19872-93-6Relevant academic research and scientific papers
Electronic: Versus steric effects of pyridinophane ligands on Pd(III) complexes
Tang, Fengzhi,Park, Sungho V.,Rath, Nigam P.,Mirica, Liviu M.
, p. 1151 - 1158 (2018)
Several new PdII and PdIII complexes supported by electronically and sterically tuned tetradentate pyridinophane ligands MeN4OMe, MeN4, and tBuN4 were isolated and fully characterized (MeN4OMe: N,N′-dimethyl-2,11-diaza[3,3](2,6)-para-methoxypyridinophane; MeN4: N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane; tBuN4: N,N′-di-tert-butyl-2,11-diaza[3,3](2,6)pyridinophane). Cyclic voltammetry studies, UV-vis and EPR spectroscopy, and X-ray crystallography were employed to reveal that the steric properties of the N-substituents of the RN4 ligands have a pronounced effect on the electronic properties of the corresponding PdIII complexes, while the electronic tuning of the ligand pyridyl groups has a surprisingly minimal effect. An explanation for these observations was provided by DFT and TD-DFT calculations which suggest that the electronic properties of the PdIII complexes are mainly dictated by their frontier molecular orbitals that have major atomic contributions from the Pd center (mainly the Pd dz2 atomic orbital) and the axial N atom donors.
Scanning-tunneling-spectroscopy-directed design of tailored deep-blue emitters
Sanning, Jan,Ewen, Pascal R.,Stegemann, Linda,Schmidt, Judith,Daniliuc, Constantin G.,Koch, Tobias,Doltsinis, Nikos L.,Wegner, Daniel,Strassert, Cristian A.
, p. 786 - 791 (2015)
Frontier molecular orbitals can be visualized and selectively set to achieve blue phosphorescent metal complexes. For this purpose, the HOMOs and LUMOs of tridentate PtII complexes were measured using scanning tunneling microscopy and spectroscopy. The introduction of electron-accepting or -donating moieties enables independent tuning of the frontier orbital energies, and the measured HOMO-LUMO gaps are reproduced by DFT calculations. The energy gaps correlate with the measured and the calculated energies of the emissive triplet states and the experimental luminescence wavelengths. This synergetic interplay between synthesis, microscopy, and spectroscopy enabled the design and realization of a deep-blue triplet emitter. Finding and tuning the electronic "set screws" at molecular level constitutes a useful experimental method towards an in-depth understanding and rational design of optoelectronic materials with tailored excited state energies and defined frontier-orbital properties.
Sulfur transfer reactions of a zinc tetrasulfanido complex
Ballesteros Ii, Moises,Tsui, Emily Y.
, p. 16305 - 16311 (2020)
A zinc tetrasulfanido complex supported by a bis(carboxamide)pyridine ligand framework has been synthesized by the insertion of elemental sulfur into the zinc-S(thiolate) bond of a zinc dithiolate complex ([LZn]2-). This paper reports on sulfur transfer reactions of this polysulfanido complex ([1]2-) and compares this behavior to known reactions of metal polysulfido complexes. Complex [1]2- was demonstrated to be in exchange with [LZn]2- and free elemental sulfur in solution. Although triphenylphosphine abstracts sulfur from [1]2- to form [LZn]2-, complex [LZn]2- can abstract sulfur from the zinc polysulfido complex (TMEDA)ZnS6 (TMEDA = N,N,N′,N′-tetramethylethylenediamine). The tetrasulfanido complex [1]2- can also transfer sulfur to dimethyl acetylenedicarboxylate to form a zinc dithiolene complex. These studies demonstrate that the zinc complex with a tetrasulfanido moiety can undergo similar reactions as metal complexes with purely inorganic polysulfido groups, although the final metal-containing products are different.
Electron transfer pathways in photoexcited lanthanide(iii) complexes of picolinate ligands
Kovacs, Daniel,Kocsi, Daniel,Wells, Jordann A. L.,Kiraev, Salauat R.,Borbas, K. Eszter
supporting information, p. 4244 - 4254 (2021/04/06)
A series of luminescent lanthanide(iii) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate ligands. The antennae carried methyl, methoxymethyl or trifluoromethyl substituents in their 4-positions, allowing for a range of excited state energies and antenna electronic properties. The1H NMR spectra of the Eu(iii) complexes were found to be analogous to each other. Similar results were obtained in the solid-state by single-crystal X-ray crystallography, which showed the structures to have nine-coordinate metal ions with heavily distorted tricapped trigonal prismatic geometries. Steady-state and time-resolved luminescence spectroscopy showed that the antennae could sensitize both Tb(iii) and Eu(iii), however, quantum yields were lower than in other octadentate complexes lacking pyridylcarboxylate. Complexes with more electron-poor pyridines were less emissive even when equipped with the same antenna. The oxidation and reduction potentials of the antennae and the pyridinecarboxylates, respectively, were determined by cyclic voltammetry. The obtained values were consistent with electron transfer from the excited antenna to the pyridine providing a previously unexplored quenching pathway that could efficiently compete with energy transfer to the lanthanide. These results show the crucial impact that photophysically innocent ligand binding sites can have on lanthanide luminescence.
