Single-crystal X-ray Diffractometry Research Articles

N‒N hydrazonyl bond cleavage in benzothiazolyl-hydrazino-phenathrenequinone mediated by ruthenium(II) via an anion radical intermediate

The complexes [Ru(LBenz)H(CO)(PPh3)2] 2, [Ru(LBenz)Cl(CO)(PPh3)2] 3, (ligand behaving as bidentate monoanionic) and [Ru(LBenz)Cl(CO)(PPh3)] 4, (ligand is tridentate monoanionic) have been synthesized starting from benzothiazolyl-hydrazino-phenathrenequinone (HL) 1 and [RuH(CO)Cl(PPh3)3]. These are characterized by electrochemical and spectral methods as well as single crystal X-ray diffractometry (SCXRD). Upon treating with NaBH4, 3 accepts an electron within the coordinated ligand framework and the anionic hydrazonyl-N takes up a proton to be transformed to meta-stable hydrazinoquinone anion radical complex of ruthenium(II) [Ru(HLBenz•‒)Cl(CO)(PPh3)2] 5, possibly via concerted proton electron transfer process (CPET). Thus, the redox non-innocent character of the ligand upon complexation with ruthenium(II), has been disclosed and it is attributed to presence of low lying π* orbitals of almost entirely of phenanthraquinone and hydrazone character. In 5, the π‒acceptor ability of the ligand donor centres are reduced due to the existence of an odd electron in SOMO and hence the M-L distances around the coordination sphere are altered. The N‒N (hydrazonyl bond length increases from 1.296(6) Å in 3 to 1.429 Å in 5, leading to lesser thermodynamic stability of the latter and upon standing, the N‒N bond is cleaved to be transformed to 6+, possibly via the formation of iminoquinone anion radical complex, [6] (reported elsewhere). Also, it is via the dissociation of N‒N (hydrazonyl) bond, the biologically important molecule 2-aminobenzothiazole is formed along with 6+, so as to provide a novel route for its synthesis.

Synthesis and Structure of Unsymmetrical Anthracenyl-Isoxazole Antitumor Agents Via the Diastereoselective Bromination of 3-(9′-Anthryl)-Isoxazole Esters

In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report herein. The C-9 nitrile oxide, after its reaction with bromine, was isolated, but when subjected to re-aromatization, it returned to the starting 10-bromo nitrile oxide 1, which did provide an accurate crystal structure, with R = 0.018. The 10-halogenated 3-(9’-anthryl)-isoxazole esters were subjected to bromination and re-aromatization. Surprisingly, the yields obtained in the presence of the isoxazole were reasonably good (62–68% isolated yields), and the major diastereomers allowed for the characterization using Sc-xrd. The penta bromo product 2 showed a trans, trans, cis relationship for the four bromines on the A-ring of the anthracene, and we observed that for the unit cell, the atropisomers displayed a 1:1 ratio at the chiral axis between the isoxazole and anthrancene rings. Similarly, the 10-chloro 3 indicated a ratio of 1:1 at the chiral axis in the crystal structure. A base-induced re-aromatization afforded 3,10-dihalogenated analogues selectively in very good yields (X = Cl, 89%; X = Br 92%), of which the dibromo 4 was characterized using Sc-xrd. The improved yields of the unique diastereomeric bromination products suggested the consideration of a novel electrophilic aromatic substitution mechanism driven by the stereo-electronic environment, imposed by the isoxazole ester substituent. The promise of the application of this chemistry in the future development of AIM antitumor agents is suggested.

Three Ways to (Pseudo)cubic Structure Models: Phase Transition and Pseudosymmetry in Orthorhombic Cs3MO4 (M = V, Nb, or Ta).

