Highly twisted disilene

Thermochromism was already noted for the first stable disilene l.2a In dialkyl- or bis(trimethylsilyl)diaryldisilenes, the size of the aryl groups affects the thermochromism Tip-substituted ones (9,10) are thermochro-mic,10 while Mes-substituted ones (3,4) are not.9 Interestingly, tetrakisftri-alkylsilyl)disilanes 22 and 23 are highly thermochromic hexane solutions of 22 and 23 are light yellow below 0°C but dark red above 50°C.21 These observations were interpreted in terms of a thermal equilibrium between the bent and twisted conformations. Compound 24, having an absorption band at 480 nm, is dark red in solution even at room temperature. 

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