Single crystals of the organometallic nonlinear optical material, diaqua(thiocyanato) manganese(II)mercury(II)IN,N-dimethylacetamide (MMTWD), were grown from aqueous solutions. The morphology of the crystals was indexed. The grown crystals were characterized by elemental analyses, scanning electron microscopy (SEM), Raman and infrared spectroscopy, X-ray powder diffraction (XRPD), thermal analysis and Vis/UV/NIR spectroscopy. The MMTWD crystal exhibits good physicochemical stability at normal temperature and pressure. Its UV transparency cutoff is 360 nm, which is shifted to the violet by 13 nm, as compared with MnHg(SCN)(4) (MMTC). The optical transmission is 55.17% at 404 nm, which is by 27.81 % higher than that of MMTC. (C) 2002 Elsevier Science B.V. All rights reserved.