X-ray Structural Studies Research Articles

Intramolecular cyclization to fused pyranoisoxazoles and molecular packing motifs identification through X-ray structural studies

The present work describes intramolecular cyclization of 4-(hydroxyamino)-2-oxo-6-aryl-N-(substituted)-2H-pyran-3-carboxamides (1a-e) under the basic condition to yield fused pyranoisoxazoles (2a-e). The X-ray structural studies delineate a network of non-covalent forces that provided a molecular packing motif to generate a reproducible stacking pattern towards column scaffold formation in the pyranoisoxazole crystal system.

Synthesis, characterization, 31P{1H} NMR, X-ray structure and voltammetric study of 2-mercaptothiazolines and phosphines ruthenium(II) complexes

In this work, complexes containing mercaptothiazolines, and mono- and diphosphines with the general formula [Ru(N−S)2(P)2] or [Ru(N−S)2(P-P)] – N–S−: 1,3-thiazoline-2-thionate (tzt− - a) and benzo-1,3-thiazoline-2-thionate (bzoxt− - b), and P2 = monophosphine: P{p-tol}3 – 2; P-P = dppe – 3, dppp – 4, dppb – 5, dppf – 6 or DPEPhos – 7 were synthesized. The complexes were characterized by 1H and 31P NMR, vibrational spectroscopy, elemental analysis, and the molecular structures of 3a, 4a, 5a, 6a•CH2Cl2 and 7a were solved by X-ray diffraction. The Hirshfeld surface analysis and the 2D fingerprint plots were performed. The 1H NMR spectra of the compounds revealed the signals of the ligands and the main feature is the absence of the NH signal of the protonated ligands TztH and BzoxtH supporting the coordination in their anionic forms, which is also evidenced by the vibrational spectroscopy and molar conductivity studies. The 31P{1H} NMR spectra present only one singlet indicating the chemical equivalence of both phosphorus nuclei and in a region compatible with phosphorus cis-positioned for the P(p-tol)3 and for the potentially trans-spanning dppf and DPEPhos, whereas for the other diphosphines (dppe, dppp and dppb) only the cis-configuration is expected. The molecular structure revealed the Ru center is sited on a distorted octahedral geometry mainly as a consequence of the formation of four-membered chelate rings involving the N–S− ligand. The coordination sphere is completed with two phosphorus atoms positioned in a cis-fashion while trans to the nitrogen atoms of the tzt− ligand, and the remaining sulfur donors (thiolate) of tzt− ligand positioned trans to each other. The cyclic voltammograms of the complexes presented one monoelectronic and reversible process attributed to the Ru3+/Ru2+ couple, and for the complexes with dppf an additional redox process is observed due to the Fe3+/Fe2+ couple.

Structural Diversity in the Reactions of Dimetallic Alkyl Titanium Oxides with Isonitriles and Nitriles

A detailed study of the reaction of the dinuclear [{Ti(η5-C5Me5)R2}2(μ-O)] (R = Me 1, CH2Ph 2) compounds with a series of organic isonitriles (R′NC, R′ = tBu, iPr, CH2SiMe3, Xyl) (Xyl = 2,6-Me2C6H3) and nitriles (R′CN, R′ = tBu, iPr, SiMe3) has been carried out. Single-crystal X-ray structural studies revealed a variety of reactivity and structural moieties. Theoretical calculations (density functional theory, DFT) were used to understand the mechanism of some uncommon reactions observed experimentally. Reactions of 1 and 2 with isocyanides tBuNC, iPrNC, and Me3SiCH2NC led to the formation of dimetallic η2-iminoacyl species [{Ti(η5-C5Me5)(R′NCR)R}2(μ-O)] (R = Me, R′ = tBu 3, iPr 4, CH2SiMe3 5; R = CH2Ph, R′ = CH2SiMe3 6). Complex 4 underwent net rearrangements at room temperature to give the imido-vinylamido derivative [Ti2(η5-C5Me5)2(μ-O)(μ-NiPr) {N(iPr)CMe═CMe2}Me] (7), whereas the reaction of complex 2 with XylNC rendered the N─C bond cleavage product [{Ti(η5-C5Me5)(CH═CHPh)}(μ-O)(μ-κ2-N,C─N(MeC6H3)CH2){Ti(η5-C5Me5)}] (8). The reactions of 1 with nitriles tBuCN and iPrCN gave the ketimido products [{Ti(η5-C5Me5)Me(CN(Me)R′)}2(μ-O)] (R′ = tBu 9, iPr 10), whereas the analogous processes with 2 gave the alkenyl-imido complexes [{Ti(η5-C5Me5)(CH2Ph)2}(μ-O){Ti(η5-C5Me5)(═NC(R′)═C(H)Ph)(NCR′)}] (R′ = tBu 11, iPr 12) with the concomitant coordination of a nitrile molecule. Complex 1 reacts with Me3SiCN to afford the nitrile–isonitrile isomerization product [{Ti(η5-C5Me5)Me2}(μ-O){Ti(η5-C5Me5)(κ2-C,N-Me2CNSiMe3)(CNSiMe3)] (13).

