Formation of helical J-aggregate of chiral thioether-derivatized phthalocyanine bound by palladium(II) at the toluene/water interface

A chiral thioether-substituted phthalocyanine ((2,3,9,10,16,17,23,24-octakis-1-phenylethylthiophthalocyaninato)magnesium(II) [MgPc(SEtPh)8]) has been synthesized, which can be bound by soft-metal ions such as palladium(II) ion. Aggregates formed from MgPc(SEtPh)8 and Pd(II) in toluene and at the toluene/water interface were characterized by means of UV-vis absorption and circular dichroism (CD) spectrometries using centrifugal liquid-membrane (CLM) cell. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and scanning electron microscope (SEM) were used as complementary techniques. The toluene solution of MgPc(SEtPh)8 had no optical chirality. However, the addition of PdCl2 into the toluene solution of MgPc(SEtPh)8 induced optical chirality, which indicated the formation of a twisted H-type dimer (face-to-face fashion) of MgPc(SEtPh)8 bound by four PdCl2 in the bulk toluene solution. On the other hand, in the toluene/water interface, helical J-aggregate (head-to-tail fashion) of MgPc(SEtPh)8 bound by PdCl2 was formed, in which one J-aggregate unit contained five 1:2 complexes of MgPc(SEtPh)8-Pd(II) on average. On the basis of the experimental results and the exciton theory for optical chirality, a possible mechanism for the chiral aggregation of MgPc(SEtPh)8-Pd(II) complexes at the interface was proposed. In the present study, we demonstrated a novel strategy for the design of helical phthalocyanine aggregates using the liquid/liquid interface as a template.

Aggregation of thioether-substituted subphthalocyanines with palladium(ii) at the toluene-water interface

Novel chloro-subphthalocyaninatoboron()(Subpc) derivatives with six thioether at the 2 and 3 positions of peripheral benzene (Subpc(SR)) such as chloro-[2,3,9,10,16,17-hexakis-ethylthio-subphthalocyaninato]boron()(Subpc(SEt)) and chloro-[2,3,9,10,16,17-hexakis-benzylthio-subphthalocyaninato]boron()(Subpc(SBz)) were synthesized. The interfacial adsorption of Subpc and Subpc(SR), and the interfacial aggregation of Subpc(SR)-Pd() complexes in the toluene-water system have been investigated by means of high-speed stirring (HSS) spectrometry, centrifugal liquid-membrane (CLM) spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Characteristically orientated structures of Subpc(SR) molecules and the aggregates of Subpc(SR)-Pd() complexes at the toluene-water interface have been suggested depending on the structures of Et and Bz at the periphery. The interfacial aggregation was observed only in the presence of palladium(), in which one aggregate unit contained at least seven 1 : 2 complexes of Subpc(SR)-Pd(). Interestingly, the absorption spectra of the interfacial aggregates of Subpc(SEt)-Pd() and Subpc(SBz)-Pd() complexes were very similar to the previously reported spectra of μ-oxo dimer and binuclear molecule of subphthalocyanine, respectively, suggesting the formation of "face-to-face" or H-aggregate for Subpc(SEt)-Pd() and "head-to-tail" or J-aggregate for Subpc(SBz)-Pd(), respectively, at the toluene-water interface.