First-order perturbative approximations to the diatomics-in-molecule (DIM) approach are implemented for studying interactions between the neon atom and chlorine molecule in the X (1) Sigma(g)(+)(0(+)) and B (3) Pi(u)(0(+)) states. Intermolecular DIM perturbation theory (IDIM PT1) [J. Chem. Phys. 101, 9913 (1996)], which accounts for the atomic component of spin-orbit interaction, is compared to the anisotropic model by Naumkin and Knowles [J. Chem. Phys. 103, 3393 (1995)] which is proven to be a first-order approximation to the nonrelativistic DIM approach, An importance of the spin-orbit effects for the ground-state potential energy surface (PES is demonstrated. Semiempirical PESs are used in the accurate quantum calculations on the vibrationally averaged geometry, B<--X vibronic spectra, and vibrational predissociation dynamics of the Ne...Cl-2 van der Waals complex. The IDIM PT1 model is shown to provide good agreement with available experimental data. The effects of interaction potential topology on the spectroscopic and dynamic properties of the complex and the relation of DIM-based PESs to the results of abinitio calculations are discussed.