Abstract

We performed density functional calculations to investigate the electronic and magnetic properties of BN-substituted non-classical fullerenes. The substitutional structures, binding energies, energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), ionisation potentials, electron affinities, vibrational frequencies and nucleus-independent chemical shifts (NICS) were systematically investigated. The binding energies of the BN-substituted non-classical fullerenes were found to be slightly smaller than those obtained for pure non-classical fullerenes. While the reverse trend was observed for BN-substituted \(\hbox {C}_{46}\) and \(\hbox {C}_{32}\) fullerenes, it was found that the BN-substituted \(\hbox {C}_{62}\) fullerene has bigger ionisation potentials (IP) and smaller electron affinities (EA) than that of their parents. Because of low concentration of BN impurity, the IR spectra in the BN-substituted fullerenes are very similar to those of their parents, which can be considered as two separate regions: a low-frequency region at 200–1000 \(\text {cm}^{-1}\) corresponding to the out-of-plane bending and breathing modes and a high-frequency region at 1000–1800 \(\text {cm}^{-1}\) derived from the stretching of C–B, C–N, B–N and C–C bonds. It was shown that diatropic and paratropic ring currents of hexagons and pentagons together with the harshly antiaromatic character of the four-membered ring combine to produce a relatively small NICS at the centre of the \(\hbox {C}_{62}\) and \(\hbox {C}_{46}\) fullerene cages. The decrease in the antiaromatic and aromatic character of the \(\hbox {B}_{2}\hbox {N}_{2}\) ring and the adjacent hexagons affects the aromaticity character of the BN-substituted fullerenes.

Graphic Abstract

中文翻译：

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含方环的BN取代的非经典富勒烯

摘要

我们进行了密度泛函计算，以研究BN取代的非经典富勒烯的电子和磁性。系统地研究了最高占据分子轨道（HOMO）与最低未占据分子轨道（LUMO）之间的取代结构，结合能，能隙，电离势，电子亲和力，振动频率和与核无关的化学位移（NICS）发现BN-取代的非经典富勒烯的结合能比对于纯非经典富勒烯获得的结合能稍小。对于BN取代的\（\ hbox {C} _ {46} \）和\（\ hbox {C} _ {32} \）富勒烯，观察到相反的趋势，但发现BN取代的\（\ hbox {C} _ {62} \）富勒烯比其母体具有更大的电离势（IP）和更小的电子亲和力（EA）。由于BN杂质的浓度低，BN取代的富勒烯中的红外光谱与其母体的红外光谱非常相似，可以将其视为两个独立的区域：200–1000 \（\ text {cm } ^ {-1} \）对应于平面外弯曲和呼吸模式以及从C的拉伸得出的1000–1800 \（\ text {cm} ^ {-1} \）处的高频区域–B，C–N，B–N和C–C键。结果表明，六边形和五边形的变径和副变环电流以及四元环的严格的抗芳烃特性相结合，在\（\ hbox {C} _ {62} \）的中心产生相对较小的NICS。和\（\ hbox {C} _ {46} \）富勒烯笼子。\（\ hbox {B} _ {2} \ hbox {N} _ {2} \）环和相邻六边形的抗芳族和芳族特征的降低会影响BN取代的富勒烯的芳族特征。

图形摘要