René Masse

A new approach in the design of polar crystals for quadratic nonlinear optics exemplified by the synthesis and crystal structure of 2-amino-5-nitropyridinium dihydrogen monophosphate (2A5NPDP)

Abstract2-amino-5-nitropyridinium dihydrogen monophosphate exemplifies a new crystal engineering strategy combining mineral and organic moieties towards enhanced quadratic nonlinear optical properties. This strategy is meant to combine the advantages of mineral ionic structures (cohesion, stability, optical and other damage resistance) with those of organic molecules (structural flexibility, high optical polarizability). This organic inorganic material is designed so as to favour mutual dipolar interactions between the 2-amino-5-nitropyridinium cations and the (H2PO4−)n subnetwork interlocked by hydrogen bonding in the same crystalline lattice. This approach rests on the structural features and chemical properties of (H2PO4−)n polyanion. The 2A5NPDP structure reveals a polar layered arrangement. The high powder SHG efficiency of 2A5NPDP, comparable to that of state-of-the-art purely organic 3-methyl-4-nitropyridine-1-oxide (POM) crystals, confirms the validity of this approach, currently generalized to a large variety of mixed organo-mineral crystals.

Crystal engineering and structural investigations of the 2-amino-5-nitropyridinium salts C5H6N3O2+.HSO4− and C5H6N3O2+.H2AsO4−

The aim of studying the encapsulation of 2-amino-5-nitropyridinium cations in (HSO 4 - ) n and (H 2 AsO 4 - ) n polymeric host matrices is to build acentric frameworks that are efficient for quadratic nonlinear optical applications. Evidence is given for the role of inorganic polyanions in the formation of polar packings and this is discussed on the basis of X-ray crystal structure investigations. C 5 H 6 -N 3 O 2 + .HSO 4 - is orthorhombic, Pcab, with a=29.617 (9), b=13.185 (3), c=9.013 (2) A, Z=16: the crystal structure has been solved using direct methods and difference Fourier syntheses, with a reliability factor R=0.049 for 2483 independent reflections

Structural evidence in 2-amino-5-nitropyridinium halides (Cl–, Br–) of herringbone motifs favourable to efficient quadratic non-linear optical properties

2-Amino-5-nitropyridinium halides have been synthesized and their crystal structures determined. The structures of acentric phases reveal networks of non-linear chromophores arranged in herringbone motifs. Their secondharmonic generation responses vary in magnitude between that of 3-methyl-4-nitropyridine N-oxide and 2-methyl-2,4-dinitrophenyl aminopropanoate molecular compounds. Chained anions screen favourably the interactions between the non-linear cations in acentric phases, while the reverse situation is observed in the centric phase of 2-amino-5-nitropyiridinium bromide built up with open pseudo-hexagonal anionic layers.

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.

Perfect layered arrangement of ion-paired chromophores in a crystalline non-linear optical organic salt: 2-amino-3-nitropyridinium chloride

2-Amino-3-nitropyridinium chloride is reported as a new crystalline non-linear optical organic salt, built around a two-dimensional hyperpolarisable cationic chromophore. Its crystal structure (space groupP2 1 ) reveals a quasi-perfect layered arrangement of the cations and the anions. Within each layer the chromophores are arranged in a herringbone structure and strong hydrogen bonds are present. The first hyperpolarisabilities of ion-paired chromophores calculated for 2-amino-3-nitropyridinium chloride as well as 2-amino-5-nitropyridinium chloride emphasize the favourable contribution of the inorganic anionic sublattice to the enhancement of the molecular β ijk and macroscopic χ (2) susceptibilities.

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.