Melanie Rademeyer

Structures and trends of one-dimensional halide-bridged polymers of five-coordinate cadmium(II) and mercury(II) with benzopyridine and -pyrazine-type N-donor ligands

Cadmium and mercury dihalides were reacted with benzopyridine- and benzopyrazine-type N-donor ligands as Lewis bases. The solid-state structures of 13 novel reaction products were studied by X-ray diffraction. Eleven of the structures can be classified as one-dimensional halide-bridged polymers of composition [M(μ-X)2(L)]∞, in which the metal ion displays a coordination number of five, while the remaining two structures exhibit one-dimensional dimers that are linked by long, semi-coordinate M–X⋯M–X interactions to form pseudo-halide-bridged polymers. Four of the structures contain Cd2+ as the metal ion, while the remaining nine have Hg2+ as the metal ion. Although all the halide-bridged polymers show a coordination number of five, two different metal cation geometries are displayed. A detailed comparison of all structural results, which includes related compounds from the literature and allows for the study of the effect of an increase in the width of the N-donor ligand on the halide-bridged chain geometries and other structural features, concludes the discussion.

Robust motifs in 2-phenylethylammonium and related tetrahalometallates

The novel crystal structures of seven compounds which combine 2-phenylethylammonium cations and perhalometallate anions, all with the general formula (C8H9NH3+)2 MX42−, were determined to establish the effect of metal atom and halogen ligand substitution on the structures and hydrogen bonding interactions. Five of the structures, bis(2-phenylethylammonium) tetrachlorozincate, (C8H9NH3+)2 ZnCl42−, bis(2-phenylethylammonium) tetraiodozincate, (C8H9NH3+)2 ZnI42−, bis(2-phenylethylammonium) tetrabromodichloroiodozincate, (C8H9NH3+)2 ZnCl2BrI2−, bis(2-phenylethylammonium) tetrabromocadmate, (C8H9NH3+)2 CdBr42−, and bis(2-phenylethylammonium) tetrabromomercurate, (C8H9NH3+)2 HgBr42−, were found to be isostructural, while two of the compounds containing iodo ligands, bis(2-phenylethylammonium) tetraiodocadmate, (C8H9NH3+)2 CdI42−, and bis(2-phenylethylammonium) tetraiodomercurate, (C8H9NH3+)2 HgI42−, crystallize in a different, but related disordered structure. Strong N+–H⋯X−–M hydrogen bonding interactions, as well as weaker C–H⋯π aromatic interactions occur in all seven structures, and two robust tetrameric hydrogen bonded zero-dimensional motifs are present in all seven structures. C–H⋯Cl–M hydrogen bonding interactions are present in the structure of bis(2-phenylethylammonium) tetrachlorozincate, and result in the distortion of the geometry of the 2-phenylethylammonium cation. Comparison of the identified zero-dimensional hydrogen bonding motifs with those occurring in related structures reported in the literature shows that the motifs are robust and can tolerate changes in cation, metal and ligand to a large extent.

Structures and trends of neutral MXxsolvent4−x tetrahedra and anionic [MX4]2− tetrahalometallates of zinc(II), cadmium(II) and mercury(II) with benzopyridine- and benzopyrazine-type N-donor ligands or cations

Zinc, cadmium and mercury dihalides were reacted with benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX4]2−, with either Cd2+ or Hg2+ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn2+ as the tetrahedral cationic node. Five of the nine Zn2+ compounds are neutral, and four are ionic. Three of the four ionic Zn2+ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX4]2−, while the inorganic component of the fourth ionic Zn2+ compound is coordinated by three halido ligands and one aqua ligand, [ZnX3(H2O)]−. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.

Bis(4-amino-benzoic acid-κN)dichloridozinc(II).

Molecules of the title compound [ZnCl2(C7H7NO2)2], are located on a twofold rotation axis. Two 4-aminobenzoic acid moieties, and two chloride ligands are coordinated to a Zn atom in a tetrahedral fashion, forming an isolated molecule. Neighbouring molecules are linked through hydrogen-bonded carboxyl groups, as well as N—H⋯Cl hydrogen-bonding interactions between amine groups and the chloride ligands of neighbouring molecules, forming a three-dimensional network.

3-Methyl-anilinium nitrate.

In the title compound, C7H10N+·NO3 −, the 3-methylanilinium cations interact with the nitrate anions through strong bifurcated N+—H⋯(O,O) hydrogen bonds, forming a two-dimensional hydrogen-bonded network.

Bis(2-methyl-4-nitro­anilinium) tetra­chloridomercurate(II)

The title compound, (C7H9N2O2)2[HgCl4], self-assembles into cationic organic bilayers containing the 2-methyl-4-nitroanilinium cations, sandwiched between anionic inorganic layers built up by the distorted tetrahedral [HgCl4]2− groups. The organic sheets are interlinked through weak C—H⋯O hydrogen bonds, while they interact with the anionic part via strong charge-assisted N+—H⋯Cl—Hg hydrogen bonds. The [HgCl4]2− anions are bisected by a mirror plane passing through the metal and two of the chloride ions.

