49669-13-8Relevant articles and documents
New nucleobase analogs for the extension of the triple helix recognition code
Lengeler,Weisz
, p. 1657 - 1658 (1999)
Molecular modeling was used to design novel nucleobases for the specific recognition of Watson-Crick base pairs within a triple helix. The synthesis for one of the nucleoside analogs is described in detail. Preliminary NMR measurements on the monomeric nucleobases in apolar solvents indicate preferred association modes and affinities towards a guanosine-cytidine Watson-Crick base pair.
Trifunctional pNHC, Imine, Pyridine Pincer-Type Iridium(III) Complexes: Synthetic, Structural, and Reactivity Studies
He, Fan,Danopoulos, Andreas A.,Braunstein, Pierre
, p. 198 - 206 (2016)
Iridium(III) complexes with a trifunctional pincer ligand containing protic N-heterocyclic carbene (pNHC), pyridine, and imine donor groups were obtained in two sequential steps: (i) protonation of 2-(1-(2,6-diisopropylphenylimino)ethyl)-6-(1-imidazolyl)pyridine (LCH; the superscript specifies the position of the tautomerizable H atom in the imidazole ring) with HBF4·Et2O to give the imidazolium salt [HLCH]+[BF4]- (protonation always occurs at the imidazole N atom) and (ii) metalation of the latter with [Ir(cod)(μ-Cl)]2 to give the hydrido pincer complex [Ir(H)(Cl)(NCMe){LNH-κ3Nimine,NPy,CNHC}]+[BF4]- (3+[BF4]-). Substitution of MeCN in 3+[BF4]- by treatment with triisopropylphosphine gave the analogue [Ir(H)(Cl)P(i-Pr)3{LNH-κ3Nimine,NPy,CNHC}]+[BF4]- (4+[BF4]-). Chloride abstraction from 3+[BF4]- by AgBF4 gave [Ir(H)(NCMe)2{LNH-κ3Nimine,NPy,CNHC}]2+[BF4-]2 (52+[BF4-]2). The centrosymmetric dinuclear Ir(III) complex [Ir(H)(NCMe){μ-(LCH-H)-κ3Nimine,NPy,C2,κN3}]22+[B(C6F5)3F-]2 (62+[B(C6F5)3F-]2) was obtained after deprotonation of 52+[BF4-]2 with KO-t-Bu, followed by addition of B(C6F5)3. It contains two Ir pincer moieties, each with a Nimine,NPy,C2 donor set, which are connected by the Ir-N bonds involving the imidazolide rings, leading to a μ-C,N bridging mode for the latter. Remarkably, all of the donor atoms in the tetradentate bridging chelating ligands are chemically different. The molecular structures of 3+[BF4]-·CH2Cl2, 4+[BF4]-·CH2Cl2, 52+[BF4-]2·2CH2Cl2, and 62+[B(C6F5)3F-]2·4CH2Cl2 have been determined by X-ray diffraction.
A convenient preparative method for anionic tris(substituted pyrazolyl)methane ligands
Charbonnière, Lo?c J.,Ziessel, Raymond
, p. 6305 - 6307 (2003)
The synthesis of tris[3-(6-carboxypyridin-2-yl)pyrazol-1-yl]methane is described in a linear multi-step protocol. The pyridyl-pyrazolyl arms are first constructed before being condensed with chloroform. Careful study of the condensation reaction shows the presence of an isomeric form of the tris(pyrazolyl)methane derivative in which one of the pyrazolyl substituents is linked through the nitrogen atom at the 2 position of the pyrazol. After acid-catalysed isomerisation to the desired isomer, the intermediate compound was subjected to a carboalkoxylation reaction and a subsequent hydrolysis. These are some rare examples of reactions directly occurring on the tris(pyrazolyl)methane platforms.
Mono- And Dinuclear Coinage Metal Complexes Supported by an Imino-Pyridine-NHC Ligand: Structural and Photophysical Studies
Simler, Thomas,M?bius, Karen,Müller, Kerstin,Feuerstein, Thomas J.,Gamer, Michael T.,Lebedkin, Sergei,Kappes, Manfred M.,Roesky, Peter W.
