3P136
ELG 法による擬一次元金属錯体の高圧下 I－M－I 遷移の超効率的定量解析（九大院・総理工 1，JST-CREST2）○Liu Kai1，折本 裕一 1，青木 百合子 1, 2

Highly efficient analyses of I-M-I transition in quasi-1D metalcomplexes by elongation method(Kyushu Univ.1，JST-CREST2) ○Liu Kai1，Yuuichi Orimoto1，Yuriko Aoki1, 2

The one-dimensional (1D) d8 transition metals systems, [M(dmg)2, M=Ni, Pd and Pt,
dmg=Bis(dimethylglyoximato)] have attracted a lot of attentions for their interesting electricaland optical properties. For example, the Pt(dmg)2 system (structure shown in Fig. 1(a)) basedon molecular stacking units exhibits insulator-to-metal-to-insulator (IMI) transition [1] at highpressure with potential applications of pressure switch devices. For the further development of
this kind of metals, we carefully examined the nature of this transition from the stand point ofelectronic structures .
The structure of Pt(dmg)2, is a d8-square-planar complex with Pt-Pt distance of 3.26 Å inthe direction of stack at normal pressure (shown in Fig. 1(b)). However, the distance of thismetal bond (Pt-Pt) between two units will decrease when the pressure increases.
Considering the stacking behaviors of the Pt(dmg)2 system, we deveploed the elongation(ELG) method [2] including the relativistic effectsby third order Douglas-Kroll (DK3) totheoretically simulate the chain stacking process for heavy metal included systems andexamine the orbital energy gaps changes along with the increasing of unit size at different
distance of metal bond. The different distance of metal bond represents the situation ofPt(dmg)2 system at different pressure.
(a)(b)Fig. 1 The structure of Pt(dmg)2. (a). For one Unit, (b) For the stacking structure.

The orbital energy gaps of 16 units of Pt(dmg)2 system, calculated by ELG with DK3correction at mini basis set of HF level, become narrow as the chain elongates (shown in Fig.
2). Meanwhile, the orbital gap also decreases, if the distance of metal bond decreases. In otherwords, when the pressure increases, the electrical conductivity of Pt(dmg)2 system isenhanced because of the narrowing orbital energy gaps.
In order to more accurately investigate the details of this gap changes, 8 units of Pt(dmg)2
are calculated by mPW1PW91 method with large basis set. The LanL2DZ basis set isemployed to include the relativistic effect for metal atoms, and 6-31G(d,p) for the rest atoms.
The orbital energy gap of 8 units of Pt(dmg)2 will
decrease as the pressure increases. However, when thedistance is less than 2.6 Å, the energy gap becomes large
again (shown in Fig. 3). This energy gaps changes arevery similar to the experiment data. When the pressure of
the system increases, the Pt(dmg)2 system indicates theIMI transition. The orbital shape of the HOMO andLUMO is also compared as the metal bond changes forthe distance of metal bond is equal to 2.3 Å, 2.6 Å, and3.2 Å. The result shows that at normal pressure (3.2 Å)
the transition is attributed to dz2 to dpz. While when thepressure increases, the transition is changed to dpz to dz2,
at the same time, because of the small energy gap, thematerial shows the metallic properties. When thepressure is increasing, the transition changes back again.
However, the orbitals involving the transition becomeless. This change of orbital transition clearly explains theexperiment phenomenon. Under the pressures, the orbitaltransition arises the IMI transition of Pt(dmg)2 systems.
This findings will also guide us for the further material
design and properties improvement.

Fig. 2 The orbital energy gap

changes by ELG method with DK3approximation.

Fig. 4 The orbital shape ofFig. 3 The orbital energy gaps of 8 units of Pt(dmg)2 system.

HOMO and LUMO.

[1] Takeda, K.; Shirotani, I.; Yakushi, K. Chem. Mater. 2000, 12, 912.
[2] Imamura, A.; Aoki, Y.; Maekawa, K. J. Chem. Phys. 1991, 95, 5419.