Solubility and specific heat properties of the semiorganic nonlinear optical crystal, L-arginine hydrocholorobromide (LAHClBr), have been measured as a function of temperature. The compound crystallizes in a rectangular bipyramidal shape with well-developed {100} and {001} pinacoids. X-ray diffraction analysis shows that it belongs to the space group P2 1 with two independent molecules in asymmetric units and lattice parameters a = 11.158(2) A, b = 8.579(3) A, c = 11.235(3) A, β = 91.55°(4). The arginine molecules occur as zwitterions, with the amino groups and the guanidyl groups each accepting a proton from the acid groups present in the molecule. The molecules are held together by a three-dimensional network of hydrogen bonds.

Morphology, crystal structure, and thermal and spectral studies of semiorganic nonlinear optical crystal LAHClBr

Analogue reaction systems of selenate reductase, which reduces substrate in the overall enzymatic reaction SeO42- + 2H+ + 2e- → SeO32- + H2O, have been developed using bis(dithiolene) complexes of ...

Analogue reaction systems of selenate reductase.

A series of metal–organic supramolecular co-ordination polymers [Zn(HPO4)(Hpytz)] (1), [Cd(Hpytz)2(H2PO4)2(H2O)2] (2), [Zn(pytz)2(H2O)4]·2H2O (3) [pytz− = 5-(4-pyridyl)tetrazolate], [M(tzpyo)2(H2O)4] [M = Zn (4), Ni (5)] [tzpyo− = 4-tetrazolate-pyridine N-oxide] incorporating tetrazolyl ligands have been synthesized via in situ [2 + 3] cycloaddition reactions of 4-cyanopyridine, 4-cyanopyridine N-oxide with sodium azide in the presence of zinc, cadmium or nickel salts under hydrothermal reaction conditions at 130–160 °C. Use of higher temperatures leads to hydrolysis of nitriles to carboxylates and subsequently to decarboxylation, resulting in two unexpected byproducts, [inaH]+(NO3−) (6) [ina = isonicotinic acid] and [(4,4′-bipyH2)(H2PO4)2(H2O)2] (7). Single crystal X-ray structure analyses of 1 and 2, prepared under hydrothermal conditions in the presence of H3PO4, reveal κ1-co-ordination of the N-donor at the 2-position of the tetrazolyl ligands binding in a TZ-mode. The pyridyl N-centres in 1 and 2 are protonated resulting in the formation of Npy–H⋯O hydrogen-bonds within the solid-state structures. In the absence of H3PO4 similar hydrothermal reactions afforded 3, in which the pyridyl group is directly bound to Zn(II) and tetrazolate-ring is unco-ordinated (PY-mode). Single crystal X-ray structures of 4 and 5 show a TZ-binding mode analogous to that for 1 and 2, with the pyridyl N-oxide moiety forming hydrogen-bonds with co-ordinated water molecules to give supramolecular pillar-layered frameworks. Complex 2 exhibits a distorted 6-connected α-Po net of 412·63 topology; 3 possesses an attractive 3D (4,5,10)-connected trinary (3·42·53)2(3·44·54·6)4(32·48·514.612·77·82) net, while the isostructural complexes 4 and 5 show 3D (4,8)-connected layer-pillared network structures with a unique (46)2(412·612·84) topology. In 6, all hydrogen atoms of inaH+ cations are involved in the formation of hydrogen-bonds with either nitrate or other inaH+ cations resulting in a 2D (4,6)-connected binary net with (32·42·52)(34·44·54·63) topology. In 7, the dihydrogenphosphate anions are arranged viahydrogen-bonds into an unusual (4,4) grid-type sheet, and these layers are further pillared by organobipyridine cations to form a 3D open framework with channels occupied by helical chains of water dimers. The thermal stability of these metal-tetrazolate complexes has been studied by TGA and powder X-ray diffraction, and the effect of proton source (H3PO4) on the co-ordination mode of these tetrazolyl ligands is discussed.

In situ synthesis of 5-substituted-tetrazoles and metallosupramolecular co-ordination polymers

Synthesis, crystal growth and characterization of a new organic NLO material: Caffeinium picrate (CAFP)—A charge transfer molecular complex salt

Synthesis, structural, thermal, mechanical, second harmonic generation efficiency and laser damage threshold studies of 4-dimethylaminopyridinium-3,5-dicarboxybenzoate trihydrate single crystal

In the title compound, C5H14N3+·H2PO4−, the cation has a central guanidinium fragment with a planar geometry, as expected for a central Csp2 atom with a small charge delocalization along the three C—N bonds. The crystal packing is governed by hydrogen bonds so that the phosphate anions are linked head to tail, forming chains running parallel to the c direction. These chains in turn are interconnected by hydrogen bonds to intermediate tetra­methyl­guanidinium cations forming hydrogen-bonded molecular layers stacked parallel to the bc crystal planes.

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1,1,3,3-Tetramethylguanidinium dihydrogenorthophosphate

l-Argininium hydrogen selenite (C6H15N4O2HSeO3) is a new semiorganic compound of the hydrogen selenite family with non-linear optical properties. The crystal lattice is monoclinic with unit-cell parameters a = 22.493 (5), b = 5.1624 (13), c = 9.730 (4) A, β = 95.68 (3)°, V = 1124.3 (6) A3, Z = 4, space group C2. Second-harmonic generation measurements performed on powder samples, using a Q-switched Nd:Yag laser (λ = 1064 nm), showed the second-harmonic power to be about twice that of urea. Differential scanning calorimetry measurements revealed the existence of a phase transition with onset at 289 K.

I.M.L. Fernandes

Papers

1,1,3,3-Tetramethylguanidinium dihydrogenorthophosphate

Synthesis, structure, thermal and non-linear optical properties of l-argininium hydrogen selenite