, p. 3649 - 3661 (2019)
A new imino-pyridine-NHC (NHC = N-heterocyclic carbene) hybrid ligand was accessed through a multistep synthesis, and its coordination chemistry was examined among coinage metals. Mononuclear copper, silver, and gold complexes as well as dinuclear homo- and heterometallic complexes were isolated and fully characterized by spectroscopic methods as well as X-ray crystallography. A comparative study of the structural and photophysical properties of the complexes was performed to get more insight into structure-property relationships. The photoluminescence (PL) properties were investigated in the solid state at temperatures between 20 and 295 K, and systematically compared with those of related complexes bearing a bipyridine-NHC ligand and previously reported by our group. The PL properties can be finely "tuned" depending on the coordinated metals, and the weak emission of the complexes can be traced back to the structural flexibility of the imino-pyridine-NHC framework.
A family of immobilizable chiral bis(pinenebipyridine) ligands
P?llnitz, Alpár,Skupienski, Radek,Stoeckli-Evans, Helen,Crochet, Aurélien,Silvestru, Anca,Fromm, Katharina M.,Mamula, Olimpia
, p. 2555 - 2558 (2013)
New enantiopure ligands containing two (-)-5,6-pinenebipyridine units connected by a bridge situated in position 6′ of the bipyridines have been prepared. The chemically addressable groups of the bridging (hydroxyl or keto) can be covalently bound to various supports in order to heterogenize the ligand. Georg Thieme Verlag Stuttgart · New York.
Synthesis and physical property studies of cyclometalated Pt(II) and Pd(II) complexes with tridentate ligands containing pyrazole and pyridine groups
Chiu, Chi-Wen,Devendhiran, Tamiloli,Kumarasamy, Keerthika,Lin, Mei-Ching
, (2020)
Novel substituted tridentate ligands, which contains a series of pyrazole and pyridine groups as donors, and their cyclometalated complexes have been successfully synthesized. The ligands and complexes were completely characterized by a variety of techniques, such as 1H NMR, UV–Vis, FT-IR, mass spectrometry and elemental analysis. Meanwhile, the single crystal structures of ligand 7 and complex 11 were determined by X-ray crystallography. For ligand 7, due to the effect of delocalization, the C(6)-C(7) bond length in the pyrazole ring is 0.05 ? shorter than a normal C-C bond. After coordinating with the metal centre, the configuration was limited by the coordination sphere, so the bond lengths and bond angles of complex 11 are different from those of ligand 7. Through photoluminescence in acetonitrile solution at ambient temperature, two emission bands have been found between 500 and 600 nm for complexes 9 and 10. Moreover, there are several absorbing bands respectively located at 240 to 250 nm and 300 to 310 nm for ligands 7 and 8 (π(L) → π*(L) and n → π*(L)). A red-shift was observed in the UV spectra, on comparing the complexes with electron-donating and electron-withdrawing groups on the ligand, which is due to the electronic effect of the substituent. One absorbing band is also found at 375 to 425 nm for complexes 9 and 10, and this band is attributed to a MLCT (dπ(Pt) → π*(L)).
Bis(pyrazolato) Bridged Diiron Complexes: Ferromagnetic Coupling in a Mixed-Valent HS-FeII/LS-FeIII Dinuclear Complex
Dechert, Sebastian,Demeshko, Serhiy,Hua, Shao-An,Meyer, Franc,Wong, Joanne W. L.,Ye, Shengfa
supporting information, p. 4137 - 4145 (2020/11/23)
Using a new bis(tridentate) compartmental pyrazolate-centered ligand HL, the bis(pyrazolato)-bridged diiron complex [L2FeII2][OTf]2 (1) and its singly oxidized mixed-valent congener [L2FeIIFeIII][OTf]3 (2) have been synthesized and structurally characterized. While 1 features two HS-FeII ions coordinated to two cis-axial pyridine moieties in a highly distorted octahedral environment, the metal ions in 2 are coordinated by the ligand strand in a trans-axial configuration. Very different Fe–N bond lengths and distinctly different coordination polyhedra are associated with pronounced valence localization in the case of 2. The electronic structures and magnetic properties of 1 and 2 have been further investigated by M?ssbauer spectroscopy and variable temperature magnetic susceptibility measurements. In the case of 1, weak antiferromagnetic coupling is observed between the two HS-FeII ions (J = –0.6 cm–1), while the HS-FeII and LS-FeIII ions in 2 are ferromagnetically coupled (J = +5.2 cm–1) to give an ST = 5/2 ground state with significant zero-field splitting (DFe(II) = 2.3 cm–1). The findings are rationalized with the help of DFT computations.
