セイスイアツ カ ノ [Pt(en)2] [Pt(en)2Cl2] (ClO4)4 ノ ギ イチジゲン デンカ ミツドハ ノ コウガクテキ ケンキュウ

We have measured optical absorption, photoinduced absorption, and Raman scattering in the quasi-one-dimensional mixed-valence complex [Pt(en)2][Pt(en)2Cl2](Cl04)4 (where ‘‘en’’ is an abbreviation for ‘‘ethylenediamine’’), under hydrostatic pressure up to 3 GPa at temperatures in the range 110–300 K. Analyzing the results by use of the Morse potential, we have evaluated the Peierls gap Eg, the electron-phonon coupling constant β, the Peierls distortion of Cl ions, u, and the supertransfer energy t0: Eg=3.0 eV, β=1.94 eV/Å, and t0=0.52 eV at atmospheric pressure; Eg, β, and ‖u‖ decrease with increasing pressure because t0 is enhanced significantly by the contraction of the Pt-Pt & electrons of Pt ions are delocalized. It has been established that the intragap absorption which is enhanced by pressure and photoexcitation arises from the soliton-to-band transitions mediated by neutral solitons with a coherence length of only one Pt-Pt distance: The absorption band exhibits two peaks, A and B, at 1.68 and 2.0 eV, corresponding to the van Hove singularities of quasi-one-dimensional conduction and valence bands. Such a small coherence length of the soliton is crucial for an understanding of this novel double-peak spectrum.最大3 GPaまでの静水圧下でハロゲン架橋擬一次元白金錯体[Pt(en)2][Pt(en)2Cl2](ClO4)4のギャップ間遷移光吸収、レーザ誘起光吸収およびラマン散乱を測定した。１つの理論ポテンシャルを導入してデータを解析し、パイエルスギャップ、パイエルス変位、電子・音子結合定数および移動積分の圧力依存性を評価した。これらの結果は、レーザ誘起ミッドギャップバンドが最近接白金原子間距離の程度のサイズを持った中性ソリトンに起因するという考え方を支持する。このミッドギャップバンドが見かけ上2つのピークから成ることも擬一次元半導体特有の価電子帯と伝導帯の分散で理解できることを指摘した