Water Molecules in Carbon 70, (H 2 O) 3 @C 70

Endohedral fullerene studies are the fascinating one, particularly with Carbon 60 and Carbon 70. Water molecules inside fullerenes alter their cage structure, reorientations make them to play a lot in charge distribution. In this line we are presenting our work on Carbon 70 with three water molecules inside. Ab initio SCF calculations are carried out for the fullerene Carbon 70 and Carbon 70 with three water molecules. Carbon 70 is a rugby ball structure, when three water molecules are added inside it, dissociation of charges takes place. Un-usual flip flop circular hydrogen bond formation takes place inside Carbon 70. The dipole moment of endohedral C 70 with three water molecules has been found to be 0.53 Debye, 0.49 Debye and 0.71 Debye respectively for STO-3G, 3-21G and 6-31G basis sets. Total energies for this molecule are reported in addition to the Hydrogen bond length and bond angles of the three water molecules trapped inside C 70 .


Introduction
Theoretical predictions of buckyball molecules appeared in literature between 1960 and 1970. Carbon 70 was discovered in 1985 by Robert Curl, Harold Kroto and Richard Smalley using laser evaporation of graphite. They found C n clusters (n > 20) of which the most common were C 60 and C 70 . For this discovery they have been awarded Nobel Prize in 1996. Carbon 70 molecule, which is one type of fullerene is a cage like fused ring structure, resembles like a rugby ball. C 70 is made by 25 hexagons and 12 pentagons. Endohedral fullerenes also called as endofullerenes are fullerenes that have additional atoms, ions, clusters enclosed

Results
The structure of fullerene C 70 and the structure of Carbon 70 with three waters molecules inside are shown in Figure 1 and Figure 2 respectively. Optimized geometry calculations are carried out at SCF ab-initio STO-3G, 3-21G and 6-31G basis sets. Total energies of these molecules are given in Table 1 in atomic units.
Optimized C 70 with 3 water molecules at 3-21G basis set is reported in the Figure 2. Cyclic hydrogen bonds involving flipping action inside Carbon 70 with 3 water molecules at 3-21G basis set with bond lengths and oxygen angles is shown in Figure 3. The bond length of one oxygen atom to the hydrogen atom of other water molecule and vice versa is 1.52 Å, 1.53 Å and 1.64 Å and the angle with respect to the oxygen of each water molecule is 57.55˚, 64.96˚ and 57.48˚ respectively.
Structure of C 70 with 3 H2O molecules optimised at 3-21G basis set Cyclic water molecules having anchored and deflected with one hydrogen atom in each molecule, angles formed among water molecules after optimisation at 3-21G basis set are shown in Figure 4. The angles in respect of anchored and deflected hydrogen atom in each water molecule are 49.41˚, 79.65˚ and 50.93˚, 60.67˚, 61.88˚ and 57.46˚ respectively. The angle of water molecule is of 109.82˚, 105.69˚ and 107.15˚.
The optimized structure at 6-31G basis set of C 70 with 3 water molecules reported and the conformation of water molecules with hydrogen bonding in cyclic manner along with their bond lengths and oxygen bond angles are shown in Figure 5, Figure 6(a) and Figure 6(b) respectively. The bond length of one oxygen atom to the hydrogen atom of other water molecule and vice versa is 1.63 Å, 1.63 Å and 1.70 Å and the angle with respect to the oxygen of each water molecule is 57.64˚, 65.85˚ and 56.51˚ respectively.
Structure of C 70 with 3 H2O molecules optimised at 6-31G basis set Cyclic water molecules having anchored and deflected with one hydrogen atom in each molecule and the angles formed among water molecules after op-

