Complexes Of Donors Research Articles

Charge Polarity Control in Organic Transistors of Mixed and Segregated Complexes Based on Diaminonaphthalene and Pyrene.

Organic cocrystals of diaminonaphthalene (DAN) and diaminopyrene (DAP) with bromanil (BA) and tetracyanoquinodimethane (TCNQ) are an exemplar system for understanding the charge-transport process, where from the viewpoint of partition theory, orbital symmetry plays a crucial role in controlling the carrier charge polarity of transistors. In the mixed-stack complexes of BA and other p-quinone acceptors, a comparatively weak donor, 1,5-DAN, shows p-channel characteristics owing to the counteractive contribution of the next highest occupied molecular orbital for electron transport. This characteristic behavior occurs because the BA molecule, situated on top of the amino group, overlaps with half of the DAN molecule. By contrast, the BA and TCNQ complexes of a stronger donor, 1,6-DAP, exhibit n-channel transport due to the cooperative path and orthogonal orbitals. Similarly, TCNQ complexes of variously substituted DAN show n-channel transport, where the TCNQ molecules are located on top of the DAN molecules. However, when the carbon electrodes of (1,5-DAN)(BA) are replaced by silver, electron transport appears due to the competitive effect of the Schottky barriers. In a highly conducting segregated complex of (1,6-DAP)(TCNQ), ambipolar transistor characteristics are observed without subtracting the bulk current by using carefully prepared thin-film transistors.

Two Electron Multicenter Bonding (Pancake Bonding) between Electron Donors and Acceptors in Charge-Transfer Compounds ofN,N,N′,N′-Tetramethyl-p-phenylenediamine and (Semi)quinoid Electron Acceptors

Five charge transfer complexes of electron donor N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD or Wurster’s blue) with quinoid electron acceptors tetrafluoro- (F4Q), tetrachloro- (Cl4Q), tetrabromoquinone (Br4Q), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) were prepared and studied by X-ray crystallography, impedance spectroscopy, and DFT computations. Mixed donor–acceptor π-stacks were observed in all compounds; in TMPD·F4TCNQ, the moieties formed 2D stacked arrays. All moieties had a partial radical character due to charge transfer. The presence of two-electron multicenter bonding (pancake bonding) was confirmed by quantum chemical computation. In TMPD·F4Q, alternating longer and shorter interplanar distances were consistent with formation of pancake-bonded dimers; in complexes of TMPD with Cl4Q, Br4Q, and TCNQ, the stacks were equidistant implying existence of pancake-bonded polymers.

Facile Access to Far‐Red Fluorescent Probes with Through‐Space Charge‐Transfer Effects for In Vivo Two‐Photon Microscopy of the Mouse Cerebrovascular System

AbstractMuch effort has been devoted to the generation of fluorescent probes by synthetic approaches. In this study, we developed a facile strategy to construct far‐red fluorescent probes based on through‐space charge transfer within complexes of acceptors and donors and their “twist+twist” interactions. Owing to their rare two‐photon excitation property, the complexes could be used for in vivo imaging of the mouse cerebrovascular system.

Facile Access to Far-Red Fluorescent Probes with Through-Space Charge-Transfer Effects for In Vivo Two-Photon Microscopy of the Mouse Cerebrovascular System.

Much effort has been devoted to the generation of fluorescent probes by synthetic approaches. In this study, we developed a facile strategy to construct far-red fluorescent probes based on through-space charge transfer within complexes of acceptors and donors and their "twist+twist" interactions. Owing to their rare two-photon excitation property, the complexes could be used for in vivo imaging of the mouse cerebrovascular system.

