Solid-to-solid polymorphic phase transitions in two isostructural Bi(III) complexes with 1-phenylethyl-N-ethylthiosemicarbazide and halogens.

Two isostructural (in room temperature) complexes of Bi(III) with halogens and sulfur ligands have been investigated in terms of the solid-to-solid phase transitions indicated by temperature. Both chloride and bromide (X) complexes of the general formula (µ2-X)-(BiX2L2)2 exhibit some phase transitions between 100 and 333 K, which, apart from the numerous similarities, show significant differences, which have been noted and analyzed in detail in this paper by using different techniques, i.e., powder and single crystal diffraction or DSC. The obtained results have also been collated with those obtained for solid solutions of both complexes.

Deoxyfluorinating reagents as tools for γ-amino-α-hydroxyphosphonate modification.

Herein, we would like to present deoxyfluorinating reagents such as DAST and PyFluor and their successful use as tools for selective modification of γ-amino-α-hydroxyphosphonates. Depending on the deoxyfluorinating reagent applied, an intramolecular cyclization leading to phosphonates containing the 1,3-oxazinan-2-one moiety or direct nucleophilic deoxyfluorination yielding the α-fluorinated derivatives of γ-aminophosphonates was observed. The obtained compounds may be used as precursors in the preparation of medicinally important compounds e.g., dipeptide analogues or scaffolds containing the 1,3-oxazinan-2-one group.

Synthesis and Spectroscopic Investigations of Schiff Base Ligand and Its Bimetallic Ag(I) Complex as DNA and BSA Binders.

Generation of well-defined potential metallotherapeutics for cancer treatment, one of the most population-threatening diseases, is challenging and an active area of modern research in view of their unique properties and thus multiple possible pathways of action in cells. Specifically, Schiff base ligands were recognized as very promising building blocks for the construction of stable and active complexes of numerous geometries and topologies. Incorporation of Ag(I) ions allows for the formation of flat complexes with potential unoccupied coordination sites, thus giving rise to specific interactions between the metallotherapeutic and biomolecule of interest. Herein, we present the design, synthesis and characterization of new Schiff base ligand L and its Ag(I) bimetallic complex [Ag2L2]2+ with two planar moieties formed around the metal ions and connected through cyclohexane rings, confirmed by X-ray measurements. The compounds were described in context of their potential use as anticancer drugs through DNA and BSA binding pathways by several spectroscopic methods (CD, UV-Vis, fluorescence). We revealed that both, L and [Ag2L2]2+, interact with similar affinity with CT-DNA (Kb~106 M-1), while they differ in the type and strength of interactions with the model albumin-BSA. [Ag2L2]2+ binds BSA in both a dynamic and static manner with the Ksv = 8.8 × 104 M-1 in the Trp-134 and Trp-213 sites, whereas L interacts with BSA only dynamically (KSV = 2.4 × 104 M-1). This found further confirmation in the CD studies which revealed a reduction in α-helix content in the albumin of 16% in presence of [Ag2L2]2+.

Reductive Electropolymerization and Electrochromism of Iron(II) Complex with Styrene-Based Ligand.

The benzimidazole-based ligand containing polymerizable styrene group has been prepared via condensation of picolinaldehyde derivative containing styrene moiety and benzimidazole-based hydrazine. The ligand reacted with iron(II) tetrafluoroborate and iron(II) trifluoromethanesulfonate giving red-brown complexes of Fe(II) ions of formula [FeL2]X2, where X = CF3SO3- (1) or BF4- (2). Reductive electropolymerization was used to obtain a thin layer of the polymeric complex, poly-1. Further investigation of electrochemical properties of the compound by cyclic voltammetry showed two quasi-reversible redox processes assigned to electrooxidation and electroreduction of the polymer. Spectroelectrochemical measurements confirmed that the polymer undergoes the color changes during oxidation and reduction process. The polymer in its neutral state (Fe(II)) is yellow and it exhibits absorption band at 370 nm, after oxidation to Fe(III) state absorption band shifts to 350 nm and the polymer is almost colorless. While the metal ions are reduced to Fe(I) absorption band at around 410 nm has been observed and the polymer changed its color to intense yellow. The stability of the polymer during multiple oxidation/reduction cycles has also been investigated.

