Organic Chemistry

Multicomponent Crystals with Two Fast Reorienting Constituents: Mutually Affected Rotation of DABCO and THF


Here we report two new multicomponent supramolecular rotors (1 and 2) based on 2,7-diphenyl-9H-carbazole stators and two rotators brought together by a non-innocent C-HO interaction. This hydrogen bond serves a dual function: it constitutes the rotational axis for THF and acts as a ‘brake’ for the motion of DABCO. Dynamic characterization of 1 by VT 2H NMR experiments supports that DABCO rotates about its supramolecular axis with jumps of 120º (3-fold) and a krot >10 MHz at 300 K, but interestingly, this motion is reduced to 5 MHz at 150 K. Concurrently, the THF experiences an atypical motion on an axis that is perpendicular to that of DABCO, experiencing 180º jumps in the fast regime even at 175 K. 1H(T1) relaxometry studies show that DABCO has an Ea=3.5 kcal/mol, while for THF, an Ea=2.3 kcal/mol was computed by periodic DFT. Fast and organized mobility of two constituents within crystals is extremely infrequent and could have strong implications for future applications of multicomponent solids with regulated dynamics.


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