Theoretical characterization of a series of N₅-based aromatic hyperhalogen anions

Abstract

Hyperhalogens are a class of highly electronegative molecules whose electron affinities even exceed those of their superhalogen ligands. Such species can serve as new oxidizing agents, biocatalysts, and building blocks of unusual salts, and hence are important to the chemical industry. Utilizing stable N5(-) as the ligand, a series of aromatic hyperhalogen anions, namely mononuclear M(N5)(k+1)(-) (M = Li, Be, B) and dinuclear M2(N5)(2k+1)(-) (M = Li, Be), have been reported here for the first time. Calculation results based on the density functional theory revealed that all the N5(-) subunits preserve their structural and electronic integrity as well as aromatic characteristics in these anions. Especially, these anionic molecules exhibit larger vertical electron detachment energies (6.76-7.86 eV) than that of the superhalogen ligand N5(-), confirming their hyperhalogen nature. The stability of these studied anions is guaranteed by their large HOMO-LUMO gaps, and positive dissociation energies of predetermined fragmentation pathways. We hope this work will not only provide evidence of a new type of hyperhalogen molecule but also stimulate more research interest and efforts in the amazing superatom realm.

Hyperhalogen properties of early-transition-metal borates

“…39 Recently, two series of hyperhalogen anions involving planar and cage-like superhalogen ligands were reported, respectively, and the concept of aromatic hyperhalogen was brought forward as well. 40,41 In this work, theoretical investigation of borates of the rst three subgroup elements, namely scandium, titanium, and vanadium, was presented. On the one hand, these transition metal (TM) elements have unlled d orbitals, which may render the resulting compounds magnetism.…”

Theoretical studies on structures and nonlinear optical properties of alkali doped electrides B12N12-M (M = Li, Na, K)

“…Li and coworkers demonstrated that the molecules with loosely bound excess electrons (such as electride and alkalide molecules) exhibited large NLO response. In 2004, two theoretical papers have been reported, indicating that the hydrogen fluoride trimer anion ((FH) 2 {e} (HF)) and the water trimer anion ((H 2 O) 3 {e}) with excess electron exhibited significantly large static first hyperpolarizabilities ( β 0 ) . For instance, the β 0 value was found to be 1.72 × 10 7 au for (H 2 O) 3 {e} anion, which was dramatically larger than that of (H 2 O) 3 (only 35 au) and (H 2 O) 3 F – (only 46 au) .…”

Can Fluorinated Molecular Cages Be Utilized as Building Blocks of Hyperhalogens?

“…gens" M(N 5 ) k + 1 (M = Li, Be, B). [48] It is expected that these species could lead to the synthesis of new superoxidizing agents. Up to now,t he ligands of superhalogens/hyperhalogens have evolved from conventional halogen atoms [24][25][26][27][28][29][30][31][32][33][34] into linear groups (such as CN, SCN, and BO 2 ) [35][36][37][40][41][42][43][44][45] and then into planar groups (such as NO 3 ,V O 3 ,a nd N 5 ).…”

“…Up to now,t he ligands of superhalogens/hyperhalogens have evolved from conventional halogen atoms [24][25][26][27][28][29][30][31][32][33][34] into linear groups (such as CN, SCN, and BO 2 ) [35][36][37][40][41][42][43][44][45] and then into planar groups (such as NO 3 ,V O 3 ,a nd N 5 ). [39,42,48] Therefore, an interesting question emerges:c an such speciesb ec onstructed by using molecular cages as ligands?T oa nswer this question, the polyhedral fluorocarbon cages became the focus of our attention.A st hese molecularc ages have as ufficient interiora ttractive potential, they can serve as the electron hole. Recently, it was reported that an excesse lectron can be trapped inside fluorinated fullerenes, such as C 60 F 60 and C 20 F 20 , [49] to form the molecular-solvated electrons e@C 20 F 20 and e@C 60 F 60 .…”

“…The electron affinities of hyperhalogens can even surpass those of their superhalogen ligands. A multitude of hyperhalogens have been reported since 2010, such as Au(BO 2 ) 2 , Cu(BO 2 ) 2 , Na(BO 2 ) 2 , Al(BO 2 ) 4 , Ag(BO 2 ) 2 , and Al(BF 4 ) 4 , as well as the “magnetic hyperhalogens” Mn(BO 2 ) n and Fe(BO 2 ) n ( n= 3, 4), and “aromatic hyperhalogens” M(N 5 ) k +1 (M=Li, Be, B) . It is expected that these species could lead to the synthesis of new superoxidizing agents.…”