Syntheses, structure variations and luminescent properties of rare earth metal-organic complexes modulated by multifunctional arenesulfonate and N-heterocycle

Self-assembly of 2-hydroxyl-5-carboxylbenzenesulfonic acid (H3L) and rare earth (RE) metal nitrates together with 1,10-phenanthroline (1,10-phen) generates sixteen complexes, namely, [RE(NO3)(H2O)8]·2(H2L)·2H2O (1-RE) (RE = Nd, Sm, Gd, Tb, Dy), [RE(NO3)2(H2O)6]·[RE(H2O)9]·4(H2L)·4H2O (2-RE) (RE = Ho and Y), [La(L)(H2O)3]n·3nH2O (3-La), [Eu2(L)2(1,10-phen)2(H2O)2]n·nH2O (4-Eu), [Tb2(L)2(1,10-phen)3(H2O)2]n·nH2O (5-Tb), [RE(L)(1,10-phen)2]n·nH2O (6-RE) (RE = Dy, Ho and Y), and [RE(L)(1,10-phen)(H2O)2]n (7-RE) (RE = Er, Yb and Lu), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. 1-RE and 2-RE are mononuclear complexes containing different RE(III) hydrates and H2L- counter-anions. In comparison with the room temperature self-assembly, hydrothermal reaction is more suitable for the formation of coordination polymer. The La(III) cations in 3-La are interconnected by the μ3-L3- trianions to form (4,4) layer, while the Eu(III) cations in 4-Eu are joined by two L3- trianions in different μ3 coordination modes into (4,4) layer. Polymer 5-Tb exhibits tubular structure extended by two unique L3- trianions in different μ2 and μ3 coordination modes. Polymers 6-RE and 7-RE present distinct chain structures with the extension of L3- trianions in the same μ2 coordination mode. Such structure evolutions are highly dependent on the diverse coordination modes of L3- trianion and the participation of 1,10-phen. Complexes 1-Nd, 1-Sm, 1-Gd, 2-Y, 3-La and 7-Lu exhibit violet, blue and green emissions from 362 to 502 nm, meanwhile, complexes 1-Dy and 6-Dy, 1-Tb and 5-Tb, as well as 4-Eu exhibit their characteristic green and red emissions. These results indicate that the present multifunctional H3L is a good antenna molecule for sensitizing RE(III) cations luminescence.