Effects of substitutional Fe and oxygen vacancies on room temperature ferromagnetism of Fe-doped In2O3 dilute magnetic nanowires

The magnetic behavior and origin of dilute magnetic nanowires are critical for further development and application of nanoscale spintronic devices. In this work, the Fe doping into single-crystalline In 2 O 3 nanowires are fabricated using chemical vapor deposition (CVD) method to research these problems based on theoretical and experimental analysis. The XRD, XPS, TEM and XAS results show that the deposited Fe-doped In 2 O 3 nanowires possess the cubic bixbyite structure and the doped Fe ions substitute for the In sites of In 2 O 3 lattice with +2 and + 3 mixed valences. The PL results prove the existence of single ionized oxygen vacancies as well as the defect complexes of donor (oxygen vacancy)-acceptor (Fe impurity) pairs. The intrinsic room temperature ferromagnetism can be observed for the Fe-doped In 2 O 3 nanowires and the saturation magnetization largely enhance with Fe doping. The first principles calculations show that the introducing of oxygen vacancy defects can cause strong hybridization between Fe 3d and O 2p orbitals at the Fermi level, resulting in the transition from antiferromagnetic to ferromagnetic coupling between the Fe ions. These results open up the possibilities for exploring spin-electronic devices. • Effects of Fe doping on local structure, optical and magnetic properties of Fe-doped In 2 O 3 nanowires are studied. • The doped Fe ions substitute for the In sites of In 2 O 3 lattice with +2 and + 3 mixed valences. • Single ionized oxygen vacancies and the defect complexes of donor -acceptor pairs can be observed. • Introducing of oxygen vacancies results in the transition from antiferromagnetic to ferromagnetic coupling between Fe ions.

Spectral, thermal and DFT studies of novel nickel(II) complexes of 2-benzoylpyridine-N4-methyl-3- thiosemicarbazone: Crystal structure of a square planar azido-nickel(II) complex

Novel six Ni(II) complexes of an NNS donor 2-benzoylpyridine-N4-methyl-3- thiosemicarbazone(HL) are synthesized and characterized. Various physicochemical techniques are applied for the study of the coordination behavior of the thiosemicarbazone to the nickel center. In all the complexes, thiosemicarbazone is coordinated in the thiolate form. A four coordinated Ni(II) complex [NiLN3] is crystallized and its molecular and crystal structures are determined by single-crystal X-ray crystallography. Single-crystal XRD reveals that the complex got crystallized in the monoclinic space group P21/n and nickel(II) has a square planar environment. Intramolecular hydrogen bonding interactions make the complex more rigid and in the crystal lattice, the intermolecular hydrogen bonding interactions generate a supramolecular 1 D chain. The chemical reactivity behavior of the HL and six Ni(II) complexes was evaluated with the CAM-B3LYP quantum chemical calculations. The validity of electronic structure principles like Maximum Hardness, Minimum Polarizability, and Minimum Electrophilicity Principle in the study is discussed.

Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

Enantiomerically pure, C2‐symmetric 2,6‐bis(pyrazol‐3‐yl) pyridine ligands were obtained by treatment of diethyl‐2,6‐pyridinedicarbonate with (1R,4R)‐(+)‐camphor in the presence of NaH followed by ring closure with hydrazine. After twofold N‐alkylation at the pyrazole rings, the addition of iron(II) chloride led to the according pentacoordinate dichloridoiron(II) complexes. All intermediates of the ligand synthesis, the ligands bearing NCH3 and NCH2C6H5 groups and the derived iron(II) complexes were structurally characterized by means of X‐ray structure analysis. In‐situ reaction with iron(II) carboxylates resulted in the formation of iron(II) carboxylate complexes, which turned out to be highly active in the hydrosilylation of acetophenone. However, even at room temperature, the enantiomeric excess of the product 1‐phenylethanol is poor. 57Fe Mössbauer spectroscopy gave an insight into the species formed during catalysis.

Dysprosium-based complexes with a flat pentadentate donor: a magnetic and ab initio study.

