title: Analysis of poly(amidoamine) dendrimer structure by UV-vis spectroscopy.
abstract: We report a UV-vis spectroscopic study of four different types of poly(amidoamine) dendrimers. The results indicate that the degree of protonation of the interior tertiary amines of these dendrimers correlates directly to an absorption band with λ(max) in the range of 280-285 nm. Specifically, at low pH, the tertiary amines are protonated and the 280-285 nm band is absent. However, at elevated pH, when these groups are deprotonated, this band appears. Similar results were obtained for a simple model compound. The dependence of the 280-285 nm band on the chemical state of the tertiary amines of the dendrimers was confirmed by complexing them with Pd(2+) and Pt(2+). In this case the band disappears, and it only reappears when the metal ions are decomplexed following reduction with BH(4)(-). Finally, filtration experiments showed that the absorption band between 280-285 nm arises exclusively from intact, or nearly intact, dendrimers rather than low-molecular-weight fragments.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, USA.
authors.forename: Surojit
authors.initials: S
authors.lastname: Pande
authors.forename: Richard M
authors.initials: RM
authors.lastname: Crooks
mesh_terms: D050091:Dendrimers / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D053758:Nanoparticles / Q000032:analysis; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D011073:Polyamines / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties
chemical_list: D050091:Dendrimers; D009942:Organometallic Compounds; C531249:Poly(amidoamine); D011073:Polyamines; D010984:Platinum; D010165:Palladium