title: Spectroscopic, morphological, and mechanistic investigation of the solvent-promoted aggregation of porphyrins modified in meso-positions by glucosylated steroids.
abstract: Solvent-driven aggregation of a series of porphyrin derivatives was studied by UV/Vis and circular dichroism spectroscopy. The porphyrins are characterised by the presence in the meso positions of steroidal moieties further conjugated with glucosyl groups. The presence of these groups makes the investigated macrocycles amphiphilic and soluble in aqueous solvent, namely, dimethyl acetamide/water. Aggregation of the macrocycles is triggered by a change in bulk solvent composition leading to formation of large architectures that express supramolecular chirality, steered by the presence of the stereogenic centres on the periphery of the macrocycles. The aggregation behaviour and chiroptical features of the aggregates are strongly dependent on the number of moieties decorating the periphery of the porphyrin framework. In particular, experimental evidence indicates that the structure of the steroid linker dictates the overall chirality of the supramolecular architectures. Moreover, the porphyrin concentration strongly affects the aggregation mechanism and the CD intensities of the spectra. Notably, AFM investigations reveal strong differences in aggregate morphology that are dependent on the nature of the appended functional groups, and closely in line with the changes in aggregation mechanism. The suprastructures formed at lower concentration show a network of long fibrous structures spanning over tens of micrometres, whereas the aggregates formed at higher concentration have smaller rod-shaped structures that can be recognised as the result of coalescence of smaller globular structures. The fully steroid substituted derivative forms globular structures over the whole concentration range explored. Finally, a rationale for the aggregation phenomena was given by semiempirical calculations at the PM6 level.
authors: Charles University, Department of Organic Chemistry, Albertov 8, 12840 Prague 2, Czech Republic.
authors: Karel
authors: K
authors: Zelenka
authors: Tomáš
authors: T
authors: Trnka
authors: Iva
authors: I
authors: Tišlerová
authors: Donato
authors: D
authors: Monti
authors: Stefano
authors: S
authors: Cinti
authors: Mario Luigi
authors: ML
authors: Naitana
authors: Luca
authors: L
authors: Schiaffino
authors: Mariano
authors: M
authors: Venanzi
authors: Giuseppe
authors: G
authors: Laguzzi
authors: Loredana
authors: L
authors: Luvidi
authors: Giovanna
authors: G
authors: Mancini
authors: Zdena
authors: Z
authors: Nováková
authors: Ondřej
authors: O
authors: Šimák
authors: Zdeněk
authors: Z
authors: Wimmer
authors: Pavel
authors: P
authors: Drašar
mesh_terms: D002942:Circular Dichroism; D006027:Glycosides / Q000737:chemistry*; D007700:Kinetics; D018625:Microscopy, Atomic Force; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D013256:Steroids / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D006027:Glycosides; D011166:Porphyrins; D012997:Solvents; D013256:Steroids; D014867:Water