Bases, solvates and salts: new benzimidazole- and pyridine-scaffolded ligands.

The intermolecular interactions in the structures of a series of Schiff base ligands have been thoroughly studied. These ligands can be obtained in different forms, namely, as the free base 2-[(2E)-2-(1H-imidazol-4-ylmethylidene)-1-methylhydrazinyl]pyridine, C10H11N5, 1, the hydrates 2-[(2E)-2-(1H-imidazol-2-ylmethylidene)-1-methylhydrazinyl]-1H-benzimidazole monohydrate, C12H12N6·H2O, 2, and 2-{(2E)-1-methyl-2-[(1-methyl-1H-imidazol-2-yl)methylidene]hydrazinyl}-1H-benzimidazole 1.25-hydrate, C13H14N6·1.25H2O, 3, the monocationic hydrate 5-{(1E)-[2-(1H-1,3-benzodiazol-2-yl)-2-methylhydrazinylidene]methyl}-1H-imidazol-3-ium trifluoromethanesulfonate monohydrate, C12H13N6+·CF3O3S-·H2O, 5, and the dicationic 2-{(2E)-1-methyl-2-[(1H-imidazol-3-ium-2-yl)methylidene]hydrazinyl}pyridinium bis(trifluoromethanesulfonate), C10H13N52+·2CF3O3S-, 6. The connection between the forms and the preferred intermolecular interactions is described and further studied by means of the calculation of the interaction energies between the neutral and charged components of the crystal structures. These studies show that, in general, the most important contribution to the stabilization energy of the crystal is provided by π-π interactions, especially between charged ligands, while the details of the crystal architecture are influenced by directional interactions, especially relatively strong hydrogen bonds. In one of the structures, a very interesting example of the nontypical F...O interaction was found and its length, 2.859 (2) Å, is one of the shortest ever reported.

Cocrystals of pyrazine and benzene polycarboxylic acids.

The crystal structures of four cocrystals of pyrazine with benzene polycarboxylic acids were determined, namely pyrazine-phthalic (benzene-1,2-dicarboxylic) acid (1/1), C4H4N2·C8H6O4 (1), pyrazine-hemimellitic (benzene-1,2,3-tricarboxylic) acid (1/1), C4H4N2·C9H6O6 (2), pyrazine-hemimellitic acid-water (1/2/2), C4H4N2·2C9H6O6·2H2O (2a), and pyrazine-pyromellitic (benzene-1,2,4,5-tetracarboxylic) acid (3/1), 3C4H4N2·C10H6O8 (3). In all cases, infinite chains of alternating acid and base molecules, bonded by O-H...N hydrogen bonds, are formed. However, the details of the supramolecular structures are different. The additional carboxylic acid groups in the tri- and tetracarboxylic acids participate in hydrogen bonding with neighbouring acid molecules (in 2), water molecules, which makes the structure more complicated (in 2a), or with additional pyrazine molecules (in 3). π-π interactions between aromatic rings help organize the crystal architectures in all cases except for hydrate 2a. In that case, the hydrogen-bond-enriched structure enforces a disposition of the rings in which no stacking is observed. The Hirshfeld surface analysis allows better visualization of the differences between the structures by fingerprint plots in particular.

Charge-density analysis using multipolar atom and spherical charge models: 2-methyl-1,3-cyclopentanedione, a compound displaying a resonance-assisted hydrogen bond.

