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제117회 대한화학회 학술발표회, 총회 및 기기전시회 Reversal of Hückel (anti)aromaticity in the lowest triplet states of hexaphyrins and spectroscopic evidence for Baird’s rule

2016년 3월 23일 15시 39분 28초
KCS2.O-2 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
목 10시 : 38분
한국다우케미칼 우수논문상 수상자 구두발표
저자 및
성영모, 윤민철, 임종민, 김동호*
연세대학교 화학과, Korea

The reversal of (anti)aromaticity in a molecule’s triplet excited state compared with its closed-shell singlet ground state is known as Baird’s rule and has attracted the interest of synthetic, physical organic chemists and theorists because of the potential to modulate the fundamental properties of highly conjugated molecules. Here we show that two closely related bis-rhodium hexaphyrins (R26H and R28H) containing [26] and [28]π-electron peripheries, respectively, exhibit properties consistent with Baird’s rule. In the ground state, R26H exhibits a sharp Soret-like band and distinct Q-like bands characteristic of an aromatic porphyrinoid, whereas R28H exhibits a broad absorption spectrum without Q-like bands, which is typical of an antiaromatic porphyrinoid. In contrast, the T–T absorption of R26H is broad, weak and featureless, whereas that of R28H displays an intense and sharp Soret-like band. These spectral signatures, in combination with quantum chemical calculations, are in line with qualitative expectations based on Baird’s rule.