Four new mixed-ligand divalent coordination polymers (CPs) [Cu2­(muco)2­(4-clpy)2] (1), [Cu2­(muco)2­(4-brpy)2] (2), [Zn2­(bdc)2­(4-clpy)2] (3), and [Zn2­(bdc)2­(4-brpy)2] (4) (H2muco = trans,trans-muconic acid or 1,3-butadiene-1,4-dicarbox­ylic acid; H2bdc = 1,4-benzene dicarbox­ylic acid; 4-clpy = 4-chloro­pyridine and 4-brpy = 4-bromo­pyridine) have been synthesized and well characterized by elemental analysis, infrared spectra, single-crystal X-ray diffraction techniques, powder X-ray diffraction patterns, and thermogravimetric analysis. All the compounds 1–4 have a two-dimensional (2D) coordination polymeric sheet structure. Of these, 1 and 2 are isotypical and form a 3D supramolecular aggregation based on type-I halogen–halogen interactions (Cl···Cl or Br···Br) and have an impact on CO2 sorption properties. For the first time, halogen–halogen interactions have been used as a tool in the construction of high-dimensional CPs for sorption studies. However, analogous compounds 3 and 4 are expanded to 3D supramolecular structures based on π···π interactions. These compounds have no halogen–halogen interactions and hence become nonporous toward CO2 sorption. It appears that the halogen–halogen interactions between the 2D sheets are desirable for the uptake of CO2 gas.

A sensitive, rapid, and specific assay has been developed for the simultaneous determination of acetylsalicylic acid and caffeine in commercial tablets based on their natural fluorescence. The mixture of these drugs was resolved by first derivative synchronous fluorimetric technique using two scans. At Deltalambda=106 nm, using first derivative synchronous scanning, only acetylsalicylic acid yields a detectable signal at 316 nm (peak to zero method) which is unaffected by caffeine. At Deltalambda=30 nm, the signal of caffeine at 288 nm (peak to zero method) is not affected by acetylsalicylic acid. The range of application is between 0.021 and 41.62 microg ml(-1) (correlation coefficient, R=0.9995) for acetylsalicylic acid and between 0.4486 and 44.86 microg ml(-1) (correlation coefficient, R=0.99786) for caffeine. The recovery range of 98.40-102% for acetylsalicylic acid and 90-100.5% for caffeine from their synthetic mixture was reported. Overall recovery of both compounds about 97-99% for acetylsalicylic acid and 97-98% for caffeine was obtained from real sample analysis. The detection limits are 0.0013 microg ml(-1) and 0.0306 microg ml(-1) for acetylsalicylic acid and caffeine, respectively. The relative standard deviation (n=10) for 20 microg ml(-1) of acetylsalicylic acid is 2.75% and for 2.2 microg ml(-1)of caffeine is 1.7%.

Two 1D coordination polymers, [Cd(adc)(4-phpy)2(H2O)2]n (1) and [Zn(adc)(4-phpy)2(H2O)2]n, (2) (H2adc = acetylenedicarboxylic acid and 4-phpy = 4-phenylpyridine) of which Cd(ii) shows better device applicability compared to Zn(ii).

14-Membered metal–ligand ring present in a photosensitive 2D coordination polymer, [Zn2(fum)2(4-phpy)4(H2O)2] (H2fum = fumaric acid and 4-phpy = 4-phenyl pyridine) shows aromatic character as evident by the nucleus-independent chemical shifts (NICS) calculation.

A sensitive and selective fluorimetric sensor for the assay of ascorbic acid (AA) using silver nanoparticles as emission reagent was investigated. In this study, silver nanoparticles were prepared based on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. The nanoparticles were water-soluble, stable and had a narrow emission band. They were used as a fluorescence probe for the assay of ascorbic acid on its quenching effect on the emission of silver nanoparticles. The principal reason for quenching is likely to be a complexation between ascorbic acid and silver nanoparticles. The quenching mechanism was established by Stern-Volmer law. Under the optimum conditions, the quenched fluorescence intensity was linear with the concentration of ascorbic acid in the range of 4.1 x 10(-6) to 1.0 x 10(-4) m (r = 0.9985) with a detection limit of 1.0 x 10(-7) m. The RSD for repeatability of the sensor for the assay of ascorbic acid concentration of 3.0 x 10(-5) and 4.0 x 10(-6) m was found to be 1.5 and 1.3%, respectively. The proposed method was applied to the determination of ascorbic acid in vegetables and vitamin C tablets.