CH3CN Complex Research Articles

The ALMA-QUARKS Survey. I. Survey Description and Data Reduction

This paper presents an overview of the QUARKS survey, which stands for “Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures.” The QUARKS survey is observing 139 massive clumps covered by 156 pointings at Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 (λ ∼ 1.3 mm). In conjunction with data obtained from the ALMA-ATOMS survey at Band 3 (λ ∼ 3 mm), QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au. This overview paper describes the observations and data reduction of the QUARKS survey, and gives a first look at an exemplar source, the mini-starburst Sgr B2(M). The wide-bandwidth (7.5 GHz) and high-angular-resolution (∼0.″3) observations of the QUARKS survey allow for the resolution of much more compact cores than those could be done by the ATOMS survey, and to detect previously unrevealed fainter filamentary structures. The spectral windows cover transitions of species including CO, SO, N2D+, SiO, H30 α, H2CO, CH3CN, and many other complex organic molecules, tracing gas components with different temperatures and spatial extents. QUARKS aims to deepen our understanding of several scientific topics of massive star formation, such as the mass transport within protoclusters by (hub-)filamentary structures, the existence of massive starless cores, the physical and chemical properties of dense cores within protoclusters, and the feedback from already formed high-mass young protostars.

In situ synthesis, crystal structure, selective anticancer and proapoptotic activity of complexes isolated from the system containing zerovalent nickel and pyrazole derivatives

New nickel(II) complexes [NiLS(NCS)2]∙CH3CN (1) [Ni(dmpz)2(NCS)2]n (2), where LS is N,N,N-tris(1-(3,5-dimethylpyrazolylmethyl)amine) and dmpz is 3,5-dimethylpyrazole, have been isolated in a one-pot synthesis by reacting zerovalent-powered nickel, 1-hydroxymethyl-3,5-dimethylpyrazole (HL1) and 1-carboxamide-3,5-dimethylpyrazole (HL2) as precursors. The complexes were characterized by elemental analysis, IR and UV–Vis spectra, thermal investigations and single crystal diffraction studies. The anti-proliferative activity of the described Ni(II) complexes was studied in vitro against selected human tumour cell lines and normal human cells (fibroblasts). The monomeric complex [NiLS(NCS)2]∙CH3CN (1) expressed more potent anti-proliferative activity towards cancer cells with the relevant cytotoxicity, while the polymeric complex [Ni(dmpz)2(NCS)2]n (2) was very toxic towards normal cells and was also characterized by mild inhibitory potency against tumour cells and poor selectivity. Complex (1) causes massive death of cancer cells due to programmed cell death, apoptosis. The obtained results demonstrated potent cytotoxic activity of the isolated [NiLS(NCS)2]∙CH3CN complex combined with strong selectivity towards cancer cells, and the mechanism of its actions included apoptosis.

Self-assembly patterns of non-metalloid silver thiolates: structural, HR-ESI-MS and stability studies.

Screening of AgNO3/AgStBu solutions in DMF, DMSO and NMP resulted in the isolation of three novel nanosized silver/thiolate complexes with a torus-like {Ag20(StBu)10} core. The structures of [NO3@Ag20(StBu)10(NO3)9(DMF)6] (1) and [NO3@Ag20(tBuS)10(NO3)8(NMP)8][NO3@Ag19(tBuS)10(NO3)8(NMP)6]2(NO3) (2) were studied by single crystal X-ray diffraction (SCXRD). The self-assembly process leading to 1 can be switched to a different outcome using Br-, resulting in [Br@Ag16(StBu)8(NO3)5(DMF)3](NO3)2 (3), which is the one of the few genuine host-guest complexes in the silver/thiolate systems. Solutions of the individual complexes in CH3CN were studied by HR-ESI-MS techniques, which revealed a dynamic behavior for each complex, driven by a redistribution of the {AgNO3} units. This dynamics results in the appearance of both cationic and anionic species, based on unchanged silver-thiolate cores. Daylight causes degradation of 3 with the formation of a composite material based on defective orthorhombic Ag2S with a porous morphology, as observed using the SEM technique. The electrocatalytic HER activity of such a material was studied.

