Syntheses of 3‐arm and 4‐arm star‐branched polystyrene Ru(II) complexes by the click‐to‐chelate approach

Abstract

Metal template synthesis is a useful methodology to make sophisticated macromolecular architectures because of the variety of metal ion coordination. To use metal template methodology, chelating functionalities should be introduced to macromolecules before complexation. In this article, we demonstrate the click‐to‐chelate approach to install chelating functionality to polystyrene (PS) and complexation with Ru(II) ions to form 3‐arm and 4‐arm star‐branched PS Ru(II) complexes. Azide‐terminated PS (PS‐N3) was readily prepared by atom transfer radical polymerization using 1‐bromoethylbenzene as an initiator followed by substitution of bromine by an azide group. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition of PS‐N3 with 2‐ethynylpyridine or 2,6‐diethynylpyridine affords 2‐(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐tapy) or 2,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐bitapy) ligands bearing one or two PS chains at the first‐position of the triazole rings. Ru(II) complexes of PS‐tapy and PS‐bitapy were prepared by conventional procedure. The number‐averaged molecular weights (Mns) of these complexes were determined to be 6740 and 10,400, respectively, by size exclusion chromatography using PS standards. These Mn values indicated the formation of 3‐arm and 4‐arm star‐branched PS Ru(II) complexes [Ru(PS‐tapy)3](PF6)2 and [Ru(PS‐bitapy)2](PF6)2 on the basis of the Mn values of PS‐tapy (2090) and PS‐bitapy (4970). The structures of these complexes were also confirmed by UV–vis spectroscopy and X‐ray crystallography of the Ru(II) complexes [Ru(Bn‐tapy)3](PF6)2 and [Ru(Bn‐bitapy)2](PF6)2, which bear a benzyl group instead of a PS chain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry

“…60,133 Study of an analogous complex [Ru(1) 2 ](PF 6 ) 2 confirmed the geometry of the polymer-appended complex. Polymers such as polystyrene, poly(n-butyl acrylate), poly(n-hexyl isocyanate), poly(caprolactone) and poly(styrene oxide) were used in various combinations.…”

“…59 This research demonstrated that synthesis of the btp based ligand provided easy access to a class of terdentate ligands, possessing a terpy-like coordination environment, but with distinctive differences such as the broad scope of functionalisation available via the CuAAC reaction and size differential between the heterocyclic rings. Hence, btp provides a promising method of introducing terpy-like functionality to macromolecules because of the excellent feasibility of azide substitution and 'click' chemistry, 60 as was also discussed above.…”

“…Given the fact that the btp ligand can be readily derivatised at the 1-position of the triazole units, this ligand is an excellent candidate for such endeavours. 60,61 This is further fuelled by the rapid developments that have occurred within the field of metallo-supramolecular chemistry. Here, most architectural shapes and topologies have been accessed; hence, the focus has increasingly moved towards developing new methods for functionalising ligands, and synthesis that is modular, facile and high-yielding.…”

“…The versatility of triazolyl substituents reported is remarkable, with alkyl chains of various lengths, aryl groups and even motifs such as ferrocenes 91 and porphyrins 71 being introduced. Btp ligands have even been attached directly to surfaces, such as polystyrene, 60 and bound to TiO 2 surfaces; 92 clearly demonstrating the wide scope such ligands have in modern coordination and supramolecular chemistry.…”

“…59,60,93,95,97,98,100,105,106,111,128,129 Flood and co-workers showed that Ru(II) forms stable coordination compounds with 3b. X-ray crystal crystallography showed a 1 : 2 metal : ligand stoichiometry, with the ligands adopting a distorted octahedral geometry, as demonstrated in Fig.…”