First synthesis and structural report on selenophen-2-yl containing pnictogens: Biological activities of tris(selenophen-2-yl)stibine

Heteroaryl bismuthines: a novel synthetic concept and metalπ heteroarene interactions

The alkoxide Bi[OCMe₂(2-C₄H₃S)]₃ (1) is formed by the reaction of three equiv. of the alcohol HOCMe₂(2-C₄H₃S) with Bi(O^tBu)₃ and subsequent hydrolysis provides the bismuth oxido cluster [Bi₄O₂{OCMe₂(2-C₄H₃S)}₈] (2). In contrast, the reaction of Bi(O^tBu)₃ and Bi[N(SiMe₃)₂]₃ with the silanols HOSiMe₂(2-C₄H₃X) (X = O, S, Se, and NMe), HOSiMe₂(2-C₄H₂S-5-SiMe₃) and HOSiMe₂(3-C₄H₃S) leads to the formation of tris(heteroaryl)bismuthines Bi(2-C₄H₂X-5-R)₃ [where X = O, R = H (3); X = S, R = H (4); X = S, R = SiMe₃ (5); X = NMe, R = H (6); X = Se, R = H (7)] and Bi(3-C₄H₃S)₃ (8). For the silanols, bismuth-carbon bond formation is observed rather than silanol-alcoholate or silanol-amide exchange. The structures of compounds 1, 2, and 4-7a in the solid state were established by single crystal X-ray diffraction and all compounds except 5 show London dispersion type bismuthπ heteroarene interactions. For the bismuthine Bi(2-C₄H₃Se)₃ (7), two polymorphs were isolated depending on the conditions of crystallization. At 8 °C, polymorph I (7a) crystallizes from an n-hexane solution in the triclinic space group P1[combining macron], whereas polymorph II (7b) crystallizes at 20 °C from a CH₂Cl₂/n-pentane solution in the monoclinic space group P2₁/c. The heteroaryl bismuthines 3 and 4 exhibit 2D network structures as a result of bismuthπ heteroarene interactions, whereas for the pyrrole derivative 6 the dispersion type interactions provide separated dimers.

The role of dispersion type metal⋯π interaction in the enantiotropic phase transition of two polymorphs of tris-(thienyl)bismuthine

Bi(2-C₄H₃S)₃ shows an enantiotropic phase transition that is dominated by London dispersion forces. DFT calculations on model compounds were carried out in order to investigate the competition between Bi⋯S and Bi⋯π heteroarene interaction.

Study of stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the configurational isomers of the selenophene-2-carbaldehyde azine by NMR spectroscopy and MP2-GIAO calculations

In the (1)H and (13)C NMR spectra of selenophene-2-carbaldehyde azine, the (1)H-5, (13)C-3 and (13)C-5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the (1)H-1, (13)C-1, (13)C-2 and (13)C-4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The (15)N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60-65 mg/g) between the (77)Se resonance positions is revealed in the studied azine isomers, the (77)Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the (1)H, (13)C, (15)N and (77)Se shielding constants in the energy-favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions.

Perspectives of antimony compounds in oncology

Antimony, a natural element that has been used as a drug for over more than 100 years, has remarkable therapeutic efficacy in patients with acute promyelocytic leukemia. This review focuses on recent advances in developing antimony anticancer agents with an emphasis on antimony coordination complexes, Sb (III) and Sb (V). These complexes, which include many organometallic complexes, may provide a broader spectrum of antitumoral activity. They were compared with classical platinum anticancer drugs. The review covers the literature data published up to 2007. A number of antimonials with different antitumoral activities are known and have diverse applications, even though little research has been done on their possibilities. It might be feasible to develop more specific and effective inhibitors for phosphatase-targeted, anticancer therapeutics through the screening of sodium stibogluconate (SSG) and potassium antimonyltartrate-related compounds, which are comprised of antimony conjugated to different organic moieties. For example, SSG appears to be a better inhibitor than suramin which is a compound known for its antineoplastic activity against several types of cancers.