen-related fluorescence quenching pathway. The resulting COF enhances the fluorescence in a linear proportion to the progress of deprotonation, achieving a 3.8-fold improved emission. This pinpoint N-H cleavage on the pore walls can be driven only by the fluoride anion while other halogen anions, including chloride, bromide, and iodide, remain inactive, enabling the selective fluorescence switch-on sensing of the fluoride anion at a ppb level.

Proton-Conductivity Enhancement in Polymer Thin Films.

Highly proton conductive polymers have long attracted the attention of researchers for use in energy conversion, sensors, catalysts, and other applications. From the viewpoint of the scientific history of the creation of highly proton conductive polymers, one fundamental approach is based on the strategy of phase-segregated structures with strong acid groups. This Feature Article presents a new approach to enhancing the proton conductivity of the polymer thin films using an interface that can modify the degrees of freedom for a polymer structure through interaction between the substrate surface and polymers. I introduce suppressed proton conductivity into Nafion thin films and then specifically examine the enhancement in proton conductivity by the molecular orientation of the polymers. As the last topic, a highly proton conductive organized polyimide thin film is demonstrated using the lyotropic liquid-crystal property. Both molecular ordering and the in-plane oriented structure can enhance proton conductivity. Moreover, the optical domain and degree of molecular ordering derived from the molecular weight can contribute strongly to the proton transport property.

Multilayer Growth of Porphyrin-Based Polyurea Thin Film Using Solution-Based Molecular Layer Deposition Technique.

Controllable synthesis of organic thin film materials on solid surfaces is a challenging issue in the research field of surface science, as it is affected by several physical parameters. In this work, we demonstrated a solution-based molecular layer deposition (MLD) approach to prepare porphyrin-based covalent organic molecular networks on a 3-aminopropyl trimethoxysilane (APTMS) modified substrate surface using the urea coupling reaction between 1,4-phenylene diisocyanate (1,4-PDI) and 5,10,15,20-tetrakis-(4-aminophenyl) porphyrin (H2TAPP) at room temperature (22 ± 2 °C). Multilayer growth was investigated under different relative humidity (RH) conditions of the reaction chamber. Sequential molecular growth at low relative humidity (≤10% RH) was observed using UV-vis absorption spectroscopy and atomic force microscopy (AFM). The high-RH condition shows limited film growth. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) revealed the polyurea bond formation in sequential multilayer thin films, demonstrating that stepwise multilayer film growth was achieved using the urea coupling reaction.

Development of Ion-Conductive and Vapoluminescent Porous Coordination Polymers Composed of Ruthenium(II) Metalloligand.

We synthesized two new porous coordination polymers (PCPs) {Ln7(OH)5[Ru(dcbpy)3]4·4nH2O} (Ln7-Ru4; Ln = Ce, Nd) composed of the luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)3]4- ([4Ru]; 4,4'-dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide ions Ln3+ (Ln = Ce, Nd). These two PCPs Ln7-Ru4 are isomorphous with the previously reported PCP La7-Ru4, and the lattice constants (a, c, and unit cell volume V) changed systematically according to the lanthanide contraction. All three Ln7-Ru4 compounds have OH- anion containing porous structures and a large number of hydrate water molecules within the pores, resulting in moderate ion conductivities (10-6-10-7 S cm-1) at 90% relative humidity (RH) and 298 K. In contrast, the structural transformation of Ln7-Ru4 associated with water-vapor adsorption/desorption strongly depends on the lanthanide ion; the Ln7-Ru4 compounds with larger Ln3+ ions recover the original porous structure at lower relative humidities (RH). A similar trend was observed for the ion conduction activation energy, suggesting that the bridging Ln3+ ion plays an important role in the formation of the ion-conductive pathways. La7-Ru4 and Ce7-Ru4 exhibit vapochromic luminescence associated with water vapor adsorption/desorption, arising from the 3MLCT emission of [4Ru]. This vapochromic behavior is also affected by the replacement of the Ln3+ ion; the vapochromic shift of Ce7-Ru4 was observed at RH values (near 100% RH) higher than that of La7-Ru4. 3MLCT emissions of the [4Ru] metalloligand in Nd7-Ru4 were barely observable in the visible region, but sharp emission bands characteristic of 4f-4f transitions of the Nd3+ ion were observed in the near-infrared (NIR) region (arising from the 1MLCT transition of [4Ru]), suggesting the transfer of energy from the [4Ru] 3MLCT excited state to the 4f-4f transition state of the Nd3+ ions.

