| Full text | |
| Author(s): |
Suarez, Eduardo Diaz
;
Lima, Filipe Camargo Dalmatti Alves
;
Rebaza, Arles V. Gil
;
Constantino, Vera Regina Leopoldo
;
Petrilli, Helena Maria
Total Authors: 5
|
| Document type: | Journal article |
| Source: | DALTON TRANSACTIONS; v. 54, n. 6, p. 13-pg., 2024-12-18. |
| Abstract | |
Distortions in the porphyrin core from planarity can trigger a unique structure-property relationship, imparting its basicity, chemical stability, redox potential, and excited-state energetics, among other properties. The colour change promoted by such distortion is signed by red shifts in its electronic absorption spectra. The adsorption of guest meso-substituted free-base porphyrin species onto inorganic hosts, such as clay minerals (layered aluminium or magnesium silicates), is known to further promote colour changes. However, the origin of these changes remains a subject of debate without a clear consensus. In this work, an extensive theoretical study was conducted using density functional theory (DFT) to model the interactions between tetracationic porphyrins, specifically meso-substituted groups N-methyl-4-pyridyl (p-TMPyP) and N-methyl-3-pyridyl (m-TMPyP), and montmorillonite (MMT) with the ideal formula [(Al1.67Mg0.33)Si4O10(OH)2]-0.33. The following conditions were evaluated: (i) adsorption or intercalation of p-TMPyP into MMT host structure, (ii) intercalation of m-TMPyP into MMT, and (iii) the influence of water on the intercalation process. The electrostatic interactions between the porphyrins and the MMT siloxane surface induced conformational changes in p-TMPyP, characterized by rotation of the substituent groups at the macrocycle periphery and a twist of the porphyrin plane. The nonplanarity of the intercalated p-TMPyP guest produced robust Br & oslash;nsted basic sites capable of abstracting H+ ions from intercalated water molecules, resulting in the formation of a dication. The macrocycle distortion was found to decrease pi-conjugation, thereby enhancing the localisation of the lone pair on the imine nitrogen atom. On the other hand, m-TMPyP exhibited slight core macrocycle deformations and minor changes in the dihedral angles of its meso-substituent groups compared to its isomer, with no observed protonation reaction upon intercalation. These findings highlight the clay microenvironment as a promising strategy for inducing conformational alterations in porphyrins, promoting nonplanarity, and exemplifying a shape-responsive system within the framework of guest-host chemistry. (AU) | |
| FAPESP's process: | 23/17506-6 - Computational study of the electron transfer mechanism in nanostructured hybrid systems |
| Grantee: | Filipe Camargo Dalmatti Alves Lima |
| Support Opportunities: | Regular Research Grants |
| FAPESP's process: | 14/50869-6 - INCT 2014: on Organic Electronics |
| Grantee: | Roberto Mendonça Faria |
| Support Opportunities: | Research Projects - Thematic Grants |