Low-symmetry azaanalogues of perhalogenated subphthalocyanine

Abstract

Novel electron-deficient low-symmetry perhalogenated azaanalogues of subphthalocyanine, [Cl2F8N2subPc] and [Cl4F4N4subPc], were prepared by mixed co-cyclotrimerization of tetrafluorophthalonitrile and 5,6-dichloropyrazine-3,4-dicarbonitrile in p-xylene in the presence of BCl3. They were characterized by MALDI mass-spectrometry, UV-VIS, IR, [Formula: see text]C, and [Formula: see text]F NMR spectroscopy, and the molecular structure of [Cl2F8N2subPc] was established by single crystal X-ray diffraction. The spectral-luminescence and redox properties of [Cl2F8N2subPc] and [Cl4F4N4subPc] as well as peculiarities of their electronic structure are compared with the corresponding symmetrically substituted compounds - perfluorosubphthalocyanine, [F[Formula: see text]subPc], and hexachlorotripyrazinosubporphyrazine, [Cl6N6subPc]. Consecutive substitution of one and two tetrafluorobenzene fragments by dichloropyrazine units leads to stabilization of the frontier [Formula: see text]-molecular orbitals and widening of the HOMO–LUMO gap. As a result, electron-affinity of the macrocycle is increased and the first reduction potentials are increasingly shifted in the less negative region from -0.43 V for [F[Formula: see text]subPc] to -0.31 V for [Cl2F8N2subPc], -0.19 V for [Cl4F4N4subPc], and the maxima of the Q-band is shifted hypsochromically from 573 nm to 565 and 553 nm, respectively. Preliminary photoelectrical measurements indicate that novel compounds can be used as acceptor materials in non-fullerene photovoltaic cells.