Excimer formation of 6-(1-pyrenyl)hexyl-11(1-pyrenyl)undecanoate within an ionic liquid and cosolvent-modified ionic liquid mixture

Abstract

The ring closing metathesis within an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]), a 'green' solvent tetraethylene glycol (TEG), and their equimolar mixture is investigated through the intramolecular excimer formation of 6-(1-pyrenyl)hexyl-11-(1-pyrenyl)undecanoate [1]. The excimer formation efficiency correlates directly with the inverse of the bulk viscosity of the systems. A simplistic double exponential decay model based on Birk's scheme is enough to fit the excited state intensity decay of 1 in these liquids. This behavior is in stark contrast to that reported in organic solvents and in scCO(2), where three exponentials are required to fit the fluorescence decay. The activation energies of the excimer formation (E(a)), viscous flow (E(a,η(bulk))), and microviscosity (E(a,η(μ))) were estimated from the temperature dependence. E(a) and E(a,η(μ)) are significantly higher for the equimolar mixture as compared to that for [bmim][PF(6)] or TEG, whereas E(a,η(bulk)) is close to the average. This highlights the important outcome that the cyclization dynamics scales with the microviscosity rather than the bulk viscosity of the systems investigated.

Interplay between Electronic Energy Transfer and Reversible Photoreactions in a Triad Comprising Two Different Styrylbenzoquinoline Photochromes and a ′Hidden′ Quencher

“…In the triad EZ isomer, the reactive Z-SBQ2 photochrome absorbs 31 % of an incident light. For the (E-SBQ1)-(Z-SBQ2) D-A pair, an overlap integral is J = 1.5 × 10 13 M À 1 cm À 1 nm 4 , and the Förster radius R 0 = 2.13 nm, implying effective ET E-SBQ1! Z-SBQ2 (compare these parameters with those in Table 1).…”

“…Multi-chromophoric molecular systems, including covalently linked dyads and triads, attract much attention as models for experimental and theoretical studies of inter-chromophore interactions leading to excimer formation, [1][2][3][4][5][6] energy and/or electron transfer. [7][8][9][10][11][12][13][14][15][16][17][18] In the case when chromophores are also photochromes capable of reversibly photoisomerizing between two stable forms (isomers), multi-photochromic systems can serve as molecular digital switches and logic gates.…”

Excimer Formation Dynamics of Dipyrenyldecane in Structurally Different Ionic Liquids

“…43 Further, the k a of another bis-pyrenyl compound with long ester linkage, 6-(1pyrenyl)hexyl-11(1-pyrenyl)undecanoate whose intramolecular excimer formation follows a simple Birk's scheme within [bmim][PF 6 ] and tetraethylene glycol (TEG) in the temperature range 10−90 °C, is only slightly higher in magnitude to those obtained for 1Py (10)1Py in ionic liquids in the same temperature range. 53 The temperature dependence of the estimated apparent k a is investigated next. Figure 5A presents plots of ln k a versus 1/T for the four [bmim + ] ionic liquids.…”

The Effect of C4H and C5H on the Microstructure of Aqueous Solutions of 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids

“…Thus, many studies have been devoted to understanding the microstructure of IL-solvent and IL-IL mixtures, [5][6][7][8] as it determines the key physicochemical properties of the mixtures, such as viscosity,c onductivity,d ensity,a nd surface tension, which ultimately influence the catalytic performance and dissolving capacity of the ILs. [9] Therefore, studies on the microstructure of IL-solvent mixtures as well as the relationship between the microstructure and physicochemicalp roperties are important for both the academic and the industrial communities. 1-Alkyl-3-methylimidazoliumt etrafluoroborates ([C n mim]BF 4 ; Scheme 1) are prototypical ILs that are usually used as catalysts or solvents for organic reactions and extractive distillation processes.…”

“…During catalytic reactions and the recovery process, ILs always coexist with other solvents. Thus, many studies have been devoted to understanding the microstructure of IL–solvent and IL–IL mixtures,5–8 as it determines the key physicochemical properties of the mixtures, such as viscosity, conductivity, density, and surface tension, which ultimately influence the catalytic performance and dissolving capacity of the ILs 9. Therefore, studies on the microstructure of IL–solvent mixtures as well as the relationship between the microstructure and physicochemical properties are important for both the academic and the industrial communities.…”