The experimental charge-density distribution in 2-methyl-1,3-cyclopentanedione in the crystal state was analyzed by synchrotron X-ray diffraction data collection at 0.33 Šresolution. The molecule in the crystal is in the enol form. The experimental electron density was refined using the Hansen-Coppens multipolar model and an alternative modeling, based on spherical atoms and additional charges on the covalent bonds and electron lone-pair sites. The crystallographic refinements, charge-density distributions, molecular electrostatic potentials, dipole moments and intermolecular interaction energies obtained from the different charge-density models were compared. The experimental results are also compared with the theoretical charge densities using theoretical structure factors obtained from periodic quantum calculations at the B3LYP/6-31G** level. A strong intermolecular O-H···O hydrogen bond connects molecules along the [001] direction. The deformation density maps show the resonance within the O=C-C=C-OH fragment and merged lone pair lobes on the hydroxyl O atom. This resonance is further confirmed by the analysis of charges and topology of the electron density.

1-[Bis(4-fluoro-phen-yl)meth-yl]piperazine.

In the title mol-ecule, C(17)H(18)F(2)N(2), the dihedral angle between the benzene rings is 73.40 (3)°. The piperazine ring is close to an ideal chair conformation and the N-H hydrogen is in an equatorial position. In the crystal, molecules are linked via weak C-H⋯F hydrogen bonds.

(R)-Doxylaminium (R,R)-tartrate.

IN THE TITLE COMPOUND (SYSTEMATIC NAME: (R)-dimeth-yl{2-[1-phenyl-1-(pyridin-2-yl)eth-oxy]eth-yl}aza-nium (R,R)-3-carb-oxy-2,3-dihy-droxy-propano-ate), C(17)H(23)N(2)O(+)·C(4)H(5)O(6) (-), the doxylaminium cation is protonated at the N atom. The tartrate monoanions are linked by short, almost linear O-H⋯O hydrogen bonds into chains extended along [100]. These chains are inter-linked by anion-pyridine O-H⋯N hydrogen bonds into a two-dimensional grid structure. WeakC-H⋯O inter-actions also play a role in the crystal packing. An intra-molecular hy-droxy-carboxyl-ate O-H⋯O hydrogen bond influences the conformation of the anion: the hydrogen-bonded fragment is almost planar, the maximum deviation from the mean plane being 0.059 (14) Å. In the cation, the aromatic rings are almost perpendicular [dihedral angle = 84.94 (8)°] and the conformation of the O-C-C-N chain is gauche(-), the dihedral angle is -76.6 (2)°. The absolute configuration was assigned on the basis of known chirality of the parent compound.

4-[(4-Benzyl-oxybenzyl-idene)amino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one.

In the title mol-ecule, C(25)H(23)N(3)O(2), two terminal phenyl rings are twisted by 50.20 (6) and 71.26 (5)° from the mean plane (r.m.s. deviation = 0.032 Å) of the central benzyl-idene-amino-pyrazolone fragment. The N atoms of the pyrazole ring have a pyramidal environment, the sums of the valence angles around them being 353.5 (2) and 347.3 (2)°. The crystal structure is stabilized by C-H⋯O interactions.

Tramadolium picrate.

In the title salt {systematic name: [2-hy-droxy-3-(3-meth-oxy-phen-yl)cyclo-hexyl-meth-yl]dimethyl-aza-nium 2,4,6-trinitro-phenol-ate}, C(16)H(26)NO(2) (+)·C(6)H(2)N(3)O(7) (-), the cation is protonated at the N atom. The cyclo-hexane ring adopts a chair conformation with the hy-droxy substituent in an axial position. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the cations and anions into supra-molecular chains along [100].

Ethyl N-(2-benzoyl-4-chloro-phen-yl)-ethane-carboximidate.

In the title compound, C(17)H(16)ClNO(2), the N=C-O-C-C fragment is planar within 0.029 (1) Å, and makes dihedral angles of 66.71 (8) and 59.61 (8)° with the planes of the chloro-phenyl and benzoyl rings, respectively. The carbonyl C=O bond is not coplanar with either of the aromatic rings; it makes angles of 42.5 and 23.5° with the normals to the ring planes. In the crystal, very weak C-H⋯O, C-H⋯Cl, C-H⋯π and π-π [inter-planar distance = 3.53 (1) Å] inter-actions are observed.

