Effects of electron-rich ancillary ligands on green and yellow-emitting bis-cyclometalated iridium complexes

Abstract

Six new green to yellow-emitting heteroleptic bis-cyclometalated iridium(III) complexes of the type Ir(C?N)₂(L?X) (C?N?=?cyclometalating ligand, L?X?=?monoanionic chelating ancillary ligand) bearing two widely used cyclometalating ligands (C?N?=?2-(2-thienyl)pyridine (thpy) and 2-phenylbenzoxazole (bo)) and six different ancillary ligands were prepared. In this study, the complexes include structurally diverse ancillary ligands that allow us to investigate several aspects of structure-property relationships. Ancillary ligands used in this study are small-bite-angle N-phenylacetamidate (paa), N-isopropylbenzamidate (ipba) and N,N′-diisopropylbenzamidinate (dipba), and larger bite-angle β-ketoiminate (acNac), β-diketiminate (NacNac), and β-thioketoiminate (SacNac). The emission color is governed by the choice of the cyclometalating ligand, but the ancillary ligands influence the electrochemical and photophysical properties. Electrochemical analysis shows that the energy of the HOMO varies substantially as the L?X structure is altered, whereas the energy of LUMO remains nearly constant. The emission maxima range from 537?nm to 590?nm, with solution quantum yields between 0.0094 and 0.60 and microsecond lifetimes. The results here reveal the ancillary ligands provide a channel to control redox properties and excited-state dynamics in cyclometalated iridium complexes that luminesce in the middle regions of the visible spectrum.     

Theoretical investigations into trioxo group 7 compounds LRO3 with perfluorated ligands

Group 7 trioxides LRO₃ with perfluorated ligands L (L = CF₃, C₅F₅ and C₆F₅) are investigated using density based (BP86) and wave-function based (MP2) methods together with energy-adjusted scalar relativistic pseudopotentials for the metal atoms Mn, Tc and Re. The C₆F₅ compounds have short metal-carbon bond distances and are more stable than the η¹-C₅F₅ and the CF₃ compounds. The perfluorinated cyclopentadienyl compounds, C₅F₅MO₃, all are η¹ coordinated in contrast to the C₅Me₅MO₃ homologues. Our calculations indicate that C₆F₅MnO₃ might be a stable complex and therefore a promising target for future synthesis.     

介绍一种金属有机化合物的分类新方法: 共价键分类法

本文比较详细地介绍了M.L.H.Green最近提出的金属有机化合物分类新方法-共价键分类法，包括基本概念、MLX丰度图的绘制及其在提供金属的反应性与反应机理等信息方面的应用。     

Radical steps in the reactions of organometallic compounds with 2-methyl-2-nitrosopropane: experimental evaluation of the validity of the nitroxyl method for investigations of homolytic reactions of organometallic compounds

Radical adducts formed in the reactions of organometallic compounds of group II-V elements and of some organochromium and organoiron compounds with 2-methyl-2-nitrosopropane and phenyl(tert-butyl)nitrone were studied by ESR. Nitroso compounds and nitrones can be used as selective spin traps for investigations of homolytic reactions involving organometallic compounds.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 916–920, May, 1994.     

Mechanochemical tools in the synthesis of organometallic compounds

In response to rising environmental concerns, chemistry is experiencing a considerable change in both concepts and practices to adopt more efficient and sustainable technologies. One of the alternative technologies that offer many advantages over the conventional solution-based techniques is mechanochemistry which utilizes mechanical energy to induce chemical reactions. Despite the fact that mechanochemistry has reached high significance in the creation of advanced materials, such as alloys, ceramics, electrode materials, and nanocomposites, in the field of small molecule synthesis its potential remains largely untapped. This review highlights the opportunities and prospects of different mechanochemical tools in the synthesis of organometallic compounds, including transition metal complexes with N-heterocyclic carbene, arene, and cyclopentadienyl ligands, monometallacyclic and pincer derivatives, as well as main group metal compounds (e.g., allyl complexes and the Grignard reagents). Many important organometallic transformations such as C–H bond metalation, transmetalation, and oxidative addition can be successfully implemented under mechanochemical conditions in a highly productive and energy-saving manner. Furthermore, the postmodification of metal-containing species upon grinding or milling is shown to be a powerful route to both new discrete metal complexes and different supramolecular architectures (metal-containing organic cages, macrocylces, networks).     

