小澤 芳樹

Two polymorphs of mononuclear six-coordinate iron(II) spin-crossover complex trans-[Fe(tzpy)(2)(NCS)(2)] (tzpy=3-(2-pyridyl)[1,2,3]triazolo[1,5-a]pyridine) (1) were isolated and structurally characterized. According to the thermally dependent magnetic measurements, polymorph A undergoes a gradual spin transition from a paramagnetic high-spin state (T-5(2), S=2, HS-1) above 200K to a diamagnetic low-spin state ((1)A(1) S=0, LS-1) below 120 K, whereas polymorph B shows an abrupt spin transition with T-1/2 at 102 K. Molecular and crystal structures of polymorph A in the HS-1 and LS-1 states were studied at 300 and 40 K, respectively. Significant differences in Fe-N distances and coordination geometries of Fe were found between the two spin states, as expected. Light-induced excited spin state trapping (LIESST) was observed upon irradiating the crystal with 532 nm laser light at 40 K, whereupon a metastable high-spin state (HS-2) was formed; the molecular and crystal structure of this metastable state were investigated by a pump and probe method because of its relatively fast relaxation. The electronic configuration of the Fe center in the HS-1, LS-1, and LIESST (HS-2) states were further confirmed by Fe K- and L-edge absorption spectroscopy. In addition, the C N stretching frequency on the ligand can also be followed through the spin transition. The excitation and relaxation process concerning such metastable state were followed by the C N stretching frequency and magnetic susceptibility measurements in the temperature ranges 15-55 K and 5-80 K, respectively. The structure and electronic configuration of the LIESST state of polymorph A were firmly established by X-ray diffraction, X-ray absorption, infrared absorption, and magnetic measurements. A single-crystal-to-single-crystal transition through irradiation was demonstrated. The changes in structure and electronic configuration as a result of the spin transition are believed to occur concurrently.

Yoshiki OZAWA, Shin-ichi ADACHI, 2009, 'MS24', <i>Nihon Kessho Gakkaishi</i>, vol. 51, no. 1, pp. 56-58

In the crystalline state, the rhodium dinuclear complex [(RhCp*)(2)(mu-CH(2))(2)(mu-O(2)SSO(2))] (1) with a photoresponsive dithionite group (mu-O(2)SSO(2)) and two pentamethylcyclopentadienyl ligands (Cp* = eta(5)-C(5)Me(5)) undergoes a 100% reversible unimolecular type T inverse photochromism upon interconversion to [(RhCp*)(2)(mu-CH(2))(mu-O(2)SOSO)] (2). The photochromism can be followed directly by using stepwise crystal structure analysis (Angew. Chem., Int Ed. 2006, 45, 6473). In this study, we found that the photoreaction of 1 was triggered by absorption of the 510 nm light (charge transfer band from sigma(S-S) to sigma*(S-S) and e(Rh-Rh) orbitals assigned by DFT calculation) and included two important processes: kinetically controlled oxygen-atom transfer to produce four stereoisomers of 2 and thermodynamically controlled isomerization between the four stereoisomers of 2 to afford the most stable isomer. Although the formation rate of the four stereoisomer products was kinetically controlled and the population of the four stereoisomers produced in the system was thermodynamically controlled, both processes were regulated by the steric hindrance between the mu-O(2)SSO(2) or mu-O(2)SOSO ligand and the reaction cavity formed by the Cp* ligands. The cooperation of both processes achieved an intriguing stereospecific oxygen-atom rearrangement to produce only one stereoisomer of 2 at the final stage of the photoreaction at room temperature. We also determined the effect of the oxygen-atom rearrangement on the rotational motion of the two crystallographically independent Cp* ligands (parallel and perpendicular arrangement). Using variable-temperature (13)C CP/MAS NMR and quadrupolar echo solid-state (2)H NMR spectroscopies, before photoirradiation, the activation energies for the rotation of the parallel and perpendicular Cp* ligands in 1 were determined to be 33 +/- 3 and 7.8 +/- 1 kJ/mol, respectively, and after photoirradiation, in 2, they were much lower than those in 1 (21 +/- 2 and 4.7 +/- 0.5 kJ/mol, respectively). The large decrease in the activation energy for the parallel Cp* in 2 is attributed to the relaxation of molecular stress via a stereospecific oxygen-atom rearrangement, which suggests that the rotational motion of the Cp* ligands is coupled to the photochromism.

