V. M. Babaev

Supramolecular assemblies of triblock copolymers with hexanuclear molybdenum clusters for sensing antibiotics in aqueous solutions via energy transfer

The work introduces the supramolecular assembly of triblock copolymers, namely (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4), (PPO)8(PEO)22(PPO)8 (10R5) and (PEO)21(PPO)67(PEO)21 (P123) with novel cluster complexes [K(diglyme)(CH3CN)]2[Mo6I14] (1) and [K2(diglyme)(CH3CN)5][Mo6I14] (2) as a route to increase their water solubility. Dynamic light scattering and photophysical measurements reveal the decisive influence of the arrangement of PEO and PPO blocks and of their length on both colloidal and photophysical properties of these solutions. ES-MS data reveal [Mo6I14]2− clusters as the predominant form in aqueous solutions of L64 and P123. The steady state and time resolved luminescence data indicate concentration dependent sensitizing of the Mo-centered luminescence through the energy transfer from difloxacin to [Mo6I14]2− mediated by the ion-pairing. The impact of both arrangement and length of PEO and PPO blocks in the luminescent response of [Mo6I14]2− to difloxacin is discussed. The aqueous solutions of L64 at pH 4 provide the optimal conditions for the sensing of difloxacin through the cluster luminescence.

Nanoparticle-Delivered 2-PAM for Rat Brain Protection against Paraoxon Central Toxicity

Solid lipid nanoparticles (SLNs) are among the most promising nanocarriers to target the blood-brain barrier (BBB) for drug delivery to the central nervous system (CNS). Encapsulation of the acetylcholinesterase reactivator, pralidoxime chloride (2-PAM), in SLNs appears to be a suitable strategy for protection against poisoning by organophosphorus agents (OPs) and postexposure treatment. 2-PAM-loaded SLNs were developed for brain targeting and delivery via intravenous (iv) administration. 2-PAM-SLNs displayed a high 2-PAM encapsulation efficiency (∼90%) and loading capacity (maximum 30.8 ± 1%). Drug-loaded particles had a mean hydrodynamic diameter close to 100 nm and high negative zeta potential (-54 to -15 mV). These properties contribute to improve long-term stability of 2-PAM-SLNs when stored both at room temperature (22 °C) and at 4 °C, as well as to longer circulation time in the bloodstream compared to free 2-PAM. Paraoxon-poisoned rats (2 × LD50) were treated with 2-PAM-loaded SLNs at a dose of 2-PAM of 5 mg/kg. 2-PAM-SLNs reactivated 15% of brain AChE activity. Our results confirm the potential use of SLNs loaded with positively charged oximes as a medical countermeasure both for protection against OPs poisoning and for postexposure treatment.

“Host–guest” binding of a luminescent dinuclear Au(I) complex based on cyclic diphosphine with organic substrates as a reason for luminescence tuneability

This work introduces a luminescent dinuclear Au(I) complex with a cyclic PNNP ligand ((AuCl)2L) as a “host” molecule with two binding sites, “upper” and “lower”. The “upper” binding site is nucleophilic due to two preorganized Au–Cl moieties, while the “lower” one is electrophilic due to positive partial charges of hydrogen atoms of P–CH2–N moieties. The “host–guest” binding is a reason for both solvent- and substrate-induced tuning of the complex luminescence. Organic cations, namely N-methylpyridinium and trimethylammonium, are revealed as substrates able to bind via the “upper” site of the complex. Acetone, diphenylketone, DMSO, DMF and acetonitrile exemplify substrates able to bind with both the binding sites of the complex. The binding via “lower” sites leads to changes in mutual arrangement of pyridyl moieties and P–Au bonds of the complex, which results in a more pronounced effect on the excited state energy relative to the binding via the “upper” site. Substrate-induced tuning of the luminescence is affected by the nature of the solvent due to competitive “host–guest” binding of (AuCl)2L with solvent molecules.

Synthetic glycosides containing two isosteviol fragments functionalized with D-glucopyranose

The synthesis of isosteviol (16-oxo-ent-beyeran-19-oic acid) glycosides in which two isosteviol fragments functionalized with tetra-O-acetyl-D-glucopyranose are linked through a diester spacer is described for the first time.

