Abstract
The solvent Stark effect on the spectral shifts of anthracene is studied with temperature‐dependent solvatochromic measurements. The Stark contribution Δv Stark to the absorption shift Δv p in polar solvents is measured to be Δv Stark=(53±35) cm−1, in reasonable agreement with dielectric continuum theory estimate of 28 cm−1, whereas the major shift Δv p∼300 cm−1 presumably originates from the solute quadrupole. We pay attention to the accurate correction of Δv p for the nonpolar contribution that is crucial when the shifts are modest in magnitude.
Highlights
Ea 1⁄4 À cq1 1⁄4 À 3a 2a3 RTf p (3)When a nondipolar polarizable solute like anthracene, perylene21 or trans-stilbene is immersed in a polar solvent, it is stabilized via interaction with fluctuating solvent electric field e by energy where f p 1⁄4 1⁄22ðeÀ 1Þ=ð2eþ1Þ À 2ðn2À 1Þ=ð2n2þ1Þ is the wellknown response in polar solvents.[4]
Ea 1⁄4 À ah e2 i=2 where α is the solute polarizability, and the averaging is taken over all solvent configurations.[1,2]
The Stark effect directly results in solvatochromic shifts for stabilization is commonly called the solvent Stark effect.[3,4,5,6,7]
Summary
21 or trans-stilbene is immersed in a polar solvent, it is stabilized via interaction with fluctuating solvent electric field e by energy where f p 1⁄4 1⁄22ðeÀ 1Þ=ð2eþ1Þ À 2ðn2À 1Þ=ð2n2þ1Þ is the wellknown response in polar solvents.[4]. Cql are related to slow Energies E and shifts Δv are in eV, kJ/mol or cmÀ 1 with the (orientational) and fast (quantum, electronic) degrees of free- relations between the units dom of the solvent with dielectric constant e and refractive index n; R = 8.31 J/mol/K is the gas constant and T temperature; eV 1⁄4 96:49 kJ=mol 1⁄4 8065 cmÀ 1 1⁄4 1:602 D2=Å3, 40 l = 1 or 2 corresponds to dipolar or quadrupolar solute, or with l 1 D2=Å3 1⁄4 0:624 eV 1⁄4 5032 cmÀ 1. Proposed quadrupolar or higher multipolar nature of the aforementioned shifts. In our case Δvp does not contain the dipolar part, but presumably contains Stark ΔvStark and quadrupolar[3] ΔvQ part
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