L-Arginine nitrates

In the L-Arg þ HNO3 þ H2O system, where Arg stands for arginine (þ(H2N)2CNH(CH2)3CH(NH2)COO2), crystals of 2(LArg ·HNO3)·H2O (or formal L-Arg·HNO3·0.5H2O) (I) and L-Arg·2HNO3 (II) compounds have been produced. The structures of both compounds were solved by X-ray crystallography. The asymmetric part of the triclinic unit cell (space group P1) of the (I) compound contains two monocharged arginine cations (Argþ), two nitrate ions and a water molecule interacting through hydrogen bonds. The monoclinic unit cell of the (II) compound (space group P21) is composed of two crystallographically independent nitrate ions and one doubly charged arginine cation hydrogen bonded to nitrate groups. The Argþ cations are hydrogen bonded to each other, while the Arg2þ cations do not interact. In addition the crystal of compound (II) emits phase matched second harmonic generation signal of a Nd:YAG laser. q 2003 Elsevier B.V. All rights reserved.