New Acentric Materials Constructed From Aminopyridines And 4-Nitrophenol

Co-crystallization of 4-nitrophenol (I) with five aminopyridines (4-aminopyridine 1, 3,4-diaminopyridine 2, 2,3-diaminopyridine 3, 3-aminopyridine 4, 2-amino-6-methylpyridine 5) and 2,4-diaminopyrimidine 6 resulted in six adducts with the ratio of components 2 : 1 in five and 1 : 1 in one final compounds. Single crystals were grown by slow evaporation technique using ethanol as a solvent. Five adducts with 1-5 crystallize in acentric P21 and Pna21 space groups, and one, 2(I)·6-in centrosymmetric P21/c space group. Compounds 2(I)·1, 2(I)·2, 2(I)·3 are isomorphous, and demonstrate similar H-bonding patterns despite the differences in aminopyridine molecules. Compound 2(I)·5 is isomorphous to two previously reported compounds. Adducts 2(I)·1, 2(I)·2, 2(I)·3, 2(I)·5, 2(I)·6 represent organic salts composed of pyridinium/pyrimidinium cation, 4-nitrophenolate anion, and 4-nitrophenol neutral molecule. The H-bonded 4-nitrophenol-4-nitrophenolate anionic dimers were found in all compounds with 2 : 1 molar ratio. In adduct I·4 both molecules are in neutral form. The IR spectral data support crystallographic conclusions on salts formation. Plane wave pseudopotential density functional theory calculations were used to predict hyperpolarizability tensor components. Our calculations suggest 2(I)·3 as the best candidate for nonlinear optical materials (14 times more active than urea). © 2013 The Royal Society of Chemistry

Pyrimidine-2,4-diamine acetone monosolvate

In the title compound, C4H6N4·C3H6O, the pyrimidine-2,4-diamine molecule is nearly planar (r.m.s. deviation = 0.005 Å), with the endocyclic angles covering the range 114.36 (10)–126.31 (10)°. In the crystal, N—H...N and N—H...O hydrogen bonds link the molecules into ribbons along [101], and weak C—H...π interactions consolidate further the crystal packing

Pyridine-2,5-diamine

In the title molecule, C5H7N3, intracyclic angles cover the range 117.15 (10)–124.03 (11)°. The N atoms of the amino groups have trigonal–pyramidal configurations deviating slightly from the pyridine plane by 0.106 (2) and −0.042 (2) Å. In the crystal, the pyridine N atom serves as an acceptor of an N—H...N hydrogen bond which links two molecules into a centrosymmetric dimer. Intermolecular N—H...N hydrogen bonds between the amino groups further consolidate the crystal packing, forming a three-dimensional network

Unusual Chemical Ratio, Z″ Values, and Polymorphism in Three New <i>N-</i>Methyl Aminopyridine–4-Nitrophenol Adducts

Cocrystallization of 4-nitrophenol (<b>I</b>) with <i>N</i>-methyl substituted aminopyridines, 4-<i>N</i>-methylaminopyridine <b>1</b>, 2-<i>N</i>-methylaminopyridine <b>2</b>, and 2-<i><i>N,N</i></i>-dimethylaminopyridine <b>3</b>, resulted in three novel adducts <b>1</b>·2­(<b>I</b>), <b>2</b>·3­(<b>I</b>), and <b>3</b>·3­(<b>I</b>), one of which, <b>2</b>·3­(<b>I</b>), was found in three polymorphic forms, <b>A</b>, <b>B</b>, and <b>C</b>. The single crystals were grown by slow evaporation from ethanol. The proton transfer from the phenoxy to the pyridine moieties was registered in all compounds. The adducts comprise pyridinium cations, 4-nitrophenolate anions, and varying in number neutral 4-nitrophenol molecules. Though the asymmetric hydrogen-bonded network involving the −N⁺H groups of pyridinium cations and the −C–O^– and −C–OH groups of 4-nitrophenol moieties is registered in the adducts, the delicate balance of noncovalent interactions that include CH···O hydrogen bonds and face-to-face stacking interactions between the extended antiparallel arrays of components controls the centrosymmetric packing. Although three polymorphs of <b>2</b>·3­(<b>I</b>) share several structural common features, they reveal significant differences in the conformation of the pyridinium cation, and the hydrogen-bonding patterns

Pyridine-4-carbaldehyde&#8211;fumaric acid (2/1)

