Synthesis, structure, magnetism, luminescence and DFT analysis of three metal-organic complexes based on 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid.

The three multi-dimensional coordination polymers, [Mn 2 (μ 4 -dttpa)(μ 6 -dttpa)(H 2 O) 2 ] n (1), {[Co(μ 4 -dttpa)(H 2 O) 2 ]·2H 2 O} n (2), and {[Zn 3 (μ 4 -dttpa) 2 (μ 2 -dttpa)(phen) 2 (H 2 O) 2 ]·2H 2 O} n (3) (H 2 dttpa ​= ​2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid; phen ​= ​1,10- phenanthroline), are successfully synthesized and characterized by X-ray single crystal diffraction, powder X-ray diffraction (PXRD), FT-IR spectra, elemental analysis and thermogravimetric analysis. Structurally, complex 1 is a three-dimensional structure with the 3-nodal Schläfli point symbol of {4·63·82} 2 {42·62·82}{62·84}. Complex 2 displays a two-dimensional network with a 6-connected uninodal net. With the point symbol of {4·62} 2 ·{43·63} 2 ·{44·62}{6}, complex 3 shows the two-dimensional stacking pattern. Temperature-dependent magnetic data of complexes 1 and 2 indicate antiferromagnetic behaviors between adjacent metal ions from 2 ​K to 300 ​K. Further magnetic studies show that the best fitting parameters of comple× 1 are obtained using the dinuclear Mn(II) model. From 50K to 300K, complex 2 displays antiferromagnetism over its mononuclear analogue with the zero-field splitting parameter (|D| ​= ​35.2 ​cm−1). The luminescent intensity of complex 3 is much stronger than that of free ligand (H 2 dttpa) and auxiliary ligand (phen). Moreover, the photoluminescence mechanism of complex 3 has been analyzed by theoretical calculation at ωB97XD/6–311++g(2d,p) level with DFT and TDDFT, which reveals that luminescence emission of 3 is attributed to the ligand-to-ligand charge transfer (π∗ phen -π dttpa2-). Compared with the free ligand, the enhancement of the luminescent intensity of compound 3 might occur due to the construction of Zn(II) ion, dttpa2− and phen increases the efficiency of charge transfer between LUMO and HOMO in the solid state. [Display omitted] • The luminescence mechanism of Zinc(II) compound has been elaborated by DFT and TDDFT analysis. • Summary and comparison of dttpa2− complexes in this paper and published in literature. • A new coordination mode μ 2 -(η1)-(η1) of dttpa2− in the solid state is first published. [ABSTRACT FROM AUTHOR]