The Antibacterial Properties of Nanocomposites Based on Carbon Nanotubes and Metal Oxides Functionalized with Azithromycin and Ciprofloxacin.

Different microorganisms are present in nature, some of which are assumed to be hazardous to the human body. It is crucial to control their continuing growth to improve human life. Nanomaterial surface functionalization represents a current topic in continuous evolution that supports the development of new materials with multiple applications in biology, medicine, and the environment. This study focused on the antibacterial activity of different nanocomposites based on functionalized multi-walled carbon nanotubes against four common bacterial strains. Two metal oxides (CuO and NiO) and two antibiotics (azithromycin and ciprofloxacin) were selected for the present study to obtain the following nanocomposites: MWCNT-COOH/Antibiotic, MWCNT-COOH/Fe3O4/Antibiotic, and MWCNT-COOH/Fe3O4/MO/Antibiotic. The present study included two Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Ciprofloxacin (Cip) functionalized materials (MWCNT-COOH/Fe3O4/Cip) were most efficient against all tested bacterial strains; therefore, we conclude that Cu and Ni reduce the effects of Cip. The obtained results indicate that the nanocomposites functionalized with Cip are more effective against selected bacteria strains compared to azithromycin (Azi) functionalized nanocomposites. The current work determined the antibacterial activities of different nanocomposites and gave fresh insights into their manufacture for future research regarding environmental depollution.

Organopnictogen(III) bis(arylthiolates) containing NCN-aryl pincer ligands: from synthesis and characterization to reactivity.

Salt elimination reactions between organopnictogen(III) dichlorides, RPnCl2 [R1 = 2,6-(Me2NCH2)2C6H3, Pn = Sb (1), Bi (2); R2 = 2,6-{MeN(CH2CH2)2NCH2}2C6H3, Pn = Sb (3), Bi (4); R3 = 2,6-{O(CH2CH2)2NCH2}2C6H3, Pn = Sb (5), Bi (6)] and 2 equivalents of KSC6H3Me2-2,6 afforded the isolation of a series of new NCN-chelated monoorganopnictogen(III) bis(arylthiolates), RPn(SC6H3Me2-2,6)2 [R1, Pn = Sb (7), Bi (8); R2, Pn = Sb (9), Bi (10); R3, Pn = Sb (11), Bi (12)]. Compounds 7 and 8 are unstable upon exposure to a dry O2 atmosphere and their aerobic decomposition yields the monoorganopnictogen(III) oxides, cyclo-[2,6-(Me2NCH2)2C6H3Pn(µ-O)]2 [Pn = Sb (13), Bi (14)] with concomitant formation of the corresponding disulfide, ArS-SAr (Ar = C6H3Me2-2,6). The oxidative addition of elemental sulfur or selenium to 7 undergoes a similar reaction path and gives stable heterocyclic species cyclo-[2,6-(Me2NCH2)2C6H3Sb(µ-E)]2 [E = S (15), Se (16)]. The reaction of 12 with I2 (1 : 1 molar ratio) gives the diiodide [2,6-{O(CH2CH2)2NCH2}2C6H3]BiI2 (17), along with the S-S oxidative coupling by-product, ArS-SAr. The use of an excess of iodine affords the crystallization of a 2 : 1 iodine adduct of 17 (17·0.5I2), built through halogen bonding. All new compounds were characterized by multinuclear NMR spectroscopy and ESI-MS as well as single crystal X-ray diffraction (except compounds 9 and 10).

Synthesis, Structure and Supramolecular Properties of a Novel C3 Cryptand with Pyridine Units in the Bridges.

The high-yield synthesis and the structural investigation of a new cryptand with C3 symmetry, exhibiting 2,4,6-triphenyl-1,3,5-triazine central units and pyridine-based bridges, are reported. The structure of the compound was investigated by single crystal X-ray diffractometry, NMR (nuclear magnetic resonance), HRMS (high resolution mass spectrometry) measurements, and theoretical calculations. The study of supramolecular behavior in solid state revealed the association of cryptand molecules by C-H---π and π---π contacts. Moreover, theoretical calculations indicated the high binding affinity of the cryptand for various organic molecules as guests.

Indenopyrans - synthesis and photoluminescence properties.

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

Mixed triorganobismuthines RAr2Bi [Ar = C6F5, 2,4,6-(C6F5)3C6H2] and hypervalent racemic Bi-chiral diorganobismuth(iii) bromides RArBiBr (Ar = C6F5, Mes, Ph) with the ligand R = 2-(Me2NCH2)C6H4. Influences of the organic substituent.

