Goro Maruta

Metal–organic frameworks of manganese(II) 4,4′-biphenyldicarboxylates: crystal structures, hydrogen adsorption, and magnetism properties

Reactions of 4,4′-biphenyldicarboxylic acid (H2bpdc) with manganese(II) nitrate under solvothermal conditions yield two types of new metal–organic frameworks, [Mn4(bpdc)4(DMF)3](DMF) (1) (DMF = N,N′-dimethylformamide) and Mn3(bpdc)3(DMA)4 (2) (DMA = N,N′-dimethylacetamide). Structural analysis shows different solvents lead to distinct phases of manganese(II) 4,4′-biphenyldicarboxylate although the same starting materials are employed. Complex 1 features a microporous noninterpenetrated structure with nano-sized channels and a rare cem topological net, while 2 is non-porous with an α-polonium topology. Microporous 1 exhibits significant hydrogen adsorptive capability. Magnetic behaviors of the both complexes suggest the presence of antiferromagnetic interactions.

Metal–organic coordination architectures with 3-pyridin-3-yl-benzoate: crystal structures, fluorescent emission and magnetic properties

Reactions of 3-pyridin-3-yl-benzoic acid (HL) with metal nitrates under hydrothermal conditions yield seven new coordination polymers: Ni(L)2(H2O)2 (1), [Ni(L)2](H2O) (2), Co(L)2(H2O)2 (3), [Zn(L)2](H2O) (4), Cu(L)2 (5), Cd(L)2 (6) and Gd2(L)6(H2O)4 (7). A systematic investigation on coordination chemistry of the ligand and the significant function of supramolecular interactions in managing the resultant crystalline networks has been carried out. On the basis of the X-ray diffraction analysis of these complexes, the results show that complexes 1–5 and 7 form similar one-dimensional (1D) double-chain coordination arrays, among which 1 and 3, as well as 2 and 4, are isostructural. Remarkably, distinct network architectures are further constructed with the aid of weak secondary interactions. Amongst them, complexes 1, 3 and 5 exhibit the classical α-polonium networks, while complexes 2 and 4 present the (3,4)-connected two-dimensional layers. In 7, the intermolecular π–π stacking interactions lead to the formation of a double-strand structure. The CdII complex 6 assembles into a three-dimensional metal–organic framework exhibiting a unique 6-connected roa topology. The trans-configuration of L ligand is only found in the case of 6, whereas the cis-ligands are generally observed in these complexes. The fluorescent emission properties of 4 and 6 as well as the magnetic property of 7 have also been investigated.

Molecular Rotors of Coronene in Charge-Transfer Solids

Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA-type alternating π column, TCNQ also afforded a 3:1 complex, in which a face-to-face dimer of parallel coronenes (Cor-As) is sandwiched between TCNQs to construct a DDA-type alternating π column flanked by another coronene (Cor-B). Whereas solid-state (2)H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in-plane 6-fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)2] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA-type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor-As in the [Ni(mnt)2] complex arrange in a non-parallel fashion must cause the fast in-plane rotation of Cor-A relative to that of Cor-B. This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor-As shows inter-column interactions with neighboring Cor-As. The solid-state (1)H NMR signal of the [Ni(mnt)2] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in-plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable-temperature spin-lattice relaxation time (T1) experiments, are significantly lower than that of pristine coronene. The investigated structure-property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid-state rotor system that involves unsynchronized plural rotators.

Assembling an alkyl rotor to access abrupt and reversible crystalline deformation of a cobalt(II) complex

Harnessing molecular motion to reversibly control macroscopic properties, such as shape and size, is a fascinating and challenging subject in materials science. Here we design a crystalline cobalt(II) complex with an n-butyl group on its ligands, which exhibits a reversible crystal deformation at a structural phase transition temperature. In the low-temperature phase, the molecular motion of the n-butyl group freezes. On heating, the n-butyl group rotates ca. 100° around the C–C bond resulting in 6–7% expansion of the crystal size along the molecular packing direction. Importantly, crystal deformation is repeatedly observed without breaking the single-crystal state even though the shape change is considerable. Detailed structural analysis allows us to elucidate the underlying mechanism of this deformation. This work may mark a step towards converting the alkyl rotation to the macroscopic deformation in crystalline solids.

Spin density distributions of p-N-alkylpyridinium nitronyl nitroxides studied by solid-state high-resolution NMR

Abstract The electron spin density distributions of p - N -alkylpyridinium α-nitronyl nitroxides with alkyl=methyl ( p -MPYNN) and n -butyl ( p -BPYNN) were determined in their iodide salts from the temperature dependence of the solid-state high-resolution 1 H MAS NMR spectra. The results were compared with that of p -pyridyl α-nitronyl nitroxide ( p -PYNN) to see how positive charge on the aromatic ring affects the spin density distribution. This effect was not significant contrary to the effect of incorporation of a nitrogen atom into the aromatic group. The change in the magnitude of the spin density can be ascribed to the dihedral angle between nitroxide and aromatic moieties. Relatively large hyperfine coupling constant of N -methyl proton, which is almost half as large as those of β-methyl proton, implies the utility of the N -methyl group as an intermolecular magnetic coupler.

