Generation of a dynamic system of three-dimensional tetrahedral polycatenanes

Abstract

Seven of the best: A dynamic combinatorial library of polycatenated tetrahedra was prepared by complexation between a dynamic Fe₄L₆ tetrahedral cage, constructed from ligands containing an electron‐deficient naphthalenediimide core, and an electron‐rich aromatic crown ether, 1,5‐dinaphtho[38]crown‐10. The highest order species in the library is the tetrahedral [7]catenane.

Scheme 1

a) Synthesis of tetrahedral cage A; b) representation of a DCL formed upon addition of excess crown ether B.

Figure 1

Partial ¹H NMR spectra (400 MHz, CD₃CN/CDCl₃ 1:1 v/v, 298 K) of a) crown ether B, b) cage A, c) a DCL formed following the mixture of A (5.4×10⁻⁴  m, 1 equiv) and B (10 equiv) after 12 h, and d) the [7]catenane obtained by the addition of B (38 equiv) to A (1 equiv) after 12 h. Signals H^a′, H^b′, and H^c′ are from crown ether protons threaded around an NDI, and peak H^10′ is the corresponding catenated NDI proton. Peak H¹⁰* corresponds to a noncatenated NDI edge of a cage. All other protons are assigned as indicated in Scheme 1.

Figure 2

DOSY spectrum (500 MHz, CD₃CN/CDCl₃ 1:1 v/v, 298 K) of a 1:10 cage/crown ether mixture.

Figure 3

Electrospray Fourier‐transform ion‐cyclotron‐resonance mass spectrometry. a) ESI‐FTICR mass spectrum of A. Insets show isotope patterns after mass‐selection at different time intervals of irradiation in an IR multiphoton dissociation experiment. b) ESI‐FTICR mass spectrum of a 1:10 cage/crown ether mixture. c),d) spectra obtained from IRMPD experiments performed with mass‐selected [M₄L₆C₆]⁸⁺ and [M₄L₆C₇]⁸⁺ ions, respectively.

Figure 4

Binding isotherm showing the fraction of bound NDI, [NDI bound]/[NDI]₀, versus the total concentration of B, [Crown B], as derived from ¹H NMR equilibrium data. Squares represent the experimental data points (for full details of NMR analysis and data treatment, see the Supporting Information, Section S8). The black trace is the fitting of the data using a one‐to‐one binding model, yielding K _chem=794±34 L mol⁻¹. Colored lines represent the calculated composition of the intermediate cage/crown ether complexes as a function of crown ether concentration.