Haruo Naruke

Enantioselective resolutions and circular dichroism studies of lanthanide-containing Keggin-type [Ln(PW11O39)2](11-) polyoxometalates.

Enantiopure crystals of K(1.3)Na(3.2)H(6.5)[l-Pr(PW(11)O(39))(2)]·8.3l-proline·21.5H(2)O (1), K(1.3)Na(3.2)H(6.5)[d-Pr(PW(11)O(39))(2)]·8.3d-proline·17H(2)O (2), and K(1.3)Na(3.2)H(6.5)[l-Er(PW(11)O(39))(2)]·8.3l-proline·22.5H(2)O (3) were successfully obtained by using l- and d-proline (pro) as chiral auxiliary agents. In these crystals, l- and d-[Ln(PW(11)O(39))(2)](11-) anions are attached by two l- and d-pro molecules, respectively, through a O···N hydrogen-bonding interaction between the square-antiprismatic LnO(8) center and amino-N atoms. The l- and d-[Pr(PW(11)O(39))(2)](11-) anions in aqueous solutions exhibited a couple of mirror-imaged CD spectra due to (3)H(4/2)→(3)P(0,1,2) and (1)D(2) transitions in the stereogenic Pr(3+) center. Chirality inductions by l- and d-pro from a racemic solution of [Er(PW(11)O(39))(2)](11-) was demonstrated by means of CD spectroscopy.

X-Ray structural and photoluminescence spectroscopic investigation of the europium octamolybdate polymer Eu2(H2O)12[Mo8O27]·6H2O and intramolecular energy transfer in the crystalline lattice

Photoluminescence and intramolecular energy-transfer properties of Eu2(H2O)12[Mo8O27]·6H2O, 1 have been determined in connection with the crystal structure. The compound has been prepared by treating K2[MoO4] with Eu(NO3)3 in aqueous solution at pH 3.0 and isolated in a crystalline form with a belt structure. A single-crystal X-ray analysis [triclinic, space group P, a= 10.105(3), b= 12.006(5), c= 9.365(4)A, α= 122.59(3), β= 90.12(3), γ= 98.33(3)°, Z=1, Mo-Kα radiation, R= 0.063 for 4485 independent data with I > 3σ(I)] shows the cation to have the composition [Eu(H2O)6]3+. The latter is also bonded to one oxygen atom of each octahedron of an edge-sharing pair of MoO6 octahedra in the Mo8O27 anion, which is isostructural to the condensation polymer of the octamolybdate through one common oxygen atom. In addition, Eu3+ is linked by one oxygen atom belonging to the MoO6 octahedron in a neighbouring Mo7O27 unit, resulting in the formation of a tricapped trigonal-prismatic Eu(H2O)6O3 group (average Eu–O bond length 2.48 A). Luminescent transitions of both 5D0→7FJ and 5D1→7FJ for Eu3+ are observed upon photoexcitation of the O → Mo ligand-to-metal charge-transfer (l.m.c.t.) bands but the intramolecular energy transfer to the 5D1 level takes place predominantly from the O → Mo l.m.c.t. states at energies higher than 3.6 eV (ca. 5.8 × 10–19 J). The temperature dependence of the intramolecular energy transfer from the O → Mo l.m.c.t. states to Eu3+ indicates that the configuration of the Mo–O–Eu linkage (ca. 150°) allows hopping of a d1 electron to the EuO9 site due to thermally activated delocalization between MoO6 and EuO9 sites, which acts as a deactivation channel for the energy transfer from the O → Mo l.m.c.t. states to the emitting levels of Eu3+. Co-ordination of six aqua ligands leads to a low lifetime (0.17 ± 0.01ms) of the emitting state of 5D0 with a resultant decrease in the total quantum yields of the emission, arising from vibronic coupling of the 5D0 state with the vibrational states of high-frequency OH oscillators. The 7F1, 7F2, 7F3, 7F4, 5D1 and 5D2 crystal-field splittings for the C1 site of Eu3+ are estimated on the basis of the high-resolution emission and excitation spectra at 77 K. Vibronic lines belonging to the 7F0→5D2 and 7F1→6D1 transitions are observed in the excitation spectrum.

