Gal Jean-François, Maria Pierre-Charles, Decouzon Michèle, Mó Otilia, Yáñez Manuel, Abboud José Luis M
Chimie des Matériaux Organiques et Métalliques, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France.
J Am Chem Soc. 2003 Aug 27;125(34):10394-401. doi: 10.1021/ja029843b.
The gas-phase lithium cation basicities (LCBs) of naphthalene, azulene, anthracene, and phenanthrene were measured by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The structures of the corresponding complexes and their relative stabilities were investigated at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d) level of theory. In the theoretical survey, pyrene, coronene, [3]phenylene, angular [3]phenylene, and circumcoronene were also included. The strength of the binding to a given aromatic cycle decreases as the number of cycles directly fused to it increases. Hence, the stability of the outer pi-complexes, in which Li(+) is attached to the peripheral rings, is systematically greater than that of the complexes in which the metal is attached to the inner rings. The energy gap between these local minima decreases as the number of fused rings in the system increases. This result seems to indicate that, as the size of the system increases, the rings tend to lose their peculiarities, in such a way that in the limit of a graphite sheet all rings would exhibit identical characteristics and reactivity. The good agreement between calculated LCBs and experimental values lends support to the enhanced stability of the outer complexes. The activation barriers connecting these local minima decrease as the number of fused cycles increases, but seems to tend toward a limit. [3]Phenylene and angular [3]phenylene exhibit enhanced LCBs reflecting nonnegligible Mills-Nixon effects that increase the electron-donor properties of these annelated benzenes.
通过傅里叶变换离子回旋共振（FT-ICR）质谱法测量了萘、薁、蒽和菲的气相锂阳离子碱度（LCB）。在B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d)理论水平上研究了相应配合物的结构及其相对稳定性。在理论研究中，还包括了芘、蒄、[3]亚苯基、角[3]亚苯基和外周蒄。与给定芳香环的结合强度随着直接稠合到其上的环的数量增加而降低。因此，Li(+)附着在外围环上的外部π配合物的稳定性系统地大于金属附着在内环上的配合物的稳定性。随着系统中稠合环数量的增加，这些局部极小值之间的能隙减小。这一结果似乎表明，随着系统尺寸的增加，环倾向于失去其特殊性，以至于在石墨片的极限情况下，所有环将表现出相同的特征和反应性。计算得到的LCB与实验值之间的良好一致性支持了外部配合物稳定性的增强。连接这些局部极小值的活化能垒随着稠合环数量的增加而降低，但似乎趋于一个极限。[3]亚苯基和角[3]亚苯基表现出增强的LCB，反映了不可忽略的米尔斯-尼克松效应，该效应增加了这些稠合苯的给电子性质。
