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Synthetic, Optical and Theoretical Study of Alternating Ethylenedioxythiophene–Pyridine Oligomers: Evolution from Planar Conjugated to Helicoidal Structure towards a Chiral Configuration
Author(s) -
Chevallier Floris,
Charlot Marina,
Mongin Florence,
Champagne Benoît,
Franz Edith,
Clays Koen,
BlanchardDesce Mireille
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201601057
Subject(s) - chromophore , hyperpolarizability , conjugated system , solvatochromism , crystallography , materials science , cyanine , chemistry , absorption (acoustics) , fluorescence , photochemistry , polymer , organic chemistry , polarizability , optics , molecule , physics , composite material
A series of alternating 3,4‐ethylenedioxythiophene–alkynylpyridine oligomers (DA) n with increased solubility are synthesized and their photophysical properties and nonlinear optical properties are investigated. Their quadratic polarizabilities are determined from hyper‐Rayleigh scattering experiments to obtain information on their conformations in solution. These chromophores, based on the alternation of electron‐rich (D) and electron‐deficient (A) moieties, exhibit optical properties that arise from the combination of dipolar and helicoidal features in the (DA) n homologue series where n =1–4. The transition from dipolar conjugated planar structures ( n =1, 2) to helicoidal structures ( n =3, 4) is clearly evidenced by results from symmetry‐sensitive second‐order nonlinear optical experiments. This suggests an approach towards highly efficient chiral chromophores for second‐order nonlinear optics. Interestingly, this structural evolution also has significant impact on the photophysical properties: both absorption and fluorescence emission show bathochromic and hyperchromic shifts with increasing number of repeating units in the dipolar planar derivatives ( n =1–2) but show saturation effects in the helicoidal structures ( n =2–4). In addition, the helicoidal structures show sizeable two‐photon absorption at 700–750 nm (40–100 GM) for compounds lacking either electron‐donating or electron‐withdrawing substituents.