Nobuyuki Matsushita

Photo-Induced Absorption Band in One-Dimensional Halogen-Bridged Mixed-Valence Platinum Complex: [Pt(en)2][PtI2(en)2](SO4)2·6H2O and its Au-Doped Complex: [AuxPt1-xI(en)2]SO4·3H2O

The intervalence charge-transfer absorption spectra in the mixed-valence complexes [Pt(en) 2 ][PtI 2 (en) 2 ](SO 4 ) 2 ·6H 2 O and [Au x Pt 1- x I(en) 2 ]SO 4 ·3H 2 O ( x =0.03) have been investigated at 4.2 K. In these complexes, below the charge-transfer absorption edge, a weak absorption band ( A -band) has been observed for the light polarized parallel to the chain axis. When these complexes were irradiated with the light in the region of the charge-transfer transition from Pt II to Pt IV , the absorption coefficient of the A -band increased remarkably, which implies that the A -band is a photo-induced absorption band. The photo-induced effect for the A -band in [Au x Pt 1- x I(en) 2 ]SO 4 ·3H 2 O ( x =0.03) is more intense than that in [Pt(en) 2 ][PtI 2 (en) 2 ](SO 4 ) 2 ·6H 2 O. The A -band suggests the existence of new excitations such as a soliton-like excitation in the electronic state of the platinum chains.

Spatial correlations in the valence of metal ions in Ni1-xPdx(chxn)2Br3

X-ray scattering experiments have been performed on a quasi-one dimensional system, Ni 1- x Pd x (chxn) 2 Br 3 . Strong diffuse scattering was observed for x > 0.7, and it was interpreted as due to spatial inhomogeneity in the valence of metal ions. This inhomogeneity takes the form of CDW in which the metal ions within a chain have valences alternating between +2 and +4. Correlations in the valence sequence could be determined parallel as well as perpendicular to the chain direction. Pair correlation functions deduced from the measurements show the existence of strong correlation between the positions of bridging Br ions and those of Br counter ions. It is concluded that the valence of metal ions for x <0.7 is +3. These results are consistent with previous data on optical and magnetic measurements.

A three-dimensional iodo-bridged mixed-valence gold(I,III) compound, Cs2AuIAuIIII6

The title compound, dicaesium gold(I) gold(III) hexaiodide, has a distorted perovskite structure. The crystal contains compressed and elongated [AuI6] octahedra, which are stacked alternately along the [001] and [110] directions by sharing all the corner I atoms. The compound is also characterized by the assembly of the gold complex ions, [AuII2]− and [AuIIII4]−. The position of the two halogen atoms of Cs2AuIAuIIII6 is closer to the midpoint between the two Au atoms than in Cs2AuIAuIIICl6. On the other hand, the distortion from the cubic system to the tetragonal system in the iodide compound is slightly larger than that in the chloride.

Counter-ion radius dependence of the mixed-valence state on MX chain platinum complexes

Abstract We have investigated the size effect of the counter anion influencing to the mixed-valence state in MX chain platinum complexes. In order to study the counter-ion radius dependence of the mixed-valence state, we have measured the polarized reflectance spectra of [Pt(en)2][PtCl2(en)2]Y4 (en=ethylenediamine, Y=PF6, HSO4, BF4) in single crystals, and analyzed the crystal structure of [Pt(en)2][PtCl2(en)2](BF4)4 by X-ray diffraction method. From comparing the tetrafluoroborate, the perchlorate, the hydrogensulfate and the hexafluorophosphate in the series of the chloro-bridged complex, we found that the mixed-valence gap of platinum decreases with decreasing the counter-anion radius.

A Luminescent Nonlinear-chain Tetracyanoplatinate(II) Forming a Charge-transfer Complex with Methyl Viologen

We display that a tetracyanoplatinate(II) forming a charge-transfer complex with methyl viologen dication in the crystal exhibits intense luminescence despite no direct Pt···Pt interaction.

Controlling the mixed-valence state of halogen-bridged one-dimensional platinum complexes by the substitution of counter ions

Abstract The mixed-valence states of halogen-bridged one dimensional platinum complexes have been investigated by the substitution of counter ions. The crystal structures of [Pt(en) 2 ][PtCl 2 (en) 2 ](PF 6 ) 4 (ClPF 6 ), [Pt(en) 2 ][PtCl 2 (en) 2 ](HSO 4 ) 4 (ClHSO 4 ) and [Pt(en) 2 ][PtBr 2 (en) 2 ](H 2 PO 4 ) 4 · 6H 2 O (BrH 2 PO 4 ) (en=ethylenediamine) have been determined by single-crystal X-ray diffraction, and their absorption edges have been measured at room temperature. The crystal data are: for ClPF 6 , monoclinic, P2/m, a =9.204(3), b =5.506(2), c=8.185(2) A , β =107.29(2)° and Z= 1 2 ; for ClHSO 4 , orthorhombic, Ibam, a =9.261(1), b =14.422(2), c=10.929(1) A , and Z =2; for BrH 2 PO 4 , monoclinic, P2/a, a =19.463(2), b =5.722(1), c=8.325(1) A , s =101.59(1)° and Z =1. The absorption edegs of the intervalence charge-transfer bands are c.a. 17,500cm −1 for ClPF 6 , c.a. 16,500cm −1 for ClHSO 4 and c.a. 14,800cm −1 for BrH 2 PO 4 . These results show that the counter ion size and the hydrogen atom of the counter ion influence the mixed-valence state. A mid-gap absorption band below the absorption edge is found at c.a. 14,700cm −1 in ClHSO 4 .