The first vanadotellurate, [HTeV9O28](4-), has been synthesized and structurally characterized. The V-51 and H-1 NMR revealed that the proton stays on the surface of the molecular oxide anion even in solution.[GRAPHICS](C) 2008 Elsevier B.V. All rights reserved.

The platinum dimer and heteropolynuclear platinum complexes of 3,5-dimethylpyrazolate, [Pt2M4(mu-Me(2)pz)(8)] [M = H (1), Ag (2), Cu (3)], were synthesized and structurally characterized. They exhibit yellow, sky-blue, and orange luminescence, respectively, in the solid state. The absorption bands of 2 and 3 are mainly assigned to the combination of the metal-metal-to-ligand charge-transfer and [Pt-2 -> Pt2M4] transitions by the time-dependent density functional theory (DFT) method. DFT calculations also indicate that the emissive states of 2 and 3 are (3)[Pt-2 -> Pt2Ag4] and (3)[Cu(d) -> Pt2Cu4], respectively.

The M alpha NP acid method has been applied to racemic aliphatic acetylene alcohols in order to simultaneously prepare enantiopure alcohols and to determine their absolute configurations by H-1 NMR anisotropy. Racemic acetylene alcohols 6 - 8, 11, and 20 were esterified with M alpha NP acid (S)-(+)-1 to yield diastereomeric MaNP esters which were efficiently separated by HPLC on silica gel with separation factors a in the range 1.60 - 1.93. The H-1 NMR anisotropy factors Delta delta [= delta(2nd fr.) - delta(1st fr.)] were calculated from the data of the first- (22a - 27a) and second-eluted M alpha NP esters (22b - 27b). The absolute configurations of the first-eluted esters were determined from the distribution of Delta delta values in the M alpha NP sector rule. In the case of M alpha NP ester 26b, the assigned absolute configuration was confirmed by X-ray crystallography. The solvolysis of M alpha NP esters yielded enantiopure acetylene alcohols 5 - 8 with established absolute configurations. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

A tetraethylammonium (TEA) salt of TeO42- was synthesized by reacting Te(OH)(6) with tetraethylammonium hydroxide. X-ray structural analysis of (TEA)(2)TeO4 center dot 2H(2)O confirmed that this new compound consists of discrete TeO42- anions of distorted tetrahedral structure together with TEA cations and water molecules of crystallization [a = 8.0820(9) angstrom, b = 13.7730(12) angstrom, c = 20.1590(18) angstrom, V=2244.0(4) angstrom(3), Z=4, and space group Pccb]. The Te-125 NMR spectrum indicated that water reacts with the TeO42- anion to regenerate octahedral tellurate species in solution.

The structure of tris(2,4-xylyl)phosphane (1) is reported and supramolecular assembly of gua(+) salt of tris(2,4-dimethyl-5-sulfonatophenyl)phosphane co-crystal with guanidine chloride (2) is analyzed in detail. Weaving hydrogen bond ribbons with polar and apolar stabilizing pillars as well as stacking interaction of phenyl rings resulting sixfold phenyl embraces interpenetrating with the polar networks were found. Both compounds are racemate, show propeller chirality and 2 crystallizes in non-centrosymmetric space group (C-3 symmetry) with the ortho-methyl groups outside of the molecular cone. According to the DFT calculations on the anion of 2, the high barrier of concerted ring rotation opens the possibility of resolving the enantiomers through hydrogen bonds to chiral donors. (c) 2006 Elsevier B.V. All rights reserved.

Icosaniobate [Nb20O54](8-) was synthesized by reacting [H4Nb6O19](4-) with NO in tetrahydrofuran or MeNO2. A single-crystal X-ray diffraction study of its n-tetrabutylammonium salt [a = 17.7284(18) angstrom, b = 33.542(3) angstrom, c = 34.316(2) angstrom, Z = 4, and space group P22(1)2(1)] revealed a dimeric structure where two decaniobate ions are condensed sharing two terminal O atoms. Unlike that in [(NbW5O18)(2)O](4-), the Nb-O-Nb bridges in icosaniobate are bent. The nonlinear bridging reduces the maximum possible symmetry of the dimeric anion to mm 2, which it closely approximates.

