Regioselective complexation in the 2H-chromene series and studies of theirphotochromic properties

The regioselectivity of the complexation of chromenes with tricarbonyl(tris pyridine)chromium [Cr(CO)(3)Py-3] can be controlled by the addition of BF3. Et2O boron trifluoride etherate, Depending on the molar ratio of the Lewis acid, different complexes can be prepared. The spectrokinetic properties o f the so-formed complexes were studied and it was shown that the thermal bl eaching constants are either more or less reduced, depending on the positio n of the chromium tricarbonyl moiety. Copyright (C) 2000 John Wiley & Sons, Ltd.