Intramolecular energy transfer in polyoxometaloeuropate lattices and their application to a.c. electroluminescence device

Abstract Crystal Structures of four polyoxometaloeuropates, Na 9 [EuW 10 O 36 ].32H 2 O (1), K 15 H 3 [Eu 3 (H 2 O) 3 (SbW 9 O 33 )(W 5 O 18 ) 3 ].25.5H 2 O(2), [NH 4 ] 12 H 2 [Eu 4 (H 2 O) 16 (MoO 4 )(Mo 7 O 24 ) 4 ].13H 2 O(3),and Eu 2 (H 2 O) 12 [Mo 8 O 27 ].6H 2 O (4) are investigated to understand the relaxation process of the oxygen-to-metal (O→M) charge-transfer excitation energy in the polyoxometalate lattice. The temperature dependence of the intramolecular energy transfer from the O→M LMCT states to Eu 3+ in the polyoxometaloeuropate lattices indicates that the M-O-M and Eu-O-M bond angles of about 150° allow the hopping of d 1 electron among MO 6 octahedra and to EuO 8 (or EuO 9 ) site to be the deactivation of the O→M LMCT state due to the deactivated recombination between the electron and hole in the lattice. Co-ordination of aqua ligands to Eu 3+ leads to a decrease in lifetime of the emitting state of 5 d 0 , due to the vibronic coupling of the 5 d 0 state with the vibrational states of high frequency OH oscillators. Dispersion-typed electroluminescence (EL) cell is constructed with a highly photoluminescent [EuW 10 O 36 ] 9− system. With a.c. excitation to the divice consisting of the doublet structure of emissive [EuW 10 O 36 ] 9− and insulating Mylar film layers, the [EuW 10 O 36 ] 9− layer exhibits EL which matches the photoluminescence spectrum of the solid. A multicolor display in combination with other polyoxometalolanthanoates is possible.

Photoluminescence of (NH4)12H2[Eu4(MoO4)(H2O)16(Mo7O24)4] · 13H2O

Photoluminescence properties of polyoxomolybdoeuropate solid (NH4)12H2[Eu4(MoO4)(H2O)16(Mo7O24)4]·13H2O are studied. Photoexcitation into the oxygen-to-metal charge transfer (OaMo LMCT) band of the Mo7O24 group in this complex leads to red emission due to faf transitions within Eu3+, as a result of an intramolecular energy transfer from the Mo7O24 group to the Eu atom. The quantum yield of the emission under the OaMo LMCT excitation is low compared to that of polyoxotungstoeuropates. Two quenching channels for the photoluminescence are proposed: the deactivation of the OaMo LMCT state within the Mo7O24 group and the coupling of the excited state (5D0) of Eu3+ with high frequency O-H vibrational states of aqua ligands.

Crystal structure of K18.5H1.5[Ce3(CO3)(SbW9O33)(W5O18)3]·14H2O

Crystal structure of the title compound, which was isolated from a neutral solution containing HCO3−, was determined by X-ray diffraction analysis. It crystallized in monoclinic (C2/m) with crystallographic parameters of a=28.979(5), b=18.379(4), c=19.461(3) A, β=100.21(1)°, Z=4, and V=10201(3) A3. The [Ce3(CO3)(SbW9O33)(W5O18)3]20− anion possesses a trinuclear [Ce3(CO3)]7+ core attached by one B-α type [SbW9O33]9− and three [W5O18]6− groups with C3v symmetry. The [Ce3(CO3)]7+ core has the carbonate group which links three Ce3+ cations. A groove is formed between adjacent [W5O18]6− groups in the anion, resulting in three grooves in the anion. Each groove contains two K+ cations contacting the O atoms of the [Ce3(CO3)]7+, [SbW9O33]9−, and three [W5O18]6− groups. Other K+ cations form O–K–O linkages among the anions in the lattice.

Structure of dialuminiohexalutetiopentakis(hexaniobate): comparison with europium and erbium analogues

Abstract The structure of Na6.5H19.5[{Lu3O(OH)3(H2O)3}2Al2(Nb6O19)5]·38H2O was determined by X-ray diffraction analysis and compared with isomorphous Eu- and Er-complexes to investigate the effect of the ionic radii of the lanthanide cations (Eu3+:1.066; Er3+:1.004; Lu3+:0.977 A, for eight-fold coordination) on the molecular structure. A central [{Lu3O(OH)3(H2O)3}2]8+ core in the [{Lu3O(OH)3(H2O)3}2Al2(Nb6O19)5]26− anion was attached by both three equatorial [Nb6O19]8− and two axial [Al(Nb6O19)]5− groups with approximate D3 point symmetry. The three Lu atoms in a [Lu3O(OH)3(H2O)3]4+ group, a half [{Lu3O(OH)3(H2O)3}2]8+ core, achieved eight-fold coordination with O atoms: one μ3-O, two OH−, one terminal H2O and four O atoms belonging to the equatorial [Nb6O19]8− groups. The mean Lu···Lu distance within each of the two Lu3 triads is 3.676(6) A, while that between the two different Lu3 triads is 4.69(5) A. The former distance is short compared with that of the Eu-complex (3.76(2) A) but somewhat long compared with that of the Er-complex (3.66(1) A). The latter distance is comparable to the corresponding distance (4.69(6) A) of the Eu-complex, and slightly long compared with that of the Er-complex (4.62(4) A). The small size of the Lu3+ cation was reflected by a contraction of the [{Lu3O(OH)3(H2O)3}2]8+ core. This effect represents a shift in the three equatorial [Nb6O19]8− groups toward the center of the complex by about 0.13 and 0.05 A, compared with Eu- and Er-complexes, respectively.

