Size and shape assessment of organometallic gold(I) metallodendrimers through PGSE-NMR and molecular dynamics simulations

Abstract

The reactions of the amino-terminated PAMAM-dendrimers (generations 0–2) with Ph2PCH2OH in the appropriate molar ratios give rise to the dendritic phosphines PAMAM-GZ-(N(CH2PPh2)2)n (Z=0, n=4 (1), Z=1, n=8 (2) and Z=2, n=16 (3)). Further reaction of phosphines 1–3 with one equivalent of [Au(C6F5)(tht)] (tht=tetrahydrothiophene) per P-donor site leads to metallodendrimers [{Au(C6F5)}2n{PAMAM-GZ-(N-(CH2PPh2)2)n}] (Z=0, n=4 (4), Z=1, n=8 (5) and Z=2, n=16 (6)). Phosphines 1–3 and metallodendrimers 4–6 have been characterized by 1H, 19F and 31P{1H} NMR spectroscopy and through IR spectroscopy. 1H PGSE NMR studies of the dendritic phosphines and the metallodendrimers permit the evaluation and comparison of the different molecular sizes through their corresponding hydrodynamic radius, depending on the dendrimer generation and on the coordination of the organometallic fragments [Au(C6F5)]. Molecular dynamics simulations allow the theoretical estimation of the macromolecular size through the calculation of the radius of gyration for each species and the calculation of the dendrimer flexibility.