Abstract:
Complexation ofN-alkyl derivatives of PMDI with β-CD is probed using a variety of techniques. Although
MALDI-TOF and CV experiments suggested complex formation, it is very evident from UV−vis and NMR experiments that
these complexes are different from regular inclusion complexes. A clear understanding of the structure of the binary complex
PMDI@β-CD could be obtained using ICD and NMR ROESY experiments. ICD signals were negative which suggest that the
PMDI moiety is placed outside of the cavity. ROESY experiments provide support for this contention. When the alkyl group istbutyl or 2-propyl, the CH3
protons exist very close to the inner protons ofβ-CD, but the aromatic proton of PMDI is clearly
outside theβ-CD cavity. Based on these results we proposed a structure for PMDI@β-CD with the PMDI moiety placed at the
narrow rim ofβ-CD and theN-alkyl group projecting into the cavity and designated these as“rim-binding”complexes. Additional
experiments showed thatβ-CD can accommodate a PMDI moiety at the narrow rim and an adamantane moiety in its cavity
simultaneously, resulting in the formation of ternary complexes PMDI⊃β-CD⊂ADA. Structure of the ternary complex was also
probed by ROESY. The ternary complex formation can be utilized for the design of higher order functional materials such as CDbased hydrogels
