The synthesis, structural, and photophysical properties of a novel family of neutral fac-[Re(N(∧)N)(CO)(3)(L)] complexes, where N(∧)N is either 2,2'-bipyridine or 1,10-phenanthroline and L is a para functionalized 5-aryltetrazolate [namely, 5-phenyltetrazolate (Tph(-)), 4-(tetrazolate-5-yl)benzaldehyde (Tbdz(-)), 5-(4-acetylphenyl)tetrazolate (Tacy(-)), and methyl 4-(tetrazolate-5-yl)benzoate (Tmeb(-))] are reported. The complexes were prepared by direct addition of the corresponding tetrazolate anion to the acetonitrile solvated fac-[Re(N(∧)N)(CO)(3)](+) precursor. NMR data demonstrate that the coordination of the metal fragment is regiospecific at the N2 atom of the tetrazolate ring. These conclusions are also supported by X-ray structural determinations. Photophysical data were obtained in diluted and deaerated dichloromethane solutions displaying broad and structureless profiles with emission maxima ranging from 566 to 578 nm. The absorption profiles indicate the presence of higher energy intraligand (IL) π-π* transitions and lower energies ligand-to-ligand charge transfer (LLCT) and metal-to-ligand charge transfer (MLCT). As the last two transitions are mixed, they are better described as a metal-ligand-to-ligand charge transfer (MLLCT), a result that is also supported by density functional theory (DFT) calculations. The complexes show excited state lifetime values ranging from 102 to 955 ns, with associated quantum yield between 0.012 and 0.099. Compared to the parent neutral chloro or bromo [Re(N(∧)N)(CO)(3)X], the complexes show a slightly improved performance because of the π accepting nature of the tetrazolato ligand. The metal-to-ligand backbonding is in fact depleting the Re center of electron density, thus widening the HOMO-LUMO gap and reducing the non-radiative decay mechanism in accordance with the energy gap law. Finally, the electron-withdrawing or donating nature of the substituent on the phenyltetrazolato ligand allows the fine-tuning of the photophysical properties.
Environmentally friendly, commercially available BiPh3 reacts with heavy alkaline-earth metals (Ae) and bulky trimethylsilylamines to give the corresponding amides [Ae{N(SiMe3)(R)}2(thf)n] (R=SiMe3, 2,4,6-Me3C6H2, 2,6-iPr2C6H3) in good yields, providing proof of concept for a general synthetic method.
Three bis-phenylbismuth sulfonates [Ph(2)Bi(O(3)SR)](∞) (R = p-tolyl 1, mesityl 2 or S-(+)-10-camphoryl 3) have been synthesised and characterised. Their tendency for ligand redistribution in solution, and activity against the bacterium Helicobacter pylori have been investigated. The structures of 2 and 3 have been authenticated by X-ray diffraction crystallography. They are structurally very similar with polymeric helical chain structures composed of four coordinate Bi atoms which bridge between two sulfonate O atoms with near linear O-Bi-O bond angles. The two phenyl rings are cis to one another and trans to the stereochemically active lone pair. Upon dissolution of the pure compounds 1, 2 and 3, a ligand redistribution reaction occurs in which the mono-phenylbismuth bis-sulfonates, the bismuth tris-sulfonates and triphenylbismuth are formed. Two further complexes of general formula [PhBi(O(3)SR)(2)](∞) (where R = p-tolyl 4, and mesityl 5) were thus obtained and their crystal structures determined. The presence of the single sulfonato ligand in compounds 1, 2 and 3 resulted in a dramatic increase in bacteriocidial activity towards H. pylori (MIC values of ≥6.25 μg mL(-1)) relative to BiPh(3) (>64 μg mL(-1)) and the sulfonic acids, which were essentially inactive.
In exploring the formation of heteroleptic bismuth benzoates and their conversion to polynuclear bismuth oxo-clusters through hydrolysis, ortho-nitrobenzoic acid (= LH) was treated with triphenylbismuth under various reaction conditions. The simple 2:1 stoichiometric reaction in ethanol produced four crystalline products; [{BiL 2 (OEt)(EtOH)} 2 ] ¥ (2) and [Ph 2 BiL] ¥ (4) initially crystallized together, while [BiL 3 (H 2 O)] ¥ (1) appeared later from the filtered mother liquor. Compound 2 results from the in situ ethanolysis of [PhBiL 2 ] n (3) and subsequently undergoes hydrolysis to give crystals of the Bi 10 oxo-cluster [Bi 10 O 8 L 14 (EtOH) x .(EtOH) y (H 2 O) z ] ¥ (5). This latter process was confirmed through the formation of the moisture-sensitive compound [PhBiL 2 ] n under solvent-free, inert atmosphere conditions, which on treatment with dry ethanol produced [{BiL 2 (OEt)(EtOH)} 2 ] ¥ (2). Compound 4 was obtained as a single isolable product from the 1:1 reaction of o-(NO 2 )-C 6 H 4 CO 2 H with BiPh 3 in diethyl ether at room temperature. Single-crystal X-ray diffraction studies on four of the five compounds (1, 2, 4, and 5) show them all to be polymeric in the solid state, having distinct coordination modes and methods of polymer formation. Complexes 1, 4, and 2 are carboxylate-bridged (1, 4) or carboxylate-and ethoxide-bridged (2) polymers in which Bi is nine, eight, and five (with additional Bi-π(Ar) interactions) coordinate respectively. In 5, Bi 10 O 8 L 14 cluster units are linked in a pearl necklace motif by bridging carboxylate groups. These oxo-clusters have a distorted rhombic dodecahedral Bi 6 O 8 core with four additional Bi atoms sited above alternate oxygen atoms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.