Theoretical study of a novel organic electride with large nonlinear optical responses

Abstract

The design of stable organic electrides with high nonlinear optical (NLO) properties is a challenge in organic and materials chemistry. Here we theoretically design of a novel organic molecular electride model, Li + (C 20 H 15 Li 5 )e − , by modifying the lithiation and Li-doping based on dodecahedrane (C 20 H 20 ). Its electride characteristic is verified by the quantum theory of atoms in molecules and electron localization function analyses. For the first time, the strategy of steric protection is applied to improve the stability of the organic electride Li + @(C 20 H 15 Li 5 )e − , in which the closed C 20 cage serves not only as the ligand with a negative inner electric field to stabilize the Li cation but also as a barrier to prevent the Li cation from escaping. Meanwhile, the released excess electron is firmly captured in the cavity of Li 5 . Moreover, Li + (C 20 H 15 Li 5 )e − displays a remarkably large first hyperpolarizability of 1.4 × 10 4 au with potential application in organic second-order NLO materials.Electrides are a novel kind of ionic compounds in which electrons serve as anions, and considered to have potential applications in nonlinear optics. Here, a new and stable organic electride, Li@C 20 H 15 Li 5 , was theoretically designed based on dodecahedrane (C 20 H 20 ). First, five H atoms in one five-membered carbon ring of C 20 H 20 are substituted by five Li atoms to form the Li salt (C 20 H 15 ) δ-(Li 5 ) δ+ with the large dipole moment of 9.6 D, forming the molecular field. Second, an additional Li atom is encapsulated in the cage, and the valence electron of Li is polarized in the molecular field of C 20 and then pushed outside the cage to give rise to the excess electron, which is captured by the cavity formed by five Li atoms to form the electride Li + (C 20 H 15 Li 5 )e − . Additionally, in the dimer of the electride Li@C 20 H 15 Li 5 , both the Li cation and the electron are sealed in the carbon and Li cages, effectively improving the stability of the electride. In addition, the electride characteristics of the monomer and dimer were verified by the topology AIM and ELF. This electride has a remarkably large first hyperpolarizability and thus may be a promising building block for high-performance NLO materials based on electrides. ACKNOWLEDGEMENTS

Demonstrating the Potential of Alkali Metal-Doped Cyclic C6O6Li6 Organometallics as Electrides and High-Performance NLO Materials

“…Thus, Li + (C 20 H 15 Li 5 )e − exhibits a large value of hyperpolarizability (1.4 × 10 4 au) with potential for application in NLO materials. 64 Mahmood and co-workers analyzed the organometallic C 6 O 6 surface for the NLO response. They doped superalkalis on the C 6 O 6 surface and achieved electride characteristics in their designed complexes with large hyperpolarizability.…”

“…Here, the excess electrons are released, which remain encapsulated in the Li 5 cavity. Thus, Li + (C 20 H 15 Li 5 )­e – exhibits a large value of hyperpolarizability (1.4 × 10 4 au) with potential for application in NLO materials . Mahmood and co-workers analyzed the organometallic C 6 O 6 surface for the NLO response.…”

A DFT study of the second-order nonlinear optical properties of Ru(ii) polypyridine complexes

“…[2][3][4][5] In 1987, Green et al first published details of organometallic complexes equipped with considerably larger SHG responses than previously reported inorganic and organic compounds; 6 since then, the NLO properties of organometallic complexes have attracted more and more attention. 7 Relative to inorganic crystals and purely organic complexes, [8][9][10] organometallic complexes have large molecular structures and chemical versatility, and they can show intriguing NLO properties arising from the integration of optical, magnetic, and redox-switching properties. [11][12][13] In recent years, organometallic complexes have gradually become excellent candidate NLO materials.…”

Li4EPc: A metallo‐organic electride comprising metal‐nitrogen bonds

“…Later on numerous organic as well as inorganic electrides have been designed with a high amount of electron localization into it. Ligands with multi nitrogen centers give more stability to the organic electrides [11]. X‐ray crystallography cannot detect the presence of confined electrons in an electride, thus experimental characterization of an electride is still very challenging [1].…”