Molecular orientation and structure in mixed-stack charge transfer (CT) films of 2-octadecyl-7,7,8,8-tetracyanoquinodimethane (octadecyl-TCNQ) doped by 5,10-dimethyl-5,10-dihydrophenazine ((Me)(2)P) have been investigated by using ultraviolet-visible-near-infrared (UV-vis-NIR) and infrared (IR) spectroscopies and X-ray diffraction. The degree of charge transfer (rho) was determined to be 0.5 by a shift of a b(1u) C=N stretching band of the TCNQ chromophore, suggesting that the complex is close to the neutral-ionic boundary. An X-ray diffraction pattern indicates that the CT films consist of a highly ordered multilayered structure in which donor ((Me)(2)P) and acceptor (octadecyl-TCNQ) molecules are periodically arranged. The d value was calculated to be 3.3 nm, implying that each layer of the CT films comprises bimolecular layers. Comparison of IR intensities of b(1u), b(2u), and a(g) C=N stretching bands of the acceptor (A) and a totally symmetric band at 1255 cm(-1) of the donor (D) between the transmission and reflectance absorption (RA) IR spectra indicates that the chromophores of D and A are almost perpendicular to the substrate surface with their long molecular axes being nearly parallel to the surface normal in the one-layer mixed-stack CT films. The hydrocarbon chain of octadecyl-TCNQ was evaluated to lie on the substrate. In the multilayer CT films the D and A chromophoric planes seem to be slightly tilted with respect to the substrate surface.