Macrocyclic derivatives of isosteviol with two tetracyclic diterpenoid skeletons

Reaction of a diester based on 16-hydroxyisosteviol and sebacic acid with ditosylates of ethylene glycol, propane-1,2-diol, and octane-1,8-diol has led to new macrocycles containing two tetracyclic diterpenoid ent-beyerane skeletons.

Electrochemical properties and reactivity of organonickel sigma-complex [NiBr(Mes)(bpy)] (Mes = 2,4,6-trimethylphenyl, bpy = 2,2′-bipyridine)

Electrochemical properties and reactivity of electrochemically activated forms of organonickel sigma-complex [NiBr(Mes)(bpy)] (where Mes = 2,4,6-trimethylphenyl, bpy = 2,2′-bipyridine) were studied. The activation of the organonickel sigma-complex was found to proceed under both electrochemical reduction and oxidation conditions to give coordinatively unsaturated forms of the complex: radical [Ni(Mes)(bpy)]• and cationic complex [Ni(Mes)(bpy)]+, respectively. It was shown experimentally that the active forms of organonickel complex [NiBr(Mes)(bpy)] can react with organic substrates (cyclohexene, octene-1, tetrahydrofuran) and convert nitriles (acetonitrile, acetonitrile-d3, chloroacetonitrile) into corresponding imines containing 2,4,6-trimethylphenyl fragment.

Lariat ethers in the chiral recognition of amino acid esters:electrospray ionization mass spectrometry investigation

The ability of the crown ethers (1–4), containing the ortho- or para- methoxyphenoxy-methyl substituents in their structure, to chiral recognition in reference to amino acid esters has been investigated by electrospray ionization mass spectrometry (ESI-MS). The method allows registering the diastereomeric complexes between the studied crowns as hosts and the protonated alanine, phenylglycine and phenylalanine methyl esters as guests in the gas phase. ESI-MS experiments using isotopically labeled guests provide robust and reproducible results, indicating a moderate degree of chiral discrimination in the series of the studied crown ethers. ESI-MS experiments using achiral amine as a reference yielded the results comparable with the previous method. It has been found that (S)-enantiomers of the crowns bind predominately (S)-enantiomers of the amino acid esters, and vice-versa. It has been shown that the chiral ortho-substituted crown (S)-1 demonstrates the more pronounced values for chiral discrimination as compared with the para-substituted crown (S)-2. This fact indicates the interrelationship between the chiral recognition and the lariat nature of crown 1. Increasing the size of the cavity and the presence of a flat aromatic moiety in crowns 3 and 4 strengthens their complexing ability, simultaneously weakening the enantioselectivity of the complexation.

Open-Chain and Macrocyclic Polyethyleneglycol Esters of the Diterpenoid Isosteviol

Open-chain and macrocyclic derivatives of the diterpenoid isosteviol (16-oxo-ent-beyeran-19-oic acid) in which two isosteviol molecules were connected by polyethyleneglycol spacers were synthesized for the first time.

Synthesis of Macrocyclic Derivatives of the Diterpenoid Isosteviol with Two and Four ent-Beyerane Frameworks

Macrocycles with two or four ent-beyerane diterpenoid frameworks joined by ester spacers with various polymethylene chain lengths (n = 2, 6, 8) were synthesized for the first time from the diterpenoid isosteviol (16-oxo-ent-beyeran-19-oic acid).

Synthesis, structures, and properties of 15-oxoisosteviol thiosemicarbazone and oxime

New nitrogen-containing derivatives of the diterpenoid isosteviol (16-oxo-ent-beyeran-19-oic acid) containing oxo, hydroxyimine, and thiosemicarbazone groups were synthesized. Isosteviol 15-oxo-16-thiosemicarbazone forms a 1: 1 complex with CuII and inhibits the growth of Mycobacterium tuberculosis (H37RV, in vitro) at the minimum inhibitory concentration of 20 μg mL−1.