The new oxometalates Cs3NbO4 and Cs3TaO4 together with Cs3VO4 crystallize with the K3NO4 structure type [Pnma, a = 12.495(2) Å, b = 9.0183(14) Å, and c = 6.6529(10) Å for the V compound; a = 12.928(2) Å, b = 9.177(3) Å, and c = 6.739(4) Å for the Nb; and a = 12.963(4) Å, b = 9.122(2) Å, and c = 6.774(1) Å for the Ta compound]. Their crystal structures were evaluated on the basis of single-crystal and powder X-ray diffractometry, assisted by vibrational spectroscopy, thermoanalysis, and DFT calculations. The crystal structures contain tetrahedral [M5+O4]3- anions, representing the first occurrence of Nb and Ta in a tetrahedral oxidic environment. Many representatives of the orthorhombic K3NO4 structure type have been described in the literature with a cubic structure model with disordered O atomic positions. Based on studies on Cs3MO4 (M = P, V, Nb, or Ta), we show here three different effects which can lead to (pseudo)cubic data sets. Two of them are problems of crystallographic nature (overlooked twinning or adverse atomic form factor ratios), but the third one, phase transformation into a plastic crystalline high-temperature modification, leads to a "truly" cubic structure with dynamically disordered (freely rotating) oxometalate anions. This might be of interest with respect to a large and growing number of sulfido- and selenidometalate materials which are today in discussion as solid-state electrolytes and to the mechanism of the unusually efficient ion transport therein.

A Linear Two-Coordinate Cr(II) Complex: Synthesis, Characterization, and Reactivity.

The synthesis and characterization of a linear two-coordinate Cr(II) amido complex, Cr{N(t Bu)Dipp}2 (Dipp=2,6-diisopropylphenyl), from the reaction of 1 molar equivalent (equiv) of CrCl2 and 2 equiv. of LiN(t Bu)Dipp is reported. Single-crystal X-ray diffractometry (SC-XRD) analysis revealed that it has a short Cr-N bond distance of 1.8878(9) Å, which could be attributed to the relatively less bulky nature of the amido ligand compared with reported systems. Furthermore, the oxidation reaction of the two-coordinate Cr(II) complex was explored. The oxidation reaction of Cr{N(t Bu)Dipp}2 with the one-electron oxidants AgOTf and [FeCp2 ][BArF 4 ] (BArF 4 - =[B{C6 H3 -3,5-(CF3 )2 }4 ]- ) afforded the trigonal planar three- and bent two-coordinate Cr(III) complexes Cr{N(t Bu)Dipp}2 (OTf) and [Cr{N(t Bu)Dipp}2 ][BArF 4 ], respectively. The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of the organic azides AdN3 (Ad=1-adamantyl) and PhN3 afforded the three-coordinate Cr(IV) imido complexes Cr{N(t Bu)Dipp}2 (NAd) and Cr{N(t Bu)Dipp}2 (NPh), respectively. The reaction of Cr{N(t Bu)Dipp}2 and two equiv. of Me3 NO afforded the Cr(VI) dioxo complex Cr{N(t Bu)Dipp}2 (O)2 . The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of CyN=C=NCy resulted in the insertion of the carbodiimide into the Cr-N bond, with the formation of a three-coordinate Cr(II) complex. Finally, density functional theory (DFT) calculations were used to elucidate the electronic structure of these complexes.

Fluorenyl-tethered N-heterocyclic carbene: An effective ancillary support for heteroleptic magnesium organometallics

Judicious designing of ancillary ligands with appropriate stetrolelectronics is critical for the chemistries of electropositive alkaline earths that typically make labile coordination to conventional donor sites. We report here a series of magnesium complexes [(LH)Mg(A)Br(thf)] (A = nBu (1), N(SiMe3)2 (2)), [(L)Mg{N(SiMe3)2}] (3), and [(L)MgMe(thf)] (4) supported by a N-heterocyclic carbene LH ([(Flu)H-(CH2)2-NHCDipp]; Dipp = 2,6-iPr2-C6H3) with a fluorenyl sidearm and its monoanionic version L- ([(Flu)-(CH2)2-NHCDipp] -). Complexes 1, 2, and 4 are characterized by single crystal X-ray diffractometry. 3 and 4 are additionally analyzed by DFT calculations. The pseudo-bidentate L- appears to be quite an effective ancillary support as evident from the monomeric nature of 4 and the thermal stability of 3 and 4 towards the deleterious Schlenk equilibrium. This is also reflected in 4′s catalytic activity in intramolecular hydroamination/cyclization of two primary aminoalkenes as model substrates, for which the presence of a spectator ligand and its ability to thwart the Schlenk equilibrium are critical. It’s also the 1st NHC-based main group catalyst for intramolecular hydroamination. Complex 2 also catalyzes the hydroboration of model substrates of carbonyl, ester, amide, and nitrile functions.

