Chiral properties of tetrathiatriarylmethyl spin probes

Abstract

We report that tetrathiatriarylmethyl (trityl) EPR probes are chiral molecules at room temperature, the two stereoisomers that differ in their helicity being configurationally stable enough to be separated and stored independently.

Triarylmethanols with Bulky Aryl Groups and the NOESY/EXSY Experimental Observation of a Two‐Ring‐Flip Mechanism for the Helicity Reversal of Molecular Propellers

“…7), the paramagnetic analogue of 1 . [16] The experimental and calculated activation enthalpies resulted from our kinetic studies match fairly well the value of Δ H ≠ , which may be derived from the original literature data reported for 7 . In accordance with eq.…”

“…This means much shorter half-life for racemization (τ 1/2 = ln2/2 k enant,298 = 8.4 h) in comparison with that for the paramagnetic analogue (28.6 days in ethyl acetate solution [16] ), but it is sufficient to provide the isolation of enantiomerically pure isomers of 1 with of the use of CSP HPLC technique. Thus, a procedure applied by authors of ref.…”

“…Thus, a procedure applied by authors of ref. 16 to resolution of racemic triarylmethanol 1 (column temperature 25 °C, elution over 10 min, immediate freezing the collected fractions at −78 °C) potentially must afford the individual stereoisomers of 1 with optical purity better than 99% ee . In fact it was 100 % ee within error limits of CD optical density measurements.…”

EPR Imaging Spin Probe Trityl Radical OX063: A Method for Its Isolation from Animal Effluent, Redox Chemistry of Its Quinone Methide Oxidation Product, and in Vivo Application in a Mouse

“…In Finland trityl, the parent congener of OX063, the three aryl units have a propensity to adopt a C 3 symmetric arrangement, with the aryl units canted parallel to one another, analogous to that found in a three-bladed propeller. 19–21 The greater steric congestion combined with possible hydrogen bonding interactions may allow the three aryl units of OX063 to exist in either fully parallel arrangement or with two of the aryl units parallel and one anti-parallel.…”

Exchange Phenomena in the Electron Paramagnetic Resonance Spectra of the Nitroxyl and Trityl Radicals: Multifunctional Spectroscopy and Imaging of Local Chemical Microenvironment

“…5 Conformational studies using EPR spectroscopy, DFT calculation, and X-ray diffraction have shown that the TAMs adopt a helix conformation (Scheme 2) which protects the central carbon bearing approximately 60% of the unpaired electron spin density 66 and provides helicoidally chirality to the EPR spin probe. 67,68 …”