C_(52)N_4四面體型(T_d)球簇分子之半經驗分子軌域法理論研究

A Semiempirical Theoretical Study of Tetrahedral Type (T_d) C_(52)N_4 Molecule

孫光中(Kuang-Chung Sun) ； 盧文琦(Wen-Chi Lu) ； 孫光明(Kuang-Ming Sun)

《化學》 66卷4期 (2008/12) Pp. 327-338

https://doi.org/10.6623/chem.2008032

摘要

本文採用半經驗分子軌域法PM3針對屬於T_d點對稱群之C_(52)N_4(5)與C_(52)N_4(6)球簇分子所進行之計算與分析。與C_(36)N_4、C_(24)N_4球簇分子不同的是：屬於T_d點對稱群之C_(52)N_4球簇分子有兩種立體結構，而與其等電子之異構物C_(52)(CH)_4亦有兩種。其一、四個位於T_d頂點的N_v在三個五角形的頂點，其二、四個位於T_d頂點的N_v在三個六角形的頂點。在全幾何最佳化(Fully Optimization)下，與CN_(36)N4、C_(24)N_4球簇分子不同的是：原本上述屬於T_d點對稱群之C_(52)N_4球簇分子，不再保有原有的T_d點對稱群，而是經由傑恩-泰勒扭變(Jahn-Teller Distortion)至屬於T_d次群(Subgroup)的D_(2d)較低對稱群結講，以保有其穩定性。經由振動頻率的計算，C_(52)N_4(5)分子振動頻率在260.4(E)~1755.0(A_1)cm^(-1)，C_(52)N_4(6)分子振動頻率在253.7(E)~1730.8(B_1)cm^(-1)間；二者皆為穩定的立體球簇分子。而由非區域化能量的觀點查看分佈在整體球簇表面情形，明顯地看出C_(52)N_4(5)(D_(2d)分子較C_(52)N_4(6)(D_(2d))分子更為穩定，其分佈之非區域化能與富勒烯C_(60)相近。本研究所有證據顯示C_(52)N_4分子為一穩定之異碳球烯分子，頗值得實驗化學家致力將其合成出。

關鍵字

C_(52)N_4 ； C_(56) ； C_(36)N_4 ； C_(24)N_4 ； C_(60) ； 半經驗分子軌域法 ； 非區域化能量

並列摘要

The semiempirical PM3 calculations are carried out on C_(52)N_4(5) and C_(52)N_4(6) molecules of T_d symmetry. Different from C_(36)N_4 and C_(24)N_4 clusters, C_(52)N_4 cluster which belongs to T_d symmetry that has two possible geometric structures, and is isoelectronic with the fullerene derivative C_(52)(CH)_4. The isoelectronic isomer of the C_(52)(CH)_4 molecule also has two types. First, the four N_v’ atoms are located at the T_d top point which consist of three five-membered rings. Second, the four N_v’ atoms are located at the T_d top point which consist of three six-membered rings. At fully optimization, unlike C_(36)N_4 and C_(24)N_4 clusters, the T_d point group of C_(52)N_4 cluster can not be remained any more. However, the stability was obtained by Jahn-Teller distortion and its geometric structure from Td point group turn into the lower D_(2d) symmetry subgroup. Proved by the vibrational frequency, both of the C_(52)N_4(5) which at 260.4 (E)~1755.0 (A_1) cm^(-1) and C_(52)N_4(6) which at 253.7 (E)~1730.8 (B_1) cm-1 are all stable structures. Besides, in terms of delocalization energy, it is apparently that the structure of C_(52)N_4(5) (D_(2d)) is more stable than C_(52)N_4(6) (D_(2d)). Furthermore, the distribution of delocalization energy and first ionization energy of C_(52)N_4(5) (D_(2d)) are similar to those of fullerene C_(60). All evidences of this research proved that C_(52)N_4 cluster is a stable heterofullerene and the molecule is worth to be synthesized by organic chemist.

並列關鍵字

C_(52)N_4 ； C_(56) ； C_(36)N_4 ； C_(24)N_4 ； C_(60) ； Semiempirical MO method ； Delocalization energy.