Visualizing lone pairs in compounds containing heavier congeners of the carbon and nitrogen group elements

In this mini-review, I discuss some recent work on the stereochemistry and bonding of lone pairs of electrons in divalent compounds of the heavier carbon group elements (Sn^II , Pb^II) and in trivalent compounds of the heavier nitrogen group elements (Bi^III). Recently developed methods that permit the real-space visualization of bonding patterns on the basis of density functional calculations of electronic structure, reveal details of the nature of s electron lone pairs in compounds of the heavier main group elements — their stereochemistry and their inertness (or lack thereof). An examination of tetragonalP4/nmm SnO, α-PbO and BiOF, and cubic PbS provides a segue into perovskite phases of technological significance, including ferroelectric PbTiO₃ and antiferroelectric/piezoelectric PbZrO₃, in both of which the lone pairs on Pb atoms play a pivotal r?le.     

Laser photochemistry of organometallic compounds related to applications in microelectronics

Photochemistry of organometallic compounds achieves a marriage of a rich variety of organometallic chemistry and the full potential of electronically excited states of molecules. The application of lasers as light sources adds a great many new features to these studies, which cannot be attained by other means, because lasers provide light of such a high quality, e.g. a high-intensity, energetic (i.e. wavelength) purity, a high degree of coherence, and a high spatial and temporal resolution. Laser photochemistry of organometallic compounds, such as laser photochemical vapor deposition (LPCVD), laser ablation, and photochemical dry etching, forms the basis of many important industrial processes which sustain the present-day microelectronics industries. Lasers are used not only to photodissociate organometallic molecules, but to monitor the reaction steps by probing the starting material, chemical intermediate, or final product by many laser-based spectroscopic methods. Although it is a very young area of science (the first laser was operated in 1960), this research area is now really ebullient, as a result of strong interest from both the fundamental and the practical sides. Laser photochemistry of organometallic compounds extends a wide and fertile research frontier, full of challenge and novel possibilities. In the present review, the present status of laser (ultraviolet and visible) photochemistry of organometallic compounds related to these industrial applications is briefly reviewed, with special emphasis on the basic studies of the relevant photochemistry and their relationship to photochemical processes on solid surfaces.     

Carbonyl group‐containing organometallic intramolecular‐coordination five‐membered ring compounds

Carbonyl group‐containing organometallic intramolecular‐coordination five‐membered ring compounds are easily synthesized by the following five reaction methods: (1) cyclometalation, especially, orthometalation reactions; (2) the reactions of the moieties of an unsaturated carbon? carbon bond attached to a carbonyl group (C?C? CO, C?C? CO); (3) the reactions of an unsaturated carbon? carbon bond with carbon monoxide (C?C and CO, C?C and CO); (4) carbonylative ring expansion reactions; and (5) others. These compounds are very easily and regio‐specifically synthesized with many kinds of metal compounds, including both transition metals and main group metals. Many of such the reactions are easily applied to organic syntheses. Copyright © 2010 John Wiley & Sons, Ltd.     

Reactions of organic halides with organometallic compounds and terminal acetylenes catalyzed by palladium complexes

The results of the investigation of the cross-coupling of organometallic compounds and terminal acetylenes with organic halides catalyzed by transition metal complexes are generalized and analyzed. The influence of different factors on the rate and selectivity of catalytic cross-coupling is discussed. A detailed mechanism of the cross-coupling of Grignard reagents with organic halides is suggested. The cross-coupling reaction involving organotin compounds proceeds under very mild conditions in the presence of a ligand-free Pd catalyst. Examples of using catalytic cross-coupling of organic halides with organomagnesium, organozinc, and organotin compounds are presented.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2148–2167, September, 1996.     

