- A New Class of Lanthanide Complexes with Three Ligand Centered Radicals: NMR Evaluation of Ligand Field Energy Splitting and Magnetic Coupling
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Combination of three radical anionic Ph-BIAN ligands (Ph-BIAN=bis-(phenylimino)-acenaphthenequinone) with lanthanoid ions leads to a series of homoleptic, six-coordinate complexes of the type Ln(Ph-BIAN)3. Magnetic coupling data were measured by paramagnetic solution NMR spectroscopy. Combining 1H NMR with 2H NMR of partially deuterated compounds allowed a detailed study of the magnetic susceptibility anisotropies over a large temperature range. The observed chemical shifts were separated into ligand- and metal-centered contributions by comparison with the Y analogue (diamagnetic at the metal). The metal-centered contributions of the complexes with the paramagnetic ions could then be separated into pseudocontact and Fermi contact shifts. The latter is large within the Ph-BIAN scaffold, which shows that magnetic coupling is significant between the lanthanide ion and the radical ligand. Pseudocontact shifts were further correlated to structural data obtained from X-ray diffraction experiments. Ligand-field parameters were determined by fitting the temperature dependence of the observed magnetic susceptibility anisotropies. The electronic structure determined by this approach shows, that the Er and Tm analogues are candidates for single molecule magnets (SMM). These results demonstrate the possibilities for the application of NMR spectroscopy in investigations of paramagnetic systems in general and single molecule magnets in particular.
- Hiller, Markus,Sittel, Thomas,Wadepohl, Hubert,Enders, Markus
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- A Visible-Light-Harvesting Covalent Organic Framework Bearing Single Nickel Sites as a Highly Efficient Sulfur–Carbon Cross-Coupling Dual Catalyst
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Covalent Organic Frameworks (COFs) have recently emerged as light-harvesting devices, as well as elegant heterogeneous catalysts. The combination of these two properties into a dual catalyst has not yet been explored. We report a new photosensitive triazine-based COF, decorated with single Ni sites to form a dual catalyst. This crystalline and highly porous catalyst shows excellent catalytic performance in the visible-light-driven catalytic sulfur–carbon cross-coupling reaction. Incorporation of single transition metal sites in a photosensitive COF scaffold with two-component synergistic catalyst in organic transformation is demonstrated for the first time.
- Chen, Hui,Liu, Wanlu,Laemont, Andreas,Krishnaraj, Chidharth,Feng, Xiao,Rohman, Fadli,Meledina, Maria,Zhang, Qiqi,Van Deun, Rik,Leus, Karen,Van Der Voort, Pascal
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supporting information
p. 10820 - 10827
(2021/04/09)
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- Synthesis, characterization of zinc complexes with neutral α-diimine ligands and application in ring-opening polymerization of σ-caprolactone
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A series of neutral α-diimine ligands with diacetyl and acenaphthenequinone skeletons were prepared by the reaction between diacetyl and the corresponding aromatic amine. These ligands reacted with ZnCl2 to generate symmetric α-diimine zinc complexes C1-C
- Wang, Xiaodan,Liu, Xuehong,Huang, Ju
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p. 773 - 776
(2017/12/08)
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- Novel yttrium and zirconium catalysts featuring reduced Ar-BIANH2 ligands for olefin hydroamination (Ar-BIANH2 = bis-arylaminoacenaphthylene)
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The novel class of bis-arylaminoacenaphthylenes (Ar-BIANH2) was employed for the preparation of zirconium and yttrium complexes to be used as catalysts for cyclohydroamination of a number of primary and secondary aminoalkenes. The complex [(2,6
- Cimino, Alessandro,Moscatelli, Filippo,Ferretti, Francesco,Ragaini, Fabio,Germain, Stéphane,Hannedouche, Jér?me,Schulz, Emmanuelle,Luconi, Lapo,Rossin, Andrea,Giambastiani, Giuliano
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supporting information
p. 10285 - 10293
(2016/12/07)
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- Cationic platinum(II) complexes bearing aryl-BIAN ligands: Synthesis and structural and optoelectronic characterization
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Five cationic platinum(II) complexes bearing a 2-(3′-substituted aryl)pyridine cyclometalating ligand (C^N) and a neutral Ar-BIAN ligand have been synthesized: [Pt(ppy)(PhBIAN)]PF6 (1), [Pt(3Fppy)(PhBIAN)]PF6 (2), [Pt(3MeOppy)(PhBIAN)]PF6 (3), [Pt(3MeOppy)(4-FPhBIAN)]PF6 (4), [Pt(ppy)(4-MeOPhBIAN)]PF6 (5). All complexes have been characterized by NMR spectroscopy and mass spectrometry. Complexes 2 and 3 have been characterized by X-ray crystallography. Structure-property relationships were established from UV-visible spectroscopy and cyclic voltammetry studies. Interestingly, we found that when both the C^N and the Aryl-BIAN ligands contained electron-donating MeO groups the absorption spectrum for the platinum complex extended out to 650 nm. The electrochemical studies of these complexes established that they are electronically compatible dye molecules for dye-sensitized solar cells.