Iridium(III) Complexes Bearing a Formal Tetradentate Coordination Chelate: Structural Properties and Phosphorescence Fine-Tuned by Ancillaries
Yuan, Yi,Gnanasekaran, Premkumar,Chen, Yu-Wen,Lee, Gene-Hsiang,Ni, Shao-Fei,Lee, Chun-Sing,Chi, Yun
supporting information, p. 523 - 532 (2019/12/30)
Synthesis of the multidentate coordinated chelate N3C-H2, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation of Ir(III) metal complexes bearing a N3C chelate in the tridentate (κ3), tetradentate (κ4), and pentadentate (κ5) modes was executed en route from two nonemissive dimer intermediates [Ir(κ3-N3CH)Cl2]2 (1) and [Ir(κ4-N3C)Cl]2 (2). Next, a series of mononuclear Ir(III) complexes with the formulas [Ir(κ4-N3C)Cl(py)] (3), [Ir(κ4-N3C)Cl(dmap)] (4), [Ir(κ4-N3C)Cl(mpzH)] (5), and [Ir(κ4-N3C)Cl(dmpzH)] (6), as well as diiridium complexes [Ir2(κ5-N3C)(mpz)2(CO)(H)2] (7) and [Ir2(κ5-N3C)(dmpz)2(CO)(H)2] (8), were obtained upon treatment of dimer 2 with pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3, 5, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations. Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the development of highly efficient iridium complexes for OLED applications.
Realization of Highly Efficient Red Phosphorescence from Bis-Tridentate Iridium(III) Phosphors
Gnanasekaran, Premkumar,Yuan, Yi,Lee, Chun-Sing,Zhou, Xiuwen,Jen, Alex K.-Y.,Chi, Yun
supporting information, p. 10944 - 10954 (2019/09/09)
Bis-tridentate Ir(III) metal complexes bring forth interesting photophysical properties, among which the orthogonal arranged, planar tridentate chelates could increase the emission efficiency due to the greater rigidity and, in the meantime, allow strong interligand stacking that could deteriorate the emission efficiency. We bypassed this hurdle by design of five bis-tridentate Ir(III) complexes (1-5), to which both of their monoanionic ancillary and dianionic chromophoric chelate were functionalized derivative of 2-pyrazolyl-6-phenylpyridine, i.e. pzpyphH2 parent chelate. Hence, addition of phenyl substituent to the pyrazolyl fragment of pzpyphH2 gave rise to the precursors of monoanionic chelate (A1H-A3H), on which the additional tert-butyl and/or methoxy groups were introduced at the selected positions for tuning their steric and electronic properties, while precursors of dianionic chelates was judiciously prepared with an isoquniolinyl central unit on pziqphH2 in giving the red-shifted emission (cf. L1H2 and L2H2). Factors affected their photophysical properties were discussed by theoretical methods based on DFT and TD-DFT calculation, confirming that the T1 excited state of all investigated Ir(III) complexes shows a mixed metal-to-ligand charge transfer (MLCT), intraligand charge transfer (ILCT), ligand-to-ligand charge transfer (LLCT), and ligand-centered (LC) transition character. In contrast, the poor quantum yield of 3 is due to the facilitation of the nonradiative decay in comparison to the radiative process. As for potential OLED applications, Ir(III) complex 2 gives superior performance with max. efficiencies of 28.17%, 41.25 cd·A-1 and 37.03 lm·W-1, CIEx,y = 0.63, 0.37 at 50 mA cm-2, and small efficiency roll-off.
Effects of structural modifications on the metal binding, anti-amyloid activity, and cholinesterase inhibitory activity of chalcones
Fosso, Marina Y.,LeVine, Harry,Green, Keith D.,Tsodikov, Oleg V.,Garneau-Tsodikova, Sylvie
supporting information, p. 9418 - 9426 (2015/09/15)
As the number of individuals affected with Alzheimer's disease (AD) increases and the availability of drugs for AD treatment remains limited, the need to develop effective therapeutics for AD becomes more and more pressing. Strategies currently pursued include inhibiting acetylcholinesterase (AChE) and targeting amyloid-β (Aβ) peptides and metal-Aβ complexes. This work presents the design, synthesis, and biochemical evaluation of a series of chalcones, and assesses the relationship between their structures and their ability to bind metal ions and/or Aβ species, and inhibit AChE/BChE activity. Several chalcones were found to exhibit potent disaggregation of pre-formed N-biotinyl Aβ1-42 (bioAβ42) aggregates in vitro in the absence and presence of Cu2+/Zn2+, while others were effective at inhibiting the action of AChE.
