Search

Abstract: Ruthenium‐containing organometallic ionic liquids with the B(CN)4 anion were developed that generate microporous amorphous coordination polymers upon UV irradiation. UV light irradiation of [Ru(C5H5)(C6H5R)][B(CN)4] (R=butyl, ethyl, octyl) quantitatively generated a yellow powder of a coordination polymer with the formula [Ru(C5H5){B(CN)4}]n. In this reaction, the arene ligand is eliminated by UV irradiation and coordination polymer is formed by coordination of the cyano groups of the anion to the Ru ion. The photogenerated solids exhibited nitrogen absorption properties due to their microporous structure. This paper proposes a method to fabricate functional coordination polymers by photoirradiation of liquids. [ABSTRACT FROM AUTHOR]

Nucleophilic substitution of [(η5‐cyclopentadienyl)(η6‐chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η5‐cyclopentadienyl)(η6‐phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η5‐1,2,3,4,5‐pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η5‐cyclopentadienyl)(η6‐phenyl)iron(II)]+ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X‐ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η5‐cyclopentadienyl)(η6‐phenyl)iron(II)]+ unit at the NHC ligand. [ABSTRACT FROM AUTHOR]

Chiral magnetic materials are proposed for applications in second‐order non‐linear optics, magneto‐chiral dichroism, among others. Recently, we have reported a set of tetra‐nuclear Fe(II) grid complex conformers with general formula C/S‐[Fe4L4]8+ (L: 2,6‐bis(6‐(pyrazol‐1‐yl)pyridin‐2‐yl)‐1,5‐dihydrobenzo[1,2‐d : 4,5‐d′]diimidazole). In the grid complexes, isomerism emerges from tautomerism and conformational isomerism of the ligand L, and the S‐type grid complex is chiral, which originates from different non‐centrosymmetric spatial organization of the trans type ligand around the Fe(II) center. However, the selective preparation of an enantiomerically pure grid complex in a controlled manner is difficult due to spontaneous self‐assembly. To achieve the pre‐synthesis programmable resolution of Fe(II) grid complexes, we designed and synthesized two novel intrinsically chiral ligands by appending chiral moieties to the parent ligand. The complexation of these chiral ligands with Fe(II) salt resulted in the formation of enantiomerically pure Fe(II) grid complexes, as unambiguously elucidated by CD and XRD studies. The enantiomeric complexes exhibited similar gradual and half‐complete thermal and photo‐induced SCO characteristics. The good agreement between the experimentally obtained and calculated CD spectra further supports the enantiomeric purity of the complexes and even the magnetic studies. The chiral resolution of Fe(II)‐ [2×2] grid complexes reported in this study, for the first time, might enable the fabrication of magneto‐chiral molecular devices. [ABSTRACT FROM AUTHOR]

An easily synthesized fluorescein-based luminescent dye has been utilized for the dual-mode detection of histamine at nanomolar concentrations at pH 7.0 in water. The specific response to histamine was achieved by imidazole-catalyzed 'imine formation' reaction. The protocol was subsequently applied for the estimation of histamine in complex biological milieu such as human blood serum and urine samples. Furthermore, the dose-dependent cellular uptake of histamine and de novo synthesis (by thapsigargin treatment) was visualized in RAW 264.7, a mouse macrophage cell line. We have also developed portable paper strips for rapid, on-site detection of histamine without involving costly instruments. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen activation/reduction processes as an alternative to noble‐metal‐Pt‐based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio‐inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20‐tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs' surface. The catalysts' electrocatalytic activity varied with the axial coordination environment (i. e. S‐thiophene, N‐imidazole, and O‐carboxylate); the imidazole‐coordinated catalyst MWCNTs‐Im‐FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT‐Im‐FeF20TPP was loaded onto the cathode of a zinc−air battery, an open‐cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs‐Thi‐FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs‐Ox‐FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time‐saving method to prepare covalently immobilized molecular electrocatalysts on carbon‐based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion. [ABSTRACT FROM AUTHOR]

Wrinkles and photo‐oxidation reactions are widely found in soft materials, which are intimately associated with the failure of materials and structures. It is expected that the photo‐oxidation process could also have a positive effect on the material and its surface. Here, we report the photo‐oxidation of 2‐(4‐dietheylaminophenyl)‐4,5‐bis(4‐methoxyphenyl) imidazole (DEA‐TAI) into a wrinkled bilayer system to control surface wrinkle and fluorescent patterns, in which a supramolecular polymer network composed of carboxylic acid‐containing copolymer (PS‐BA‐AA; PS=poly(styrene), BA=butyl acrylate; AA=acrylic acid) and DEA‐TAI were used as the skin layer. Ultraviolet (UV) irradiation can induce photo‐oxidation of the imidazole ring of DEA‐TAI to weaken the intermolecular hydrogen bonding between PS‐BA‐AA and DEA‐TAI, resulting in the release of stress in the bilayer system. The wrinkled morphology and fluorescence of the surface can be simultaneously regulated by photo‐oxidation of DEA‐TAI under UV light, and the resulting wrinkles are extremely sensitive to the pH value, which can be quickly and reversibly erased by NH3 gas. Smart surfaces with specific hierarchical wrinkles and fluorescence can be achieved by selective irradiation with photomasks, which may find potential applications in smart displays and multi‐code information storage. [ABSTRACT FROM AUTHOR]

This paper deals with a systematic density functional theory (DFT) study aiming to unravel the mechanism of the thyroxine (T4) conversion into 3,3′,5-triiodothyronine (rT3) by using different bio-inspired naphthyl-based models, which are able to reproduce the catalytic functions of the type-3 deiodinase ID-3. Such naphthalenes, having two selenols, two thiols, and a selenol-thiol pair in peri positions, which were previously synthesized and tested in their deiodinase activity, are able to remove iodine selectively from the inner ring of T4 to produce rT3. Calculations were performed including also an imidazole ring that, mimicking the role of the His residue, plays an essential role deprotonating the selenol/thiol moiety. For all the used complexes, the calculated potential energy surfaces show that the reaction proceeds via an intermediate, characterized by the presence of a XIC (X=Se, S) halogen bond, whose transformation into a subsequent intermediate in which the CI bond is definitively cleaved and the incipient XI bond is formed represents the rate-determining step of the whole process. The calculated trend in the barrier heights of the corresponding transition states allows us to rationalize the experimentally observed superior deiodinase activity of the naphthyl-based compound with two selenol groups. The role of the peri interactions between chalcogen atoms appears to be less prominent in determining the deiodination activity. [ABSTRACT FROM AUTHOR]

