Pyridine-hydrazone-controlled cyanide detection in aqueous media and solid-state: tuning the excited-state intramolecular proton transfer (ESIPT) fluorescence modulated by intramolecular NHBr hydrogen bonding.

A new efficient pyridine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique excited-state intramolecular proton transfer (ESIPT) mechanism. The addition of a Br group to the fluorophore skeleton at the ortho-position of hydrazone generates reference compounds (4b-E and 4c-Z). Interestingly, the potential intramolecular NHBr hydrogen bonding might compete with the anion-induced intermolecular NHA- hydrogen bonding, resulting in dramatic ESIPT suppression. The high emission of probe 4a-E and other control probes in solid-state is also investigated. Moreover, probe 4a-E preloaded on test papers, upon cyanide treatment, shows obvious changes in color which demonstrates that 4a-E is a writable platform. More importantly, it exhibits great potential application for the detection of cyanide in food materials and excellent performance in real-world water samples.

Addition of α-Cyanomethylpyridine to Naphthalimide via Trifluoromethyl-Directed CH Functionalization: Cyanide Sensing in Aqueous Media.

A colorimetric anion sensor based on the activated C-H group is described, and the selective and reusable detection of cyanide using the sensor is demonstrated. The system uses bromine to block isomerization and trifluoromethyl-directed C-H regioselective functionalization for direct C-C bond formation between a fluorophore and 2-(pyridin-2-yl)acetonitrile. Thus, this system provides a new way to develop activated CH-based anion receptors.

A reusable cyanide sensor via activation of C-H group: trifluoromethylcarbinol-directed meta-C-H cyanomethylation of naphthalimide.

A fluorescent and colorimetric anion sensor based on the activated C-H group has been developed, and its reusability and ability to selectively detect cyanides have been demonstrated. The system utilizes trifluoromethylcarbinol-directed C-H regioselective cyanomethylation for direct C-C bond formation between the fluorophore and acetonitrile. The present paper also describes a novel strategy for the enhancement of carbanion stability by a potential intramolecular C[double bond, length as m-dash]OH-C hydrogen bonding system, thus providing a new way to develop activated CH-based anion receptors.

Pyridinium-derived polycationic covalent organic polymers for aromatic C-H bond photocatalytic oxidation.

Using oxygen in the air as the sole oxidant to oxidize hydrocarbons into high value-added compounds is a highly promising synthesis strategy with economic advantages. However, the oxidation of hydrocarbons with molecular oxygen under mild conditions is challenging due to the large C-H bond energy in hydrocarbons. Herein, a metal-free two-dimensional covalent organic polymers (COP) functionalized by photoactive pyridinium units has been developed for heterogeneous photocatalytic oxidation of hydrocarbons. This is the first kind of COPs material that can achieve photocatalytic oxidation of hydrocarbons without any additives or stoichiometric oxidants except for the oxygen in the air.

Improved Effect of Metal Coordination on Molecular Oxygen Activation for Selective Aerobic Photooxidation.

A pyridinium-based complex with environment-friendly and earth-abundant ZnII ion was synthesized and explored as a green catalyst applied in activating molecular oxygen for the simple and efficient photooxidation of alcohols into aldehydes under additive-free and mild conditions. The metal coordination was conducive to promoting the electron transfer efficiency and introducing the heavy-atom effect for the increased generation of ⋅O2 - and 1 O2 . Accordingly, improved photocatalytic performance of this complex compared to its precursor, no matter activity or selectivity, was obtained, facilitating the transformation of alcohols into aldehydes in a sustainable way.