Discussion
The pentagons and hexagons of the rugby ball structure of fullerene C 70 as shown Figure 1 are adopted to have the usual bond lengths and bond angles as reported experimentally. Due to the inclusion of water molecules as shown in Figure 2, C 70 structure is slightly modified and the formation of dipole moment is seen. Dipole moment has been found to be 0.53 Debye, 0.49 Debye and 0.71 Debye respectively for STO-3G, 3-21G and 6-31G basis sets. Dipole moment is the indication of conductivity and magnetism. Three water molecules inside C 70 interact with each other through hydrogen bonding. One hydrogen of the water molecule interact with Oxygen of other water molecule respectively through bonding in cyclic, which makes themselves as a cyclic water trimer. Water trimer exhibits ortho metastable configuration inside C 70 , rather para configuration when it is outside the rugby ball [11]. This study is in line with our previous work on circular and linear hydrogen bonds on molecules [ [15]. Fullerenes and Endohedral fullerenes will find a lot of applications in conductivity, magnetism, drug delivary, photovoltics and storing atoms and molecules. It seems to be finding applications in sensing, cosmetics and medicinal fields. This kind of studies will help to achieve the above applications. i.e. 59.90˚, 60.26˚ and 59.84˚. The bond length between the deflected hydrogen atom of one water molecule and the oxygen of the second water molecule, deflected hydrogen of second water molecule and the oxygen of the third water molecule and deflected hydrogen of third water molecule and the oxygen of the first water molecule have been observed respectively as 1.52 Å, 1.53 Å and 1.64 Å as shown in Figure 3(a). The ab-initio calculations of Fullerene C 70 , Water trimer and Water trimer encapsulated fullerene in three different levels of basis sets, STO-3G, 3-21G and 6-31G, using RHF have been taken place and their optimised and the total energy for stabilizing the molecules is presented as shown in the Table 1. Water molecules in the endohedral fullerene adopt an angle is 109.82˚, 105.69˚ and 107.15˚ and their bond length as defined in the Figure 3(b) and Table 2   All the three water molecules are stabilized by interacting with their hydrogens among themselves and also with carbons of fullerenes C 70 . Four hydrogens of two water molecules are interacting with six membered ring of C 70 and two hydrogens of one water molecule is interacting with five membered ring of the C 70 as shown in Figure 8(a). The overall optimized fullerene C 70 structure is related to oval in shape and the diameter of the fullerene alongside of the oval is 8.25 Å and their minimum diameter other than the oval side is 6.98 Å as shown in Figure 8(b). The spatial orientation of atoms (anchored hydrogens, deviated hydrogens and oxygens) in all the three water molecules within C 70 are altogether are in different planes and parallel to each other. The hydrogen atoms and oxygen atoms of all the three water molecules are stabilized by maximally interacting with six membered rings of the fullerene molecule in range of the distance from 2.5 Å to 2.9 Å. Graphical representations of the molecule are referred by Visual Molecular Dynamics software Package [19]. Journal of Biophysical Chemistry  [6]. The bond length between the deflected hydrogen atom of one water molecule and the oxygen of the second water molecule, deflected hydrogen of second water molecule and the oxygen of the third water molecule and deflected hydrogen of third water molecule and the oxygen of the first water molecule have been observed respectively as 1.63 Å, 1.63 Å and 1.70 Å respectively as shown in Figure 6(a). The ab-initio calculations of Fullerene C 70 , Water trimer and Water trimer encapsulated fullerene in three different levels of basis sets, STO-3G, 3-21G and 6-31G, using RHF have been taken place and their optimized and the total energy for stabilizing the molecules is presented as shown in the Table 1. Water molecules in the endohedral fullerene adopt an angle is 112.17˚, 107.34˚ and 109.48˚ and their bond length as defined in Figure 7 and Table 2. All the three water molecules are stabilized by interacting with their hydrogens among themselves and also with carbons of fullerenes C 70 . Four hydrogens of two water molecules are interacting with six membered ring of C 70 and two hydrogens of one water molecule is interacting with partially with both the five and six membered ring of the C 70 as shown in Figure  9(a). The overall optimized fullerene C 70 structure optimized at 631-G is also related to oval in shape and the maximum diameter of the fullerene alongside of the oval is 8.26 Å and their maximum diameter other than the oval side is 6.98 Å as shown in Figure 9(b). The spatial orientation of atoms (i.e. anchored hydrogen, deviated hydrogen and oxygen) in all the three water molecules within C 70 are altogether existing in different planes and parallel to each other. Journal of Biophysical Chemistry Comparison of optimised C 70 with three water molecules at 3-21G and 6-31G basis sets Comparing the endohedral fullerene (H 2 O) 3 @C 70 structure at 3-21G and 6-31G basis sets, it is found that having maximum similarities. In contrary the water molecules adopts their position among themselves are meagerly deflective through their oxygen and hydrogen bonds as show in Figure 10 & Figure 11. There is also a dissimilarity of their bond lengths. The orientations of the water molecules encapsulated in C 60 [5] [6] with comparison of the water molecules encapsulated in C 70 optimized both at 3-21G and 6-31G basis sets are considerably different in their various angles and bond lengths as discussed. The hydrogen and oxygen bond deviations in respect of the water molecules optimized at 3-21G and 6-31G basis set is shown in Figure 10 & Figure 11.
The spacial orientation of atoms (i.e. anchored hydrogen, deviated hydrogen and oxygen) in all the three water molecules within C 70 level are altogether existing in different planes and parallel to each other separately but high probable similarities could be observed among the water molecules at 3-21 G and 6-31 G by measuring the differences as detailed in Table 3.
The length of deviations among bond lengths and angles of all the three water molecules in C 70 is as shown in Figure 12 and in Table 3.

Conclusion
SCF ab initio Calculations on fullerenes C 70 and endohedral fullerene (H 2 O) 3 @ C 70 shows a promising beginning to find out the structural reorientation in equilibrium geometries. Spacial orientations of atoms in water molecules within C 70 show three different planes. Charges need refinements. This result is in line with our previous ab-initio calculation with (H 2 O) 3 @C 60 . The study on seven endofullerene, M@C 60 ), Where M = H2O, Li+, Na+, K+, Be2+, Mg2+, and Ca2+ were also reported [20] and concluded that all of the endofullerenes are more stable than pure C60. Coupled translational and rotational motions of H2 molecules in C 70 and C60 has been reported [21] with the predictions that at most two H2 molecules can stably occupy C 70 and just one can be accommodated by C 60 which are Table 3. Length of deviations in bond length and bond angles of trimer water molecules in C 70 encapsulated at 3-21G and 6-31G basis set.  Figure 10. Orientation of water molecules inside C 70 , Optimised at 3-21G and 6-31G basis sets. Figure. 11. Bond length (Å) and Angle (˚) of water molecules inside C 70 at 3-21G and 6-31G basis sets. Figure 12. Deviations of bond length in Å and bond angle in degrees among three water molecule inside C 70 , optimized at 3-21G basis set and 6-31G basis set. Journal of Biophysical Chemistry in accord with the experimental preparation of (H 2 )n@C 70 (n) 1, 2) 4 and H 2 @C 60 [22] [23]. At the same Experimental value of dipole moment of one water encapsulated fullerene also supports this kind of work, but a lot of experimental work should be carried out for further endeavours. This kind of studies will help endohedral fullerenes to achieve the applications in the field of sensors, super conductivity, medicine, magnetism, storing, photovoltic and drug delivery, etc.