CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

To see the effect of hydration on the distribution of the excess electron in iodine
dimer radical anion, I •− 2 , Mulliken atomic spin (a-b) population over different atoms is
calculated in the hydrated cluster, I •− 2 .nH 2 O clusters (n=0-8). It is clearly observed that
the odd electron spin is localized over the two I atoms only. Results suggest that the spin
distribution of the odd electron does not change significantly on successive addition of
solvent H 2 O molecules in I •− 2 .nH 2 O clusters (n=1-8). The nature of σ type hemi bond (2c-
3e) between two I atoms in I •− 2 remains the same even after addition of successive water
molecules. This observation is true for Cl •− 2 .nH 2 O and Br •− 2 .nH 2 O systems too.
2.3.1.2. Structure of X.nH 2 O (X= NO − 3 and CO •− 3 ) Clusters
In the previous section, structures of diatomic anionic systems are discussed. In
this section, structure of hydrated clusters of carbonate radical anion (CO 3•¯ ) and nitrate
anion (NO − 3 ) is reported. To choose a suitable level of theoretical method for geometry
search in these systems, geometrical parameters of mono-, di and tri-hydrated clusters of
NO − 3 and CO 3•¯ are carried out following 30 correlated density functionals (hybrid, pure
and meta generalized gradient approximation density functionals). The caculated
geometrical parameters are compared to that at MP2 theory adopting 6-311++G(d,p)
basis functions. It is observed that Becke’s three parameter non-local exchange (B3) and
Lee-Yang-Parr (LYP) non-local correlation functionals (B3LYP) performs well to
describe these clusters producing geometrical parameters close to MP2 results. Various
possible initial structures of NO 3¯.nH 2 O and CO 3•¯.nH 2 O clusters (n=1-8) are considered
for geometry optimization and a number of minimum energy structures (conformers) are
obtained for each size cluster as expected.
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