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The removal and detection of highly toxic and environmentally harmful gases such as SO2, H2S and CO2 is a hot topic of the scientific community. Porous organic compounds, in particular, imine based macrocycles, are promising materials for this purpose. In this paper we have used porous N4O4-donor macrocyclic Schiff base (1, 6, 20, 25- tetraaza-2, 5:8, 9:17, 18:21, 24:27, 28:36, 37 hexabenzo-10, 16, 29, 35-tetraoxa- cyclooctatriakonta- 1, 6, 20, 25-tetraen) (1) for sorption of NH3, SO2, Cl2, CO2 and H2S. Five novel inclusion compounds 1xNH3, 1xSO2, 1xCl2, 1xCO2 and 1xH2S were prepared by a single-crystal to single- crystal (SC-SC) transformation. Single-crystal X- ray diffraction (SCXRD) analysis of 1xCO2 and 1xNH3 inclusion compounds have shown that CO2 molecule resides in the plane of the macrocyclic ring connected by weak C–O … π interactions to the host, and no host-guest interactions in 1xNH3 were observed. The relative thermal stabilities of the host-guest systems (Ton – Tb parameter) is in the range from 93 (1xNH3) to 132 ◦C (1xH2S), indicating the formation of stable inclusion compounds. Although used gases are highly reactive and corrosive, FT IR and powder diffraction studies indicate that the molecular and crystal structure of the host is constant upon gas sorption. The activated compound displays moderate uptake (0.35 mmol/g) of CO2 at 298 K. The relatively high thermal stability, constant molecular and crystal structure of inclusion compounds with interesting optical properties (determined by solid state UV–Vis) make this material potentially useful for the detection of toxic gases.

A novel group of energetic compounds, known as energetic coordination polymers (ECPs), can be rationally designed by introducing of highly energetic ions like ClO4-, N3–, NO3– and NO2– into a polymeric framework. Herein we report the preparation of four novel cadmium(II) complexes with picolinamide (pia) as ligand and different ions: [Cd(pia)3](ClO4)2·2H2O (1), [Cd(NO3)(ac)(pia)2] (2), [Cd(NO2)2(pia)2] (3), [Cd2(μ1, 1-N3)4(pia)2]n [Cd(μ1, 1-N3)2(pia)]n (4). The presence of different anions from starting Cd(II) salts caused the formation of discrete coordination compounds(1, 2 and 3), and coordination polymer (4). In 2, 3 and 4 anions are coordinated to Cd(II), while in 1 perchlorate anions act as a counterion. The molecular and crystal structure analysis has shown that in all compounds pia acts as N, O-chelator in various coordination arrangements depending on the present anion (1, 2 and 4 - distorted octahedral, 3- distorted square antiprismatic). In the crystal structures, the dominant mode of intermolecular interaction is a strong head−to−head amide hydrogen bond, with exception of 1. Structural analysis of herein-reported compounds and previously described Cd(pia)A (A – anion) compounds has shown that bulky tetrahedral anions (ClO4- and SO42-) inhibit the formation of the strong head−to−head amide hydrogen bonds. The investigations of energetic properties and sensitivity indicate a possible application of compound 4 as a secondary explosive material with energetic properties like those of LA (lead azide), mercury fulminate, or ammonium nitrate.

A novel monosubstituted dipicolinic acid hydrazide derivative (H2L = 6-{; ; ; ; [2- (phenylcarbonyl)hydrazino]carbonyl}; ; ; ; pyridine-2- carboxylic acid) was prepared by the multi-step synthesis route starting from methoxy- substituted pyridine-2, 6-dicarboxylic acid. Reaction of the prepared compound with Co and Cr salts in the presence of 1, 6-diaminohexane resulted in formation of discrete complex compounds (CoL and CrL). The synthesized compounds were identified by chemical analyses and characterized by IR spectroscopy, thermal analysis and the ligand additionally by NMR spectroscopy. The crystal and molecular structure of the prepared complexes were determined by the single-crystal X-ray diffraction and electrochemical properties by cyclic voltammetry. The molecular structure of the complex compounds is found to be isostructural with rather small differences in the crystal packing arrangement. In both complexes the coordination geometry is octahedral and each metal ion is coordinated by two mutually orthogonal ligand molecules that act as N, N, O-tridentate ligand. In the crystal structure, the molecules are linked via multiple O–H⋯O, N–H⋯O and N–H⋯Cl hydrogen bond interactions thus forming a supramolecular zig- zag motif that is additionally stabilized by a series of hydrogen bond interactions that involve water molecule, diaminohexane cation, uncoordinated oxygen atom of carboxylic group and oxygen atom of carbonyl group. Electrochemical analysis of complex compounds indicated irreversible oxidation of Cr3+ in CrL and reduction of Co3+ to Co2+ in CoL, which agrees with the proposed oxidation state of the metal in complexes.

