Density functional theory (DFT) and time-dependent DFT calculations were carried out to comparatively describe the molecular structures, molecular orbital energy gaps, atomic charges, infrared (IR) and Raman spectra, and UV-vis spectra of PbPc (1), PbPc(alpha-OC2H5)(4) (2), and PbPc(alpha-OC5H11)(4) (3) {Pc2- = dianion of phthalocyanine; [Pc(alpha-OC2H5)(4)](2-) = dianion of 1,8,15,22-tetra-ethoxyphthalocyanine; [Pc(alpha-OC5H11)(4)](2-) = dianion of 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine}. The calculated structural data of compounds I and 3 and the simulated IR and UV-vis spectra of 3 are compared with X-ray crystallography molecular structures and the experimental absorption spectra respectively to verify the performance of the B3LYP method and the LANL2DZ basis set. Substitution of bulky alkoxy groups at the nonperipheral positions of the phthalocyanine ring adds obvious effect to the molecular structure of phthalocyaninato lead compounds by deflecting the isoindole units in the direction that the isoindole units extends and distorting them in the C-4 axis direction due to the steric hindrance. Both the calculated IR and UV-vis absorption spectra of 3 correspond well with the experimental results.