Muriel Bagieu-Beucher

Crystal structure of anhydrous bismuth iodate, Bi(IO3)3

Bismuth iodate was synthesized by precipitation from bismuth nitrate and iodic acid. The powder was dissolved in dilute nitric acid and single crystals were obtained by slow evaporation at 70°C. Bi(IO3)3 crystallizes in the monoclinic system, space group P21/n (N° 14), a = 8.8882(2) Å, b = 5.9445(2) Å, c = 15.2445(5) Å, β = 97.064(1) Å. BiO9 polyhedra are edge-connected forming chains parallel to the b axis; these chains are linked through (IO3) groups forming layers parallel to (101). The 3D framework is designed by linking these layers through long I–O bonds. DSC analysis shows a remarkable thermal stability.

Sodium 4-nitrophenolate 4-nitrophenol dihydrate crystal: a new herringbone structure for quadratic nonlinear optics

Sodium 4-nitrophenolate 4-nitrophenol dihydrate is a new nonlinear optical crystal of C2 monoclinic symmetry composed of two distinct organic chromophores of respective calculated molecular hyperpolarisabilities β xxx =18.2×10 –30 and 5.2×10 –30 esu. The chromophores are organised in herringbone motifs along inorganic chains of NaO6 edge shared octahedra. A short H-bond network assembles the herringbone motifs. A remarkable feature is the unique proton shared between the two chromophores respecting the twofold symmetry. The structure is isotypic with that of the magnesium bis(4-nitrophenolate) dihydrate. Structural analogies with other known metal nitrophenolates are pointed out and the nonlinear optical efficiency is discussed.

A new octupolar material for quadratic nonlinear optics: tris(2,2′-bipyridyl)Zn(II) tetrakis(2-chloro-4-nitrophenolate)Zn(II)

Tris(2,2′-bipyridine)Zn(II) tetrakis(2-chloro-4-nitrophenolate)Zn(II), [Zn(bpy)3][Zn(CNP)4] 1, is a new octupolar material for quadratic nonlinear optics. 1, a chiral metal–organic complex, crystallizes in space group C2. Refinement of the Flack parameter supports the description of the [Zn(bpy)3]2+ cation as the Δ enantiomer. The counterion is an octupolar, tetrahedral assembly of 2-chloro-4-nitrophenolate chromophores around a Zn2+ ion. A second harmonic generation signal equal to 5 × urea is observed. A complex having a slightly different stoichiometry, bis(2,2′-bipyridine)-bis(2-chloro-4-nitrophenolate)Zn(II), crystallizes in the centrosymmetric space group P. The structure of bis(2-chloro-4-nitrophenolate)Zn(II) pentahydrate, a precursor of 1 with P symmetry, is described.

Sodium 3-methyl-4-nitrophenolate dihydrate: a crystal engineering route towards new herringbone structures for quadratic non-linear optics

Abstract Sodium 3-methyl-4-nitrophenolate dihydrate (Na3M4NP) is a new stable non-linear optical crystal of Cc monoclinic symmetry. The organic anions having an average calculated molecular hyperpolarisability β xxx ≈20×10 −30 esu are organised in a herringbone motif, inducing, together with water molecules, a very dense packing of NaO 6 edge shared octahedra. A three-dimensional network of homogeneous and short hydrogen bonds close-packs the herringbone motifs in a staggered arrangement. The crystal structure is simply described and explained in relation to basic inorganic structural models.

1,3-Dibromo-2,4,6-trinitrobenzene (DBTNB). Crystal engineering and perfect polar alignment of two-dimensional hyperpolarizable chromophores.

1,3-Dibromo-2,4,6-trinitrobenzene (DBTNB), a two-dimensional charge transfer hyperpolarisable chromophore, crystallizes in the non-centrosymmetric space group C2 in perfect polar order leading to an intense powder SHG signal at 1.06 microns.

Crystal engineering strategy of thiocyanates for quadratic nonlinear optics. Hg3CdCl2(SCN)6 and Hg4CdBr4(SCN)6

Abstract The noncentrosymmetric crystals Hg 3 CdCl 2 (SCN) 6 and Hg 4 CdBr 4 (SCN) 6 with, respectively, R3c and Fmm2 space group symmetry have been synthesised suggesting an engineering route of nonlinear optical crystals with a large transparency bandwidth. The structures have been solved in order to valuate their nonlinear optical efficiency in relation with the orientation of SCN chromophores in each crystal symmetry.

