The structure and spectral properties of a squarylium dye, 2,4-bis[(1-n-butyl-2(1H)-quinolylidene)methyl]-1,3-cyclobutadienediylium-1,3- diolate

Structural and spectral characterizations of the title compound, 2,4-bis[(1-n-butyl-2(1H)-quinolylidene)methyl]-1,3-cyclobutadienediylium-1,3- diolate (BQMS), a prime candidate for a solar energy material, have been carried out. Crystals are monoclinic, P2₁/n with a = 9.586 (2) Å, b = 9.730 (2) Å, c = 13.894 (3) Å, β = 99.77 (9)°, and Z = 2. The structure has been solved by direct methods and refined by using 1078 reflections for which F > 2σ(F) with anisotropic temperature factors on the non-hydrogen atoms to R = 0.098 and R_w = 0.074. Quasi-metallic reflection is observed along both principal directions for the (101) and (001) faces. The transition moment is found to be polarized along the long axis of the molecule.