Using nuclear magnetic resonance spectroscopy to study molecular structure and noncovalent interactions in dendrimer and dendrimer-related supramolecular systems

Various nuclear magnetic resonance (NMR) methods can be used to study the structure, property, and interaction of molecules in solution. In this thesis, 1D and 2D NMR techniques were used to completely characterize the structures of novel dendrimers and dendrimer based supramolecular systems. Furthermore, diffusion NMR was used to quantify the efficiency of spontaneous formation of dendrimer based guest-host systems and dendrimer based inverse micellar systems.; The results from this thesis demonstrate the effectiveness of NMR spectroscopy as a powerful tool for structural characterization as well as investigation of molecular interactions. By dispersing the NMR resonances into another dimension, the enhanced resolution allows a complete characterization of the novel dendrimers and the components of dendrimer related systems via encapsulation and self-assembly. The dendrimers and related systems are poly(etherhydroxyamine) piperazine surface dendrimer, poly(amidoamine) Tris-OH surface dendrimer, poly(propyleneimine) dendrimer (PPI), DTPA (diethylenetriaminepentaacetic acid, a commonly used MRI contrast reagent) and 5-fluorouracil (a clinically used anti-tumor drug) as guest molecules for dendrimer encapsulation, and hexanoic acid self-assembled inverse micelles based on PPI dendrimers.; In this thesis, a novel adiabatic selective diffusion NMR pulse sequence was used. In order to achieve high accuracy and precision of diffusion NMR measurements, different experimental conditions and parameters were explored. The optimized settings were selected and used to measure the efficiency of the interactions between molecules in the dendrimer related encapsulation and self-assembly systems. Therefore, accurate diffusion coefficients of dendrimers and the entities in the dendrimer based supramolecular systems were measured. These values were then used to determine the binding efficiency of the dendrimer based guest-host systems, as well as to calculate the binding constants for the dendrimer based inverse micelles. It was found that dendrimers can encapsulate (or interact with) guest molecules at an efficacy up to 50% of the total guest population. Also, according to the calculated binding constants, the interaction of hexanoic acid molecules with PPI dendrimers in the self-assembled inverse micelles was comparable to the complexation of copper (II) ions (Cu 2+) with ammonia ligands at equilibrium.