In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners.

This study aims to assess present day density functionals in the description of spin crossover iron(II) complexes. Two recently synthesized spin crossover complexes were considered. Theoretical calculations were made using 53 of the most popular exchange-correlation density functionals with triple zeta plus polarization quality basis sets. The present work shows that even though different density functionals can lead to different energy gaps between spin states, most of them are very similar for these two compounds when a comparison between energy gaps is sought. The present work shows that even though different exchange correlations can lead to different energy gaps between spin states, the difference between these gaps calculated at different geometries and that calculated at a given reference geometry is surprisingly independent of the choice of functional. The reasons for the similarities and the differences among exchange and correlation functional combinations are discussed.

The formation of dimethyl carbonate (DMC) from CO₂ and methanol with the dimer [n-Bu₂Sn(OCH₃)₂]₂ was investigated by experimental kinetics in support of DFT calculations. Under the reaction conditions (357–423 K, 10–20 MPa), identical initial rates are observed with three different reacting mixtures, CO₂ /toluene, supercritical CO₂ , and CO₂ /methanol, and are consistent with the formation of monomeric di-n-butyltin(IV) species. An intramolecular mechanism is, therefore, proposed with an Arrhenius activation energy amounting to 104 ± 10 kJ mol⁻¹ for DMC synthesis. DFT calculations on the [(CH₃)₂Sn(OCH₃)₂]₂ /CO₂ system show that the exothermic insertion of CO₂ into the Sn–OCH₃ bond occurs by a concerted Lewis acid–base interaction involving the tin center and the oxygen atom of the methoxy ligand. The Gibbs energy diagrams highlight that, under the reaction conditions, the dimer–monomer equilibrium is significantly shifted towards monomeric species, in agreement with the experimental kinetics. Importantly, the two Sn–OCH₃ bonds are prompt to insert CO₂ . These results provide new insight into the reaction mechanism and catalyst design to enhance the turnover numbers.

The different fragmentation channels of cytosine, adenine and guanine have been studied through DFT calculations. The electronic structure of bases, their cations, and the fragments obtained by breaking bonds provides a good understanding of the fragmentation process that can complete the experimental approach. The calculations allow assigning various fragments to the given peaks. The comparison between the energy required for the formation of fragments and the peak intensity in the mass spectrum is used. For cytosine and guanine the elimination of the HNCO molecule is a major route of dissociation, while for adenine multiple loss of HCN or HNC can be followed up to small fragments. For cytosine, this corresponds to the initial bond cleavage of N3–C4/N1–C2, which represents the main dissociation route. For guanine the release of HNCO is obtained through the N1–C2/C5–C6 bond cleavage (reverse order also possible) leading to the largest peak of the spectrum. The corresponding energies of 3.5 and 3.9 eV are typically in the range available in the experiments. The loss of NH₃ or HCN is also possible but requires more energy. For adenine, fragmentation consists of multiple loss of the HCN molecule and the main route corresponding to HC8N9 loss is followed by the release of HC2N1.

The nature and the position of the substituents are important factors driving the NLO properties.

The fragmentation process of the uracil RNA base has been investigated via DFT calculations in order to assign fragments to the ionisation mass spectrum obtained after dissociation induced by collision experiments. The analysis of the electronic distribution and geometry parameters of the cation allows selection of several bonds that may be cleaved and lead to the formation of various fragments. Differences are observed in the electronic behaviour of the bond breaking as well as the energy required for the cleavage. It is reported that N₃–C₄ and N₁–C₂ bonds are more easily cleaved than the C₅–C₆ bond, since the corresponding energy barriers amount to ΔG = +1.627, +1.710, +5.459 eV, respectively, which makes the C₅–C₆ bond cleavage almost prohibited. Among all possible formed fragments, the formation of the OCN⁺ fragment for the peak at m/z = 42 Da is excluded because of an intermediate that was not observed experimentally and too a large free energy barrier. Based on the required free energy, it is observed that two fragment derivatives: C₂H₄N⁺ and C₂H₂O˙⁺ may be formed, with a small preference for C₂H₄N⁺. This latter product is not formed through a retro Diels Alder reaction in contrast to C₂H₂O˙⁺. The following sequence is proposed for the peak at 42 Da: C₂H₄N⁺ (from N₁–C₂, C₄–C₅ cleavages) > C₂H₂O˙⁺ (from N₃–C₄, N₁–C₂ and C₅–C₆ cleavages) > C₂H₄N⁺ (from N₁–C₂, N₃–C₄ and C₄–C₅) > C₂H₂O˙⁺ (from C₅–C₆, N₁–C₂ and N₃–C₄ cleavages) > NCO⁺ (from N₁–C₂, C₄–C₅ and N₃–C₄ cleavages). Finally the peak at 28 Da is assigned to CNH₂ ⁺ derivatives that can be formed through two different paths, the easiest one requiring 5.4 eV.