Bis[µ-4-(2-oxidobenzyl-idene)thio-semi-carbazidato-κS,N,O:O]bis-[(pyridine-κN)zinc].

In the title compound, [Zn(2)(C(8)H(7)N(3)OS)(2)(C(5)H(5)N)(2)], the Zn(2)O(2) ring has a flattened roof shape, with the roof angle equal to 10.10 (6)°. The thio-semicarbazones act as tridentate ligands to one Zn(II) atom, with the O atoms additionally in bridging positions to the second Zn(II) atom. Both Zn(II) atoms are five-coordinated; the coordination polyhedra are close to square pyramids, with the pyridine N atoms at apical positions. Two inter-molecular N-H⋯N and one relatively weak N-H⋯S hydrogen bond, together with C-H⋯S weak inter-actions, connect the mol-ecules into a three-dimensional network.

[S-Allyl-4-(4-hy-droxy-2-oxidobenzyl-idene-κO)-1-(2-oxidobenzyl-idene-κO)isothio-semicarbazidato-κN,N](ethanol-κO)dioxido-uranium(VI) ethanol monosolvate.

In the title compound, [U(C(18)H(15)N(3)O(3)S)O(2)(C(2)H(5)OH)]·C(2)H(5)OH, the U(VI) ion is in a distorted penta-gonal-bipyramidal coordination geometry, with two oxide O atoms in axial sites. Two N and two O atoms of the tetra-dentate ligand and an O atom of an ethanol ligand form the equatorial plane. The dihedral angle between the mean planes of the two benzene rings is 34.8 (3)°. In the crystal, relatively strong O-H⋯O hydrogen bonds connect the complex and ethanol solvent mol-ecules into alternating centrosymmetric R(2) (2)(8) and R(4) (4)(16) ring motifs, forming chains along [100]. Weak inter-molecular C-H⋯O hydrogen bonds are also present.

(2E)-3-(3-Bromo-4-meth-oxy-phen-yl)-1-(4-methyl-phen-yl)prop-2-en-1-one.

The overall shape of the mol-ecule of the title compound, C(17)H(15)BrO(2), can be described by the dihedral angles between three planar fragments: 1-bromo-2-meth-oxy-phenyl ring [maximum deviation = 0.003 (2) Å], the central prop-2-en-1-one chain [maximum deviation = 0.005 (2) Å], and the methyl-phenyl ring [maximum deviation = 0.004 (2) Å]. The terminal planes are twisted by 10.37 (12)°, while the central plane is almost coplanar with the methyl-phenyl ring [3.30 (13)°], but the dihedral angle with the other phenyl ring is significantly larger [8.76 (16)°]. In the crystal, mol-ecules are linked into chains along [001] by three C-H⋯O hydrogen bonds. These chains inter-act with each other by means of weak π-π contacts [centroid-centroid distances = 3.73 (1) and 3.44 (1) Å]. An inter-molecular C-H⋯Br inter-action also occurs.

(2E)-3-(3-Bromo-4-meth-oxy-phen-yl)-1-(4-fluoro-phen-yl)prop-2-en-1-one.

In the title compound, C(16)H(12)BrFO(2), the dihedral angle between the aromatic rings is 23.75 (12)° and the dihedral angle between the prop-2-en-1-one fragment and the fluorobenzene ring is 20.9 (2)°. In the crystal, only van der Waals interactions occur.

(1RS,6SR)-Ethyl 4-(4-chloro-phen-yl)-6-(4-fluoro-phen-yl)-2-oxocyclo-hex-3-ene-1-carboxyl-ate toluene hemisolvate.

