Solid state deposition of chiral amphiphilic porphyrin derivatives on glass surface

Abstract

Herein, we present a straightforward method to achieve optically active films based on porphyrin derivatives. The introduction of an aminoacid functionality on the porphyrin platform confers to the macrocycle both the amphiphilic and chiral character exploited for its solvent-promoted self-aggregation leading to the formation of chiral supramolecular architectures. These ordered suprastructures have the propensity to spontaneously layer as solid films on glass surfaces. The deposited material has been characterized by means of UV-visible, fluorescence emission, circular dichroism spectroscopy and AFM. The reported studies show once more how the stereochemical information stored on a single porphyrin framework can induce the formation of supramolecular chiral architectures, in solution, as well as in solid state. Furthermore, slight modifications on the porphyrin skeleton can influence the aggregation process and the structural features of the final assemblies, leading to solid surfaces featuring different morphologies. These combined aspects can be of great importance for the achievement of solid state chemical sensors with stereoselective properties.

Stereospecific Self-Assembly Processes of Porphyrin-Proline Conjugates: From the Effect of Structural Features and Bulk Solvent Properties to the Application in Stereoselective Sensor Systems

“…The synthesis of the macrocycles entailed the straightforward coupling of the proper macrocycle with the proline derivative using the well-known peptide coupling reactions. The procedures are summarised in Scheme 2 [ 41 , 42 , 43 , 44 ].…”

“…In the case of the present chiral cationic derivatives, the spontaneous deposition yielded to porphyrin films with retained supramolecular chirality ( Figure 7 a) [ 42 ]. The same substrates, once transferred onto quartz slides by means of Langmuir–Blodgett technique, still formed chiral films but, in the case of the cationic free-base (M = 2H), of opposed chirality with respect to that of the films obtained upon spontaneous deposition in equilibrium conditions ( Figure 7 b) [ 79 ].…”

Chiral Selectivity of Porphyrin–ZnO Nanoparticle Conjugates

“…We have recently studied, in fact, the formation of chiral supramolecular structures formed by cationic chiral porphyrin derivatives (MPL­(+); see Supporting Information (SI), Chart S1 and Figure S1). − Although the chirality of these structures was preserved after the deposition onto inorganic substrates, the expected stereoselective properties were not found after the film’s deposition onto the surface of quartz microbalance, with regard to exposure to vapors of chiral analytes (unpublished results; see Figure S1 in the SI and the Results section below).…”

Seeding Chiral Ensembles of Prolinated Porphyrin Derivatives on Glass Surface: Simple and Rapid Access to Chiral Porphyrin Films

“…Within this set of tetrapyrroles, cationic derivatives functionalized with a peripheral (L)-proline moiety have been also exploited for the preparation of chiral films to be applied for sensor development. Two strategies have been basically reported: 1) the steering of the self-aggregation of chiral porphyrin monomers in ethanol/water mixture of proper composition to give in 1-2 days chiral assemblies that spontaneously layer on glass substrate dipped into the solution (Monti et al, 2011); 2) the use of Langmuir-Blodgett technique to assemble the porphyrin molecules onto a glass surface in chiral multilayers through air/water interfacial organization (Colozza et al, 2019). Films based on the anionic counterpart (L)ZnP(-) (Scheme 1) anchored to ZnO nanoparticles have been also chirally organized on quartz microbalance surfaces and used for the stereoselective recognition of limonene enantiomer vapors (M. Stefanelli et al, 2019).…”