Improvement of the Thermal Stability and Aqueous Solubility of Three Matrine Salts Assembled by the Similar Structure Salt Formers.

Matrine (MAT), a natural Chinese herbal medicine, has a unique advantage in the treatment of various chronic diseases. However, its low melting point, low bioavailability, and high dosage restrict its subsequent development into new drugs. In this study, three kinds of MAT salts, namely, MAT-2,5-dihydroxybenzoic acid (MAT-25DHB), MAT-2,6-dihydroxybenzoic acid (MAT-26DHB), and MAT-salicylic acid-hydrate (MAT-SAL-H2O), were designed and synthesized to improve the drugability of MAT. The three salts were characterized by using various analytical techniques, including single-crystal X-ray diffractometry, powder X-ray diffractometry, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. The results of the thermal stability evaluation showed that the formation of salts improved the stability of MAT; MAT-25DHB is the most stable salt reported at present. The results of aqueous solubility showed that the solubility of MAT-25DHB was higher than that of MAT, while that of MAT-26DHB and MAT-SAL-H2O were less. Given that the MAT-25DHB salt further improved the solubility of MAT, it is expected to be subjected to further research as an optimized salt. Lattice energy and solvation free energy are important factors affecting the solubility of salts; the reasons for the changes of solubility and stability of three kinds of salts are explained by calculating them.

Heterometallic Co–Sr −2,3-pyridinedicarboxylate complex and its related perovskite oxide: Synthesis, structural characterization and magnetic properties

A new heterometallic complex {[CoSr(2,3-pdc)2(H2O)5]3H2O}n (1), where 2,3-H2pdc stands for 2,3-pyridinedicarboxylic acid, has been synthesized and investigated by single crystal X-Ray diffractometry, IR spectroscopy and thermal analysis. The compound is self-organized in a polymeric structure forming a 2D framework. The 2,3-pyridinedicarboxylic acid is fully deprotonated performing several types of coordination: monodentate, bridging chelating, bidentate bridging. Thermal decomposition of the heterometallic 2,3-pyridinedicarboxylate 1 leads to the formation of a perovskite type oxide of brownmillerite series, 2, with 20.8 % yield. Magnetic studies of 1 show the paramagnetic behavior of Co(II) ions with a significant influence of a ground state zero-field splitting at low temperatures. Variable field and temperature magnetic studies of the oxide product 2 (obtained by the controlled heating of 1) indicate the presence of the Sr6Co5O15, detected by the diffraction method. Also, trace amounts of SrCoO2.75 and SrCoO2.5 were revealed by magnetic and DSC methods, respectively.

Mechanical Properties and Temperature and Pressure Effects on the Crystal Structure of (2S,3S,4R)-2,3,4-(Trinitratomethyl)-1-nitroazetidine (TMNA) by Single-Crystal X-ray Diffractometry and Density Functional Theory

Mechanical Properties and Temperature and Pressure Effects on the Crystal Structure of (2S,3S,4R)-2,3,4-(Trinitratomethyl)-1-nitroazetidine (TMNA) by Single-Crystal X-ray Diffractometry and Density Functional Theory

Dioxygen-halogen bonding exemplified by crystalline peroxosolvates of N,N'-bis(haloacetyl) bispidines.

