作者：Tsung-Lung Li, Wencai?Lu
关键字：Alkali-rubrene complexes, Structural effects ,Intramolecular intercalation, Complexation energy,Density functional theory
论文来源：期刊
具体来源：Materials Chemistry and Physics
发表时间：2016年
The geometric and electronic structures of neutral monolithium- and monosodium-rubrene (Li1 Rub and Na1 Rub) isomers are investigated and compared with monopotassium-rubrene (K1 Rub). Based on the alkali binding site, all isomers of these alkali-rubrene complexes can be subdivided into two types: intramolecularly intercalated and extramolecularly adsorbed. The minimum-energy Li1 Rub and Na1 Rub are intercalated structures, whereas the minimum-energy K1 Rub is adsorbed. The fact that the intercalated Li1 Rub and Na1 Rub structures are energetically favorable over the adsorbed ones can be explained by two energy rules. First, “double” proximity of the intercalating alkali element to a pair of phenyl side groups enormously reduces the total energy. Second, accommodation of a minuscule intercalant does not significantly deform the carbon frame and, thus, increases the energy only by a small amount. Additionally, the peculiar effects of intramolecular intercalation on the electronic structures of molecules are also studied in this simulation of monoalkali intercalation. In the monoalkali-intercalated rubrene complex, only one of the two pairs of phenyl groups of rubrene is intercalated, intentionally leaving another pair pristine, which facilitates the comparison of electronic structures between the intercalated and pristine pairs of phenyl side groups in a single molecule. The uniformity of chemical environments of the phenyl groups of the intercalated Li1 Rub/Na1 Rub is deteriorated by the incorporation of the intercalant, and leads to their spectral characteristics in contrast to K1Rub. In particular, the introduction of the intercalant promotes the carbon 2p orbitals of the intercalated phenyl pair to take part in the electronic structures of the HOMO and LUMO peaks of Li1 Rub/Na1 Rub. The unpaired electron in the HOMO is delocalized over the backbone with higher probability of distributing over the central two fused rings than over the outer two.