3.1.4 Pentamer and Hexamer:
The number of conformers, including both linear and cyclic forms,
possible for pentamer and hexamer are appreciably high. Here we would
like to reiterate that the goal of this study is not to look for
different possible conformers that could exist, but to investigate how
the geometric and energetic features of CH—O H-bonds modulate with
cluster size and how that modulation influences the cluster formations.
For that purpose, we needed to choose a particular type of linear and
cyclic conformer each for clusters of various sizes. For linear, we
chose all-trans conformer and for cyclic, we chose the ones where all
the free carbonyl groups were pointing in the same direction. Binding
energy of pentamer (TTTT) and hexamer (TTTTT) was found to be-31.7 and
-39.0 kcal mol-1 respectively, provided in Table 1.
The geometries of the two conformers are given in Figure S5. As in the
preceding section, we have named the 5-membered and 6-membered cyclic
clusters as Pentamer1and Hexamer1. The two are having binding energy
-31.9 and -37.9kcal mol-1 respectively. The energetics
have been provided in Table 1, whereas the geometries are being provided
in Figure S5.