The halogen bonding in molecular crystals and supramolecular assemblies has been widely investigated. Special attention is given to the molecular structures capable of simultaneously exhibiting different types of non-covalent interactions, including conventional hydrogen bonds and halogen bonds. This paper systematically analyzes crystalline peroxosolvates of bispidine-based bis-amide derivatives, containing haloacetic acid residues, namely previously reported 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodooethanone) peroxosolvate C13H20I2N2O2·H2O2 (1) and four new crystalline compounds, 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O2·H2O2 (2), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodoethanone) peroxosolvate C13H20I2N2O5·0.5H2O2 (3), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O5·H2O2 (4), and 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-chloroethanone) peroxosolvate C13H20Cl2N2O5·H2O2 (5). Compounds 2-5 were synthesized for the first time and their crystal structures were determined by single-crystal X-ray diffractometry (SCXRD). To the best of our knowledge, 3-5 are unprecedented crystalline hydrogen peroxide adducts of organic hydroperoxides (R-OOH). Short intermolecular contacts between halogen and hydroperoxo oxygen atoms were found in 1-3. The halogen bonding of C-I(Br) fragments with dioxygen species in compounds 1-3 as well as in the previously reported cocrystal of diacetone diperoxide with triodotrinitrobenzene (6) was identified through reduced density gradient analysis, Hirshfeld surface analysis, and Bader analysis of crystalline electron density. The interactions were quantified using the electron density topological properties acquired from the periodic DFT calculations and evaluated to lie in the range of 9-19 kJ mol-1. A distinctive spectral feature was revealed for this type of interaction, involving a red shift of the characteristic O-O stretching vibration by about 6 cm-1, which appeared in IR spectra as a narrow low-intensity band in the region 837-872 cm-1.

Solvent-induced structural transformation in a one-dimensional coordination polymer.

We have rationally designed a one-dimensional coordination polymer (1D CP), termed 1D-DGIST-18, that exhibits intrinsic structural flexibility. This 1D CP enables its expansion into a three-dimensional network through supramolecular interactions involving coordinated solvents and/or ligands. The strategic selection of solvents for solvent exchange, prior to drying, significantly influences the structures of 1D-DGIST-18 by removing certain coordinating solvents and modulating π-π stacking. Consequently, a hierarchical porosity emerges, ranging from micro- to meso- to macroporous structures, which is attributed to its inherent structural dynamics. Additionally, the formation of excimers endows 1D-DGIST-18, when immersed in acetone, with 'turn-on' fluorescence, as evidenced by fluorescence decay profiles. These structural transitions within 1D-DGIST-18 are further elucidated using single-crystal X-ray diffractometry. The insights from this study provide a foundation for the design of materials with structural dynamics and tunable properties.

Supramolecular Nature of Multicomponent Crystals Formed from 2,2'-Thiodiacetic Acid with 2,6-Diaminopurine or N9-(2-Hydroxyethyl)adenine.

The synthesis and characterization of the multicomponent crystals formed by 2,2'-thiodiacetic acid (H2tda) and 2,6-diaminopurine (Hdap) or N9-(2-hydroxyethyl)adenine (9heade) are detailed in this report. These crystals exist in a salt rather than a co-crystal form, as confirmed by single crystal X-ray diffractometry, which reflects their ionic nature. This analysis confirmed proton transfer from the 2,2'-thiodiacetic acid to the basic groups of the coformers. The new multicomponent crystals have molecular formulas [(H9heade+)(Htda-)] 1 and [(H2dap+)2(tda2-)]·2H2O 2. These were also characterized using FTIR, 1H and 13C NMR and mass spectroscopies, elemental analysis, and thermogravimetric/differential scanning calorimetry (TG/DSC) analyses. In the crystal packing the ions interact with each other via O-H⋯N, O-H⋯O, N-H⋯O, and N-H⋯N hydrogen bonds, generating cyclic hydrogen-bonded motifs with graph-set notation of R22(16), R22(10), R32(10), R33(10), R22(9), R32(8), and R42(8), to form different supramolecular homo- and hetero-synthons. In addition, in the crystal packing of 2, pairs of diaminopurinium ions display a strong anti-parallel π,π-stacking interaction, characterized by short inter-centroids and interplanar distances (3.39 and 3.24 Å, respectively) and a fairly tight angle (17.5°). These assemblies were further analyzed energetically using DFT calculations, MEP surface analysis, and QTAIM characterization.

Electromagnetic wave absorption properties of porous carbon nanocomposite prepared by explosion method derived from energetic CuFe-MOF

