CATENANDS BUILT ON POLY(ETHYLENIMINE) - ATTACHMENT OF 2 PHENANTHROLINES IN CLOSE PROXIMITY ON THE POLYMER BACKBONE

In an attempt to establish a methodology for introduction of two or mo re functional groups in close proximity to the backbone of synthetic p olymers, two molecules of a 1,10-phenanthroline were preassembled with Cu(I) ion and then cross-linked with poly(ethylenimine) (PEI) to obta in [Cu(I)Phen(2)](PEI)-P-PA. Removal of Cu(I) ion from [Cu(I)Phen(2)]( PEI)-P-PA produced [apoPhen(2)](PEI)-P-PA, whose primary and secondary amines were subsequently acetylated to produce [apoPhen(2)](AcPEI)-Ac -PA. Crosslinkage of each preassembled phenanthroline pair with PEI th rough four-point attachment would produce two interlocking macrocycles linked to each other or two fused entwining macrocycles. The former i s a special class of catenand, whereas the latter is a catenand analog ue. Ionization constants for the phenanthroline moieties and formation constants for the Cu!II) complex were measured for the PEI derivative s. The results indicate that the geometry of two phenanthrolines origi nally assembled by Cu(I) ion is effectively conserved in [apoPhen(2)]( PEI)-P-PA and [apoPhen(2)](AcPEI)-Ac-PA. Stabilization of a phenanthro linium ion by an adjacent phenanthroline as well as unfavorable electr ostatic interaction between two close phenanthrolinium ions are disclo sed by the 10(9.5)-fold difference in ionization constants for two pre assembled phenanthrolines. Analysis of the Cu(II)binding data revealed that the effective molarity of a phenanthroline toward Cu(II) ion bou nd to the other phenanthroline in each phenanthroline pair is 10(6) M. These demonstrate very close proximity between the two phenanthroline s. Preassemblage of organic molecules with a template metal ion follow ed by cross-linkage with a branched polymer can be utilized in design of biomimetic functional molecules including artificial enzymes.