Nt1310 Unit 9 Final Paper

3.3. Frontier molecular orbital

The electronic structure of the doped fullerene interacting with glycine compared to pure fullerene C20 has been calculated with density functional theory using the B3LYP/6-31G basis set. The molecular orbital theory, the relative chemical reactivity of a molecular system can be estimated using HOMO and LUMO energies and overlaps of molecular orbital [18-20]. The electronic transition from the HOMO to LUMO are mainly derived from the electron density transfer n orbital to p* orbital. The HOMO and LUMO help to derive the chemical reactivity and kinetic stability of the molecule. The energy of the HOMO is directly related to the ionization potential, LUMO energy is related to the electron affinity. The conjugated

Using the Mulliken atomic charges of cation and anion, the fukui function (fk+, fk-), local softness (sk+, sk-) and local electrophilicity indices (ωk+, ωk-). These functions can be condensed to the nuclei by using an atomic charge partitioning scheme, such as Mulliken population analysis: fk+ = [q(N+1) – q(N)] for nucleophilic attack fk- = [q(N) – q(N-1)] for electrophilic attack (2)

Local softness and electrophilicity indices are calculated using (3) sk+ = Sk+ , sk- = Sk- , sk0= Sk0, (3) ωk+ = ωfk+, ωk- = ωfk-, ωk0 =

All the fundamental vibrations are IR active stable structure. The harmonic vibrational frequencies calculated for doped fullerene with glycine have been compared from low frequency (below 1000 cm-1) to high vibrational frequency (above 1000cm-1) as shown in Table5. The symmetrical stretching vibrations of NH2 group are assigned in 3079, 3569 and 3613cm-1. The two strong stretching vibrations are found at 3569, 3695cm-1 for doped fullerene C19Si-glycine and 3569, 3715cm-1 for C19Ge-glycine. The strongest carbonyl stretching, vibration peak at 1769cm-1for doped fullerene interacting with amino acid C19Si-glycine and at 1780cm-1 for doped fullerene C19Ge-glycine peak are presented in Fig 7. Ge doped fullerene has the highest low frequency values among all of these compounds, this compound has the largest force constants. Higher values of low frequencies obtained for doped fullerene interacting with glycine can be regarded as a higher protection from thermal decomposition of thus molecules. Zero-Point Vibrational Energy (ZPE) for fullerene doped Silicon (Si) interacting with glycine is greater than Germanium (Ge) doped fullerene - glycine molecules. These molecules show that the relative thermal stability of fullerene doped with Si is higher than C19Ge-glycine compound are listed in Table 3. The Infrared vibrational frequencies are computed to further provide the