First Sphere Coordination Chemistry of Modified Cyclodextrins: The Bis-CoCl₂ and Bis-CuBr₂ Complexes of 6^A,6^B,6^D,6^E-Tetra-O-Nicotinoyl-α-Cyclodextrin

Abstract

Substitution of the primary hydroxyl groups of α-cyclodextrin by nicotinate groups in an ABDE conformation yields a molecule having two pairs of pyridyl ligands. The compound complexes CoCl₂ and CuBr₂ in methanol or acetone to yield 1:2 complexes which are soluble in chloroform. The electronic spectrum of the blue CoCl₂ complex is almost identical to that of Co(Py)₂Cl₂, implying a molecular complex with a tetrahedral geometry. The molecular graphics study of this complex shows the two CoCl₂ groups positioned over and outside of the rim of unoccupied α-cyclodextrin.

Key Words:

• Cobalt
• copper
• nicotinate
• cyclodextrins
• synthesis
• modelling