Acta Crystallographica Section B

Structural Science

Volume 52, Part 3 (June 1996)

research papers

Acta Cryst. (1996). B52, 500-504 [ doi:10.1107/S0108768195012559 ]

Structure of 1,5-bis(dimethylamino)-1,5-diphenylpentadienylium perchlorate and modelling of pentadienylium salts (cyanine dyes)

J.-P. Declercq, A. Dubourg, C. Payrastre, M.-R. Mazières, Y. Madaule and J.-G. Wolf

Abstract: C₂₁H₂₅N₂⁺.ClO₄^- (orange crystals), M_r = 404.9, orthorhombic; P2₁2₁2₁, a = 7.810 (2), b = 15.007 (3), c = 18.326 (3) Å, V = 2147.8 (7) Å³. Graphite-monochromated Mo K [alpha] source at room temperature; [lambda] = 0.71069 Å, = 0.22 mm^-1, Z = 4; F(000) = 856, D_x = 1.25 g cm^-3, R = 0.057 for 1392 independent data. As for the unsubstituted pentamethinium dyes, the chain lies in an all-trans planar configuration. Molecular modelling calculations reproduce the X-ray structure with good accuracy, even in the case of more crowded pentadienylium cations, i.e. 1,5-bis(dimethylamino)-1,3,5-triphenylpentadienylium perchlorate.