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Gradual Fluorination of Ladder‐type Quarterphenyl
Author(s) -
Kobin Björn,
Grubert Lutz,
Mebs Stefan,
Braun Beatrice,
Hecht Stefan
Publication year - 2014
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.201400044
Subject(s) - chemistry , homo/lumo , fluorine , dipole , crystallography , cyclic voltammetry , fluorene , molecular orbital , phenylene , methylene bridge , methylene , quantum yield , molecule , fluorescence , stereochemistry , electrochemistry , organic chemistry , polymer , physics , quantum mechanics , electrode
A series of partially bridge‐fluorinated derivatives of ladder‐type quarterphenyl L4P is reported. Successive introduction of two fluorine atoms each into the two terminal and one central benzylic methylene positions enabled the synthesis of the three symmetrical derivatives L4P‐F 2 , L4P‐F 4 , and L4P‐F 6 . X‐ray diffraction data show that fluorination does not notably affect the molecular structure of the π system; however, molecular packing in the crystalline solid is largely impacted by the introduction of strong dipoles perpendicular to the molecular axis. The effect of substitution with the present electron‐withdrawing fluorine atoms is clearly reflected in significantly lowered (frontier) molecular orbital levels (the LUMO of L4P is at approximately −1.8 to −2.0 eV and shifts to −2.8 eV or lower), as evidenced by lower reduction and higher oxidation potentials in cyclic voltammetry measurements. Furthermore, the influence of fluorination on the optical properties is unexpectedly strong, in particular, with regard to the fluorescence quantum yield. Fluorination in fluorene bridge positions thus provides an interesting alternative tool to tune the electronic and optical properties, as well as self‐assembly behavior, of ladder oligo( para ‐phenylene)s.