An energetic heteronuclear metal–organic framework (MOF), denoted as {[CuIIFeIII3O(tza)6(H2O)3]·Cl·(NO3)2·4H2O}n (CuFe-MOF), was successfully synthesized and characterized using various techniques, including single-crystal X-ray diffractometry (XRD), powder X-ray diffractometry (PXRD), and scanning/transmission electron microscopy (SEM/TEM). The compound crystallized in the P63m space group, forming an infinite 3D cationic network composed of [Fe3O(tza)6]+ clusters and Cu2+ ions. Subsequently, we transformed CuFe-MOF into porous carbon nanocomposites, C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4, using an explosion method. We then investigated the electromagnetic wave (EMW) attenuation properties and mechanisms of the carbon nanocomposite. Notably, the synthesized C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4 composite material demonstrated exceptional EMW absorption. At a low frequency of 4.1 GHz with a thickness of 5.0 mm, it achieved a minimum reflection loss (RL) of −47.7 dB. Even at a high frequency of 17.8 GHz and a thickness of 1.5 mm, the minimum RL reached −41.8 dB. Moreover, this material exhibited a wide effective absorption bandwidth (EAB; RL ≤ −10 dB) spanning 14.9 GHz (3.1–18 GHz) for thicknesses between 1.0 and 5.5 mm. These attributes position the carbon composite as a strong candidate for absorption applications within the Ku, X, and C bands, making it suitable for both military and civilian usage. Our mechanistic analysis suggests that the excellent absorption performance of C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4 results from a combination of mechanisms, including electrical and magnetic loss. This research introduces an innovative approach for the fabrication of high-performance carbon composite materials via the explosive method, utilizing multinuclear energetic materials.

PI and PIII Ions Supported by BZIMPY Ligands.

We report a class of compounds in which both PIII -X and PI forms featuring the same ligand are stable and readily cycled with each other. A series of PIII -X (X=Cl, Br, I) dicationic triflate salts supported by benzyl- and allyl-substituted 2,6-bis(benzimidazole-2-yl)pyridine (BZIMPY) ligands is synthesized. Surprisingly, treatment of these with R3 PO (R=Et, Oct) results in reduction to BZIMPY-ligated PI monocationic triflate salts while treatment with Ph3 P reduces but also substitutes the compound to produce Ph3 P-BZIMPY-ligated PI dicationic triflate salts. The mechanisms of these surprising reductions are probed experimentally and rationalized computationally. The PIII -X dications are shown to be strong Lewis acids both experimentally and computationally and to readily behave as X+ , PX, and P+ transfer agents in reactions with phosphines, NHCs, and diazabutadienes. The PI mono- and dications are shown to be very effective P+ transfer agents when treated similarly. Oxidation from a monocationic PI salt back to the dicationic PIII -X (X=Cl, Br) salt was achieved by treatment with N-chlorosuccinimide (NCS) or N-bromosuccinimide (NBS). Full characterization is reported using multinuclear nuclear magnetic resonance spectroscopy, elemental analysis, and single-crystal X-ray diffractometry where suitable crystals were isolated.

Semisynthesis of Linariophyllenes A-C and Rumphellolide H, Structure Revisions and Proposed Biosynthesis Pathways.

The first semisynthetic routes toward terrestrial anti-inflammatory natural products linariophyllene A-C and the refined route toward marine natural product rumphellolide H are presented. Among the synthesized target compounds, the correct structure of linariophyllene A was determined to be the diastereomer of the originally proposed structure with an inverted stereocenter at the secondary alcohol. The proposed structures of linariophyllene B and rumphellolide H were confirmed. However, the correct structure of linariophyllene C was found to be the diastereomer of the originally proposed structure with an inverted stereocenter at the tertiary carbon of the epoxide moiety. The structures of linariophyllenes A-C and rumphellolide H were unequivocally confirmed by single-crystal X-ray diffractometry. The obtained results enabled the proposal of the biosynthetic origins of the aforementioned natural products and bolstered the diversity of available sesquiterpenoids. Linariophyllenes A-C and rumphellolide H were obtained in sufficient amounts to further expand their bioactivity profile and utility as reference standards in future studies of chemical constituents of terrestrial and marine organisms.

Topochemical Syntheses of Polyarylopeptides Involving Large Molecular Motions: Frustrated Monomer Packing Leads to the Formation of Polymer Blends.

