An NMR and Molecular Modeling Study of Carbosilane‐Based Dendrimers Functionalized with Phenolic Groups or Titanium Complexes at the Periphery

Abstract

Dendrimers are modified polymers whose architecture is defined by the presence of a central atom or core with multiple branches. These molecules lend themselves to a variety of architectures and uses, including drug delivery and catalysis. The study of the molecular conformations and shapes of dendritic molecules is necessary but not yet routine. Here we present an NMR and molecular modeling study of a series of carbosilane dendrimers, namely 1G-{(CH2)3[C6H3(OMe)]OH}4 (1), 2G-{(CH2)3[C6H3(OMe)]OH}8 (2), and 2G-{(CH2)3[C6H3(OMe)]O[Ti(C5H5)Cl2]}8 (3). Various two-dimensional NMR techniques were used to completely assign the 1H and 13C resonances of molecules 1-3. This information was used, in conjunction with 1H and 13C spin-lattice relaxation measurements, to assess the chain motion of the molecules. The NMR data were also compared with 1-ns molecular dynamics (MD) simulations of 1 and 2 using the MMFF94 force field. The results indicate that these dendrimers possess a core that is motionally decoupled from the rest of the dendrimer, with flexible arm segments that extend from the core. The addition of eight functionalized titanium groups to the ends of the dendrimer chains of 2 to yield molecule 3 serves to further restrict chain motion.

“Clickable” PEG−Dendritic Block Copolymers

“…From a structural point of view, this variation of T 2 reflects the different mobility and relative density distribution within the dendrimers, and this could be better defined if a more complete study, covering several signals, and not only T 2 , but also spin−lattice relaxation times ( T 1 ), were carried out (Figure ) …”

Coarse-grained modelling of urea-adamantyl functionalised poly(propylene imine) dendrimers

“…[24][25][26][27][28] Another was using atomistic MD to model specific dendrimers, but still in implicit solvent or actual vacuum. Most notable are poly(propylene imine) (PPI) in vacuum [29,30] and melt [31,32] and poly(amido amine) (PAMAM) in vacuum [33][34][35] and melt, [36] but also various phenyl- [37][38][39][40] and carbosilane-based [41,42] dendrimers have been modelled. As both the solvent and the dendrimer composition influence the behaviour, explicit solvent atomistic simulations have also been performed for, e.g., PPI, [43][44][45][46] PAMAM [46][47][48][49] and carbosilane [50] dendrimers.…”

Neutral and Cationic Dendritic Palladium(II) Complexes ContainingN,N‘-Iminopyridine Chelating Ligands. Synthesis and Their Use for the Syndiospecific Copolymerization of CO/4-tert-Butylstyrene

“…Metallodendrimer research has been steadily gaining ground during the past few years, and a considerable number of dendritic macromolecules containing transition metals at their core, branches, or periphery have been prepared for use in metal-based catalysis, including oligomerization and polymerization. , We have contributed to the chemistry of carbosilane dendrimers containing early-transition-metal complexes bonded to the dendritic periphery or focal point, usually through O- or N-donor anchoring ligands. , In our study of the catalytic performance in ethylene polymerization of nickel(II) complexes coordinated to carbosilane dendrimers through the pyridylimine ligands Ia − c (Chart ), we found that the microstructure and oligomer/polymer product distribution are significantly affected by the size of the dendritic precursor …”