Cooperative Anions Binding with Nitrophenyl Thiourea Derivative

Summary Two new nitrophenyl urea derivatives 1 and 2 weresynthesized by the simple reaction of 4'-aminobenzo-15-crown-5 ether and 4-nitrophenyl isothiocyanate and 4-nitro-phenyl isotcyanate. Ligand 1 bound with sodium cations andiodide anions simultaneously with positive cooperativity. Adistinct color change was observed when ligand 1 wastreated with anions. Binding properties for ligand 2 wasinvestigated, but a weak positive cooperative binding wasobserved. Experimental Benzo-15-crown-5 nitrothiourea (1). To a solution 0.1 g(0.35 mmol) of 4'-aminobenzo-15-crown-5 ether in 10 mLTHF was added with 0.06g (0.35 mmol) of 4-nitrophenylisothiocyanate and the reaction mixture was stirred for 1hour under the nitrogen atmosphere. The precipitate wasoccurred in reaction mixture. The reaction mixture wascooled and filtered to give 0.12 g (74%) of 1 ; 1 H NMR(CD 3 CN) δ 8.50, 8.45 (two s, 2H, NH), 8.18 and 7.79 (a pairof d, 4H, O 2 NArH, J = 8.5 Hz), 6.95 (m, 3H, ArH withcrown unit), 4.07, 3.79 and 3.63 (three m, 16H, -OCH