SYNTHESIS AND CHARACTERIZATION OF ALKALI-STABLE BRIDGED PHTHALEIN DYES AND AN INVESTIGATION OF THE REGIOCHEMICAL EFFECTS ON THEIR NEAR-IR ABSORBENCY

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