Interfacial Structure and Proton Conductivity of Nafion at the Pt-Deposited Surface.

Understanding the Nafion-Pt interface structure is important because fuel cell reactions occur at the three-phase boundary. Infrared (IR) p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) technique was used to investigate the in-plane (IP) and out-of-plane (OP) spectra in the identical substrate. Our previous study revealed that the proton conductivity of the Nafion thin films decreased at the MgO and SiO2 surfaces. We proposed that the origin for the lower proton conductivity can be derived from the highly oriented structure at the interface. However, the interface structure of the Nafion-Pt interface remains unclear. In this study, Nafion thin films were prepared by spin-coating on a Pt-deposited MgO substrates. The IP spectrum exhibited a well-known spectrum, but the OP spectrum was quite differed considerably from the IP spectrum. Furthermore, thickness dependence of the degree of orientation for this OP band was observed at the Nafion-Pt interface. This OP band can be assigned as the vibration mode of the mixture of the CF2 and sulfonic acid groups. At the low-RH region, proton conductivity of the Nafion thin film on the Pt-deposited surface was 1 order of magnitude higher than that on the SiO2 surface. Furthermore, the activation energy was 0.4-0.5 eV, which is lower than that of the SiO2 surface. These results, which suggest that the Pt surface influenced the proton transport property of Nafion thin film, can contribute to understand the relationship between the proton transport property and thin film structure on the Pt-deposited surface at the three-phase boundary for fuel cells.

Metal-Organic Coordination Network Thin Film by Surface-Induced Assembly.

The growth of metal-organic coordination network thin films on surfaces has been pursued extensively and intensively to manipulate the molecular arrangement. For this study, the oriented multilayer thin films based on porphyrinic nanoarchitecture were synthesized toward metal-organic coordination networks using surface-induced assembly (SIA). Nanoscale molecular thin films were prepared at room temperature using cobalt(II) ion and porphyrin building blocks as precursors. Stepwise growth with a highly uniform layer was characterized using UV-vis, AFM, IR, and XPS studies. The grazing incidence small-angle X-ray scattering and X-ray reflectivity results remarkably suggested a periodic structure in in-plane direction with constant and high mass density (ca. 1.5 g/cm(3)) throughout the multilayer formation. We propose that orientation of the porphyrin macrocycle plane with a hexagonal packed model by single anchoring mode was tilted approximately 60° with respect to the surface substrate. It is noteworthy that the well-organized structure of porphyrin-based macrocyclic framework on the amine-terminated surface substrate can be achieved efficiently using a simple SIA approach under mild synthetic conditions. The synthesized thin film provides a different structure from that obtained using bulk synthesis. This result suggests that the SIA technique can control not only the film thickness but also the structural arrangement on the surface. This report of our research provides insight into the ordered porphyrin-based metal-organic coordination network thin films, which opens up opportunities for exploration of unique thin film materials for diverse applications.

Fabrication and Characterization of Cross-Linked Organic Thin Films with Nonlinear Mass Densities.

The preparation of urea (bonded) cross-linked multilayer thin films by sequential deposition of bifunctional and tetrafunctional molecular building blocks is demonstrated. Multilayer growth as a function of deposition cycles was inspected using UV-vis absorption spectroscopy. From infrared results, three characteristic infrared bands of amide I, amide II, and asymmetric νa(N-C-N) stretching confirmed the formation of polyurea networks by alternate dipping into solutions of amine and isocyanate functionality monomers. The deconvoluted component of the C 1s and N 1s spectra obtained by X-ray photoelectron spectroscopy shows clear evidence of stable polyurea networks. The enhancement of structural periodicity with film growth was demonstrated by grazing-incidence small-angle X-ray scattering measurements. The thin film near the substrate surface seems to have an amorphous structure. However, molecular ordering improves in the surface normal direction of the substrate with a certain number of deposited layers. Constant mass density was not observed with deposition cycles. The mass density increased up to 16% within deposited layers from proximate layers to those extending away from the substrate surface. This difference in the packing density might derive from the different degrees of cross-linking among layers proximate to the substrate surface and extending away from the substrate surface.