COMPOUNDS AND COMPOSITIONS FOR THE TREATMENT OF PAIN
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Page/Page column 70; 72, (2019/08/26)
The invention relates to compounds, pyridine derivatives, and pharmaceutical 10 compositions containing same for use in the treatment of pain. It also relates to specific compounds, compositions comprising the same and uses thereof, in particular in the treatment of pain.
Synthesis of 2,6-di(1,8-naphthyridin-2-yl)pyridines functionalized at the 4-position: Building blocks for suitable metal complex-based dyes
Nakamura, Shunsuke,Takase, Tsugiko,Oyama, Dai
, p. 1396 - 1405 (2019/05/01)
This study reports the synthesis of a methoxy-substituted 2,6-di(1,8-naphthyridin-2-yl)pyridine using Friedl?nder methodology. The functionalization at the 4-carbon of the methoxy-substituted derivative was confirmed by X-ray structural analysis. Finally, the methyl ether protecting group was cleaved to obtain 2,6-di(1,8-naphthyridin-2-yl)pyridine-4-ol. Using the compounds, coordination behavior to ruthenium(II) center was also examined.
Nonanuclear Ni(II) complexes in a [1-7-1] formation derived from asymmetric multidentate ligands: Magnetic and electrochemical properties
Tsuji, Yasuhiro,Togo, Tatsuo,Mishima, Akio,Koshiyama, Tomomi,Ohba, Masaaki
supporting information, p. 4036 - 4039 (2018/03/26)
Nonanuclear Ni(ii) complexes, [Ni9(Ln)6(OH)6(H2O)6] (Ni9Ln, n = 1-4; H2Ln = 6-acetoacetyl-2-pyridinecarboxylic acid derivatives), were prepared via self-assembly using the asymmetric multidentate ligands H2Ln. A corner-sharing tetrahedron-type structure, [Ni7(μ3-OH)6]8+, and terminal mononuclear units constitute the nonanuclear structure in a [1-7-1] formation. The electrochemical and magnetic properties of Ni9Ln were modulated by the introduction of various substituents in H2Ln.
A formal anti-Markovnikov hydroalkoxylation of allylic alcohols with a ruthenium catalyst
Nakamura, Yushi,Ohta, Tetsuo,Oe, Yohei
, p. 288 - 291 (2018/02/14)
Hydroalkoxylation of C-C double bonds was achieved through the use of a ruthenium catalyst. The reaction of allylic alcohols with nucleophilic alcohols was carried out in the presence of a ruthenium catalyst prepared by RuClH(CO)(PPh3)3 and 2,6-bis(n-butyliminomethyl)-4-(piperidin-1-yl)pyridine under mild reaction conditions to afford the corresponding γ-alkoxypropanols in good yield.
Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate
Fan, Ruixi,Serrano-Plana, Joan,Oloo, Williamson N.,Draksharapu, Apparao,Delgado-Pinar, Estefanía,Company, Anna,Martin-Diaconescu, Vlad,Borrell, Margarida,Lloret-Fillol, Julio,García-Espa?a, Enrique,Guo, Yisong,Bominaar, Emile L.,Que, Lawrence,Costas, Miquel,Münck, Eckard
supporting information, p. 3916 - 3928 (2018/03/26)
The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by M?ssbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a M?ssbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the M?ssbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (～75%) with some FeIV(O)(?OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 ? away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.
The Influence of para Substituents in Bis(N-Heterocyclic Carbene) Palladium Pincer Complexes for Electrocatalytic CO2 Reduction
Therrien, Jeffrey A.,Wolf, Michael O.
, p. 1161 - 1172 (2017/02/15)
The effect of modifying the pyridyl para position of lutidine-linked bis(N-heterocyclic carbene) Pd pincer complexes is studied both experimentally (R = OMe, H, Br, and COOR) and computationally, showing a strong effect on the first reduction potential of the complex and allowing the reduction potential to be tuned over a wide range in relation to the Hammett σp constant of the para substituent. The effect of the pyridyl para substituent on electron density of the metal center, frontier orbital energies, and dissociation energy of the trans ligand are also investigated in the context of reactivity with CO2 through electrochemical characterization of the complexes under N2 and CO2 and controlled potential electrolysis experiments where CO2 is reduced to CO.