Drug–drug cocrystals are formulated to produce combined medication, not just to modulate active pharmaceutical ingredient (API) properties. Nano-crystals adjust the pharmacokinetic properties and enhance the dissolution of APIs. Nano-cocrystals seem to enhance API properties by combining the benefits of both technologies. Despite the promising opportunities of nano-sized cocrystals, the research at the interface of nano-technology and cocrystals has, however, been described to be in its infancy. In this study, high-pressure homogenization (HPH) and high-power ultrasound were used to prepare nano-sized cocrystals of 4-aminosalysilic acid and sulfamethazine in order to establish differences between the two methods in terms of cocrystal size, morphology, polymorphic form, and dissolution rate enhancement. It was found that both methods resulted in the formation of form I cocrystals with a high degree of crystallinity. HPH yielded nano-sized cocrystals, while those prepared by high-power ultrasound were in the micro-size range. Furthermore, HPH produced smaller-size cocrystals with a narrow size distribution when a higher pressure was used. Cocrystals appeared to be needle-like when prepared by HPH compared to those prepared by high-power ultrasound, which had a different morphology. The highest dissolution enhancement was observed in cocrystals prepared by HPH, however, both micro- and nano-sized cocrystals enhanced the dissolution of sulfamethazine.

Two novel polymorphs (Form I and II) of coumarin thione-triazole - 4-methyl-7-[(4-phenyl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methoxy]-2H-chromen-2-one, have been prepared by recrystallization of the crude product from water (Form I) and acetonitrile (Form II). Crystal structures of both forms were determined by the single-crystal X-ray diffraction and additionally characterized by FT-IR spectroscopy and thermal analysis. Single-crystal X-ray diffraction experiments revealed that two polymorphs crystalize in different crystal systems (orthorhombic and monoclinic), with different hydrogen bonding schemes and packing arrangements. In Form I, molecules are primarily connected via N H⋯O hydrogen bonds. Molecules of Form II are primarily connected by offset π···π interactions in the crystal structure. The intermolecular interactions in both crystal structures were further studied by the Hirshfeld surface analysis and intermolecular energy utilizing theoretical calculation. The DSC analysis revealed that Form II is a higher melting point form. Further analysis indicates the monotropic relationship between polymorphs. The Cambridge Structural Database search showed that this is the first structurally characterized compound containing coumarin thione-triazole moieties.

Structural characterization of novel Fe(III) basic acetate with 1,3,5,7-tetraazaadamantane (hexamine – HEX), [Fe3(μ3-O)(OAc)6(H2O)3)](NO3)(HEX)2(H2O)5] (1), revealed a molecular structure typical for Fe(III) basic carboxylates, with a triangular array formed by three iron atoms being equilateral and with an uncoordinated hexamine molecule and nitrate anion present in the crystal structure. Despite the hexamine molecule being uncoordinated, it plays a crucial role in the formation of a supramolecular network. The magnetic properties of the compound were characterized by magnetic susceptibility, Mossbauer and EPR spectroscopy. These studies indicate the presence of high-spin iron ions in +3 oxidation state with non-Curie-like behaviour. A small room temperature value of the effective magnetic moment and a decrease of the product χT with decreasing temperature both speak in favour of antiferromagnetic interactions between the three individual Fe(III) ions of complex 1 with a total ground state spin of St = 1/2 per trinuclear cluster. EPR spectroscopy confirmed the formation of a St = 1/2 ground state, but also suggested the presence of weak intermolecular exchange interactions between two (or more) clusters of neighbouring molecules. The temperature-dependent Mossbauer spectra show a slowing-down of the fast spin-lattice relaxation rates of the paramagnetic Fe(III) ion below about 60 K, however, yet no static spin regime is reached down to 3.6 K.

