Third-order nonlinear optical properties of a π-conjugated biradical molecule investigated by third-harmonic generation spectroscopy

Disease activity–guided rituximab therapy in rheumatoid arthritis: The effects of re‐treatment in initial nonresponders versus initial responders

“…The validity of this structure–property relationship has been computationally confirmed using various open‐shell singlet models and real compounds including hydrogen atom chains,6, 14, 18 p ‐quinodimethane model,14 diphenalenyl diradicaloids,19, 20 graphene nanoflakes,21–23 and transition metal compounds 24, 25. These results have been also supported by recent experimental data on two‐photon absorption26 and third harmonic generation,27 and they have stimulated other investigations on linear and NLO properties28–39 of multiradical compounds as well as their vibrational signatures 40, 41. In previous studies,20, 42, 43 spin‐unrestricted hybrid density functional theory (UDFT) calculations have shown that supermolecular and supramolecular multiradical systems composed of phenalenyl units are promising NLO systems, because their properties can be controlled by adjusting the architectures, the diradical characters, and the charge states.…”

Third‐Order Nonlinear Optical Properties of One‐Dimensional Quinoidal Oligothiophene Derivatives Involving Phenoxyl Groups

“…From this result, the γ values of open‐shell singlet molecules can be enhanced by 1) tuning y to be in the intermediate region to increase f γ ( y , r K ), and 2) increasing the effective diradical distance R . On the basis of these strategies, third‐order NLO properties have been evaluated and measured for several singlet diradical compounds with intermediate y . For example, very strong two‐photon absorptions (TPAs) of thermally stable s ‐indaceno[1,2,3‐ cd ;5,6,7‐ c ′ d ′]diphenalene (IDPL) and dicyclopenta[ b ; g ]naphthalene[1,2,3‐ cd ;6,7,8‐ c ′ d ′]diphenalene (NDPL), with intermediate y , were observed experimentally .…”

“…From this result, the g values of open-shell singlet molecules can be enhanced by 1) tuning y to be in the intermediate region to increase f g (y, r K ), and 2) increasing the effective diradical distance R. [6][7][8][9][10][11][12] On the basis of these strategies, third-order NLO properties have been evaluated and measured for several singlet diradical compounds with intermediate y. [13][14][15][16][17][18][19] For example, very strong twophoton absorptions (TPAs) of thermally stable s-indaceno[1,2,3cd;5,6,7-c'd']diphenalene (IDPL) and dicyclopenta[b;g]naphthalene[1,2,3-cd;6,7,8-c'd']diphenalene( NDPL), with intermediate y, were observed experimentally. [13] The recent development of synthetic techniques has achieveds uch thermally stable open-The diradical characters (y)a nd third-order nonlinear optical (NLO) properties of open-shell quinoidal oligothiophene derivatives with phenoxyl groups, and the corresponding reduced (hydrogenated)-state oligomers, are investigated by using the broken-symmetryd ensity functional theory method.…”

Finite‐field method with unbiased polarizable continuum model for evaluation of the second hyperpolarizability of an open‐shell singlet molecule in solvents

“…This design principle is thus easily understandable and can be interpreted based on various conventional chemical concepts like resonance structures and aromaticity, so that a variety of chemical modifications are expected for tuning diradical characters. Recently, this design strategy was experimentally verified for several organic compounds …”