Dynamic Covalent Chemistry Approach toward 18-Membered P4N2 Macrocycles and Their Nickel(II) Complexes.

A dynamic covalent chemistry approach was used for the stereoselective synthesis of 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecanes via condensation reaction of 1,4-bis(organylphosphino)butane, formaldehyde, and primary amines. The obtained 18-membered P4N2 macrocycles were isolated in pure form as meso- (RPSPSPRP) or rac- (RPRPRPRP/SPSPSPSP) isomers. The structural features of the individual stereoisomers were revealed by NMR spectroscopy and X-ray structure analysis. All P4N2 macrocycles form square-planar nickel(II) complexes with the RPSPSPRP isomer only, in which the orientation of the lone pairs of electrons at phosphorus favors this coordination mode, independent of the initial configuration of the ligand, indicating the ability of the 18-membered P4N2 macrocycles to stereoisomerize in the course of the complexation.

Nanoscale isoindigo-carriers: self-assembly and tunable properties.

Over the last decade isoindigo derivatives have attracted much attention due to their high potential in pharmacy and in the chemistry of materials. In addition, isoindigo derivatives can be modified to form supramolecular structures with tunable morphologies for the use in drug delivery. Amphiphilic long-chain dialkylated isoindigos have the ability to form stable solid nanoparticles via a simple nanoprecipitation technique. Their self-assembly was investigated using tensiometry, dynamic light scattering, spectrophotometry, and fluorometry. The critical association concentrations and aggregate sizes were measured. The hydrophilic-lipophilic balance of alkylated isoindigo derivatives strongly influences aggregate morphology. In the case of short-chain dialkylated isoindigo derivatives, supramolecular polymers of 200 to 700 nm were formed. For long-chain dialkylated isoindigo derivatives, micellar aggregates of 100 to 200 nm were observed. Using micellar surfactant water-soluble forms of monosubstituted 1-hexadecylisoindigo as well as 1,1'-dimethylisoindigo were prepared for the first time. The formation of mixed micellar structures of different types in micellar anionic surfactant solutions (sodium dodecyl sulfate) was determined. These findings are of practical importance and are of potential interest for the design of drug delivery systems and new nanomaterials.

Isatin derivatives in reactions with phosphorus(III-V) compounds.

In this review we generalize and analyze information about reactions between isatin and three-, four-, and five-coordinate phosphorus compounds, published between 1966 and 2014.