Abstract: | In this article, diaquatetrakis (thiocyanato) manganese(II) mercury(II)‐N‐methyl‐2‐pyrrolidone, MnHg(SCN)4(H2O)2.2(C3H6CONCH3), (abbreviated as MMTWMP), a new organometallic nonlinear optical crystal material is reported. The structure, optical and thermal characterizations were determined by elemental analysis, infrared and Raman spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, differential scanning calorimetry, special heat, SHG measurements and UV/Vis/NIR optical transmission spectra. It belongs to the tetragonal crystallographic system, with cell parameters: a = 12.1294, c = 8.2238Å, V = 1211.27Å3. Single crystals with dimensions up to 8 × 7 × 5 mm3 have been obtained. The morphology of the crystals was indexed. The MMTWMP 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 44.82% at 404 nm, which is by 17.46% higher than that of MMTC. |