Masaki Maekawa, Yoshiki Ozawa, Atsushi Yagasaki, 2006, 'Icosaniobate:  A New Member of the Isoniobate Family', <i>Inorganic Chemistry</i>, vol. 45, no. 24, pp. 9608-9609

The six-dimensional (6D) low density elimination method (LDEM) has been applied to solve the p-type icosahedral Zn 75 Mg 16 Ho 9 quasicrystal. The reconstructed electron density distribution by the LDEM exhibits three large occupation domains (ODs) centred at (0,0,0,0,0,0), (1/2,1/2,1/2,1/2,1/2,1/2,) and (1/2,0,0,0,0,0) in the 6D primitive unit cell, and the OD at (1/2,1/2,1/2,1/2,1/2,1/2,) contains Ho atoms, which mainly distribute around the threefold directions. A geometrical analysis confirms that a rhombic triacontahedron cluster which includes a Bergman-type cluster is a basic building unit of the structure.

The first Pt molecular oxide that incorporates a hetero element has been synthesized by reacting [(Me3P)(2)Pt](NO3)(2) with Na2MoO4 and its two different conformers have been structurally characterized. (C) 2005 Elsevier B.V. All rights reserved.

The first single crystal structure of small natural raphides in an agave plant is completely determined using an intense X-ray originating from a synchrotron radiation. The SEM image shows that the tip of the crystal is approximately hundreds of nanometer in width sharply grow to stick to the tissue of herbivorous vermin. Furthermore, the crystal develops cracks that propagate at an inclination of approximately 45° towards the direction of crystal growth such that the crystal easily splits into small pieces in the tissue.

Redox reactions of dodecacarbonyltetrarhodium(0), Rh₄(CO)₁₂, with 9,10-phenanthraquinone derivatives gave novel one-dimensional rhodium(I)–semiquinonato complexes. Two typical linear chain structures with direct Rh–Rh contacts were determined by X-ray crystal structure analyses of the compounds.

We have characterized superstructures of thiacyanine J aggregates in aqueous electrolyte solution in the dye concentration range between 2.5 and 80 mM. Fluorescence microscopy, polarized-light microscopy, and atomic force microscopy proved that the individual thiacyanine J aggregate possessed a mesoscopic rectangular sheetlike morphology (similar to3-7 mum wide and similar to10-30 mum long) consisting of a two-dimensional monomolecular layer of molecules. Synchrotron small-angle X-ray scattering revealed the superstructure of oriented monomolecular sheets which shows a disordered (nematic-like) or an ordered (smectic) layer alignment in solution. These superstructural behaviors can be interpreted in terms of the packing or alignments of the mesoscopic monomolecular sheets of the J aggregate as a function of the dye concentration.

The crystal structures of [(PhCH2)(2)NH2](+)[m-C6H4(N-3)-(COO)](-) before and after UV-irradiation were analyzed at 25 K by using an X-ray vacuum camera set up at the synchrotron laboratory (SPring-8). The C-N (nitrene) bond distance in the triplet state of the photo-induced m-carboxyphenylnitrene is determined to be 1.34(4) Angstrom.

Molecular distortion of a photoexcited diplatinuin(II) complex in a single crystal has been directly observed by accurate synchrotron radiation diffraction studies. Photoexcited crystallographic analysis has revealed that a small portion of [Pt-2(pop)(4)](4-) (pop = H2O5P22-) Complex shows the Pt-Pt bond shrinkage of 0.23 Angstrom under blue laser irradiation.

In situ synchrotron radiation structure analyses of a light-induced radical pair from o-Cl-HABI were performed by using an X-ray vacuum camera at 23-70K at the BL02B1 station of SPring-8. The combined results of X-ray analysis with theoretical calculation, IR, and UV-vis spectroscopy reveal that a slight conformational change of the radical pair causes the drastic spin-multiplicity change during 2-140 K.