Despite polymorphism of crystalline active pharmaceutical ingredients (APIs) being a common phenomenon, reports on polymorphic co- crystals are limited. As polymorphism can vastly affect API properties, controlling polymorph generation is crucial. Control of the polymorph nucleation through the use of different solvents during solution crystallization has been used to obtain a desirable crystal polymorph. There have been two reported polymorphic forms of the 4- aminosalicylic acid-sulfamethazine co-crystals. These forms were found to have different thermodynamic stabilities. However, the control of co-crystal polymorph generation using preparation parameter manipulation has never been reported. The aim of this study was to establish the effect of different solvent parameters on the formation of different co- crystal polymorphic forms. Selection of the solvents was based on Hansen Solubility Parameters (HSPs) as solvents with different solubility parameters are likely to interact differently with APIs, ultimately affecting co- crystallization. Eight solvents with different HSPs were used to prepare co-crystals by solvent evaporation at two different temperatures. Through characterization of the co-crystals, a new polymorph has been obtained. The hydrogen bond acceptability seemed to affect the co-crystal form obtained more than the hydrogen bond donation ability. Furthermore, the use of HSPs can be utilized as an easy calculation method in screening and design of co-crystals.

Two novel discrete cadmium(II) complexes, namely [CdBr2(pia)2] (1) and [CdI2(pia)2] (2) were prepared by reactions of aqueous solutions of CdX2 (X = Br, I) salts with picolinamide (pia) in the 2:1 ligand to metal stoichiometric ratio. Both compounds were characterized by elemental analysis, IR-spectroscopy, TG/DSC analyses and electrochemical methods. The electrochemical characteristics of both ligand (pia) and prepared complexes were studied by cyclic and (cyclic) square-wave voltammetry, on a static mercury drop electrode (SMDE), in aqueous media over a wide pH range. The molecular and crystal structure of the compounds was determined by the single crystal X- ray diffraction method. X-ray structure analysis of 1 and 2 have shown that the compounds are isostructural with minor differences in the bond angles of the coordination sphere. In both compounds the Cd(II) ion is coordinated by two halide atoms and two mutually orthogonal picolinamide ligands that act as N, O-chelators in a distorted octahedral arrangement. In the crystal structure, the molecules of 1 and 2 are primarily linked via strong head–to–head amide hydrogen bond interactions forming dimers. In 1 the adjacent dimers are connected via Nsingle bondH⋯Br hydrogen bonds and offset face to face π⋯π interactions that involve pyridine rings, while in the structure of 2, the dimers are connected via Csingle bondH⋯O, Csingle bondH⋯N and Nsingle bondH⋯I hydrogen bonds into the final 3D structure. The intermolecular interactions in both crystal structures were further studied by Hirshfeld surface analysis. Electrochemical analysis of 2-picolinamide indicates the irreversible nature of its electro-reduction reaction on SMDE at pH 2. To provide better insight into the redox mechanism and electrokinetic properties of 2-picolinamide, the study of the effect of signal frequency on CSWV response was carried out, too. The electrochemical reduction of complex 2 involves two electron transfer reactions at −0.55 V and −0.83 V, indicating two redox active centers in the molecule, while complex 1 appears to be apparently electro-inactive in the studied potential range.

A novel N4O4-donor macrocyclic Schiff base (1, 6, 20, 25-tetraaza-2, 5:8, 9:17, 18:21, 24:27, 28:36, 37-hexabenzo-10, 16, 29, 35-tetraoxa-cyclooctatriakonta-1, 6, 20, 25-tetraen) (1) was prepared by a [2 + 2] cyclocondensation reaction of the corresponding dialdehyde and diamine. The crystal and molecular structure was determined by the single crystal X-ray diffraction analysis, and the compound was additionally characterized by IR, Raman and NMR spectroscopy, thermal and elemental analysis. In the crystal the molecules of the macrocycle are connected by a series of weak hydrogen bonds into tubular structures, thus forming an open porous structure with nanometre sized pores (around 18% of the void volume). Recrystallization of 1 from chloroform and dichloromethane led to the formation of the chloroform solvate (1×CLF), and the dichloromethane solvatomorph (1×DCM). The chloroform solvate was treated with iodine vapour in a sealed chamber thus forming a stable iodine host–guest complex (1×I2). From the spectroscopic, crystal structure, and thermal analysis studies of 1×CLF, 1×DCM and 1×I2 it can be deduced that the compound forms stable host–guest complexes without any changes in the organic framework. The host:guest ratio was found to be 1:1, 1:3 and 2:1 for chloroform, dichloromethane and iodine complexes, respectively. The adsorption studies of activated 1×CLF showed a small uptake of CO2 at 298 K.

