540464-01-5Relevant academic research and scientific papers
Comparison of the electronic properties of diarylamido-based PNZ pincer ligands: Redox activity at the ligand and donor ability toward the metal
Davidson, Jillian J.,Demott, Jessica C.,Douvris, Christos,Fafard, Claudia M.,Bhuvanesh, Nattamai,Chen, Chun-Hsing,Herbert, David E.,Lee, Chun-I,McCulloch, Billy J.,Foxman, Bruce M.,Ozerov, Oleg V.
, p. 2916 - 2935 (2015/03/30)
This paper presents the synthesis and characterization of a series of pincer ligands and their Ni, Pd, Pt, and Rh complexes. The ligands under examination are based on a diarylamine which is modified either by two phosphino (-PR2) substituents in the ortho-positions (PNP ligands) or by a combination of a phosphino and an iminyl (?CH - NX) substituent (PNN ligands). The ligands can be broken down into three groups: (a) C2v-symmetric PNP ligands with identical side ?PR2 donors, (b) Cs-symmetric PNP? ligands with different ?PR2 side donors, and (c) PNN ligands containing a ?PiPr2 side donor. All of the ligands under study readily formed square-planar complexes of the types (PNZ)PdCl, (PNZ)Pd(OAc), and (PNZ)RhCO, where PNZ is the corresponding anionic tridentate pincer ligand. For select PNP ligands, (PNP)NiCl and (PNP)PtCl were also studied. The (PNZ)MCl complexes (M = Ni, Pd, Pt) underwent quasireversible oxidation in cyclic voltammetry experiments. Based on the close similarity of formal potentials for Ni, Pd, and Pt analogs, and based on the previous literature evidence, these oxidation events are ascribed primarily to the PNZ ligand, and the E1/2 values can be used to compare the ease of oxidation of different ligands. A (PNP)PdCl complex containing methoxy substituents para- to the central nitrogen underwent two quasireversible oxidations. Two mono-oxidized complexes were isolated and structurally characterized in comparison to their neutral analog, revealing minimal changes in the bond distances and angles. Several other neutral complexes were also structurally characterized. The carbonyl stretching frequency in (PNZ)RhCO complexes was used to gauge the donating ability of the various pincer ligands toward the metal. Comparison of E1/2 values for (PNZ)PdCl and ?CO values for (PNZ)RhCO revealed that the two are not consistently correlated across all the studied ligands and can be tuned to different degrees through judicious ligand alteration.
Para-phenylene-bridged spirobi(triarylamine) dimer with four perpendicularly linked redox-active π systems
Ito, Akihiro,Hata, Kazuhira,Kawamoto, Kensuke,Hirao, Yasukazu,Tanaka, Kazuyoshi,Shiro, Motoo,Furukawa, Ko,Kato, Tatsuhisa
experimental part, p. 10866 - 10878 (2010/12/24)
para-Phenylene-bridged spirobi(triarylamine) dimer 2, in which it conjugation through four redoxactive triarylamine subunits is partially segregated by the unique perpendicular conformation, was prepared and characterized by structural, electrochemical, and spectroscopic methods. Quantum chemical calculations (DFT and CASSCF) predicted that the frontier molecular orbitais of 2 are virtually fourfold degenerate, so that the oxidized states of 2 can give intriguing electronic and magnetic properties. In fact, the continuous-wave ESR spec-troscopy of radical cation 2.+ showed that the unpaired electron was trapped in the inner two redox-active dianisylamine subunits, and moreover was fully delocalized over them. Magnetic susceptibility measurements and pulsed ESR spectroscopy of the isolated salts of 2, which can be prepared by treatment with SbCl5, revealed that the generated tetracation 24+ decomposed mainly into a mixture of l) a decomposed tetra(radical cation) consisting of a tri(radical cation) moiety and a trianisylamine radical cation moiety (≈75%) and 2) a diamagnetic quinoid dication in a tetraanisyl-p-phenylendiamine moiety and two trianisylamine radical cation moieties (≈25%). Furthermore, the spin-quartet state of the tri(radical cation) moiety in the decomposed tetra(radical cation) was found to be in the ground state lying 30 cal mol-1 below the competing spindoublet state.
A spiro-fused triarylaminium radical cation with a triplet ground state
Ito, Akihiro,Urabe, Masashi,Tanaka, Kazuyoshi
, p. 921 - 924 (2007/10/03)
Novel spirobis(radical cation) 12+ was prepared to examine the magnetic interaction between the two radical centers. The dication 12+ was found to be a robust triplet diradical on the basis of the ESR spectrum, magnetic susceptibilit
