We have studied bond length and bond angle of a series of phenols. For present study the molecular modelling and geometry optimization of all the compounds were carried out with MOPAC software using MINDO/3 methods. We have conclude that the order of bond lengths between C-O, C-C, C-H and O-H atoms have been changed by changing the position of the substituents i.e., from ortho to para substitution. The C-C-C band angles have the same value while the C-C-O and C-O-H band angles differ from their normal values on substitution.
We have studied the molecular orbitals of ruthenium (II) bromide, in order to study the
extent of contribution of 4d, 5s and 5p orbitals in the formation of molecular orbitals. The
3D modeling and geometry optimization of the ruthenium (II) bromide have been done by
CAChe software using molecular mechanics with EHT option. Eigenvector analysis shows
that 4dx2-y2 and 4dxy orbitals of ruthenium play a major role in bonding between ruthenium
and bromide, 5s orbital is next and 4p orbitals have a negligible role. There is a difference
in energy levels of s and p orbitals of bromide are 0.6090 eV. The overlap population
analysis shows that the nonbonding orbitals are present in 6th and 7th molecular orbitals. No
molecular orbital is formed by only two atomic orbitals. All molecular orbitals have
contribution from many atomic orbitals; the difference is only in extent of involvement.
Computational study of electronic structure of some of azoxybenzene-based liquid crystals belonging to nematic class: p-azoxyanisole, p-azoxyphenetole, ethyl-p-azoxybenzoate, ethyl-p-azoxycinnamate and n-octyl-pazoxycinnamate have been studied. In order to obtain more information on the reactivity of above molecules towards nucleophile and electrophile, we performed semiempirical (AM1, PM3 and PM5) and density functional theory (DFT) based calculation to evaluate the negative and positive charge distribution in all the cases. p- Azoxyanisole is treated as reference compound (RC). The study shows that replacement of -OCH3 group of RC by - OC2H5 group increase the QMAX, while successive addition of –CH=CH-COOC8H17, –CH=CH-COOC2H5 and - COOC2H5 groups decreases the QMAX, respectively. In all the compounds it is the carbon atom at site 12, C12, which has QMAX, except in ethyl-p-azoxybenzoate, where QMAX is at C9. In respect to QMIN, it is the azoxy oxygen, O24, which has QMIN and the only differences in the trend is due to the positions of ethyl-p-azoxybenzoate and noctyl- p-azoxycinnamate, which are interchanged. The study also shows that DFT based calculations provide better result than the semiempirical based calculations
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