C₅Ch₅およびC₆Ch₆ (Ch = S, Se, Te)の分子構造と芳香族性の評価

Abstract

(CO)_nで記されるCO単位の環状重合体であるオキソカーボンは長年関心を集めてきた．しかし，Oをカルコゲン原子Ch = (S, Se, Te)で置換した擬オキソカーボン類については，これまで系統的に理論計算による検討はなされてはいない．そこで今回，(CCh)_n (n = 5,6)についてDFT計算による分子構造の最適化とNICS値の算定を試みた．最適化計算からは，カルコゲンが高周期になるにつれて構造の平面性が増すことが分かった．NICS値からは，(CTe)₆でベンゼンに匹敵する芳香族性が示唆された．

Figures

Figure 1.

 Chemical structure of C₅Ch₅ and C₆Ch₆.

Figure 2.

 Optimized molecular structures of C₅Ch₅

Figure 3.

 Optimized molecular structures of C₆Ch₆

Figure 4.

 Visualized electrostatic potentials; C₆O₆, C₆S₆, C₆Se₆, C₆Te₆ and C₆H₆ (from left to right).

Tables

Table 1. Natural population results of C₅Ch₅.

	Charge	Natural Electron Configuration
O	−0.38	[core]2S (1.71) 2p (4.66) 3p (0.01) 3d (0.01)
S	0.26	[core]3S (1.75) 3p (3.96) 4S (0.01) 3d (0.01) 4p (0.01) 5p (0.01)
Se	0.31	[core]4S (1.81) 4p (3.86) 4d (0.01) 6p (0.01)
Te	0.39	[core]5S (1.85) 5p (3.75) 5d (0.01) 7p (0.01)

Table 2. Natural population results of C₆Ch₆.

	Charge	Natural Electron Configuration
O	−0.39	[core]2S (1.71) 2p (4.66) 3p (0.01) 3d (0.01)
S	0.24	[core]3S (1.77) 3p (3.96) 3d (0.01) 5p (0.01)
Se	0.30	[core]4S (1.82) 4p (3.86) 4d (0.01) 6p (0.01)
Te	0.33	[core]5S (1.85) 5p (3.80) 5d (0.01) 7p (0.01)

Table 3. NICS results of C₅Ch₅.

	C5O5	C5S5	C5Se5	C5Te5
NICS	21.95	35.80	7.62	5.81

Table 4. NICS results of C₆Ch₆.

	C6O6	C6S6	C6Se6	C6Te6
NICS	17.56	−1.31	−1.58	−7.19

Table 5. Bond order results of C₅Ch₅

Ch	C-Ch	C-C
O	1.87	0.91
S	1.75	1.04
Se	1.38	1.17
Te	1.25	1.21

Table 6. Bond order results of C₆Ch₆.

Ch	C-Ch	C-C
O	1.89	0.91
S	1.48	1.14
Se	1.38	1.18
Te	0.97	1.36

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