Triorganobismuthines R(C6F5)2Bi (1) and R[2,4,6-(C6F5)3C6H2]2Bi (2) [R = 2-(Me2NCH2)C6H4] were synthesized by reaction of RBiBr2 with C6F5MgBr and 2,4,6-(C6F5)3C6H2Li, respectively, in a 1 : 2 molar ratio. The Bi-chiral bromides R(C6F5)BiBr (3), R(Mes)BiBr (4), and R(Ph)BiBr (5) were obtained from RBiBr2 and C6F5MgBr, MesMgBr or PhMgBr, or from PhBiBr2 and RLi, in a 1 : 1 molar ratio. The molecular structures of 1-5 were determined by single-crystal X-ray diffraction and are discussed taking into account the chirality of the species. Supramolecular aspects in the solid state are presented. The solution behaviour of the title compounds, including dynamic aspects, are discussed on the basis of multinuclear ((1)H, (13)C, (19)F) NMR spectroscopy.

Cryptands with 1,3,5-tris(1',3'-dioxan-2'-yl)-benzene units: synthesis and structural investigations.

Various cryptands based on 1,3-dioxane decorated 1,3,5-trisubstituted-benzene building blocks, connected by different chains (exhibiting ester, ether, or triazol groups) to several units with C3 symmetry, are reported. The structure of the compounds was investigated by single crystal X-ray diffraction, NMR, and MS. The role of the 1,3-dioxane units was targeted to ensure the preorganization of the substrate for the macrocyclization reactions on one side, and for easier NMR assignment of the structure of the cryptands on the other side.

Bis(8-methyl-2,8-dicarba-closo-dodeca-boran-2-yl) tris-elenide.

In the title compound, C(6)H(26)B(20)Se(3), the geometry around the central Se atom is V-shaped, with the Se-Se-Se angle being 105.60 (4)°. The Se-Se bond lengths are consistent with single covalent bonds.

µ-Carbonato-bis-(bis-{2-[(diethyl-amino)-meth-yl]phen-yl}bis-muth(III)).

The mol-ecular structure of the title compound, [Bi(2)(C(11)H(16)N)(4)(CO(3))], consists of a symmetrically bridging carbonato group which binds two [2-Et(2)NCH(2)C(6)H(4)](2)Bi units that are crystallographically related via a twofold rotation axis bis-ecting the carbonate group. The two Bi atoms and two of the C atoms directly bonded to bis-muth are quasi-planar [deviations of 0.323 (1) and 0.330 (9)Å for the Bi and C atoms, respectively] with the carbonate group. The remaining two ligands are in a trans arrangement relative to the quasi-planar (CBi)(2)CO(3) system. The metal atom is strongly coordinated by the N atom of one pendant arm [Bi-N = 2.739 (6) Å], almost trans to the O atom, while the N atom of the other pendant arm exhibits a weaker intra-molecular inter-action [Bi⋯N = 3.659 (7) Å] almost trans to a C atom. If both these intra-molecular N→Bi inter-actions per metal atom are considered, the overall coordination geometry at bis-muth becomes distorted square-pyramidal [(C,N)(2)BiO cores] and the compound can be described as a hypervalent 12-Bi-5 species. Additional quite short intra-molecular Bi⋯O inter-actions are also present [3.796 (8)-4.020 (9) Å]. Inter-molecular associations through weak η(6)⋯Bi inter-actions [Bi⋯centroid of benzene ring = 3.659 (1) Å] lead to a ribbon-like supra-molecular association.

Organobismuth compounds with the pincer ligand 2,6-(Me2NCH2)2C6H3: monoorganobismuth(III) carbonate, sulfate, nitrate, and a diorganobismuthenium(III) salt.

The reaction of RBiCl(2) (1) [R = 2,6-(Me(2)NCH(2))(2)C(6)H(3)] with Na(2)CO(3) or Ag(2)SO(4) (1 : 1 molar ratio) gave RBiCO(3) (2) and RBiSO(4) (3), respectively. RBi(NO(3))(2) (4) was obtained from RBiCl(2) and AgNO(3) (1 : 2 molar ratio). The ionic complex [R(2)Bi][W(CO)(5)Cl] (6) was obtained from R(2)BiCl (5) and W(CO)(5)(THF), following an unusual chlorine transfer from bismuth to tungsten. Compounds 2-4 are partially soluble in water. The molecular structures of 2·0.5CH(2)Cl(2), 3, 4·H(2)O and 6 were established by single-crystal X-ray diffraction. The carbonate 2 and the sulfate 3 exhibit a polymeric structure based on bridging oxo anions, while for the compound 4 dimer associations are formed, with both bridging and terminal nitrate anions. Dimer associations, based on weak Cl···H interactions between the cation and the anion, were found in the crystal of 6.