Multiisotopic modeling of fragmentation ion patterns in mass spectra of organometallic and coordination compounds

Investigation of hardly interpretable complex patterns can lead to an explanation of details of fragmentation and, therefore, the identification of ion clusters can be a significant procedure of mass spectra interpretation. The modeling presented remains a simple tool for mass spectra interpretation and determination of parameters of complex cluster components. Good adjustment of model to experimental data suggests that such components must be considered in the pattern interpretation; approach results in the model fits within a 1% precision for the cluster of two or more components. Applications of the Multiisotopic Modeling of Fragmentation Ion Patterns (MMFIP method) are presented for bis(dibutyldithiophosphate)‐zinc(II)‐[(C₄H₉O)₂PS₂]₂Zn, 1′,1‴‐dibenzylbiferrocene‐C₃₄H₃₀Fe₂ and 1,1′,2,2′,3,3′‐hexachloroferrocene‐C₁₀H₄Cl₆Fe as examples. It seems that the isotopic cluster modeling based on the least squares method can be a helpful aid for determination of the complex pattern components. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 354–365, 2001     

Synthesis and structures of the first cationic perfluoroaryllanthanoid(II) complexes

Tetraphenylborate salts of solvated pentafluorophenyllanthanoid(II) cations [Ln(C(6)F(5))(thf)(n)](+) (Ln=Eu, n=6 (1); Ln=Yb, n=5 (2)) were readily synthesized in high yield by reactions of ytterbium or europium with HgPh(C(6)F(5)) and Me(3)NHBPh(4) in THF. The structures of 1.THF and 2 confirmed the existence of well-separated ions and both 1 and 2 show notable thermal stability at room temperature. The cation in 2 was also observed in the remarkable mixed-valent complex [Yb(II)(C(6)F(5))(thf)(5)][Yb(III)(C(6)F(5))(2)[N(SiMe(3))(2)](2)] (3), fortuitously isolated in low yield from a reaction of ytterbium metal, HgPh(C(6)F(5)), and HN(SiMe(3))(2) in THF, and which additionally has an unusual bis(pentafluorophenyl)bis[bis(trimethylsilyl)amido)]ytterbate(III) anion. (171)Yb-(19)F coupling has been observed in the low-temperature (171)Yb NMR spectra of 2 and [Yb(C(6)F(5))(2)(thf)(4)].     

P NMR spectroscopy in benzoxazine model compounds and benzoxazine chemistry - main chain and end group studies

Using ³¹P NMR spectroscopy after phosphorylation, different phenols are easily discriminated. Proposed phenolic model compounds from benzoxazine reaction/polymerization are phosphorylated with 2-chloro-1,3,2-dioxaphospholane directly in an NMR tube. The dimer and oligomer structure of benzoxazine is different from that of monomer, that is, the breaking of the oxazine ring upon polymerization results in the formation of Mannich bridge structure linking phenolic groups together. Different electronic environment in the phosphorus derivatives of the methylamine-based benzoxazine model dimer and oligomers allows comparison of these ³¹P NMR spectra with the ³¹P-NMR spectra of the compounds from traditional benzoxazine polymerization provides useful end group information. Phenolic functional groups in benzoxazine dimer and oligomers, e.g. phenolic end groups and phenolic groups on the backbone, are studied.     

A survey of crystal structures and biological activities of platinum group metal complexes containing N-acylthiourea ligands

Abstract

N-Acyl-thioureas are important compounds in the field of organic synthesis and medicinal chemistry. Research interest in these compounds has grown recently because coordination to metal ions enhances their application especially in view of medicinal studies. These thiourea derivatives possess rich coordination chemistry and the coordination behavior of these derivatives alters upon reaction with different metals. Such ligands generally coordinate to Pt(II) and Pd(II) ions in a bidentate S,O manner and often coordinate to Ru(II), Rh(III) and Ir(III) centers through the S donor atom. We isolated some complexes of these ligands by reaction with sodium azide which coordinates to Ru(II), Rh(III), and Ir(III) in a bidentate S,N fashion. The deprotonated thiourea nitrogen atom resulted in the formation of strained 4-membered ring structures around the metal center. Biological application of N-acyl thiourea derivatives and their platinum group metal complexes are further discussed. Studies has shown that these compounds can be used as drugs to treat several human diseases like microbial infections, tuberculosis, carcinomas, malaria, leishmaniasis, urease inhibitors and anti-inflammatory. This review intends to summarize the recent advancement in the chemistry of N-acyl-thioureas and highlight some perspectives in the synthesis, versatile coordination behavior to ruthenium, rhodium, iridium, platinum and palladium, and their metal complexes in biological applications.     

