Supramolecular Diversity, Theoretical Investigation and Antibacterial Activity of Cu, Co and Cd Complexes Based on the Tridentate N,N,O-Schiff Base Ligand Formed In Situ.

The four new complexes, [Cu(HL1)(L2)Cl] (1), [Cu(HL1)(L1)]∙Cl∙2H2O (2), [Co(L1)2]∙Cl (3) and [Cd(HL1)I2]∙dmso (4), have been prepared by one-pot reactions of the respective chloride or iodide metal salt with a non-aqueous solution of the polydentate Schiff base, HL1, resulted from in situ condensation of benzhydrazide and 2-pyridinecarboxaldehyde, while a ligand HL2, in case of 1, has been formed due to the oxidation of 2-pyridinecarboxaldehyde under reaction conditions. The crystallographic analysis revealed that the molecular building units in 1-4 are linked together into complex structures by hydrogen bonding, resulting in 1D, 2D and 3D supramolecular architectures for 1, 2 and 4, respectively, and the supramolecular trimer for 3. The electronic structures of 1-4 were investigated by the DFT theoretical calculations. The non-covalent interactions in the crystal structures of 1-4 were studied by means of the Hirshfeld surface analysis and the QTAIM theory with a special focus on the C-H⋯Cl bonding. From the DFT/DLPNO-CCSD(T) calculations, using a series of charged model {R3C-H}0⋯Cl- assemblies, we propose linear regressions for assessment of the interaction enthalpy (ΔH, kcal mol-1) and the binding energy (BE, kcal mol-1) between {R3C-H}0 and Cl- sites starting from the electron density at the bond critical point (ρ(rBCP), a.u.): ΔH = -678 × ρ(r) + 3 and BE = -726 × ρ(r) + 4. It was also has been found that compounds 1, 3 and 4 during in vitro screening showed an antibacterial activity toward the nine bacteria species, comprising both Gram-positive and Gram-negative, with MIC values ranging from 156.2 to 625 mg/L. The best results have been obtained against Acinetobacter baumannii MßL.

Increasing Structural Dimensionality of Alkali Metal Fluoridotitanates(IV).

Reactions between AF (A = Li, Na, K, Rb, Cs) and TiF4 (with starting n(AF):n(TiF4) molar ratios in the range from 3:1 to 1:3) in anhydrous hydrogen fluoride yield [TiF6]2-, [TiF5]-, [Ti4F19]3-, [Ti2F9]-, and [Ti6F27]3- salts. With the exception of the A2TiF6 compounds, which consist of A+ cations and octahedral [TiF6]2- anions, all of these materials arise from the condensation of TiF6 units. The anionic part in the crystal structures of A[TiF5] (A = K, Cs) and A[TiF5]·HF (A = Na, K, Rb) is composed of infinite ([TiF5]-)∞ chains built of TiF6 octahedra sharing joint vertices. Each structure shows a slightly different geometry of the ([TiF5]-)∞ chains. The crystal structure of Na[Ti2F9]·HF is constructed from polymeric ([Ti2F9]-)∞ anions that appear as two parallel infinite zigzag chains comprising TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the other chain through a shared fluorine vertex. Slow decomposition of single crystals of K4[Ti8F36]·8HF and Rb4[Ti8F36]·6HF ( Shlyapnikov , I. M. ; et al. Chem. Commun. 2013 , 49 , 2703 ) leads to the formation of [Ti2F9]- (Rb) and [Ti6F27]3- (K, Rb) salts. The former displays the same ([Ti2F9]-)∞ double chain as in Na[Ti2F9]·HF, while the anionic part in the latter, ([Ti6F27]3-)∞, represents the first example of a three-dimensional network built of TiF6 octahedra. The ([Ti6F27]3-)∞ anion was also found in [H3O]3[Ti6F27]. The crystal structure determination of Cs3[Ti4F19] revealed a new type of polymeric fluoridotitanate(IV) anion, ([Ti4F19]3-)∞. Similar to the ([Ti2F9]-)∞ anion, it is also built of zigzag double chains comprising TiF6 units. However, in the former there are fewer connections between TiF6 units of two neighboring chains than in the latter.

Canted Antiferromagnetism in Two-Dimensional Silver(II) Bis[pentafluoridooxidotungstate(VI)].

By slow reaction between colorless AgIW2O2F9 and elemental F2 in liquid anhydrous HF, violet platelike single crystals of Ag(WOF5)2 were grown. The crystal structure of Ag(WOF5)2 consists of layers built from Ag2+ cations bridged by [WOF5]- anions and not, as previously assumed, from infinite [AgII-F]+∞ chains and [W2O2F9]- anions. A majority (97%) of the disordered AgII cations are found with square-planar coordination of F/O ligands within the same layer, and they form additional long contacts with O/F atoms originating from the neighboring layers. The remaining 3% the of Ag(II) ions are coordinated only by F atoms in a square-planar fashion. The magnetic moments of Ag2+ from the same layer are almost perfectly antiferromagnetically aligned. Weak ferromagnetic interlayer interactions cause a small tilt (∼1.5°) of the magnetic moments, resulting in canted antiferromagnetism. Because of the lowering of the symmetry of [WOF5]- in the solid state, the vibrational spectra show more bands than expected for regular C4v symmetry. The electronic spectrum of Ag(WOF5)2 is reported and analyzed.

