Metal–organic frameworks with oxazoline-containing tripodal ligand: structure changes via reaction medium and metal-to-ligand ratio

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Six new copper(I) complexes [Cu2(L)2(H2O)](ClO4)2 (1), [Cu3(L)2(CH3CN)3(ClO4)3] (2), [Cu2(L)2Cl]ClO4·(9/4)H2O·(3/4)CH3CN (3), [Cu2(L)2(CH3CN)2](ClO4)2·2H2O (4), [Cu2(L)Br2] (5) and [Cu4(L)2Br4]·2CH3CN (6) [L = 1,3,5-tris(2-oxazolinyl)benzene] were prepared by reactions of ligand L with Cu(I) salts. Complexes 1 and 2 obtained by using the same reactants, but different solvents have 1D chain and trinuclear propeller-shaped M3L2 cage-like structures, respectively. While 3 and 4 with 2D (42·62·82)(4·62)(4·62) topological network and M2L2 macrocyclic ring structures were synthesized by addition of CuCl and CuBr, respectively. Complexes 5 and 6 with different structures were isolated by changing the metal-to-ligand ratios. 5 is an infinite 1D chain while 6 is a 3D framework with (4·122)2(42·124) topology. The results suggest that the reaction solvents, counter anions and metal-to-ligand ratios play important roles in the formation of frameworks. The complexes were characterized by X-ray crystallography and electrospray mass spectrometry. Complex 2 shows modest second harmonic generation (SHG) activity.