Reactions between 4-amino-1,2,4-triazole and nitro-substituted benzaldehydes in acetonitrile under neutral conditions afford stable hemiaminals, seven of which have been structurally and spectroscopically characterized. Two Schiff bases have also been obtained after the addition of hydrochloric acid to the reaction mixture. We describe a correlation between the conformation and configuration of the hemiaminals, and conclude that the formation of these species is determined by the substituents on the phenyl ring, as well as by the presence of 4-amino-1,2,4-triazole.

Under neutral conditions the reactions between 4-amino-1,2,4-triazole and cyano-substituted benzaldehyde derivatives yield stable hemiaminals. Addition of small amounts of acid catalyst promotes further step of dehydration resulting in formation of Schiff bases. Four new hemiaminals and the corresponding imines have been obtained. The molecular stability of the hemiaminal intermediates results from both the 1,2,4-triazole moiety and electron withdrawing substituents on the phenyl ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess stereogenic centres on carbon and nitrogen atoms. The chirality of these centres is strongly correlated with the conformation of the molecules due to heteroatom hyperconjugation effects.

Stable hemiaminals can be obtained in the one-pot reaction between 2-aminopyrimidine and nitrobenzaldehyde derivatives. Ten new hemiaminals have been obtained, six of them in crystal state. The molecular stability of these intermediates results from the presence of both electron-withdrawing nitro groups as substituents on the phenyl ring and pyrimidine ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess a tetrahedral carbon atom constituting a stereogenic centre. As the result of crystallisation in centrosymmetric space groups both enantiomers are present in the crystal structure.

A series of novel ruthenium(II) 2,2′-bipyridyl (bpy) and 1,10-phenanthroline (phen) derivatives containing PTA (1,3,5-triaza-7-phosphaadamantane) or mPTA (N-methyl-1,3,5-triaza-7-phosphaadamantane cation) have been synthesized and fully characterized. Three types of complexes have been obtained, neutral [Ru(N–N)(PTA)₂Cl₂] (1, N–N = bpy and 4, N–N = phen), monocationic [Ru(N–N)(PTA)₃Cl][Cl] (2, N–N = bpy and 5, N–N = phen) and dicationic [Ru(N–N)(mPTA)Cl₂][BF₄]₂ (3, N–N = bpy and 6, N–N = phen). The solid-state structures of four complexes have been determined by single-crystal X-ray diffraction. The cytotoxicity of the complexes has been evaluated in vitro against U266 and RPMI human multiple myeloma cells.

This study presents a simple and energy-efficient self-assembly LAG synthetic method for novel water-soluble copper(I) complexes [Cu(terpy)(PTA)][PF₆] (1) and [Cu(terpy)(PTA)₂][PF₆] (2). They were characterized by FT-IR, ¹H, and ³¹P{¹H} NMR spectroscopy, elemental analysis, and single-crystal/powder X-ray diffraction (for 2). The X-ray analysis of compound 2 indicates a bidentate coordination mode of terpyridine to the metal center. Variable-temperature NMR tests indicate dynamic properties for terpyridine in the case of both compounds, as well as for the PTA ligands in the case of 2. Additionally, compounds 1 and 2 exhibit interesting cytotoxic activity, which was tested on normal human dermal fibroblasts (NHDFs), human lung carcinoma (A549), human breast adenocarcinoma (MCF-7), and human cervix carcinoma (HeLa) established cell lines. In comparison to the other tested compounds, complexes 1 and 2 seem to have significantly lower IC₅₀ values against cancer cells (A549, HeLa, MCF-7), indicating their potential as prospective anticancer agents. Moreover, both compounds show no significant toxicity towards normal skin cells (NHDFs), suggesting a certain selectivity in their action on cancer cells. Cisplatin as a reference compound also exhibited considerable cytotoxicity against cancer cells but with a low level of selectivity, which could lead to unwanted effects on normal cells. Remarkably, compounds 1 and 2 exhibit up to 30 times the cytotoxic activity of cisplatin, with a six-fold lower toxicity to normal cells. They also interact strongly with human serum albumin, suggesting potential therapeutic applications. Overall, these compounds hold significant promise as potential chemotherapeutic agents.