Synthesis of heptanuclear Ni4Dy3 coordination aggregate using tridentate ligand: X-ray structure, magnetism and theoretical studies

The Schiff base ligand, 2-(((2-hydroxybenzyl)imino)methyl)phenol (H2L) having ONO donor centres are utilized to synthesize {Ni4Dy3} coordination aggregate following the support of six benzoate bridging groups. Sequential addition of Dy(NO3)3·6H2O and NiCl2·6H2O to H2L followed by PhCO2Na completes the coordination driven aggregation of heptanuclear Na[Ni4Dy3(L)4(μ3-OH)4(μ1,1,3,3-PhCO2)2(μ1,3-PhCO2)4(CH3OH)4]∙CH2Cl2·9H2O (1) having 2,3,6M7 − 1 topology. Two adjacent perpendicular inverse Ni2Dy2 partial di-cubane units sharing a common vertex through the central DyIII ion resulted a new structural arrangement within the Ni − Dy family of coordination aggregates. The complex shows no slow magnetic relaxation under zero applied fields and only shows a very weak field dependent magnetization. The DFT calculations revealed weak ferromagnetic exchange between benzoato-bridged NiII ions, whereas the CASSCF calculations were used to identify magnetic anisotropy in NiII and DyIII ions resulting in low-lying excited states of DyIII ions with significant probability for the quantum tunneling of the magnetization, which rationalize the observed fast dynamics in the magnetic properties.

Synthesis of luminescent phosphine-containing rigid-rod dinuclear alkynylgold(I) complexes and their X-Ray structural, photophysical, self-assembly and electroluminescence studies

A series of rigid-rod dinuclear alkynylgold(I) complexes bearing triethylene glycol monomethyl ether or dibutoxy-substituted oligo(p-phenylene ethynylene)s moieties as the backbone, and phosphine ligands that are charge-neutral or bear a positive or negative charge, has been designed and synthesized. The alkynylgold(I) complexes with charge-neutral phosphines are found to show polymeric zig-zag chain structure with short gold‧‧‧gold distances in their X-ray crystal structures, while those with negatively charged phosphine ligands demonstrate spherical aggregates in dimethyl sulfoxide (DMSO)-water dispersions. The aggregation behaviour of the complex with positively charged phosphine ligand is found to follow an isodesmic mechanism upon increasing the water content in DMSO. Representative complexes have been applied as the emitting material in solution-processed organic light-emitting devices, exhibiting sky-blue emission with emission maxima at 432 nm. This work has provided further insights into the aggregation behaviour of this class of alkynylgold(I) complexes, as well as the understanding of their molecular packing and alignment for the future design of structurally-related rigid-rod organometallic materials.

