Polarization by the effect of a small torsional change in the benzothiazole (A)-benzobisthiazole (B) oligomer A-B13-A

Abstract

Abstract:We use a method for the calculation of the molecular dipole ( µ ) and quadrupole ( θ ) moments and dipole-dipole ( α ), dipole-quadrupole ( A ) and quadrupole-quadrupole ( C ) polarizabilities which we have successfully applied to the benzothiazole (A)-benzobisthiazole (B) linear oligomer A-B 13 -A. Two model rotational isomers have been characterized: (1) the fully-planar (000) conformation; and (2) a rotational isomer with each unit rotated in the range 1 − 10° in the same direction (+++). For isomer 000, µ is smaller than for +++. The calculation of α , A and C has been carried out by the interacting induced dipoles polarization model that calculates tensor effective anisotropic point polarizabilities (method of Applequist et al.). The values of A are specially sensitive to µ which varies under rotation. This fact explains the great values of A x xx , for the +++ polar isomer. It is found that small torsional changes can enhance solubility by a clear increasing of the hydrophilic accessible surface area. However, the torsion of the oligomer varies the value of µ and so modifies α , C , and, specially, A . For conformer +++, polarization effects occur even when each unit is rotated only φ = 1°. The observed effect is an increase in µ and, hence, in α , C , and, specially, A .

New dimension indices for the characterization of the solvent-accessible surface

“…The TOPO program37–42 calculates the molecular volume V and molecular bare surface area S 43–48 by means of a 3D‐grid method, which is improved following a procedure proposed by Meyer 43, 44. The details have been discussed elsewhere, and will not be repeated here 41.…”

Topological Charge-Transfer Indices: From Small Molecules to Proteins

“…Torrens et al also developed an interacting induced-dipole polarization model for molecular polarizabilities and applied it to the benzothiazole (A)-benzobisthiazole (B) linear oligomers up to A-B 13 -A [31] and analyzed the torsional effects on A-B 13 -A molecular polarizabilities. In other result, Torrens et al [32] studied the polarization by the effect of a small torsional change in A-B 13 -A. We also applied the interacting induced-dipole polarization model to reference molecules, amino acids and model peptides [33].…”

Resonance in Interacting Induced-Dipole Polarizing Force Fields: Application to Force-Field Derivatives

“…where  a ind is the induced molecular dipole moment and a, b, c… denote Cartesian components [9][10][11][12][13][14][15][16][17][18][19]. Considering a set of N interacting atomic polarizabilities, the atomic induced-dipole moment has a contribution also from the other atoms: …”