Hisashi Konaka

Synthesis, crystal structure and magnetic properties of novel Mn12 single-molecule magnets with thiophenecarboxylate, [Mn12O12(O2CC4H3S)16(H2O)4], and its tetraphenylphosphonium salt

Abstract The preparation and physical characterization are reported for novel Mn12 single-molecule magnets having thiophenecarboxylate bridges, [Mn12O12(O2CC4H3S)16(H2O)4] (1), and its PPh4 salt (2). The reaction of the excess amount of 2-thiophenecarboxylic acid (tpcH) and [Mn12O12(OAc)16(H2O)4] in CH2Cl2 gave black crystals of 1, which could be reduced by PPh4I to give 2. From the crystal structure analysis of 2, it is revealed that there are two five-coordinated Mn ions, one of which is assigned to a MnII ion being in the vicinity of the tetraphenylphosphonium cation. Both complexes exhibit out-of-phase a.c. magnetic susceptibility (χ″M) signals in the 5.0–6.5 K range at 997 Hz a.c. frequency, which indicate that they are single-molecule magnets. From Arrhenius plots of the frequency dependence of the temperature of the χ″M peaks, the effective energy barriers Ueff were estimated to be 69 and 57 K for high-temperature phases of 1 and 2, respectively, and 40 K for the low-temperature phase of 1. The reduced magnetization measurement and its analysis indicate that 2 has S=19/2 ground state with g=1.99 and D=−0.61 K.

Crystal structure and photo-induced property of two-dimensional silver(I) complex with 1,3,5-tris(benzylsulfanyl)benzene

Abstract The silver(I) complex [Ag2(3bsb)2(ClO4)2] (1) (3bsb; 1,3,5-tris(benzylsulfanyl)benzene) has been prepared and its molecular structure was determined by X-ray crystallography. In 1, the silver ion prefers a tetrahedral coordination geometry and produces a two-dimensional sheet structure containing dimeric units. Irradiation of this complex 1 with light changes its color from white to pink; heat or exposure to acetone vapor makes the irradiated sample revert back to white. However, only 3bsb has no characteristic like this photochromism.

Bowl–shaped Cu(I) metallamacrocyclic ethylene and carbonyl adducts as structural analogues of organic calixarenes

Three novel Cu(I) metallacalixarenes with C(2)H(4) and CO legs, in which an anion is accommodated in the inside cavity, were self-assembled by anion templation and have been structurally characterized.

Syntheses and structural studies on silver(I) coordination polymers with trans,trans-1,4-dipenyl-1,3-butadiene

For the purpose of investigation on the reactivity of silver(I) with multiphenyl diene and the effect of counteranions on silver(I) complexes, we selected several silver(I) salts to react with trans , trans -1,4-diphenyl-1,3-butadiene (dpbd). The treatment of AgClO 4 ·H 2 O with dpbd afforded a 1-D W-type chain silver(I) coordination polymer [Ag(dpbd)(ClO 4 )] ( 1 ) and while the reaction of AgCF 3 CO 2 with dpbd gave rise to a co-crystallization structure [Ag 3 (CF 3 CO 2 ) 3 ]·(dpbd) ( 2 ) in which silver(I) and trifluoroacetate form a 1-D supramolecular ladder chain. The measurements of electric conductivity show that polymer 1 exhibits semiconductive behavior and while polymer 2 is an insulator. The effect of counteranions and steric hindrance on the formation of these silver(I) complexes is also discussed.

Two-dimensional silver(I) coordination polymer with twisted naphthalene rings

Abstract The silver(I) complex of octakis(cyclohexylsulfanyl)-naphthalene (ochsn), [Ag4(ochsn)(CF3COO)4](CH2Cl2) (1), has been prepared and its molecular structure was determined by X-ray crystallography. In 1, the silver ion prefers a tetrahedral coordination geometry comprised of two S atoms from the ochsn molecules and the two O atoms from the counter anion then producing two-dimensional sheet structure. Interestingly, the naphthalene ring in the complex has large deviations from planarity and end-to-end twists on the order of 35°. In contrast, the central naphthalene ring of ochsn shows almost a planar structure in the solid state.

New refinement approach for crystal structure analysis of organic compounds

Crystal structure analysis from powder diffraction data has become, for a decade, an effective and powerful technique when the single crystalline state of a sample cannot be maintained due to hydration, dehydration, or phase transition as well as when single crystals are not obtained. One of the big reasons is that several one-stop software have widely been used, providing all the features required for the structure analysis. However, the last step of the analysis “refinement of crystal structures” is still challenging. In case of, in particular, powder samples of organic compounds and metal complexes, the crystal structures are usually refined by setting restraints to bond lengths and angles to keep the molecular structures from collapsing. However, good results will not sometimes be obtained without setting proper restraints: the molecular structure may collapse if the restraints are weak, or the observed pattern may not agree with the calculated pattern if the restraints are strong. The effect of restraint strength factor on crystal structures and calculated profiles varies with observed intensities, peak profiles, etc. Therefore, the restraint strength factor should be estimated for each analysis. We will report several analysis examples from organic powder samples and validate the way of estimating restraint strength factors by comparing each result with the corresponding single crystal structure.

(μ-2,11-Dithia­[3.3]paracyclo­phane-κ2S:S′)bis­[(6-carboxy­pyridine-2-carboxylato-κ2N,O6)silver(I)]: a mixed-ligand silver-based dinuclear compound

In the title complex, [Ag2(C7H4NO4)2(C16H16S2)], each Ag(I) atom is trigonally coordinated by one S atom of a 2,11-dithia[3.3]paracyclophane (dtpcp) ligand, and by one N and one O atom of a 6-carboxypyridine-2-carboxylate ligand. Dtpcp acts as a bidentate ligand, bridging two inversion-related AgI atoms to give a dinuclear silver(I) compound. The dinuclear moieties are interconnected via O-H...O hydrogen bonds to form a two-dimensional zigzag sheet. Two such sheets are interwoven via pi-pi interactions between pyridine rings, affording an interwoven bilayer network.