A new photoactivable NO-releasing {Ru-NO}6 ruthenium nitrosyl complex with a tetradentate ligand containing aniline and pyridine moieties.

A new type of photoactivable NO-releasing ruthenium nitrosyl complex, [Ru(EPBP)Cl(NO)], with a tetradentate ligand, N,N'-(ethane-1,2-diyldi-o-phenylene)-bis(pyridine-2-carboxamide) (= H2 EPBP) was synthesized. Single crystal X-ray crystallography revealed that the complex has a distorted octahedral coordination geometry and NO is positioned at cis to Cl- ion. NO-photolysis was observed under a white room light. The photodissociation of Ru-NO bond was identified by various techniques including X-ray crystallography, IR, UV/Vis absorption, electron paramagnetic resonance (EPR), and NMR spectroscopies. Quantum yields for the NO-photolysis of the complex in CH3 OH, CHCl3 , DMSO, CH3 CN, and CH3 NO2 were measured to be 0.19-0.36 with 400 (±5) nm excitation. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were performed to understand the details of the photodissociation of the complex. The calculations suggest that the NO photolysis is most likely initiated by the electronic transition from the aniline moiety π MOs (π (aniline)) of the EPBP2- chelating ligand to the π-antibonding MO of Ru-NO (π*(Ru-NO)). Experimental and theoretical investigations indicate that the EPBP2- ligand provides an effective platform forming ruthenium nitrosyl complexes useful for NO-photoreleasing.

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Synthesis, characterization, DNA binding ability, in vitro cytotoxicity, electrochemical properties and theoretical studies of copper(II) carboxylate complexes

Four copper(II) carboxylate complexes, namely [Cu2(μ-3,5-dinitrobenzoate-O,O')4(4-(dimethylamino)benzaldehyde)2] (1), [Cu2(μ-benzoate-O,O')4(benzoic acid)2] (2), [Cu2(μ-benzoate-O,O')4(H2O)2] [Cu(benzoate-O,O')2(imz)2].2H2O (3) and [Cu(benzoate-O,O')2(2-Me-imz)2] (4) (imz = imidazole, 2-Me-imz = 2-methyl-imidazole), were synthesized and comprehensively characterized by elemental analysis, spectroscopic methods, single crystal X-ray diffraction, cyclic voltammetry (CV), topological analysis as well as theoretical studies. Single crystal X-ray diffraction revealed that products 1 and 2 are dinuclear paddle-wheel complexes, compound 3 is a co-crystal containing mononuclear and dinuclear blocks, while compound 4 is a mononuclear complex. Hirshfeld surface analysis of the compounds rationalized different types of hydrogen bonds, which also lead to the generation of H-bonded networks in 3 and 4. Their topological analysis disclosed a uninodal 4-connected 2D layer with sql topology in 3 and a uninodal 2-connected 1D chain with 2C1 topology in 4. The interaction of 1–4 with calf thymus DNA was investigated by UV–visible and fluorescence spectroscopy, revealing a moderately strong non-intercalative mode of interaction. In vitro cytotoxicity study of the complexes on HepG2 (human liver hepatocellular carcinoma) cell lines revealed a significant inhibition activity. Electrochemical study of the complexes in CH3CN (1–3) and DMSO (4) solution showed a one electron transfer corresponding to Cu(III)Cu(II)/Cu(II)Cu(II) and Cu(II)Cu(II)/Cu(I)Cu(II) redox couples. The ΔE and Ipa/Ipc values suggest that the redox couples are quasireversible. The DFT study was performed to further rationalize the crystal structures and nuclearity of the obtained copper(II) complexes.

