Predictions, Synthetic Strategy, and Isolation of a Linear Tetrametallic Triple‐Stranded Lanthanide Helicate

Abstract

Liganden, die sich winden: In Einklang mit thermodynamischen Rechnungen liegt das Tripelhelicat [Ln4L3]12+ mit vier Lanthanoidionen (siehe Bild) – trotz seiner hohen positiven Ladung – bei millimolaren Konzentrationen in Lösung als Hauptspezies vor. Für den Europiumkomplex wurde diese nanometergroße tripelhelicale Struktur im Festkörper etabliert.

Linear Polynuclear Helicates as a Link between Discrete Supramolecular Complexes and Programmed Infinite Polymetallic Chains

“…[15] We note that the apparent intermetallic repulsion DE , e r % 1.0). [14] This deviation is mainly due to the contribution of solvation to the intermetallic interactions, which can be estimated with a Born-Haber cycle involving the solvation energies obtained with Born equation for the complexes [Eu(L3) 3 …”

“…The agreement between experimental and re-calculated con- [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] www.chemeurj.org stants ( Table 3, 12 + (Figure 8 and Figure S4, Supporting Information) systematically display 39 signals, which confirm the exclusive formation of the D 3 -symmetrical triple-stranded helicates at millimolar concentrations. [15] The diagnostic downfield shifts of protons H3, H9 and H12 in the fast-relaxing paramagnetic [Eu 4 (L4) 3 ] 12 + helicate points to the existence of a tight triple-stranded helix, [10] while the detailed analysis of two-dimensional COSY-, NOESY-, ROESY-NMR spectra allows the complete assignement of the 39 signals for the Table S1, Supporting Information). [15] The crystal structure of [Eu 4 (L4) 3 ] 12 + unambiguously confirms the formation of the tetranuclear triple-stranded helicate (Figure 3), characterized by an almost linear arrangement of the metals (a Eu1···Eu2···Eu3 170.71(1)8, a Eu2···Eu3···Eu4 172.03(1)8) combined with their regular spacing along the helical axis (Eu1···Eu2 9.312(1) , Eu2···Eu3 9.054(1) , Eu3···Eu4 9.405(1) , average Eu···Eu 9.26(18) ).…”

“…The simultaneous multi-linear least-squares fit of the twelve experimental formation constants collected for the helicates [Eu m (Lk) n ] 3m + (k = 1-4, Table 1, column 2) with Equation (15) gives log(K inter ) = 4.93 and log(K intra ) = 1.65. The agreement between experimental and re-calculated con- [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] log(b Eu,Lk m,n,calcd ) [b] www.chemeurj.org stants ( Table 3, 12 + (Figure 8 and Figure S4, Supporting Information) systematically display 39 signals, which confirm the exclusive formation of the D 3 -symmetrical triple-stranded helicates at millimolar concentrations.…”

“…The syntheses of the ligand L4 and of its complexes [Ln 4 (L4) 3 ]-A C H T U N G T R E N N U N G (CF 3 SO 3 ) 12 , and the crystal structure of [Eu 4 (L4) 3 ] 12 + have been described in a preliminary communication. [15] Results and Discussion…”

“…3 ] 12 + (average 9.26 (18) ). [15] For the rigid assembly in question, a standard Coulombic approach predicts ln(u EuEu ) / -const/d, [14] which leads to u 0.33 , because the metals are regularly spaced along the strand. Finally, the interligand interaction u LL is restricted to operate between two sites bound to the same metal.…”