Sustainable ionic liquids are promising compounds in green chemistry applications. While using them as solvent or reaction media is an important step towards more environmentally friendly chemistry, their synthesis is usually expensive and not green at all. Herein, a benign route to synthesize task ‐ specific ionic liquids is presented, offering several possible functionalities in the cation and anion (artwork by D. Kraban). More information can be found in the Full Paper by C. Liedel et al. on page 11810. [ABSTRACT FROM AUTHOR]

The X‐ray study on a single crystal of the butterfly‐like complex [{Pt(C^C*)(μ‐pz)}2] (1), containing a cyclometalated N‐heterocyclic carbene ligand as wings (HC^C*=1‐(4‐(ethoxycarbonyl)phenyl)‐3‐methyl‐1H‐imidazol‐2‐ylidene), showed three molecules in the asymmetric unit with intermetallic separations (Å) of 3.2294(4) (1A), 3.2834(4) (1B), and 3.1208(6) (1C). From the reaction of 1 with excess of CHI3 in the air and the sunlight, complex [{Pt(C^C*)(μ‐pz)I)}2] (2) (dPt−Pt=2.6079(2) Å) was obtained as the major product, while [IPt(C^C*)(μ‐pz)2Pt(C^C*)CHI2] (3) (dPt−Pt=2.6324(3) Å) was obtained as the major product under argon atmosphere in the dark. Experimental and theoretical investigations showed that an easily accessible radical‐like mechanism operates under thermal conditions, with dioxygen acting as an efficient radical (R.) scavenger. The oxidation of a Pt2(II,II) "butterfly" by CHI3 to give metal−metal bonded Pt2(III,III) compounds is described now for the first time. [{Pt(C^C*)(μ‐pz)}2] is the first "platinum‐butterfly" with a cyclometalated N‐heterocyclic carbene (C^C*) acting as wings, that has ever been oxidized by halocarbons. The control of the reaction conditions allowed to get almost selectively [{Pt(C^C*)(μ‐pz)I)}2] or [IPt(C^C*)(μ‐pz)2Pt(C^C*)CHI2] which were fully characterized. Experimental and theoretical investigations showed that an easily accessible radical‐like mechanism operates under thermal conditions. [ABSTRACT FROM AUTHOR]

The design, synthesis, and characterization of a new multifunctional supramolecular assembly based on a photoactive glycosylated porphyrin and covalently attached monofunctionalized cucurbit[7]uril (CB7) are reported. To obtain the target supramolecular assembly, azido‐functionalized tetraphenylporphyrin (TPP) was used as a building block. TPP was first glycosylated by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction, then a monopropargyloxy‐functionalized‐CB7 unit was conjugated to glycosylated TPP with a second CuAAC reaction. The host–guest chemistry of the assembly was investigated by 1H NMR experiments to establish the availability of the CB7 as a host. The imidazole‐based guest, which is known to have high affinity toward CB7, was observed to form inclusion complex with CB7. It was also demonstrated that this supramolecular assembly can serve as an efficient photosensitizer for the generation of singlet oxygen. Sugar‐coated assemblies: A new multifunctional supramolecular assembly was synthesized by clicking an azide functionalized photoactive glycosylated porphyrin with monopropargyloxy functionalized cucurbit[7]uril (CB7). This supramolecular assembly can serve as a host to bind with guests and an efficient photosensitizer for the generation of singlet oxygen (see figure). [ABSTRACT FROM AUTHOR]

Organocatalytic asymmetric transformation of common aromatic heterocycles via in situ formation of highly reactive dearomatized ortho‐quinodimethane diene species and subsequent [4+2] cycloaddition with suitable dienophiles has become a powerful tool to enter cyclohexane‐fused heterocycles. Most of these reactions were previously applied to benzo‐fused heterocycles or poorly aromatic rings. Herein, we disclose how previously intractable aromatic imidazole rings, equipped with removable methylidene malononitrile activating handle, could be involved as competent cycloaddends with β‐aryl enals in efficient eliminative [4+2] cycloadditions under mild organocatalytic conditions. This method allowed the efficient and direct preparation of scantly represented 6,7‐dihydrobenzo[d]imidazoles with optimal enantio‐ and regioselectivities. Post‐cycloaddition chemical editing provided imidazole‐based ring systems with diverse oxidation state and functional groups. [ABSTRACT FROM AUTHOR]

Diimidazolium-based organic salts, bearing peptides or amino acids as anions have been synthesised and tested for their gelling ability in biocompatible solvents. These low molecular weight salts were successfully used as gelators in phosphate buffered saline (PBS) solution and ionic liquids. Then, the properties of the obtained soft materials were analysed in terms of melting temperature and gel strength as accounted for by rheological investigations. The gel-phase formation was studied by using UV/Vis and resonance light scattering measurements, whereas the morphology of the soft materials was analysed by using polarised optical microscopy and scanning electron microscopy. To get information about the organisation of the gelator in the gelatinous matrix, X-ray diffraction measurements were performed both on the neat gelators and their gels. The results collected show that the properties of the gel phases, like the thermal stability, the self-repairing ability, the resistance to flow as well as the morphology, are dependent on the nature of the anion. Furthermore, bioassays revealed that the obtained diimidazolium organic salts possessed antimicrobial activity, against gram-negative and gram-positive tester strains. In particular and noteworthy, the diimidazolium organic salts exert a bactericidal capability, which was retained even if they are included in the gel phase. Thus, a novel kind of bioactive soft material was obtained that could be fruitfully employed as a non-covalent coating exerting antibacterial capability. [ABSTRACT FROM AUTHOR]

Glucose regulated protein 94 (Grp94) is the endoplasmic reticulum (ER) resident isoform of the 90 kDa heat shock protein (Hsp90) family and its inhibition represents a promising therapeutic target for the treatment of many diseases. Modification of the first generation cis-amide bioisostere imidazole to alter the angle between the resorcinol ring and the benzyl side chain via cis-amide replacements produced compounds with improved Grp94 affinity and selectivity. Structure-activity relationship studies led to the discovery of compound 30, which exhibits 540 n m affinity and 73-fold selectivity towards Grp94. Grp94 is responsible for the maturation and trafficking of proteins associated with cell signaling and motility, including select integrins. The Grp94-selective inhibitor 30 was shown to exhibit potent anti-migratory effects against multiple aggressive and metastatic cancers. [ABSTRACT FROM AUTHOR]