Proton Conductivities of Lamellae-Forming Bioinspired Block Copolymer Thin Films Containing Silver Nanoparticles.

Size-controlled metal nanoparticles (NPs) were spontaneously formed when the amphiphilic diblock copolymers consisting of poly(vinyl catechol) and polystyrene (PVCa-b-PSt) were used as reductants and templates for NPs. In the present study, the proton conductivity of well-aligned lamellae structured PVCa-b-PSt films with Ag NPs was evaluated. We found that the proton conductivity of PVCa-b-PSt film was increased 10-fold by the addition of Ag NPs into the proton conduction channels filled with catechol moieties. In addition, the effect of humidity and the origin of proton conductivity enhancement was investigated.

Modification for Uniform Surface of Nafion Ultrathin Film Deposited by Inkjet Printing.

A lack of knowledge about the features of Nafion confined to ultrathin films at the interface has motivated additional examinations to promote the performance of polymer electrolyte membrane fuel cells (PEMFCs). In this work, we demonstrated the utilization of practical film-forming technique inkjet printing to fabricate a Nafion ultrathin film less than 10 nm thickness. However, the well-known "coffee-ring" effect caused poor quality of the printed pattern, which has restricted its application. This report describes a systematic investigation of necessary parameters such as ink concentration, substrate type, pitch, and offset for printing processes. Furthermore, post-treatment in an ethanol vapor atmosphere exhibited a significant effect on flattening and homogenizing the film surface morphology. Results show that the well-distributed Nafion ultrathin film modified by ethanol vapor annealing manifested much-improved proton conductivity.

Visualization of Ion Conductivity: Vapochromic Luminescence of an Ion-Conductive Ruthenium(II) Metalloligand-Based Porous Coordination Polymer.

We synthesized a new porous coordination polymer {La1.75(OH)1.25[Ru(dcbpy)3]· 16H2O} (La7-[4Ru]4; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) composed of a luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)3](4-) and La(3+) cations. X-ray analysis for La7-[4Ru]4 revealed that the La(3+) cations and [4Ru] metalloligands are crystallized in a molar ratio of 7:4 with OH(-) counteranions and a void fraction of ∼ 25.5%. Interestingly, La7-[4Ru]4 shows a reversible structural transition triggered by water ad/desorption, which affects not only the triplet metal-to-ligand charge-transfer ((3)MLCT) emission energy but also the ion conductivity in the solid state. This correlation suggests that La7-[4Ru]4 is an interesting material that enables visualization of the ion conductivity via the (3)MLCT emission energy.

Anomalous enhancement of proton conductivity for water molecular clusters stabilized in interstitial spaces of porous molecular crystals.

In an investigation into the proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials, we have found that water-stable nanoporous crystals are formed by complementary hydrogen bonding between [Co(III) (H2 bim)3 ](3+) (H2 bim: 2,2'-biimidazole) and TATC(3-) (1,3,5- tricarboxyl-2,4,6-triazinate); the O atoms in the -COO(-) groups of TATC(3-) in the porous outer wall are strongly hydrogen bonded with H2 O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2 O molecules as a novel C2 -type WMC, which are hydrogen bonded with four-, three-, and two-coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two-coordinated H2 O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre-melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10(-5) S cm(-1) at 300 K with an activation energy of 0.30 eV) through a proton-hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10(-5) S cm(-1) at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b-axis. The proton-transfer route can be predicted in WMCs, as O(4) of an H2 O molecule at the center of an SCTC shows a motion that rotates the dipole in the b-axis direction, but not the c-axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X-ray crystallography reflect a structural fluctuation along the b-axis direction induced by [Co(III) (H2 bim)3 ](3+) .