Synthesis, molecular structure, and properties of DABCO bromide based ionic liquid combining spectroscopic studies with DFT calculations

Abstract

A new DABCO-based ionic liquid, namely 1-octyl-1,4-diazabicyclo [2.2.2] octan-1-ium Bromide ([C 8 DABCO + ][Br -]) has been synthesized through N-alkylation of 1,4-diazabicyclo [2.2.2] octane with 1-bromooctane using a simple procedure in one step. This [C 8 DABCO + ] [Br -] IL was characterized by FT-IR, FT-Raman and by 1 H and 13 C-NMR spectroscopies. The structure of [C 8 DABCO + ][Br -] IL was confirmed combining 1 H and 13 C-NMR spectroscopies with B3LYP/6-31G* calculations. Three ionic C-H•••Br bonds were predicted by natural bond orbital (NBO), atoms in molecules (AIM) calculations and bond orders but a monodentate coordination between cation and anion is suggested because only one of them has higher energy and lower distance. The effect of Br on properties of IL is clearly observed by the change in orientation and direction of dipole moment vector in the IL, as compared with the cation. NBO studies reveal that the Br anion strongly stabilizes to cation to form the IL. The complete vibrational assignments of 129 and 132 vibration modes expected for the cation and its IL were performed by using two harmonic force fields with the SQMFF methodology and transferable scaling factors. The scaled harmonic force constants were also reported for both species. The Br confers a higher reactivity to [C 8 DABCO + ][Br -], as suggested by analyses of frontier orbitals. The effect of Br is also observed in the different assignments observed for the IL and its cation. Reasonable correlations were found between the experimental IR, Raman and NMR spectra and the corresponding theoretical ones.

Explicating the recognition phenomenon of hazardous nitro-aromatic compound from contaminated environmental and cellular matrices by rationally designed pyridine-functionalized molecular probes

“…The theoretical calculations (carried out in Turbomole v7.0), carried out for determining the geometry-optimized structures of the sensors and sensor-analyte adducts, were completely in line with the experimental findings [ [41] , [42] , [43] ]. Upon the addition of TNP, the lowering of energy and the HOMO-LUMO gap of the sensors clearly attributed to the productive host-guest interaction ( Table 2 ).…”

Thermal Decomposition, Low Temperature Phase Transitions and Vapor Pressure of Less Common Ionic Liquids Based on the Bis(trifuoromethanesulfonyl)imide Anion

“…The ionic liquids based on 1-decyl-1,4-diazabicyclo [2.2.2] octan-1-ium [DABCO10 + ], 3,3′-dimethyl-1,1′-(1,3-phenylenedimethylene)-bis(1H-imidazolium) [m-C 6 H 4 (CH 2 ImMe) +2 ], 3,3’-dibutyl-1,1’-(1,4-phenylenedimethylene)-bis(1H-imidazolium) [p-C 6 H 4 (CH 2 ImBu) +2 ] and 1-hexylpyridinium [C 6 Py + ] with chloride or bromide anions were prepared through a procedure described in detail elsewhere [ 36 , 37 , 38 , 39 ] and reported in a shorter form in the present paper. The syntheses are based on an alkylation reaction of precursors and alkyl halides.…”

3D mesoporous polycalix-functionalized dual Brønsted–Lewis acidic double-charged DABCO-based ionic liquid: a powerful and recyclable supramolecular polymeric catalyst for the synthesis of spiro-fused[4H-pyran]

“…In this regard, double-charged or di-cationic ILs based on 1,4-diazabicyclo[2.2.2]octane (DABCO) are much more attractive due to their bearing two active N atoms. [66][67][68][69] Also, this bicyclic organic compound shows features such as medium hindrance, a cage-like structure, high reactivity, and weak alkalescence that make it suitable for wide use in producing ionic liquids. 66,[70][71][72] As a result of the cage-like scaffold in DABCO (which decreases nitrogen inversion due to the high energy barrier), the localization of the lone-pair electrons of nitrogen increases.…”

“…[66][67][68][69] Also, this bicyclic organic compound shows features such as medium hindrance, a cage-like structure, high reactivity, and weak alkalescence that make it suitable for wide use in producing ionic liquids. 66,[70][71][72] As a result of the cage-like scaffold in DABCO (which decreases nitrogen inversion due to the high energy barrier), the localization of the lone-pair electrons of nitrogen increases. In this manner, DABCO is more ready for covalent quaternization.…”