Synthesis, spectral characterization, optical properties and X-ray structural studies of S centrosymmetric N2S2 or N2S2O2 donor Schiff base ligand and its binuclear transition metal complexes

A new chelate namely 2,2′-thiobis(N\\-thiophen-2-ylmethyylene) acetohydrazide) (H2TTAH) was synthesized and its metal complexes with Co (II), Ni (II), Cu (II), and Zn (II) ions. The isolated complexes were characterized by conventional spectroscopic (IR, UV-visible, ESR, 1H, 13C-NMR, and mass), elemental analysis, and magnetic as well as thermal measurements. H2TTAH binds either as neutral tetra-dentate and mono- or dibasic NNOOSS hexadentate coordinating two metal ions. The metal complexes afforded the formulae: [Cu2(TTAH)Cl3(C2H5OH)3]0.5C2H5OH.H2O (1), [Co2(TTAH)(C5H5N)]Cl2.2.5C2H5OH (2), [Ni2(TTAH)(C5H5N)2(OH)2(C2H5OH)2] (3) and [Zn2(TTAH)2)(OH)4(C5H5N)2].C2H5OH (4). On the premise of their electronic spectra and magnetic moments data; tetrahedral for Co (II) and octahedral geometries for other complexes were suggested. X-ray powder diffraction technique was used to obtain more details of the chemical constitution of (2) complex. The geometries of all studied compounds were further affirmed by DFT method calculations. Also, all compounds were examined for their antibacterial and superoxide dismutase (SOD)-like activities.

Synthesis and X-ray Structural Study of Dioxalate Complexes of Uranyl and Plutonyl with Urea

Synthesis and X-ray Structural Study of Dioxalate Complexes of Uranyl and Plutonyl with Urea

Uranyl complexes of p-t-butylcalix[8]arene as H-bond acceptors—subtle effects of the donors

Leaving a mixture of excess N,N,N′,N′-tetramethyl-1,4-butanediamine (Me4BDA) with p-t-butylcalix[8]arene (L) and [(UO2)(dmso)5](ClO4)2 in a 1:2 ratio in acetonitrile solution to stand for an extended period resulted in the deposition of a mixture of three different crystalline materials. Single crystal X-ray structural studies were carried out to determine that the three materials were the solvated uncomplexed macrocycle L.1.5MeCN, and two uranyl complexes. These were formulated as (Me4BDAH2)2+[(HO)(UO2)2(L-5H)]2–·9MeCN·H2O and (Me4BDAH2)2+[HO(UO2)2{L-5H)]2–·(Me3BDAH)+[H2O(UO2)2(L-5H)]−·Me4BDA·14MeCN·H2O·CH3OH respectively. In contrast to analogous systems based on 1,2-ethanediamine and 1,3-propanediamine derivatives, extension of the chain length separating the N-centres to (CH2)4 in the present systems has resulted in the formation of polymeric chains where the calixuranate anions are linked by H-bond acceptance from diammonium units. These links are still not completely direct and pass in part through solvent bridges. Direct double interactions do occur in the inverse situation where the calixarene acts as an H-bond donor to neutral 1,4-butanediamine species but lead only to dimerisation.

Synthesis, X-ray structure, spectroscopic electrochemistry, anti-nociceptive activity and DFT study of cis-[Ru(EPh3)(L)Cl2] complexes (E = P, as and Sb) (L = thioether-azoimine tridentate SNN donor ligands)

The complexes cis-[Ru(EPh3)(L1)Cl2] (1–3) {L1 = (2-PhS)C6H4N = NC(COCH3)-NC6H5, E = P (1); As (2), Sb (3)} and cis-[Ru(PPh3)(L2)Cl2] (4) {L4 = (2-CH3S)C6H4N = N-(COCH3) = NC6H5} have been synthesized by reacting Ru(EPh3)3Cl2 and thioether-azoimine ligand (H2L1 and H2L4) in refluxing ethanol. The complexes have been characterized by IR, NMR, UV–Vis spectroscopy and cyclic voltammetry. The structures of 2 and 4 have been confirmed by single crystal X-ray diffraction. The electronic spectra of the complexes show MLCT and intense LLCT transitions. Cyclic voltammetric studies show one quasi reversible Ru(III)/Ru(II) oxidation couple and one L(0/−1) electron reduction, respectively. Antinociceptive activity study shows that the most active compound is complex 4 which has 70% inhibition at 45 µmol/Kg. The ligands were inactive, however, the complexes 1–4, significantly reduced the pain response in dose dependent manner (p < 0.05) in the acetic-acid-induced writhing test relative to control ligands. The compounds 2 and 4 possessed strong antinociceptive activity and thus are strong candidates for further detailed studies. The structure–activity relationships were also investigated by comparing the antinociceptive activity of complexes 1 and 4. The results show that changing the phenyl group as in complex 1 to a methyl group as in complex 4 increased the antinociceptive effects. The electronic structure, redox and absorption properties of the complexes have been explained based on DFT and TDDFT calculations.

