| Abstract
| - Shape-persistent multi(NCN−palladium and/or −platinum) complexes having one- (5 and 6), two-(1 and 2), and three-dimensional (3 and 4) geometries were prepared in moderate to good yields.Two different approaches were used to construct the multimetallic materials: (i) the constructionof the multisite ligands followed by the permetalation step and (ii) selective and mild one-potcoupling of monometallic buiding blocks to a multifunctional shape-persistent organic core molecule.The first approach was used to prepare the palladated and/or platinated tris- (2) and bis(NCN−pincer) (5) complexes, while the second approach afforded the palladated and platinated octakis-(3) and dodecakis(NCN−pincer) (4) complexes. Complexes 1−6 were subjected to nanofiltration(NF) experiments in order to investigate the influence of rigidity and geometry on the retention ofthese molecules by NF membranes. For this purpose, the corresponding (NCN−Pt−X)n complexes(1c−4c, 5, and 6) were used since exposing these complexes to sulfur dioxide in solution resultedin the formation of bright orange complexes, allowing the use of UV/vis spectroscopy to accuratelydetermine the concentrations of 1−6 in both retentate and permeate. Using the MPF-60 (MWCO= 400) NF-membrane, retention rates of 82.4 (6), 93.9 (1c), 98.7 (2c), 99.5 (3c), 99.6 (5), and >99.9%(4c) were found, while 2c and 4c in combination with the MPF-50 (MWCO = 700) NF-membranewere retained in 97.6 and 99.9%, respectively. A clear relationship is observed between thedimensions calculated by molecular modeling and the retention rates of 1−6. The one-dimensionalbis(pincer−platinum) complex 5, however, shows an unexpectedly high retention rate (99.6%) thatcan be due to precipitation of the complex in the membrane (clogging of the membrane) and/or tothe formation of larger aggregates near the membrane. In addition, comparison of 2 and 4 withflexible nickelated G0- and G1-dendrimers with similar dimensions proved that a high degree ofrigidity in the backbone of macromolecular complexes indeed leads to more efficient retentions ofthese multimetallic materials by NF-membranes.
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