The quadratic hyperpolarizability (beta) of 4-(dimethylamino-4'-stilbazole) tungsten pentacarbonyl (W(CO)(5)DAS) organometallic chromophore has been studied by DFT/TDDFT methods. The intrinsical mechanism for the second-order response has been ascribed to the contribution from metal-to-ligand charge transfer. The consideration of the solvent effect quantitatively improves the consistency of the calculated data with the experimental data, and switches the beta(vec) sign. The beta(vec) value is remarkably sensitive to the polarized solvent and even exhibits the different mechanisms for the second-order response in gas and solution phases. The possibilities of using this intriguing effect in the perspective of a molecular switch device are evaluated. (C) 2009 Elsevier B. V. All rights reserved.