Reaction of mercury(II) diiodide with triphenyl selenophosphorane-Se (1:1 mole ratio) in acetone followed by recrystallisation of the product from chloroform formed crystals of stoichiometry HgI₂(Ph₃PSe)(1). Compound1 exists as a centrosymmetric homobimetallic dimer, Hg(Μ-I)I(Ph₃PSe)₂, as monoclinic crystals of space group P2₁/n. The dimer comprises two Μ₂-iodo atoms that form unequal Hg-I bonds 2.8230(10), 3.1135(9) å and two equal terminal Hg-I bonds 2.6524(10) å. The Se atom of Ph₃PSe forms terminal Hg-Se bond 2.5914(11)å and thus the geometry about each Hg centre is distorted tetrahedral and the range of tetrahedral bond angles is 92.97(2) to 130.85(3)‡, the largest being that of Se(1)-Hg(1)-I(1) and the shortest, I(2)-Hg(1)-I(2)‡. Hg-Hg and I-I separations of 4.0930(11)å and 4.3097(15)å are more than the sums of their respective van der Waal radii 3.00 å and 4.24 å.

In the present study, the dialdehyde carboxymethyl cellulose (DCMC) was cross-linked covalently to gelatin via the Schiff base reaction to form a three-dimensional hydrogel (DCMC-cl-G). The crosslinking degree of DCMC and gelatin was estimated to be 50.31 ± 2.65. The maximum swelling capacityof the hydrogel in aqueous medium was around 74 g/g at pH 10.0 and 37^°C with equilibrium swelling attained in three hours and the compressive strength of the hydrogel was found to be 55 ± 0.76 kPa at 60% strain. The biodegradation studies confirmed 82.67% degradation of the hydrogel sample within a period oftwelve weeks. Further, the hydrogel was evaluated as a bio adsorbent for the removal of hazardous dyes, namely Rhodamine B (RhB) and Methyl Violet (MV) from water due to its decent swelling capacity and good mechanical strength. The maximum percentage of RhB and MV removed from the respective dye solutionsusing DCMC-cl-G hydrogel was 96.5% and 90% at pH 6.0, respectively. Both dyes followed Langmuir adsorption isotherm, which considers monolayer adsorption of adsorbate over adsorbent, with a pseudosecond-order kinetic model.