The 2-isocyanoazulene-gold(I) fragment as a versatile element for organometallic dyes and liquid crystals

Abstract

This manuscript reports the synthesis and liquid crystal behavior of isocyanoazulene gold(I) complexes [AuX (CN-Az)] (Az = azulene; X = halide, perhalophenyl or alkynyl) and [μ-4,4′-C6F4C6F4{Au(CN-Az)}2]. The comparison of the X-ray structures of homologous compounds, reveals that the introduction of a long substituent in the system produces a loss of molecular planarity that induces a decrease in the melting temperatures. The free 2-isocyanoazulene is not a liquid crystal itself, but its gold complexes bearing a C10 hydrocarbon chain display a SmA mesophase, whose formation is driven by nanosegregation between molten chains and aromatic parts. The free isocyanide is strongly colored and displays fluorescence in solution associated with the azulene fragment, which is largely diminished upon coordination to the gold fragment.