A comparison of ether- and alkyl-imidazolium-based ionic liquids diluted with CH3CN: A combined FTIR and DFT study

Ether-based functionalized ionic liquids (ILs) show great potential in electrochemical devices and energy applications, but their microscopic behaviour is seldom investigated. In this work, the microscopic structures of two imidazolium-based ILs (1-methoxyethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EOMIMFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI)) and their hydrogen bonding interactions with acetonitrile (CH3CN) at various concentrations are investigated by using attenuated total reflection infrared spectroscopy (ATR-FTIR), excess infrared spectroscopy and quantum chemical calculations. Additionally, the effects of introducing a functional group, i.e., an ether group, on the properties of the IL are explored. The main conclusions are as follows: (1) [EOMIM]+ can form an intra-molecular hydrogen bond with C2H or C5H, and the former is more stable. (2) The introduction of an ether group to the cation weakens the hydrogen bonding interactions between the cation and anion/CH3CN. (3) The introduction of an ether group to the cation changes the interaction sites between the ILs and CH3CN. In the EMIMFSI–CH3CN system, C2H is the main interaction site. In the EOMIMFSI–CH3CN system, the interaction site with CH3CN changes from C2H in the [EOMIM]+–CH3CN complex to C4H in the ion pair–CH3CN/ion cluster–CH3CN complex. (4) Some complexes such as ion clusters, small ion clusters and ion pairs in the two systems are identified by excess infrared spectroscopy and quantum chemical calculations.

Luminescence from a highly asymmetric nine-coordinate tricapped trigonal prismatic Sm(III) complex

The nine-coordinate complexes of tris(dibenzoylmetanato)La(III) and Sm(III) with tptz were synthesized and thoroughly characterized. The 1H NMR spectrum of [La(dbm)3(tptz)]∙CH3CN is consistent with the coordination of three dbm and one tptz. The tricapped trigonal prism geometry of [Sm(dbm)3(tptz)]∙CH3CN complex is revealed by single crystal X-ray diffraction analysis. The shape 2.1v analysis authenticates the tricapped trigonal prism geometry of [Sm(dbm)3(tptz)]∙CH3CN complex. The Sm(III) is coordinatively saturated by the coordination of six oxygen atoms from dbm units and two pyridyl and one triazine nitrogen atoms from tptz moiety. The steady-state and time resolved photoluminescence of the solid [Sm(dbm)3(tptz)]∙CH3CN and its PMMA hybrid films of different concentration are investigated and discussed. The complex has only one emitting center since the decay times are fitted by mono-exponential function. The higher PL intensity of 4G5/2 → 6H7/2 (ΔJ = 1, magnetic-dipole transition) transition compared to 4G5/2 → 6H9/2 (ΔJ = 2, electric-dipole transition), in the case of 3% (w/w) PMMA hybrid film is the result of strong vibrionic coupling. Although the PL intensity of two transition are different even then the decay times of the transition are roughly similar in magnitude. The stark splitting of electric-dipole 4G5/2 → 6H9/2 transition in the spectrum of 3% film is interesting and leads to believe a strong coupling between states of f-electrons and electric fields of the surrounding ligands.

Synthesis and crystal structure of manganese(III), zinc(II) and cadmium(II) complexes based on a symmetrical macroacyclic Schiff base ligand containing piperazine moiety, DNA binding studies of complexes

Three macroacyclic Schiff base complexes have been obtained by the reaction of a previously known Schiff base ligand, 2-((Z)-(2-((4-((Z)-2-((Z)-2-hydroxy-3-methoxybenzylideneamino)benzyl)piperazin-1-yl)methyl)phenylimino)methyl)-6-methoxyphenol (H2L), and Mn(II), Zn(II) and Cd(II) ions in mixture of ethanol and methanol solvents. The resultant complexes were characterized by physical and spectroscopic methods. Molar conductivity (ɅM) data were measured at 25 °C using 10−3 M solutions of the complexes in acetonitrile solvent. In addition, the structure of the [MnL]ClO4·CH3CN complex has been revealed by a single-crystal X-ray structural analysis. In this complex, the Mn(II) has been oxidized to Mn(III), with the manganese ion being in a slightly distorted trans-O2N4 octahedral coordination environment arising from all six donor atoms of the doubly deprotonated ligand. The interaction of the ligand and the corresponding Mn(III), Zn(II) and Cd(II) complexes with calf thymus DNA (ct-DNA) has been appraised by dynamic viscosity, emission titration and competitive fluorescence methods which revealed that the compounds interact with ct-DNA via an intercalation mechanism.

All]-S,S-dioxide Oligo-Thienylenevinylenes: Synthesis and Structural/Electronic Shapes from Their Molecular Force Fields.