Starting from 2,4-dichloropyrimidine, 4-(2-dialkylamino)pyrimidinyl functionalized mesitylimidazolium chlorides are accessible in a five-step reaction sequence. Two routes leading to palladium NHC complexes derived from these ligands have been worked out: By transmetalation with the corresponding NHC-AgCl complexes, C,N-coordinated palladium(II) complexes can be obtained. Treatment of palladium dichloride with the imidazolium salts in pyridine and in the presence of K2CO3 gives cyclometalated and thus C,C-coordinated compounds. The reactivities of all these compounds were investigated in detail as well as their performance in the catalytic Suzuki-Miyaura cross-coupling reaction. It turned out that the C,C-coordinated derivatives exhibit high catalytic activities in the coupling of arylboronic acids with aryl chlorides, which is consistent with the generally accepted mechanistic ideas on substrate activation. [ABSTRACT FROM AUTHOR]

Recently, the fields of organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs) have improved tremendously with regard to tunable emission, efficiency, brightness, and thermal stability. Imidazole derivatives are excellent deep blue‐green light‐emitting layers in the OLED or LEC devices. This Review summarizes the major breakthroughs of various electroluminescence (EL) layers with imidazole‐containing organic or organometallic derivatives, the molecular design principles, and their light‐emitting performances as effective EL materials. The highly tunable chemical structures and flexible molecular design strategies of imidazole‐based compounds are advantages that provide great opportunities for researchers. They can provide a good basis for the design and development of new EL materials with narrower emission and higher efficiency. Moreover, imidazole compounds have demonstrated breakthrough performances in thermally activated delayed fluorescence (TADF) properties where triplet excitons are utilized to inhibit anti‐intersystem quenching, showing great promise in breaking the theoretical external quantum efficiencies (EQE) limits in traditional fluorescent devices. [ABSTRACT FROM AUTHOR]

The carbon allotrope exhibiting only one-dimensional sp-hybridized carbon atoms is called carbyne. However, its existence is very controversial. Studies on model compounds for carbyne revealed that many oligoalkynes show not a straight, but a bent structure of the carbon chain. Here, we question whether it would also be possible to obtain a more complex structure from carbyne, such as a dimeric double helix. Based on quantum chemical calculations, we show that only a small energetic expense is needed for the formation of a double helix starting from oligoalkyne chains. In some cases, the double helix-like conformation is more stable than the corresponding conformation with a parallel arrangement of the acetylene chains. Furthermore, model systems were synthesized in which two diphenyl oligoalkyne chains are fixed and twisted by a chiral imidazole-containing clamp. A structural investigation of these model systems was performed based on UV and CD spectroscopy and quantum chemical calculations. The observed twisting in these model systems can be regarded as the first small step towards an imaginable carbon double helix. [ABSTRACT FROM AUTHOR]

We report the synthesis of task-specific imidazolium ionic compounds and ionic liquids with key functionalities of organic molecules from electro-, polymer-, and coordination chemistry. Such products are highly functional and potentially suitable for technology applications even though they are formed without elaborate reactions and from cheap and potentially green reagents. We further demonstrate the versatility of the used synthetic approach by introducing different functional and green counterions to the formed ionic liquids directly during the synthesis or after metathesis reactions. The influence of different cation structures and different anions on the thermal and electrochemical properties of the resulting ionic liquids is discussed. Our goal is to make progress towards economically competitive and sustainable task-specific ionic liquids. [ABSTRACT FROM AUTHOR]

The synthesis of metal-organic framework (MOF) thin films has garnered significant attention during the past decade. By better understanding the parameters governing the nucleation and growth of such thin films, their properties can be rationally tuned, empowering their application as (reactive) membranes. Here, a combined AFM-vibrational spectroscopy research strategy is employed to detail the chemistries governing the nucleation and growth of zeolitic imidazolate framework (ZIF) thin films, in particular isostructural Co-ZIF-67 and Zn-ZIF-8. First, a single step direct synthesis approach is used to investigate the influence of different synthesis parameters -metal/linker ratio, temperature, and metal type- on the thin film nucleation and growth behaviour. While the metal/linker ratio has a pronounced effect on the thin film nucleation rate, the temperature mainly influences the growth kinetics of nuclei forming the thin film. In addition, the nucleation and growth of ZIF thin films is shown to be highly dependent on the electronegativity of the metal type. Thin-film thickness control can be achieved by using a multistep synthesis strategy, implying repetitive applications of single step deposition under identical synthesis conditions, for which a growth mechanism is proposed. This study provides insight into the influence of synthesis parameters on the ZIF thin film properties, using tools at hand to rationally tune MOF thin film properties. [ABSTRACT FROM AUTHOR]

Starting from DMSAuCl, isonitriles and functionalized propargylammonium salts in the presence of simple trimethylamine as auxiliary base, unsymmetrically substituted ester- and phosphonate-functionalized AuI-imidazolylidene complexes were synthesized in an easy-to-use modular one-pot template synthesis. In the course of the reaction, after the initial nucleophilic addition of the amine to the gold(I)-activated isonitrile, a Michael addition closes the N-heterocyclic carbene (NHC) ring. Then the remaining double bond migrates into the NHC ring, evidently a more stable position than the initial exocyclic double bond. These functional groups attached to the back bone of the NHC ligands represent ideal handles for a further modification of the system, for example an attachment to larger assemblies or heterogenization by an attachment to surfaces are conceivable. [ABSTRACT FROM AUTHOR]

