The quantum chemical solvation of indole: accounting for strong solute–solvent interactions using implicit/explicit models

Abstract

In this paper, we investigate the efficacy of different quantum chemical solvent modelling methods of indole in both water and methylcyclohexane solutions. The goal is to show that one can...

Direct Force Constants for Spectroscopic Analysis from Quantum Mechanical Information: SmartField Force Field

“…31,34 To this end, a valid alternative comes from the use of multi-reference method such as the CASSCF. 31,33,35 Their values are in agreement with previous theoretical data, which report values of 259.7 nm and 205.9 nm for L a and L b states with an active space of ten electrons and nine orbitals, however, even in this case the order of the states is still inverted. 35 This is likely because of still scarce electron correlation even when more configurations are taken into account.…”

“…A similar trend is observed for the emission, where a large increase of λ max is calculated for the clusters with more than 7 water molecules explicitly included in the QM region. This strong stabilisation was previously observed for clusters of indole with water, 33 In particular, an increase of about 10 nm is observed with respect to the bare solute, with exception of the second cluster which shows an larger increase of 34 nm. Such a low λ max might likely be due to sampled conformal regions of excited-state which are closer in energy to that of the ground-state trajectory.…”

“…Their relative oscillation strength are slightly overestimated with respect to the theoretical values in the literature, which ranges between 0.11-0.13 and 0.06-0.02 for L a and L b , respectively, [31][32][33] while the order of the two states is reversed with respect to the experiment. This is a known aspect of the limits of most DFT exchange-correlation functionals which are unable to predict the correct order of the two states because of the single-reference nature of DFT methodology.…”

“…30 This aspect was also previously reported, and it can be again ascribed to the single-reference nature of TDDFT. 31,33 To this end, for instance, Dreuwet al employed the algebraic diagrammatic construction (ADC) scheme of the polarization propagator at the second and third orders, 31 while DFT-based multi-reference configuration interaction DFT/MRCI method was used by Russo et al to obtain good Stoke shifts. 33 In the present context, since the polar nature of La state, we mainly focus on the underlying mechanism of the stabilization of this state in solution.…”

A first principles examination of phosphorescence

“…34 The energetic ordering or spacing of these oen degenerate states can change with respect to the medium, altering uorescence and non-radiative decay pathways, a phenomenon known as solvatochromativity. 35,36 Good examples for this include diketo-pyrrolopyrrole, 31,37,38 indole, [39][40][41] and acridine, 11,42 with all three displaying drastically different photophysics depending on the polarity of the solvent it is measured in. Acridine in particular is interesting as in addition to the low lying L a and L b states, there is also a low lying np* state.…”