Coordination-driven self-assembly of three-dimensional supramolecular dendrimers

Abstract

The design and synthesis of novel three-dimensional (3-D) supramolecular dendrimers is described. The coordination-driven self-assembly of a 120 degrees diplatinum acceptor and tritopic pyridyl donors bearing [G-0]-[G-3] Fréchet-type dendrons results in a series of supramolecular dendrimers under mild conditions, possessing a robust adamantanoid core of well-defined shape and size. The assemblies were identified using multinuclear ((31)P and (1)H) NMR spectroscopy and electrospray ionization mass spectrometry, as well as pulsed-field-gradient spin-echo (PGSE) NMR measurement together with computational simulations. Isotopically resolved mass spectral data support the existence of the [6 + 4] assembly of adamantanoid dendrimers, and the NMR results are consistent with the formation of these symmetrical assemblies. PGSE NMR measurements together with MMFF force-field modeling clearly reveal the structural feature of the 3-D supramolecular dendrimers with varying sizes.

Figure 1

³¹P{¹H} NMR (300 MHz, Acetone-d₆/CD₂Cl₂: 1/1) Spectra of (a) 120° Organoplatinum Acceptor 1 and (b) [G-3] Supramolecular Dendrimer 3d.

Figure 2

Calculated (blue, top) and Experimental (red, bottom) ESI Mass Spectra of [G-2] Supramolecular Dendrimer 3c.

Figure 3

Computational simulations (MMFF force field) of 3-D dendrimers 3a–d (protons and triethyl phosphrous moieties of adamantanoid core omitted for clarity) and their calculated (blue) sizes as well as experimental (red) values from PGSE NMR measurements.

Scheme 1

Representation of the [6 + 4] Self-Assembly of Adamantanoid Supramolecular [G-0]–[G-3] Dendrimers 3a–d.