Theoretical Study of Effective Exchange Integrals for Ferromagnetic Phenylenevinylene Polymers with Nitroxddes. Possibilities of Organic Ferro-or Ferri-Magnetic Solids

Abstract Molecular orbital calculations were carried out for pendant-type ferromagnetic phenylenevinylene pligomers with nitroxide groups in order to elucidate variations of the effective exchange integrals with oligomer size, conformational change and spin defects generated in the dehydrogenation process of NOH groups in the precursor oligomers. It was shown that the ferromagnetic effective exchange interactions between the nearest neighbor nitroxides are about 50–80 cm−1, but they decrease with the internal rotation and spin defect. The interchain interactions between the oligomers are antiferromagnetic, and therefore they should be controlled by introduction of spacer group, showing a possibility to obtain the high Tc organic ferrimagnet induced by one-electron transfer between the oligomer and spacer.

Theoretical Calculation of Effective Exchange Integrals for One-and Two-Dimensional Poly(Phenylenemethylene) Systems. Possibilities of Organic Ferro-and Ferri-Magnetic Solids

Abstract Ab initio post UHF, DFT, CASSCF and semiempirical INDO calculations were carried out for one-and two-dimensional poly(phenylenmethylene) in order to elucidate variations of the effective exchange integrals with molecular connectivity, cluster size and hole (electron) doping. It was shown that the ferromagnetic effective exchange integrals by UCCSD(T) and DFT/4–31G are about 400 cm−1 for m-phenylene bis(methylene). The nigh-spin ground states of hole-doped polycarbenes were also studied, indicating a possibility of obtaining the high Tc organic ferrimagnets induced by the one electron transfer between polycarbene and spacer (electron donor or acceptor).

Hyperfine coupling of the cyanide ions and crystal water molecules of three dimensional magnetic polycyanides as studied by solid-state 13C- and 2H NMR

Abstract The hyperfine coupling constant (HFCC) of a CN ligand must be sensitive to its coordination bond and local magnetic structures in three dimensional magnetic polycyanide such as Prussian-blue analogs. The local magnetic structure of Rb0.90Mn1.05[Fe(13CN)6]·3H2O, which exhibits a thermally induced spin phase transition near room temperature with a wide hysteresis, was investigated in the high and low spin phase by solid-state 13C NMR spectrum of the 13CN ligand. Major and minor peaks were observed in the high spin phase FeIII(S=1/2) 13CN MnII(S=5/2), while the major and two other peaks were observed in the low spin phase. These results indicate a slightly non-uniform structure of Rb0.90Mn1.05[Fe(13CN)6]·3H2O. The HFCC of a carbon atom was estimated from the slope of the 13C NMR shift as a function of inverse temperature. The HFCC of the Fe 13CN Mn of Rb0.90Mn1.05[Fe(13CN)6]·3H2O is positive in both spin phases, while that of the FeIII(S=1/2) 13CN of (Na0.4K0.6)3[FeIII(S=1/2)(13CN)6] is negative. This result indicates that the effect of the spin of Mn ion exceeds the negative contribution of Fe ion in the Fe CN Mn system. On the other hand, the HFCC is negative for Na0.5Co1.26[Fe(13CN)6]·nH2O in the high spin phase, where the spin of FeIII(S=1/2) ion dominates the HFCC in the FeIII(S=1/2) CN CoII(S=3/2) system. The positive and negative contributions from MnII(S=5/2) and CrIII(S=3/2), respectively, dominate the 13C NMR shift in different temperature regions in the CrIII(S=3/2) 13CN MnII(S=5/2) system of MnII1.5[CrIII(13CN)6]·nH2O.

Local Magnetic Structure of Layered Compounds Cu2(OD)3X with Exchangeable Acid Anion X Studied by Solid State High Resolution Deuterium NMR

Abstract The microscopic magnetic local structure of Botallackite-type layer structured compounds Cu2(OD)3X (X = NO3 − and HCOO−) exhibiting a nonequilateral planar triangular magnetic lattice was determined by the solid-state high resolution deuterium NMR of deuterated hydroxy groups in the high temperature region above 190 K. The magnetic interactions in a copper ion layer were probed by the paramagnetic NMR shifts of the two chemically distinct hydroxy groups. Isotropic NMR shift of each hydroxy group showed different temperature dependence, suggesting non-uniform magnetic interaction. The magnetic interaction in the copper layer could be decomposed into a sum of 1D-Heisenberg ferro- and antiferromagnetic chains in the high temperature region. Two distinct copper chains with ferro- and antiferromagnetic exchange interactions J= ± 19 ± 11 and − 21 ± 3 K were found for x = NO3− from the temperature dependence of the two distinct NMR signals, while J = ± 13 ± 7 and − 13 ± 5 K for x = HCOO−. The derived va...

Muon spin relaxation study of magnetism of a triangular lattice BaVS3

We performed muon spin relaxation (µSR) experiments on a \(S =\frac{1}{2}\) triangular lattice system, BaVS 3 . Fast muon spin relaxation was observed below T X ≃30 K, indicating magnetic ordering....