A novel tetranuclear mixed valence cationic Pt molecular oxide [RMe3P)(2)Pt)(3)Pt(OH)(6)](4+) is obtained by reacting H2Pt(OH)(6) and (Me3P)(2) Pt2+, whose NMR spectra suggest the existence of another species in solution that may serve as a starting point for further synthesis of Pt molecular oxides.

A new one-dimensional iodo-bridged mixed-valence diplatinum(II,III) complex (MMX chain compound) with dithiobutanoate (n-PrCS₂^-) as a ligand, Pt₂(n-PrCS₂)₄I, was found to undergo a structural phase-transition at 358–359 K by the differential scanning calorimetry (DSC) measurement and X-ray crystal structure analyses. In X-ray diffraction photographs measured using synchrotron radiation of the SPring-8 facility, the weak but distinct Bragg spots corresponding to the periodicity of 2-fold repetition length of a –Pt–Pt–I– unit were observed at 300 K and changed to diffuse scattering at 350 K. The electric conductivity deviates from the typical semiconducting behavior in the temperature region above 330 K.

A new one-dimensional (I-D) halogen-bridged mixed-valence diplatinum(II,III) compound, Pt-2(EtCS2)(4)I (3). has been successfully synthesized from [Pt-2(EtCS2)(4)] (1) and [Pt-2(EtCS2)(4)I-2] (2). These three compounds have been examined using UV-visible-near-IR, IR, polarized Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray crystal structure analyses (except for 1). Compound 3 was further characterized through electrical transport measurements, determination of the temperature dependence of lattice parameters, X-ray diffuse scattering, and SQUID magnetometry. 3 crystallizes in the monoclinic space group C2/c and exhibits a crystal structure consisting of neutral 1-D chains with a repeating -Pt-Pt-I- unit lying on the crystallographic 2-fold axis parallel to the b axis. The Pt-Pt distance at 293 K is 2.684 (1) Angstrom in the dinuclear unit, while the Pt-I distances are essentially equal (2.982 (1) and 2.978 (1) Angstrom). 3 shows relatively high electrical conductivity (5 -30 S cm(-1)) at room temperature and undergoes a metal-semiconductor transition at TM-S = 205 K. The XPS spectrum in the metallic state reveals a Pt2+ and Pt3+ mixed-valence state on the time scale of XPS spectroscopy (similar to 10(-17) S). In accordance with the metal-semiconductor transition, anomalies are observed in the temperature dependence of the crystal structure, lattice parameters, X-ray diffuse scattering, and polarized Raman spectra near TM-S. In variable-temperature crystal structure analyses, a sudden and drastic increase in the Pt-I distance near the transition temperature is observed. Furthermore, a steep increase in U-22 of iodine atoms in the I-D chain direction has been observed. The lattice parameters exhibit significant temperature dependence with drastic change in slope at about 205-240 K. This was especially evident in the unit cell parameter b (I-D chain direction) as it was found to lengthen rapidly with increasing temperature. X-ray diffraction photographs taken utilizing the fixed-film and fixed-crystal method for the metallic state revealed the presence of diffuse scattering with line shapes parallel to the a* axis indexed as (-, n + 0.5, 1) (n; integer). Diffuse scattering with k = n + 0.5 is considered to originate from the 2-fold periodical ordering corresponding to -Pt2+-Pt2+-I-Pt3+-Pt3+-I-or-Pt2+-Pt3+-I-Pt3+-Pt2+-I- in an extremely short time scale. Diffuse lines corresponding to 2-D ordering progressively decrease in intensity below 252 K and are converted to the diffuse planes corresponding to I-D ordering near TM-S. Furthermore, diffuse planes condensed into superlattice reflections below TM-S. Polarized Raman spectra show temperature dependence through a drastic low-energy shift of the Pt-I stretching mode and also through broadening of bands above TM-S.

Yoshiki OZAWA, 2001, 'Introduction to the Weissenberg Camera.', <i>Nihon Kessho Gakkaishi</i>, vol. 43, no. 5, pp. 347-352

Crystallographic studies of metastable and excited state molecular crystals provide direct geometrical information for those of light-induced structure changes or transition states in solid-state chemical reactions. Such geometry changes will give only very small difference in X-ray diffraction intensities. Special instrumentation and data acquisition technique must be required in order to detect small changes of intensity. This review describes a few examples of experimental and analysis technique applying to photo-excited crystallography.