Mixed-Valence State of a One-Dimensional Platinum Complex with a Counter Ion Having Two Alkyl Chains and its Liquid Crystal Phase

We have investigated optical property and crystal structure of a one-dimensional halogen-bridged platinum complex (MX chain compound) with a counter ion having two alkyl chains, [Pt(en) 2 ][PtCl 2 (en) 2 ]{(CH 3 (CH 2 ) 7 CO 2 ) 2 CH 2 CHSO 3 } 4 2H 2 O, to elucidate influence of molecular fastener effect of the long alkyl chain on mixed-valence state of the platinum atoms. Thermal-behavior observations of the complex were also performed using a polarizing optical microscope without and with crossed nicols to examine thermal change of the mixed-valence state and appearance of the liquid crystal phase. Consequently, the complex has exhibited that the interaction between the platinum atoms is strengthened and the Pt II -Pt IV distance is shortened by doubling the number of alkyl chains around the platinum complex moieties compared with a corresponding PtCl chain complex with a single alkyl chain counter ion. We have also observed a texture of liquid crystal at about 200C. Mixed-Valence State One-Dimensional Halogen-Bridged Platinum Complex Long Alkyl Chain Molecular Fastener Effect Liquid Crystal Phase

Midgap absorption spectra in various kinds of halogen bridged mixed-valence Pt complexes

Abstract We have investigated several kinds of midgap absorption spectra due to the mismatch of valence alternation(nonlinear excitations such as solitons and polarons) in various kinds of halogen bridged mixed-valence Pt complexes, [Pt(en)2][PtX2(en)2](SO4)26H2O(X=Cl, Br and I), [PtX2(en)][PtX4(en)](X=Cl and Br), and [Pt(NH3)4][PtCl2(NH3)4](HSO4)4. Also we investigated the relationship between the stability of the mismatch of valence alternation and the crystal structure.

A one-dimensional iodine-bridged PtII/PtIV mixed-valence complex, catena-poly[[[bis­(ethyl­ene­diamine)­platinum(II)]-μ-iodo-[bis­(ethyl­ene­di­amine)platinum(IV)]-μ-iodo] hydrogenphosphate dihydrogenphosphate iodide trihydrate]

The title compound, {[PtIIPtIVI2(C2H8N2)4](HPO4)(H2PO4)I.3H2O}n, has a chain structure composed of square-planar [Pt(en)2]2+ and elongated octahedral trans-[PtI2(en)2]2+ cations (en is ethylenediamine) stacked alternately along the c axis and bridged by the I atoms; a three-dimensionally valence-ordered system exists with respect to the Pt sites. The title compound also has a unique cyclic tetramer structure composed of two hydrogenphosphate and two dihydrogenphosphate ions connected by strong hydrogen bonds [O...O = 2.522 (10), 2.567 (10) and 2.569 (11) A]. The Pt and I atoms form a zigzag ...I-PtIV-I...PtII... chain, with PtIV-I bond distances of 2.6997 (7) and 2.6921 (7) A, interatomic PtII...I distances of 3.3239 (8) and 3.2902 (7) A, and PtIV-I...PtII angles of 154.52 (3) and 163.64 (3) degrees . The structural parameters indicating the mixed-valence state of platinum, expressed by delta = (PtIV-I)/(PtII-I), are 0.812 and 0.818 for the two independent I atoms.

Optical Studies of MX Chain Complex [Pt(en)2] [PtBr2(en)2] (SO4)2-6H2O Under High Pressure

Abstract We have measured the absorption and resonance Raman spectra in single crystals of the MX chain complex [Pt(en)2][PtBr2(en)2](SO4)2.6H2O in order to study the mixed-valence state, the midgap state and the phase transition under various hydrostatic pressures up to 3.7 GPa at room temperature. Red shifts of both the intervalence charge-transfer absorption edge and the Pt-Br stretching mode Raman peak with increasing pressure show that the electronic state of PtII and PtIV in the mixed-valence state approaches that of PtIII. An absorption band appearing above 2.5 GPa and a Raman peak appearing above 1.6 GPa suggest that a new phase coexists at pressures above 1.6 or 2.5 GPa. On the other hand, no enhancement of the optical absorption in the region of the midgap absorption bands (A-, B- and C-bands) is observed. This result shows that the midgap state is not generated by applying pressure at room temperature.