Solid State and Solution Characterization of Chiral, Conformationally Mobile Tripodal Ligands

Abstract

The synthesis of the ligands N,N-bis [(2-pyridyl)methyl]-1-(2-pyridyl)ethanamine (1, R-MeTPA), N,N-bis[(6-phenyl-2-pyridyl)methyl]-1-(2-pyridyl)ethanamine (2, R-MePh 2 TPA), N,N-bis[(2-quinolyl)methyl]-1-(2-pyridyl)ethanamine, (3, R-MeBQPA), and N,N-bis[(2-pyridyl)]methyl(phenyl)(2-pyridyl)methanamine (4, R-PhTPA) is described. The ligands form chiral, pseudo C 3 -symmetric complexes with Zn II and Cu II salts that possess an available electrophilic coordination site. X-ray crystallographic structures of the complexes [Zn(R-MeTPA)Cl](ClO 4 ), [Zn(RMeBQPA)Cl](ClO 4 ), and [Zn(R-PhTPA)Cl]( ClO 4 ) show that the spatial arrangement of the three pyridyl groups resembles a propeller whose directional sense is controlled by a substituent on one methylene arm. Chiroptical measurements provide supporting information that the complexes maintain similar structures in solution. Monte Carlo/stochastic dynamics (MC/SD) simulations of the [Zn(L)Cl] + complexes indicate that only two conformers are populated at normal temperatures, suggest the presence of a synchronicity in the movement of the heteroaromatic rings during conformer interconversions, and provide an estimate of the energy difference between the conformers.

Optimization of the Efficiency of Oxidation Catalysts Based on Iron Bispidine Complexes

“…Syntheses, Structural Properties, and Fe III/II Reduction Potentials Ligands L 2 and L 3 were prepared in good yields in analogy to L 1 [29] but by using the corresponding substituted picolylamine-derived building blocks, [30][31][32] and the corresponding iron complexes were obtained in analogy to those of L 1 . [33] Racemic samples were used for structural and electrochemical experiments as well as for the epoxidation reactions.…”

Synthesis and circular dichroism studies of N,N‐bis(2‐quinolylmethyl)amino acid Cu(II) complexes: Determination of absolute configuration and enantiomeric excess by the exciton coupling method

“…1) using solution, solid state, and computational methods. 12,31 Various primary amines were alkylated with two chromophores and com- N,N-BIS(2-QUINOLYLMETHYL)AMINO ACID plexation to Cu(II) created a conformationally rigid, asymmetric species featuring a helical configuration dictated by the absolute configuration of the chiral center. These studies have relied heavily upon ECCD, which can reveal the absolute sense of orientation of two or more chromophores in space.…”

Derivatization, complexation, and absolute configurational assignment of chiral primary amines: Application of exciton‐coupled circular dichroism

“…This geometry is different from that observed in our related work with tetradentate ligands where quinoline moieties normally occupy positions in the plane. 48 The net result of the present structure is that the two quinoline rings appear to be nearly coplanar, although they are actually out of plane by ∼6°. In this structure, the bulky phenyl substituent is directed up and away from the quinoline groups, with the methyl and hydrogen substituents pointing towards the quinolines.…”