Enantiomerically Pure Trinuclear Helicates via Diastereoselective Self-Assembly and Characterization of Their Redox Chemistry

Abstract

A tris(bipyridine) ligand 1 with two BINOL (BINOL = 2,2'-dihydroxy-1,1'-binaphthyl) groups has been prepared in two enantiomerically pure forms. This ligand undergoes completely diastereoselective self-assembly into D2-symmeteric double-stranded trinuclear helicates upon coordination to copper(I) and silver(I) ions and to D3-symmetric triple-stranded trinuclear helicates upon coordination to copper(II), zinc(II), and iron(II) ions as demonstrated by mass spectrometry, NMR and CD spectroscopy in combination with quantum chemical calculations and X-ray diffraction analysis. According to the calculations, the single diastereomers that are formed during the self-assembly process are strongly preferred compared to the next stable diastereomers. Due to this strong preference, the self-assembly of the helicates from racemic 1 proceeds in a completely narcissistic self-sorting manner with an extraordinary high degree of self-sorting that proves the power and reliability of this approach to achieve high-fidelity diastereoselective self-assembly via chiral self-sorting to get access to stereochemically well-defined nanoscaled objects. Furthermore, mass spectrometric methods including electron capture dissociation MS(n) experiments could be used to elucidate the redox behavior of the copper helicates.

Enantiopure Alleno‐Acetylenic Helicages Containing Multiple Binding Sites

“…The 1 HNMR spectrum of (D 3 )-(P 6 )-4 consists of the same number of proton resonances as that of ligand (P 2 )-3,a ni ndication of a C 3 -symmetrica ssembly,e xcluding the formation of a" mesocate" or other nonsymmetrical structures ( Figure 2). [18] The pattern resembles that of the previously reported (D 2 )-(P 3 )-2. [12] In as imilarm anner,H h andH g are shiftedu pfield from d = 9.15 to 8.06 and 8.03 ppm, respectively,w hile protonH b is least affected, with as mall downfield shift of d = 0.15 ppm (Figure 2a,b).…”

Influencing the Self‐Sorting Behavior of [2.2]Paracyclophane‐Based Ligands by Introducing Isostructural Binding Motifs

“…Although the formation of helical polymeric structures from discrete cyclic structures, as observed in case of [(dppp)Pd{( S p )‐ L iso }] n (OTf) 2 n and [(dppp)Pd{( R p )‐ L nit }] n (OTf) 2 n , is in accordance with earlier observations and other self‐assembled polymers, the formation of bowl‐shaped, concave, yet polymeric, structures as observed in [(dppp) 2 Pd 2 {( S p )‐ L nit }{( R p )‐ L nit }] n (OTf) 4 n , is more scarce, both on the level of discrete supramolecular structures as well as on the level of self‐assembled polymers.…”

Linear and circular helicates: A brief review

“…Few higher nuclear triple stranded metallohelicates were also found. Few representative examples for triple-stranded metallohelicates [22][23][24][25][26] are reported.…”