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A novel Zn(II) binuclear complex with 4-hydroxyquinoline-2-carboxylic acid as a ligand (4hqc) has been prepared. Due to the presence of strong O H⋯O− hydrogen bond interactions (-55.0 kJ/mol to −62.5 kJ/mol) hydroxyl oxygen atom is deprotonated and uncoordinated to the Zn(II) cation. [Display omitted] Investigation of strong hydrogen bonds in crystal engineering is extensively used for the preparation of intriguing novel pharmaceutical co-crystals and ionic compounds. Strong O H⋯O− hydrogen bonds in phenolates were recently recognized as a promising supramolecular synthon for the preparation of novel ionic co-crystals, and phenolates as promising catalysts and reducing agents. Investigations of complex compounds containing uncoordinated phenolate are exceptionally rare and this particular research area is yet unexplored. As part of our continuous investigations in the supramolecular chemistry of coordination compounds, we have prepared a novel Zn(II) binuclear complex with 4-hydroxyquinoline-2-carboxylic acid as a ligand (4hqc). The compound was characterized by IR-spectroscopy, and molecular and crystal structure was determined by the single-crystal X-ray diffraction method. The compound is a binuclear Zn complex, with each Zn(II) ion coordinated by one 4hqc ligand and two water molecules in the distorted square pyramidal arrangement. The central Zn 2 (µ -O) 2 unit is planar and Zn ions are bridged by monodentatelly coordinated carboxylate oxygen atoms. In the crystal, the discrete binuclear units are primarily connected by strong O H⋯O− hydrogen bond interactions that involve deprotonated hydroxyl oxygen atoms and coordinated water molecules. The 3D structure is additionally stabilized by offset face-to-face π ⋯ π interactions. Additional structural analysis has shown that geometrical parameters of O H⋯O− hydrogen bonds are very similar to those in phenolate co-crystals, thus confirming the presence of phenolate in the complex. The calculated lattice energy of the compound was found to be unusually high (-505.56 kJ/mol), and O H⋯O− bond energies were estimated to be in the range from −55.0 kJ/mol to −62.5 kJ/mol. By comparison to previously reported phenolate coordination compounds, it was proposed that such compounds could be synthesized in mildly alkaline conditions, ligand: metal stoichiometric ratio 1:1, and with ligands bearing carboxylate, imine, or pyridine groups separated from phenol group by hydrogen atom or other bulkier groups. [ABSTRACT FROM AUTHOR]

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: [CdX 2 (pia)] n (X = Cl ( 1 ), Br ( 2 ), I ( 3 ). Cadmium(II) sulphate gave [Cd(SO 4 )(pia)(H 2 O) 3 ] ·2H 2 O ( 4) while cadmium(II) nitrate in the presence of perchlorate ions gave mixed complex [Cd(pia) 3 (H 2 O)](NO 3 )(ClO 4 ) ( 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 R 2 2 (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. [ABSTRACT FROM AUTHOR]

A novel N 4 O 4 -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×I 2 ). From the spectroscopic, crystal structure, and thermal analysis studies of 1×CLF , 1×DCM and 1×I 2 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 CO 2 at 298 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel trinuclear iron(III) acetate as with uncoordinated hexamine. • The complex has been structurally characterized by single crystal X-ray diffraction. • The impact of hexamine on intermolecular interactions was studied. • High-spin iron ions in +3 oxidation state with non-Curie-like behaviour. • Antiferromagnetic interactions between the three individual Fe(III) ions. Structural characterization of novel Fe(III) basic acetate with 1,3,5,7-tetraazaadamantane (hexamine – HEX), [Fe 3 (μ 3 -O)(OAc) 6 (H 2 O) 3)](NO 3)(HEX) 2 (H 2 O) 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, Mössbauer 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 S t = 1/2 per trinuclear cluster. EPR spectroscopy confirmed the formation of a S t = 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 Mössbauer 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. [ABSTRACT FROM AUTHOR]

• Silver complexes. • N,O -donor macrocycles. • Anion and ligand influence. • Exo-coordinated. • SC-XRD, TG/DSC, FTIR analysis. Three novel silver(I) complexes with N 2 O 2 -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, AgL1ClO 4 , and (AgL2ClO 4) 2 ·CH 2 Cl 2. The reaction of L2 with silver nitrate resulted in a formation of discrete binuclear silver complex (AgL2NO 3) 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 AgL1ClO 4 , 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 (AgL2ClO 4) 2 ·CH 2 Cl 2 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 (AgL2NO 3) 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. [ABSTRACT FROM AUTHOR]

