Steady-state spectra, rotation times, and time-resolved emission spectra of the probe 4-aminophthalimide (4-AP) in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6 -]) were measured over the temperature range 298−355 K. The steady-state spectroscopy indicates that the solvation energetics of 4-AP in [bmim+][PF6 -] are comparable to those of 4-AP in highly polar but aprotic solvents such as dimethylformamide and acetonitrile (π* ∼ 0.8, ∼ 0.4). The rotation of 4-AP in [bmim+][PF6 -] and in more conventional aprotic solvents generally conforms to the expectations of simple hydrodynamic models. Other than the fact that [bmim+][PF6 -] is highly viscous, nothing distinguishes the rotation of 4-AP in this ionic liquid from its rotation in more conventional polar aprotic solvents. Time-dependent emission spectra, recorded with an instrumental response of 25 ps, indicate that solvation dynamics in [bmim+][PF6 -] occur in two well-separated time regimes. Near to room temperature, the observable response takes place in the 0.1−2 ns time range. This component can be described by a stretched exponential time dependence with an exponent of 0.6−0.7, indicative of strongly nonexponential relaxation. The integral time of the observed component of solvation is proportional to the rotation time of 4-AP and to solvent viscosity, suggesting the involvement of substantial solvent rearrangement. In addition to this relatively slow component, more than half of the solvation response in [bmim+][PF6 -] is faster than can be detected in these experiments, that is, takes place in <5 ps.

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Problem-based learning, process-oriented guided inquiry learning, and peer-led team learning are student-centered, active-learning pedagogies commonly used in science education. The characteristic features of each are compared and contrasted to enable new practitioners to decide which approach or combination of approaches will suit their particular situation.

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The energy of the nitrile stretching mode in benzonitrile is known to be solvent-dependent. Kamlet-Taft solvatochromic parameters pi* and alpha are used to model this dependence in both protic and aprotic solvents using multivariable linear regressions. Aprotic solvents induce red shifts that are shown to be proportional to pi*. In protic solvents, the positions of the two bands attributed to distinct solvation states, F and H, are both fit to the Kamlet-Taft solvatochromic equation. The inclusion of an alpha term yields excellent correlations with the H band, indicative of the strong influence of hydrogen bonding interactions occurring at the nitrile nitrogen in this solvation state. The F band also is best fit by inclusion of the alpha term, albeit with a weaker overall dependence and a much poorer fit than that for the H band. DFT calculations on simple single-molecule complexes with benzonitrile are consistent with the presence of pi-H bonds to the nitrile group as a possible source of the F band dependence on alpha.