Photoswitching of the Lewis Acidity of a Catecholborane Bearing an Azo Group Based on the Change in Coordination Number of Boron

Photoisomerization of a catecholborane bearing a 2-(phenylazo)phenyl group with an N−B dative bond caused photoswitching of the coordination
number of boron between 3 and 4. The Lewis acidity of the catecholborane was switched by photoirradiation, and the complexation ability of
the (E)- and the (Z)-isomers of the catecholborane with pyridine differs by more than a factor of 300.