Density functional theory study of the nuclear magnetic resonance properties and natural bond orbital analysis of germanium-phenyl nanocluster

Abstract

In this study, the optimized molecular geometry and vibrational frequencies of novel germanium-phenyl nanostructure were calculated using the hybrid functional B3LYP/Lanl2dz as implemented in Gaussian 09 program. The obtained geometries from the calculations of density functional theory were used to carry out natural bond orbital analysis. The stabilization energy E₂ that is related to the delocalization trend of electrons from donor to acceptor orbitals was also computed. The higher the stabilization energy E₂, between a bonding orbital and an acceptor orbital the greater the interaction between them, signifying clear evidence of stabilization that is originating from the hyperconjugation of H- bonded interaction. Our results reveal strong stabilization energy E₂, of orbital interaction between the bonding orbitals (Ge₄-Ge₆) and non-lone pair Ge₈ with value of 81.36 Kcal/mol. The NMR isotropic chemical shift and magnetic shielding of [Ge₉(C₆H₅)] nanostructure were calculated using Gauge-including atomic orbitals(GIAO) algorithm and results compared with experimental data. The theoretically calculated values of the coupling constant in the gas phase are ³ J (H − H) =10.99 Hz, ³ J (C − H) =10.99 Hz, and ³ J (C −C) =12.99Hz respectively and are observed to be bigger than the experimental value with a difference of about 3.29 Hz. The spin-spin coupling constant ³J was calculated by means of the generalized Karplus-type relationship.