The host–guest composites of Hofmann‐type iron(II) spin‐transition (ST) porous coordination polymers incorporating guest molecules show guest‐dependent ST behavior in accordance with the respective ...guest species, which may be a gas, solvent, halogen, or organic molecule. The guest also works as a chemical stimulant to switch the spin state of the host between high and low spin at room temperature. In this review, we discuss guest properties including size, shape, flexibility, chemical properties, and pore loading content, which impact the spin states of the host framework and the ST behavior exhibited by the host–guest composites.
It all depends on the guests: The host–guest composites of Hofmann‐type iron(II) spin‐transition porous coordination polymers incorporating guest molecules show guest‐dependent spin‐transition behavior in accordance with the respective guest species (see scheme: G=guest, L=ligand).
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•Gas sensors using graphene oxide are summarized in this review.•Most studies on these sensors have been published in the last few years.•Graphene oxide has a large specific area and ...its characteristics change with adsorbed gases.•Oxygenous functional groups on graphene oxide interact with polar gas molecules.
This paper is a review of the recent progress on gas sensors using graphene oxide (GO). GO is not a new material but its unique features have recently been of interest for gas sensing applications, and not just as an intermediate for reduced graphene oxide (RGO). Graphene and RGO have been well known gas-sensing materials, but GO is also an attractive sensing material that has been well studied these last few years. The functional groups on GO nanosheets play important roles in adsorbing gas molecules, and the electric or optical properties of GO materials change with exposure to certain gases. Addition of metal nanoparticles and metal oxide nanocomposites is an effective way to make GO materials selective and sensitive to analyte gases. In this paper, several applications of GO based sensors are summarized for detection of water vapor, NO2, H2, NH3, H2S, and organic vapors. Also binding energies of gas molecules onto graphene and the oxygenous functional groups are summarized, and problems and possible solutions are discussed for the GO-based gas sensors.
A novel tetraoxolene‐bridged Fe two‐dimensional honeycomb layered compound, (NPr4)2Fe2(Cl2An)3 ⋅2 (acetone)⋅H2O (1), where Cl2Ann−=2,5‐dichloro‐3,6‐dihydroxy‐1,4‐benzoquinonate and ...NPr4+=tetrapropylammonium cation, has been synthesized. 1 revealed a thermally induced valence tautomeric transition at T1/2=236 K (cooling)/237 K (heating) between Fem+ (m=2 or 3) and Cl2Ann− (n=2 or 3) that induced valence modulations between FeIIHSFeIIIHS(Cl2An2−)2(Cl2An.3−)2− at T>T1/2 and FeIIIHSFeIIIHS(Cl2An2−)(Cl2An.3−)22− at T<T1/2. Even in a two‐dimensional network structure, the low‐temperature phase FeIIIHSFeIIIHS(Cl2An2−)(Cl2An.3−)22− valence set can be regarded as a magnetic chain‐knit network, where ferrimagnetic Δ and Λ chains of FeIIIHS(Cl2An.3−)∞ are alternately linked by the diamagnetic Cl2An2−. This results in a slow magnetization behavior attributed to the structure acting as a single‐chain magnet at lower temperatures.
Transfer news: A tetraoxolene‐bridged Fe layered compound has been shown to undergo a tautomeric transition from FeIIHSFeIIIHS(Cl2An2−)2(Cl2An.3−)2− at T>T1/2 to FeIIIHSFeIIIHS(Cl2An2−)(Cl2An.3−)22− at T<T1/2 (T1/2=236 K) by a thermally driven electron transfer between the Fe center and ligand. The compound can be regarded as a chain‐knit network that shows single‐chain magnet behavior in the low‐temperature state.