The crystal and molecular structure of di-substituted pyridine-2,6-dicarboxylic acid (pdc) hydrazide derivative containing quinazoline moieties was determined. A non-planar molecule with a specific N , N , N -chelate binding site. A novel Cu(II) complex with the ligand molecule was prepared. Coordination geometry is a square pyramid, hydrazide atoms are in deprotonated anionic form, and quinazoline N atoms are in protonated cationic form. [Display omitted] • Pyridine-2,6-dicarboxylic acid hydrazide quinazoline derivative. • Ligand with N , N , N -chelate binding sites suitable for the complexation of metal ions. • Square pyramidal Cu(II) complex compound. • Hydrazide atoms in the anionic form, and N -quinazoline atoms in the cationic form. • Dimer motif in the structure of the ligand and π ⋯ π interactions in the Cu(II) complex. Crystal and molecular structures of novel pyridine-2,6-dicarboxylic acid (pdc) hydrazide derivative (H 2 L) dimethanol solvate (H 2 L = N,N'-bis(2-methyl-4-oxoquinazolin-3(4H)-yl)pyridine-2,6-dicarboxamide) and its copper(II) complex were determined by the single-crystal X-ray diffraction. In the crystal structure, these non-planar molecules form specific cavities that are populated by methanol molecules (held by O H⋯O and N H⋯O hydrogen bonds). Additional stabilization is achieved through a series of offset face-to-face π ⋯ π interactions between aromatic moieties. The compound is the first structurally described pdc hydrazide derivative containing quinazoline moieties. The reaction of the H 2 L with copper(II) chloride in methanol resulted in the formation of a new methanol/water solvate containing discrete CuCl 2 L molecules. Cu(II) ion is coordinated by three nitrogen atoms (two from hydrazide and one from pyridine moieties) in a chelate fashion. Two chloride ions complete distorted square pyramidal coordination geometry. Unlike in H 2 L molecules, in CuCl 2 L the hydrazide N -atoms are deprotonated, and coordinated to Cu(II), while quinazoline N -atoms are protonated. In its crystal structure, CuCl 2 L molecules form dimeric motifs via O H⋯O, N H⋯O, O H⋯Cl hydrogen bond interactions. The adjacent dimers are stacked along the crystallographic b - and c -axis through N H⋯Cl and offset face-to-face π ⋯ π interactions. The FT-IR spectra analysis indicates a significant shift of C O stretching vibrations of uncoordinated carbonyl groups, that can be attributed to the electron-withdrawing effect of Cu(II) ion. The TG analysis indicates that the weakly bounded solvent molecules evaporate at lower temperatures and that the compound is stable up to 300 °C. [ABSTRACT FROM AUTHOR]

(i) Monosubstituted dipicolinic acid hydrazide derivative. (ii) N,N,O -tridentate ligand. Co(III) and Cr(III) complexes. (iii) Isostructural octahedral complexes with similar crystal packing. (iv) SC-XRD, TG/DSC, FTIR, NMR, CV analyses. A novel monosubstituted dipicolinic acid hydrazide derivative ( H 2 L = 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. [ABSTRACT FROM AUTHOR]

The influence of 4 different anions on hydrogen bonding interactions and energetic properties Cd picolinamide complexes have been studied. Bulky, tetrahedral anions inhibit the formation of strong head-to-head amide interaction and azide anion promotes the formation of insensitive energetic coordination polymer. [Display omitted] A novel group of energetic compounds, known as energetic coordination polymers (ECPs), can be rationally designed by introducing of highly energetic ions like ClO 4 - , N 3 – , NO 3 – and NO 2 – 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 ](ClO 4) 2 ·2H 2 O (1), [Cd(NO 3)(ac)(pia) 2 ] (2), [Cd(NO 2) 2 (pia) 2 ] (3), [Cd 2 (μ 1,1 -N 3) 4 (pia) 2 ] n [Cd(μ 1,1 -N 3) 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 (ClO 4 - and SO 4 2-) 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. [ABSTRACT FROM AUTHOR]

The removal and detection of highly toxic and environmentally harmful gases such as SO 2 , H 2 S and CO 2 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 N 4 O 4 -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 NH 3 , SO 2 , Cl 2 , CO 2 and H 2 S. Five novel inclusion compounds 1xNH 3 , 1xSO 2 , 1xCl 2, 1xCO 2 and 1xH 2 S were prepared by a single-crystal to single-crystal (SC-SC) transformation. Single-crystal X-ray diffraction (SCXRD) analysis of 1xCO 2 and 1xNH 3 inclusion compounds have shown that CO 2 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 1xNH 3 were observed. The relative thermal stabilities of the host-guest systems (T on – T b parameter) is in the range from 93 (1xNH 3) to 132 °C (1xH 2 S), 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 CO 2 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. Novel inclusion complexes of porous 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) were prepared by single-crystal to single-crystal (SC-SC). Inclusion complexes with CO 2 , NH 3 , SO 2 , Cl 2 and H 2 S were prepared and characterized by thermal analysis, spectroscopy (NMR and FT-IR) and the single-crystal X-ray diffraction (SCXRD). [Display omitted] • CO 2 , NH 3 , SO 2 , Cl 2 and H 2 S inclusion compounds were prepared by single-crystal to single-crystal (SC-SC) transformation. • Crystal structures were determined for CO 2 (1xCO 2) and NH 3 (1xNH 3) inclusion compounds. • In 1xCO 2 , the CO 2 molecules form weak C–O ... π interactions to the host. • T on – T b parameter is 93 °C, 110 °C, 120 °C and 132 °C for 1xNH 3 , 1xSO 2 , 1xCl 2 and 1xH 2 S , respectively. • GCMC simulations indicate maximum absence of strong host-guest interactions. [ABSTRACT FROM AUTHOR]

Synthesis, crystal structure and electrochemical characterization of novel CdX 2 (X = Br, I) picolinamide complexes are presented. Prepared coordination compounds (CdBr 2 (pia) 2 and CdI 2 (pia) 2) are isostructural displaying different electrochemical behaviour – two electron transfer reactions in complex CdI 2 (pia) 2 at −0.55 V and −0.83 V, indicating two redox active centers in the molecule, while complex CdBr 2 (pia) 2 appears to be electro-inactive. • Cadmium(II) complexes. • 2-Picolinamide. • Electrochemical properties. • Hirshfeld surface analysis. • SC-XRD, TG/DSC, FTIR analysis. Two novel discrete cadmium(II) complexes, namely [CdBr 2 (pia) 2 ] (1) and [CdI 2 (pia) 2 ] (2) were prepared by reactions of aqueous solutions of CdX 2 (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 N H⋯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 C H⋯O, C H⋯N and N H⋯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. [ABSTRACT FROM AUTHOR]

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. Image, graphical abstract [ABSTRACT FROM AUTHOR]