The proton-coupled electron-transfer (PCET) reaction is investigated for a newly synthesized imidazole-anthraquinone biomimetic model with a photoactive RuII-polypyridyl moiety that is covalently coupled to the imidazole fragment. Intramolecular H-bonding interactions between imidazole and anthraquinone moieties favor the PCET process; this can be correlated to an appreciable positive shift in the one-electron reduction potential of the coordinated anthraquinone moiety functionalized with the imidazole fragment. This can also be attributed to the low luminescence quantum yield of the RuII-polypyridyl complex used. The dynamics of the intramolecular electron-transfer (ET) and PCET processes are studied by using femtosecond transient absorption spectroscopy. The steady-state spectroscopic studies and the results of the time-resolved absorption studies confirm that H-bonded water molecules play a major role in both ET and PCET dynamics as a proton relay in the excited state. The electron-transfer process is followed by a change in the H-bonding equilibrium between AQ and imidazole in acetonitrile solvent, and protonation of AQ.− by water leads to PCET in the presence of water. A slower forward and backward electron-transfer rate is observed in the presence of D2O compared with that in H2O. These results provide further experimental support for a detailed understanding of the PCET process. [ABSTRACT FROM AUTHOR]

Depending on the amount of methanol present in solution, CO2 adducts of N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) have been found to be in fully reversible equilibrium with the corresponding methyl carbonate salts [EMIm][OCO2Me] and [EMMIm][OCO2Me]. The reactivity pattern of representative 1-ethyl-3-methyl-NHO-CO2 adduct 4 has been investigated and compared with the corresponding NHC-CO2 zwitterion: The protonation of 4 with HX led to the imidazolium salts [NHO-CO2H][X], which underwent decarboxylation to [EMMIm][X] in the presence of nucleophilic catalysts. NHO-CO2 zwitterion 4 can act as an efficient carboxylating agent towards CH acids such as acetonitrile. The [EMMIm] cyanoacetate and [EMMIm]2 cyanomalonate salts formed exemplify the first C−C bond-forming carboxylation reactions with NHO-activated CO2. The reaction of the free NHO with dimethyl carbonate selectively led to methoxycarbonylated NHO, which is a perfect precursor for the synthesis of functionalized ILs [NHO-CO2Me][X]. The first NHO-SO2 adduct was synthesized and structurally characterized; it showed a similar reactivity pattern, which allowed the synthesis of imidazolium methyl sulfites upon reaction with methanol. [ABSTRACT FROM AUTHOR]

Imidazole (IMZ) rings catalyze many biological dephosphorylation processes. The methyl positioning effect on IMZs reactivity has long intrigued scientists and its full understanding comprises a promising tool for designing highly efficient IMZ-based catalysts. We evaluated all monosubstituted methylimidazoles (xMEI) in the reaction with diethyl 2,4-dinitrophenyl phosphate by kinetics studies, NMR analysis and DFT calculations. All xMEI showed remarkable rate enhancements, up to 1.9×105 fold, compared with spontaneous hydrolysis. Unexpectedly, the electron-donating methyl group acts to decrease the reactivity of the xMEI compared to IMZ, except for 4(5)methylimidazole, (4(5)MEI). This behavior was attributed to both electronic and steric effects. Moreover, reaction intermediates were monitored by NMR and surprisingly, the reactivity of the two different 4(5)MEI tautomers was distinguished. [ABSTRACT FROM AUTHOR]

Three donor‐acceptor compounds based on the imidazo‐pyrazine‐5,6‐dicarbonitrile (IPDC) acceptor were synthesized. The IPDC emitters exhibit blue to near‐infrared (NIR) emission with up to 54 % photoluminescent quantum yield. 9,9‐Dimethyl‐9,10‐dihydroacridine (ACR), phenoxazine (POX), and phenothiazine (PTZ) served as electron donors. IPDC‐POX displayed NIR emission in toluene solution, while showing room‐temperature phosphorescence in the solid state. IPDC‐ACR exhibited yellow thermally activated delayed fluorescence. Interestingly, dual‐emissive behavior as well as excitation‐dependent thermally activated delayed fluorescence (TADF) was found for IPDC‐PTZ, arising from the two conformers of phenothiazine derivatives. Overall, this work describes a novel strong electron acceptor from the fusion of imidazole, pyrazine, and nitrile functional groups into one conjugated heterocycle for materials exhibiting NIR emission, TADF, and/or room‐temperature phosphorescence (RTP). [ABSTRACT FROM AUTHOR]

Considering the difficulties associated with the conventional 'trial and error' method for a complete analysis of a giant molecular space, we took the aid of computational pathway (DFT) in screening a large space search of 780 (12×13×5) molecules to search for a host for the blue emitter. The selection process was completed in three Tiers with the conditions of highest theoretical triplet energy (>2.81 eV), aligned HOMO/LUMO levels w.r.t blue dopant (FIrpic), and position of substituents to meet the optimal requirements as host materials. Tier 1 screened twelve different imidazole heterocycle derivatives as base space groups which resulted in the selection of 4,5‐diphenyl‐1H‐imidazole. Tier 2 process converged the search to mCN‐CZ having the highest triplet energy and appropriate HOMO/LUMO level relative to FIrpic and ETL. Further, the carbazole of mCN‐CZ was replaced with different aromatic hydrocarbons to find the other best compound in terms of triplet energy and HOMO/LUMO. Tier 3 resulted in another promising candidate (mCN‐FL) as possible host materials. The band alignment with guest predicted mCN‐FL and mCN‐CZ to have optimal device performances compared to CZ‐CZ and the experimentally observed device performance was in accordance with virtual screening results when TAPC was utilized as the hole transporter. The device results of mCN‐CZ and mCN‐FL were better than the reference host TCTA. The obtained results thus proved that a virtual screening process will be a useful tool for synthetic chemists in designing task‐specific materials. [ABSTRACT FROM AUTHOR]

Isonitrile 1 due to its carbene-like reactivity serves generally as a one-carbon synthon in a diverse set of organic transformations. We report in this article that the isocyano group can also act as a polarized triple bond to undergo, as a two-atom synthon, heteroannulation with primary propargylamines 15. In addition, we serendipitously discovered that the reaction pathways can be modulated by simply changing the catalyst loading. In the presence of 0.1 equiv of Yb(OTf)3 or TfOH, the reaction between 1 and 15 afforded exclusively imidazoles 16 by a formal [3+2] cycloaddition. At a higher catalyst loading (Yb(OTf)3 (0.4 equiv) or TfOH (0.5 equiv)) under otherwise identical conditions, the same reaction furnished 1,6-dihydropyrimidines 17 in good to excellent yields by way of a formal [4+2] cycloaddition process. Mechanistic investigations indicated that both annulations went through an amidine intermediate resulting from the insertion of the isocyano group to the NH bond of the primary amine. Subsequent catalyst-loading-dependent 5- exo-dig or 6- endo-dig cyclization provided selectively the two heterocycles, respectively. [ABSTRACT FROM AUTHOR]