In this review article we discuss the unique and novel magnetic properties for the cobalt(II) compounds with a variety of terpy derivatives including substituents at the 4-position. These are also ...compared with the unsubstituted terpy cobalt(II) complex. Since the first SCO cobalt(II) complex with terpy ligand was reported, this system has been widely studied. SCO cobalt(II) complexes possessing terpy or OH-terpy ligand reveal incomplete or gradual SCO behavior. The pyterpy-appended cobalt(II) complex shows SCO depending on the guest molecules involved. Cobalt(II) complexes with long-alkylated terpy ligands, Co(C
n-terpy)
2(BF
4)
2 (
n
=
16, 14 and 12) have been synthesized and some were characterized by single crystal X-ray analysis. Furthermore, variable-temperature magnetic susceptibility indicated that the non-solvated compounds Co(C
n-terpy)
2(BF
4)
2 (
n
=
16, 14 and 12) exhibit “reverse spin transition” phenomenon with wide thermal hysteresis around room temperature. In addition, the solvated compound Co(C12-terpy)
2(BF
4)
2·EtOH·0.5H
2O shows “re-entrant SCO” behavior. The long alkyl chains in SCO cobalt(II) complexes can lead to novel physical properties resulting from a synergetic effect between SCO and response of the flexibility toward external stimuli.
Recently, “host–guest chemistry” aspects of material science have received much attention, particularly in relation to moderating the functions of materials. In particular, magnetic properties ...involving the “magnetic ordering” and “spin crossover” of host–guest metal complex systems have been actively investigated in terms of their host–guest chemistry. That is, systems in which the magnetic properties are sensitive to perturbation by the uptake of guests (which thus act as chemical stimuli). Such guests (solvents, gases and organic molecules) very often influence the structures of both discrete metallosupramolecular assemblies as well as those of coordination polymers/metal‐organic frameworks (CPs/MOFs), providing a means for fine‐tuning their magnetic behavior, including the switching of their spin states. In this minireview, we report recent progress in the development and investigation of magnetic materials of both the CP and MOF categories as well as of discrete complexes whose properties are modulated by guests.
In this minireview, we discuss magnetic materials, characterized as being both “porous magnets” and “SCO complexes” in which the magnetic properties can be modulated by the presence or absence of guests residing in a metal complex's molecular framework. That is, the effect of guest molecules on both the structures and magnetic properties of the metal complex assemblies are discussed.
Elastic crystals are a novel class of materials for use in optoelectronics and solar cells. Although controlling mechanical flexibility is critical when developing functional soft crystals, the ...number of reported metal-coordination-complex-based elastic crystals is limited. When developing such crystals, the flexibility of the crystals may be tuned via ligand substitution of the central metals or by exchange of the central metal ions; however, this has not been demonstrated experimentally to date. Thus, we herein report the preparation of mechanically flexible compounds using a synthetic procedure based on metal coordination complexes. It was found that the packing structure was considerably affected by the crystallization solvent, and control over the packing process was critical in obtaining complex molecules with designed flexibilities and structures. Furthermore, we demonstrate new Pd and Pt complexes with the salophen ligand, which exhibit the second and third highest elastic strains (ε values) reported to date, respectively, and the highest and second highest ε values (ε = 11.95% for Pd; 10.65% for Pt), respectively, among metal coordination complexes. These effects can be attributed to the microscopic changes in bond distance between the metals and ligands. Our findings are expected to inspire the tuning and development of metal-complex-based flexible crystals.
Proton conductivities of layered solid electrolytes can be improved by minimizing strain along the conduction path. It is shown that the conductivities (σ) of multilayer graphene oxide (GO) films ...(assembled by the drop‐cast method) are larger than those of single‐layer GO (prepared by either the drop‐cast or the Langmuir‐Blodgett (LB) method). At 60 % relative humidity (RH), the σ value increases from 1×10−6 S cm−1 in single‐layer GO to 1×10−4 and 4×10−4 S cm−1 for 60 and 200 nm thick multilayer films, respectively. A sudden decrease in conductivity was observed for with ethylenediamine (EDA) modified GO (enGO), which is due to the blocking of epoxy groups. This experiment confirmed that the epoxide groups are the major contributor to the efficient proton transport. Because of a gradual improvement of the conduction path and an increase in the water content, σ values increase with the thickness of the multilayer films. The reported methods might be applicable to the optimization of the proton conductivity in other layered solid electrolytes.
