Zinc coordination polymers containing isomeric forms of p-(thiazolyl)benzoic acid: blue-emitting materials with a solvatochromic response to water

4 years ago

Zinc coordination polymers containing isomeric forms of p-(thiazolyl)benzoic acid: blue-emitting materials with a solvatochromic response to water

Lapo Luconi, Samuele Staderini, Andrea Rossin, Giuliano Giambastiani, Philipp Muller, Giulia Tuci, Franziska Eichler, Alexander Eychmüller, Stefan Kaskel

Two coordination polymers of assorted dimensionality (1D, 2D) have been prepared, namely [Zn3(L2Th)4(OH)2 ∙ 2(HL2Th)]n (1) and [Zn(L5Th)(OAc)]n (2), starting from Zn(II) salts and the isomeric forms of the organic linker p-(thiazolyl)benzoic acid: p-(2-thiazolyl)benzoic acid (HL2Th) and p-(5 thiazolyl)benzoic acid (HL5Th). The isomers have been prepared ad hoc following straightforward Pd-catalysed C−C coupling reaction protocols. In 1, the deprotonated ligand is coordinated through its carboxylate group only, with dangling thiazole groups. The -COO- units are bridging adjacent metal centers, thus creating a 1D chain. The structure of 2 is instead made of Zn2(carboxylate)4 "paddle wheel" dimers as the constituting inorganic node. The resulting final assembly is two-dimensional (2D). The luminescent properties of both polymers have been analyzed in the solid state; they are featured by ligand-centered emissions at lambda = 434 nm (1) and 427 nm (2), respectively. The theoretical analysis of the ligands electronic features and related molecular orbitals reveals that the observed transitions are mainly of p - p* nature, involving p orbitals delocalized on both aromatic cycles. A significant (reversible) blue shift of the emission maximum of ca. 60 nm from the visible to the UV region has been observed for 1 when suspended in water.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/ejic.201700830