Site-selective formation of optically active inclusion complexes of alkoxo-subphthalocyanines with β-cyclodextrin at the toluene/water interface

Several subphthalocyanine derivatives that contain an alkoxo substituent as an axial ligand (RO-Subpc, R = 9-anthracenemethyl, benzyl, phenyl, 3,5-dimethylbenzyl, 3,5-dimethylphenyl, 4-methylbenzyl, and 4-methylphenyl) were synthesized. The formation of inclusion complexes of RO-Subpc with P-CD in DMSO and at the toluene/water interface was investigated by UV/Vis absorption spectro-scopy, induced circular dichroism (ICD), and nuclear magnetic resonance (NMR) measurements. Interfacial tension measurements suggested that PCD adsorbed as a monolayer at the toluene/water interface and probably orientated towards the toluene phase with its primary face. The 1:1 composition of P-CD-RO-Subpc inclusion complexes was confirmed in DMSO and at the toluene/water interface for BzO-Subpc, PhO-Subpc, MeBzO-Subpc, and MePhO-Subpc. A 2:1 inclusion complex of AnO-Subpc formed in DMSO. The observed ICD spectra of beta-CD-RO-Subpc inclusion complexes are discussed with respect to molecular modeling and the simulation based on Tinoco-Kirkwood theory. Interestingly, the ICD spectra of beta-CD-BzO-Subpc and beta-CD center dot MeBzO-Subpc inclusion complexes exhibited a negative sign in DMSO and a positive sign at the toluene/water interface. This reversal of the ICD sign strongly suggests a difference in the structure of the inclusion complexes: P-CD at the interface formed the inclusion complex with its primary face, whereas the secondary face of P-CD bound favorably to RO-Subpc in DMSO.