E- or Z-Isomers Arising from the Geometries of Ligands in the Mercury Complex of 2-(Anthracen-9-ylmethylene)-N-phenylhydrazine Carbothioamide

An anionic mercury(II) complex of 2-(anthracen-9-ylmethylene)-N-phenylhydrazine carbothioamide (HATU) and two isomers of a neutral mercury(II) complex of the anion of the same ligand (ATU) were reported. The anionic complex [Hg(HATU)2Cl2]·CH2Cl2 had a monodentate HATU ligand (a neutral form of the ligand) and chloride ligands. The two conformational isomers were of the neutral mercury(II) complex Hg(ATU)2·2DMF. The two isomers were from the E or Z geometry of the ligands across the conjugated C=N-N=C-N scaffold of the coordinated ligand. The two isomers of the complex were independently prepared and characterized. The spectroscopic properties of the isomers in solution were studied by 1H NMR as well as fluorescence spectroscopy. Facile conversion of the E-isomer to the Z-isomer in solution was observed. Density functional theory (DFT) calculations revealed that the Z-isomer of the complex was stable compared to the E-isomer by an energy of 14.35 kJ/mol; whereas, E isomer of the ligand was more stable than Z isomer by 8.37 KJ/mol. The activation barrier for the conversion of the E-isomer to the Z-isomer of the ligand was 167.37 kJ/mol. The role of the mercury ion in the conversion of the E-form to the Z-form was discussed. The mercury complex [Hg(HATU)2Cl2]·CH2Cl2 had the E-form of the ligand. Distinct photophysical features of these mercury complexes were presented.

π-Stacking among the Anthracenyl Groups of a Copper Complex Resulted in Doubling of Unit Cell Volume To Provide New Polymorphs

Two polymorphs of the 9-N-(3-imidazolylpropylamino)methylanthracene (Hanthraimmida) containing hydrated copper(II)-2,6-pyridinedicarboxylate complex are reported. The two polymorphs have either lamellar or Herringbone arrangements of π-stacks among the anthracenyl groups of organocation. The difference between the two polymorphs originated from having face-to-face stacking arrangements between the two anthracenyl groups of the symmetry independent cations within the unit cell in one of the polymorphs. The π-stacked anthracenyl groups in consecutive layers of the polymorphs are oriented in one direction in the polymorph designated as P1, whereas the polymorph designated as P2 has such orientations in opposite directions. The unit cell volume of the polymorph P2 (Z = 4) has approximately twice the volume of the polymorph P1 (Z = 2); it happend due to coalescence of two unit cells of P1 in the ab-crystallographic plane. A mixed methanol/water solvate of the copper complex is also reported. It has a channel-like arrangement of the cations; has the anions and the solvents within the cation embraced channel-like enclosures. This complex is unstable, once taken out from the methanol solvent, it transforms in real time to P2 by replacements of the methanol molecules by water molecules.

Polymorphic solvates, ionic cocrystals and C–N bond formation to form ionic cocrystals in sulfamethoxazole and sulfathiazole-derived urea

Solvates and ionic cocrystals of two sulfa-drug based urea derivatives were studied, where also polymorphs of a solvate, thermal stability, unusual C–N bond formation and desolvation were elucidated.

Changes in the proportions of an active pharmaceutical through cocrystals

In this study, the modulation of amounts sulfathiazolium cations in different 2,6-pyridinedicarboxylates is demonstrated. An uncommon monoionic sulfathiazolium zinc 2,6-pyridinedicarboxylate (1:1 electrolyte) complex was characterized. Conventional sulfathiazolium zinc-bis-2,6-pyridinedicarboxylate dianionic complexes (2:1 electrolyte) were formed when hydroxyaromatic compounds such as 1,3-dihydroxybenzene or 3-nitrophenol were used as guest components. Thus, with the aid of the hydroxyaromatic molecules the zinc-bis-2,6-pyridinedicarboxylate complexes were stabilized with the relatively large sized sulfathiazolium cations. It was a consequence of domain expansion by the phenolic compounds. Sandwiched aromatic guests between the 2,6-pyridinedicarboxylates provided appropriate packing to accommodate the two large cations in the self-assemblies, which helped to modulate the amounts of sulfathiazole in different formulations. Antibacterial activities with E. coli DH5α have shown that the salt and the complexes have lower g/ml antibacterial activity than the parent drug.

Intrinsic structural features of coordination polymers make an impact on dye selectivity

Differences in hydrogen-bonded assembly help in recognition of dyes.

5-[(Pyren-9-ylmethyl)amino]isophthalic acid with nitrogen containing heterocycles: stacking, N–H⋯π interactions and photoluminescence

Synthons guided the types of N–H⋯π interactions and stacking to cause quenching of emissions.

