Giant enhancement of the second hyperpolarizabilities of open-shell singlet polyaromatic diphenalenyl diradicaloids by an external electric field and donor-acceptor substitution

Masayoshi Nakano, Takuya Minami, Kyohei Yoneda, Shabbir Muhammad, Ryohei Kishi, Yasuteru Shigeta, Takashi Kubo, Léa Rougier, Benoit Champagne, Kenji Kamada, Koji Ohta

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Abstract

Switching on an external electric field (F) along the electron correlation direction produces a giant enhancement of the second hyperpolarizability γ in a polyaromatic diradicaloid having intermediate diradical character. This has been evidenced by carrying out spin-unrestricted density functional theory calculations with the LC-UBLYP long-range corrected exchange-correlation functional for the s-indaceno[1,2,3-cd;5,6,7-c′d′]diphenalene (IDPL) diradical compound in comparison to a closed-shell analogue of similar size composed of two pyrene moieties (PY2). For IDPL, the field-induced enhancement ratio is estimated to reach 4 orders of magnitude for an electric field of 0.0077 a.u., whereas it is less than a factor of 2 for PY2. Moreover, an enhancement is also observed by substituting both-end phenalenyl rings of IDPL with donor (NH2)/acceptor (NO2) groups, but this enhancement is limited to about 2 orders of magnitude. These enhancements are associated with a reduction of the diradical character (and therefore an improved thermal stability) as well as with the appearance of substantial type-I contributions to γ.

Original languageEnglish
Pages (from-to)1094-1098
Number of pages5
JournalJournal of Physical Chemistry Letters
Volume2
Issue number9
DOIs
Publication statusPublished - 5 May 2011

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