Institut für Organische Chemie der Universität, Am Hubland, D-97074 Würzburg, Germany, Fax: (+49) 931-888-4606.
Angew Chem Int Ed Engl. 1999;38(8):1064-7. doi: 10.1002/(SICI)1521-3773(19990419)38:8<1064::AID-ANIE1064>3.0.CO;2-U.
The UV/Vis spectra of thermochromic semibullvalenes 1 and barbaralanes recorded at various temperatures yield enthalpy differences between the two degenerate classical structures 1 and 1' and the less stable species (1*) that absorb at long wavelengths. The latter species are interpreted in terms of higher, delocalized states that are located just above the flat potential energy barrier between the ground states (ΔH(0) =11 (R=H; in butyronitrile), 1 kJ mol(-1) (R=Ph)).
热致变色半环辛烯 1 和巴尔巴拉烷的 UV/Vis 光谱在不同温度下记录，得出了两个简并经典结构 1 和 1'与吸收长波长的较不稳定物种（1*）之间的焓差。后一种物种可以用位于基态之间的平坦势能垒（ΔH(0)=11（R=H；在丁腈中），1 kJ/mol(-1)（R=Ph））之上的更高离域态来解释。