Three novel silver(I) complexes with N2O2-donor macrocyclic Schiff bases L1 and L2 (L1 = 1, 5-diaza- 2, 4:7, 8:17, 18-tribenzo-9, 16-dioxa-cyclononadeca-1, 5-dien ; L2 = 1, 5-diaza-2, 4:7, 8:18, 19- tribenzo-9, 17- dioxa-cycloeicosa-1, 5-dien) were prepared by the reaction of the corresponding macrocycles with silver nitrate and silver perchlorate in 1:1 stoichiometric ratio. The reactions of macrocyclic ligands (L1 and L2) with silver perchlorate led to the formation of unusual (regarding donor set atoms) silver coordination polymers, AgL1ClO4, and (AgL2ClO4)2 CH2Cl2. The reaction of L2 with silver nitrate resulted in a formation of discrete binuclear silver complex (AgL2NO3)2. In all three compounds, silver ions are exo-coordinated due to the presence of rigid C@N bond in the molecular structure of ligands in which nitrogen atom non-bonding electron pairs are exo- oriented. All synthesized compounds were characterized by vibrational spectroscopy (IR) and thermal methods (TG/DSC). The crystal and molecular structures of silver complexes were determined by the single crystal X-ray diffraction method. In the complex AgL1ClO4, each silver atom is coordinated by two ligand molecules and one perchlorate anion (T-shaped geometry). The coordination geometry around the silver atom can be described as T-shaped, resulting in a formation of the 1D zig-zag polymeric chain. In (AgL2ClO4)2 CH2Cl2 two distinct coordination surroundings of silver ions that can be divided into cationic (linear geometry) and anionic (square planar geometry) part. The topology of the polymeric chain can be described as a 1D zig-zag. The silver atoms in (AgL2NO3)2 are tetrahedrally coordinated with two N-bound ligand molecules and one nitrate anion (bidentate). This form of coordination produces a discrete bimetallic silver complex with an additional metallacyclic ring. The anion and ligand influence on the chain structure is attributed to the presence of rigid imine double bond and partly to the coordination ability of counter ions.

The reactions of picolinamide (pyridine-2-carboxamide, pia) with various cadmium(II) salts in aqueous media were investigated. With cadmium(II) halides, three novel coordination polymers (CPs) were isolated, namely: [CdX2(pia)]n (X = Cl (1), Br (2), I (3). Cadmium(II) sulphate gave [Cd(SO4)(pia)(H2O)3] ·2H2O (4) while cadmium(II) nitrate in the presence of perchlorate ions gave mixed complex [Cd(pia)3(H2O)](NO3)(ClO4) (5) with both anions acting as counterions. All isolated complexes were identified by chemical analysis and characterized using IR-spectroscopy and thermal methods (TG/DSC). X-ray crystal structure analysis of 1–3 revealed a distorted octahedral coordination of Cd(II) which consists of four halide and N,O-chelated pia ligands. The chain propagation is achieved through metal-halide double-bridges. The pia ligand is in cis geometry (cis-configured polymeric chain) and the topology of chains can be described as zig-zag. In 1 the neighbouring chains are mutually linked through weak C H···Cl and N H···Cl hydrogen bonds into 3D supramolecular framework. In 2 and 3, which are isostructural, unlike in 1 the neighbouring chains are linked by a strong head-to-head amide hydrogen bonds (graph set R22(8)) into supramolecular sheets in (0 1 0) planes and through weak C H···X interactions a 3D supramolecular framework is accomplished. In discrete molecules of 4 and 5, a distorted octahedral and pentagonal bipyramidal coordination of Cd(II) ion is revealed respectively. The final 3D supramolecular dimensionality of 4 and 5 is achieved through non-covalent interactions including sulphate ions in the former, and perchlorate and nitrate ions in the later thus pointing a discernible influence of anions on the structure.

