Synthesis and characterization of alkali-stable bridged phthalein dyes and an investigation of the regiochemical effects on their near-IR absorbance

Abstract

Novel bridged phthalein dyes substituted with a diisopropylamide ortho to the bridge are stable at high pH; with a chromogenically active auxochrome ortho to the meso carbon, a hypsochromic shift, band narrowing, and an increased molar absorptivity of the near-infrared absorbance are observed relative to the regioisomer in which the chromogenically active auxochrome is para.