Synthesis, X-ray structure, Hirshfeld analysis and DFT studies of Ni(II) complexes with pyridine-type ligands and monoanionic (SCN¯, N3¯ and NO3¯) ligands

The molecular and supramolecular structures of two self-assembled Ni(II) complexes with pyridine-type ligands (34Lut: 3,4-lutidine and 4Pic: 4-picoline) comprising different anions (SCN¯, N3¯and NO3¯) were presented. The dinuclear [Ni(34Lut)3(SCN)2]2(1) complexcomprises a hexa-coordinated Ni(II) with NiN5S coordination environment from three 34Lut, one isothiocyanate, in addition to two SCN¯ connecting the two Ni(II) centres via µ(1,3) coordination mode. Structure of complex 2 has the two complex units [Ni(4Pic)4(N3)2][Ni(4Pic)4(NO3)2], in which the two Ni(II) centers have also hexa-coordinated environments with NiN6 and NiN4O2 coordination spheres. In both units, there are four 4Pic ligand units coordinating the Ni(II) via the pyridine nitrogen atom and two anions in anti-positions to one another. In the first unit, the two azides have terminal coordination mode. In the second unit, there are two monodentate nitrate ions coordinating the Ni(II) ion via one oxygen atom. Molecular packing analysis using Hirshfeld calculations revealed the importance of the S…H (20.4%) and CH…π (25.2%) interactions in 1. For complex 2, the N…H (16.2%) and O…H (20.7%) contacts are the most important in [Ni(4Pic)4(N3)2] and [Ni(4Pic)4(NO3)2] complex units, respectively. The H…H contact percentages are 50.5, 54.6 and 51.3%, respectively which are the most common in all complex units. Using DFT calculations, the charge of the Ni(II) ion decreased to 0.7792, 0.8136 and 0.9377 e in the thiocyanato, azido and nitrato complexes, respectively. Using AIM calculations, the Ni-N, Ni-S and Ni-O bonds showed the characteristics of mainly closed shell interactions.

Metal-Organic Frameworks for Highly Selective Separation of Xylene Isomers and Single-Crystal X-ray Study of Aromatic Guest-Host Inclusion Compounds.

Separation of hydrocarbon molecules, such as benzene/cyclohexane and o-xylene/m-xylene/p-xylene, is relevant due to their widespread application as chemical feedstock but challenging because of their similar boiling points and close molecular sizes. Physisorption separation could offer an energy-efficient solution to this problem, but the design and synthesis of sorbents that exhibit high selectivity for one of the hydrocarbons remain a largely unmet challenge. Herein, we report a new heterometallic MOF with a unique tortuous shape of channels decorated with aromatic sorption sites [Li2Zn2(bpy)(ndc)3] (NIIC-30(Ph), bpy = 4,4'-bipyridine, ndc2- = naphthalene-1,4-dicarboxylate) and study of its benzene/cyclohexane and xylene vapor and liquid separation. For an equimolar benzene/cyclohexane mixture, it is possible to achieve a 10-fold excess of benzene in the adsorbed phase. In the case of xylenes, microporous framework NIIC-30(Ph) demonstrates outstanding selective sorption properties and becomes a new benchmark for m-/o-xylene separation. In addition, NIIC-30(Ph) is stable enough to carry out at least three separation cycles of benzene/cyclohexane mixtures or ternary o-xylene/m-xylene/p-xylene mixtures both in the liquid and in the vapor phase. Insights into the performance of NIIC-30(Ph) are gained from X-ray structural studies of each aromatic guest inclusion compound.

