Oligomers nuclear resonance spectroscopy

Davidson et characterized perflurotetradecahydrophenanthroline oligomers using a combination of nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy for chemical analysis and time of flight secondary ion mass spectrometry, infrared spectroscopy and ultraviolet-visible spectroscopy. 

Synthesis. Functionalized monomers (and oligomers) of sebacic acid (SA-Me2) and 1,6 -bis(/ -carboxyphenoxy)hexane (CPH-Me2) were synthesized and subsequently photopolymerized as illustrated in Figure 1. First, the dicarboxylic acid was converted to an anhydride by heating at reflux in methacrylic anhydride for several hours. The dimethacrylated anhydride monomer was subsequently isolated and purified by dissolving in methylene chloride and precipitation with hexane. Infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis results indicated that both acid groups were converted to the anhydride, and the double bond of the methacrylate group was clearly evident. 

Most of the metal alkoxides of interest for electrooptical ceramics are solids (less often liquids) that can be purified by recrystallization, sublimation, or distillation. They are all moisture sensitive, and handling under an inert atmosphere and with anhydrous solvents is thus required. Their unequivocal characterization and formulation are best achieved by x-ray diffraction studies (on monocrystals). Studies on solutions (molecular weight data, nuclear magnetic resonance, NMR, with H, or metal nuclei) are a means either to establish whether the solid-state structure is retained or, in the absence of x-ray data, to establish the molecular structure and eventually stereolability [48]. Mass spectrometry provides information on the stability of the oligomers or the het-erometallic species in the vapor phase. The information gained by infrared spectroscopy is limited the technique is mostly useful for the identification of solvates M(OR) (ROH)x (vOH absorption 3400-3100 cm-l or of chemically modified (heteroleptic) alkoxides (probe for the vCO stretching of P-diketonate or carboxylate ligands, for instance). 

In addition, gel-permeation chromatography (GPC), high performance liquid chromatography (HPLC) (39,80), and other analytical procedures such as nuclear magnetic resonance (NMR) (28) and infrared spectroscopy (IR) (81) are performed to determine MW, MW distribution, oligomer composition, fiinctional groups, and... 

Nuclear magnetic resonance (NMR) spectroscopy ( H, and other nuclei) is an extremely powerful analytical technique capable of providing unequivocal proof of a compound structure, but is usually applied to soluble materials. An interesting example in which this method provided the molecular structure, as well as information about conformations and molecular dynamics, for over 20 soluble n-alkoxy-substituted phenylene vinylene oligomers has been described [95]. 

---