10.1016/j.ica.2010.05.009
The study focuses on the synthesis and characterization of five new Ni(II) complexes with aroyl hydrazone ligands derived from 2,6-diacetyl pyridine monooxime. The complexes were found to have a distorted octahedral N4O2 coordination environment around the Ni(II) ion, with the ligands coordinating through the pyridine nitrogen, imino-hydrazone nitrogen, and the deprotonated oxygen of the hydrazone moiety. The uncoordinated iminooxime groups and the orthogonal orientation of the CH3–C@N–OH groups relative to the adjacent pyridine rings were observed. The ligands and their corresponding Ni(II) complexes exhibited luminescence, with the complexes showing a lower quantum yield compared to the free ligands. The study also includes the X-ray crystal structure of the Ni(II) salicyloylhydrazone complex, which revealed details about the molecular structure and hydrogen bonding interactions in the crystal lattice. The research provides insights into the coordination chemistry of aroyl hydrazone ligands and their potential applications in areas such as pharmaceuticals and materials science.
10.1246/cl.1980.131
The research investigates the photochemical substitution of ring hydrogen in pyridinecarboxylic esters by alkyl groups derived from solvent alcohols, aiming to elucidate the multiple pathways involved in this process. The study found that the photoalkylation of pyridinecarboxylic esters occurs via several paths, including alkylation initiated by the excited carbonyl moiety of the ester group and alkylation initiated by the excitation of the π-electronic system of the pyridine ring. Methyl 2-pyridinecarboxylate (1) and methyl 3-pyridinecarboxylate (5) are key compounds used to investigate the photochemical substitution of ring hydrogen by alkyl groups derived from solvent alcohols. Methyl 2-pyridinecarboxylate is used to study the dependence of photoalkylation on the added acid, revealing that alkylation occurs at different positions depending on the presence of acid. In the absence of acid, alkylation occurs at the β-position, while in the presence of sulfuric acid, alkylation occurs exclusively at the γ-position. Methyl 3-pyridinecarboxylate is used to explore the complex acidity dependence of photoalkylation and photoalkoxylation, showing that these processes compete under certain conditions. The study also examines the effects of different solvents (methanol and ethanol) and additives (such as benzene, naphthalene, and anthracene) on the photoreactions, revealing that alkylation and alkoxylation originate from different excited states. The results highlight the roles of these compounds in demonstrating the multiple pathways and complex mechanisms involved in the photoalkylation of pyridinecarboxylic esters.
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