Oligo-S,S-dioxothienylenevinylenes have been prepared by transferring oxygen atoms to the sulfur atoms using the HOF⋅CH3 CN complex. Their photophysical properties are presented in comparison with their thiophenevinylene congeners. Together with their vibrational properties and molecular force fields, this study allows for the interpretation of the alteration of aromaticity and inter-ring exocyclic π-conjugation in this series.

Iron(III)–salen ion catalyzed s-oxidation of l-cysteine and s-alkyl-l-cysteines by H2O2: Spectral, kinetic and electrochemical study

The H2O2 oxidation of l-cysteine and s-alkyl-l-cysteines (s-met-l-cys, s-et-l-cys & s-pro-l-cys) catalyzed by iron(III)–salen (salen = N,N′-bis(salicylidene)ethylenediaminato) complexes in aqueous CH3CN proceeds through Michaelis–Menten kinetics. The rate constant (k) values correlate well with Hammett σ constants, which gives the positive reaction constant (ρ = 1.5–1.9) value. The CV of oxoiron(IV)-salen ion shows a clear oxidation peak at 1.28 V in 0.1 M phosphate buffer (PB) solution using 0.1 M tertiary butyl ammonium perchlorate (TBAP) as supporting electrolyte at 266 K. The rate of the reaction is highly sensitive to the length of the alkyl chains present in the l-cysteines, pH and solvent composition of the medium. The calculated binding constant values (Kf) in the range of 117–613 M−1, indicate that iron(III)–salen complexes carrying electron donating substituents in the salen ligand have higher binding constant values compared to those carrying electron withdrawing substituents. Product analysis shows the conversion of l-cys to its disulfide and s-alkyl-l-cys to the corresponding sulfoxides. Based on the spectral and kinetic data the plausible mechanism has been proposed.

A comparison of the metal-ligand interactions of the pentafluorophenylethynyl and trifluoropropynyl ligands in transition metal cyclam complexes

The pentafluorophenylethynyl ligand, C2C6F5, is a commonly used electron withdrawing ligand. In the context of developing complexes with blue-shifted emission for organic light emitting diode applications, it is often necessary to have electron poor ligands that are also relatively high on the spectrochemical series. The trifluoropropynyl ligand, C2CF3, is also electron withdrawing and has never been directly compared to C2C6F5. Herein complexes of the type trans-[M(cyclam)(C2R)2]OTf, where M = CoIII and CrIII and C2R = C2C6F5, are prepared and characterized by X-ray crystallography, cyclic voltammetry, and UV-Vis, IR, and Raman spectroscopy. Emission spectroscopy for the CrIII complex is also reported. These C2C6F5 complexes are compared to the corresponding complexes where C2R = C2CF3, and C2C6H5. For trans-[Co(cyclam)(C2R)2]OTf, the reversible CoIII/II reduction for the C2C6F5 complex occurs 120 mV more cathodic than that for the C2CF3 complex, indicating that C2CF3 is more electron withdrawing, a conclusion that is supported by analysis of CC stretching frequencies. The lowest energy metal-centered (MC) 1A1g → 1T2g absorption band for the C2CF3 and C2C6F5 complexes in CH3CN appear at 425 and 438 nm, respectively, suggesting that C2CF3 is a stronger field ligand. In the region of the LMCT transitions, the absorption spectra for the trans-[Cr(cyclam)(C2R)2]OTf complexes, where C2R = C2C6H5 and C2C6F5, show significant vibronic structure that is also superimposed on the MC transitions, suggesting some degree of charge transfer character in the latter. The CrIII complexes are all emissive in room-temperature fluid solution with the C2CF3 complex showing significant fine structure and the C2C6H5 and C2C6F5 complex emission being broad, structureless, and redshifted by comparison. This suggests that emission in the C2CF3 complex is of 2Eg (Oh) origin and emission for the C2C6H5 and C2C6F5 complexes is of 2T1g (Oh) origin. Emission for all CrIII complexes in 77 K glass shows significant fine structure. The presence of a dominant 0-0′ emission band in the C2C6H5 and C2C6F5 complexes suggests a non-centrosymmetric ground state. This is supported by the crystal structure for trans-[Cr(cyclam)(C2C6F5)2]OTf that shows an angle of 77.8° between the planes defined by the aryl rings.

