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Twenty symmetrical and asymmetrical 1,2‐bisazolylethanes have been obtained from azoles and 1,2‐dibromoethane or 1‐chloro‐2‐(pyrazol‐1‐yl)ethane by phase transfer catalysis (PTC). The 1H and 13C nmr properties are reported and the chemical shifts of the ethylene carbon atoms discussed using an additive model.

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In the triclinic polymorph of 2-iodo-4-nitroaniline, C(6)H(5)IN(2)O(2), space group P-1, the molecules are linked by paired N-H...O hydrogen bonds into C(8)[R(2)(2)(6)] chains of rings. These chains are linked into sheets by nitro...I interactions, and the sheets are pairwise linked by aromatic pi-pi-stacking interactions. In the orthorhombic polymorph, space group Pbca, the molecules are linked by single N-H...O hydrogen bonds into spiral C(8) chains; the chains are linked by nitro...O interactions into sheets, each of which is linked to its two immediate neighbours by aromatic pi-pi-stacking interactions, so producing a continuous three-dimensional structure.

Novos derivados do lapachol 2, nor-lapachol 3 e da lausona 4 foram sintetizados através do deslocamento nucleofílico das metoxinaftoquinonas 2a, 3a e 4a pela poliamina (PA) N 1 -Boc-N 5 -Bn-espermidina 1a. Os produtos, 2b, 3b e 4b, respectivamente, foram obtidos em bons rendimentos e caracterizados por métodos espectroscópicos e analíticos. Os ensaios preliminares de inibição das enzimas topoisomerases (topo) I e II-α mostraram-se promissores: todos os compostos (1a 2b, 3b e 4b) inibiram a atividade catalítica da enzima topo II-α na dose de 2 μM. Considerando que somente a PA 1a não inibiu a atividade da enzima na dose de 0,2 μM, as naftoquinonas apresentam-se como fragmentos em potencial para melhorar a atividade de PAs. Nenhum dos compostos inibiu a topo I na dose de 200 μM.Novel derivatives of lapachol 2, nor-lapachol 3 and lawsone 4 have been synthesized by nucleophilic displacement of the methoxynaphthoquinones 2a, 3a and 4a with the polyamine (PA) N 1 -Boc-N 5 -Bn-spermidine 1a. The respective products 2b-4b were obtained in good yields and characterized by spectroscopic and analytical methods. The inhibitory action of these naphthoquinone-PA conjugates on DNA-topoisomerases (topo) I and II-α was evaluated by relaxation assay of supercoiled DNA plasmid. All compounds (1a 2b, 3b and 4b) presented significant inhibition of topo II-α catalytic activity at the 2 μM dose. Considering that only PA 1a did not inhibit the enzyme catalytic activity at the 0.2 μM dose, the appended naphthoquinone moiety acts as a "value added" fragment. Compounds 1a 2b, 3b and 4b did not inhibit the enzyme DNA-topo I at the 200 μM dose.Keywords: spermidine, lapachol, lawsone, nor-lapachol, DNA-topoisomerase II-α IntroductionPolyamines (PAs) spermidine, spermine and putrescine occur in the cells of living organisms where they fulfill an array of physiological roles. 1 Because they are involved in optimum growth and replication of various cell types, and are present in higher concentrations in rapidly proliferating cells 2 they were identified as potential targets for the development of anticancer drugs. Initial efforts were focused on the design and synthesis of selective inhibitors of the PA biosynthetic enzymes however their action was not sufficient to inhibit tumor growth. 3 The discovery that tissues with a high demand of PAs contain active polyamine transporter (PAT) for importing exogenous PAs 4 redirected the focus of interest to the PA uptake system from the cellular environment, and several potent inhibitors became known. 5 Anticancer therapies have tried to use the PAT to convey citotoxic and genotoxic agents to rapidly proliferating cells. 6 440 Cunha et al. J. Braz. Chem. Soc. Currently, the most actively pursued approach is based on tumor growth inhibition by cytotoxic structural analogues of the natural PAs, however the PA transport system also offers the possibility to improve transport and accumulation by tumors of compounds which are tethered to PA structures. One of the recent strategies involved the grafting o...

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Precursors of chelate pyridine-N-heterocyclic carbene (N^C:) ligands with methyl- or benzyl-substituted imidazolylidene fragments were synthesized. They were used to obtain 12 iridium bis-cyclometalated complexes of the type [Ir(C^N)(N^C:)] (C^N = 2-(phenyl)pyridinato-C,N, ppy, 2-(4,6-difluorophenyl)pyridinato-C,N, dfppy). The ancillary N^C: ligands contain different structural modifications. The aim of the work was to analyze the effect that changes in the two types of ligands have on the photophysical and electrochemical properties and also on the behavior of these materials as photosensitizers. The X-ray crystal structures of five complexes were determined. The complexes emitted in the blue-green region. It was expected that the frontier orbitals and thus the photophysical and electrochemical properties would be controlled by the main C^N ligands, and it was demonstrated that the effect of the modifications in the N^C: ligand, especially the presence of a nitro group in the pyridine ring or the interruption of conjugation between the two rings, also affected these properties. The quenching with O and photostability studies were also performed. Density functional theory calculations were used to explain the behavior of some derivatives. The complexes and other previously reported compounds were employed as photosensitizers (PS) in preliminary studies on the production of H from water using [Co(bpy)]Cl (bpy = 2,2'-bipyridine) as catalyst and triethanolamine (TEOA) as the sacrificial reductant. The absence of quenching of the PS with TEOA allowed us to propose an oxidative quenching mechanism.