CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

kcal/mol less stable than V-A. It is obtained from an initial guess where two water
molecules forming two SHB and one WHB arrangements is added opposite to the H-
bonded network of structure III-A. Conformers V-C and V-D are having at least two
DHB arrangements. Structure V-E has five symmetrical DHB arrangements keeping the
angle between the successive O-I-I planes as 72 o . Conformer V-F having comparable
stability with structure V-E has four DHB and one axial SHB arrangements. The least
stable structure (~19 kcal/mol less stable compared to V-A), V-G has three symmetrical
DHB and two axial SHB arrangements.
Seven minimum energy structures displayed in Fig. 2.1-VI(A-G) are obtained for
the hexa-hydrate cluster, I •− 2 .6H 2 O. The most stable structure, VI-A has five SHB and
five WHB arrangements. Structure VI-G, having no WHB arrangement is the least stable
conformer (~22 kcal/mol less stable compared to V-A). It is interesting to mention that
structure VI-B, having exactly the same number of WHB and SHB arrangements as of
VI-A is 0.33 kcal/mol less stable than VI-A. Both structures contained one H-bonded
water cyclic tetramer. Structure VI-C, where two I atoms are in between two H-bonded
water trimer networks, is less stable than the structure VI-A by ~1.3 kcal/mol though it
has more number of inter water H-bonds. Four H 2 O units form a hydrogen bonded
tetramer network in case of structure VI-D. Remaining two H 2 O units are linked to the
solute atoms by symmetrical DHB arrangement and at a distance to have no interaction
with each other or with any other H 2 O units. Structure VI-E, having six SHB, four WHB
arrangements but no DHB arrangement is 4.14 kcal/mol less stable than VI-A. Structure
VI-F has one H 2 O with a symmetrical DHB, five SHB and four WHB arrangements. The
least stable structure, VI-G has four symmetrical DHB and two SHB from the both sides
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