3-Acetyl-2,5-dimethyl-1,4-diphenylpyrrole: Synthesis, X-ray structure, DFT, TDDFT studies and anti-corrosion activity

• Eco-friendly synthesis of 3-acetyl-2,5-dimethyl-1,4-diphenylpyrrole: X-ray structure, DFT and TDDFT studies. • UV-Visible spectrum was studied using TD-DFT/B3LYP/ 6-31 G(d,p) method. • FT-IR spectrum of product was compared with the scaled results. • The intramolecular interaction has been determined between the oxygen atom and the methyl group bounded to the pyrrole moiety. • Experimental 1 H NMR and 13 C NMR chemical shifts have been compared with the theoretical data. A single-crystal X-ray diffraction analysis of a pyrrole derivative namely 3-acetyl-2,5-dimethyl-1,4-diphenylpyrrole, that was synthesized by a multicomponent reaction, is described in this paper. The density functional theory (DFT) was performed using B3LYP functional with 6-31G(d, p) basis set for the determination of the molecular geometry and the electronic transitions of the studied compound. Moreover, calculations of the FT-IR vibrational frequencies, 1 H and 13 C NMR chemical shifts are in good agreement with the experimental values. Electrochemical tests were investigated by potentiodynamic polarization and AC impedance measurement to evaluate the anti-corrosion activity of the compound.

Change of tension state of electrolytic nickel under exposure to plasma

A study of the effect of cold air plasma on cathode nickel grade N-1 has been carried out. The changes in the microstructure, macro- and microstresses, as well as static displacements of atoms from equilibrium positions are investigated. By the method of aim metallography it was shown that the microstructure does not change under plasma exposure. X-ray structural studies have established that the level of microstresses does not change when exposed to plasma. A decrease in the magnitude of macrostresses is shown when exposed to plasma for 5 and 10 min. Macrostresses in this case vary from tensile stresses in the initial state to compressive stresses after exposure to plasma. The change in the static displacements of atoms from the equilibrium positions and their decrease when exposed to plasma have been established.

Structural and spectroscopic characterization of an einsteinium complex.

The transplutonium elements (atomic numbers 95-103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies1. Here we characterize a coordination complex of einsteinium, using less than 200 nanograms of 254Es (withhalf-life of 275.7(5) days), with an organic hydroxypyridinone-based chelating ligand. X-ray absorption spectroscopic and structural studies are used to determine the energy of the L3-edge and a bond distance of einsteinium. Photophysical measurements show antenna sensitization of EsIII luminescence; they also reveal a hypsochromic shift on metal complexation, which had not previously been observed in lower-atomic-number actinide elements. These findings are indicative of an intermediate spin-orbit coupling scheme in which j-j coupling (whereby single-electron orbital angular momentum and spin are first coupled to form a total angular momentum, j) prevails over Russell-Saunders coupling. Together with previous actinide complexation studies2, our results highlight the need to continue studying the unusual behaviour of the actinide elements, especially those that are scarce and short-lived.

Planar chiral [2.2]paracyclophanyl-based boron fluoride complexes: synthesis, crystal structure and photophysical properties.

Planar chiral [2.2]paracyclophanyl-based boron fluoride complexes (3a-3d) were designed and facilely synthesized. The X-ray structure study, theoretical calculations and CD spectra reveal the intense emission and planar chiral structures of these complexes. In particular, 3a-3d show moderate quantum yields and large Stokes shifts both in solution and solid state. Furthermore, the blue-shifted mechanochromic properties of 3a and 3b were both investigated in the solid state. This work is the first study on planar chiral boron monofluoride complexes within the boron fluoride complex field.

