Halochrome Molekeln 2. Mitteilung [1] Synthese und acidobasisches Verhalten substituierter 6,6‐Diphenyl‐6 H ‐chromeno [4,3‐ b ]indole

Halochromic Molecules, Synthesis and Acidobasic Behaviour of Substituted 6,6‐Diphenyl‐6 H ‐chromeno [4,3‐ b ]indoles Substituted 6,6‐diphenyl‐6 H ‐chromeno [4,3‐ b ]indoles are forming with acid ring‐opened, intensely coloured diphenyl‐indol‐3‐yl‐carbenium salts. The preparation of these products is described and the UV./VIS.‐spectra are discussed. An investigation of the halochromic properties is made by spectrophotometric determination of ϵ pH *‐ and ϵ H0 *‐curves in buffered methanol/water solutions. p K *‐ and p K *‐values respectively are calculated and the suitability of substituted 6 H ‐ chromeno [4, 3‐ b ]indoles as chromogens in self‐duplicating stationery is discussed.