1D, 2D and 3D Coordination Polymers of Aromatic Carboxylate Tb-III: Structure, Thermolysis Kinetics and Fluorescence

Reactions of TbCl(3 center dot)6H(2)O with aromatic acids, namely, pyridine-2,3-dicarboxylic acid (H(2)pda), isophthalic acid (H(2)ipa) and isonicotinic acid (Hina) gave rise to three new coordination polymers {[Tb(pda)(Hpda)]center dot 3H(2)O}(n) (1), {[KTb(ipa)(2)(H2O)(3)-(mu-H2O)]center dot 2H(2)O}(n) (2) and [Tb(ina)(3)(H2O)(2)](n) (3), respectively. Complex 1 constructed by eight-coordinate Tb-III nodes connected with completely and half-deprotonated pda and Hpda spacers is a novel 3D metal-organic architecture with nanosized hexagonal 1D channels hosting guest water, whereas complex 2 is a 2D heterometal sheet built by completely deprotonated ipa spacers bridging eight-coordinate K-I and nine-coordinate Tb-III. As for 3, deprotonated monoacid ina anions link eight-coordinate Tb-III centres into a 1D doublechain structure. As excited at 320 nm, complexes 1-3 all display a serial of emissions centred at about 486, 545, 582 and 620 nm, which is assigned to the characteristic D-5(4)-> F-7(j) (j = 6; 5; 4; 3) electronic transitions of Tb-III. The overall fluorescence nature of 1-3 is extremely alike, but their fluorescence intensity and lifetime are affected by the architectures. Very interestingly, the fluorescence intensity of 2, especially emitting at 545 nm, is largely enhanced owing to the coordination of alkali metal K-I in the Tb-III-carboxylate network. Furthermore, thermal behaviours of 1-3 under a nitrogen atmosphere as well as the thermolysis nonisothermal kinetics of 2 are researched. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)