A novel symmetrical bis-Schiff base was synthesized and characterized by means of single crystal X-ray diffraction, FT-IR and NMR spectroscopy, elemental, TG/DSC and electrochemical analysis. The synthesized molecule represents a rare example of symmetrical bis-Schiff base with uncondensed primary amino group as the final reaction product. The molecule is planar, with largest deviation of aminophenyl benzene ring from the plane calculated through the aliphatic chain in the amount of 4.93(1)°. In the crystal, the molecules are primarily linked by hydrogen bonds involving primary amino groups and weak C H⋯π interactions. Consequently, these interactions are arranging molecules into herringbone packing motif. The FT-IR and NMR spectra indicated presence of both imino and amino groups in dissolved and solid state, therefore confirming consistency of the studied material and also molecular structure determined by X-ray diffraction. Electrochemical study has shown that the oxidation of the investigated Schiff base is irreversible, diffusion controlled process and that the oxidation products are adsorbed on the glassy carbon electrode surface.

C19H20O4, monoclinic, P21/c (no. 14), a = 16.5979(5) Å, b = 8.5654(2) Å, c = 11.8418(4) Å, β = 108.537(4)°, V = 1596.18(8) Å3, Z = 4, R gt (F) = 0.0385, wR ref (F 2 ) = 0.0973, T = 190 K.

Two new macrocyclic Schiff bases m 3 and m 4 (m 3 = 1,5-diaza-2,4:7,8:17,18-tribenzo-9,16-dioxa-cyclononadeca-1,5-dien; m 4 = 1,5-diaza-2,4:7,8:18,19- tribenzo-9,17-dioxa-cycloeicosa-1,5-dien) were synthesized by reactions of the appropriate dialdehyde and diamine. The compounds were characterized by means of FT-IR and NMR spectroscopy, TG/DSC and elemental analysis. The crystal and molecular structures were determined by the single crystal X-ray diffraction method. Both molecules are N2O2-donor macrocyclic Schiff bases with 19 and 20 atoms in their inner macrocyclic rings and of a similar molecular structure. A different crystal packing arrangement of the molecules is caused by the differences in macrocycle planarity. The extraction experiments of the aforementioned compounds were performed by using metallic picrate salts, and simultaneously for the previously synthesized 17- and 18- membered macrocyclic analogues (m 2 and m 1). The metal cation extractability was determined for m 1, m 2, m 3 and m 4 by UV–Vis spectrophotometry in order to find correlation of structural features and the extraction capabilities of the Schiff bases. The highest metal cation extraction percentage was determined for the Hg2+ ion in the case of the m 2 macrocycle.

(7-Hydroxy-2-oxo-2-chromen-4-yl)-acetic acid methyl ester H ( 1 ) upon reaction with ethyl bromoacetate furnishes (7-ethoxycarbonylmethoxy-2-oxo-2 H -chromen-4-yl)-acetic acid methylester ( 2 ), which on treatment with 100% hydrazine hydrate yields (7-hydrazinocarbonylmethoxy-2-oxo-2 H -chromen-4-yl)-acetic acid hydrazide (). The 3condensation of compound 3 with different aromatic aldehydes afforded a series of [7-(arylidenehydrazinocarbonylmethoxy)-2-oxo-2 H -chromen-4-yl]-acetic acid arylidene-hydrazide Schiff’s bases 4a-k. Cyclo-condensation of compounds 4a-k with 2-mercapto-acetic acid in N,N -dimethylformamide in the presence of anhydrous ZnCl 2 affords N -(2-aryl-4-oxothiazolidin-3-yl)-2-(4-(2-aryl-4-oxothiazolidin-3-ylcarbamoyl)-methyl)-2-oxo-2 H -chromen-7-yloxy)-acetamides 5a-k . Structure elucidation of the products has been accomplished on the basis of elemental analysis, IR, 1 H-NMR and 13 C-NMR data. Compounds 4a-k and 5a-k will be screened for their antibacterial activity against both Gram-positive and Gram-negative bacteria and the results reported elsewhere in due course.