Self-Assemblies of Zinc Complexes for Aggregation-Induced Emission Luminogen Precursors

Positional isomers of zinc-nitrobenzoate complexes possessing pyridine -3-(or-4-) carboxamide are used for a comparative theoretical and experimental study to understand their utility as model complexes to understand the role of metal-to-ligand charge transfer in aggregation-induced emission (AIE). Among the five different model zinc complexes, four of them are non-ionic, and one is an ionic complex. The frontier molecular energy levels of different combinations of the positional isomeric complexes and the absorption maximum were ascertained by density functional theory calculations. The PolyQ value obtained from solid samples of each complex is different. Shifts in the emissions to higher wavelengths than the expected emission for the S₁ to S₀ transition were observed due to aggregations. The highest value of PolyQ among the complexes was 13.56% observed for emission at 439 nm (λ_ex = 350) of the non-ionic complex, namely, (di-aqua)bis(pyridine-3-carboxamide)di(2-nitrobenzoato)zinc(II) monohydrate. Close resemblance in emission lifetime decay profiles of the solid samples of those complexes and the respective solutions of those complexes in dimethyl sulfoxide with or without water showed a common trend, suggesting aggregation-induced emission in each case. Aggregation-induced emission caused by adding water in dimethyl sulfoxide solution of each complex showed an initial increase without a shift in the emission wavelength followed by a quenching with a shift of the respective emission peak to a short wavelength. Dynamic light scattering studies showed an increase in the average particle sizes upon an increase in the concentration of water. This indicated initial participation of water molecules to form aggregates with the complexes, favoring an increase in the AIE intensity. Aggregation of each complex changes with the concentration of water, and an increase in the concentration of water beyond a characteristic limit causes lowering of the emission intensity to the short wavelength.

Photophysical properties of Ag, Zn and Cd - N-(4-pyridylmethyl)-1,8-naphthalimide complexes: influences of π-stacking and C–H⋯O interactions

In solution ligand and complexes show similiar fluorescence emission whereas emission in solid samples are distinguishable.

Copper(II), Zinc(II), and Cadmium(II) Formylbenzoate Complexes: Reactivity and Emission Properties

Synthesis, characterization, reactivity, and sensing properties of 4-formylbenzoate complexes of copper(II), zinc(II), and cadmium(II) possessing the 1,10-phenanthroline ancillary ligand are studied. The crystal structures of the (1,10-phenanthroline)bis(4-formylbenzoate)(aqua)copper(II) and (1,10-phenanthroline)bis(4-formylbenzo-ate)zinc(II) and a novel molecular complex comprising an assembly of mononuclear and dinuclear species of (1,10-phenanthroline)bis(4-formylbenzoate)cadmium(II) are reported. These zinc and cadmium complexes are fluorescent; they show differentiable sensitivity to detect three positional isomers of nitroaniline. The mechanism of sensing of nitroanilines by 1,10-phenanthroline and the complexes are studied by fluorescence titrations, photoluminescence decay, and dynamic light scattering. A plausible mechanism showing that 1,10-phenanthroline ligand-based emission quenched by electron transfer from the excited state of 1,10-phenanthroline to nitroaniline is supported by density functional theory calculations. In an anticipation to generate a fluorescent d¹⁰-copper(I) formylbenzoate complex by a mild reducing agent such as hydroxylamine hydrochloride for similar sensing of nitroaromatics as that of the d¹⁰-zinc and cadmium 4-formylbenzoate complexes, reactivity of d⁹-copper(II) with hydroxylamine hydrochloride in the presence of 4-formylbenzoic acid and 1,10-phenanthroline is studied. It did not provide the expected copper(I) complex but resulted in stoichiometry-dependent reactions of 4-formylbenzoic acid with hydroxylamine hydrochloride in the presence of copper(II) acetate and 1,10-phenanthroline. Depending on the stoichiometry of reactants, an inclusion complex of bis(1,10-phenanthroline)(chloro)copper(II) chloride with in situ-formed 4-((hydroxyimino)methyl)benzoic acid or copper(II) 4-(hydroxycarbamoyl)benzoate complex was formed. The self-assembly of the inclusion complex has the bis(1,10-phenanthroline)(chloro)copper(II) cation encapsulated in hydrogen-bonded chloride-hydrate assembly with 4-((hydroxyimino)methyl)benzoic acid.

