Regiodivergent C-H bond arylation of fluorinated 2-aryl-pyridines and-quinolines has been developed. The use of Pd catalyst allows to functionalize the C-H bond of the aryl flanked by two fluorine atoms (most acidic position); while using Ru catalyst, the arylation takes place at the ortho heterocycle position. Both reaction conditions exhibit a good functional group tolerance. The synthetically useful selectivity observed with Pd catalyst was applied to design novel C^N ligands for the preparation of luminescent cationic iridium(III) complexes. The influence of the incorporated aryl group onto the fluorinated phenyl unit and the fluorine position patterns on the photophysical properties is described.

Pd-catalyzed C-H bond arylation applied to 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine (1) and 2-(3,5-difluorophenyl)-5-(trifluoromethyl)pyridine (5) allows the access to two families of Ir(III) complexes, charge-neutral and cationic species. The reaction is regioselective since only the C3-or C4-position of the fluorinated phenyl ring of 1 or 5 is readily functionalized -namely the C-H bond flanked by the two fluorine atoms which is the most acidic -which allows the electronic control of the reactive site. A range of electron-withdrawing (CN, CO 2 Et, C(O)Me) substituents on the aryl group has been incorporated leading to the pro-ligands (Ar-2,4-dFppy; 2, Ar = p-C 6 H 4 -CN; 3, Ar = p-C 6 H 4 -CO 2 Et; 4, Ar = p-C 6 H 4 -C(O)Me; and Ar-3,5-dFppy; 6, Ar = p-C 6 H 4 -CO 2 Et). The unsubstituted complexes F/G-1 and F/G-5 featuring 1 and 5 respectively, as C^N ligands are used as reference complexes. The families of five charge-neutral [Ir(C^N) 2 (N^O)] complexes (C^N is 2-(5-aryl-(4,6-difluorophenyl)-5-(trifluoromethyl)pyridinato (F2-F4), and 2-(4-aryl-(3,5-difluorophenyl)-5-(trifluoromethyl)pyridinato (F5-F6), N^O = 2-picolinate] and five cationic [Ir(C^N) 2 (N^N)]PF 6 complexes [N^N = dmbpy is 4,4'-dimethyl-2,2'-bipyridine](G2-G6) were synthesized and their structural and photophysical properties studied with comparison to the unsubstituted analogues used as reference complexes. The appended aryl group provides large steric bulk as the biaryl fragment is twisted as shown by the X-ray crystal structures of F2, F5, F6, G3 and G5. These latter complexes display a wide variety of different Ir…Ir intermetallic distances in crystals, from 8.150 Å up to 15.034 Å. Moreover, the impact on the emission energy is negligible, as a result of the breaking of the conjugation between the two aryl groups. Charge-neutral complexes [Ir(C^N) 2 (N^O)] (N^O = 2picolinate) show bright luminescence: F2-F4 (λ em = 495-499 nm) are blue-green emitters whereas F5 and F6 (λ em = 537, 544 nm), where the fluorine substituents are located at the C3-and C5-positions, emit in the green region of the visible spectrum. In all cases, a unitary photoluminescence quantum yield is found. The improvement of  might be explained by an increase of the radiative rate constant due to a higher degree of rigidity of these congested molecules, compared to the unsubstituted complex F1. The same trends are observed for the family of complexes G. Complexes G1-G4 exhibit blue photoluminescence, and G5 and G6 leads to a red-shifted emission band, as also found for the related complexes F5 and F6 due to the similar fluorine substitution pattern. Their emission quantum yields are remarkably high for charged complexes in CH 2 Cl 2 solution. These results showed that Pd-catalyzed C-H bond arylation is a valuable synthetic approach for designing efficient emitters with tunable photophysical properties.

No abstract

The title compound, [Ni(C10H8N2)3](C9H5N4O)2·2H2O, crystallizes as a racemic mixture in the monoclinic space group C2/c. In the crystal, the 1,1,3,3-tetracyano-2-ethoxypropenide anions and the water molecules are linked by O—H...N hydrogen bonds, forming chains running along the [010] direction. The bpy ligands of the cation are linked to the chain via C—H...π(cation) interactions involving the CH3 group. The intermolecular interactions were investigated by Hirshfeld surface analysis and two-dimensional fingerprint plots.

No abstract

No abstract