A novel organic-inorganic hybrid material (C 6 H 10 N 2)(Hg 2 Cl 5) 2 .3H 2 O has been prepared under hydrothermal conditions. It is characterized by single crystal X-ray diffraction, thermal analysis and spectroscopy measurements (IR, Raman and NMR). The structural analysis revealed that this material crystallizes in the monoclinic system (C 2/c space group) with the following unit cell parameters a = 19.6830(15) Å, b =18.1870(15) Å, c = 6.8567(6) Å, β = 93.224(3) ° and Z=4. According to the data collected at 150(2) K, the refinement converged to R= 0.0296. The atomic arrangement can be described as an alternation of cationic [C 6 H 10 N 2 ] 2+ .H 2 O and anionic [Hg 2 Cl 5 ]layers along the c axis. In fact, a three-dimensional cohesion, which leads to these peridinium complexes, involves (N-H***Cl) (N-H***O) (O-H***O) and π-π interactions. Furthermore the FT-IR, Raman and NMR-MAS confirm the presence of organic and inorganic entities. Finally, the differential scanning calorimetry revealed several endothermic peaks.