Structural, electronic, optoelectronics, and linear and nonlinear optical properties of C30H18 and C30H9K9 are comparatively studied from first-principles calculations. Dipole moment, average polarizability, first molecular polarizability, molar refractivity, electron affinities, first ionization energies, work function, Eg, electric susceptibility, refractive index, dielectric constant, and magnitude of the displacement vector were computed. Adiabatic and vertical electron affinity and ionization potential and quasi-particle correction to Eg were determined. Total electronic energy and Eg of C30H9K9 are about 2.71-3.84 eV smaller than those of C30H18. Because of electron correlations, Eg decreases about 0.14-0.57 eV for C30H18 and by 0.3-0.84 eV for C30H9K9. The , chi, eta, and beta mol C30H9K9 are larger than their corresponding values of C30H18. Our results for C30H18 are in excellent agreement with theory. Results suggest that these molecules have potential applications as semiconductor components, linear and nonlinear optical materials, photoactive materials in optoelectronic devices, and possible building blocks for molecular electronics and photonic devices.