Radical cations of phenyl silatrane

Abstract

Electrochemical oxidation of phenylsilatrane (1) in CHCN/0.1 M BuNPF has been studied by voltammetry, UV-Vis and EPR-coupled spectroelectrochemistry supported by DFT calculations. One-electron withdrawal from the HOMO of 1, formed with a predominant contribution of the atrane N atom to the 3c-4e system, results in a short lived radical cation, in which the atrane nitrogen atom is almost planar and carries most of the spin density showing strong coupling with the protons of the axially directed C-H bonds of the three adjacent α-methylene groups (g = 2.0037, aH = 37.93 G, aH = 0.23 G and aH = 1.8 G). EPR spectroscopy and DFT calculations attest that the unpaired electron in the radical cation does not reside at the Si atom.

Synthesis and Electrochemical Study of 1,1′-Thienyl-Substituted Fused Bis-germatranes with a Core 5c-6e Hyperbond

“…10a Studies of the electron transfer aspect of this hyperbond are only at the very beginning, yet already opening many promising features. We have recently shown that when a metallatrane carries a relatively hard to ionize 1-substituent, electron withdrawal upon oxidation can directly affect this hyperbond, resulting in persistent cation radicals [10][11][12] with the spin localized inside the atrane cage on a practically planar N atom. 10c,12 Such systems show a great promise for various modern applications, primarily for spin-commutating interfaces 13 and as potential electromechanical actuators.…”

“…10c,12 Such systems show a great promise for various modern applications, primarily for spin-commutating interfaces 13 and as potential electromechanical actuators. 11,12,14 Driven by the double interest for these compounds and continuing the works on the redox chemistry of intramolecular-coordinated derivatives of the elements of group 14 with pending 15 or included into a rigid structure 10, 11,16 coordinating groups, we envisaged a novel bis-metallatrane system with two fused atrane cages sharing a common nitrogen atom to form a 5c-6e hyperbond capped with two thienyl end-substituents (Scheme 1).…”

Electrooxidation of Hypercoordinated Derivatives of Silicon and Reactivity of Their Electrogenerated Cation Radicals: 1-Substituted Silatranes

“…When the reduction peaks of CRs appeared at v ∼ = 0.1 V s −1 (kinetic parameter λ = kRT/nFv falling in the interval 4 × 10 −3 < λ < 20 [27]), the k of deprotonation was directly derived using Equation (11) [38]: E p = E 0 + 0.78RT/nF − (RT/2nF)ln(λ) (11) When the i p a /i p c ratio in CV fell in the range between 0.25 (1d) and 0.59 (1h) at 1 V s −1 , the rate constant k was determined using the working curve i p a /i p c − log(kτ) (τ is the time elapsed during the scan between E 1/2 and the vertex potential) [36]. For ill-shaped CV peaks, when measuring the E p is difficult, the derived CV (DCV [27]) and two-step potentiostatic chronoamperometry (CA [36]) were used to assess k using inflection potential E i for E p/2 and peak current i [65].…”

“…Therefore, the length of the N→Si contact in the atrane cage (l Si-N ) is directly related to the degree of the involvement of the nitrogen lone pair in the 3c-4e system, and hence to the ease of electron withdrawal (IP and HOMO level). Therefore, the variation of l Si-N caused by the oxidation (destroying the N→Si coordination in 1 +• [11]), i.e., ∆l = l Si-N (1 +• ) − l Si-N (1) (Table 2) is expected to correlate with the reorganization energy of the atrane carcass (λ i ), and further with k s . Then, shifting the process to the zone of ET control (v > 1-2 V s −1 , the rising parts of the ∆E p /∆lg(v) plots (see, e.g., Figure 1B) makes it possible to derive ∆G 0 = from the slope α/E p [38] and to consider the variation in the ET rate k s with the structural changes (l Si-N ) during the oxidation of silatranes.…”

“…c ∆E p /∆log(C) ∼ = 0 for silatranes 1. d From CV and CA; in parentheses the values from EPR spectroscopy. e From Romanovs, V., et al, 2017[11].…”