Thiosemicarbazones continue to attract the interest of researchers as potential anticancer drugs. For example, 3-aminopyridine-2-carboxaldehyde thiosemicarbazone, or triapine, is the most well-known representative of this class of compounds that has entered multiple phase I and II clinical trials. Two new triapine derivatives HL¹ and HL² were prepared by condensation reactions of 2-pyridinamidrazone and S-methylisothiosemicarbazidium chloride with 3-N-(tert-butyloxycarbonyl) amino-pyridine-2-carboxaldehyde, followed by a Boc-deprotection procedure. Subsequent reaction of HL¹ and HL² with CuCl₂·2H₂O in 1:1 molar ratio in methanol produced the complexes [Cu^II(HL¹)Cl₂]·H₂O (1·H₂O) and [Cu^II(HL²)Cl₂] (2). The reaction of HL² with Fe(NO₃)₃∙9H₂O in 2:1 molar ratio in the presence of triethylamine afforded the complex [Fe^III(L²)₂]NO₃∙0.75H₂O (3∙0.75H₂O), in which the isothiosemicarbazone acts as a tridentate monoanionic ligand. The crystal structures of HL¹, HL² and metal complexes 1 and 2 were determined by single crystal X-ray diffraction. The UV-Vis and EPR spectroelectrochemical measurements revealed that complexes 1 and 2 underwent irreversible reduction of Cu(II) with subsequent ligand release, while 3 showed an almost reversible electrochemical reduction in dimethyl sulfoxide (DMSO). Aqueous solution behaviour of HL¹ and 1, as well as of HL² and its complex 2, was monitored as well. Complexes 1−3 were tested against ovarian carcinoma cells, as well as noncancerous embryonic kidney cells, in comparison to respective free ligands, triapine and cisplatin. While the free ligands HL¹ and HL² were devoid of antiproliferative activity, their respective metal complexes showed remarkable antiproliferative activity in a micromolar concentration range. The activity was not related to the inhibition of ribonucleotide reductase (RNR) R2 protein, but rather to cancer cell homeostasis disturbance—leading to the disruption of cancer cell signalling.

The spectral characteristics of monosubstituted derivatives of 2,2′-bithiophene (1-BT) with simple carbonyl substituents, including –COCF₃ (trifluoroacetyl, 2-BTCF), –COCH₂CN (oxopropanenitrile, 3-BTCN) and –COCH₃ (acetyl, 4-BTCE), and the more complex 5′-((9H-fluoren-9-ylidene)methyl)-3-methyl, 5-methyl carboxylate (5-BTFL) were investigated. Absorption and fluorescence spectra and fluorescence lifetimes were measured in solvents with various polarities and compared with those in polymer matrices (polystyrene, PS; polymethyl methacrylate, PMMA; and polyvinyl chloride, PVC). Although the parent, 1-BT, absorbed near 300 nm and exhibited no or weak fluorescence, the substitution of 1-BT with simple substituents at position 5 resulted in a bathochromic shift of approximately 50 nm or more in absorption and distinct fluorescence above 400 nm. The largest shift in absorption and fluorescence was observed for the complex 5-BTFL with fluorene as a substituent for 1-BT. The most intense fluorescence was observed for the derivative 2-BTCF with trifluoroacetyl as a substituent in the polar PVC matrix. The lifetimes of fluorescence of all substituted 2,2′-bithiophenes were in the range from 0.3 to 3 ns. The polymer matrices increased the intensity of fluorescence to some extent and prolonged the lifetime of the 2,2′-bithiophene derivatives. The reasons for the variation in the fluorescence intensity resulting from the substitution of the parent dimer are discussed.

A modification of biphenylyltetrazole moiety of Losartan (A) by 3-(2-heteroaryl)-pyrazolotetrazole (B) is described. Ketone semicarbazones react with two moles of phosphorus oxychloride-dimethylformamide with the formation of 3-substituted pyrazol-4-carbaldehydes. The transformations of 3-substituted pyrazole-4- carboxaldehydes to 3-substituted pyrazole-4-nitriles were carried out by reaction of hydroxylamine in DMFA. The prepared cyano pyrazoles were converted to tetrazoles by heating with trimethylsilylazide and dibuthyltinoxide in toluene.

The convenient and multigram synthesis of a linear benzo[b]dithiophene (BDT) structure is proposed (dimethyl 3,7-diamino-4,8-bis((2-methoxy-2-oxoethyl)thio)benzo[1,2-b:4,5-b’]dithiophene-2,6-dicarboxylate). The starting materials are commercially available 2,3,5,6-tetrachloroterephthalonitrile and methyl 2-mercaptoacetate, which undergo aromatic substitution, followed by a cyclization reaction in basic conditions to form suitable BDT for potential optoelectronic applications.

The synthesis of 4-(1H-tetrazol-5-yl)-2-(p-tolyl)quinoline 4 as a possible modification of the biphenyltetrazole substructure of losartan 1 is described. The transformation of 2-(p-tolyl)quinoline-4-carbonitrile 3 to the corresponding tetrazole 4 was carried out by the reaction of trimethysilyl azide and dibutyltin oxide as a catalyst in refluxing toluene. The title compound (4) was characterized by IR, ¹H NMR, ¹³C NMR, and HRMS.