Syntheses, structures and properties of a series of organic–inorganic complexes based on methylenediisophthalic acid (H4MDIP)

Abstract

Six new inorganic–organic polymers {Mg(H₂MDIP)(H₂O)₄]·3H₂O}_n (1), {Ca₂(MDIP)(H₂O)₄]·CH₃OH·4H₂O}_n (2), {[Sr₂(MDIP)(H₂O)₇]·2H₂O}_n (3), {[Ba(MDIP)_0.5(H₂O)₄]·H₂O}_n (4), {[Mn(H₂MDIP)(H₂O)]₂·H₂O}_n (5) and {[Co(H₂MDIP)(H₂O)]₂·H₂O}_n (6) were obtained by self-assembly of the corresponding metal salts with methylenediisophthalic acid (H₄MDIP), and their structures were determined by single-crystal X-ray diffraction studies. Monodentate coordination mode of H₂MDIP²⁻ in 1 results in a 1D chiral chain (right-handness) with a monoclear magnesium center. Complexes 2–4 have 2D layer networks, and each MDIP⁴⁻ ligand coordinates to Ca(II), Sr(II) or Ba(II) atoms using four carboxylate groups: the chelating-mono coordination mode in 2 leads to a 1D helical chain, yet the chelating-mono and chelating coordination modes lead to binuclear [Sr–O–Sr] and [Ba–O–Ba] units in 3–4. Both 5 and 6 have 2D grid structures with a binuclear [M–O–C–O–M] unit (M = Mn²⁺, Co²⁺). The luminescence properties of 1–4 have been investigated in the solid state at ambient temperature and it was found that the strong emissions vary from blue to yellow–green fluorescence depending on the metal ions. Compound 1 exhibits good second-harmonic generation activity, approximately 1.1 times that of urea.