Local structure of ionic liquids probed by self-quenching of thiobenzophenone

Abstract

Self-quenching of the triplet excited state of thiobenzophenone ((3)TBP*) in molecular solvents, a sodium dodecyl sulfate (SDS) micellar solution, and ionic liquids (ILs) was measured using nanosecond laser flash photolysis. In the molecular solvents and ILs, (3)TBP* single-exponentially decayed, and the decay was accelerated with increasing TBP concentration. Self-quenching rate constants (k(SQ)) obtained in the ILs were smaller than those in the molecular solvents with similar solvent viscosities, indicating that molecular diffusion is inhibited in the ILs. In the SDS micellar solution, the decay of (3)TBP* showed two components. The fast decay component was attributed to self-quenching of (3)TBP* which presents inside micelles containing two or more TBP molecules, while the slow decay component was from deactivation of single (3)TBP*. The decay of (3)TBP* in an IL, N,N,N-trimethyl-N-propylammonium bis(trifluoromethylsulfonyl)amide (TMPA TFSA), had only one decay component, showing that unlike the micelles, the local structure of TMPA TFSA does not have a long lifetime. The cage lifetime of TMPA TFSA was estimated to be between 17 and 20 ns.

Ionic Liquid Dependence of Triplet-Sensitized Photon Upconversion

“…We will briefly discuss the reason for the decrease in τ T as the motions of the molecules become more allowed. First, self-quenching (T 1 + S 0 → S 0 + S 0 ) among perylene molecules is not responsible for this behavior, and this is based on our experimental confirmation of τ T being independent of perylene concentration (Figure S6 in the Supporting Information). Generally, for a molecule to change its electronic spin state, a fluctuating time-dependent magnetic perturbation at the position of the molecule is required. , As for perylene, the exchange energy J that serves as an energetic barrier between the T and S states is relatively large (ca.…”

Pressure-enhanced surface interactions between nano-TiO2 and ionic liquid mixtures probed by high pressure IR spectroscopy

“…[2][3][4][5][6] Ionic liquids are generally defined as organic salts with melting points below 100 1C and comprised entirely of ions. [13][14][15][16] The alkyl side chain length has an influence on the supramolecular assemblies and aggregation effects between alkyl tails may lead to an ordered local environment. The most extensively studied ionic liquids are the 1-alkyl-3-methylimidazolium salts.…”

“…Some researchers suggested that imidazolium-based ionic liquids may be considered as nanostructured with polar and nonpolar regions. [13][14][15][16] The alkyl side chain length has an influence on the supramolecular assemblies and aggregation effects between alkyl tails may lead to an ordered local environment. 9,17 The physical and chemical properties of ionic liquids are tunable through the selection of their cation and anion moieties.…”

Specific interactions between the quaternary ammonium oligoether-based ionic liquid and water as a function of pressure

“…Ionic liquids containing dissolved water may not be regarded as homogeneous solvents but have to be considered as microheterogeneous materials, where the microheterogeneity may be attributed to incomplete mixing at the molecular level. [15][16][17][18] Because ionic liquids are entirely composed of ions, ionic liquids have been utilized in the preparation of ion gels (a new class of solid state electrolytes). [19][20][21][22] The addition of gelling agents to ionic liquids occasionally leads to the gelation of ionic liquids and the gelling agents include low molecular weight gelators, nanoparticles, and block copolymers.…”