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Relevant academic research and scientific papers

The first helical-chiral phosphane ligands: rac-[5]- and rac-[6]-heliphos

The syntheses of two helical, chiral phosphanes in their racemic forms are described. Their helicene backbone was built up using an improved photocyclization approach. The phosphorus functionalities were introduced in the last step. Up to now, separation of the enantiomers of the helicene phosphanes could be achieved analytically but not on a preparative scale.

Synthesis of Conjugated Helical Acetylene-Bridged Polymers and Cyclophanes

Pd(0)-catalyzed reactions of 2,15-diethynyl[6]helicene with derivatives of p- and o-diiodobenzene give, respectively, polymers 4 and cyclophanes 5, in which helicenes are linked by diethynylbenzenes. Both are very soluble in many common solvents. The molar rotation of polymer 4 is greater than that of monomeric analogue 12, and peaks in its UV and CD spectra at wavelengths greater than 350 nm are shifted to the red of those in 12. Cyclophane 5a, which contains two helicene rings, could be isolated from the reaction mixture in pure form. Its maxima in the UV and CD spectra are not shifted to the red of those of 12, most likely because the two helicene rings in 5a are twisted with respect to one another.

Circularly Polarized Luminescence of [6]Helicenes through Excited-State Intramolecular Proton Transfer

We present the concept of combining circularly polarized luminescence (CPL) and excited-state intramolecular proton transfer (ESIPT) features into a single molecule as a strategy to generate high-performance ESIPT-based CPL materials. For this purpose, a [6]helicene bearing two ESIPT structural units was synthesized using a double Suzuki–Miyaura reaction and a double C(sp2)?H hydroxylation approach. The photophysical properties of the doubly hydroxylated [6]helicene were studied in parallel with a non-hydroxylated [6]helicene control compound, revealing that the presence of a chiral [6]helicene unit results in a strong CPL response and the presence of the ESIPT units in a considerable red shift. The red-shifted emission along with the outstanding glum (≈10?2) and a large Stokes shift makes the doubly hydroxylated [6]helicene a promising candidate for use in optoelectronics.

Chiral Self-Discrimination and Guest Recognition in Helicene-Based Coordination Cages

Chiral nanosized confinements play a major role for enantioselective recognition and reaction control in biological systems. Supramolecular self-assembly gives access to artificial mimics with tunable sizes and properties. Herein, a new family of [Pd2L4] coordination cages based on a chiral [6]helicene backbone is introduced. A racemic mixture of the bis-monodentate pyridyl ligand L1 selectively assembles with PdII cations under chiral self-discrimination to an achiral meso cage, cis-[Pd2L1P2L1M2]. Enantiopure L1 forms homochiral cages [Pd2L1P/M4]. A longer derivative L2 forms chiral cages [Pd2L2P/M4] with larger cavities, which bind optical isomers of chiral guests with different affinities. Owing to its distinct chiroptical properties, this cage can distinguish non-chiral guests of different lengths, as they were found to squeeze or elongate the cavity under modulation of the helical pitch of the helicenes. The CD spectroscopic results were supported by ion mobility mass spectrometry.

First enantioselective catalysis using a helical diphosphane

The synthesis of 2,15-bis(diphenylphosphino)-hexahelicene (PHelix) in enantiomerically pure form and its use as a helical ligand for enantioselective rhodiumcatalyzed hydrogenation are described.

Synthesis and Chiral Recognition of Optically Active Crown Ethers incorporating a Helicene Moiety as the Chiral Centre

The synthesis of optically active crown ethers (8), (14), and (18) incorporating helicene molecular frameworks is reported.Their chiral recognition properties have been examined and show that (M)-(-)-(14), although of the same helicity as (M)-(-)-(8) and

Synthesis and Chiral Recognition of Novel Crown Ethers incorporating Helicene Chiral Centres

Two novel optically active crown ethers (7) and (14) incorporating helicene molecular frameworks were prepared, and their chiral recognition properties were examined to show that (M)-(-)-(7) and (M)-(-)-(14) had opposite chiral recognition for the transpo