Issue 10, 2010

Ambidextrous optically active copper(ii) phthalocyanine supramolecules induced by peripheral group homochirality

Abstract

Self-assembling features of the disk-shaped copper(II) phthalocyanine (Pc) molecules carrying four enantiopure (S)- and (R)-1-(p-tolyl)ethylaminocarbonyl groups at their peripheral positions, CuPc-(S) and CuPc-(R), were studied. For comparison, an analogous CuPc carrying racemic 1-(p-tolyl)ethylaminocarbonyl groups, CuPc-(RS), was used. From circular dichroism and visible/infrared spectroscopic studies with wide-angle-X-ray diffraction data, CuPc-(S) and CuPc-(R) were shown to generate optically active π−π stacked assemblies formed in less-polar solvents. CuPc-(RS) produced similar assemblies with a loss of optical activity in the less-polar solvents. Plural interactions of Pcπ/Pcπ stacking, quadruple hydrogen bonding, homochiral stereocenters at the peripheral groups, bulky aralkyl entities and weak coordinating nature of copper(II) of the CuPcs were thought to be responsible for the formation of the optically active CuPc assemblies. The solvent effect was evident: less polar chloroform and tetrahydrofuran helped to generate the optically active CuPc assembly while highly polar N,N-dimethylformamide gave a monomeric Pc species due to the loss of Pc–Pc intermolecular hydrogen-bonding interaction. The self-assembling ability of the CuPcs was similar to NiPc analogues carrying the same chiral peripherals reported previously. Atomic force microscope study revealed that by casting dilute chloroform solutions of CuPc-(S), CuPc-(R) and CuPc-(RS) onto mica surface, worm-like supramolecular polymers were observed while the NiPc-(R) analogue provided needle-like supramolecular polymers.

Graphical abstract: Ambidextrous optically active copper(ii) phthalocyanine supramolecules induced by peripheral group homochirality

Supplementary files

Article information

Article type
Paper
Submitted
18 May 2010
Accepted
18 Jun 2010
First published
08 Jul 2010

New J. Chem., 2010,34, 2310-2318

Ambidextrous optically active copper(II) phthalocyanine supramolecules induced by peripheral group homochirality

W. Zhang, A. Ishimaru, H. Onouchi, R. Rai, A. Saxena, A. Ohira, M. Ishikawa, M. Naito and M. Fujiki, New J. Chem., 2010, 34, 2310 DOI: 10.1039/C0NJ00374C

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