Stacking among the clips of the poly-aromatic rings of phenazine with hydroxy-aromatics and photophysical properties

Clip-like arrangements of molecules in the cocrystals of phenazine with hydroxy-aromatics in their respective self-assemblies and photophysical properties were presented. Phenazine cocrystals with 1,2-dihydroxybenzene provided assembly with butterfly-like arrangements. In these cocrystals, the phenazine molecules occurred in parallel pairs having extensive π-stacking. The clip-like cocrystals with 1,3-dihydroxybenzene also exhibited parallel pairs of phenazine molecules that were parallel cofacial π-stacked. The hydrated cocrystals of phenazine with 1,2,3-trihydroxybenzene had chains of parallel cofacial phenazine rings having three distinguishable π-separation distances among the centroids of the phenazine rings. Also, 2,7-dihydroxynaphthalene formed a clip-like cocrystal with phenazine, which encapsulated an additional molecule of phenazine. This cocrystal also provided chain-like parallel arrangements of the phenazine molecules. The emission and quantum yields of the cocrystals were determined by the integrating sphere method, which indicated that only the cocrystal of phenazine with 2,7-dihydroxynaphthalene showed monomer-like emission of phenazine and the rest of the cocrystals were in a quenched state. In the solution phase, quenching of the emission of hydroxynaphthalene was observed when phenazine was added to an independent solution of 2,7-dihydroxynaphthalene or another hydroxynaphthalene. However, when hydroxybenzenes were added to a solution of phenazine, fluorescence enhancements of phenazine occurred due to photo-electron transfer.

π-Stackings control the photoluminescence efficiencies in solids, whereas in solutions, the ON or OFF processes are dependent on the hydroxyaromatics.

Combinations of Tautomeric Forms and Neutral-Cationic Forms in the Cocrystals of Sulfamethazine with Carboxylic Acids

The cocrystals of sulfamethazine with different acids, namely, 2-mercaptophenylcarboxylic acid, 2,6-pyridinedicarboxylic acid, 4-(4-hydroxyphenylazo)phenylcarboxylic acid, 3-(4-hydroxyphenyl)propanoic acid, and 4-(phenyl)phenylcarboxylic acid, are studied here. Each has distinct notable supramolecular features. The pyrimidin-2-amine unit of the sulfamethazine provided unique examples of cocrystals in which amidine and imidine forms or neutral and protonated forms of sulfamethazine are observed in 2:2 ratios. Hence, this study provides avenues to explore cocrystals with tautomeric forms together in a cocrystal and also neutral and protonated cocrystal partners as apparent multicomponents in cocrystals. Among the cocrystals, three of them have the amidine form of the sulfamethazine in respective self-assembly. The cocrystal of 2-mercapto-phenylcarboxylic acid with sulfamethazine has the amidine form and it has the distinction of having S-H···π interactions. The cocrystal of sulfamethazine with 2,6-pyridinecarboxylic acid is a rare example of a 1:1 cocrystal of sulfmethazine with dicarboxylic acid. It has methanol molecules as a solvent of crystallization. Sulfamethazine forms a hydrated cocrystal with 4-(4-hydroxyphenylazo)-phenylcarboxylic acid that has conventional R 2 2(8) synthons of amidine hydrogen-bonding with carboxylic acid. The phenolic part of the acid component is anchored to the water molecule and provides a robust self-assembly. The hydrated cocrystal of sulfamethazine with 3-(4-hydroxyphenyl)propanoic acid (2:2 cocrystal) has two independent molecules of sulfamethazine, one in amidine form and the other in imidine form. It has two neutral carboxylic acids anchored through complementary hydrogen bonds and also has two water molecules of crystallization. The cocrystal of sulfamethazine with 4-(phenyl)phenylcarboxylic acid is also a 2:2 cocrystal. It is a di-hydrate, which has a neutral and protonated form of sulfamethazine. The neutral form is hydrogen-bonded to a neutral carboxylic acid, whereas the protonated form is charge-assisted hydrogen-bonded to the corresponding carboxylate anion.

Photo-physical properties of salts of a di-topic imidazole-tethered anthracene derivative in solid and solution

Combined effects of Dexter-quenching and protonation to change the photoluminescence of a di-topic anthracene–amine conjugate by nitrophenols and aromatic carboxylic acids in solid and solution are presented.

Different self-assemblies and absorption–emission properties of the picrate salts of aromatic amine or heterocycle linked oximes

Different sub-assemblies and fluorescence quenching in picrate salts of an aromatic amine and of three different heterocycle tethered aldoximes are described.

Four-coordinated see-sawN-(aryl)-2-(propan-2-ylidene)hydrazinecarbothioamide complexes of nickel(ii), copper(ii) and zinc(ii) and their propensity for catalytic cyclisation

Four-coordinated metal complexes of two hydrazinecarbothioamide-derived ligands with divalent nickel, copper and zinc are described and the selective reactivity difference of copper(ii) to cyclise the ligand or to form a complex is described.

