A test of hydrodynamics in binary solvent systems: rotational diffusion studies of oxazine 118

Rotational dynamics of neutral red: Do ionic and neutral solutes experience the same friction?

“…Stick vs slip hydrodynamics. While interpreting the rotational reorientation dynamics of polar solutes in polar solvents with the help of hydrodynamic theories both stick [29][30][31][32][33][34]44,48 and slip [35][36][37][38][39][40][41][42] boundary conditions have been used previously. However, the choice of a particular boundary condition is not without ambiguity especially in the case of a polar solute rotating in a polar solvent because hydrodynamic friction alone is not sufficient to explain the observed rotational reorientation times and both slip as well as stick boundary conditions underestimate the actual friction experienced by the rotating molecule.…”

“…60,61 Though the calculated friction using both models is sensitive to the value of the cavity radius, the Alavi and Waldeck model is more sensitive to the cavity radius because the charges are brought closer to the cavity. Waldeck and co-workers [35][36][37][38][39][40][41][42] applied their model to explain the rotational dynamics of medium sized charged as well as neutral molecules in pure and mixed solvents. However, a majority of their studies [35][36][37][38]40,42 were carried out in solvents like dimethyl sulphoxide ͑DMSO͒, benzonitrile, toluene, and methylcyclohexane where the effects of dielectric friction are minimal compared to alcohols.…”

Rotational reorientation dynamics of Rhodamine 700 in different excited states

“…A polar solute rotating in a polar solvent will experience hindrance due to both hydrodynamic and dielectric effects, and the electro-hydrodynamic coupling exists between these two types of friction [59][60][61][62][63]. In practice, as a useful approximation, the total friction z total experienced by the solute molecule can be written as the sum of mechanical and dielectric frictions, and this practice has been followed in literature [11][12][13][14][15][16][17][18][19][20]58] in the past few decades. Hence,…”

“…This is suitable for the conditions when either the solute or the solvent is nonpolar. However, when the solute and the solvent are both polar in nature, the deviations between the experimentally measured reorientation times and the calculated ones using the SED theory are generally observed due to the specific solute-solvent interactions, such as hydrogen bonding [2,[25][26][27] or dielectric friction [11][12][13][14][15][16][17][18][19][20]. In addition, the reorientation time of the solute in solutions is also affected by the size of the solute with respect to the size of the solvent [29,30].…”

Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media

“…Their photophysical and photochemical properties make them suitable as laser dyes and optical sensors. They are frequently used as active agent for solid-state dye lasers [1,2], artificial light-harvesting antennae [3], rotational diffusion studies [4,5], optical spectroscopy in molecular sieves [6,7], nanoparticle conjugated probes [8], DNA sequence detection [9], and tuning lasers [10].…”