The effect of ionization and CH3 ligand for hydrogen storage in Co‐ and Ni‐based organometallic compounds

Maximum capacities of the hydrogen storage in organometallic compounds consisting of Co and Ni atoms bound to C_mH_m ring (m = 4, 5; capped type) were, respectively, found as 3.48 and 3.49 wt % (Guo et al., Struct Chem, 2009, 20, 1107). Here, we extend this study to structures having a transition metal (TM) inserted in C_mH_m ring (inserted type), having TM located on either a C₄H or a C₅H molecule, and the CH₃ ligand bound to the organometallic compounds. We find that for the CoC₄H₄ and NiC₄H₄ complexes, the capped types are 1.39 eV and 1.41 eV higher in energy than the inserted types, respectively, while the ground states for CoC₅H₅ and NiC₅H₅ complexes are found to be the capped type, which are lower than the inserted types, respectively, by 1.27 eV and 1.31 eV. The maximum capacity of hydrogen storage reached 5.13 wt % for both of CoC₄H(H₂)₃ complex and the inserted‐type CoC₄H₄(H₂)₃ complex with a reasonable binding energy (0.3–1.0 eV per H₂). The positively charged C₄H₄ and C₅H₅ molecules do not only improve the capacity of hydrogen storage but also make all H₂ adsorbing in molecular form and keep the adsorption energy in an ideal range. After adding the CH₃ ligand to the compounds, the average adsorption energy of H₂ decreased to an ideal range 0.61–0.94 eV per H₂ and the stability of the compounds is also improved. Finally, we analyze the HOMO–LUMO gaps and display the kinetic stability when H₂ was added to organometallic compounds. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acids

The binding capacity of fulvic and alginic acids towards trimethyl tin(IV) cation was quantitatively determined in order to evaluate the sequestering ability of toxic organometallic compounds by natural organic matter. Investigations were performed in the pH range of natural waters (5–8.5) where the carboxylate groups, largely present in both sequestering agents, are the main binding sites. A chemical interaction model, according to which both the protonation of polyelectrolyte ligands and the hydrolysis of the organotin cation in NaCl aqueous solution were considered, was used to define the speciation of the systems under investigation. Measurements performed at different ionic strength values (0.1, 0.25, 0.5 and 0.7 mol L^?1, NaCl) allowed us to consider the dependence of stability constants on the ionic strength, and to calculate the formation constants at infinite dilution. Results obtained show the formation of the complex species TMT(L), TMT(L)₂ and TMT(L)(OH) for L = fulvic acid and TMT(L) for L = alginic acid, respectively. In order to compare the strength of interaction of these natural poly electrolytes with other analogous synthetic polyelectrolytes, measurements were also carried out on the trimethyltin(IV)–polyacrylate (5.1 kDa) system, and in this case the formation of TMT(L), TMT(L)₂ and TMT(L)(OH) species was found. Results show the following trend of stability for the species TMT(L) in the systems investigated: TMT–fulvate ≈ TMT–polyacrylate > TMT–alginate. On the basis of the stability data obtained, the lowest concentration of fulvic and alginic acids, able to act as sequestering agents towards triorganotin(IV) cation in the conditions of natural waters, was also calculated. Copyright © 2006 John Wiley & Sons, Ltd.     

Three main group metal coordination polymers bearing imidazole-based dicarboxylates: Hydro(solvo)thermal syntheses, crystal structures and properties

Three coordination polymers [Pb(HMIDC)]_n (1), [Ba(H₂MIDC)₂]_n (2) and {[Mg(HMIDC)(H₂O)₂]·H₂O}_n (3) (H₃MIDC = 2-methyl-1H-imidazole-4,5-dicarboxylic acid) have been yielded under different hydro(solvo)thermal conditions. X-ray diffraction analysis reveals that compound 1 exhibits a 3-D framework constructed by 2-D networks joined by μ₄-HMIDC²⁻ bridges. Compound 2 also presents a 3-D structure, which is generated from 2-D layers pillared by 1-D chains along the c-axis. Compound 3 is a 1-D infinite chain and forms supramolecular layers through hydrogen bonds. The thermal and solid-state photoluminescence properties of polymers 1-3 have been determined as well. The theoretical predication of the methyl substituent effect of the ligand H₃MIDC has been investigated.