In the crystal structure of the title compound, C(21)H(18)ClFO(3)·0.5C(7)H(8), the toluene solvent mol-ecules occupy special positions on centres of symmetry, and consequently are disordered across this site. The cyclo-hexene ring has a slightly distorted sofa conformation; the two benzene rings are inclined by 72.90 (7)° and their planes make dihedral angles of 30.09 (10) (chloro-phen-yl) and 88.13 (6)° (fluoro-phen-yl) with the approximately planar part of the cyclo-hexenone ring [maximum deviation from plane through five atoms is 0.030 (2) Å, the sixth atom is 0.672 (3)Å out of this plane]. Weak inter-molecular C-H⋯O and C-H⋯X (X = F, Cl) inter-actions join mol-ecules into a three-dimensional structure. Also, a relatively short and directional C-Cl⋯F-C contact is observed [Cl⋯F = 3.119 (2) Å, C-Cl⋯F = 157.5 (2)° and C-F⋯Cl 108.3 (2)°]. The solvent mol-ecules fill the voids in the crystal structure and are kept there by relatively short and directional C-H⋯π inter-actions.

(1RS,6SR)-Ethyl 4,6-bis-(4-fluoro-phen-yl)-2-oxocyclo-hex-3-ene-1-carboxyl-ate.

In the crystal structure of the title compound, C(21)H(18)F(2)O(3), the cyclo-hexene ring has a slightly distorted sofa conformation; the two benzene rings are inclined by 76.27 (8)° and their planes make dihedral angles of 16.65 (10) and 67.53 (7)° with the approximately planar part of the cyclo-hexenone ring [maximum deviation 0.044 (2) Å, while the sixth atom is displaced by 0.648 (3) Šfrom this plane]. In the crystal, weak inter-molecular C-H⋯O, C-H⋯F and C-H⋯π inter-actions join mol-ecules into a three-dimensional structure.

1-Methyl-piperazine-1,4-diium dipicrate.

IN THE CRYSTAL STRUCTURE OF THE TITLE COMPOUND [SYSTEMATIC NAME: 1-methyl-piperazine-1,4-diium bis-(2,4,6-trinitro-phen-ol-ate)], C(5)H(14)N(2) (2+)·2C(6)H(2)N(3)O(7) (-), the ionic components are connected by relatively strong N-H⋯O hydrogen bonds into centrosymmetric six-membered conglomerates, which comprise two dications and four anions. Besides Coulombic inter-actions, only weak C-H⋯O inter-actions and some stacking between picrates (separation between the planes of ca. 3.4 Šbut only a small overlapping) can be identified between these 'building blocks' of the crystal structure. The piperazine ring adopts a chair conformation with the methyl substituent in the equatorial position. In the picrate anions, the twist angles of the nitro groups depend on their positions relative to the phenolate O atom: it is much smaller for the NO(2) groups para to the C-O(-) group [15.23 (9)and 3.92 (14)°] than for the groups in the ortho positions [28.76 (13)-39.84 (11)°].

(1RS,6SR)-Ethyl 4-(2,4-dichloro-phen-yl)-6-(4-fluoro-phen-yl)-2-oxocyclo-hex-3-ene-1-carboxyl-ate.

There are two symmetry-independent mol-ecules in the asymmetric unit of the title compound, C(21)H(17)Cl(2)FO(3). Both these mol-ecules are very similar: the normal probability plots for bond lengths, angles and even for torsion angles show that the differences are of a statistical nature. A pseudocentre of symmetry is located between the symmetry-independent mol-ecules at [0.245 (1), 0.535 (19), 0.909 (1)]. The cyclo-hexene rings have slightly distorted sofa conformations in both mol-ecules and the two benzene rings are inclined by dihedral angles of 61.33 (14) and 62.85 (14)°. In the crystal, relatively short inter-molecular C-H⋯O inter-actions join mol-ecules into homomolecular (i.e. ⋯AAA⋯ and ⋯BBB⋯) chains along the b axis. These chains are inter-connected by further heteromolecular C-H⋯O inter-actions.