Richard F. D'Vries

Luminescence, chemical sensing and mechanical properties of crystalline materials based on lanthanide–sulfonate coordination polymers

Lanthanide-coordination polymers (Ln-CPs) constitute relevant compounds for the design of multifunctional materials. Nevertheless, studies devoted to an understanding of the relationships of combined structural–optical–mechanical properties have scarcely been reported. In this work, an exhaustive study of a series of CPs obtained from lanthanide metals, 3-hydroxinaphthalene-2,7-disulfonate (3-OHNDS) and 1,10-phenanthroline (Phen) as ligands is presented. Two crystalline phases were identified with the general formulae [Eu(3-OHNDS)(Phen)(H2O)]·3H2O (phase 1-Eu), and [Ln2(3-OHNDS)2(Phen)2(H2O)]·3H2O (phase 2-Ln), where Ln3+ = Tb, Dy, Ho, Er and Yb. Both phases were characterized by powder and single crystal X-ray diffraction, vibrational and thermal analysis and scanning electron microscopy. Moreover, nanoindentation analysis was performed in order to find the relationships between these structural features and the mechanical properties of the crystalline materials. The photoluminescence (PL) properties of the reported phases were also explored, involving excitation–emission experiments and quantification of color emission. Finally, one compound was selected as a chemical sensor model, exhibiting different optical behaviour in the presence of aromatic molecules, principally towards naphtalene molecules. These results make these compounds promising materials for the elaboration of selective chemical sensors.

4-{2-[4-(Dimethyl-amino)phen-yl]ethyl-idene}benzonitrile.

In the crystal of the title compound, C17H16N2, molecules are linked by C—H⋯N hydrogen bonds, forming rings of graph-set motifs R 2 1(6) and R 2 2(10). The title molecule is close to planar, with a dihedral angle between the aromatic rings of 0.6 (1)°. Torsion angles confirm a conformational trans structure.

Rare earth coordination dinuclear compounds constructed from 3,5-dicarboxypyrazolate and succinate intermetallic bridges

In this paper we describe the synthesis of a new family of rare earth compounds of general formula [RE2(dcpz)2(suc)(H2O)8]·(H2O)1.5, where RE = Y (1), La (2), Ce (3), Pr (4), Nd (5), Sm (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12) and Yb (13); dcpz = 3,5-dicarboxypyrazolate; suc = succinate. Single crystal X-ray diffraction studies showed that all the complexes are isostructural and crystallize in the triclinic system, space group P. They exist as dinuclear discrete molecules in which the metallic centers are linked together by dcpz and suc bridges. Hydrogen bonds between dimers give rise to a 3D bcu supramolecular network with topology (424·64). Solid-state photoluminescence studies revealed that the ligand-to-metal energy transfer mechanism is responsible for the visible emission of Sm (6), Tb (8) and Dy (9) compounds while for (5), near-infrared (1060 nm) emission was obtained by the direct excitation f orbitals in the Nd3+ ion. Magnetization measurements indicated antiferromagnetic interactions between the RE3+ ions, except Y3+ (1) and La3+ (2).

Supramolecular synthesis and thermochemical investigations of pharmaceutical inorganic isoniazid salts

In multiple-drug therapy, isoniazid (INH) is considered one of the most important antibiotics for the treatment of tuberculosis. Beyond its pharmacological importance, INH is also a versatile compound that can be combined with several other molecules to produce salts and co-crystals. In this study, novel salts of INH, obtained from the reaction with pharmaceutically accepted inorganic acids (HBr, HNO3 and H2SO4), were investigated. The reaction of INH with H2SO4, gives rise to two forms: an INH sulfate and an INH sulfate hemihydrate salt. The four salts feature a supramolecular assembly quite different from the one described for INH hydrochloride. INH hydrobromide and INH nitrate adopt a head-to-tail assembly, where the cations (INH+) are directly connected to each other. However, this is not the case for the sulfate forms, where the cations appear surrounded by the anions, being connected to them through their pyridinium and hydrazide groups. Interestingly, an unexpected homodimer is observed in the INH sulfate salt. Hirshfeld surface analysis was used to highlight and quantify the contributions of the main interactions. The relative thermal stability of these salts was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and hot-stage microscopy (HSM). Although the melting points of both sulfate forms are practically the same, the four INH salts have distinct thermal profiles.

Synthesis and characterization of (6-{[2-(pyridin-2-yl)hydrazinylidene]methyl}pyridin-2-yl)methanol: a supramolecular and topological study.

Hydrazones exhibit a versatile chemistry and are of interest for their potential use as functional molecular systems capable of undergoing reversible changes of configuration, i.e. E/Z isomerization. The title compound, C12H12N4O, has an E configuration with respect to the hydrazone C=N bond. The crystal packing is formed by N-H...N and O-H...N hydrogen bonds that give a two-dimensional layer structure and C-H...C interactions associated with layer stacking to produce the three-dimensional supramolecular structure. These intermolecular interactions were analyzed and quantified by the Hirshfeld surface method and the two-dimensional supramolecular arrangement was topologically simplified as a hcb network.

Order-disorder phase transition induced by proton transfer in a co-crystal of 2,4-dichlorobenzoic acid and trimethylamine N-oxide

A crystalline binary adduct between trimethylamine N-oxide (TMANO) and 2,4-dichlorobenzoic acid (2,4-DCBA) molecules was obtained by slow evaporation from acetonitrile. The obtained molecular complex is formed by a racemic mixture of molecular complexes crystallizing in the orthorhombic space group Pbca. An exhaustive analysis of the temperature dependence of the cell parameters and the behavior of the acidic hydrogen position and carboxylate group was performed by single crystal and powder X-ray diffraction, FT-IR spectroscopy and theoretical calculations. The molecular system was thermally characterized, subsequently demonstrating an order–disorder transition. Finally, the intermolecular interactions were analyzed via Hirshfeld surface analysis.

(E)-5-[1-Hy­droxy-3-(3,4,5-tri­meth­oxy­phen­yl)allyl­idene]-1,3-di­methyl­pyrimidine-2,4,6-trione: crystal structure and Hirshfeld surface analysis

In the title compound, C—H⋯O hydrogen bonds and aromatic π–π stacking combine to generate a three-dimensional network. A Hirshfeld surface analysis is presented.

[4-(Allyloxy)phenyl](phenyl)methanone

The structure of the title compound, C16H14O2, features a dihedral angle of 54.4 (3)° between the aromatic rings. The allyl group is rotated by 37.4 (4)° relative to the adjacent benzene ring. The crystal packing is characterized by numerous C—H⋯O and C—H⋯π interactions. Most of these interactions occur in layers along (011). The layers are linked by C—H⋯π interactions along [100], forming a three-dimensional network.

[4-(All-yloxy)phen-yl](phen-yl)methanone.

The structure of the title compound, C16H14O2, features a dihedral angle of 54.4 (3)° between the aromatic rings. The allyl group is rotated by 37.4 (4)° relative to the adjacent benzene ring. The crystal packing is characterized by numerous C—H⋯O and C—H⋯π interactions. Most of these interactions occur in layers along (011). The layers are linked by C—H⋯π interactions along [100], forming a three-dimensional network.