An efficient method for the synthesis of halo-carbolines has been developed via Pd-catalysed formation of C–N bonds through Csp2-H/N–H activation of 4-methyl-N-[2-(pyridine-3-yl)phenyl] benzenesulfonamide derivatives.
Isothiocyanato and azido coordination induced structural diversity in zinc(II) complexes with Schiff base containing tetrahydrofuran group: synthesis, characterization, crystal structure and fluorescence study † Haridas Mandal, Sukanta Chakrabartty and Debashis Ray * Three new structurally diverse zinc(II) complexes of formula [H 3 O][ZnL 2 ]ClO 4 (1), [Zn 2 (m-L) 2 (NCS) 2 ] (2) and [Zn 3 (m-L) 2 (m-N 3 ) 4 ] n (3) have been synthesized using the same furan-based tridentate ONO-donor Schiff base ligand HL (2-hydroxybenzyl-2-tetrahydrofurylmethyl)imine and characterized by X-ray structural analysis. Complex 1 is mononuclear, whereas 2 is a double phenoxido-bridged dinuclear compound. The novel polymeric compound 3 from azido coordination driven aggregation possesses a very rare 1D structure in which the dinuclear ligand-bound Zn 2 L 2 fragments are bridged by four ligand-free m 1,1 -azido bridging Zn(N 3 ) 4 2À units resulting in a zigzag arrangement of repeating triangular Zn 3 motifs with structural similarity to the P1 nuclease. Solid state mixing and grinding processes were applied for the ligand exchange reaction and core conversion. In mechanochemical solvent free synthetic routes 1 reacts with isothiocyanato and azido ions to provide 2 and 3 in pure form. The ligand HL serves as sensitive fluorescent probe for Zn 2+ , and complex 1 for SCN À and N 3 À ions in MeOH medium. Coordination induced fluorescence enhancement due to intraligand p / p* transition in the presence of Zn 2+ of HL and quenching of emission intensities of 1 with SCN À and N 3 À anions are accounted for by the formation of hitherto unknown complexes [Zn(L)(X)] (where X ¼ ClO 4 À , SCN À and N 3 À ). HL shows chelation-enhanced fluorescence response from strong metal ion coordination and binding of isothiocyanato and azido anions with an appreciable lifetime of the fluorophore signals. Excitation at 380 nm of MeOH solutions of all three complexes in air exhibit excited state life-time spanning from 2.5-4.8 ns.
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