Crystallographic characterization of the polyoxotungstate [Eu3(H2O)3(SbW9O33)(W5O18)3]18– and energy transfer in its crystalline lattices

The potassium salt of the new mixed-polyoxotungstate anion [Eu3(H2O)3(SbW9O33)(W5O18)3]18–(1) has been prepared from WO3, Sb2O3, Eu(NO3)3·6H2O, and KOH in water and isolated in crystalline form as K15H3[Eu3(H2O)3(SbW9O33)(W5O18)3]·25.5 H2O. It crystallizes in the monoclinic space group C2/m, with a= 30.250(7), b= 18.568(5), c= 22.101 (6)A, β= 109.19(8)°, and Z= 4. A central Eu3(H2O)3 core is co-ordinated by a B-type α-SbW9O33 unit and three W5O18 units with tetrahedral conformation. Each Eu3+ in the core exhibits eight-co-ordination by oxygen atoms belonging to H2O, SbW9O33, and W5O18 units. The intramolecular energy transfer from the O→W charge-transfer levels for the polyoxotungstate crystalline lattices to the emitting 5D0 level of Eu3+ takes place efficiently at least over 6.9 A which is the largest distance between W and Eu atoms in the anion. A comparison of the lifetime and quantum yield of the emission among (1), [Eu(W5O18)2]9–, and [Eu(SiW11O39)2]13– indicates that the hopping of a d1 electron between WO6 octahedra is the predominant deactivation channel of the O→W charge-transfer levels, which reduces drastically the communication with the excited levels of Eu3+.

Crystal structure of neodymium(III)-diethylene glycol complex

Abstract The title complex was crystallized from a diethylene glycol (DEG) solution containing 0.2 M neodymium trichloride hexahydrate. The X-ray structural analysis of the complex showed that [Nd(DEG)3]3+ cation consists of a central neodymium atom coordinated with nine oxygen atoms from the three DEG ligands with the approximate tricapped-trigonal prismatic configuration. There was a slight difference in conformation among the three DEG chains: one DEG ligand exhibited a zig-zag chain, while the other two were approximately planar due to disordering of the zig-zag conformations. The unequivalence of the conformation among the DEG ligands could be explained by an asymmetric arrangement of Cl− anions surrounding the [Nd(DEG)3]3+ cation.

Decisive Interactions between the Heterocyclic Moiety and the Cluster Observed in Polyoxometalate-Surfactant Hybrid Crystals

Inorganic-organic hybrid crystals were successfully obtained as single crystals by using polyoxotungstate anion and cationic dodecylpyridazinium (C12pda) and dodecylpyridinium (C12py) surfactants. The decatungstate (W10) anion was used as the inorganic component, and the crystal structures were compared. In the crystal comprising C12pda (C12pda-W10), the heterocyclic moiety directly interacted with W10, which contributed to a build-up of the crystal structure. On the other hand, the crystal consisting of C12py (C12py-W10) had similar crystal packing and molecular arrangement to those in the W10 crystal hybridized with other pyridinium surfactants. These results indicate the significance of the heterocyclic moiety of the surfactant to construct hybrid crystals with polyoxometalate anions.

Compositional introduction of lithium ions into conductive polyoxovanadate–surfactant hybrid crystals

Polyoxovanadate–surfactant hybrid layered crystals were successfully synthesized as single crystals by employing a primary alkylammonium cation, octylammonium ([C8H17NH3]+, C8NH3). Two types of hybrid crystals with the formulae [C8H17NH3]6[V10O28]·2H2O (C8NH3–V10) and [C8H17NH3]4Li2[V10O28]·4C2H5OH·6H2O (C8NH3–Li–V10) were obtained by different synthetic procedures. Changing the synthetic conditions enabled the precise introduction of lithium cations into the polyoxovanadate–surfactant hybrid crystals according to compositional control. C8NH3–V10 contained a discrete [V10O28]6− anion, while C8NH3–Li–V10 was composed of a [V10O28]6− anion associated with two lithium cations formulated as {[Li(H2O)3]2[V10O28]}4−. The conductivities of C8NH3–V10 and C8NH3–Li–V10 were investigated under anhydrous conditions at intermediate temperatures.