Designing Linear Hydrogen-Bonded Arrays by Using Substituted Charge-Transfer Complexes. The Crystal Structure of the 1 : 1 Adduct of Indole-2-carboxylic Acid with 3,5-Dinitrobenzoic Acid

Abstract

Five adducts consisting of carboxylic acid-substituted indoles with nitro-substituted benzoic acids have been synthesized and tested for second-order non-linear optical properties. These were indole-2-carboxylic acid with 2,4-dinitrobenzoic acid (1), 3,5-dinitrobenzoic acid (2), and 2,4,6-trinitrobenzoic acid (3), and indole-3-acetic acid with 3,5-dinitrobenzoic acid (4), and 2,4,6-trinitrobenzoic acid (5). Compound (2) produced clear, yellow crystals (space group P ^-1 with a 6·8400(7), b 15·150(2), c 16·097(2) Å, α 84·911(9), β 87·088(10), γ 77·865(9)°, Z 4) which allowed the structure to be determined by X-ray diffraction. Of the five adducts, compounds (3) and (5) gave second harmonic intensities of 0·15 and 0·16 times respectively that of a urea standard.