Halochrome Moleküle 9. Mitteilung[1]. Substituierte 6,11‐Dihydrospiro[[1]benzopyrano[4,3‐ b ]indol‐6,9′‐9′ H ‐xanthen]‐2′,6′‐diamine und ihre Aza‐analogen: Neue Chromogene für schwarze Farbbilder

Halochromic Molecules. Substituted 6,11‐Dihydrospiro[[1]benzopyrano[4,3‐ b ]indol‐6,9′‐9′ H ‐xanthene]‐2′,6′‐diamines and Their Aza Analogues: New Chromogenes for Black Images . We have synthesized a series of substituted 6,11‐dihydrospiro[[1]benzopyrano[4,3‐ b ]indo1‐6,9′‐9′ H ‐xanthene]‐2′,6′‐diamines and their respective aza analogues. These compounds develop a black colour in acidic media. The assumed structures of the analytically pure starting and final products are consistant with the fragmentations in the MS and are also supported by FT 1 H‐NMR. The UV/VIS spectra in buffered MeOH/H 2 O solutions were measured. From the ϵ pH * curves, we determined the p K * values. The title compounds can be used in so‐called pressure‐sensitive copying systems.