Organic heterocyclic molecules become superalkalis

Abstract

An organic molecule which behaves like a superalkali has been designed from an aromatic heterocyclic molecule, pyrrole. Using first-principles calculation and a systematic two-step approach, we can have superalkali molecules with a low ionization energy, even lower than that of Cs. Couple cluster (CCSD) calculation reveals that a new heterocycle, C3N2(CH3)5 derived from a well-known aromatic heterocycle, pyrrole (C4H5N) has an ionization energy close to 3.0 eV. A molecular dynamics calculation on C3N2(CH3)5 reveals that the structure is dynamically stable.

Recent Progress on the Design, Characterization, and Application of Superalkalis

“…With the deepening of superalkali study, some special approaches beyond the above strategies have been also proposed to design superalkalis in recent years . For example, the fluorination of superalkaline earth metal cations was used to design a new kind of cationic (M‐F) + (M=OLi 4 , NLi 5 , CLi 6 , BLi 7 , and Al 14 , see Figure ) fluorides with superalkali character in 2014 .…”

“…This design principle was already used to obtain aromatic heterocyclic superalkali molecules by Reddy et al. in 2016 . Additionally, another 2( n +1) 2 electron counting rule was proposed to account for the spherical aromaticity of molecules.…”

“…To be specific, as for neutral molecules, the vertical IE (VIE) or adiabatic IE (AIE) is usually calculated to confirm their superalkali identities. The VIE is defined as the total‐energy difference between the cation and the neutral molecule both at neutral geometry, whereas the AIE is obtained when both the neutral and the cation geometries are optimized . The AIE is a better thermodynamic quantity to evaluate the reducibility of a molecule as it describes the difference in energy between the two potential energy surfaces.…”

“…Owing to the intriguing features mentioned above, superalkalis have received more and more attention in recent years, and a lot of effort has been devoted to designing and characterizing superalkalis of new types . To date, the scope of superalkalis has been extended from conventional mononuclear superalkalis to binuclear superalkali species, and then to polynuclear superalkalis .…”

“…To date, the scope of superalkalis has been extended from conventional mononuclear superalkalis to binuclear superalkali species, and then to polynuclear superalkalis . More recently, several studies have made attempts to propose some special superalkali species, such as nonmetallic superalkali cations, aromatic superalkali species, organo‐Zintl superalkalis, organic heterocyclic superalkalis, and so forth. Although superalkalis have experienced considerable development over the past several decades, there is no comprehensive review that covers the previous studies of these unique species.…”