Picosecond laser spectroscopic study of orientational dynamics of probe molecules in the dimethyl sulfoxide-water system

Abstract

We report picosecond absorption-recovery laser spectroscopic studies of the orientational relaxation times ( T~J of the structurally similar probe molecules resorufin (anion) and cresyl violet (cation) in a series of binary systems comprising MezSO and water. While these probe molecules exhibit a hydrodynamic-like response in pure H-bonded solvents, a qualitatively different behavior is recorded in these binary systems. A distinctive curvilinear dependence of T~~~ on viscosity is observed. The introduction of dielectric friction to the theoreticaIly calculated response of the host molecular fluid is investigated, but in contrast to results for 7r0t in H-bonded systems, this does not appear to predict the observed behavior. Attention is focused on investigating the microscopic dynamics in electrolyte solutions as an alternative approach.

Fluorescence-lifetime-based pH sensing using resorufin

“…15 The only significant difference on loading into sol-gel is the disappearance of the shoulder at ~ 600 nm which is due to the change in environment. The resorufin anion (R − ) in alkaline solution has a maximum absorption at 572 nm, with a shorter wavelength shoulder around 535 nm, which is in good agreement with previous studies 16 . At high pH ∼9, immobilisation of resorufin in the pure sol-gel (S2) results in a hypsochromic shift in the absorption maximum to 560 nm when compared to the resorufin anion (R − ) in solution (Fig.…”

Rotational diffusion of the 7-diethylamino-4-methylcoumarin C1 dye molecule in polar protic and aprotic solvents

“…The two pioneering works of Eisenthal and coworkers 1,2 have triggered off a large number of similar studies of picosecond depolarisation of either the absorbance or the fluorescence of various dye molecules in different solvents, many testing more or less directly the validity of a linear τ R = f(η/T) dependency, either only within the "stick" limit, [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] or considering also the "slip" limit. [28][29][30][31] Interestingly, most papers have reported qualitative accordance with the prediction of a linear η/Tdependency, but only when varying η for a restricted class of solvents (protic, aprotic, n-alcohols, etc.)…”

Rotational dynamics of pyrrolopyrrole derivatives in alcohols: Does solute–solvent hydrogen bonding really hinder molecular rotation?

“…4,11,35 Recent investigations, however, attributed the observed slower reorientation times to electrical aspects of the solute-solvent coupling known as the dielectric friction. The rotational dynamics of a number of polar solutes in polar solvents have been studied to stress the importance of dielectric friction [15][16][17][18][19][20][21][22][23][24][25][32][33][34][35][36] and also to test various theories of dielectric friction. [26][27][28][29][30][31] Since almost all the probe molecules used in these investigations have functional groups like CvO, NH, and NH 2 , chemical intuition tells us that these groups form hydrogen bonds with protic and aprotic solvents.…”