The reactivity of the well-known pentadentate N3O2 Schiff base H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) towards a lanthanoid metal, in this case DyIII, has been investigated for the first time. This reactivity markedly depends on the pH of the medium and, accordingly, two different complexes, [Dy(HL)(NO3)2]·H2O (1·H2O) and [Dy(L)(NO3)(EtOH)(H2O)]·2H2O (2·2H2O), could be isolated from dysprosium(iii) nitrate and H2L. In addition, reaction of H2L with dysprosium(iii) chloride in methanol yields [Dy(HL')2][Dy(L)(Cl2)] (3), where H2L' ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N2O2 hemiacetal donor derived from the partial hydrolysis of the H2L ligand, and subsequent addition of the methanol solvent to the carbonyl group. This latter reaction has been firstly observed for a lanthanoid metal. Single crystal X-ray diffraction studies of 1·1.15Py·0.3CH3C6H5, 2·2H2O and 3 show that the Schiff base is acting as a nearly flat pentadentate donor in all the cases, this behaviour being independent of the deprotonation degree of the phenolic oxygen atoms, both mono- or bisdeprotonated. Complexes 1·1.15Py·0.3CH3C6H5 and 2·2H2O show DyN3O6 cores, with distorted geometries closer to spherical tricapped trigonal prism or spherical capped square antiprism for 1·1.15Py·0.3CH3C6H5 and 2·2H2O, respectively. In the case of 3, the [Dy(HL')2]+ cation shows a dysprosium ion in an N4O4 triangular dodecahedron environment, while the [Dy(L)(Cl2)]- anion displays a DyN3O2Cl2 core with distorted pentagonal bipyramidal geometry. Moreover, attempts to dilute 1·H2O with yttrium yielded single crystals of (Et3NH)[Dy0.09Y0.91(L)(NO3)2] (4), where the Schiff base shows a similar pentadentate coordination mode. Dynamic magnetic studies of 1·H2O, 2·2H2O and 3 show that 2·2H2O and 3 present field-induced slow relaxation of the magnetisation, with Ueff barriers of 46.1(9) and 31.0(7) K for 2·2H2O and 3, respectively, while 1·H2O does not exhibit frequency-dependent peaks of the out of phase susceptibility, even in the presence of an external dc magnetic field. By contrast, the dilute sample 4 behaves as a SIM at zero dc field, with an energy barrier of ca. 49 K. Ab initio calculations using CASSCF methods including spin-orbit effects qualitatively support the obtained magnetic results, indicating that axiality is not the only factor that should be taken into account in order to increase effective energy barriers.

PAH/PAH(CF3 )n Donor/Acceptor Charge-Transfer Complexes in Solution and in Solid-State Co-Crystals.

A solution, solid‐state, and computational study is reported of polycyclic aromatic hydrocarbon PAH/PAH(CF3)n donor/acceptor (D/A) charge‐transfer complexes that involve six PAH(CF3)n acceptors with known gas‐phase electron affinities that range from 2.11(2) to 2.805(15) eV and four PAH donors, including seven CT co‐crystal X‐ray structures that exhibit hexagonal arrays of mixed π‐stacks with 1/1, 1/2, or 2/1 D/A stoichiometries (PAH=anthracene, azulene, coronene, perylene, pyrene, triphenylene; n=5, 6). These are the first D/A CT complexes with PAH(CF3)n acceptors to be studied in detail. The nine D/A combinations were chosen to allow several structural and electronic comparisons to be made, providing new insights about controlling D/A interactions and the structures of CT co‐crystals. The comparisons include, among others, CT complexes of the same PAH(CF3)n acceptor with four PAH donors and CT complexes of the same donor with four PAH(CF3)n acceptors. All nine CT complexes exhibit charge‐transfer bands in solution with λ max between 467 and 600 nm. A plot of E(λ max) versus [IE(donor)−EA(acceptor)] for the nine CT complexes studied is linear with a slope of 0.72±0.03 eV eV−1. This plot is the first of its kind for CT complexes with structurally related donors and acceptors for which precise experimental gas‐phase IEs and EAs are known. It demonstrates that conclusions based on the common assumption that the slope of a CT E(λ max) versus [IE−EA] plot is unity may be incorrect in at least some cases and should be reconsidered.

