The synthesis and physical properties of four series of novel fluorene push−pull compounds (4−7)
of the D−π−A type with intramolecular charge transfer (from 1,3- and 1,2-dithiole and 1,3-selenathiole donor (D) moieties) are described. The nature of the heteroatom (S or Se) in the donor
fragment has no effect on the maxima of intramolecular absorption bands (λICT), whereas a change
of position of the heteroatoms in the dithiole moiety from 1,3 to 1,2 leads to a substantial
bathochromic shift in λICT. Solvatochromism, thermochromism, and negative halochromism in these
compounds are demonstrated. Cyclic voltammograms of 4−7 exhibit two, separate, single-electron
reversible redox waves, the potentials of which (as well as the ICT energies in the molecules) are
quantitatively described by σp
- constants of the substituents in the fluorene ring. Compounds 4−7
exhibit reversible salt formation in sulfuric acid, and for compound 5g in diluted sulfuric acid an
additional absorption in the near-IR region has been observed that we attribute to radical species
formation from the equilibrium [5g-H]+ + 5g ⇄ 5g
•
+
+ [5g-H]•.
Proceeding from fluorene-2,7-disulfonyl dichloride, a number of novel fluorene electron acceptors with sulfonyl substituents have been synthesized. Formation of charge transfer complexes (CTCs) of the synthesized acceptors with anthracene in dichloroethane has been studied by appearance of longwavelength CTC bands in the visible region of electron absorption spectra. The values of equilibrium constants determined for three acceptors (i.e. 18, 22a, 22b) show that the process of CTC formation is affected both by electronic and steric factors. Sensitization of poly-N-(2,3-epoxypropyl)carbazole (PEPC) photoconductivity with compounds 18, 21a and 22a has been studied.
146ChemInform Abstract Hydrolysis of the title compound (I) leads to the substitution of the 5-nitro group in the first step, followed by hydratization of the nitrile group, producing the hydroxy amide (III) or the hydroxy acid (IV). The bislactone (V) is obtained from all the three hydrolysis products by Bayer-Villiger oxidation. (X-ray data of (I)).
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