Synthesis, self-assembly, and semiconducting properties of phenanthroline-fused phthalocyanine derivatives

Abstract

Two novel unsymmetrical phenanthroline-fused phthalocyanine derivatives, namely metal free 2,3,9,10,16,17-hexakis(n-butyloxy)-22,25-diaza(1,10-phenanthrolino)[5,6-c₁]phthalocyanine H₂[Pc(OC₄H₉)₆(dicqn)] (1) and its zinc complex Zn[Pc(OC₄H₉)₆(dicqn)] (2), were designed, synthesized, and characterized by a series of spectroscopic methods in addition to elemental analysis. Their self-assembly properties in CHCl₃–methanol were comparatively investigated by electronic absorption spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. Effective intermolecular π–π interactions between metal free phenanthroline-fused phthalocyanine molecules in a face-to-face manner led to the formation of nanowires in CHCl₃–methanol, whereas the phenanthroline-fused phthalocyaninato zinc complex self-assembles into ribbonlike nanobundles with a head-to-tail arrangement depending mainly on Zn–N coordination bonding with a slipped π-stacking interaction between neighboring phthalocyanine molecules. Nevertheless, the aggregates formed from both compounds, in particular the metal free one, were revealed to show good semiconducting properties with a conductivity as high as 1.0 × 10⁻⁴ S cm⁻¹.