Bestimmung der Singulett‐Triplett‐Aufspaltung von Diradikalen mit Hilfe der Sauerstoff‐Abfang‐Technik

Abstract

Determination of the Singlet-Triplet Splitting of Diradicals by Oxygen-TrappingThe diradical 2, generated by thermolysis of Fmethylenebicyclo[3.2.0]hept-l-ene (l), can be trapped by oxygen in the gasphase. From the different trapping rates with and without added SF6 the intersystem crossing rates of the diradical have been deduced. From their temperature dependance the singlet-triplet splitting is calculated to be 7.4 kcal mol-' with the triplet being the ground state. The triplet is protected by an enthalpy barrier of 13.0 kcal mol-against recombination of the unpaired electrons (2-tr-1). From the heat of hydrogenation of 1 the heat of formation of 1. Chem. Ber.

Structural Indicators of Electronic Interaction in the 1,1‘,5,5‘-Tetramethyl-6,6‘-dioxo- 3,3‘-biverdazyl Diradical

“…TME itself appears to have a triplet ground state 4 but probably has a twisted D 2d conformation. 5 The related biradical 2,3-bis(methylene)-1,3-cyclohexadiene, 2, has a nearly planar triplet ground state 6 and the biradicals 2,2-dimethyl-4,5-bis(methylene)-1,3-cyclopentadiene, 7 3, and 2-(1-methyleneethenyl)cyclopentenyl, 8 4, both probably have triplet ground states. The dianion of 9,9′bianthryl has been reported to have a triplet ground state 9 with a D 2d geometry.…”