We report the topochemical syntheses of three polyarylopeptides, wherein triazolylphenyl group is integrated into the backbone of peptide chains. We synthesized three different monomers having azide and arylacetylene as end-groups from glycine, L-alanine and L-valine. We crystallized these monomers and the crystal structures of two of them were determined by single-crystal X-ray diffractometry. Due to the steric constraints, both of these monomers crystallized with two molecules, viz. conformers A and B, in the asymmetric unit. Consistently, in both cases, the A-conformers are antiparallelly π-stacked and B-conformers are parallelly slip-stacked, exploiting weak interactions. Though the arrangements of molecules in the pristine crystals were unsuitable for topochemical reaction, upon heating, they undergo large motion inside the crystal lattice to reach a transient reactive orientation and thereby the self-sorted conformer stacks react to give a blend of triazole-linked polyarylopeptides having two different linkages. Due to the large molecular motion inside crystals, the product phase loses its crystallinity.

Four Slip-Stacked Arrangements, Three Types of Photophysics: Crystal Structure and Solid-State Fluorescence of 3,6-Diaryl Substituted Furo[3,4-c]furanone Polymorphs and Regioisomers.

Six symmetrical 3,6-diaryl (aryl=phenyl, 2-, 3- and 4-tolyl, 2,4- and 3,5-xylyl) substituted furo[3,4-c]furanones (DFF) were synthesized. The computational analysis, based on density functional theory, found eight possible centrosymmetrical slipped π-stack arrangements, formed according to electron repulsion minimization principle, as for previously reported for π-isoelectronic diketopyrrolopyrroles (DPP). One of these slipped stack arrangements was found to form infinite columns in the crystals of a new polymorph of parent phenyl derivative (with centre-to-centre distance CC=6.975 Å), other three types of stacks were found for 3-tolyl (CC=6.153 Å), 4-tolyl (CC=3.849 Å) and 2,4-xylyl (CC=4.856 Å) derivatives by single crystal X-ray diffractometry. All six derivatives show intense solution fluorescence in blue/green region, with a maximum driven entirely by a number and position of methyl substituents on phenyl rings. On the other hand, the solid-state fluorescence from yellow over orange to red is observed only for four derivatives and its presence/absence, spectral position and vibronic structure is driven exclusively by the slips in π-stacks (with interplanar distance always less than 3.5 Å) of almost planar DFF molecules, resulting in J-type emission, H-type excimer-like emission and H-type quenching.

1,2,4-Triazole-Ligand-based Iridium(III) complex and its use in blue phosphorescent organic light-emitting diodes

Organic light-emitting diodes (OLEDs) play a key role in modern flexible displays. Although stable and efficient red- and green-emitting phosphors have been developed, the applications of blue emitters are limited due to their poor chemical and electrochemical stability, and thus, they require further development. Herein, we report the preparation and full characterization of IrTrz, a 3-methyl-5-phenyl-1H-1,2,4-triazole-ligand-based facial-homoleptic iridium complex. Single-crystal X-ray diffractometry results suggested that the complex is a facial isomer with C3 point symmetry. The complex exhibited a blue emission band centered at ∼450 nm in both solution and the film state at ambient temperature; moreover, it showed a very narrow full-width at half maximum value (55 nm) and a moderate photoluminescence quantum yield (33%). The complex showed high thermal stability, with 5%-weight-loss and glass-transition temperatures of 324 and 210 °C, respectively. Consecutive cyclic voltammetry measurements revealed outstanding electrochemical stability of the complex. Therefore, multilayer phosphorescent OLEDs that use IrTrz as the blue emitter were fabricated with two types of host material: (3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (mCBP) and 9-(dibenzo[b,d]thiophen-4-yl)-9H-3,9′-bicarbazole (4DBTCz)). In particular, the 4DBTCz-based devices exhibited low turn-on voltages (∼5.0 V) and high external quantum efficiencies (>11%) with a Commission Internationale de l’Eclairage y-coordinate of 0.2. Moreover, the devices demonstrated stable operational lifetimes that exceeded 690 h (for mCBP) and 390 h (for 4DBTCz) at 100 cd/m2. Therefore, we believe that the 1,2,4-triazole-ligand-based Ir(III) complex is a promising blue-phosphorescent emitter material for applications in stable and efficient OLED devices.

Improvement in Radiative Efficiency Via Intramolecular Charge Transfer in ortho-Carboranyl Luminophores Modified with Functionalized Biphenyls.