Crystal engineering of two-dimensional polar layer structures: hydrogen bond networks in some N-meta-phenylpyrimidinones

In a recent paper (New J. Chem., 2001, 25, 1520), we have analysed crystal structures of some N-aryl pyrimidinones. Based on the occurrence of two-dimensional layers in six out of nine crystals, we proposed that self-assembly in these structures might be analysed in terms of the stacking of 2D hydrogen-bonded layers. We show herein that meta-substituted phenyl pyrimidinones (Br, I, F, NO2, Me, OMe) have an overwhelming preference for the 2D polar arrangement, namely the parallel alignment of 1D chains within a layer. The molecules are arranged in chains mediated by C–H⋯O hydrogen bonds and such motifs are connected via C–H⋯O and C–H⋯halogen interactions in the lateral direction. A notable feature in these structures is that chains of dipolar molecules align in a parallel fashion to produce polar layers. The preference for 2D polarity is explained by the shape of the aryl pyrimidinone molecule and the geometry of interactions between hydrogen bonding functional groups (C–H donors, O/halogen acceptors). However, the polar layers stack in an anti-parallel manner and the crystal structures are centrosymmetric. The task of controlling parallel stacking of polar domains in the 3D crystal is a continuing challenge in our studies.

Crystal engineering of neutral N-arylpyrimidinones and their HCl and HNO3 adducts with a C–H⋯O supramolecular synthon. Implications for non-linear optics

In a previous crystallographic study of some N-arylpyrimidinones 1, we noted that: (1) C–H⋯O hydrogen bonds connect molecules in a linear array; (2) the charge transfer axis of the chromophore is aligned with the main symmetry operator of point groups 2 or m at ca. 57°, a value that is close to the ideal angle of 54.74°; (3) the methyl and chloro derivatives are isostructural. In this paper, we report the characterisation of chloride and nitrate salt adducts of 1 by X-ray diffraction and the analysis of their packing motifs. Recurrence of the same C–H⋯O supramolecular synthon in three neutral and five HCl and HNO3 adducts of 1 signifies the robustness of this weak hydrogen bond. The occurrence of a mirror plane m in a family of eight crystal structures (four Pnma, two P21/m, one Pbcm, and one Pmn21) is unusual because this symmetry operation is generally avoided due to close packing considerations. Ab initio calculations show that the bisected phenyl conformation present in these crystal structures is the most stable conformation of the pyrimidinone molecule. The presence of aryl and pyrimidinone chromophores in 1, the correct alignment of the aromatic ring in the crystal and the occurrence of 2D polar layers in some crystal structures are favourable factors for non-linear optical applications. However, a strategy for the crystallisation of these achiral molecules in non-centrosymmetric space groups is yet to be achieved. This crystal engineering study simplifies the challenge of complete 3D structural control into a modular 2D+1D problem.

Engineering of non-linear optical crystals displaying a quasi perfect polar alignment of chromophores

Four non-linear optically active crystals based on organic salts obtained by bis-protonation of four diamines (trans-(±)-1,2-, trans-(1R,2R)-(–)-, cis-1,2-diaminocyclohexane or R-(–)-2-methylpiperazine) by 2-methoxy-4-nitrophenol have been prepared. Their crystal structures and non-linear optical efficiencies have been studied. The two adjacent proton acceptor sites in 1,2-diaminocyclohexanes play an important role in aligning the 2-methoxy-4-nitrophenolate chromophores in a quasi-perfect polar arrangement by anchoring through short hydrogen bonds. In the case of the methylpiperazinium derivative the symmetrical 1,4 location of proton acceptor sites directs the chromophores to near antiparallel alignment by forming short hydrogen bonds. The second harmonic generation efficiencies at 1.064 µm of Nd 3+ :YAG laser light are equivalent to that of POM (3-methyl-4-nitropyridine-1-oxide) for the three diammoniocyclohexane derivatives and equivalent to twice that of urea for the methylpiperazinium derivative.

Erbium cyclo-hexaphosphate decahydrate: Er2P6O18 · 10H2O

Crystal data and atomic arrangement are given for a new rare-earth cyclo-hexaphosphate decahydrate: Er2P6O18 · 10H2O. This compound is monoclinic P21a, with a = 18.315(8), b = 13.343(4), c = 11.211(4) A, b = 94.46(3)⊃, Z = 4, V = 2681 (3) A3. The crystal structure was determined with a final R = 0.032 for 4897 independent reflections. It can be described as a succession of thick corrugated layers of alternated P6O18 rings and ErO8 polyhedra with wide channels where non-bonded water molecules are located. The phosphoric ring anion has no internal symmetry. The erbium polyhedra do not share any edge or corner.