Dr Ankur Rastogi
@opju.ac.in
Associate Professor, Department of Chemistry
OP Jindal University, Raigarh
RESEARCH INTERESTS
Macrocyclic Chemistry
Scopus Publications
Scopus Publications
Ankur Rastogi and Ram Nayan
Informa UK Limited
Syntheses of copper(II) complexes of 20-membered and 15-membered aza macrocycles 1,3,6,8,11,13,16,18-octaaza-2,7,12,17-tetrachlorocycloeicosane (OTCE, [20]-N8) and 1,3,6,8, 11,13-hexaazacyclopentadecane (HCPD, [15]-N6) involving metal template condensation between 1,2-diaminoethane, trichloromethane and dichloromethane, respectively, are reported. Formulation of [Cu4(OTCE)(H2O)8]Cl8 and [Cu3(HCPD)(H2O)6]Cl6 · 2H2O and the ligand hydrochlorides OTCE · 8HCl and HCPD · 6HCl are supported by elemental analyses, conductivity measurements, and spectral studies. For a comparative cavity size effect on the stability constant, potentiometric measurements on the copper complexes of the generated macrocycles [15]-N6 and [20]-N8 and the structurally related larger macrocycle 1,3,6,8,11,13,16,18,21,23-decaaza-2,2,7,7,12,12,17,17,22,22-decachlorocyclopentacosane (DDCP, [25]-N10, prepared recently) have been performed in aqueous solution at 25°C (μ = 0.1 M KNO3). Very high stability constants obtained for reaction Cu2+ + A ⇌ CuA2+ (A = ligand, log K = 20.51 and 25.87, respectively, for OTCE and DDCP systems) are a reflection on the folding of the ligand to provide a small cavity suitable for fitting of the copper ion. Further, a high equilibrium constant value for CuA2+ + Cu2+ ⇌ Cu2A4+ (OTCE system, log K = 14.59) or Cu2A4+ + Cu2+ ⇌ Cu3A6+ (DDCP system, log K = 16.69) is due to suitable fitting of two and three copper ions in the 20-membered and 25-membered ring cavity of OTCE and DDCP, respectively.