142946-79-0Relevant academic research and scientific papers
Synthesis of bis(trifluoromethyl)-2,2'-bipyridines by nickel catalysed homocoupling reactions
Chan,Tse
, p. 1929 - 1934 (1993)
Bis(trifluoromethyl)-2,2'-bipyridines have been synthesized in moderate yields by nickel or palladium catalysed homocoupling of 2-chloro-(trifluoromethyl)pyridines.
Picosecond dynamics of nonthermalized excited states in tris(2,2-bipyridine)ruthenium(II) derivatives elucidated by high energy excitation
McFarland, Sherri A.,Lee, Felix S.,Cheng, Karen A. W. Y.,Cozens, Frances L.,Schepp, Norman P.
, p. 7065 - 7070 (2005)
The picosecond excited-state dynamics of several derivatives have been investigated using high photon energy excitation combined with picosecond luminescence detection. Instrument response-limited fluorescence (τ1 ≈ 3-5 ps) at 500 nm was observed for all of the complexes, while longer-lived emission (τ2 > 50 ps), similar in energy, was observed for only some of the complexes. Interestingly, the presence of τ2 required substitution at the 4,4-positions of the bipyridine ligands and D3 symmetry for the complex; only the 4,4-substituted homoleptic complexes exhibited τ2. On the basis of previous assignments of the ultrafast dynamics measured for Ru(bpy)3 2+ and Ru(dmb)32+, τ2 has been tentatively ascribed to relaxation from higher electronic or vibrational levels in the triplet manifold having slightly more triplet character than the state responsible for τ1. However, given that the kinetics for these transition metal complexes are highly dependent on both pump and probe wavelengths and that there is considerable interest in utilizing such complexes for electron transfer in the nonergodic limit, further characterization of the state giving rise to τ2 is warranted.
Photoacidic and Photobasic Behavior of Transition Metal Compounds with Carboxylic Acid Group(s)
O'Donnell, Ryan M.,Sampaio, Renato N.,Li, Guocan,Johansson, Patrik G.,Ward, Cassandra L.,Meyer, Gerald J.
, p. 3891 - 3903 (2016)
Excited state proton transfer studies of six Ru polypyridyl compounds with carboxylic acid/carboxylate group(s) revealed that some were photoacids and some were photobases. The compounds [RuII(btfmb)2(LL)]2+, [RuII(dtb)2(LL)]2+, and [RuII(bpy)2(LL)]2+, where bpy is 2,2′-bipyridine, btfmb is 4,4′-(CF3)2-bpy, and dtb is 4,4′-((CH3)3C)2-bpy, and LL is either dcb = 4,4′-(CO2H)2-bpy or mcb = 4-(CO2H),4′-(CO2Et)-2,2′-bpy, were synthesized and characterized. The compounds exhibited intense metal-to-ligand charge-transfer (MLCT) absorption bands in the visible region and room temperature photoluminescence (PL) with long τ > 100 ns excited state lifetimes. The mcb compounds had very similar ground state pKa's of 2.31 ± 0.07, and their characterization enabled accurate determination of the two pKa values for the commonly utilized dcb ligand, pKa1 = 2.1 ± 0.1 and pKa2 = 3.0 ± 0.2. Compounds with the btfmb ligand were photoacidic, and the other compounds were photobasic. Transient absorption spectra indicated that btfmb compounds displayed a [RuIII(btfmb-)L2]2+? localized excited state and a [RuIII(dcb-)L2]2+? formulation for all the other excited states. Time dependent PL spectral shifts provided the first kinetic data for excited state proton transfer in a transition metal compound. PL titrations, thermochemical cycles, and kinetic analysis (for the mcb compounds) provided self-consistent pKa? values. The ability to make a single ionizable group photobasic or photoacidic through ligand design was unprecedented and was understood based on the orientation of the lowest-lying MLCT excited state dipole relative to the ligand that contained the carboxylic acid group(s).
