Can we enhance diradical character using interaction with stoichiometric surfaces of ionic oxides? A theoretical investigation using chemical indices

Abstract

Chemical indices, especially diradical character, are utilised to examine the functions and reactivity of stable radical species. In the present study, we formulated an approximation to estimate chemical indices using...

Diradical Characters of s-Indaceno[1,2,3-cd;5,6,7-c’d’]Diphenalene with and without Interaction with MgO(001)

“…Stabilised diradical states in stable organic radicals, transition metal complexes, and metal clusters are the origin of their unique optical, electrochemical, and catalytic properties [1][2][3][4][5][6]. Diradical character (y), which is defined as the contribution of two-electron excited states, is a key factor in studying singlet diradical states [1,[7][8][9][10][11]. For example, it has been confirmed that the y value is correlated with hyperpolarizability in third-order nonlinear Regular Paper e-J.…”

“…Nanotechnol. 20, 59-67 (2022) | DOI: 10.1380/ejssnt.2022-011 optics [1,10,11], and it can be used for the analysis of covalent bonds because the y value is also correlated with the effective bond order [1,[7][8][9]. Ten years ago, it was proved that the y value can be experimentally estimated, and the equation for the experimental estimation of the y value is as follows:…”

“…In addition, the analysis technique for the diradical state using the results of density functional calculations with a plane-wave basis (DFT/planewave), which is a general calculation method for the electronic states of solid surfaces, is insufficient. Hence, detailed analyses of the diradical state with surface interactions are scarce [9,[19][20][21][22][23]. Although magnetic interactions between radical molecules adsorbed on Au(111) were analysed by molecular orbital calculation, discussions incorporating the effects of the Au band were difficult because the Au models used were the Au 10 clusters because of the high computational cost [16].…”

“…Recently, a scheme was proposed to estimate the y value from the electron density instead of the results of molecular orbital analysis [9,24]. Because the electron density is a standard output of the DFT/plane-wave calculation, the y value can be easily estimated from the calculated results by DFT/plane-wave without any artificial operations, such as orbital (wavefunction) conversion.…”

“…Because the electron density is a standard output of the DFT/plane-wave calculation, the y value can be easily estimated from the calculated results by DFT/plane-wave without any artificial operations, such as orbital (wavefunction) conversion. Using the developed scheme, it has been shown that even interactions with inert surfaces, such as MgO(001) and BaO(001), can enhance the y values of model biradicals [9]. The models used in the previous work were Au 2 biradicals with different atomic distances, and the charge-dipole interaction between the Au atoms and surfaces increased the y values.…”