Photocatalytic and Antimicrobial Activity of Titanium(IV)-Oxo Clusters of Different Core Structure

Abstract

The purpose of this paper is to assess the relationship between the core architecture of titanium(IV)-oxo complexes (TOCs) known as {TiaOb} and their photocatalytic and antimicrobial activity. The following TOCs: [Ti6O4(OiBu)8(O2C13H9)8] · 2(CH3)2CO (1), [Ti6O6(OiBu)6(O2C13H9)6] (2), [Ti6O6(OiBu)6(O2C13H9)6] (3), [Ti3O(OiPr)8(O2C13H9)2] (4), and [Ti4O2(OiBu)10(O2C13H9)2] (5), where -O2C13H9represents 9-fluorene-carboxylate ligands, werestudied to investigate thiseffect. The structures of (1)–(5) were confirmed using single-crystal X-ray diffraction and spectroscopic methods. Since TOCs can be sensitive to hydrolysis processes, their photocatalytic and antimicrobial activity was evaluated after dispersing them in a polymer matrix, which acted as a protective agent against the aquatic environment. The results revealed that the photocatalytic activity of the studied TOCs follows the trend (2) > (5) > (4) > (1) in both the UV and visible ranges. All studied oxo complexes exhibited strong antibacterial activity against Gram-positive strains and weaker activity against Gram-negative strains. The proposed mechanism of the antimicrobial activity of TOCs assumes that this effect is associated with the generation of reactive oxygen species (ROS) on the surface of composite samples. Samples of PMMA + (1) 10 wt.% and PMMA + (5) 20 wt.%, in which both O− and O2− paramagnetic species were observed in the electron paramagnetic spectroscopy (EPR) spectra, demonstrated the highest antimicrobial activity.

Structural Characterization and Bioactivity of a Titanium(IV)-Oxo Complex Stabilized by Mandelate Ligands

“…In this case, the mechanism of biocidal action is associated with oxidative stress induced by the generated ROS. Our previous investigations confirmed the biocidal activity of {Ti 4 O 2 } clusters stabilized with carboxylate ligands (such as 4-aminobenzoic acid, 4-hydroxybenzoic acid, and 9-fluorene carboxylate) [5,24,25]. The analysis of the electron paramagnetic resonance (EPR) spectra of these compounds confirmed the generation of O 2 − and O − oxygen anions on the surface of both pure oxo complexes and composites prepared by dispersing the complexes in a poly(methyl methacrylate) (PMMA) matrix.…”

“…These compounds have found applications in diverse technologies, including hydrogen production or water purification [3,4]. Previous research led to the synthesis of TOCs with cores containing from 2 to 44 titanium atoms [5][6][7][8][9][10][11][12], with the largest group consisting of compounds with four-and six-nuclear cores [13][14][15][16][17]. The cores {Ti a O b } of TOCs can be stabilized by alkoxide groups, as well as carboxylate or phosphonate ligands, although β-diketonate, β-ketoester, and sulfonate ligands have also been employed [5,18,19].…”

“…Previous research led to the synthesis of TOCs with cores containing from 2 to 44 titanium atoms [5][6][7][8][9][10][11][12], with the largest group consisting of compounds with four-and six-nuclear cores [13][14][15][16][17]. The cores {Ti a O b } of TOCs can be stabilized by alkoxide groups, as well as carboxylate or phosphonate ligands, although β-diketonate, β-ketoester, and sulfonate ligands have also been employed [5,18,19]. The varied possibilities of carboxylate ligand coordination with titanium atoms [20] explain the fact that most of the works focus on investigations of Ti(IV)-oxo complexes stabilized with alkoxide and carboxylate ligands.…”

“…The varied possibilities of carboxylate ligand coordination with titanium atoms [20] explain the fact that most of the works focus on investigations of Ti(IV)-oxo complexes stabilized with alkoxide and carboxylate ligands. Notably, the type of carboxylate ligand has a significant influence both on the {Ti a O b } core structure and the oxo complex photocatalytic activity [5,7,[21][22][23][24][25][26].…”

“…Interest in Ti(IV)-oxo complexes also stems from their potential biomedical applications. Studies on the utilization of TOCs in photodynamic therapy [27] and as antimicrobial agents [5,13,24,[28][29][30] are particularly significant. With the ongoing search for materials possessing bactericidal properties and the ability to prevent microbial growth, our research has concentrated on the latter aspect.…”