High proton conductivities in multilayer graphene oxide (GO) at room temperature facilitate the use of GO as a solid electrolyte in various cells. The conductivities of multilayer GO films are larger than those of single‐layer films by several orders of magnitude, which implies that protons move more easily in the interlayers than on the surfaces.
Ferroelectric spin crossover (SCO) behavior is demonstrated to occur in the cobalt(II) complex, Co(FPh‐terpy)2(BPh4)2⋅3ac (1⋅3 ac; FPh‐terpy=4′‐((3‐fluorophenyl)ethynyl)‐2,2′:6′,2′′‐terpyridine) and ...is dependent on the degree of 180° flip–flop motion of the ligand's polar fluorophenyl ring. Single crystal X‐ray structures at several temperatures confirmed the flip–flop motion of fluorobenzene ring and also gave evidence for the SCO behavior with the latter behavior also confirmed by magnetic susceptibility measurements. The molecular motion of the fluorobenzene ring was also revealed using solid‐state 19F NMR spectroscopy. Thus the SCO behavior is accompanied by the flip–flop motion of the fluorobenzene ring, leading to destabilization of the low spin cobalt(II) state; with the magnitude of rotation able to be controlled by an electric field. This first example of spin‐state conversion being dependent on the molecular motion of a ligand‐appended fluorobenzene ring in a SCO cobalt(II) compound provides new insight for the design of a new category of molecule‐based magnetoelectric materials.
Inspired by molecular ferroelectrics induced by molecular rotors, multifunctional compound exhibiting both ferroelectricity and spin crossover behavior was constructed. The flip–flop motion of polarization unit results in the expression of ferroelectricity and spin crossover behavior.
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•Biliary tract cancers are clinically and genetically heterogeneous.•32 significantly mutated genes were identified, some negatively affecting prognosis.•A novel deletion of MUC17 at ...7q22.1 was detected.•Cell-of-origin predictions suggest hepatocyte-origin of hepatitis-related ICCs.•Deleterious germline mutations of cancer-predisposing genes were detected in 11% of patients with BTC.
Biliary tract cancers (BTCs) are clinically and pathologically heterogeneous and respond poorly to treatment. Genomic profiling can offer a clearer understanding of their carcinogenesis, classification and treatment strategy. We performed large-scale genome sequencing analyses on BTCs to investigate their somatic and germline driver events and characterize their genomic landscape.
We analyzed 412 BTC samples from Japanese and Italian populations, 107 by whole-exome sequencing (WES), 39 by whole-genome sequencing (WGS), and a further 266 samples by targeted sequencing. The subtypes were 136 intrahepatic cholangiocarcinomas (ICCs), 101 distal cholangiocarcinomas (DCCs), 109 peri-hilar type cholangiocarcinomas (PHCs), and 66 gallbladder or cystic duct cancers (GBCs/CDCs). We identified somatic alterations and searched for driver genes in BTCs, finding pathogenic germline variants of cancer-predisposing genes. We predicted cell-of-origin for BTCs by combining somatic mutation patterns and epigenetic features.
We identified 32 significantly and commonly mutated genes including TP53, KRAS, SMAD4, NF1, ARID1A, PBRM1, and ATR, some of which negatively affected patient prognosis. A novel deletion of MUC17 at 7q22.1 affected patient prognosis. Cell-of-origin predictions using WGS and epigenetic features suggest hepatocyte-origin of hepatitis-related ICCs. Deleterious germline mutations of cancer-predisposing genes such as BRCA1, BRCA2, RAD51D, MLH1, or MSH2 were detected in 11% (16/146) of BTC patients.
BTCs have distinct genetic features including somatic events and germline predisposition. These findings could be useful to establish treatment and diagnostic strategies for BTCs based on genetic information.
We here analyzed genomic features of 412 BTC samples from Japanese and Italian populations. A total of 32 significantly and commonly mutated genes were identified, some of which negatively affected patient prognosis, including a novel deletion of MUC17 at 7q22.1. Cell-of-origin predictions using WGS and epigenetic features suggest hepatocyte-origin of hepatitis-related ICCs. Deleterious germline mutations of cancer-predisposing genes were detected in 11% of patients with BTC. BTCs have distinct genetic features including somatic events and germline predisposition.
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