Electrochemical Generation and Spectroscopic Characterization of the Key Rhodium(III) Hydride Intermediates of Rhodium Poly(bipyridyl) H2-Evolving Catalysts.

We previously reported that the [RhIII(dmbpy)2Cl2]+ (dmbpy = 4,4'-dimethyl-2,2'-bipyridine) complex is an efficient H2-evolving catalyst in water when used in a molecular homogeneous photocatalytic system for hydrogen production with [RuII(bpy)3]2+ (bpy = 2,2'-bipyridine) as photosensitizer and ascorbic acid as sacrificial electron donor. The catalysis is believed to proceed via a two-electron reduction of the Rh(III) catalyst into the square-planar [RhI(dmbpy)2]+, which reacts with protons to form a Rh(III) hydride intermediate that can, in turn, release H2 following different pathways. To improve the current knowledge of these key intermediate species for H2 production, we performed herein a detailed electrochemical investigation of the [RhIII(dmbpy)2Cl2]+ and [RhIII(dtBubpy)2Cl2]+ (dtBubpy = 4,4'-di- tert-butyl-2,2'-bipyridine) complexes in CH3CN, which is a more appropriate medium than water to obtain reliable electrochemical data. The low-valent [RhI(Rbpy)2]+ and, more importantly, the hydride [RhIII(Rbpy)2(H)Cl]+ species (R = dm or dtBu) were successfully electrogenerated by bulk electrolysis and unambiguously spectroscopically characterized. The quantitative formation of the hydrides was achieved in the presence of weak proton sources (HCOOH or CF3CO3H), owing to the fast reaction of the electrogenerated [RhI(Rbpy)2]+ species with protons. Interestingly, the hydrides are more difficult to reduce than the initial Rh(III) bis-chloro complexes by ∼310-340 mV. Besides, 0.5 equiv of H2 is generated through their electrochemical reduction, showing that Rh(III) hydrides are the initial catalytic molecular species for hydrogen evolution. Density functional theory calculations were also performed for the dmbpy derivative. The optimized structures and the theoretical absorption spectra were calculated for the initial bis-chloro complex and for the various rhodium intermediates involved in the H2 evolution process.

Some new metal(II) complexes based on bis-Schiff base ligand derived from 2-acetylethiophine and 2,6-diaminopyridine: Syntheses, structural investigation, thermal, fluorescence and catalytic activity studies

A novel Schiff base ligand N, N′-bis (1-(thiophen-2-yl) ethylidene) pyridine-2, 6-diamine has been prepared by the condensation of 2,6-diaminopyridine and 2- acetylthiophene in ethanol in the molar ratio of 1:2. The Study by analytical and spectroscopic techniques indicated that the complexes have composition with the general formulae: [MLX2]· nH2O, where (M = Mn, Co, Ni, and Cu; X = Cl; n = 4, 6, 6, 2), respectively. All the metal (II) complexes have been characterized with elemental analysis, FT−IR, Mass, 1H NMR, UV–Vis, magnetic moment, thermal analysis (TG and DTG) techniques, molar conductance and fluorescence spectra. Non electrolyte of complexes using DMF as a solvent is due to their low molar conductance. From FTIR spectral data, the coordination between the central metal ion with azomethine nitrogen and sulfur of acetylthiophene ring are confirmed. An octahedral geometry of all metal(II) complexes is investigated from electronic and magnetic data. The kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern equation. The fluorescence properties of theses complexes in DMSO, DMF, and CH3CN were studied. The effect of pH influencing the fluorescence intensity is discussed. The catalytic activities of metal(II) complexes were studied using H2O2 solution.

Cyclometalated Ir(iii) complexes [Ir(tpy)(bbibH2)Cl][PF6] and [Ir(tpy)(bmbib)Cl][PF6]: intramolecular ππ interactions leading to facile synthesis and enhanced luminescence.