Synthesis and Characterization of a Series of Bis-homoleptic Cycloruthenates with Terdentate Ligands as a Family of Panchromatic Dyes
Rees, Thomas W.,Liao, Jinfeng,Sinopoli, Alessandro,Male, Louise,Calogero, Giuseppe,Curchod, Basile F.E.,Baranoff, Etienne
, p. 9903 - 9912 (2017)
A series of six homoleptic bis-cyclometalated ruthenium complexes, Ru(N^N^C)2, is reported where N^N^C is a 6-(2,4-difluoro-3-R3-phenyl)-4-R2-4′-R1-2,2′-bipyridine with R3 = -H or -CF3 and R2 and R1 = -COOEt or -CF3. An effective synthesis of the ligands and the complexes is described. The UV-visible absorption studies demonstrate that these complexes are panchromatic dyes absorbing up to 900 nm. Importantly, the onset of absorption depends only on the substitution on the metalated phenyl, whereas the intensity of absorption throughout the spectra is a function of substituents on both the phenyl and the bipyridine moieties. The same trend is observed in electrochemistry as the redox gap depends only on the substitution on the metalated phenyl, whereas the oxidation and reduction potentials are a function of substituents on both the phenyl and the bipyridine moieties. Preliminary tests as sensitizer for dye-sensitized solar cells demonstrate that the number of anchoring groups on the dye has a major influence on the device efficiency.
Improved synthesis of electron deficient bipyridines
Li, Hao,Oppenheimer, Jossian,Smith, Milton R.,Maleczka, Robert E.
, p. 2231 - 2232 (2016)
Symmetric bipyridines commonly serve as ligands for various types of catalytic processes. Nickel catalyzed Ullmann couplings are often used to prepare such bipyridines, however for electron deficient substrates low conversions and/or yields are often reported. We herein report an improved synthesis of trifluoromethyl substituted bipyridines using stoichiometric amounts of Zn(0), NiCl2·6H2O, and Ph3P. This modified procedure enables a >20 fold improvement over the previously reported yield for the synthesis of 4,4′,5,5′-tetrakis(trifluoromethyl)-2,2′-bipyridine.
Nonthermalized excited states in Ru(ll) polypyridyl complexes probed by ultrafast transient absorption spectroscopy with high photon energy excitation
McFarland, Sherri A.,Cheng, Karen A. W. Y.,Lee, Felix S.,Cozens, Frances L.,Schepp, Norman P.
, p. 1118 - 1125 (2008)
The picosecond excited state dynamics of a series of homoleptic Ru(II) polypyridyl complexes (where LL = bpy, dmb, dmeob, dfmb, or dttb) have been investigated in aqueous solution at room temperature using femtosecond transient absorption spectroscopy with high photon energy excitation. All of the complexes studied produced similar spectroscopic signatures: a near-instantaneous bleach centered at 470-500 nm corresponding to the static absorption spectrum, as well as an intense absorption (475-650 nm) that decayed within the instrument response function (IRF) to form a broad, low-level absorption extending from 500-650 nm. Detailed analyses of both kinetic and spectral parameters by singular value decomposition (SVD) indicate that the excited state difference spectra contain contributions from at least three distinguishable species that have been assigned as ligand-based Π* ← Π* and ligand-to-metal-charge-transfer (LMCT) transitions concomitant with the loss of the ground state metal-to-ligand-charge-transfer (MLCT) transition. Kinetic information extracted at 530 nm (an optical marker for the fully intraligand-delocalized 3MLCT state) or 660 nm (LMCT transitions) appear to be biphasic in some cases with the amplitude of the IRF-limited component becoming larger with shorter wavelength excitation. Further, rise dynamics were observed at redder probe wavelengths for Ru(bpy)32+ and Ru(dttb)32+. These observations are different from those obtained using lower photon energy excitation and show that excitation wavelength strongly influences the early photophysical events in these Ru(II) complexes.
Structural and spectroscopic studies of reduced [Re(bpy-R)(CO) 3]-1 species relevant to CO2 reduction
Benson, Eric E.,Grice, Kyle A.,Smieja, Jonathan M.,Kubiak, Clifford P.
, p. 229 - 234 (2013)
Spectroscopic and structural comparisons are made between the rhenium anions with bpy-R ligands spanning a wide range of electron-withdrawing and donating abilities (R = CF3, H, Me, tBu, OMe). The synthesis and characterization of the rhenium anions [Re(bpy-R)(CO)3]-1 (bpy-R = 4,4′-disubstitued- 2,2′-bipyridine; R = CF3, Me, OMe) are reported. The anions [Re(bpy-R)(CO)3]1 (R = Me and OMe) were structurally characterized. X-ray characterization of [Re(bpy-CF3)(CO)3]-1 was unsuccessful. However, the structure of a mono-reduced complex, [Re(bpy-CF3)(CO) 3Cl][K(18-crown-6)] was obtained. This compound is a rare example of a structurally characterized 19e- intermediate formed in the chemical and electrochemical reduction of a Re(bpy-R)(CO)3Cl species.
