- Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks
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We report the synthesis of five dicarboxylic acid-substituted dipolar molecular rotors for the use as linker molecules in metalorganic frameworks (MOFs). The rotor molecules exhibit very low rotational barriers and decent to very high permanent, charge free dipole moments, as shown by density functional theory calculations on the isolated molecules. Four rotors are fluorescent in the visible region. The linker designs are based on push-pull-substituted phenylene cores with ethynyl spacers as rotational axes, functionalized with carboxylic acid groups for implementation in MOFs. The substituents at the phenylene core are chosen to be small to leave rotational freedom in solids with confined free volumes. The dipole moments are generated by electron-donating substituents (benzo-1,3-dioxole, benzo-1,4-dioxane, or benzo-2,1,3-thiadiazole annelation) and withdrawing substituents (difluoro, or dicyano substitution) at the opposite positions of the central phenylene core. A combination of 1,4-dioxane annelation and dicyano substitution generates a theoretically predicted, very high dipole moment of 10.1 Debye. Moreover, the molecules are sufficiently small to fit into cavities of 10 ?3. Hence, the dipolar rotors should be ideally suited as linkers in MOFs with potential applications as ferroelectric materials and for optical signal processing.
- Hamer, Sebastian,R?hricht, Fynn,Jakoby, Marius,Howard, Ian A.,Zhang, Xianghui,N?ther, Christian,Herges, Rainer
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- Fine electronic state tuning of cobaltadithiolene complexes by substituent groups on the benzene ring
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A series of 3,6- and 4,5-dihalogen-substituted 1,2-benzenedithiol (H2bdt) ligands, (3,6-X12-4,5-X22-1,2-H2bdt) (X2 = H, X1 = F (1a), Cl (1b), Br (1c); X1 = H, X2 = Cl (4)), and their cobalt complexes, [Cp?Co(3,6-X12-4,5-X22-1,2-bdt)] (X2 = H, X1 = F (2a), Cl (2b), Br (2c); X1 = H, X2 = Cl (5)), were synthesized by a modified selective thiolation reaction. The 1,2-diphenyl-substituted cobaltadithiolene complex (2d) was also synthesized. The molecular structures of all cobaltadithiolene complexes were determined by single crystal X-ray diffraction analysis. Compounds 2a, 5 and 12 showed unique packing structures with intermolecular interactions that confirmed them as the first examples of half-sandwich-type metalladithiolene complexes with a Cp? ligand. The effects of the benzene substituent type and position on the metalladithiolene ring were investigated using UV-vis spectroscopy measurements and cyclic voltammetry. The results indicate that substitution of halogen atoms at the 3 and 6 position of the benzene ring had a larger effect on the dithiolene ring than substitution at the 4 and 5 positions.
- Tsukada, Satoru,Kondo, Masataka,Sato, Hironobu,Gunji, Takahiro
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- The basicity gradient-driven migration of iodine: Conferring regioflexibility on the substitution of fluoroarenes
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Six different fluoroarenes were submitted to the same transformations. Direct deprotonation with alkyllithium or lithium dialkylamide as reagents and subsequent carboxylation afforded the acids 1, 6, 11, 16, 18, and 23. If the aryllithium intermediate was trapped with iodine rather than with dry ice, an iodofluoroarene (2, 7, 12, 17, 19, and 24) was formed. This, upon treatment with lithium diisopropylamide, underwent deprotonation and iodine migration. The resulting new aryllithium species was intercepted either by carboxylation, to give the acids 3, 8, 13, 20, and 25, or by neutralization, to produce the iodofluoroarenes 4, 9, 14, 21, and 26. The latter family of compounds was converted into another set of acids 5, 10, 15, 22, and 27 by subsequent treatment with butyllithium or isopropylmagnesium chloride and carbon dioxide. ( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
- Rausis, Thierry,Schlosser, Manfred
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p. 3351 - 3358
(2007/10/03)
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