Conformation and Visual Distinction between Urea and Thiourea Derivatives by an Acetate Ion and a Hexafluorosilicate Cocrystal of the Urea Derivative in the Detection of Water in Dimethylsulfoxide

Structures of different solvates and solute-solvent interactions of 4-(3-(4-nitrophenyl)urido)benzoate (L ₁ ) and methyl-4-(3-(4-nitrophenyl)thiourido)benzoate (L ₂ ) with different solvents are analyzed. The solution of L ₁ with tetrabutylammonium acetate (TBAA) in dimethylsulfoxide (DMSO) is colorless, but a similar solution of L ₂ with TBAA is orange. On the other hand, respective solutions of these urea and thiourea derivatives with tetrabutylammonium fluoride (TBAF) in DMSO are orange. Urea derivative L ₁ facilitates the reaction of TBAF with glass to form tetrabutylammonium hexafluorosilicate, which on further interaction with L ₁ forms cocrystal 2L ₁ ·(TBA)₂SiF₆. Reorganization of hydrogen-bonded self-assembly of 2L ₁ ·(TBA)₂SiF₆ in DMSO caused by water is established by a dynamic light scattering study. With an increase in the amount of water in the solution, visual color changes from orange to colorless, and the color changes are reversed upon the addition of a dehydrating agent such as molecular sieves. Solvates of L ₁ with DMSO, dimethylformamide (DMF), and dimethylacetamide are quasi-isostructural. The respective self-assembly of these solvates differs due to orientations of aromatic rings and the carbomethoxy group across the thioamide/amide bond. Significant differences in self-assemblies of the respective DMSO solvate of L ₁ and L ₂ are observed; self-assembly of the former has dimeric subassemblies as repeat units, whereas the latter has monomeric subassemblies. DMF solvates of L ₁ and dimethylacetamide of L ₁ are built by dimeric subassemblies to form self-assembled structures, but these subassemblies differ in the orientation of the carbomethoxy group across the urea units.

Competing phenol–imidazole and phenol–phenol interactions in the flexible supramolecular environment of N,N′-bis(3-imidazol-1-ylpropyl)naphthalenediimide causing domain expansion

Spectroscopic and crystallographic studies on cocrystals of N,N′-bis(3-imidazol-1-yl-propyl)naphthalenediimide (L) with a series of phenolic compounds have revealed that competition to form phenol–imidazole and phenol–phenol synthons causes domain expansion.

Oxime synthons in the salts and cocrystals of quinoline-4-carbaldoxime for non-covalent synthesis

Synthons in the cocrystals and salts of quinoline-4-carbaldoxime with acids are discussed.

Solvent and anion facilitated conformational changes in benzylamine substituted thiazolamine

Solvent and anion guided conformational adjustments in the syn–anti–syn form of N,N′-(1,4-phenylene-bis(methylene))-bis(5-methylthiazol-2-amine) and the utility of nitrate ions in stabilizing the anti–anti–anti form are established.

A study on fluoride detection and assembly of hydroxyaromatic aldoximes caused by tetrabutylammonium fluoride

Different assemblies formed by the interactions of tetrabutylammonium fluoride with hydroxy-aromatic oximes show characteristic optical properties.

A modular approach for molecular recognition by zinc dipicolinate complexes

Recognition of 4-nitrophenol guest molecules by stacking and H-bonding interactions with a 4,4′-bipyridinium zinc dipicolinate host was found and investigated in detail.

Cyclic aromatic imides as a potential class of molecules for supramolecular interactions

Prospects of stacking interactions of imides beneficial to generation of new soft materials are projected by analysing examples of primary building blocks that provide a basis for understanding at the molecular level.

Study on divalent copper, nickel and zinc model complexes for fluoride ion detection

A series of mononuclear hydroxyaromatic oxime metal complexes were synthesized for detection of fluoride ion and shown that the spectral signals of such complexes depend on the electronic configuration of the metal ion.

Structural and magnetic properties of oxyquinolinate clusters of cobalt(ii) and manganese(ii) and serendipitous intake of carbonate during synthesis

During transformation of a Co₄ oxiquinolinate cluster to a Co₁₀ cluster, serendipitous intake of a carbonate ion was observed.

Selective interactions of 5-(hydroxyimino)quinolin-8-one with tetrabutylammonium fluoride and zinc(ii) ions

Zinc ions or fluoride ions can be selectively detected by 5-(hydroxyimino)quinolin-8-one under mild acidic conditions.