Cyclic oligomers as highly selective catalysts

Mass Spectrometry Reveals Complexing Properties of Modified PNP-Lariat Ether Containing Benzyl Derivative of (S)-Prolinamine

In the investigation presented here the synthesis of new lariat ether derivative obtained from the modification of tetrapyrrolidinyl-PNP-crown ether macrocycle is described. The polyheterotopic molecular coreceptor consisted of the replacement of chlorine atoms with an optically active (S)-(1-benzylpyrrolidin-2-yl) methanamine. The structure was confirmed by using elemental analysis, mass spectrometry, and NMR spectroscopy. This work covers results concerning the complexing properties of the new ligand towards Ag⁺, Cu^2+, Co^2+, Ni²⁺, and Zn²⁺ ions. The formation of non-covalent complexes of 1:1 stoichiometry with the Cu^2+, Co^2+, Ni²⁺, and Zn²⁺ ions have been confirmed by mass spectrometry. Due to the previous work and application possibilities, a large emphasis was put on the investigation of the complexation ability of lariat ether with silver (I) cation to determine stability constants by direct potentiometric method. In this case, the formation of four different forms of complexes AgL, Ag₂L, Ag₃L, and Ag₄L has been proved. The observed unusual binding through the nitrogen atoms from the exocyclic substituents may provide the structural unit to build a new coordination polymers.

Structure-property relationships of a tetrapyrrolidinyl PNP-lariat ether and its complexes with potassium, sodium, and silver cations

Spectral properties of the tetrapyrrolidinyl PNP-lariat ether, L, and its complexes with K+, Na+, and Ag+ were investigated. Crystal structures of L and its complex with potassium iodide [KL]I were determined. Protonation constants of the ligand and formation constants of its complexes with Ag+, K+, and Na+ in aqueous solutions were determined. 1H NMR, 31P NMR, FTIR, and ESIMS spectra as well as potentiometric measurements indicate that complexation of Ag+ involves participation of the polyether oxygen donors and the endocyclic nitrogen atom of the cyclophosphazene ring. On the other hand, for complexation of K+ and Na+, only polyether oxygen atoms are involved. The latter conclusion is confirmed in the solid-state structure of the [KL]I complex.

Stereoselective reduction with NADH model BNAH through chiral induction in cyclodextrins

Stereoselective reductive debromination-cyclopropanation of 2-bromo-1-phenylethylidene-malononitrile and 2-bromo-1-beta-naphthylethylidenemalononitrile by coenzyme NADH model BNAH through chiral induction in cyclodextrins is reported. The matching between substrates and cyclodextrins, the substituent effect, and the effect of cyclodextrin concentration on the optical yields have been investigated.