Charge-Transfer-to-Solvent-Driven Dissolution Dynamics of I^-(H₂O)_2-5upon Excitation:  Excited-State ab Initio Molecular Dynamics Simulations

Abstract

In contrast to the extensive theoretical investigation of the solvation phenomena, the dissolution phenomena have hardly been investigated theoretically. Upon the excitation of hydrated halides, which are important substances in atmospheric chemistry, an excess electron transfers from the anionic precursor (halide anion) to the solvent and is stabilized by the water cluster. This results in the dissociation of hydrated halides into halide radicals and electron-water clusters. Here we demonstrate the charge-transfer-to-solvent (CTTS)-driven femtosecond-scale dissolution dynamics for I-(H2O)n=2-5 clusters using excited state (ES) ab initio molecular dynamics (AIMD) simulations employing the complete-active-space self-consistent-field (CASSCF) method. This study shows that after the iodine radical is released from I-(H2O)n=2-5, a simple population decay is observed for small clusters (2 </= n </= 4), while rearrangement to stabilize the excess electron to an entropy-driven structure is seen for n = 5. These results are in excellent agreement with the previous ultrafast pump-probe experiments. For the first approximately 30 fs of the simulations, the iodine plays an important role in rearranging the hydrogen orientations (although the water network hardly changes), which increases the kinetic energy of the cluster. However, approximately 50 fs after the excitation, the role of the iodine radical is no longer significant. After approximately 100 fs, the iodine radical is released, and the solvent molecules rearrange themselves to a lower free energy structure. The CTTS-driven dissolution dynamics could be useful in designing the receptors which are able to bind and release ions in host-guest chemistry.

Time-resolved radiation chemistry: Dynamics of electron attachment to uracil following UV excitation of iodide-uracil complexes

“…35,[44][45][46] Comparison to theory suggests that these shifts result from two effects: the excited state interaction of the neutral iodine atom with the diffuse electron associated with the nascent negative ion formed by photoexcitation, 47 and, in the case of multiple solvating species, solvent motion driven by the injection of the excess electron into the solvent network. [48][49][50][51][52] For a binary complex such as I -U, only the first mechanism is operative. Therefore, neutral iodine motion relative to the DB orbital of the uracil anion is likely responsible for the dynamics in Figure 3.…”

Disulfuric acid dissociated by two water molecules: ab initio and density functional theory calculations

“…1 The dissociation and deprotonation phenomena of solute molecules are highly complicated phenomena. As such, a number of studies have been reported on diverse cations, [2][3][4][5][6] anions, 7,8 acids, [9][10][11][12][13][14][15][16][17][18][19][20][21][22] bases, 23,24 salts [25][26][27] as well as aromatic and biomolecules [28][29][30][31] hydrated by various numbers of water molecules. In particular, hydration of acids is of importance in the aerosol nucleation process in the atmosphere.…”

Coordinate space translation technique for simulation of electronic process in the ion–atom collision

“…To this end, the first principle solvated electron dynamics simulations, 1 excited state ab initio molecular dynamics simulations, [2][3][4] and ion-atom collision time-dependentdensity-functional theory (TDDFT) simulations [5][6][7][8] have been reported. To this end, the first principle solvated electron dynamics simulations, 1 excited state ab initio molecular dynamics simulations, [2][3][4] and ion-atom collision time-dependentdensity-functional theory (TDDFT) simulations [5][6][7][8] have been reported.…”