2-Chloro-3-fluoropyridine copper(II) complexes and the effect of structural changes on magnetic behavior

Abstract A family of copper(II) compounds has been prepared with the general formula (2-chloro-3-fluoro-pyridine)2CuX2·n(Y), where X = Cl, Br, n = 0,1, and Y = methanol or water. For the copper chloride complexes, only solvated structures were obtained (1, X = Cl, Y = H2O; 2, X = Cl, Y = CH3OH) while for the copper bromide compounds, both a desolvated structure and the methanol solvate were prepared (3, X = Br, Y = none; 4, X = Br, Y = CH3OH). Each compound has been characterized by IR, powder X-ray diffraction, single-crystal X-ray diffraction, and temperature-dependent magnetic susceptibility measurement. Compounds 1 and 4 are isostructural, in the space group Cm, and neither exhibits significant magnetic exchange although superexchange pathways are present. Compound 2 also crystallizes in the Cm space group and exhibits weak ferromagnetic interactions (J/kB = 1.72(2) K from the 1D-ferromagnetic chain model) which are likely propagated by hydrogen bonding. Compound 3 crystallizes in the space group P21/n with the Cu(II) ion sitting on a crystallographic inversion center. Compound 3 exhibits weak antiferromagnetic exchange via two-halide superexchange typical for similar complexes. The magnetic data for 3 were fit to the 1D-antiferromagnetic chain model resulting in J/kB = −1.21(1). GRAPHICAL ABSTRACT

Tetrahalometallate salts of N-(4-picolinium)-1,8-naphthalimide: structures and solid-state fluorescence

The structural characteristics and solid-state fluorescence behaviour of organic–inorganic hybrid compounds formed through the combination of the N-(4-picolinium)-1,8-naphthalimide (pnH) cationic fluorophore with tetrahalometallate anions were investigated. Eight novel crystal structures, of the formula 2(C18H13N2O2)+[MX4]2−, were obtained through the combination of divalent metal halide salts and pnH cations, with [MX4]2− = [CoCl4]2− in structure pnHCoCl, [CoBr4]2− in pnHCoBr, [ZnCl4]2− in pnHZnCl, [ZnBr4]2− in pnHZnBr, [CdCl4]2− in pnHCdCl, [HgCl4]2− in pnHHgCl, [CuCl4]2− in pnHCuCl and [CuBr4]2− in pnHCuBr. To highlight the effect of halide salt formation, the structures and fluorescence behaviour of N-(4-picolinium)-1,8-naphthalimide chloride, pnHCl, and N-(4-picolinium)-1,8-naphthalimide bromide, pnHBr, were also studied. The effect of the formation of the halide- or tetrahalometallate salt on the solid-state fluorescence properties relative to that of N-(4-picolyl)-1,8-naphthalimide (pn) is highlighted. In addition, packing trends across the family and crystal engineering synthons are identified. It is illustrated that the fluorescence emission of the pn fluorophore can be tweaked through the formation of its halide- or tetrahalometallate salt.

The MX2Lx matrices, with M = Zn2+, Cd2+, Hg2+, X = Cl−, Br−, I− and L = pyrazine, quinoxaline, phenazine

Abstract Three structures combining the ditopic organic ligand quinoxaline with divalent metal halides MX2, with M = Cd2+ and Hg2+, are reported. All three structures are coordination polymers, with the quinoxaline ligand acting as organic linker between metal centers. In two structures, with M = Hg2+ and X = Cl− or Br−, the formation of a 1-D, halide-bridged polymer in addition to the quinoxaline coordination polymer increases the dimensionality of the structure to 2-D, while in the case of M = Hg2+ and X = Cl−, the formation of two halide-bridged polymers along with the coordination polymer results in the creation of a 3-D structure. Structural trends are identified, and the templating effect of the organic ligand is highlighted, through horizontal and vertical comparisons of these structures with related structures reported in the literature obtained upon combining the said metal halides with the related organic ligands pyrazine, quinoxaline, and phenazine, presented as the resulting matrices of structures.

Salts of 4-aminobutyric acid and 6-aminohexanoic acid behaving as molecular Velcro

The crystal structures of eight novel carboxyalkylammonium salts, (+H3N(CH2)nCOOH)X−, are reported, with n = 4 and X = Cl, Br and I in structures 1, 2 and 3, respectively, and n = 6 and X = Cl, Br·0.5H2O, Cl·0.5H2O, NO3 and ClO4 in structures 4, 5, 6, 7 and 8. The members of this family of compounds were found to display significant structural diversity, and a careful analysis of the structures employing the principles of crystal engineering was done to explain the observed trends and differences, specifically also the interdigitation or non-interdigitation of alkyl chains. It was found that a primary hydrogen bonding network formed between the ammonium groups and halide or oxo-anions, which plays a major structure-directing role. The structures may be likened to molecular Velcro, in which secondary hydrogen bonding interactions involving the carboxylic acid groups act as “hooks” to link primary networks.