Crystal structure determination of bis-dimethyl heptamethine cyanine chloride,C11N2H19Cl · 4 H2O

Mr = 286.59, monoclinic superposition structure C 121, Z = 4, a = 15.248(3), b = = 6.942 (3), c = 9.074(1) Å, β = 120.1(1)°, V = 827(1) ų, D_m = 1.13(1) Mg m⁻³, D_x = = 1.15 Mg m⁻³, λ(MoK_α) = 0.71069 Å, μ = 0.243 mm⁻¹, F (000) = 312, T = 296 K, final R = 0.061 for 802 reflections. All hydrogen atoms were located. The structure consists of chloride anions, bis-dimethyl heptamethine cyanine cations and water molecules. The structure of bis-dimethyl heptamethine cyanine chloride is disordered, e.g. there exist partial coincidence operations, leading to more than one stacking mode of the bis-dimethyl heptamethin cyanine chains. The crystal structure consists of rows of molecule along the a-axis. The C C bonds show the bond length compensation, typical of polymethines, towards a partial double bond (mean value 1.38 Å) between formally sp²-hybridized C atoms. The C N bond lengths to the methyl carbon atoms (mean value 1.49 Å) correspond to normal C N single bonds. The valence angles at the C atoms of the heptamethine chain clearly alternate and deviate systematically from 120°. This is also observed in other structures of a similar type. The structure determined by X-ray analysis confirms the chemical results.