The synthesis and properties of naphthopyran– boradiazaindacene conjugates

Three new 3,3-diaryl-3H-naphtho[2,1-b]pyran–boradiazaindacene conjugates have been synthesised. The naphthopyran–boradiazaindacene conjugates exhibit a weaker photochromic response relative to the simple naphthopyrans with the photomerocyanines fading relatively quickly. Photochromic switching of the naphthopyran unit results in a decrease in the fluorescence intensity for only the most persistent photomerocyanine. A crystal structure shows that the units are essentially orthogonally disposed and that the boradiazaindacene core is extensively delocalised.