Structural Reorganizations Control Intermolecular Conductance and Charge Trapping in Paraquat‐Tetraphenylborate Inverse Photochemical Cell

Abstract

Miniaturization of electronic devices to the level of single molecules requires detailed understanding of the mechanisms of their operation. One of the questions here is the identification of the role of structural alterations in charge separation and stabilization in photoactive complexes. To address this question, we calculate optimized molecular and electronic structures, and optical and vibrational spectra of l,l'-dimethyl 4,4'-bipyridinium-bis tetraphenylborate PQ(BPh(4))(2) complex ab initio using density functional theory approach and compare them with the experimentally observed UV-Vis and Raman spectra of the molecules in solid-state films. The results indicate that the association of PQ and BPh(4) leads to the formation of an internally ionized structure that is accompanied by the structural reorganization of both PQ (the twisting of pyridinium rings) and BPh(4) (phenyl rings rotation) moieties. The quanta of light do not seem to be directly involved in the formation of this ionized structure, but provide energy for fast recombination of the separated charges between BPh(4)(-) and PQ(2+). The high efficiency of the dark charge separation and the stabilization of separated charges in the complex permit the using of PQ(BPh(4))(2) in various charge-transfer devices like molecular probes, photovoltaic devices or chemical memory units.

Statistical evaluation of an electrochemical probe for the detection of chlorate

“…Factor C appears independently of interactions with other factors in Figure 4, suggesting that a CA interaction may be responsible at least in part for the non-monotonic behavior of the M i C in the Taguchi design of Table 3. Such behavior is consistent with previous observations of contributions of anion-film age interactions on current responses in paraquat-silicate thin film electrodes [54,56]. Interpretation of the non-monotonic behavior of the M i H in Table 3, however, is complicated by the combined effects of HA interactions, if any, and the HS interaction noted in Figure 4, which is of significant magnitude relative to the H Effect (i.e., 7.98 vs. 11.93, respectively).…”

“…This behavior indicates some restructuring of the films as they age, leading to changes in permeability and mechanical properties reflected in the current response. Similar behaviors have been noted for paraquat-silicate [54][55][56] and polyelectrolyte multilayer [57][58][59][60] films, in which components are usually deposited in kinetically trapped conformations that slowly relax via chemical or physical processes, respectively, to their thermodynamically stable equilibrium conformations as the films age. That similar phenomena related to changes in internal structure occur in our films is also supported by observations of slight changes in film absorbance noted by Fernandes,et.…”

Internal Control of Electron Transfer through a Single Iron Atom by Chelating Porphyrin

“…On the other hand, the lowest unoccupied molecular orbital (LUMO) is delocalized between the two His and iron in the tetrapyrrole ring and only weakly interacts with tetrapyrrole. Since MO delocalization is the main parameter determining the efficiency of ET through the molecule, the LUMO delocalization between His and Fe indicates the possibility for efficient ET through this MO in the direction perpendicular to the porphyrin ring.…”

Analysis of the Resonant Raman Spectra of Viologens and of Their Radical Cations Using Range-Separated Hybrid Density Functionals

“…Often such experimental characterizations are accompanied by computational studies. In the case of (extended) viologens, several theoretical studies have already been achieved about the molecular structure and electronic and magnetic properties ,− but not about the vibronic structure and related properties.…”