Intermolecular-Type Conical Intersections in Benzene Dimer

Abstract

The equilibrium and conical intersection geometries of the benzene dimer were computed in the framework of the conventional, linear-response time-dependent and spin-flipped time-dependent density functional theories (known as DFT, TDDFT and SF-TDDFT) as well as using the multiconfigurational complete active space self-consistent field (CASSCF) method considering the minimally augmented def2-TZVPP and the 6–31G(d,p) basis sets. It was found that the stacking distance between the benzene monomers decreases by about 0.5 Å in the first electronic excited state, due to the stronger intermolecular interaction energy, bringing the two monomers closer together. Intermolecular-type conical intersection (CI) geometries can be formed between the two benzene molecules, when (i) both monomer rings show planar deformation and (ii) weaker (approximately 1.6–1.8 Å long) C–C bonds are formed between the two monomers, with parallel and antiparallel orientation with respect to the monomer. These intermolecular-type CIs look energetically more favorable than dimeric CIs containing only one deformed monomer. The validity of the dimer-type CI geometries obtained by SF-TDDFT was confirmed by the CASSCF method. The nudged elastic band method used for finding the optimal relaxation path has confirmed both the accessibility of these intermolecular-type CIs and the possibility of the radiationless deactivation of the electronic excited states through these CI geometries. Although not as energetically favorable as the previous two CI geometries, there are other CI geometries characterized by the relative rotation of monomers at different angles around a vertical C–C axis.

Theoretical insights into dopamine photochemistry adsorbed on graphene-type nanostructures

“…[106][107][108][109] Since excited states can be localize on one or the other constituent of the molecule-surface complex, or charges can easily migrate from the molecule to the surface or vice versa, relaxation processes can also occur either on the components separately or even inside the binary system. Accordingly, it was already shown, that non-radiative relaxation can occur either on the graphene surface 110 itself or in the binary complex, [111][112][113][114][115][116][117][118] but at the same time, excited states in the case of slightly modified GrNP can also decay via fluorescence phenomena. 119,120 Given that the relatively moderate size of the chosen graphene model (62 carbon and 22 hydrogen atoms) does not require the use of, e.g., a solid-state based physical model, in the present case the binary molecule-graphene complex will be considered as a macromolecular system with two interacting constituents and treated with the ordinary DFT and TDDFT methods suitable for molecular systems.…”

Light-induced photodissociation in the lowest three electronic states of the NaH molecule

“…Although many of these works treat the dynamical problem of diatomics starting investigations from the simplest hydrogen-like ions or molecules to systems with large numbers of electrons, 1–16 other relevant papers are tackling the problem of photodissociation and fragmentation of polyatomics, as well. 17–36…”

“…Although many of these works treat the dynamical problem of diatomics starting investigations from the simplest hydrogen-like ions or molecules to systems with large numbers of electrons, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] other relevant papers are tackling the problem of photodissociation and fragmentation of polyatomics, as well. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Molecular dissociation is usually treated within the Born-Oppenheimer (BO) framework, which relies on the separation of the motions of the electrons and nuclei due to different time scales of their motion. In most cases, this approach works well and provides an acceptable treatment of dynamical processes.…”

Revealing the Minimum Energy Pathways for Formamide Hydrogenation Reactions in the Presence of Platinum and Platinum–Vanadium Clusters: A Quantum Chemical DFT/Nudged Elastic Band Study

“…An additional goal of this paper is to discuss, in detail, some of the problems arising in the construction of complex MEPs when using the NEB method [36]. This method currently represents a promising trend in computational quantum chemistry and makes it possible to localize intermediate and transition states on a complex potential energy surface [37][38][39]. The authors have previously successfully applied this relatively new method in [35,40].…”