Freeze the dynamicity: charge transfer complexation assisted control over the reaction pathway.

Charge transfer (CT) complexes between electron donor and acceptor molecules provide unique alternate D-A arrangements. However, these arrangements cannot be fully translated into chemo-selective organic transformations as the dynamicity of CT complexes in solution results in the co-existence of D-A assemblies and free monomers during the reaction time-scale. A conceptually new strategy to exploit CT complexes toward chemo-selective products by means of seizing the dynamicity of CT complexes is reported here. Aqueous CT complexes of donor and acceptor molecules bearing reactive thiol groups were frozen instantly and cryo-desiccated to get the alternate D-A assemblies intact in the solid state. Oxidation of reactive thiols in an oxygen rich solvent in the solid state resulted in the formation of the hetero-dimer exclusively. CT complexation and appropriate molecular arrangements are the key factors behind successful execution of this novel methodology. The strategy also paves the way to prepare unsymmetrical disulfide molecules from two dissimilar thiols.

Synthesis of mononuclear copper(II) complexes of N3O2 and N4O2 donors containing Schiff base ligands: Theoretical and biological observations

A new series of six mononuclear copper(II) complexes were synthesized from N3O2 and N4O2 donors containing Schiff base ligands, and characterized by various spectral methods. The geometry of the complexes was determined using UV–Vis, EPR and DFT calculations. The complexes of N3O2 donors (1–3) adopted square pyramidal geometry and the remaining complexes of N4O2 donors (4–6) show distorted octahedral geometry around copper(II) nuclei. Redox properties of the complexes show a one-electron irreversible reduction process in the cathodic potential (Epc) region from −0.74 to −0.98 V. The complexes show potent antioxidant activity against DPPH radicals. Molecular docking studies of complexes showed σ–π interaction, hydrogen bonding, electrostatic and van der Waals interactions with VEGFR2 kinase receptor. In vitro cytotoxicity of the complexes was tested against human breast cancer (MDA-MB-231) cell lines and one normal human dermal fibroblasts (NHDF) cell line through MTT assay. The morphological assessment data obtained by Hoechst 33258 and AO/EB staining revealed that the complexes induce apoptosis pathway of cell death.

Predictive Models for the Free Energy of Hydrogen Bonded Complexes with Single and Cooperative Hydrogen Bonds.

In this work, we report QSPR modeling of the free energy ΔG of 1 : 1 hydrogen bond complexes of different H-bond acceptors and donors. The modeling was performed on a large and structurally diverse set of 3373 complexes featuring a single hydrogen bond, for which ΔG was measured at 298 K in CCl4 . The models were prepared using Support Vector Machine and Multiple Linear Regression, with ISIDA fragment descriptors. The marked atoms strategy was applied at fragmentation stage, in order to capture the location of H-bond donor and acceptor centers. Different strategies of model validation have been suggested, including the targeted omission of individual H-bond acceptors and donors from the training set, in order to check whether the predictive ability of the model is not limited to the interpolation of H-bond strength between two already encountered partners. Successfully cross-validating individual models were combined into a consensus model, and challenged to predict external test sets of 629 and 12 complexes, in which donor and acceptor formed single and cooperative H-bonds, respectively. In all cases, SVM models outperform MLR. The SVM consensus model performs well both in 3-fold cross-validation (RMSE=1.50 kJ/mol), and on the external test sets containing complexes with single (RMSE=3.20 kJ/mol) and cooperative H-bonds (RMSE=1.63 kJ/mol).