In the title co-crystal, 2C6H5NO&#183;C4H4O4, two crystallographically different hydrogen-bonded trimers are formed, one in which the components occupy general positions, and one generated by an inversion centre. This results in the uncommon situation of Z = 3 for a triclinic crystal. In the formula units, molecules are linked by O&#8212;H...N hydrogen bonds

Structural Diversity in the Complexes of Trimeric Perfluoro‑<i>o</i>‑phenylene Mercury with Tetrathia- and Tetramethyltetraselenafulvalene

Five potential charge transfer complexes of trimeric perfluoro-<i>o</i>-phenylene mercury (<b>I</b>) with tetrathiafulvalene (TTF) and tetramethyltetraselenefulvalene (TMTSF) were grown from different solvent mixtures. The adducts (<b>I</b>)₂·TTF (<b>1</b>) and <b>I</b>·TTF (<b>2</b>) were grown by slow evaporation from the 1:1 mixture of dichloromethane (CH₂Cl₂, DCM) and carbon disulfide (CS₂). Use of the different 1:1 solvent mixtures of dichloromethane (CH₂Cl₂, DCM) and dichloroethane (C₂H₄Cl₂, DCE) has led to the crystalline adducts <b>I</b>·TTF (<b>3</b>) and <b>I</b>·TTF·DCE (<b>4</b>). Adduct <b>I</b>.TMTSF (<b>5</b>) was grown by the interface crystallization on the border of two immiscible layers, ethyl acetate, and carbon disulfide. The cocrystals differ by the donor–acceptor ratio, molecular packing, and the solvent inclusion. The components in <b>1</b>–<b>5</b> form mixed donor–acceptor stacks. The stacks are stabilized by Hg···S and Hg···C short contacts, while the lateral interactions between stacks include F···F, CH···F, and S/Se···F short contacts

Spatially Non-uniform Trap State Densities in Solution-Processed Hybrid Perovskite Thin Films

The facile solution-processability of methylammonium lead halide (CH₃NH₃PbI₃) perovskites has catalyzed the development of inexpensive, hybrid perovskite-based optoelectronics. It is apparent, though, that solution-processed CH₃NH₃PbI₃ films possess local emission heterogeneities, stemming from electronic disorder in the material. Herein we investigate the spatially resolved emission properties of CH₃NH₃PbI₃ thin films through detailed emission intensity versus excitation intensity measurements. These studies enable us to establish the existence of nonuniform trap density variations wherein regions of CH₃NH₃PbI₃ films exhibit effective free carrier recombination while others exhibit emission dynamics strongly influenced by the presence of trap states. Such trap density variations lead to spatially varying emission quantum yields and correspondingly impact the performance of both methylammonium lead halide perovskite solar cells and other hybrid perovskite-based devices. Of additional note is that the observed spatial extent of the optical disorder extends over length scales greater than that of underlying crystalline domains, suggesting the existence of other factors, beyond grain boundary-related nonradiative recombination channels, which lead to significant intrafilm optical heterogeneities

Structural Diversity in the Complexes of Trimeric Perfluoro‑<i>o</i>‑phenylene Mercury with Tetrathia- and Tetramethyltetraselenafulvalene

Five potential charge transfer complexes of trimeric perfluoro-<i>o</i>-phenylene mercury (<b>I</b>) with tetrathiafulvalene (TTF) and tetramethyltetraselenefulvalene (TMTSF) were grown from different solvent mixtures. The adducts (<b>I</b>)₂·TTF (<b>1</b>) and <b>I</b>·TTF (<b>2</b>) were grown by slow evaporation from the 1:1 mixture of dichloromethane (CH₂Cl₂, DCM) and carbon disulfide (CS₂). Use of the different 1:1 solvent mixtures of dichloromethane (CH₂Cl₂, DCM) and dichloroethane (C₂H₄Cl₂, DCE) has led to the crystalline adducts <b>I</b>·TTF (<b>3</b>) and <b>I</b>·TTF·DCE (<b>4</b>). Adduct <b>I</b>.TMTSF (<b>5</b>) was grown by the interface crystallization on the border of two immiscible layers, ethyl acetate, and carbon disulfide. The cocrystals differ by the donor–acceptor ratio, molecular packing, and the solvent inclusion. The components in <b>1</b>–<b>5</b> form mixed donor–acceptor stacks. The stacks are stabilized by Hg···S and Hg···C short contacts, while the lateral interactions between stacks include F···F, CH···F, and S/Se···F short contacts