Water-stable Cd(ii)/Zn(ii) coordination polymers as recyclable luminescent sensors for detecting hippuric acid in simulated urine for indexing toluene exposure with high selectivity, sensitivity and fast response.

Three novel Cd(ii)/Zn(ii) coordination polymers (CPs), namely [Cd(L)(BPDC)0.5H2O]·0.5H2O (1), [Zn2(L)2(BPDC)]·2H2O (2) and [Cd2(L)(BTC)H2O]·3H2O (3) (L = 4-(tetrazol-5-yl)phenyl-4,2':6',4''-terpyridine, H2BPDC = 4,4'-biphenyldicarboxylic acid, and H3BTC = 1,3,5-benzenetricarboxylic acid), have been successfully synthesized and characterized. CP 1 and CP 2 display new two-dimensional double-layered honeycomb frameworks containing uncoordinated nitrogen atoms from pyridine and tetrazole rings, which can easily form hydrogen bonds with various analytes. CP 3 exhibits a 3D framework also with uncoordinated nitrogen atoms from pyridine and tetrazole rings. The fluorescence explorations indicate that CPs 1-3 exhibit strong blue luminescence and excellent chemical stability under a relatively wide range of pH conditions. It is worth noting that CPs 1-3 can quantitatively detect hippuric acid (HA), which is a metabolite of toluene in human urine, with high selectivity, sensitivity, fast response and relatively low detection limits. Moreover, the sensing mechanism of CPs 1-3 for HA can mainly be ascribed to fluorescence resonance energy transfer (FRET). CPs 1-3 could be ideal candidates as HA sensors in human urine samples for practical applications. Notably, to the best of our knowledge, we report for the first time Cd(ii)/Zn(ii)-based luminescent sensors for detecting HA in simulated urine.

Diverse manganese(II) coordination polymers derived from achiral/chiral imidazolium-carboxylate zwitterions and azide: structure and magnetic properties.

Five Mn(II) coordination polymers containing azide and carboxylate as simultaneous bridges have been derived from different imidazolium-carboxylate zwitterionic ligands: 1-methyl-3-(carboxylatomethyl)imidazolium (L(1)), 1,3-bis(carboxylatomethyl)imidazolium (L(2)), (S,S)-, (R,R)-, and (R,S)-1,3-bis(1-carboxylatoethyl)imidazolium (S,S-L(3), R,R-L(3) and R,S-L(3)). The compounds are formulated as [Mn(L(1))(N3)2] (1), [Mn(L(2))(N3)] (2), [Mn(R,R-L(3))(N3)]·0.5CH3OH (3-R), [Mn(S,S-L(3))(N3)]·0.5CH3OH (3-S), [Mn(R,S-L(3))(N3)] (4). In compound 1, the neutral monocarboxylate zwitterion ligand (L(1)) leads to uniform chains with bis(azide)(carboxylate) bridges. For compounds 2-4, the anionic dicarboxylate zwitterions L(2) and L(3) lead to (azide)bis(carboxylate) bridges, but the overall coordination networks are different. In 2 and 3-S (or 3-R), chains with the (azide)bis(carboxylate) bridges are connected by L(2) and S,S-L(3) (or R,R-L(3)), respectively, to give achiral and chiral 2D coordination networks with different connecting topologies. In compounds 4, which is derived from the mesomeric ligand R,S-L(3), linear trinuclear units with the (azide)bis(carboxylate) bridges are linked by µ-1,3 azides to give 2D layers, and the layers are pillared into a 3D framework by the 1,3-dimethyleneimidazolium tethers. Magnetic analyses suggested that compounds 1-3 behave as 1D antiferromagnetic systems, while 4 shows canted antiferromagnetism with weak ferromagnetic ordering below T(C) = 12.4 K.