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The switching properties of a cyanido-bridged Fe/Co square molecule were investigated by single-crystal X-ray diffraction and X-ray absorption spectroscopy at both Fe and Co K-edges. Combining these two techniques, a complete picture of the thermal-, light- and X-ray-induced metal-to-metal electron transfer is obtained, illustrating the concerted role played by the Fe and Co sites. [ABSTRACT FROM AUTHOR]

The two-step spin crossover in mononuclear iron(III) complex [Fe(salpm)2]ClO4 ⋅0.5 EtOH ( 1) is shown to be accompanied by a structural phase transition as concluded from 57Fe Mössbauer spectroscopy and single crystal X-ray diffraction, with spin-state ordering on just one of two sub-lattices in the intermediate magnetic and structural phase. The complex also exhibits thermal- and light-induced spin-state trapping (TIESST and LIESST), and relaxation from the LIESST and TIESST excited states occurs via the broken symmetry intermediate phase. Two relaxation events are evident in both experiments, that is, two T(LIESST) and two T(TIESST) values are recorded. The change in symmetry which accompanies the TIESST effect was followed in real time using single crystal diffraction. After flash freezing at 15 K the crystal was warmed to 40 K at which temperature superstructure reflections were observed to appear and disappear within a 10 000 s time range. In the frame of the international year of crystallography, these results illustrate how X-ray diffraction makes it possible to understand complex ordering phenomena. [ABSTRACT FROM AUTHOR]

The [(TPA)FeIII(TCC)]+ complex [TPA = tris(2-pyridylmethyl)amine, TCC2- = 3,4,5,6-tetrachlorocatecholate dianion] forms a molecular solid with the SbF6- anion, which exhibits an incomplete S = 1/2 ↔ S = 5/2 thermal spin-crossover process centered at 250 K. Single-crystal X-ray diffraction, Raman spectroscopy, and magnetic measurements of this orthorhombic polymorph were performed to delineate the spin-state thermo- and piezoswitching in relation to the structural and elastic properties. Indeed, a pressure-induced spin crossover (centered at P1/2 ≈ 1.65 kbar, T = 294 K) concomitant with unit-cell contraction was observed by applying a hydrostatic pressure to the single crystal. Under ambient conditions, the piezo-induced transition, like that induced thermally, is relatively gradual, which probably reflects a similar mechanism in response to both stimuli. Except for a 47 K shift, the spin-crossover curves of the isostructural SbF6- and PF6- salts compare well. They are discussed with respect to structural anisotropy and pressure effects. [ABSTRACT FROM AUTHOR]

The title compound ( 3), CHBrNOS, is a Schiff base compound of 5-bromosalicylaldehyde ( 1) and sulfamethoxazole ( 2). The structure of ( 3) was determined by spectral (IR, H and C NMR), elemental analyses and X-ray diffraction data. Compound ( 3) crystallizes in the monoclinic space group C2/c, with a = 31.936(3), b = 6.2571(5), c = 16.903(1) Å, β = 94.867(8), V = 3365.5(5) Å, Z = 8. In the molecule of compound ( 3), the molecule is bent at the S atom with a C-SO-NH-C torsion angle of −86.3(3)°. Pairs of molecules, related by inversion centres, form intermolecular N-H···N hydrogen bonds to produce a dimer. An intramolecular phenolic O-H···N hydrogen bond is also formed. Intermolecular hydrogen bonding and π-π stacking hold the molecules together. The average distance between stacked benzene ring planes is 3.625(2) Å. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Nalidixic acid–DACH conjugate Cu(II) molecular entity, 1 was synthesized, thoroughly characterized by spectroscopic techniques (FT–IR, EPR and ESI–MS) and single crystal X-ray diffraction technique as a potential chemotherapeutic drug candidate for cancer oncology. Complex 1 was found to be a potent drug-like molecular entity in confirmation with Lipinski rules. 1R,2R-diaminocyclohexane (DACH) ligand scaffold (which reduces the drawbacks of cisplatin analogues) and nalidixic acid pharmacophore make it a suitable drug entity targeting nucleic acids. To evaluate the chemotherapeutic potential of 1 comparative in vitro DNA/RNA interaction studies have been investigated by employing various biophysical techniques (UV–vis, fluorescence, circular dichorism, viscosity, cyclic voltammetry and FT–IR), cleavage activity and Topo-II inhibition assay. Further, mechanistic investigation revealed the efficiency of 1 to cleave pBR322 DNA strands by an oxidative pathway involving the generation of ROS and preferential selectivity towards the A–T region of DNA major groove. Antiproliferative activity in conjugation with flow cytometry analysis of 1 against human osteoblastoma cell line (U2OS) suggested a cell cycle arrest at S phase. This work further advances our knowledge for the development and design of small RNA targeted therapeutic molecules which are under exploited drug targets. [Copyright &y& Elsevier]