Dipole analyses for short-circuit current in organic photovoltaic devices of diketopyrrolopyrrole-based donor and PCBM

Guiding principles to design highly optimized organic photovoltaic devices that achieve high power conversion efficiencies (PCEs) are strongly desired. To obtain a useful guideline, we have investigated the photo- and electrochemical properties of four diketopyrrolopyrrole (DPP) derivatives containing double DPP blocks by ab initio calculations according to Yu’s recent finding that changes in dipole moments of donor molecules by photoexcitation correlate with the short-circuit current (Carsten et al. in J Am Chem Soc 133(50):20468, 2011). We found that the short-circuit current correlates with changes in dipole moments of complexes of donor and acceptor molecules rather than with the changes in dipole moments of donor molecules only. This is because of photoinduced partial charge transfer from the HOMO on the donor to the charge-bridging orbital that is delocalized over both donor and acceptor molecules. Therefore, we suggest that the change in the dipole moment in the complex of donor and acceptor molecules is a promising guideline for designing new donor molecules to improve the short-circuit current and PCEs.

Earth abundant metal complexes of donor functionalised N-heterocyclic carbene ligands: synthesis, characterisation and application as amination catalysts

A detailed study on Co and Ni complexes of N-functionalised chelating NHC ligands applied for the mono-arylation of aniline and substituted aryl amines is presented.

THERMOVOLTAIC SYNERGETIC EFFECTS OF SELF-ORGANIZATION OF IMPURITIES AND DEFECTS IN SEMICONDUCTORS OF TYPE AIIIBV

The paper deals with the synergetic of semiconductors with deep impurities and defects. The work is based on previously developed theoretical concepts of the self-organization processes in n -type semiconductors A III B V under uniform heating. The decay arising at the growing the complexes of shallow donor + vacancy causes appearance of periodic distribution of vacancies’ concentration and that of small donors along the sample, that leads to the appearance of potential barriers isotype n-n + , i.e. appearance of internal electric fields. Separation of heat generated free carriers on these potential barriers causes the appearance of currents and voltages, synergistic in nature. The paper demonstrates the research results of the A III B V type semiconductors grown up by Chohralsky method and had n-type of conductivity: GaAs<Sn>, GaAs<Te>, InP<Te>, GaSb<Te>. Research of the structures with simple ohmic contact manufactured from these semiconductors shows that they have some rather unusual properties: at uniform heating in them temperature-depended currents and voltages appear, that is the sample of A III B V type n-semiconductors at Т > 50÷60 ºС works as generator of current and (or) generator of voltage. Such unusual properties are explained by decay of complexes of type shallow donor + vacancy under influence of temperature. As a result at self-organization processes periodical distribution of vacancies and those of effective working donors and recombination centers appear that cause appearance in the samples synergetic currents and voltages. This work can be useful at manufacturing devices based on A III B V semiconductors.

Charge-transfer complexes formed in the reaction of 2-amino-4-ethylpyridine with π-electron acceptors

Molecular charge-transfer complexes (CT) of electron donor 2-amino-4-ethylpyridine (2A4EPy) with π-acceptors tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) have been studied spectrophotometrically in chloroform at 25 °C. These were investigated through electronic, infrared, mass spectra and thermal measurements as well as elemental analysis. All formed complexes exhibit well resolved charge-transfer bands in the regions where neither donor nor acceptors have any absorption. The obtained results show that the formed solid CT-complexes have the structures [(2A4EPy)(TCNE)2], [(2A4EPy)2(DDQ)] and [(2A4EPy)2(TBCHD)] for 2-amino-4-ethylpyridine in full agreement with the known reaction stoichiometries in solution as well as the elemental measurements. The formation constant KCT, molar extinction coefficient εC.T, free energy change ΔG0, CT energy ECT, ionization potential Ip and oscillator strength ƒ have been calculated for these three CT-complexes.

