Structural properties and vibrational analysis of Potassium 5-Br-2-isonicotinoyltrifluoroborate salt. Effect of Br on the isonicotinoyl ring

Abstract

In this work, the potassium 5-Br-2-isonicotinoyltrifluoroborate salt (B-ITFB) have been experimentally characterized by using FT-IR, FT-Raman and ultravioleta-visible spectra while Ab-initio calculations in gas and in aqueous solution phases were employed to predict their structural and vibrational properties.Here, the results were compared with those reported for the potassium 2-isonicotinoyltrifluorborate salt (ITFB) in order to know the impact of Br on the 2-isonicotinoyl ring and its effects on the properties of B-ITFB. Potential energy surface using B3LYP/6-311þþG** calculations has revealed two conformers for B-ITFB with C1 symmetries where only one of them presents the minimum energy. The incorporation of Br in the 5 position of isonicotinoyl ring generates: (i) a change in the symmetry from CS in ITFB to C1 in B-ITFB, (ii) a decreasing in the solvation energy due to higher size of Br, (iii) notable reduction in the Mulliken charges on all the C atoms of ring and, especially, on the C11 atom of trifluoroborate group in both media, (v) smaller bond order values, (vi) an important inductive acceptor effect, (vii) a decreasingin the electron density distribution, specifically in solution and (viii) a smaller reactivity and low electrophilicity and nucleophilicity indexes, as compared with ITFB. On the other hand, for B-ITFB the force fields in both media, the complete assignments of 45 normal vibration modes and the force constants are reported for first time