A new series of linear-type Mo₂Rh₂ tetranuclear complexes, [{Cp*Rh^III(&mu;-SCH₃)₃Mo^VIO₂}₂(&mu;-O)] (1), [{Cp*Rh^III(&mu;-SCH₃)₃Mo^VO}₂(&mu;-O)₂] (2), and [{Cp*Rh^III(&mu;-SCH₃)₃Mo^VO}₂(&mu;-O)(&mu;-S)] (3), has been prepared from reactions of the triple cubane-type oxide cluster [(Cp*Rh)₄Mo₄O₁₆]&middot;2H₂O with CH₃SH. These tetranuclear complexes have been characterized by elemental analysis, infrared, electronic, and ¹H, ¹³C, and ¹⁷O NMR spectroscopies as well as X-ray analysis. <br>Complex 1 crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 15.348(3), b = 14.059(3), c = 17.879(3) &Aring;, &beta; = 107.11(2)&deg;, V = 3690(1) &Aring;³, and Z = 4. Complex 2 crystallizes in the monoclinic space group C2/c (No. 15) with a = 25.334(4), b = 21.271(2), c = 17.831(3) &Aring;, &beta; = 129.70(5)&deg;, V = 7393(2) &Aring;³, and Z = 8. Complex 3 crystallizes in the orthorhombic space group Pcab (No. 61) with a = 16.902(3), b = 26.631(3), c = 16.855(2) &Aring;, V = 7587(3) &Aring;³, and Z = 8. Complex 1 involves a nearly linear &ldquo;O₂Mo^VI(&mu;-O)Mo^VIO₂&rdquo; framework, to which two Cp*Rh^III units are linked by &mu;-SCH₃ ligands. Complexes 2 and 3 have an analogous tetranuclear Mo^V₂Rh^III₂ structure in which the Mo^V and Rh^III atoms are bridged by three &mu;-SCH₃ ligands. Complex 2 contains a doubly-bridged &ldquo;OMo^V(&mu;-O)₂Mo^VO&rdquo; framework with an Mo&ndash;Mo distance of 2.564(1) &Aring;, while 3 contains a &ldquo;OMo^V(&mu;-O)(&mu;-S)Mo^VO&rdquo; framework with an Mo&ndash;Mo distance of 2.666(1) &Aring;. Complexes 2 and 3 retain the tetranuclear structure but are fluxional in solution. The fluxional behaviors are due to intramolecular rotations of the &ldquo;Cp*Rh(&mu;-SCH₃)&rdquo; moieties on the trigonal planes of the octahedral Mo centers. Line-shape analyses of variable-temperature ¹H NMR spectra measured in C₆D₅Cl yield activation parameters of &Delta;H^&Dagger; = +80.2 kJ mol^&minus;1, &Delta;S^&Dagger; = +22.1 J K^&minus;1 mol^&minus;1, and &Delta;G^&Dagger;_{298 K} = +73.6 kJ mol^&minus;1 for the rotation in 2 and &Delta;H^&Dagger; = +76.8 kJ mol^&minus;1, &Delta;S^&Dagger; = +21.1 J K^&minus;1 mol^&minus;1, and &Delta;G^&Dagger;_{298 K} = +70.5 kJ mol^&minus;1 for that in 3.

New photocrystallographic and cryogenic techniques are tested in a 40 K study of the 2.44 ms lifetime excited state of [RhBr2(pyridine-d(5))]Br. A modulation method is used in which a laser beam is interrupted by a mechanical chopper with a preselected frequency and the diffracted X-ray beam gated in synchronization with the chopper phase. Wilson-type plots of the response ratio eta, defined as eta(hkl) = [I-on(hkl) - I-off(hkl)]/I-off(hkl), give evidence of a small (similar or equal to 2 K) temperature increase upon laser irradiation of the crystal at 40 K. The temperature change decreases when the chopper frequency is increased from 20 to 40 to 80 Hz, pointing to a gradual temperature increase during the laser-on period. A least-squares method for the refinement of excited-state parameters, with the experimental response ratios as observations, is described and applied using 46 experimental values of eta. Although there is an indication that the Rh-Br bonds are shortened on excitation, the current data-set is too limited to allow unequivocal determination of the geometry changes upon excitation; the study presented is therefore primarily a description of the development and testing of new techniques.

