The crystal growth, space group, Raman and IR spectra of the thiocyanato manganese mercury-N,N-dimethylacetamide (MnHg(SCN)(4)(H2O)(2) (C4H9NO)(2), MMTWD) single crystal are introduced. The experiments show that the characteristic vibrational modes of MMTWD crystal consists of eight frequency regions: 50-300cm(-1), lattice modes; 300-550cm(-1), NCS bending; 550-700 cm(-1), H2O wresting; 700-1200 cm(-1), SCN stretching; 1200-1400 cm(-1), CH3 bending; 1400-1500 cm(-1), OH bending; 1500-1700 cm(-1), CH2 bending or CO stretching; 2000-3400 cm(-1), CN, CH, and OH stretching. Spectra analysis reveals that MMTWD crystal belongs to the two-dimensional layer net structure. The complex network layers are piled up in the c axis direction, and the water and dimethylacetamide (C4H9NO, DMA) molecules occupy the interlayer space. It is the additive and coordinates of water and DMA molecules in the layers that provides the crystal with large interaction force between molecules within a layer, which in turn, induces large nonlinear optical properties and higher environmental stability. (c) 2006 Elsevier B.V. All rights reserved.