The sensitivity of electronic propertiesof organic conductorsto minute modifications of their solid-state structure is investigatedhere within BEDT-TTF (ET) salts with organic bis-sulfonate anions,where specific hydrogen bonds between water molecules and sulfonatemoieties are shown to dynamically control the organic slabs’electronic structure. While the mixed-valence, 2,6-naphthalene-bis(sulfonate)salt, (ET)4(NBS)·4H2O, exhibitsa charge order state already at room temperature, the correspondingsalt with the 2,6-anthracene-bis(sulfonate) dianion, formulated as(ET)4(ABS)·4H2O, is metallicat RT and exhibits a metal–insulator transition at TMI= 85 K. The origin of the MI transition isrevealed from a combination of temperature-dependent spectroscopic(Raman) measurements, X-ray structure elucidations (from 300 to 15K), and theoretical investigations, demonstrating that the chargedisproportionation observed below TMIisassociated here with the progressive switching of bifurcated OH···Ohydrogen bonds between the sulfonate moieties of the anion and thetrapped water molecules. These movements within the anion layer aretransmitted through weaker C–H···O interactionsto the two A and B donor molecules, modifying the details of the overlapinteractions within AA and BB pairs and opening a gap in the bandstructure. [ABSTRACT FROM AUTHOR]

Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula [(η5-C5H5)Fe(μ,η6:η¹-p-RC5H4NN)Mo(η²-S2CNEt2)3] +PF6- (R: H, 5+PF6-; Me, 6+PF6-; MeO, 7+PF6-) and [(η5-C5-Me5)Fe(μ,η6:η¹-C6H5NN)Mo(η²-S2CNEt2)3]+PF6-, 8+PF6-, have been synthesized by reaction of the corresponding mixed-sandwich organometallic hydrazines [(η5-C5H5)Fe(η6-p-RC6H4NHNH2)]+PF6- (R: H, 1+PF6-; Me, 2+PF6-; MeO, 3+PF6-) and [(η5-C5Me5)Fe(η6-C6H5NHNH2)]+PF6-, 4+PF6-, with cis-dioxomolybdenum(VI) bis(diethyldithiocarbamato) complex, [MoO2(S2CNEt2)2], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC(=S)-NEt2•3H2O, in refluxing methanol. These iron-molybdenum complexes consist of organometallic and inorganic. fragments linked each other through a π-conjugated aryldiazenido bridge coordinated in η6 and η¹ modes, respectively. These complexes were fully characterized by FT-IR, UV-visible, and ¹H NMR spectroscopies and, in the case of complex 7+PF6-, by single-crystal X-ray diffraction analysis. Likewise, the electrochemical and solvatochromic properties were studied by cyclic voltammetry and UV-visible spectroscopy, respectively. The electronic spectra of these hybrids show an absorption band in the 462-489 and 447-470 nm regions in CH2CI2 and DMSO, respectively, indicating the existence of a charge-transfer transition from the inorganic donor to the organometallic acceptor fragments through the aryldiazenido spacer. A rationalization of the properties of 5+PF6--8+PF6- is provided through DFT calculations on a simplified model of 7+PF6-. Besides the heterodinuclear complexes 5+PF6--8+PF6-, the mononuclear molybdenum diazenido derivatives, [(ρ¹-p-RC6H4NN)Mo(η²-S2CNEt2)3] (R: H, 9; Me, 11); MeO, 11), resulting from the decoordination of the [(η5-C5H5)Fe]+ moiety of complexes 5+PF6--7+PF6-, were also isolated. For comparative studies, the crystalline and molecular structure of complex 10·Et2O was also determined by X-ray diffraction analysis and its electronic structure computed. [ABSTRACT FROM AUTHOR]