Cyclometalated Ir(iii) complexes [Ir(tpy)(bbibH2)Cl][PF6] (1·PF6) and [Ir(tpy)(bmbib)Cl][PF6] (2·PF6), and the control complex [Ir(tpy)(mbib)Cl][PF6] (3·PF6) were synthesized at 135 °C for 10 hours for the former two complexes, while at 190 °C for 24 hours for the latter complex, in which the cyclometalated ligands bbibH2-, bmbib- and mbib- incorporate one or two N-methylbenzoimidazole/benzimidazole units in order to explore the influence of the molecular structures of these complexes on their synthesis conditions and luminescence behaviors. The 1H NMR and crystal structure measurements indicate that both 1·PF6 and 2·PF6 contain intramolecular ππ stacking interactions between the non-coordinated N-methylbenzoimidazole/benzimidazole unit and the tpy ligand, but there are no such ππ interactions in 3·PF6. At room temperature, these complexes in CH3CN reveal an emission with a combination of 3MLCT and 3LC characteristics, occurring at 534 nm with a quantum yield Φ = 39.5% and a lifetime τ = 2.39 μs for 1·PF6, 536 nm with Φ = 66.4% and τ = 2.94 μs for 2·PF6, and 558 nm with Φ = 27.0% and τ = 1.75 μs for 3·PF6. Moreover, both 1·PF6 and 2·PF6 exhibit a TFA-induced luminescence decrease. Based on the comparison among 1·PF6, 2·PF6 and 3·PF6, we discuss the influence of intramolecular ππ interactions and Nimidazole-H/Nimidazole-CH3 units in 1·PF6 and 2·PF6 on their syntheses and luminescence.

Scaling Relations for Acidity and Reactivity of Zeolites.

Zeolites are widely applied as solid acid catalysts in various technological processes. In this work we have computationally investigated how catalytic reactivity scales with acidity for a range of zeolites with different topologies and chemical compositions. We found that straightforward correlations are limited to zeolites with the same topology. The adsorption energies of bases such as carbon monoxide (CO), acetonitrile (CH3CN), ammonia (NH3), trimethylamine (N(CH3)3), and pyridine (C5H5N) give the same trend of acid strength for FAU zeolites with varying composition. Crystal orbital Hamilton populations (COHP) analysis provides a detailed molecular orbital picture of adsorbed base molecules on the Brønsted acid sites (BAS). Bonding is dominated by strong σ donation from guest molecules to the BAS for the adsorbed CO and CH3CN complexes. An electronic descriptor of acid strength is constructed based on the bond order calculations, which is an intrinsic parameter rather than adsorption energy that contains additional contributions due to secondary effects such as van der Waals interactions with the zeolite walls. The bond order parameter derived for the CH3CN adsorption complex represents a useful descriptor for the intrinsic acid strength of FAU zeolites. For FAU zeolites the activation energy for the conversion of π-adsorbed isobutene into alkoxy species correlates well with the acid strength determined by the NH3 adsorption energies. Other zeolites such as MFI and CHA do not follow the scaling relations obtained for FAU; we ascribe this to the different van der Waals interactions and steric effects induced by zeolite framework topology.

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(ii) complexes

The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy)n(NNbpy)3−n]2+, were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH3CN show a distinct red-shift of the 1MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy)3]2+>[Ru(bpy)2(NNbpy)]2+>[Ru(NNbpy)3]2+>[Ru(bpy)(NNbpy)2]2+. Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties.

Structural study of the novel deuterated calix[4]pyrrole complex d12-meso-tetrakis(4-methoxyphenyl)-meso-tetramethylcalix[4]pyrrole-pyridine N-oxide-acetonitrile (1/1/1).

Calix[4]pyrroles act as powerful receptors for electron-rich neutral guests and anionic guests in organic solvents. For the electron-rich neutral guest pyridine N-oxide, calix[4]pyrrole, with a deep cavity, provides an appropriate environment. The ability of calix[4]pyrrole to host binding guest molecules is the result of hydrogen bonding, π-π, C-H...π and hydrophobic interactions of the cavity. The novel title complex, C52H40D12N4O4·C5H5NO·C2H3N, based on d12-meso-tetrakis(4-methoxyphenyl)-meso-tetramethylcalix[4]pyrrole, has been assembled using an excess of pyridine N-oxide and is the first deuterated complex of calix[4]pyrrole. A single-crystal X-ray study shows that the receptor adopts a cone conformation with the N-oxide fragment encapsulated deep within the cavity. 1H NMR spectroscopy was used to probe the molecular binding formation in CD3CN. The results are consistent with the single-crystal X-ray study in identifying that the pyridine N-oxide molecule occupies the cavity of the calix[4]pyrrole molecule. UV-vis spectroscopy revealed that the calix[4]pyrrole receptor molecules are able to form 1:1 inclusion complexes in CH3CN.