Frontier orbitals of photosubstitutionally active ruthenium complexes: An experimental study of the spectator ligands' electronic properties influence on photoreactivity
Jang, Hyo Jin,Hopkins, Samantha L.,Siegler, Maxime A.,Bonnet, Sylvestre
, p. 9969 - 9980 (2017)
The synthesis and characterization of [Ru(tpy)(R2bpy)(L)](X)n complexes (tpy = 2,2′:6′,2′′-terpyridine, R2bpy = 4,4′-dimethyl-2,2′-bipyridine (dmbpy), or 4,4′-bis(trifluoromethyl)-2,2′-bipyridine (tfmbpy), X = Cl- or PF6-, and n = 1 or 2) are described. The dmbpy and tfmbpy bidentate ligands allow for investigating the effects of electron-donating and electron-withdrawing ligands, respectively, on the frontier orbital energetics as well as the photoreactivity of these ruthenium polypyridyl complexes for five prototypical monodentate ligands L = Cl-, H2O, CH3CN, 2-(methylthio)ethanol (Hmte), or pyridine. According to spectroscopic and electrochemical studies, the dmbpy analogues displayed a singlet metal-to-ligand charge transfer (1MLCT) transition at higher energy than the tfmbpy analogues. The shift of the 1MLCT to higher energy results from the lowest unoccupied molecular orbital (LUMO) for the dmbpy analogues being tpy-based, whereas for the tfmbpy analogues orbital inversion occurs resulting in a tfmbpy-based LUMO. The energy level of the highest occupied molecular orbital (HOMO) was considerably affected by the nature of the monodentate ligand. Visible light irradiation of the complexes demonstrated that the tfmbpy analogue increased the rate and quantum yields of photosubstitution reactions, compared to the dmbpy analogue, suggesting that the electron-withdrawing substituents allowed better thermal accessibility of the triplet metal-centered (3MC) state from the photochemically generated triplet metal-to-ligand charge transfer (3MLCT) excited state. A correlation between the photolability of the monodentate ligands and the electrochemical reversibility of the metal-based oxidation is also reported.
A Systematic Study of the Effects of Complex Structure on Aryl Iodide Oxidative Addition at Bipyridyl-Ligated Gold(I) Centers
Bower, John F.,Cadge, Jamie A.,Russell, Christopher A.
supporting information, p. 24976 - 24983 (2021/10/20)
A combined theoretical and experimental approach has been used to study the unusual mechanism of oxidative addition of aryl iodides to [bipyAu(C2H4)]+ complexes. The modular nature of this system allowed a systematic assessment of the effects of complex structure. Computational comparisons between cationic gold and the isolobal (neutral) Pd0 and Pt0 complexes revealed similar mechanistic features, but with oxidative addition being significantly favored for the group 10 metals. Further differences between Au and Pd were seen in experimental studies: studying reaction rates as a function of electronic and steric properties showed that ligands bearing more electron-poor functionality increase the rate of oxidative addition; in a complementary way, electron-rich aryl iodides give faster rates. This divergence in mechanism compared to Pd suggests that Ar?X oxidative addition with Au can underpin a broad range of new or complementary transformations.
Convergent access to bis-1,2,4-triazinyl-2,2′-bipyridines (BTBPs) and 2,2′-bipyridines: Via a Pd-catalyzed Ullman-type reaction
Carrick, Jesse D.,Waters, Gabrielle D.
, p. 10807 - 10815 (2020/03/27)
Multidentate, soft-Lewis basic, complexant scaffolds have displayed significant potential in the discrete speciation of the minor actinides from the neutron-absorbing lanthanides resident in spent nuclear fuel. Efforts to devise convergent synthetic strategies to targets of interest to improve liquid-liquid separation outcomes continue, but significant challenges to improve solubility in process-relevant diluents to effectively define meaningful structure-activity relationships remain. In the current work, a synthetic method to achieve the challenging 2,2′-bipyridine bond of the bis-1,2,4-triazinyl-2,2′-bipyridine (BTBP) complexant class leveraging a Pd-catalyzed Ullman-type coupling is reported. This convergent strategy improves upon earlier work focused on linear synthetic access to the BTBP complexant moiety. Method optimization, relevant substrate scope and application, as well as a preliminary mechanistic interrogation are reported herein.
