Spintronics is a key technology in 21^st century based on the freedoms of the charge, spin, as well as orbital of the electron. Usually in these systems, the bulk or classical magnets composed of the transition metals are used. However, according to Mooreʼs rule, the classical or bulk magnets have a limitation to minimize the magnets into nano-sizes. On the other hand, in our study we will use Single-Molecule Quantum Magnets (SMMs), which behave as nano-sized magnets and are considered as new magnets in this century. In this review, I will focus on the new quantum molecular spintronics by using SMMs as follows;1) Single-molecule memory by Kondo peaks, 2) Field effect transistor (FET), 3) Giant magnetoresistance (TMR, ~200 %), 4) Tunneling magnetoresistance (TMR) with double butterflies.

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In this review, properties and applications of metal-organic frameworks (MOFs) and porous coordination polymers (PCPs) are described. Many MOFs and PCPs are highly flexible and responsive to external stimuli. Sometimes they transform their structures to others by maintaining the single crystallinity. For decades, MOFs and PCPs have been regarded as a class of the promising materials for hydrogen storage and carbon dioxide capture applications since they adsorb large amounts of gases at low temperatures. However, their gas uptake capacities decrease dramatically at ambient temperature compared to those at low temperatures because they physic-sorb gases by weak interaction energies. Therefore, to enhance gas storage and separation abilities of MOFs and PCPs at ambient temperature, we have modified their pore spaces. In this review, some characteristic properties of MOFs and PCPs will be introduced, and various strategies for modifying the pore spaces of PCPs and MOFs for hydrogen storage and carbon dioxide capture will be presented.

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Nucleic acids can adopt many types of noncanonical structures such as a triple helix and a quadruplex depending on the sequence and solution conditions. Recently, we developed a molecular crowding system which is the cell mimicking system to investigate thermodynamic behaviors of nucleic acids in cell. As results of our researches, the molecular crowding stabilizes the quadruplex with Hoogsteen base pairs, while it destabilizes the duplex with Watson-Crick base pairs which is the canonical structure. In this review, based on the thermodynamic results of DNA and RNA under the crowding condition, regulation of transcription and translation by the quadruplex structure of nucleic acids and its stabilizers is described. It is possible that the polymerase and ribosome bound to the template DNA and RNA, respectively, may mimic the crowded conditions in which we have shown to stabilize the quadruplex. Our results presented in this review indicate that stable noncanonical structures regulate transcription and translation. The results further our understanding of the transcription and translation processes involving the noncanonical structures and may guide the design of transcription and translation regulating drugs.

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The clusters of biomolecules have an important role as recognition interface in living systems, where the weak molecular recognition of each biomolecular unit is efficiently enhanced by the dense assembly of the units to realize strong affinity. The mimic of these molecular designs has been explored, but the structural deviations or small number of clustered units are not satisfactory as the model of natural interfaces. In our recent projects, we synthesized biomolecular clusters by anchoring a biomolecular unit to an organic ligand followed by assembling the ligands with transition metal ions to obtain self-assembled spherical complexes. Owing to the self-assembly nature of the coordination complexes, the number of introduced biomolecular units is strictly defined, the molecular sizes are huge with the diameter of several to ten nanometers, and the synthesis is quite simple and quantitative. With the variety of sugar, DNA, or peptide clusters, we demonstrated that the huge clusters work as functional interfaces and realized the application to biomolecular or inorganic recognition and further extended to the template synthesis exploiting the recognition functions and the unique three-dimensional shape.

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In this review, we report a new reduction protocol for early transition metal complexes – a salt-free reduction. In this salt-free reduction process, electron-rich organosilicon compounds, such as 1,4-bis(trimethylsilyl)-2,5-cyclohexadiene (1a), 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (1b), 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1c), 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1d), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1e), and 1,1’-bis(trimethylsilyl)-1,1’-dihydro-4,4’-bipyridine (1f), serve as versatile reducing reagents for group 4—6 metal chloride complexes, where easily removable ClSiMe₃ and the corresponding aromatic compounds, e.g., benzene, toluene, pyrazine, and 4,4’-bipyridyl, are generated as the reduction byproducts. This reductant-derived metal waste-free system enables us to directly observe catalytic intermediates by spectroscopic methods due to the homogeneity of the reaction mixture. In addition, simplicity of removing the reduction byproducts by evacuation or washing allowed us to isolate low-valent metal complexes that could be applied for direct complexation to redox-active ligands. Furthermore, 1e, containing methyl substituents around the nitrogen atom of the reductant is applicable as a stoichiometric reductant for a low-valent titanocene-catalyzed Reformatsky reaction of aldehydes and alkyl 2-bromoalkanoates without forming any reductant-derived metal waste.

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Synthesis of methanol from methane and terminal alcohols from linear alkanes using molecular oxygen as an oxidant under mild conditions is an attractive and environmentally-friendly transformation reaction. Insertion of molecular oxygen into a transition metal-carbon (sp³) bond is a key step to achieve the transition metal complex-catalyzed transformation. In this review, two mechanistically-different insertion reactions of oxygen into palladium and platinum-carbon (sp³) bonds are introduced. The former insertion is proposed to proceed by a radical chain mechanism, which is similar to that for the auto oxidation of organic compounds. A palladium(III) 17e^- intermediate, [Pd^IIIMe₂(OOMe)(bipy)] (bipy = 2,2'-bipyridine), which would be formed by the attack of a methylperoxy radical to [PdMe₂(bipy)], is regarded as a characteristic species in the proposed mechanism. On the other hand, the latter insertion involves loosely aggregated Pd(II) or Pt(II) methyl complexes, [Me(L)M^II…M^II(L)Me] (L = 6,6''-diamino-2,2':6',2''-terpyridine), which would be excited to triplet complexes, ³[Me(L)M^III–M^III(L)Me]*, upon exposure to light. Subsequent coordination of triplet oxygen and further conversions including reductive elimination of a carbon (sp³)- oxygen bond at the final step afford [M^II(L)OOMe].

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