Effect of the halogen F---H bond on the structural and vibrational properties of the Potassium 3-furoyltrifluoroborate salt

SILVIA ANTONIA BRANDAN; DAVIES, LILIAN; MAXIMILIANO ALBERTO IRAMAIN

Jyväskylä

Congreso; . XXII Horizons in Hydrogen Bond Research (HBOND); 2017

HBOND

The molecular structure of the potassium 3-furoyltrifluoroborate salt (FTFB) was notexperimentally determined and only their synthesis and characterizations by using NMR andmass spectroscopies were published [1]. The structural properties of this salt are ofimportance due to that many studies suggest that there are steric and conformational factorsthat modulate their reactivities mainly in aqueous solution. In the present work, DFTcalculations in gas phase and in aqueous solution were combined with the experimentalinfrared (FTIR) and Raman spectra in order to calculate the structural, electronic, topologicaland vibrational properties for this salt.Four structures for FTFB were found by using the hybrid B3LYP and the two 6-31G* and 6-311++G**levels of theory with the Gaussian 09 program [2]. The most stable structure with Cs symmetry can be seen in Fig.1. In solution, the PCM/SMD models were used [3] to predict the solvation energies. Expansion of volume was observed in solution with a solvation energy of -75.21 kJ/mol using 6-31G* basis set. The NBO and AIM programs were used to analyze the stabilities of this salt inboth media. The vibrational analyses of FTFB in both media were performed with the SQMFF approach [4] and the Molvib program [5]. Also, the 39 vibration modes classified as, 26 A? (planar) + 13 A??(out-of-plane) were completely assigned.FTFB showing the F---H bond The frontier orbitals calculated for FTFB in both media show that this salt in gas phase is more reactive than in solution and, that by using the 6-31G* basis set the reactivity increase, as experimentally was reported. Probably, the decreasing in the bond orders observed for the F13 atoms in solution with both basis sets are due to increasing observed in the atomic Mulliken and natural population charges on these atoms. Besides, both charges on the Katoms increase in solution increasing the bond orders of O10 atoms and, as a consequence, thelone pairs on these atoms could be easily shared in solution by H bonds formation with watermolecules. Thus, the F13---H6 interaction and the K15-O10 bond observed could probablymodulate their reactivities in aqueous solution.