Viscosity dependent internal conversion in the rhodamine dye, fast acid violet 2R

Abstract

The fluorescence lifetimes of N-(2-tolyl)-N'-(2-tolyl-5-sulphon~te) rhodamine, Fast Acid Violet 2R, in a series of alcohols, range from 10 to 160 ps as a result of viscosity dependent ultrafast internal conversion. Rates of internal conversion are shown to be dependent upon the microviscosity, as opposed to the bulk viscosity of the solvent. Within a given homologous series of alcohols, the fluorescence lifetime (zf) was found to vary with solvent viscosity (q) according to a Forster-Hoffmann type equation: zf = CV''~, but the value of C was different between the monohydric alcohols, dihydric alcohols and glycerol. This dye may be a good candidate as a fluorescent probe of solvent structure.

Fluorescence Anisotropy of Molecular Rotors

“…[9] This value also gave a good fit for fluorescence lifetimes of Fast Acid Violet 2R, a rhodamine dye, in solutions of varying viscosity. [13] Importantly, the similar fluorescence lifetimes of the dye in monohydric and dihydric solvents with bulk viscosities differing by almost an order of magnitude showed that it is the microscopic rather than bulk viscosity which is the dominant factor in determining the decay rate. For perhaps the most widely studied molecular rotor, 9-(2,2-dicyanovinyl)julolidine (DCVJ) it was initially proposed that upon photoexcitation a twisted intramolecular charge transfer (TICT) state is formed, [14] with investigations to determine the nature of the intramolecular rotation and about which bond it occurs.…”

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“…as in diethylene glycol and glycerol. 24,25 A study of fluorescent life times and quantum yields was undertaken for two of our chromophores (MORPIP and AMINO) dissolved in a series of normal alcohols, diethylene glycol and glycerol to evaluate the influence of the viscosity and polarity of the medium on their luminescence properties.…”

“…Previous studies indicate that this is due to the constraint placed on changes in molecular conformation during excitation by the hydrogen-bonding networks. 24,25 3.2 Glass forming solvents Solvents that form low temperature glasses have been extensively employed as matrices 17 for fluorophores. 43,44 If the increase in fluorescence quantum yield in viscous solvents is due to the constraining effect of the hydrogen bonding network a similar effect can be anticipated in glassy matrices.…”

“…43,44 If the increase in fluorescence quantum yield in viscous solvents is due to the constraining effect of the hydrogen bonding network a similar effect can be anticipated in glassy matrices. Suitable glass forming solvents are 1-propanol, 24,45 2MTHF 46 and a 2:2:5 mixture of ether, ethanol and isopentane (EPA). 47 The use of 1-propanol glasses allows a direct comparison to be made with the room temperature solution data.…”

Kinetics of intercalation of fluorescent probes in magnesium–aluminium layered double hydroxide within a multiscale reaction–diffusion framework

“…Theoretical explanations of this phenomenon were given by Drexhage [28], who studied the dependence of the lifetime of RhB on the amino group's flexibility. Thus, upon excitation and due to the ability of rotation along the C-N bond, this probe displays a distortion in its excited state to form a twisted intra-molecular charge transfer (TICT) state [29][30][31]. This internal rotation results in a non-radiative decay; consequently, fewer lifetime values are exhibited [32].…”