We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni2+ and Cu2+ ions over other metal cations in the CH3CN/H2O solution. Compounds (E)-4-((2-nitrophenyl)­diazenyl)-N,N-bis­(pyridin-2-ylmethyl)­aniline (A) and (E)-4-((3-nitrophenyl)­diazenyl)-N,N-bis­(pyridin-2-ylmethyl)­aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques. The interaction of sensors with these metal ions induced a new absorption band with a hypsochromic shift to the characteristic signal of the free sensors. A theoretical study via time-dependent density functional theory (TD-DFT) was performed. This method has enabled us to reproduce the hypsochromic shift in the maximum UV–vis absorption band and explain the selective sensing of the ions. For all of the systems studied, the absorption band is characterized by a π → π* transition centered in the ligand. Instead of Ni2+ and Cu2+ ions, the transition is set toward the σ* molecular orbital with a strong contribution of the 3d x 2- y 2 transition (π → 3d x 2- y 2). These absorptions imply a ligand-to-metal charge transfer (LMCT) mechanism that results in the hypsochromic shift in the absorption band of these systems.

Drimys winteri JR et G. Forster var chilensis (DC) A. is a tree native to central and southern Chile. Also it found in part of Argentina. It is abundant in wet swampy localities from sea level to an altitude of 1700 m. This tree is sacred for the Mapuche culture; it is used in folk medicine in such as inflammatory and painful processes. Phytochemical studies have demonstrated that this plant contains mainly sesquiterpenes of the drimane type, flavonoids, essential oils, phytosterols and some lignans. These drimanes have attracted interest because of their antifeedant, plant growth regulation, cytotoxic, antimicrobial and insecticidal properties. The objective of this review is to establish clearly the phytochemistry and biological activity of Drimys winteri JR et G. Forster var chilensis (DC) A. Articles based on other varieties are not considered.

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A theoretical study was performed by means of DFT calculations of [n]paracyclophanes and dioxa[n]paracyclophanes. The geometrical parameters and reactivity indexes were analyzed for chain lengths between 4 and 18 atoms...