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A novel potassium complex, [K2L2(H2O)MeOH]n (1), was prepared by reacting KOH and a substituted tetrazolyl ligand LH (LH = 1-[5-(2-hydroxyphenyl)-2H-tetrazol-2-yl]-2-methyl-2-propanol). The prepared complex was characterized by infrared spectroscopy and mass analysis and its solid-state structure was determined to be a high dimensional coordination polymer by X-ray crystallography. The synthesized potassium coordination polymer 1 was used as a catalyst for the cycloaddition of CO2 to propylene oxide and is the first potassium coordination polymer to be used for this purpose. The prepared catalyst provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activity despite the heterogeneous reaction condition.

A dual signaling reaction-based probe derived from a hybrid coumarin-benzopyrylium dye was developed for Hg2+ signaling. The probe exhibited selective colorimetric Hg2+ signaling via the Hg2+-induced thiosemicarbazide-oxadiazole transformation. Interference from Cu2+ ions was successfully circumvented using a citrate buffer as a masking agent. The detection limit for Hg2+ ions was found to be 1.88 × 10–7 M. Practical application to Hg2+ detection in simulated wastewater was realized using a typical smartphone as a stand-alone data capture and data processing device.

A novel Ag + -selective reaction-based probe based on an acetylthiourea derivative of 2-(2-hydroxyphenyl)benzothiazole dye was investigated. The designed probe showed pronounced off-on type fluorescence signaling behavior towards Ag + ions via Ag + -induced desulfurization of acetylthiourea to acetylurea. The signaling was superior to the analogous thioamide-to-amide conversion in terms of both speed and signaling contrast. Interference from thiophilic Hg 2+ ions was effectively suppressed using the chelating agent EDTA as a masking agent. The practical application of the system to the detection of Ag + in simulated wastewater with a detection limit of 0.76 μM using a smartphone as an easy-to-use data capturing and processing device was successfully demonstrated.

We herein report the development of a simple structured reaction-based probe for the fluorescence signaling of Hg 2+ ions using a dithiane derivative of an excited-state intramolecular proton transfer (ESIPT) dye. The designed probe exhibited prominent fluorescence signaling behavior towards Hg 2+ ions by the deprotection of its dithiane function to an aldehyde in an aqueous acetonitrile solution. The interfering response of Cu 2+ ions was efficiently removed using citrate as both a masking agent and a buffer. Thus, the use of a citrate buffer allowed exclusive Hg 2+ -selective signaling to be obtained in the presence of common environmentally relevant transition metal ions. Signaling of the Hg 2+ ions was complete within 15 min after sample preparation, and a detection limit of 2.0 × 10 −7 M was estimated. As a practical application of the designed probe, the detection of Hg 2+ ions in simulated wastewater was tested using a smartphone as a portable signal-capturing device.

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co(III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr2en = (N,N′-bis(pyridoxylideneiminato)ethylene) and pyr2cy = (N,N′-bis(pyridoxylideneiminato)cyclohexane)) and Co(OAc)2 and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr2en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts.