Attachment of 1,5,9-triazacyclododecane and β-cyclodextrin to poly(ethylenimine) in proximity by site-directed functionalization

A novel methodology for the site-directed introduction of a functional group in the vicinity of beta-cyclodextrin (CD) on the backbone of branched poly(ethylenimine) (PEI) is developed. Site-directed or random attachment of 1,5,9-triazacyclododecane (TC) to CD-containing PEI followed by acetylation of the primary and secondary amines of the polymer backbone produced [TC-CD](AcPEI)-Ac-SD or [TC-CD](Ran) AcPEI, respectively. By the addition of Ni(II), Cu(II), or Zn(II) ion, [M(II)TC-CD](SD) AcPEI or [M(II)TC-CD](AcPEI)-Ac-Ran was obtained. The formation constant for the complexation of a hydrophobic ester revealed that the TC portion was indeed positioned in the vicinity of the CD cavity in [M(II)TC-CD](SD) AcPEI. Compared with [M(II)TC-CD](Ran) AcPEI, [M(II)TC-CD]SDAcPEI appears to exert an extra stabilization effect (-Delta Delta G degrees = 1.0-1.3 kcal/mol) on the complexed ester by hydrogen bonding between the metal-bound water of the polymer and the carbonyl group of the ester. (C) 1998 Academic Press.