The study was aimed at determining the chemical composition, toxicity effect and field varroacidal efficacy of the essential oil distilled from the leaf of Eucalyptus globulus (Eg) grown in Algeria. Brine shrimp lethality (BSL) assay and bee hives infected by Varroa destructor were used to assess the toxicity and acaricidal effect, respectively. Steam distillation of leaves yielded 0.93 % (v/w) of essential oil (EO). GC/MS Analysis revealed 39 compounds, essentially oxygenated monoterpenes (86.01%). The main constituents of the oil were 1,8-cineole (78.45 %), o-cymene (2.18 %), isopinocarveole (1.74 %), α-pinene (1.69 %), pinocarvone (1.34%) and veridiflorol (1.31%). The BSL assay revealed a highly toxic value of LC50 (67.55 μg/mL). Furthermore, field efficacy testing on bee hives infected with Varroa destructor has confirmed the effectiveness of Eucalyptus globulus essential oil (EgEO) or thymol as varroacidal agents. Moreover, a EgEO + thymol association was more effective than EgEO or thymol alone. Finally, the use of EgEO + thymol may constitute a viable alternative to the thymol-based commercial treatment.

The synthesis and characterization of diaquabis[2-(2-hydroxyethyl)pyridine-κ² N,O)nickel(II) dinitrate, [Ni(C₇H₉NO)₂(H₂O)₂](NO₃)₂, under ambient conditions is reported and compared with catena-poly[[bis[2-(2-hydroxyethyl)pyridine-κ² N,O]copper(II)]-μ-sulfato-κ² O:O′], [Cu(C₇H₉NO)₂(SO₄)] _n [Zeghouan et al. (2016). Private communication (refcode 1481676). CCDC, Cambridge, England]. In the two complexes, the 2-(2-hydroxyethyl)pyridine ligands coordinate the metal ions through the N atom of the pyridine ring and the O atom of the hydroxy group, creating a chelate ring. The Ni^II or Cu^II ion lies on an inversion centre and exhibits a slightly distorted MO₄N₂ octahedral coordination geometry, build up by O and N atoms from two 2-(2-hydroxyethyl)pyridine ligands and two water molecules or two O atoms belonging to sulfate anions. The sulfate anion bridges the Cu^II ions, forming a polymeric chain. The photoluminescence properties of these complexes have been studied on as-synthesized samples and reveal that both compounds display a strong blue-light emission with maxima around 497 nm. From DFT/TDDFT studies, the blue emission appears to be derived from the ligand-to-metal charge-transfer (LMCT) excited state. In addition, the IR spectroscopic properties and thermogravimetric behaviours of both complexes have been investigated.