Large Stokes Shift Ionic‐Liquid Dye

Abstract

Abstract:We have incorporated the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he IL dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide [6MQc][NTf 2 ]w as characterized by NMR, ATRI R spectroscopya nd X-ray crystallography.T he fluorescence of the IL dye has al arge Stokes shift of Dl = 116 nm and aq uantum yield of f F = 0.56 in acetonitrile.C haracteristic solvent dependent shifts can be detected in the emission spectra. In other ILs,acetonitrile and THF we observe abathochromic shift of up to 28 nm compared to the pure IL dye at 467 nm. Forstronger polar solvents the fluorescence signals are strongly red-shifted to 650 nm indicating proton transfer to the solvent molecules in the excited state.T his underlines the importance of the IL building block [ MQc] + as photo acid.Fluorescent dyes are important tools in many branches of chemistry related sciences,s uch as biological chemistry, [1][2][3][4][5][6][7][8] materials science, [9][10][11] or solar-energy conversion. [12,13] Attractive fluorescent dyes are characterized by their extended spectral range,h igh emission quantum yields,p hotostability and good solubility in the solvent. Thef luorescent dye N-methyl-6-oxyquinolone [6MQz] was used for studying solvation phenomena. Thec olor of this solvatochromatic dye molecule depends strongly on the polarity of the surrounding,a st he permanent dipole moments strongly change upon excitation from the ground to the excited state.T hus [6MQz] has been used as dye for understanding solvation processes and proton transfer to solvents. [14][15][16][17][18][19][20][21][22] In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility. [10,11,18,19] Whereas other dyes have been extensively applied to probe the polarity of ionic liquids,t he protonated form of [6MQz] has never been used as moiety of an ionic liquid itself. [23,24] Thus,t he goal of our work was to incorporate the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he resulting ionic liquid dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide ]involves anion metathesis reaction and is shown in Scheme 1. Initial N-methyl-6-hydroxyquinolinium iodide was prepared using ak nown procedure which is also described in the Supporting Information (SI0). [25,26] Then, equimolar amounts of N-methyl-6-hydroxyquinolinium iodide (287 mg, 1mmol) and silver bis(trifluoromethylsulfonyl)imide (388 mg, 1mmol) were dissolved in 15 mL water each. Thet wo solutions were combined and the reaction mixture was stirred for 15 min. Silver iodide,which precipitates instantly,was filtered off and discarded. Them other liquor was removed on ar otary evaporator and the residue was dissolved in 25 mL ethanol to carry out ah ot-filtration with activated charcoal. After filtration, the solvent wa...

Tuning the photophysical and photo acidic properties of N-methyl-6-oxyquinolonium-based ionic liquid dyes: the role of solvent and substitution effects investigated by a TD-D3-DFT approach

“…A comparison of CO bond length in 6MQz-AC and [6MQc][CF 3 COO] complexes (1.287 and 1.320 Å) with that found in [6MQc][Y3–6] ion pair complexes (1.338, 1335, 1.340 and 1.340 Å) confirms that quinonoid resonance structure 6MQ is a predominant form in completely ( 6MQz-AC ) and slightly [6MQc][CF 3 COO] proton transferred complexes. The λ 1 values reported by Schmode et al 53 were 349 and 343 nm for [6MQc][Y5] IL dye in water and acetonitrile, in good agreement with our results (349 nm and 350 nm).…”

“…The calculated λ 1 emissions at the PBE0-D3/6-311++G(d,p) level of theory for [6MQc][Y5] (Y5 = [N(CF 3 SO 2 ) 2 ] − ) IL dye in water and acetonitrile are comparable with the experimental results ( λ 1 = 593 and 449 nm). 53…”

Selective Expression of Organic P hosphorescence Units: When H-Benzo[f]indole Meets 7H-Benzo[c]carbazole

“…Ultralong organic room-temperature phosphorescence (UORTP) materials are an emerging class of promising luminescent materials with a large Stokes shift and long-lived lifetime (τ > 100 ms) − and have been drawing considerable attention in the past years due to their advantages of low cost, low toxicity, simple structure modification, and easy color tunability , and their wide applications in organic light-emitting diodes (OLEDs), , high-sensitive chemical sensing, high-resolution biological imaging, − information encryption/data storage, − etc. The guest–matrix doping strategy has been becoming a universal method to construct UORTP materials − as the pure powders of organic phosphorescence molecules usually suffer from a self-quenching effect at room temperature. ,, To simplify the description, the guest–matrix phosphorescence system can be named guest@matrix.…”

Ionic Liquids [M3+][A−]3 with Three‐Valent Cations and Their Possible Use to Easily Separate Rare Earth Metals

“…While ILs can have remarkable fluorescence properties,[ 33 , 34 , 35 ] rare earth metal ions exhibit interesting luminescent behaviour as well, also as part of ionic liquids. [ 15 , 36 ] Whereas yttrium and lanthanum three‐valent cations are considered to be non‐emitting[ 37 , 38 ] and usually are only present with photoluminescence in doped solid materials and some exceptional complexes, europium salts find widespread use due to their intense and characteristic fluorescence under UV illumination.…”