Helical self-assembly of optically active phthalocyanine derivatives: effect of Zn-O coordination bond on morphology and handedness of nanostructures.

ABSTRACT

Two optically active phthalocyanine derivatives with eight peripheral chiral (S)-4'-(2-methylbutoxy)biphenyl moieties on the ß-position of the phthalocyanine ring are synthesized. The circular dichroism (CD) spectra show signals in the Q absorption region for both compounds 1 and 2 in chloroform solution, indicating the effective chiral-information transfer from the peripheral chiral (S)-4'-(2-methylbutoxy)biphenyl side chains to the phthalocyanine chromophore at the molecular level. Their self-assembling properties are further investigated by using electronic absorption and Fourier transform infrared spectroscopy, transmission electronic microscopy, scanning electronic microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Experimental results reveal the effect of the metal-coordination bond on molecular packing models in these nanostructures, which in turn results in the self-assembled nanostructures with different morphologies, from nanosheets for 1 to helical nanofibers for 2. In addition, good semiconducting properties of the nanostructures fabricated from phthalocyanine derivatives 1 and 2 are revealed by current-voltage measurements.