Palladium(II) complexes of OS donor N-(di(butyl/phenyl)carbamothioyl)benzamide and their antiamoebic activity

Two promising palladium(II) compounds of general formula, cis–[Pd(L-O,S)2] [where HL-O,S = N-(di(butyl/phenyl)carbamothioyl)benzamide] as metal based antiamoebic drug candidates, have been synthesized. Both complexes are characterized in the solid state by FT-IR spectroscopy, TGA and single crystal X-ray study, as well as in solution by other spectroscopic techniques such as 1H and 13C NMR, and UV–visible. All these studies confirm the coordination of ligands through oxygen and sulphur atoms upon thioenolization induced delocalization. Complexes adopt cis-configuration in the solid state. Both the complexes and their respective ligands were screened in vitro for antiamoebic activity against HM1:1MSS strain of Entamoeba histolytica by microdilution method and cell viability in response to drugs was checked by using MTT assay. The IC50 values in the range 0.30–0.80 μM for ligands as well as complexes compared to 1.40 for metronidazole along with their similar inhibitory effect on cell viability of HEK293 cells like metronidazole make them promising future antiamoebic drugs.

Comparison of hydrogen bonds, halogen bonds, C[sbnd]H⋯π interactions, and C[sbnd]X⋯π interactions using high-level ab initio methods

High quality CCSD(T) and DFT-SAPT potential energy curves were generated for complexes of HCN, BrCN, and HBr donors with formaldehyde and benzene acceptors in order to compare the strengths and properties of hydrogen bonds, halogen bonds, CH⋯π interactions, and CBr⋯π interactions. It is found that interactions involving BrCN, which has a large region of positive charge, are similar in strength to interactions involving HCN. Dispersion plays a pronounced role in YBr⋯π complexes, accounting for about two thirds of attraction in the HBr⋯C6H6 complex. As might be expected, interactions involving halogens have stronger contributions from dispersion.

Cu(II) complexes of a new tetradentate N2SO donor: synthesis, structure, electrochemistry, and DFT computation

Cu(II) complexes having distorted square pyramidal geometry with N2SO donor azo–thioether ligand, [Cu(L)X] (X = Cl (1) and Br (2)), have been synthesized and characterized. The geometries of the complexes are confirmed by single crystal X-ray analysis. The complexes form supramolecular 1D chains by intermolecular H-bonding and π–π interaction between the pyridines. Spectral and electrochemical properties have been studied. Electronic structure and spectral properties are explained by DFT and TDDFT analysis.

O–H···S Hydrogen Bonds Conform to the Acid–Base Formalism

Hydrogen bonding interaction between the ROH hydrogen bond donor and sulfur atom as an acceptor has not been as well characterized as the O-H···O interaction. The strength of O-H···O interactions for a given donor has been well documented to scale linearly with the proton affinity (PA) of the H-bond acceptor. In this regard, O-H···O interactions conform to the acid-base formalism. The importance of such correlation is to be able to estimate molecular property of the complex from the known thermodynamic data of its constituents. In this work, we investigate the properties of O-H···S interaction in the complexes of the H-bond donor and sulfur containing acceptors of varying proton affinity. The hydrogen bonded complexes of p-Fluorophenol (FP) with four different sulfur containing acceptors and their oxygen analogues, namely H2O/H2S, MeOH/MeSH, Me2O/Me2S and tetrahydrofuran (THF)/tetrahydrothiophene (THT) were characterized in regard to its S1-S0 excitation spectra and the IR spectra. Two-color resonantly enhanced multiphoton ionization (2c-R2PI), resonant ion-dip infrared (RIDIR) spectroscopy, and IR-UV hole burning spectroscopic techniques were used to probe the hydrogen bonds in the aforementioned complexes. The spectroscopic data along with the ab initio calculations were used to deduce the strength of the O-H···S hydrogen bonding interactions in these system relative to that in the O-H···O interactions. It was found that, despite being dominated by the dispersion interaction, the O-H···S interactions conform to the acid-base formalism as in the case of more conventional O-H···O interactions. The dissociation energies and the red shifts in the O-H stretching frequencies correlated very well with the proton affinity of the acceptors. However, the O-H···S interaction did not follow the same correlation as that in the O-H···O H-bond. The energy decomposition analysis showed that the dissociation energies and the red shifts in the O-H stretching frequencies follow a unified correlation if these two parameters were correlated with the sum of the charge transfer and the exchange component of the total binding energy.