Self‐Sorting Effects in the Self‐Assembly of Metallosupramolecular Rhombi from Chiral BINOL‐Derived Bis(pyridine) Ligands

Abstract

Four BINOL‐based bis(4‐pyridyl) ligands were synthesised in enantiopure and racemic form. These ligands form metallosupramolecular [(dppp)2M2L2] rhombi with cis‐protected [(dppp)Pd]2+ and [(dppp)Pt]2+ ions. In principle, racemic ligands can self‐assemble into three stereoisomeric rhombi. The degree of self‐sorting in the self‐assembly process crucially depends on the substitution pattern and the resulting bend angle of the V‐shaped ligands as well as the degree of steric crowding within the assembly when racemic ligands are used. Thus, these processes either lead to homochiral assemblies in a narcissistic self‐recognition manner, to heterochiral assemblies in a social self‐discriminating manner, or proceed in a nonselective fashion as evidenced by NMR spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction.

Self-assembly of metallosupramolecular rhombi from chiral concave 9,9’-spirobifluorene-derived bis(pyridine) ligands

“…Although these peak ratios suggest a slightly lower amplification of the homochiral assemblies by a factor of only two to three, this still reinforces our analysis – especially, if one takes into account that mass labelling in the periphery might cause differences in the ESI response factors that can cause slight deviations in the relative quantification of different components compared to the ratios obtained by other techniques, e.g. NMR spectroscopy, as we have recently reported [ 28 ].…”

“…So far we have studied templates based on the Tröger’s base [27] and the 2,2’-dihydroxybinaphthyl (BINOL) [28] scaffold and identified the bend angle of these V-shaped compounds to be a critical factor for the degree of self-sorting that can be achieved [9,15–18 25–28]. …”

“…As part of our ongoing programme to develop general guidelines for the diastereoselective self-assembly of metallosupramolecular aggregates, we have recently started a systematic study on the influence of rigid concave building blocks on the outcome of the self-assembly of bis(pyridine) ligands into dinuclear metallosupramolecular rhombi upon coordination to cis -protected [(dppp)Pd(OTf) 2 ] or [(dppp)Pt(OTf) 2 ] (dppp = 1,3-bis(diphenylphosphino)propane) complexes [ 27 – 28 ]. So far we have studied templates based on the Tröger’s base [ 27 ] and the 2,2’-dihydroxybinaphthyl (BINOL) [ 28 ] scaffold and identified the bend angle of these V-shaped compounds to be a critical factor for the degree of self-sorting that can be achieved [ 9 , 15 – 18 25 – 28 ].…”

Unexpected Self‐Assembly of a Homochiral Metallosupramolecular M4L4 Catenane

“…As part of our ongoing program to elucidate general guidelines for the (diastereoselective) self‐assembly of metallosupramolecular aggregates,2–6 we have recently started a systematic study on the influence of rigid chiral concave building blocks on the outcome of the self‐assembly of bis(pyridine) ligands and palladium(II) and platinum(II) ions in the sense of chiral self‐sorting 4. 5 Cis ‐protected [(dppp)Pd(OTf) 2 ] or [(dppp)Pt(OTf) 2 ] (dppp=1,3‐bis(diphenylphosphino)propane) complexes, for example, self‐assembled into dinuclear metallosupramolecular rhombi upon coordination to bis(pyridine) ligands based on Tröger’s base,4d,e the 2,2′‐dihydroxy‐binaphthyl,4f and the 9,9′‐spirobifluorene scaffold 4g…”

Chiral Self‐Sorting of trans‐Chelating Chiral Ligands upon Formation of PdII Complexes

“…However, for some dinuclear complexes the spectra of the heterochiral and homochiral diastereomers are almost identical 4e. Hence, we wanted to get additional independent evidence by another analytical method.…”