Oriented External Electric Fields Affect Rate and Stereoselectivity of Electrocyclic Reactions

Abstract

We carried out a computational investigation at the density functional theory (M06-2X) level on the effects of oriented external electric fields (OEEF) on activation barriers and stereochemical output of the thermal ring opening of 3-substituted cyclobutenes (C4H5X) to butadienes. It is well known that with πelectron-donor substituents (X = CH 3 , NH 2 ), the conrotatory outward rotation is preferred, while with π-electron-acceptor substituents (X = CHO, NO, BH 2 ), the conrotatory inward process becomes favored. In the presence of the OEEF applied along the three axes x, y, and z in either positive or negative direction, for both π-donor and π-acceptor substituents, we observed either catalysis or inhibition. Both effects were consistent with the change of the induced dipole along the direction of the applied field. An interesting effect was observed for X = CHO and NO. The simultaneous catalysis and inhibition of the outward and inward transformation leads to a reversed ratio between outward and inward transformation, with the former being favored (stereochemical inversion). Such effect was not observed for X = BH 2 (the strongest π-acceptor examined here). In this case, in the absence of the applied field, the difference between the inward and outward barriers is too large and the simultaneous catalysis and inhibition of the outward and inward transformation is not capable of determining the stereochemical inversion.

Cisplatin under oriented external electric fields: A deeper insight into electrochemotherapy at the molecular level

“…Consequently, the geometric and electronic modification of cisplatin under different oriented external electric fields (OEEFs) has been detailedly studied in this work. It is recently reported that OEEFs can cause structural distortions, 18,19 induce proton transfer, 20,21 modulate NLO responses of materials, 22,23 and catalyze various reactions as smart catalysts and controllers of reaction mechanisms 24–33 . Herein, we will mainly focus on the following two questions: (a) What is the influence of OEEFs on the geometric and electronic structure of cisplatin?…”

“…It is recently reported that OEEFs can cause structural distortions, 18,19 induce proton transfer, 20,21 modulate NLO responses of materials, 22,23 and catalyze various reactions as smart catalysts and controllers of reaction mechanisms. [24][25][26][27][28][29][30][31][32][33] Herein, we will mainly focus on the following two questions: (a) What is the influence of OEEFs on the geometric and electronic structure of cisplatin? (b) How does the OEEF-induced geometric and electronic modification improve the antitumor activity of cisplatin in electrochemotherapy?…”

Enhanced Organic Photocatalysis in Confined Flow through a Carbon Nitride Nanotube Membrane with Conversions in the Millisecond Regime

“…First, in the studied photocatalytic reactions, it induces polarization of molecules, which in turn enhances their reactivity. The profound impact of the electric field, in particular an oriented external electric field, on the reactivity of molecules has been studied theoretically and confirmed experimentally. − Second, the concentration of the internal electric field in the nanotube induced by the confinement effect facilitates separation of the photogenerated charge carriers and extends their lifetime (Figure f). As a result, photogenerated electrons and holes are utilized more efficiently, which leads to a higher AQY (Figure d).…”

Twistable dipolar aryl rings as electric field actuated conformational molecular switches

“…This is in line with the acknowledged importance of the induced dipole in tuning the catalytic effect of external fields in reactivity. 28,52 For the highest strength E-field considered of 1.5 × 10 8 V/cm, the energy lowering from the induced dipole is more than double the maximum energy variation due to the permanent dipole. Overall, in all systems the energy lowering effect of the induced dipole acts to: i) increase the energy lowering of the permanent dipole when the molecular dipole is aligned with Fx, and ii) largely cancel the energetically destabilising effect of the permanent dipole (or even reverse it at high field) when the molecular dipole is anti-aligned with Fx.…”