Large-pore microporous materials are of great interest to process bulky hydrocarbon and biomass-derived molecules. ITQ-27 (IWV) has a two-dimensional pore system bounded by 12-membered rings (MRs) that lead to internal cross-sections containing 14 MRs. Investigations into the catalytic behavior of aluminosilicate (zeolite) materials with this framework structure have been limited until now due to barriers in synthesis. The facile synthesis of aluminosilicate IWV in both hydroxide and fluoride media is reported herein using simple, diquaternary organic structure-directing agents (OSDAs) that are based on tetramethylimidazole. In hydroxide media, a zeolite product with Si/Al=14.8-23.2 is obtained, while in fluoride media an aluminosilicate product with Si/Al up to 82 is synthesized. The material produced in hydroxide media is tested for the hydroisomerization of n-hexane, and results from this test reaction suggest that the effective pore size of zeolites with the IWV framework structure is similar to but slightly larger than that of ZSM-12 (MTW), in fairly good agreement with crystallographic data. [ABSTRACT FROM AUTHOR]

Through the use of a fully C/N-functionalized imidazole-based anion, it was possible to prepare nitrogen- and oxygen-rich energetic salts. When N, N-dinitramino imidazole was paired with nitrogen-rich bases, versatile ionic derivatives were prepared and fully characterized by IR, and 1H, and 13C NMR spectroscopy and elemental analysis. Both experimental and theoretical evaluations show promising properties for these energetic compounds, such as high density, positive heats of formation, good oxygen balance, and acceptable stabilities. The energetic salts exhibit promising energetic performance comparable to the benchmark explosive RDX (1,3,5-trinitrotriazacyclohexane). [ABSTRACT FROM AUTHOR]

A new H‐bonded crystal [RuIII(Him)3(Im)3] with three imidazole (Him) and three imidazolate (Im−) groups was prepared to obtain a higher‐temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H‐bonds between the RuIII complexes and has a rare Icy‐c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10−5 S cm−1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole‐molecule rotation of [RuIII(Him)3(Im)3] at temperatures greater than 420 K. The latter rotation was confirmed by solid‐state 2H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered. [ABSTRACT FROM AUTHOR]

The 1‐methyl‐3‐(tricyanoborane)imidazolin‐2‐ylidenate anion (2) was obtained in high yield by deprotonation of the B(CN)3‐methylimidazole adduct 1. Regarding charge and stereo‐electronic properties, anion 2 closes the gap between well‐known neutral NHCs and the ditopic dianionic NHC, the 1,3‐bis(tricyanoborane)imidazolin‐2‐ylidenate dianion (IIb). The influence of the number of N‐bonded tricyanoborane moieties on the σ‐donating and π‐accepting properties of NHCs was assessed by quantum chemical calculations and verified by experimental data on 2, IIb, and 1,3‐dimethylimidazolin‐2‐ylidene (IMe, IIa). Therefore NHC 2, which acts as a ditopic ligand via the carbene center and the cyano groups, was reacted with alkyl iodides, selenium, and [Ni(CO)4] yielding alkylated imidazoles 3 and 4, the anionic selenium adduct 5, and the anionic nickel tricarbonyl complex 8, respectively. The results of this study prove that charge, number of coordination sites, buried volume (%Vbur) and σ‐donor and π‐acceptor abilities of NHCs can be effectively fine‐tuned via the number of tricyanoborane substituents. [ABSTRACT FROM AUTHOR]

NHC-B,N-heterocyclic compounds have been found to act as convenient precursors for obtaining either 1,3-azaborinine or 1 H-imidazo[1,2-a]indole derivatives, which are two different and rare classes of compounds. The formation of these two classes of compounds from the NHC-B,N-heterocycles is highly selective depending on the external stimuli employed, and the resulting products have been studied for their interesting chemical and photophysical properties. The mechanism and possible reaction pathways of the unusual transformation are established by computational studies. [ABSTRACT FROM AUTHOR]

Diphenylphosphinoethyl-functionalised imidazolium salts and their silver-carbene complexes were used to synthesise a series of di- and trinuclear gold complexes through ligand exchange and transmetallation, respectively. Besides a few positively charged macrocyclic compounds with different anions (both with and without activation of the carbene function), we were able to obtain neutral polynuclear complexes by varying the gold precursor. The synthesised gold complexes show a variety of photophysical properties, including bright white photoluminescence at ambient temperature. [ABSTRACT FROM AUTHOR]

N-Ylide complexes of Ir have been generated by C(sp3)H activation of α-pyridinium or α-imidazolium esters in reactions with [Cp*IrCl2]2 and NaOAc. These reactions are rare examples of C(sp3)H activation without a covalent directing group, which-even more unusually-occur α to a carbonyl group. For the reaction of the α-imidazolium ester [ 3H]Cl, the site selectivity of CH activation could be controlled by the choice of metal and ligand: with [Cp*IrCl2]2 and NaOAc, C(sp3)H activation gave the N-ylide complex 4; in contrast, with Ag2O followed by [Cp*IrCl2]2, C(sp2)H activation gave the N-heterocyclic carbene complex 5. DFT calculations revealed that the N-ylide complex 4 was the kinetic product of an ambiphilic CH activation. Examination of the computed transition state for the reaction to give 4 indicated that unlike in related reactions, the acetate ligand appears to play the dominant role in CH bond cleavage. [ABSTRACT FROM AUTHOR]

The first RhI‐catalyzed, directed decarbonylative C2−H alkenylation of imidazoles with readily available alkenyl carboxylic acids is reported. The reaction proceeds in a highly regio‐ and stereoselective manner, providing efficient access to C2‐alkenylated imidazoles that are generally inaccessible by known C−H alkenylation methods. This transformation accommodates a wide range of alkenyl carboxylic acids, including challenging conjugated polyene carboxylic acids, and diversely decorated imidazoles with high functional group compatibility. The presence of a removable pyrimidine directing group and the use of a bidentate phosphine ligand are pivotal to the success of the catalytic reaction. This process is also suitable for benzimidazoles. Importantly, the scalability and diversification of the products highlight the potential of this protocol in practical applications. Detailed experimental and computational studies provide important insights into the underlying reaction mechanism. [ABSTRACT FROM AUTHOR]

