A facile approach toward multicomponent supramolecular structures: selective self-assembly via charge separation

Abstract

A novel approach toward the construction of multicomponent two-dimensional (2-D) and three-dimensional (3-D) metallosupramolecules is reported. Simply by mixing carboxylate and pyridyl ligands with cis-Pt(PEt(3))(2)(OTf)(2) in a proper ratio, coordination-driven self-assembly occurs, allowing for the selective generation of discrete multicomponent structures via charge separation on the metal centers. Using this method, a variety of 2-D rectangles and 3-D prisms were prepared under mild conditions. Moreover, multicomponent self-assembly can also be achieved by supramolecule-to-supramolecule transformations. The products were characterized by (31)P and (1)H multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and pulsed-field-gradient spin echo NMR techniques together with computational simulations.

Scheme 1

Selective self-assembly of a multicomponent rectangle 4 by the combination of cis-Pt(PEt₃)₂(OTf)₂ 1, dicarboxylate ligand 2, and linear dipyridyl donor 3.

Figure 1

³¹P{¹H} NMR spectra of cis-Pt(PEt₃)₂(OTf)₂ 1 (a) and the multicomponent supramolecular rectangle 4 (b).

Figure 2

Full ESI mass spectrum of the solution of the multicomponent supramolecular rectangle 4.

Scheme 2

Selective self-assembly of multicomponent trigonal (7) and tetragonal (8) prisms by combination of cis-Pt(PEt₃)₂(OTf)₂ 1, dicarboxylate ligand 2, and tritopic (5) and tetratopic (6) pyridyl donors.

Figure 3

³¹P{¹H} NMR spectra of the trigonal prism 7 (a) and tetragonal prisms 8a (b) and 8b (c). ESI mass spectral data further support the self-assembly of supramolecular prisms 7 and 8. As shown in Figure 4 and Figure S5,6 (see Supporting Information), intense ESI mass peaks corresponding to consecutive loss of triflate anions from trigonal prism 7: m/z = 2218.76 [M – 2OTf]²⁺ and m/z = 1429.59 [M – 3OTf]³⁺ were observed, as were those corresponding to the tetragonal prisms: 8a at m/z = 2037.75 [M – 3PF₆]³⁺ and m/z = 1164.50 [M – 5PF₆]⁶⁺ and 8b at m/z = 2022.71 [M – 3PF₆]³⁺ and m/z = 1155.62 [M – 5PF₆]⁵⁺. All of these peaks are isotopically resolved and agree well with their theoretical distributions.

Figure 4

Full ESI mass spectrum of the tetragonal prism 8a.

Figure 5

Computational simulations of trigonal prism 7 (a) and tetragonal prisms 8a (b) and 8b (c).

Scheme 3

Representation of selective self-assembly of cis-Pt(PEt₃)₂(OTf)₂ with carboxylate and pyridyl moieties due to the lower energy of the heteroleptic System.

Scheme 4

Supramolecular transformations of square 9, truncated tetrahedron 10, and trigonal prism 11 into rectangle 4, trigonal prism 7, and tetragonal prism 8b, respectively, upon addition of the neutral triangle 12 assembled by cis-Pt(PEt₃)₂(OTf)₂ 1 and carboxylate ligand 2.

Figure 6

³¹P{¹H} NMR spectra of the homoleptic self-assemblies 9 (a), 10 (b), and 11 (c), and the neutral triangle 12 (d), as well as the multicomponent rectangle 4 (e), trigonal prism 7 (f), and tetragonal prism 8b (g) obtained via supramolecular transformations.

Figure 7

³¹P{¹H} NMR spectra for mixtures of square 9 upon addition of 0% (a), 10% (b), 25% (c), 50% (d), and 100% (e) of neutral triangle 12.

Scheme 5

Graphical representation of self-assembly of multicomponent porphyrin cage 14 by cis-Pt(PMe₃)₂(OTf)₂ 13 with carboxylate 2 and pyridyl ligands 6b and encapsulation of triphenylene TP.

Figure 8

Partial ¹H NMR spectra (300 MHz, acetone-d₆/D₂O = 1:1) of pure 14 (a), TP (b), and the host-guest mixture (c).

Figure 9

Calculated (blue, top) and Experimental (red, bottom) ESI mass spectrum of the encapsulated complex 14·TP.

Figure 10

Varied views of the computational model (MM2*) of the encapsulated complex 14·TP.