In benzophenone, intersystem crossing occurs efficiently between the S1(nπ*) state and the T1 state of dominant nπ* character, leading to excited triplet states after photoexcitation. The transition mechanism between S1(nπ*) and T1 is still a matter of debate, despite several experimental studies. Quantum mechanical calculations have been performed in order to assess the relative efficiencies of previously proposed mechanisms, in particular, the direct S1 → T1 and indirect S1 → T2(ππ*) → T1 ones. Multiconfigurational wave function based methods are used to discuss the nature of the relevant states and also to determine minimum energy paths and conical intersections. It is found that the T1 state has a mixed nπ*/ππ* character and that the T2(ππ*) state acts as an intermediate state between the S1 and T1 states. This result is in line with recent experiments, which suggested a two-step kinetic model to populate the phosphorescent state after photoexcitation [Aloïse et al., J. Phys. Chem. A, 2008, 112, 224–231].

A periodic density functional theory method using the B3LYP hybrid exchange-correlation potential is applied to the Prussian blue analogue RbMn[Fe(CN)6] to evaluate the suitability of the method for studying, and predicting, the photomagnetic behavior of Prussian blue analogues and related materials. The method allows correct description of the equilibrium structures of the different electronic configurations with regard to the cell parameters and bond distances. In agreement with the experimental data, the calculations have shown that the low-temperature phase (LT; Fe2+(t62g, S = 0)−CN−Mn3+(t32ge1g, S = 2)) is the stable phase at low temperature instead of the high-temperature phase (HT; Fe3+(t52g, S = 1/2)−CN−Mn2+(t32ge2g, S = 5/2)). Additionally, the method gives an estimation for the enthalpy difference (HT ⇔ LT) with a value of 143 J mol−1 K−1. The comparison of our calculations with experimental data from the literature and from our calorimetric and X-ray photoelectron spectroscopy measurements on the Rb0.97Mn[Fe(CN)6]0.98·1.03H2O compound is analyzed, and in general, a satisfactory agreement is obtained. The method also predicts the metastable nature of the electronic configuration of the high-temperature phase, a necessary condition to photoinduce that phase at low temperatures. It gives a photoactivation energy of 2.36 eV, which is in agreement with photoinduced demagnetization produced by a green laser.

The origin of the features in the Ni 3s X-ray photoelectron spectrum of NiO is investigated using a non-orthogonal configuration interaction approach for an embedded [NiO6] cluster. We study the interplay of inter-atomic screening with the metal core hole and intra-atomic exchange and electron correlation effects. We show that the spectrum can be described in terms of only few key configurations, provided that orbital relaxation effects are explicitly taken into account for the excited charge transfer configurations. The strength of this approach has been demonstrated earlier for those final states that have a high-spin coupling. In the present contribution the analysis is extended to include low-spin coupled 3s-hole states. The effects of enlarging the embedded cluster and of an improved representation of the nearest cluster surroundings were studied for the high-spin final states. We found only minor effects on the computed peak separations.

In benzophenone, intersystem crossing occurs efficiently between the S1(nπ*) state and the T1 state of dominant nπ* character, leading to excited triplet states after photoexcitation. The transition mechanism between S1(nπ*) and T1 is still a matter of debate, despite several experimental studies. Quantum mechanical calculations have been performed in order to assess the relative efficiencies of previously proposed mechanisms, in particular, the direct S1 → T1 and indirect S1 → T2(ππ*) → T1 ones. Multiconfigurational wave function based methods are used to discuss the nature of the relevant states and also to determine minimum energy paths and conical intersections. It is found that the T1 state has a mixed nπ*/ππ* character and that the T2(ππ*) state acts as an intermediate state between the S1 and T1 states. This result is in line with recent experiments, which suggested a two-step kinetic model to populate the phosphorescent state after photoexcitation [Aloïse et al., J. Phys. Chem. A, 2008, 112, 224–231].