The bond polarizability theory of Raman optical activity calculations on (R) - (+) bromochlorofluoromethane

Abstract

A general origin-invariant bond polarizability theory of Raman optical activity is presented. The theory is cast into a computational form for the special case of a molecule composed entirely of axially-symmetric bonds and is then used to calculate the Raman optical activity in the fundamentals of all the normal modes of (R) -(+) brornochlorofluoromethane.

Raman and ROA Spectra of (−)- and (+)-2-Br-Hexahelicene: Experimental and DFT Studies of a π-Conjugated Chiral System

“…All helicene systems are constituted by ortho-fused benzene molecules, each aromatic unit having a large polarizability tensor, with cylindrical symmetry and thus with two independent parameters: The in-plane α ∥ polarizability is approximately equal to 12 Å 3 , and the orthogonal α ⊥ polarizability is close to 6 Å 3 . − The latter values are rather large, and due to this, we can also expect strong Raman features, at least for some vibrational NM. It is also interesting to note that Barron, co-workers, and the British school devoted much work and numerous papers to establishing a relation between group (bond) polarizabilities and G′ and A tensors. ,,− …”

Ab initio calculation of vibrational Raman optical activity

“…More typical applications, such as structural studies (including the assignment of absolute configurations) are also discussed. Since the subject of the review is ab initio calculations, we will not discuss early semi‐empirical calculations such as the bond‐polarizability model of Barron 28, subsequently extended to semi‐empirical molecular orbital theory in the complete neglect of differential overlap approximation (CNDO) introduced by Polavarapu 29.…”

Polarized raman optical activity and the bond polarizability model

“…In particular, the bond polarizability model has proved valuable in providing simple physical pictures of the source of ROA in archetypal chiral structures [12] as well as providing a complete computational method [13,14]. We have recently constructed a new optical multichannel ROA instrument, based on the Applied Photophysics Model LR36, details of which will be published elsewhere.…”

“…If all the bonds have axial symmetry, contributions such as ~i,~ G),~ and cq~ e~oA~ vanish, where subscripts i and j denote corresponding tensors localized on bonds i and j and referred to local origins lying along the bond symmetry axes [12][13][14]. t 1 The remaining terms in the development of ~=p G~p and 5oga=p g=~aA~a p are found to be identical, and the isotropic term a== Gig vanishes (see equations (7.3.35 b, c) of [12], or equations (2.12 b, c) of [13]. A s 7 even if the bond bending vibration is totally symmetric.…”