In this study, we found that the electronic effects of the functional groups on aromatic units attached to o-carboranyl species can enhance the efficiency of intramolecular charge transfer (ICT)-based radiative decay processes. Six o-carboranyl-based luminophores having attached functionalized biphenyl groups with CF3, F, H, CH3, C(CH3)3, and OCH3 substituents were prepared and fully characterized by multinuclear magnetic resonance spectroscopy. In addition, their molecular structures were determined by single-crystal X-ray diffractometry, which revealed that the distortion of the biphenyl rings and the geometries around the o-carborane cages were similar. All compounds exhibited ICT-based emissions in the rigid state (solution at 77 K and film). Intriguingly, the quantum efficiencies (Φem) of five compounds (that of the group with CF3 could not be measured because of its extremely weak emissions) in the film state increased gradually as the electron-donating power of the terminal functional group modifying the biphenyl moiety increased. Furthermore, the nonradiative decay constants (knr) for the group with OCH3 were estimated to be one-tenth of those for the group with F, whereas the radiative decay constants (kr) for the five compounds were similar. The dipole moments (μ) calculated for the optimized first excited state (S1) structures gradually increased, from that of the group with CF3 to that of the group with OCH3, implying that the inhomogeneity of the molecular charge distribution was enhanced by electron donation. The electron-rich environment formed as a result of electron donation led to efficient charge transfer to the excited state. Both experimental and theoretical findings revealed that the electronic environment of the aromatic moiety in o-carboranyl luminophores can be controlled to accelerate or interrupt the ICT process in the radiative decay of excited states.

Imidazole-Based Metal–Organic Framework for the “On1–Off–On2” Fluorescence-Based Detection of Picric Acid and the Adsorption of Congo Red

An imidazole-functionalized metal–organic framework (MOF), {[Ba2L (H3CCOO) (DMF)2] (DMF)}n, denoted as HBU-168, has been synthesized and characterized by single-crystal X-ray diffractometry. The synthesized MOF exhibits ligand-based luminescence, which can be attributed to coordination effects. Due to its excellent fluorescence performance, HBU-168 can be used to detect nitroaromatic compounds (NACs) and metal ions selectively and sensitively. The most striking properties of HBU-168 are the distinct red shift (∼34.8 nm) observed in the presence of picric acid (PA) with a Stern–Volmer constant (KSV) of 4.17 × 104. The mechanism of the change in luminescence in the presence of PA is determined by experiments and density functional theory calculations. The results indicate that the electron transfer between PA and the MOF has a reduction in the frontier orbital energy gap. Subsequently, HBU-168 is used to prepare a light-emitting-diode-based sensor (denoted HBU-168-LED), which can detect PA rapidly and visually. In addition, we find that HBU-168 can be used to detect metal ions, particularly magnesium ions. The metal detection mechanism is based on the turn-on fluorescence of HBU-168 caused by weak interactions between the MOF and metal ions. Finally, HBU-168 is found to be a good adsorbent for Congo red, achieving a removal efficiency of 98.89%. Therefore, the multifunctional HBU-168 MOF is a promising luminescent sensor and adsorbent.

1D Supramolecular Assemblies That Crystallize and Form Gels in Response to the Shape-Complementarity of Alcohols.

N-9-Fluorenylmethyloxycarbonyl (Fmoc)- and C-tertiary butyl (t-Bu)-protected glutamate (L-2), bearing a phenanthroline moiety at the side residue, forms 1D supramolecular assemblies via H-bonding as well as undergoing π-stacking interactions to afford crystals or gels that depend on the shape-complementarity of coexisting alcohols, as demonstrated by structural analyses on these assemblies by means of single-crystal X-ray diffractometry and supplemented with small- and wide-angle X-ray scattering data. Moreover, the rheological measurements on the gels help to define a model for when gels and crystals are expected and found. These observations and conclusions highlight an important, but not very appreciated, aspect of solute-solvent interactions within supramolecular assemblies that can allow the constituent-aggregating molecules in some systems to exhibit high selectivity toward the structures of their solvents. The consequences of this selectivity, as demonstrated here by single-crystal and powder X-ray diffraction data, can lead to self-assembled structures which alter completely the bulk phase properties and morphology of the materials. In that regard, rheological measurements have helped to develop a model to explain when gels and phase-separated mixtures of crystals and solvents are expected.