This paper reports (i) a rational synthesis of heterometallic sulfide clusters with M-S-M&#039; (M and M&#039; = Rh, W, and Cu) groups, (ii) structures and bonding of the M-S-M&#039; groups determined by X-ray crystallographic analysis and IR spectroscopy, and (iii) reactivity of the M-S-M&#039; groups unique to higher-nuclearity heterometallic sulfide clusters toward H 2 O and H 2 S. A branched-type octanuclear sulfide cluster [{Cp*RhP(OEt) 3 (μ-WS 4 )(CuCl)Cu} 2 -(μ-Cl) 2 ] (4, Cp* = η 5 -C 5 Me 5 ) was stepwise prepared from the following sequence: [Cp*RhP(OEt) 3 Cl 2 ] (1, mononuclear) → [Cp*RhP(OEt) 3 WS 4 ] (2, dinuclear) → [Cp*RhP(OEt) 3 (μ-WS 4 )CuCl] (3, linear-type trinuclear) → 4 by a systematic building-block method. A bridging sulfide ligand in the W-S-Cu group of 4 reacts with a water-saturated CH 2 Cl 2 solution to convert the terminal O atom of [{Cp*RhP(OEt) 3 (μ-WOS 3 )(CuCl)Cu} 2 (μ-Cl) 2 ] (5, linked incomplete cubane-type octanuclear) with a drastic structural change in the cluster framework. The transformation reaction of 4 to 5 includes the first example of the conversion of the bridging S atom in the M-S-M&#039; group into the terminal O atom without releasing the metal atoms, and this reaction is peculiar to the higher-nuclearity heterometallic sulfide cluster 4. Clusters 4, 5, and 6 ([Cp*RhP(OEt) 3 (μ-WOS 3 )CuCl], butterfly-type trinuclear) react with H 2 S in CH 2 Cl 2 giving 3 as a major product. The formation of 3 in these reactions are based on the reactivity of M-S-Cu groups in the sulfide clusters toward H 2 S: the (μ 3 -S)-Cu bonds are easily broken by H 2 S, but not the (μ 2 -S)-Cu ones. The crystal data for 1, 2, 3, 4, 5, and 6 confirmed by X-ray analysis are as follows. 1: C 16 H 30 Cl 2 O 3 PRh, orthorhombic, P2 1 cn, a = 8.988(3) Å, b = 28.591(5) Å, c = 8.276(3) Å, 2 = 4. 2: C 16 H 30 O 3 PRhS 4 W, monoclinic, P2 1 /n, a = 14.633(2) Å, b = 15.191(2) Å, c = 11.490(1) Å, β = 104.97(1)°, Z = 4. 3: C 16 H 30 ClCuO 3 PRhS 4 W, monoclinic, P2 1 /m, a = 10.221(2) Å, b = 11.943(2) Å, c = 10.809(1) Å, β = 94.40(1)°, Z = 2. 4: C 32 H 60 Cl 4 Cu 4 O 6 P 2 Rh 2 S 8 W 2 , monoclinic, P2 1 /n, a = 10.170(3) Å, b = 14.495(3) Å, c = 19.411(3) Å, β = 104.42(1)°, Z = 2. 5·2DMF: C 38 H 74 Cl 4 Cu 4 N 2 O 10 P 2 Rh 2 S 6 W 2 , monoclinic, P2 1 /c, a = 10.011(3) Å, b = 17.115(3) Å, c = 18.678(3) Å, β = 95.10(2)°, Z = 2. 6: C 16 H 30 ClCuO 4 PRhS 3 W, orthorhombic, P2 1 nb, a = 14.515(2) Å, b = 17.225(3) Å, c = 10.261(3) Å, Z = 4.

Physical and structural properties of the MMX-type halogen-bridged mixed-valence complex, Pt-2(dta)(4)I (dta = CH3CS2) were investigated. This complex exhibits metallic conduction above room temperature, which is the first observation in halogen-bridged 1-D transition-metal complexes. Below 300 K, the metal-semiconductor transition was observed. The mixed-valence state of this compound is discussed.