Chiral bisphosphine Ph-BPE ligand: a rising star in asymmetric synthesis.

Chiral 1,2-bis(2,5-diphenylphospholano)ethane (Ph-BPE) is a class of optimal organic bisphosphine ligands with C2-symmetry. Ph-BPE with its excellent catalytic performance in asymmetric synthesis has attracted much attention of chemists with increasing popularity and is growing into one of the most commonly used organophosphorus ligands, especially in asymmetric catalysis. Over two hundred examples have been reported since 2012. This review presents how Ph-BPE is utilized in asymmetric synthesis and how powerful it is as a chiral ligand or even a catalyst in a wide range of reactions including applications in the total synthesis of bioactive molecules.

Enhanced Four-Electron Oxygen Reduction Selectivity of Clamp-Shaped Cobalt(II) Porphyrin(2.1.2.1) Complexes.

The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two CoII porphyrin(2.1.2.1) complexes bearing Ph or F5 Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered CoII /CoIII process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e- ORR pathway giving H2 O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e- ORR as compared to the 2e- pathway, consistent with experimental data.

Synthesis, Characterization, and Electrochemistry of Copper Dibenzoporphyrin(2.1.2.1) Complexes.

Three copper dibenzoporphyrin(2.1.2.1) complexes having two dipyrromethene units connected through o-phenylen bridges and 4-MePh, Ph, or F5Ph substituents at the meso positions of the dipyrrins were synthesized and characterized according to their spectral, electrochemical, and structural properties. As indicated by the single-crystal X-ray structures, all three derivatives have highly bent molecular structures, with angles between each planar dipyrrin unit ranging from 89° to 85°, indicative of a nonaromatic molecule. The insertion of copper(II) into dibenzoporphyrins(2.1.2.1) induced a change in the macrocyclic cavity shape from rectangular in the case of the free-base precursors to approximately square for the metalated copper derivatives. Solution electron paramagnetic resonance (EPR) spectra at 100 K showed hyperfine coupling of the Cu(II) central metal ion and the N nucleus in the highly bent molecular structures. Electrochemical measurements in CH2Cl2 or N,N-dimethylformamide (DMF) containing 0.1 M tetrabutylammonium perchlorate (TBAP) were consistent with ring-centered electron transfers and, in the case of reduction, were assigned to electron additions involving two equivalent π centers on the bent nonaromatic molecule. The potential separation between the two reversible one-electron reductions ranged from 230 to 400 mV in DMF, indicating a moderate-to-strong interaction between the equivalent redox-active dipyrrin units of the dibenzoporphyrins(2.1.2.1). The experimentally measured highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps ranged from 2.14 to 2.04 eV and were smaller than those seen for the planar copper tetraarylporphyrins(1.1.1.1), (Ar)4PCu.

Binuclear Rhodium(I) Complex of a Dimethylvinylene-Bridged Distorted Hexaphyrin(2.1.2.1.2.1).

A highly distorted binuclear rhodium(I) complex, 2Rh, was successfully synthesized from hexaphyrin(2.1.2.1.2.1) containing dimethylvinylene-bridges between dipyrrin units. IR spectroscopy, 1H NMR spectroscopy, and X-ray crystallography revealed that the complex 2Rh consists of two rhodium(I) ions coordinated to two dipyrrin units. Rh complexation induced a transformation from a trans-/cis-/trans- to trans-/cis-/cis-conformation on the dimethylvinylene-bridges. This is the first example of rhodium(I)-ion-induced cis-/trans-isomerization in the porphyrin derivatives. Theoretical calculations of 2Rh predicted the presence of intramolecular charge-transfer absorption due to the distorted molecular structure.

Complexation study of a 1,3-phenylene-bridged cyclic hexa-naphthalene with fullerenes C60 and C70 in solution and 1D-alignment of fullerenes in the crystals.

To investigate the host ability of a simple macrocycle, 1,3-phenylene-bridged naphthalene hexamer N6, we evaluated the complexation of N6 with fullerenes in toluene and in the crystals. The complexes in the solid-state demonstrate the one-dimensional alignment of fullerenes. The single-crystals of the C60@N6 composite have semiconductive properties revealed by photoconductivity measurements.

A porphyrin(2.1.2.1) bis-boron complex as a deep-red AIE luminophore induced by intermolecular F-π interaction.

Mono-/diboron complexes with saddle-shaped molecular conformations were synthesized from porphyrins(2.1.2.1). The boron complexes have unique structure-dependent photophysical properties: (a) monoboron complexes 2a and 2b are not emissive in solution and the solid state, (b) diboron complex 3a shows red emission in toluene, and (c) diboron complex 3b shows aggregation-induced emission (AIE) in the deep-red region due to intermolecular secondary interactions (F-π). This is the first case of a boron porphyrinoid complex that shows AIE emission in the deep-red region in decades.

Porphyrin(2.1.2.1) as a novel binucleating ligand: synthesis and molecular structures of mono- and di-rhodium(I) complexes.

The first example of monovalent and bimetallic porphyrins(2.1.2.1), the rhodium(I) complex of porphyrin(2.1.2.1), was readily obtained under controlled conditions. The coordinated rhodium(I) drastically influenced the molecular structure and optical and electronic properties. Our results clearly demonstrate that porphyrin(2.1.2.1) could be developed as a new binucleating ligand for the fabrication of bimetallic complexes.

1,3-Phenylene-bridged naphthalene wheels synthesized by one-pot Suzuki-Miyaura coupling and the complex of the hexamer with C60.

A large 1,3-phenylene-bridged hexameric naphthalene wheel N6 and a heptameric wheel N7 were synthesized simply by Suzuki-Miyaura coupling via one-pot reaction from monomers. We could control the distribution of N6 and N7via the reaction conditions. The hexameric wheel structure was revealed by X-ray diffraction analysis. The wheel N6 exhibited C60 encapsulation ability in the solid state, which was also confirmed by single crystal X-ray analysis.