Synthesis and characterization of a range of antimony(I/III) N,N'-bis(2,6-diisopropylphenyl)formamidinate complexes

Formamidinatoantimony(I/III) complexes have been successfully synthesized as monomers or dimers in the solid state featuring a variety of coordination geometries and have also been comprehensively characterized. The antimony(I) formamidinate complex bis[μ-N,N'-bis(2,6-diisopropylphenyl)formamidinato]diantimony(I)(2 Sb-Sb) tetrahydrofuran heptasolvate, [Sb₂(C₂₅H₃₅N₂)₂]·7C₄H₈O or [Sb₂(DippForm)₂]·7THF, (1), was obtained by a metathesis reaction between sodium bis(trimethylsilyl)amide [NaN(SiMe₃)₂] and N,N'-bis(2,6-diisopropylphenyl)formamidine (DippFormH), followed by SbCl₃. A range of trivalent haloformamidinatoantimony(III) complexes, namely, bis[N,N'-bis(2,6-diisopropylphenyl)formamidinato]chloridoantimony(III), [Sb(C₂₅H₃₅N₂)₂Cl] or [Sb(DippForm)₂Cl], (2), bis[N,N'-bis(2,6-diisopropylphenyl)formamidinato]bromidoantimony(III), [SbBr(C₂₅H₃₅N₂)₂] or [SbBr(DippForm)₂], (3), bis[N,N'-bis(2,6-diisopropylphenyl)formamidinato]iodidoantimony(III), [Sb(C₂₅H₃₅N₂)₂I] or [Sb(DippForm)₂I], (4), [N,N'-bis(2,6-diisopropylphenyl)formamidinato]dibromidoantimony(III), [SbBr₂(C₂₅H₃₅N₂)] or [SbBr₂(DippForm)], (5), and [N,N'-bis(2,6-diisopropylphenyl)formamidinato]diiodidoantimony(III), [Sb(C₂₅H₃₅N₂)I₂] or [Sb(DippForm)I₂], (6), were also synthesized by adding DippFormH and MN(SiMe₃)₂ (M = Li or Na) to the corresponding antimony halides SbX₃ (X = Cl, Br or I) in differing ratios. The complexes were all stable to rearrangement.

How Many Pnicogen Bonds can be Formed to a Central Atom Simultaneously?

A central ZF₃ molecule (Z = P, As, Sb, Bi) is allowed to interact with a number of nucleophiles exemplified by NCH, NH₃, and NC^– anion. The Z···N pnicogen bond (ZB) to a single base grows stronger for heavier Z atom: P < A < Sb < Bi and follows the NCH < NH₃ < NC^– order for the three bases. The maximum number of ZBs depends on both the nature of the base and pnicogen atom. PF₃ and AsF₃ can pnicogen bond with only a single CN^–; SbF₃ and BiF₃ can interact with two anions but only weakly. The weak NCH nucleophile can engage in a maximum of two ZBs, while three ZBs occur for NH₃. The latter NH₃ maximum can be extended to four ZBs but only for BiF₃. The fourth ZB is somewhat longer and weaker than the others, and the entire (H₃N)₄···BiF₃ complex relies partially on secondary interactions for its stability.

Antimony speciation in the environment: Recent advances in understanding the biogeochemical processes and ecological effects

Antimony (Sb) is a toxic metalloid, and its pollution has become a global environmental problem as a result of its extensive use and corresponding Sb-mining activities. The toxicity and mobility of Sb strongly depend on its chemical speciation. In this review, we summarize the current knowledge on the biogeochemical processes (including emission, distribution, speciation, redox, metabolism and toxicity) that trigger the mobilization and transformation of Sb from pollution sources to the surrounding environment. Natural phenomena such as weathering, biological activity and volcanic activity, together with anthropogenic inputs, are responsible for the emission of Sb into the environment. Sb emitted in the environment can adsorb and undergo redox reactions on organic or inorganic environmental media, thus changing its existing form and exerting toxic effects on the ecosystem. This review is based on a careful and systematic collection of the latest papers during 2010-2017 and our research results, and it illustrates the fate and ecological effects of Sb in the environment.

DNA cleavage, antimicrobial studies and a DFT-based QSAR study of new antimony(III) complexes as glutathione reductase inhibitor

New antimony(III) complexes, [Sb(2-aminopyridine)2Cl3] (1a), [Sb(2-aminopyridine)2Br3] (1b), [Sb(5-methyl-2-aminopyridine)2Cl3] (2a), [Sb(5-methyl-2-aminopyridine)2Br3] (2b), [Sb(2-aminopyrimidine)2Cl3] (3a), [Sb(2-aminopyrimidine)2Br3] (3b), [Sb(4,6-dimethoxy-2-aminopyrimidine)2Cl3] (4a), [Sb(4,6-dimethoxy-2-aminopyrimidine)2Br3] (4b), [Sb(2-amino-1,3,5-triazine)2Cl3] (5a), [Sb(2-amino-1,3,5-triazine)2Br3] (5b), [Sb(2-guanidinobenzimidazole) Cl3] (6a), [Sb(2-guanidinobenzimidazole)Br3] (6b) [Sb(2- benzyl-2-thiopseudeourea)2Cl3] (7a) and [Sb(2- benzyl-2-thiopseudeourea)2Br3] (7b) were synthesized. Their structures were characterized by elemental analysis, molecular conductivity, FT-IR, (1)H NMR, LC-MS techniques. Glutathione reductase inhibitor activity, antimicrobial activity and DNA cleavage studies of the complexes were determined. The geometrical structures of the complexes were optimized by DFT/B3LYP method with LANL2DZ as basis set. Calculation results indicated that the equilibrium geometries of all complexes have square pyramidal shape. About 350 molecular descriptors (constitutional, topological, geometrical, electrostatic and quantum chemical parameters) of the complexes were calculated by DFT/B3LYP/LANL2DZ method with CODESSA software. Calculated molecular parameters were correlated to glutathione reductase inhibitory activity values (pIC50) of all complexes by Best Multi-Linear Regression (BMLR) method. Obtained two-parameter QSAR equation shows that increase in "maximum partial charge for a H atom" and decrease in HOMO-LUMO gap would be favorable for the glutathione reductase inhibitory activity.