Structure of N-5-Anilino-pentadien-(2,4)-ylidenaniliniumperchlorate,C17H17N2O4Cl

M_r=348.65, monoclinic, P2₁/n, a=11.088(2), b=17.521(3), c=8.845(2) Å, β=98.87(3)⁰, Z=4, V=1697.8(8) ų, D_x=1.368(1) Mgm⁻³, μ(MoKα)=0.256 mm⁻¹, λ(MoKα)=0.71069 Å, T=296 K. Final R=0.040 for 2454 independent reflections excluding those with |F₀|<4σ(|F₀|). Intensities were measured with an automatic diffractometer. The structure belongs to the openchained cyanines. Characteristic for this class of compounds is their nearly ideal polymethinic electron structure with its main geometrical features: equalisation of bond lengths, alternation of bond angles, planarity of the polymethinic chain. All three features are significantly to be observed in the structure. The bond angle alternation determines essentially the shape of the molecules and the molecular packing.