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Conformationally Flexible Bis(9‐fluorenylidene)porphyrin Diradicaloids
Author(s) -
Zhang Hejian,
Phan Hoa,
Herng Tun Seng,
Gopalakrishna Tullimilli Y.,
Zeng Wangdong,
Ding Jun,
Wu Jishan
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201707480
Subject(s) - diradical , protonation , singlet state , porphyrin , chemistry , singlet fission , photochemistry , crystallography , intramolecular force , crystal structure , paramagnetism , triplet state , ion , stereochemistry , molecule , atomic physics , condensed matter physics , physics , organic chemistry , excited state
A stable 5,10‐bis(9‐fluorenylidene)porphyrin (Por‐Fl) diradicaloid was synthesized. It shows a quinoidal, saddle‐shaped geometry in the single crystal but can be thermally populated to a triplet diradical both in solution and in the solid state. Coordination with the Ni 2+ ion (Por‐Fl‐Ni) does not significantly change the contorted conformation but reduces the singlet–triplet gap. Heat‐induced geometric change can explain the observed paramagnetic properties as well as unusual hysteresis in SQUID measurements. On the other hand, protonation (Por‐Fl‐2H + ) dramatically changes the conformation while maintains the closed‐shell electronic structure. Our studies demonstrate how heat, coordination, and protonation affect the geometry, diradical character, and physical properties of conformationally flexible open‐shell singlet diradicaloids.