Crystal structures and Raman spectra of imidazolium poly[perfluorotitanate(IV)] salts containing the [TiF6]2-, ([Ti2F9]-)∞, and [Ti2F11]3- and the new [Ti4F20]4- and [Ti5F23]3- anions.

Reactions between imidazole (Im, C3H4N2) and TiF4 in anhydrous hydrogen fluoride (aHF) in different molar ratios have yielded [ImH]2[TiF6]·2HF, [ImH]3[Ti2F11], [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] upon crystallization. All five structures were characterized by low-temperature single-crystal X-ray diffraction. The single-crystal Raman spectra of [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] were also recorded and assigned. In the crystal structure of [ImH]2[TiF6]·2HF, two HF molecules are coordinated to each [TiF6](2-) anion by means of strong F-H···F hydrogen bonds. The [Ti2F11](3-) anion of [ImH]3[Ti2F11] results from association of two TiF6 octahedra through a common fluorine vertex. Three crystallographically independent [Ti2F11](3-) anions, which have distinct geometries and orientations, are hydrogen-bonded to the [ImH](+) cations. The [ImH]4[Ti4F20] salt crystallized in two crystal modifications at low (α-phase, 200 K) and ambient (ß-phase, 298 K) temperatures. The tetrameric [Ti4F20](4-) anion of [ImH]4[Ti4F20] consists of rings of four TiF6 octahedra, which each share two cis-fluorine vertices, whereas the pentameric [Ti5F23](3-) anion of [ImH]3[Ti5F23] results from association of five TiF6 units, where four of the TiF6 octahedra share two cis-vertices, forming a tetrameric ring as in [Ti4F20](4-), and the fifth TiF6 unit shares three fluorine vertices with three TiF6 units of the tetrameric ring. The [ImH][Ti2F9] salt also crystallizes in two crystal modifications at low (α-phase, 200 K) and high (ß-phase, 298 K) temperatures and contains polymeric ([Ti2F9](-))∞ anions, which appear as two parallel infinite zigzag chains comprised of TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the second chain through a shared fluorine vertex. Quantum-chemical calculations at the B3LYP/SDDALL level of theory were used to arrive at the gas-phase geometries and vibrational frequencies of the [Ti4F20](4-) and [Ti5F23](3-) anions, which aided in the assignment of the experimental vibrational frequencies of the anion series.

The first example of a mixed valence ternary compound of silver with random distribution of Ag(I) and Ag(II) cations.

The reaction between colourless AgSbF6 and sky-blue Ag(SbF6)2 (molar ratio 2 : 1) in gaseous HF at 323 K yields green Ag3(SbF6)4, a new mixed-valence ternary fluoride of silver. Unlike in all other Ag(I)/Ag(II) systems known to date, the Ag(+) and Ag(2+) cations are randomly distributed on a single 12b Wyckoff position at the 4̄ axis of the I4̄3d cell. Each silver forms four short (4 × 2.316(7) Å) and four long (4 × 2.764(6) Å) contacts with the neighbouring fluorine atoms. The valence bond sum analysis suggests that such coordination would correspond to a severely overbonded Ag(I) and strongly underbonded Ag(II). Thorough inspection of thermal ellipsoids of the fluorine atoms closest to Ag centres reveals their unusual shape, indicating that silver atoms must in fact have different local coordination spheres; this is not immediately apparent from the crystal structure due to static disorder of fluorine atoms. The Ag K-edge XANES analysis confirmed that the average oxidation state of silver is indeed close to +1⅓. The optical absorption spectra lack features typical of a metal thus pointing out to the semiconducting nature of Ag3(SbF6)4. Ag3(SbF6)4 is magnetically diluted and paramagnetic (µ(eff) = 1.9 µ(B)) down to 20 K with a very weak temperature independent paramagnetism. Below 20 K weak antiferromagnetism is observed (Θ = -4.1 K). Replacement of Ag(I) with potassium gives K(I)2Ag(II)(SbF6)4 which is isostructural to Ag(I)2Ag(II)(SbF6)4. Ag3(SbF6)4 is a genuine mixed-valence Ag(I)/Ag(II) compound, i.e. Robin and Day Class I system (localized valences), despite Ag(I) and Ag(II) adopting the same crystallographic position.

The cubic [Ti8F36]4- anion found in the crystal structures of K4Ti8F36·8HF and Rb4Ti8F36·6HF.

X-ray diffraction study of K4Ti8F36·8HF and Rb4Ti8F36·6HF reveals a novel type of octameric cubic [M8F36](4-) anion built from eight M(IV)F6 octahedra.