In this Concept article we provide a brief overview of the design and preparation of N‐heterocyclic carbenes carrying weakly coordinating anions (WCA‐NHCs). The anionic charge in these ligand systems is located on an exocyclic group, for example, B(C6F5)3, tethered to the backbone of the imidazole ring, thus resembling a weakly coordinating moiety. With the general guiding principle behind the application of WCA‐NHCs being the conversion of otherwise cationic NHC complexes into their overall neutral congeners, numerous transition metal as well as main group element complexes were isolated during the last decade, which are summarized herein. [ABSTRACT FROM AUTHOR]

Ruthenium dyes incorporating a 4 H-imidazole chromophore as a ligand exhibit a spectrally broad absorption in the UV/Vis region. Furthermore, they show the ability to store two electrons within the 4 H-imidazole ligand. These features render them promising molecular systems, for example, as inter- or intramolecular electron relays. To optimize the structures with respect to their electron-storage capability, it is crucial to understand the impact of structural changes accompanying photoinduced charge transfer in the electronic intermediates of multistep electron-transfer processes. The photophysical properties of these (reactive) intermediates might impact the function of the molecular systems quite substantially. However, the spectroscopic study of short-lived intermediates in stepwise multielectron-transfer processes is experimentally challenging. To this end, this contribution reports on the electrochemical generation of anions identical to intermediate structures and their spectroscopic characterization by in situ resonance Raman and UV/Vis spectroelectrochemistry and computational methods. Thereby, an efficient two-electron pathway to the 4 H-imidazole electron-accepting ligand is identified. [ABSTRACT FROM AUTHOR]

Fused-imidazoles, Groebke-Blackburn-Bienaymé (GBB) reaction, Isocyanide Chemistry, Multicomponent reactions, [2.2]Paracyclophane Cover Feature: Diversity-Oriented Synthesis of [2.2]Paracyclophane-derived Fused Imidazo[1,2-a]heterocycles by Groebke-Blackburn-Bienaymé Reaction: Accessing Cyclophanyl Imidazole Ligands Library (Chem. Eur. J. 3/2022) Keywords: Fused-imidazoles; Groebke-Blackburn-Bienaymé (GBB) reaction; Isocyanide Chemistry; Multicomponent reactions; [2.2]Paracyclophane EN Fused-imidazoles Groebke-Blackburn-Bienaymé (GBB) reaction Isocyanide Chemistry Multicomponent reactions [2.2]Paracyclophane 1 1 1 01/18/22 20220113 NES 220113 B The Groebke-Blackburn-Bienaymé three-component reaction b (GBB-3CR) has contributed enormously to the progress of organic synthesis, medicinal chemistry, and materials science. [Extracted from the article]

This report describes the synthesis of a [2.2]paracyclophane‐derived annulated 3‐amino‐imidazole ligand library through a Groebke‐Blackburn‐Bienaymé three‐component reaction (GBB‐3CR) approach employing formyl‐cyclophanes in combination with diverse aliphatic and aromatic isocyanides and heteroaromatic amidines. The GBB‐3CR process gives access to skeletally‐diverse cyclophanyl imidazole ligands, namely 3‐amino‐imidazo[1,2‐a]pyridines and imidazo[1,2‐a]pyrazines. Additionally, a one‐pot protocol for the GBB‐3CR by an in situ generation of cyclophanyl isocyanide is demonstrated. The products were analyzed by detailed spectroscopic techniques, and the cyclophanyl imidazo[1,2‐a]pyridine was confirmed unambiguously by single‐crystal X‐Ray crystallography. The cyclophanyl imidazole ligands can be readily transformed to showcase their useful utility in preparing N,C‐palladacycles through regioselective ortho‐palladation. [ABSTRACT FROM AUTHOR]

In this work, we first designed and synthesized tetraphenylene‐fused aryl‐imidazole derivatives TM‐1–4 via regulation of molecular structure, which were consisted of 1H‐imidazo[4,5‐f][1,10]phenanthroline, 1H‐phenanthro[9,10‐d]imidazole, 4,5‐diphenyl‐1H‐imidazole, 3,3′‐(1H‐imidazole‐4,5‐diyl)dipyridine moieties and AIE‐active tetraphenylethene units, respectively. The results illustrated that TM‐1–4 exhibited clear AIE characteristics. Meanwhile, TM‐2 and TM‐3 show excellent solid emission properties (ΦTM‐2=13.73 % and ΦTM‐3=36.21 %), whereas TM‐1 and TM‐4 exhibit the opposite properties (ΦTM‐1=1.48 % and ΦTM‐4=4.83 %). The multiple rotors (pyridine and benzene ring) causes twisted conformations of the molecule that prevents π‐π stacking and enhances solid emission(ΦTM‐2<ΦTM‐3, ΦTM‐1<ΦTM‐4). Significantly, TM‐2 and TM‐3 also exhibited reversible mechanochromic behavior (Emission red shifts: ΔλTM‐2=43 nm and ΔλTM‐3=41 nm) with color changes between blue and green emissions. The powder X‐ray diffraction (PXRD) suggested the disordered state of ground sample could be readily returned to an ordered crystalline. Therefore, the mechanochromisms of TM‐2 and TM‐3 are ascribable to the phase transformation between crystal and amorphous structure. The single crystal X‐ray analysis of TM‐2 reveals a twisted conformation for TPE moiety and the absence of π‐π intermolecular stacking. These excellent optical properties of TM‐2 and TM‐3 make them potentially applications in mechanochromic materials and imaging agents. [ABSTRACT FROM AUTHOR]

