Efficient synthesis of new 17-, 18-, 19- and 20-membered N2O2-donor macrocycles by NaBH4 reduction and metal picrate extraction studies

Abstract

Four new N2O2-donor macrocycles mDo4R, mDo5R, mDo6R, mDo7R (mDo4R = 1,5-diaza-2,4:7,8:15,16- tribenzo-9,14-dioxa-cycloheptadecane, mDo5R = 1,5-diaza-2,4:7,8:16,17-tribenzo-9,15-dioxa-cyclooctadecane, mDo6R = 1,5-diaza-2,4:7,8:17,18-tribenzo-9,16-dioxa-cyclononadecane; mDo7R = 1,5-diaza-2,4:7,8:18,19-tribenzo-9,17-dioxa-cycloeicosane) were prepared by NaBH4 reduction of appropriate macrocyclic Schiff bases in high yields. The compounds were characterized by means of FT-IR and NMR spectroscopy and elemental analysis. The crystal and molecular structure was determined for mDo5R and mDo7R. The molecular structure of mDo5R indicate large deviation from planarity, relatively large inner macrocyclic hole size (1.542–3.048 A) and exodentante orientation of one nitrogen atom (N2) due to presence of intramolecular N–H⋯O hydrogen bond. In mDo7R both nitrogen atoms are exodentante and involved in intramolecular N–H⋯O hydrogen bond. The mDo7R molecules are quite planar with small values of puckering amplitude (1.329(2) A, 1.355(2) A and 1.433(2) A). In the crystal structure of both compounds, molecules are primarily linked by weak C–H⋯π, C–H⋯N and C–H⋯O interactions. The metal cation extractability was determined for all compounds by UV–Vis spectrophotometry and all of compounds show affinity towards extraction of iron (III) and mercury (II) cations. Synthesis and characterisation of secondary amine macrocycles derived from macrocyclic Schiff base analouges and metal picrate extraction studies