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

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/6-311++G** calculations has revealed two conformers for B-ITFB with C-1 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 decreasing in 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. (C) 2019 Elsevier B.V. All rights reserved.