Two N2O2-donor macrocyclic Schiff bases mD1 and mD2 (mD1 = 1, 5-diaza-2, 4:7, 8:16, 17-tribenzo-9, 15-dioxa-cyclooctadeca-1, 5-dien ; mD2 = 1, 5-diaza-2, 4:7, 8:15, 16- tribenzo-9, 14-dioxa-cycloheptadeca-1, 5-dien) were prepared by the [1+1] cyclocondensation reaction of the corresponding dialdehyde and diamine. The reactions of the prepared macrocycles with silver nitrate led to formation of unique (regarding the N2O2-donors) silver coordination polymers, AgmD1 and AgmD2. All synthesized compounds were characterized by vibrational spectroscopy (IR), thermal methods (TG/DSC) and the ligands additionally by NMR. The crystal and molecular structures of the macrocycles and the silver coordination polymers were determined by the single crystal X-ray diffraction method. The molecular structure of the macrocycles is found to be rather similar, but with significant differences in the crystal packing arrangement due to slight deviations from planarity. In the complex AgmD1 each silver atom is coordinated by two imino nitrogen atoms of the neighbouring ligand molecules and, with an oxygen atom of the nitrate group, thus producing an infinite zig-zag polymeric chain. The silver atoms in AgmD2 are tetrahedrally coordinated with two N-bound ligand molecules and two nitrate anions. This form of coordination produces an additional metallacyclic ring. The polymeric structure is formed through connection of the metallacyclic rings by bridging nitrate anions. Slight deviations in the conformation of the macrocyclic ligands have significant impact upon the coordination mode and topology of the silver coordination polymer structures.

The title compound, C18H18O4, is a triclinic polymorph of the previously reported monoclinic polymorph [Han & Zhen (2005). Acta Cryst. E61, o4358–o4359]. In the crystal of the triclinic polymorph, molecules are linked by two pairs of C—H...O hydrogen bonds, forming a two-dimensional network parallel to (102), and enclosing loops with graph set motifs of R22(8) and R22(6).

In the title compound, C20H19O4, the benzene rings, linked via five methylene C atoms, form a dihedral angle of 77.28 (6)°. In the crystal, molecules are linked via pairs of weak C—H...O interactions [graph set R22(6)] into dimers that are further connected by additional weak C—H...O interactions [graph sets R22(14), R22(26) and R22(6)].

Two novel symmetrical bis-Schiff bases ((1E)-1-N-{; ; ; ; [4-(4-{; ; ; ; [(E)-N-(2-aminophenyl) carboxyimidoyl] phenoxy}; ; ; ; butoxy) phenyl]methylidene}; ; ; ; benzene-1, 2-diamine (compound 1) and (1E)-1-N-{; ; ; ; [4-(4-{; ; ; ; [(E)-N-(4-aminophenyl) carboxyimidoyl] phenoxy}; ; ; ; butoxy) phenyl]methylidene}; ; ; ; benzene-1, 4-diamine (compound 2) were synthesized and characterized by means of single-crystal X-ray diffraction (1), FT-IR and NMR spectroscopy (1, 2), elemental (1, 2), TG/DSC and electrochemical analysis (1, 2). The prepared compounds are positional isomers that display very different electrochemical behaviour. Electrochemical study has shown that the oxidation of the investigated Schiff base (1) is irreversible, diffusion controlled process and that the oxidation products are adsorbed on the glassy carbon electrode surface. Oxidation of a Schiff base (2) is reversible (follows EC reaction mechanism), diffusion controlled and the oxidation products are also adsorbed on the glassy carbon electrode surface. Considering molecular structure of compounds, molecule 1 is planar, with small deviation of atoms from the calculated plane. The planarity of molecule 1 is stabilized by untypical intramolecular interaction of amino and imino nitrogen atoms. In the crystal, the molecules are primarily linked by hydrogen bonds involving primary amino groups and weak C-H•••π interactions. Consequently, these interactions are arranging molecules into herringbone packing motif. Crystal structure of molecule 2 could not be determined but it is predicted based upon similarity with molecule 1 and interpretation of the spectral data (NMR and FTIR).