Molecular Cocrystals of Carboxylic Acids. XXVII An Investigation into the Use of Triphenylphosphine Oxide Cocrystals for Non-Linear Optics: the Crystal Structure of the Adduct of Triphenylphosphine Oxide with N -Methylpyrrole-2-carboxylic Acid

Four adducts of triphenylphosphine oxide with aromatic carboxylic acids have been synthesized and tested for second-order non-linear optical properties. These were with N -methylpyrrole-2-carboxylic acid (1), indole-2-carboxylic acid (2), 3-dimethylaminobenzoic acid (3), and thiophen-2-carboxylic acid (4). Compound (1) produced clear, colourless crystals (space group P 212121 with a 9·892(1), b 14·033(1), c 15·305(1) Å, Z 4) which allowed the structure to be determined by X-ray diffraction.