H.A. Karapetyan

Growth and investigation of new non-linear optical crystals of LAP family

Abstract The possibility of preparing new analogs of L-arginine phosphate monohydrate, (LAP), has been investigated. Single crystals of the compound L-Arg·HCOOH, which had earlier been obtained in powdered form, were successfully grown during the course of this investigation. In addition, we have found that there is a class of compounds having the Arg·2Ax composition, (where Ax is one of several inorganic or organic acids). Such compounds (Arg·2HIO 3 , Arg·2HNO 3 , Arg·2H 3 PO 4 , Arg·2HF, Arg·2HCl·H 2 O, and Arg·2HBr·H 2 O) have been synthesized and single crystals grown. The crystals grown in this investigation were studied by IR and X-ray diffraction methods. The influence of the different amino acid groups on crystal symmetry and the influence of this symmetry on non-linear optical properties are discussed.

New class of nonlinear optical crystals among arginine salts

A considerable number of new crystalline compounds were prepared by reacting L-arginine (L-Arg) with a series of inorganic and organic acids. In addition to the usual arginine slats with composition L-Arg-HX, where HX represents various acids, an entirely new class of crystal with the composition L-Arg 2HX was discovered. Due to the presence of the optically active L-arginine component, all these crystal had non-centro-symmetric structures. Most of the crystal prepared in this study gave strong phase-matched second harmonic generation signals with a Nd:YAG laser, and some appear quite promising for nonlinear optical applications.

1-Substituted derivatives of 2-phenylpyrrolidine-2-carboxamide.

The structures of two potential anti-human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTI), namely 1-(2-chlorobenzoyl)-2-phenylpyrrolidine-2-carboxamide, C(18)H(17)ClN(2)O(2), and 1-(2-furoyl)-2-phenylpyrrolidine-2-carboxamide, C(16)H(16)N(2)O(3), have been investigated by X-ray diffraction and the butterfly-like conformation established in each case. The pyrrolidine ring has the same half-chair conformation in both structures.

1-Substituted derivatives of 2-aryl-5-oxopyrrolidine-2-carboxylic acid

The structures of two potential anti-human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTI), namely 1-benzyl-5-oxo-2-phenylpyrrolidine-2-carboxamide, C(18)H(18)N(2)O(2), (III), and 2-(4-isopropoxyphenyl)-5-oxo-1-(4-tolyl)pyrrolidine-2-carbonitrile, C(21)H(22)N(2)O(2), (IV), have been investigated by X-ray diffraction, confirming the butterfly-like conformation of both compounds. The pyrrolidine ring is in an envelope conformation in (III) and a half-chair conformation in (IV). Two intermolecular N[bond]H...O hydrogen bonds are present in the crystal structure of (III), with N...O distances of 2.995 (2) and 2.927 (2) A.

l-Argininium ethyl sulfate

The title compound, C6H15N4O2 +·C2H5O4S−, exhibits nonlinear optical properties. An extensive hydrogen-bonding network [N⋯O = 2.786 (4)–3.196 (5) Å] links cations and anions into a three-dimensional structure.

l-2-Nitrimino-1,3-diazepane-4-carboxylic acid.

The cyclic form of l-nitroarginine, C6H10N4O4, crystallizes with two independent molecules in the asymmetric unit. According to the geometrical parameters, similar in both molecules, the structure corresponds to that of l-2-nitrimino-1,3-diazepane-4-carboxylic acid; there are, however, conformational differences between the independent molecules, one of them being close to a twisted chair while the other might be described as a rather flattened boat. All six active H atoms in the two molecules are involved in hydrogen bonds, two of which are intramolecular and four intermolecular, forming an infinite chain of molecules along the b axis.

1,2,5-Substituted derivatives of 2-phenylpyrrolidine.

The structures of the potential anti-human-immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTI) 1-tert-butoxycarbonyl-2-phenylpyrrolidine-2-carboxylic acid, C(16)H(21)NO(4), (I), and 2-ammoniomethyl-1-benzyl-5-oxo-2-phenylpyrrolidine chloride, C(18)H(21)N(2)O(+).Cl(-), (II), have been investigated by X-ray diffraction. The investigations confirm a butterfly-like conformation for both compounds. In (I), the pyrrolidine ring has a marked half-chair conformation, while it has a weakly pronounced envelope conformation in (II). Intermolecular hydrogen bonds, viz. O-H.O in (I), and N-H.O and N-H.Cl in (II), build infinite chains in both structures. Rotational disorder of the three methyl groups is observed in (I).

Potassium l-2-nitrimino-1,3-diazepane-4-carboxyl-ate monohydrate.

The title compound, K+·C6H9N4O4 −·H2O, crystallizes with the K atoms located on special positions related by pseudocentres of symmetry. Each K atom is coordinated by six O-atom donors. The N and water H atoms are involved in inter- and intramolecular N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonding. The data indicate inversion twinning.

l-2-Nitrimino-1,3-diazepane-4-carboxylic acid monohydrate.

The title compound, C6H10N4O4·H2O, crystallizes with two independent formula units in the asymmetric unit, their geometric parameters being quite similar. The conformations of the 1,3-diazepane rings are also similar and close to a twist-boat. All ten O- and N-bound H atoms are involved in hydrogen bonds, two of which are intra- and eight intermolecular linking crystallographically independent molecules, into a three-dimensional hydrogen-bonded network.