The Influence of the Pipelines Operation Term in Aggressive Environments on the Gas Content and Structure of Structural Steels

X-ray structural studies have shown that with the increase of the life of the pipes, the surface layers of the metal adsorb a significant amount of gases (hydrogen, oxygen and sulfur), especially this is strongly manifested in the field of corrosion defects (ulcers, pitting). Also, it was found that in the process of long-term operation, the metal of the pipe walls is heavily flooded, which directly leads to its brittle and, as a consequence, increased hardness and reduced ductility. Such studies are unique in the subject of corrosion-mechanical resistance of metal and its degradation during long-term operation in the presence of alternating loads and at the same time, the aggressive environments of oil and gas fields.

РАЗРАБОТКА ФУНКЦИОНАЛЬНЫХ ИОННО-ПЛАЗМЕННЫХ ПОКРЫТИЙ НА ОСНОВЕ МНОГОСЛОЙНЫХ ГЕТЕРОГЕННЫХ СТРУКТУР НИТРИДОВ МЕТАЛЛОВ

The article deals with the development of ion-plasma coating systems based on multilayer heterogeneous structures of the type (Me1)N/(Me2)N, (Me1–Me2)N/(Me3)N, (Me1–Me2–Me3)N/(Me4)N, where Me: Ti, Al, Cr, Mo. Tests for heat resistance and wear resistance, gas-abrasive resistance, metallographic and x-ray structural studies were carried out. It is shown that the ion-plasma coating (Ti–Al–Cr)N/CrN can be used to increase the heat resistance, wear resistance (including abrasive) of steel and titanium intermetallic parts of aircraft gas turbine engines operating in the temperature range up to 800 °C.

A rare isostructural series of 3d-4f cyanido-bridged heterometallic squares obtained by assembling [FeIII{HB(pz)3}(CN)3]- and LnIII ions: synthesis, X-ray structure and cryomagnetic study.

A new series of cyanido-bridged {FeIIILnIII}2 neutral molecular squares of general formula [Fe{HB(pz)3}(CN)(μ-CN)2Ln(NO3)2(pyim)(Ph3PO)]2·2CH3CN [Ln = Ce (1), Pr (2), Nd (3), Gd (4), Tb (5), Dy (6) and Er (7); {HB(pz)3}- = hydrotris(pyrazolyl)borate, pyim = 2-(1H-imidazol-2-yl)pyridine and Ph3PO = triphenylphosphine oxide] were obtained by reacting the low-spin [Fe{HB(pz)3}(CN)3]- species with the preformed [LnIII(pyim)(NO3)2(pyim)(Ph3PO)]+ complex anions (generated in situ by mixing the nitrate salt of each Ln(III) ion with pyim and Ph3PO molecules). Single-crystal X-ray diffraction studies show that 1-7 are isostructural compounds that crystallize in the triclinic P1̄ space group. Their crystal structures consist of centrosymmetric cyanido-bridged {FeIIILnIII}2 molecular squares where two [Fe{HB(pz)3}(CN)3]- units adopt bis-monodentate coordination modes towards two [LnIII(pyim)(NO3)2(pyim)(Ph3PO)]+ moieties. The cis-oriented convergent sites from both low-spin FeIII and LnIII fragments form a quasi square-shaped molecule in which the 3d and 4f ions alternatively occupy the corners of the square. Both FeIII ions show a distorted octahedral surrounding (C3v symmetry), whereas the LnIII ions exhibit a distorted muffin-like geometry (Cs symmetry) in 1-7. The intramolecular FeIII⋯LnIII distances across the two cyanido-bridges range from ca. 5.48/5.46 up to ca. 5.58/5.61 Å. The molecular squares in 1-7 are interlinked through hydrogen bonds, weak π⋯π stacking and very weak C-H⋯π type interactions into three-dimensional supramolecular networks. The analysis of the solid-state direct-current (dc) magnetic susceptibility data of 1-7 in the temperature range 1.9-300 K reveals the occurrence of weak intra- and intermolecular antiferromagnetic interactions. The small intramolecular antiferromagnetic couplings in 4 compare well with those previously reported for parent systems. Although the coexistence of the spin-orbit coupling (SOC) of the low-spin iron(III) and lanthanide(III) ions in the remaining compounds together with the ligand field effects mask the visualization and make difficult the evaluation of the possible magnetic interactions in them, we were able to do it through a SOC model applied on exact or effective Hamiltonians. Frequency-dependent alternating current magnetic susceptibility signals in the temperature range 2.0-9.0 K under zero and non-zero static fields were observed for 5-7 which indicate slow magnetic relaxation (SMM) behavior. The usual absence of χ''M maxima moved us to estimate their energy barriers through ln(χ''M/ χ'M) vs. 1/T plots, obtaining values from 25 to 40 cm-1.