Substitutional disorder in the ionic diorganoanti-mony halide adduct [bromido/chlorido(0.33/0.67)][2-(di-methyl-amino-meth-yl)phen-yl][2-(di-methyl-ammonio-meth-yl)phen-yl]anti-mony(III) 0.75-bromide 0.25-chloride.

The title complex, [SbBr(0.33)Cl(0.67)(C(9)H(13)N)(C(9)H(12)N)]Br(0.75)Cl(0.25), exhibits substitutional disorder of both halogen atoms in the asymmetric unit, however, with different occupancies. Thus, the halogen atom bonded to Sb has 0.67 (4) occupancy for Cl and 0.33 (4) for Br, while the anionic halogen atom shows 0.75 (4) occupancy for Br and 0.25 (4) for Cl. An N-H⋯Cl/Br hydrogen bond is established between the cation and the halide anion. The coordination geometry of the Sb center in the cation is distorted pseudo-trigonal-bipyramidal as a result of the strong intra-molecular N→Sb coordination trans to the Sb-Cl/Br bond. The pendant arm on the second ligand is twisted away from the metal center. The compound crystallizes as a racemate, i.e. a mixture of (R(N2),C(Sb1)) and (S(N2),A(Sb1)) isomers with respect to planar chirality induced by the coordinating N atom and chelate-induced Sb chirality. These isomers are associated through C(phen-yl)-H⋯Cl/Br hydrogen bonds, forming a three-dimensional architecture.

Monoorganobismuth(III) dihalides containing the new pincer 2,6-{MeN(CH2CH2)2NCH2}2C6H3 ligand: solution NMR, vibrational and single-crystal X-ray studies.

The reaction of RLi [R = 2,6-{MeN(CH2CH2)2NCH2}2C6H3 ] with BiCl3 (1:1 molar ratio) afforded RBiCl2 (2). RBiBr2 (3) and RBiI2 (4) were obtained by halogen-exchange reactions from 2 . The organobismuth(III) dihalides containing the new steric demanding (N,C,N)-pincer ligand were characterized both in solution and solid state. The molecular structures of compounds were established by single-crystal X-ray diffraction. They all show a T-shaped CBiX(2) core, stabilized by two strong intramolecular N-->Bi interactions in trans positions to each other. The overall (N,C,N)BiX2 core exhibits a distorted square-pyramidal coordination geometry. The NMR studies provided evidences for the presence of internal nitrogen-bismuth coordination in solution too. DFT calculations were performed on the related species [2,6-(R(2)NCH(2))(2)C(6)H(3)]BiX(2) (R = H, Me; X = Cl, Br, I) in order to elucidate the bond nature and vibrational spectroscopic features of these compounds.

Hypervalent organobismuth(iii) carbonate, chalcogenides and halides with the pendant arm ligands 2-(Me2NCH2)C6H4 and 2,6-(Me2NCH2)2C6H3.

R2BiOH (1) [R = 2-(Me2NCH2)C6H4] and (R2Bi)2O (2) are formed by hydrolysis of R2BiCl with KOH. Single crystals of were obtained by air oxidation of (R2Bi)2. The reaction of R2BiCl and Na2CO3 leads to (R2Bi)2CO3 (3). 3 is also formed by the absorption of CO2 from the air in solutions of 1 or 2 in diethyl ether or toluene. (R2Bi)2S (4) is obtained from R2BiCl and Na2S or from (R2Bi)2 and S8. Exchange reactions between R2BiCl and KBr or NaI give R2BiX [X = Br (5), I (6)]. The reaction of RBiCl2 (7) with Na2S and [W(CO)5(THF)] gives cyclo-(RBiS)2[W(CO)5]2 (8). cyclo-(R'BiS)2 (9) [R' = 2,6-(Me2NCH2)2C6H3] is formed by reaction of R'BiCl2 and Na2S. The structures of were determined by single-crystal X-ray diffraction.

Isomers of a dibismuthane, R2Bi-BiR2 [R = 2,6-(Me2NCH2)2C6H3], and unusual reactions with oxygen: formation of [R2Bi]2(O2) and R'R' 'Bi [R' = 2-(Me2NCH2)-6-{Me2N(O)CH2}C6H3; R' ' = 2-(Me2NCH2)-6-{O(O)C}C6H3].

R2Bi-BiR2 [1; R = 2,6-(Me2NCH2)2C6H3], a dibismuthane that exists in different forms in the crystalline state, reacts in air with the formation of the peroxide [R(2)Bi]2(O2) (2) and partial oxidation of the pendant (dimethylamino)methyl groups, yielding the mononuclear bismuth complex R'R' 'Bi (3) [R' = 2-(Me2NCH2)-6-{Me2N(O)CH2}C6H3; R' ' = 2-(Me2NCH2)-6-{O(O)C}C6H3].