- Obrien, Cameron,Wong, Michael Yin,Cordes, David B.,Slawin, Alexandra M. Z.,Zysman-Colman, Eli
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- Vanadyl cationic complexes as catalysts in olefin oxidation
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Three new mononuclear oxovanadium(iv) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol-1V h-1) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol-1V h-1) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal CC bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)]+ (1+) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(iv) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)]+ complex is the likely active V(iv) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium. This journal is
- Nunes, Carla D.,Vaz, Pedro D.,Félix, Vítor,Veiros, Luis F.,Moniz, Tania,Rangel, Maria,Realista, Sara,Mourato, Ana C.,Calhorda, Maria José
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p. 5125 - 5138
(2015/03/18)
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- Enlarging the π system of phosphorescent (C^C*) cyclometalated platinum(II) NHC complexes
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Cyclometalated (C^C*) platinum(II) N-heterocyclic carbene (NHC) complexes are emerging as a new class of phosphorescent emitters for the application in organic light-emitting devices (OLEDs). We present the synthesis of six new complexes of this class to
- Tronnier, Alexander,Poethig, Alexander,Metz, Stefan,Wagenblast, Gerhard,Muenster, Ingo,Strassner, Thomas
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p. 6346 - 6356
(2014/07/07)
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- Mild negishi cross-coupling reactions catalyzed by acenaphthoimidazolylidene palladium complexes at low catalyst loadings
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Considering that the strong σ-donor property of ylidenes derived from π-extended imidazolium salts is conducive to increasing the catalytic activity of the resulting palladium N-heterocyclic carbene complexes, robust acenaphthoimidazol-ylidene palladium complexes 3a-c with varying bulky substituted groups were prepared from the corresponding acenaphthoimidazolium chlorides by heating with PdCl2 and K2CO3 in neat 3-chloropyridine in satisfactory yields. Even at a catalyst loading as low as 0.25 mol %, complex 3a exhibited extremely high catalytic activity toward Negishi cross-coupling of alkylzinc reagents with a wide range of (hetero)aryl halides under mild reaction conditions within 30 min. Besides a great number of bromoarenes, various less expensive and inactive (hetero)aryl chlorides were coupled successfully with the alkyl- and arylzinc reagents, in which active functional groups (such as -NH2) were well tolerated even in one-pot dicoupling transformations without protection. In addition, in the case of coupling with secondary alkylzinc reagents, undesired β-hydride elimination leading to isomerized linear products was efficaciously suppressed. The catalyst system also displayed superiority in the construction of heterobiaryls through the coupling of heteroarylzinc reagents and heterocylic chloroarenes which were hardly accessible from the corresponding organoboron reagents by Suzuki-coupling reactions. Therefore, the protocol described in this paper represents a mild, general, and scalable approach to access various structurally intriguing and functionalized (hetero)aryls.
- Liu, Zelong,Dong, Ningning,Xu, Mizhi,Sun, Zheming,Tu, Tao
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p. 7436 - 7444
(2013/09/02)
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- Robust acenaphthoimidazolylidene palladium complexes: Highly efficient catalysts for suzuki-miyaura couplings with sterically hindered substrates
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Robust acenaphthoimidazolylidene palladium complexes have been demonstrated as highly efficient and general catalysts for the sterically hindered Suzuki-Miyaura cross-coupling reactions in excellent yields even with low catalyst loadings under mild reaction conditions. The high catalytic activity of these complexes highlights that, besides the "flexible steric bulky" concept, σ-donor properties of the NHC ligands are also crucial to accelerate the transformations.
- Tu, Tao,Sun, Zheming,Fang, Weiwei,Xu, Mizhi,Zhou, Yunfei
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supporting information; experimental part
p. 4250 - 4253
(2012/10/07)
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- The use of sublimable chlorotricarbonyl bis(phenylimino)acenaphthene rhenium(I) complexes as photosensitizers in bulk-heterojunction photovoltaic devices
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A series of sublimable substituted chlorotricarbonyl bis(phenylimino)acenaphthene rhenium(I) complexes was synthesized and used in the fabrication of photovoltaic devices. The hole and electron carrier mobilities of these complexes are in the order of 10-3 to 10-4 cm2 V-1 s-1. Heterojunction devices with CuPc/complex/C60 (CuPc = copper phthalocyanine) as the active layer and bulk heterojunction devices with complex:C60 as the active layer were fabricated. The rhenium complexes function as photosensitizer in the devices, and exhibit optical absorption in the region between 500 and 550 nm within which other components in the device do not absorb. Other devices with hole transport materials, exciton blocking materials, and different active layer thickness were also fabricated. Variation of substitution groups in the ligand did not show significant difference in device performance. The best power conversion efficiency of the devices was measured to be 1.29% under illumination of AM1.5 simulated solar light.
- Mak, Chris S.K.,Wong, Hei Ling,Leung, Qing Yun,Tam, Wing Yan,Chan, Wai Kin,Djuri?i?, Aleksandra B.
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experimental part
p. 2770 - 2776
(2009/12/06)
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