Peripheral Ligand Effect on the Photophysical Property of Octahedral Iridium Complex: o-Aryl Substitution on the Phenyl Units of Homoleptic IrIII(C∧C)3 Complexes (C∧C = 1-Phenyl-3-methylimidazolin-2-ylidene-C,C2') for Deep Blue Phosphorescence.

To evaluate the efficacy of ortho-arylation in the second coordination sphere of octahedral iridium complex, a series of homoleptic N-heterocyclic carbene (NHC)-based Ir(C∧CR)3-type complexes were designed and prepared by introducing various substituents (R = H, Me, Ph, MePh, and diMePh) at the ortho-position of the aryl unit of the orthometalated phenyl group. In solution, an unnoticeable increase of emission quantum yields was observed within the variation of the ortho-substituent of the sterically demanding side-branch, a diMePh- group, showing the radiative quantum yield of mer-Ir(C∧CdiMePh)3 (ΦPL = 1.9%), being higher than that of the unsubstituted carbene-based mer-Ir(C∧CH)3 (ΦPL = 1.2%), due to a considerable difference in the nonradiative decay rate (knr = 65.40 × 105 s-1 for mer-Ir(C∧CdiMePh)3 vs knr = 141.1 × 105 s-1 for mer-Ir(C∧CH)3). Such a difference is attributed to the reduction of nonradiative pathway via the 3MLCT → 3MC transition by the widening gap between triplet emissive states and 3MC state, and a rigidity increase in structure by steric hindrance of bulky aryl substituent. In contrast, significant increase of emission quantum yield was observed in the films cast by spin coating, and fac-/mer-Ir(C∧CdiMePh)3 (ΦPL = 60.1/49.1%) were the most efficient ones among NHC-Ir(III) complexes, compatible with the assumption that the secondary coordination effect, i.e. a peripheral constraint, was put into action. As the substituent R increases in size on going from H, Me, Ph, MePh, to diMePh, notable structural changes in the periphery are evident, while an increase of emission quantum yields is also seen. Such a peripheral difference was under scrutiny first with X-ray structural studies, and its manifestation in photophysics was investigated along with quantum calculations that finally addressed the peripheral effect being maximized at R = diMePh. In the application of PhOLED, the mer-Ir(C∧CdiMePh)3-doped multilayer device showed highly enhanced efficiency with an external quantum efficiency (EQE) of up to 8.1%, compared to that of the mer-Ir(C∧CH)3-based device (1.2%), indicating the multiple positive effects of bulky aryl substitution of Ir(III) dopant. A deep-blue CIE chromaticity diagram (0.16, 0.09) was achieved from the device using mer-Ir(C∧CdiMePh)3 as a dopant.

Influence of carbon in the sp1 hybridized state on the structure of PbSe thin films

The optical reflection spectra of PbSe films and PbSe films coated with a layer of linear chain carbon were studied by IR Fourier spectroscopy in the wavelength range of 1-16 μm. In all IR spectra of the samples, two minima were observed, related to plasma fluctuations of free charge carriers and related to the PbSe and PbSeO3 phases. It was found that the PbSe film coated with a layer of linear chain carbon is less oxidized. This conclusion is confirmed by the results of x-ray structural studies of the samples. The results showed a decrease in the percentage of oxygen-containing phase PbSeO3 by 2-4 times.