A series of dicyano‐imidazole‐based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain pure blue‐emitting organic light‐emitting diodes (OLEDs). The targeted molecules used dicyano‐imidazole with a short‐conjugated system as the electron acceptor to strong intermolecular π‐π interactions, and provide a relatively shallow energy level of the lowest unoccupied molecular orbital (LUMO). The cyano group was selected to improve imidazole as an electron acceptor due to its prominent electron‐transporting characteristics. Four different electron donors, that is, 9,9‐dimethyl‐9,10‐dihydroacridine (DMAC), 10H‐spiro(acridine‐9,9'‐fluoren) (SPAC), and 9,9‐diphenyl‐9,10‐dihydroacridine (DPAC), were used to alternate the highest occupied molecular orbital (HOMO) energy level to tune the emission color further. The crowded molecular structure in space makes the electron donor and acceptor almost orthogonal, reducing the energy gap (ΔEST) between the first excited singlet (S1) and the triplet (T1) states and introducing significant TADF property. The efficiencies of the blue‐emissive devices with imM‐SPAC and imM‐DMAC obtained in this work are the highest among the reported imidazole‐based TADF‐OLEDs, which are 13.8 % and 13.4 %, respectively. Both of Commission Internationale de l′Eclairage (CIE) coordinates are close to the saturated blue region at (0.17, 0.18) and (0.16, 0.19), respectively. Combining these tailor‐made TADF compounds with specific device architectures, electroluminescent (EL) emission from sky‐blue to deep‐blue could be achieved, proving their great potential in EL applications. [ABSTRACT FROM AUTHOR]

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH4][(UO2)3(HTTDS)(H2O)] (1), [(UO2)4(HTTDS)2](HIM)6 (2, IM=imidazole), [(UO2)4(TTDS)(H2O)2(Phen)2] (3, Phen=1,10‐phenanthroline), [Zn(H2O)4]0.5[(UO2)3(HTTDS)(H2O)4] (4), and {(UO2)2[Zn(H2O)3]2(TTDS)} (5), {Zn(UO2)2(H2O)(Dib)0.5(HDib)(HTTDS)} (6, Dib=1,4‐di(1H‐imidazol‐1‐yl)benzene) and [Na]{(UO2)4[Cu3(u3‐OH)(H2O)7](TTDS)2} (7) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5‐dicarboxyphenyl)silicon(H8TTDS). These UOFs have different 3D self‐assembled structures as a function of co‐ligands, structure‐directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO7 pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N‐donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO2]2+ units as co‐ligands. The second metal centers were introduced in the syntheses of 4–7, and in all cases, they are part of the final structures, either as a counterion (4) or as a component of framework (5−7). Interesting, in 7, a rare polyoxometalate [Cu3(μ3‐OH)O7(O2CR)4] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO2)2(O2CR)4] unit. Those uranyl carboxylates were sufficiently determined by single crystal X‐ray diffraction, and their topological structures and luminescence properties were analyzed in detail. [ABSTRACT FROM AUTHOR]

Instead of using organic solvents, a deep eutectic solvent (DES) composed of tetrabutylammonium bromide and imidazole (Bu4NBr/Im) was employed as a solvent for the first time to synthesize covalent organic frameworks (COFs). Due to the low vapor pressure of the Bu4NBr/Im‐based DES, a new carboxyl‐functionalized COF (TpPa‐COOH) was synthesized under environmental pressure. The as‐synthesized TpPa‐COOH has open channels, and the DES can be removed completely from the pores. The dye adsorption performance of TpPa‐COOH was examined for three organic dyes with similar molecular sizes: one anionic dye (eosin B, EB) and two cationic dyes (methylene blue, MB and safranine T, ST). TpPa‐COOH showed an excellent selective adsorption effect on MB and ST. The electronegative keto form in TpPa‐COOH might help to form electrostatic and π–π interactions between the π‐stacking frameworks of TpPa‐COOH and the positive plane MB and ST molecules. The adsorption isotherms of MB and ST on TpPa‐COOH were further investigated in detail, and the equilibrium adsorption was well modeled by using a Langmuir isotherm model. Together with hydrogen bonding, TpPa‐COOH showed higher adsorption capacity for ST than for MB (1135 vs. 410 mg g−1). These results could provide a guidance for the green synthesis of adsorbents in removing organic dyes from wastewater. [ABSTRACT FROM AUTHOR]

The intermarriage of neutral and tripodal imidazole ligand, tris(4‐(1H‐imidazol‐1‐yl)phenyl)amine (TIPA), with zinc phosphite yields two hybrid phosphites, [Zn2(HPO3)2(TIPA)]⋅2 H2O (1) and [Zn3(HPO3)3(TIPA)]⋅6 H2O (2). Compound 1 has a hybrid sheet with neutral zinc‐phosphite chains as supramolecular building blocks (SBBs), whereas 2 exhibits a 3D hybrid architecture with other neutral zincophosphite chains as supramolecular building blocks. The structural discrepancy between 1 and 2 is mainly due to the distinct linkage modes between organic TIPA ligands and inorganic zincophosphite chains. Interestingly, compounds 1 and 2 feature fast photochromism in response to UV light irradiation under ambient conditions. The discrepancy of photochromic performance between 1 and 2 is mainly due to the different geometrical configuration of the TIPA ligand. Different to majority of reported hybrid photochromic compounds driven by photochromic active units, the photochromism in 1 and 2 is derived from the electron transfer (ET) between phosphite and non‐photochromic triimidazole‐derivative ligand TIPA. Compared with the widely explored nonphotochromic polypyridine‐derivative as electron acceptors (EAs), our work provides a new EA model for the design of hybrid photochromic materials based on the ligand‐to‐ligand ET mechanism. A multiple anti‐counterfeiting application based on 1 and 2 was investigated. [ABSTRACT FROM AUTHOR]

Keywords: 2:2 complexes; cucurbituril; host-guest systems; imidazoles; viologen By CB[8] macrocycles made it possible to produce 2:2 host:guest complexes, releasing protons initially trapped on the guests, in a manner similar to the proton release observed in biology and operating through cascade supramolecular events. 2:2 complexes, cucurbituril, host-guest systems, imidazoles, viologen. [Extracted from the article]

We present a new class of tunable aryl alkyl ionic liquids (TAAILs) containing different palladate counter ions. Solid‐state structures for representative compounds have been obtained. Their properties are presented in comparison to those of newly synthesized and reported palladate ionic liquids with conventional counter ions. It was found that the aryl substitution pattern and the type of anion have a profound influence on the melting point. The speciation of the different anions in solution has been rationalized by DFT calculations. Customize, adapt, overcome: Ionic liquids containing a palladate anion are accessible in a very flexible synthetic procedure. The choice of aryl substituent, alkyl group, type of palladate counter ion and halide ligand can all be modified to allow for fine‐tuning of the properties of a wide range of new compounds. [ABSTRACT FROM AUTHOR]