Dicarboxylic acid recognition of 1,8-bis(N,N'-diethylamidino)anthracene: NMR, X-ray, ESI-mass and fluorescence analyses of dicarboxylic acid binding complexes

An ethyl-substituted diamidine, 1,8-bis(N,N'-diethylamidino)anthracene (1), for the recognition of dicarboxylic acids has been designed and synthesized. The complexation of diamidine 1 with dicarboxylic acids 3, 4 and α,ω−dicarboxylic acids 6 (C6-C11), showed the formation of 1:1 complexes in CH3CN. On the other hand, for the complexation with a monocarboxylic acid and α,ω−dicarboxylic acids 6 (C3-C5), formation of the amidinium 1·2H+ was observed. The crystal structures of the 1:1 complexes of the diamidine 1 and the α,ω−dicarboxylic acids 6 were obtained, and an unusual “U-shaped conformation” of 6 was observed. Furthermore, fluorescence spectra of the diamidine 1 showed “structural vibrational bands” derived from the anthracene unit after recognition of the α,ω−dicarboxylic acids (C6-C11). However, for the formation of the dissociated amidinium 1·2H+, broad fluorescence bands were observed (without a vibrational structure). Consequently, the stability of the formed complexes can be analyzed by the patterns (vibrational structures) of the fluorescence spectra.

Ruthenium Derivatives of in Situ Generated Redox-Active 1,2-Dinitrosobenzene and 2-Nitrosoanilido. Diverse Structural and Electronic Forms.

The article describes one-pot synthesis and structural elucidation of tc-[RuII(pap)2(L•-)]ClO4 [1]ClO4 and tc-[RuII(pap)2(L'-)]ClO4 [2]ClO4, which were obtained from tc-[RuII(pap)2(EtOH)2](ClO4)2 and benzofuroxan (L = 1,2-dinitrosobenzene, an intermediate tautomeric form of the biologically active benzofuroxan, L'- = 2-nitrosoanilido, pap = 2-phenylazopyridine, tc = trans and cis corresponding to pyridine and azo nitrogen donors of pap, respectively). The same reaction with the newly synthesized and structurally characterized metal precursor cc-RuII(2,6-dichloropap)2Cl2, however, affords isomeric ct-[RuII(2,6-dichloropap)2(L•-)]+ (3a+) and tc-[RuII(2,6-dichloropap)2(L•-)]+ (3b+) (cc, ct, and tc with respect to pyridine and azo nitrogens of 2,6-dichloropap) with the structural authentication of elusive ct-isomeric form of {Ru(pap)2} family. The impact of trans or cis orientation of the nitroso group of L/L' with respect to the N═N (azo) function of pap in the complexes was reflected in the relative lengthening or shortening of the latter distance, respectively. The redox-sensitive bond parameters of 1+ and 3+ reveal the intermediate radical form of L•-, while 2+ involves in situ generated L'-. The multiple redox processes of the complexes in CH3CN are analyzed via experimental and density functional theory (DFT) and time-dependent DFT calculations. One-electron oxidation of the electron paramagnetic resonance-active radical species (1+ and 3+) leads to [RuII(pap)2(L)]2+ involving fully oxidized L0 in 12+ and 32+; the same in 2+ results in a radical species [RuII(pap)2(L'•)]2+ (22+). Successive reductions in each case are either associated with pap or L/L'--based orbitals, revealing a competitive scenario relating to their π-accepting features. The isolated or electrochemically generated radical species either by oxidation or reduction exhibits near-IR transitions in each case, attributing diverse electronic structures of the complexes in accessible redox states.