This study details attempts to access N‐heterocyclic carbenes (NHCs) featuring the diazaborolyl group, {(HCNDipp)2B}, as one or both of the N‐bound substituents, to generate strongly electron‐donating and sterically imposing new carbene ligands. Attempts to isolate N‐heterocyclic carbenes based around imidazolylidene or related heterocycles, are characterized by facile N‐to‐C migration of the boryl substituent. In the cases of imidazolium precursors bearing one N‐bound diazaborolyl group and one methyl substituent, deprotonation leads to the generation of the target carbenes, which can be characterized in situ by NMR measurements, and trapped by reactions with metal fragments and elemental selenium. The half‐lives of the free carbenes at room temperature range from 4–50 h (depending on the pattern of ancillary substituents) with N‐to‐C2 migration of the boryl function being shown to be the predominant rearrangement pathway. Kinetic studies show this to be a first‐order process that occurs with an entropy of activation close to zero. DFT calculations imply that an intramolecular 1,2‐shift is mechanistically feasible, with calculated activation energies of the order of 90–100 kJ mol−1, reflecting the retention of significant aromatic character in the imidazole ring in the transition state. Trapping of the carbene allows for evaluation of steric and electronic properties through systems of the type LAuCl, LRh(CO)2Cl, and LSe. A highly unsymmetrical (but nonetheless bulky) steric profile and moderately enhanced σ‐donor capabilities (compared with IMes) are revealed. Borylated NHCs: Attempts to access N‐heterocyclic carbenes (NHCs) featuring the diazaborolyl group, {(HCNDipp)2B}, as the N‐bound substituent(s) are reported. These are characterized by facile N‐to‐C migration, although in the cases of imidazolium systems bearing one diazaborolyl and one Me substituent, the target carbenes can be characterized in situ by NMR measurements, and trapped by reactions with metal fragments and elemental selenium (see figure). [ABSTRACT FROM AUTHOR]

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1‐alkyl‐3‐methylimidazolium cations (i.e. [Cnmim]+) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron‐withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate‐containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials. Overlooked but not forgotten! Versatile azolate anions as a promising ionic liquid component for new tailored materials. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility. [ABSTRACT FROM AUTHOR]

The successful incorporation of a thermally fragile imidazolium moiety into a covalent triazine framework resulted in a heterogeneous organocatalyst active in carbene‐catalyzed umpolung reaction. The structural integrity of the imidazolium moiety was confirmed by combining solid‐state NMR and XPS experiments. Porous polymers: The immobilisation of an undamaged charged imidazolium moiety into a microporous covalent triazine framework (imid‐CTF) is described. A finely adjusted synthetic protocol enabled the structural preservation of the thermally labile imidazolium motif, which was verified by an in‐depth structural characterization, applying various spectroscopic techniques (see scheme). [ABSTRACT FROM AUTHOR]

The synthesis and characterization of the first bidentate C^C* cyclometalated platinum(II) complexes based on abnormal N‐heterocyclic carbenes (aNHC) is presented. The aNHC ligand precursors are prepared from benzonitriles and anilines to form 1,2,3‐trisubstituted imidazolium salts. The title compounds were synthesized by in situ generation of the silver carbene complex, followed by transmetalation to platinum and subsequent introduction of the β‐diketonate ligand. Structural characterization by 2D NMR experiments, as well as solid‐state structures unequivocally prove the abnormal binding mode of the aNHC ligands. Additionally, the photophysical properties of the platinum(II) complexes were examined and studied in detail by DFT calculations and cyclic voltammetry experiments. The title compounds proved to be strongly emissive at room temperature in the green to orange region of the visible spectrum, with emission efficiencies of up to 69 %. Photoluminescent platinum: The synthesis and characterization of the first platinum(II) complexes with C^C* cyclometalated aNHC ligands is reported. The abnormal binding mode was unequivocally confirmed by solid‐state structures and NMR experiments. Photoluminescence measurements, accompanied by DFT calculations and electrochemistry experiments, allowed insight into the emission characteristics of this class of compounds. [ABSTRACT FROM AUTHOR]

Abstract: Selective copper(I) to palladium(0) transmetallation of P‐donors from the rigid N,N′‐diphosphanyl‐imidazol‐2‐ylidene C3H2[NP(tBu)2]2 (PCNHCP) was observed when known [Cu3(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)3 was reacted with [Pd(PPh3)4]. When 1.2 equivalents of [Pd(PPh3)4] was used, the product [Cu2Pd(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)2 (2(OTf)2) was obtained, which features a CuI–CuI–Pd0 chain and appears to be the first linear heterotrinuclear complex with d10–d10 interactions between Pd0 and CuI. When the Cu3 precursor was reacted with 3.0 equivalents of [Pd(PPh3)4], the complex [CuPd2(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)2 (3(OTf)2) was obtained, which, on the basis of magnetic measurements, DFT calculations, and computed nuclear shieldings, was formulated as containing a Pd0–CuI–Pd0 chain with an electron hole delocalized over the whole cation, including the metal chain. Similarly, selective transmetallation of the P‐donors in [Ag3(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)3 from silver to palladium (originating from [Pd(PPh3)4]) gave the linear chain [Ag2Pd(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)2 (5(OTf)2), which on the basis of NMR spectroscopy comprises an AgI–AgI–Pd0 metal core. However, X‐ray diffraction data collected on various samples of 5(OTf)2 were modeled with 50:50 metal disorder at the terminal positions, corresponding to a (AgI/Pd0)–AgI–(AgI/Pd0) formulation. Upon standing in solution, 5(OTf)2 transformed to 6(OTf)2, the regioisomer of 5(OTf)2 in which the Pd center has migrated to the central position of an AgI–Pd0–AgI chain. Prolonged standing in CH2Cl2 or by reaction with [PtCl2(NCMe)2] converts complex 6(OTf)2 to the AgI/PdII complex [Ag2PdCl2(μ3‐PCNHCP,κP,κCNHC,κP)2](OTf)2 (7(OTf)2). The structural data of 2(OTf)2, 3(OTf)2, and 7(OTf)2 establish significant heterometallophilic interactions. [ABSTRACT FROM AUTHOR]