Excessive misuse of antibiotics and antimicrobials has led to a spread of microorganisms resistant to most currently used agents. The resulting global threats has driven the search for new materials with optimal antimicrobial activity and their application in various areas of our lives. In our research, we focused on the formation of composite materials produced by the dispersion of titanium(IV)-oxo complexes (TOCs) in poly(ε-caprolactone) (PCL) matrix, which exhibit optimal antimicrobial activity. TOCs, of the general formula [Ti₄O₂(OⁱBu)₁₀(O₂CR’)₂] (R’ = PhNH₂ (1), C₁₃H₉ (2)) were synthesized as a result of the direct reaction of titanium(IV) isobutoxide and 4-aminobenzoic acid or 9-fluorenecarboxylic acid. The microcrystalline powders of (1) and (2), whose structures were confirmed by infrared (IR) and Raman spectroscopy, were dispersed in PCL matrixes. In this way, the composites PCL + nTOCs (n = 5 and 20 wt.%) were produced. The structure and physicochemical properties were determined on the basis of Raman microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electron paramagnetic resonance spectroscopy (EPR), and UV–Vis diffuse reflectance spectroscopy (DRS). The degree of TOCs distribution in the polymer matrix was monitored by scanning electron microscopy (SEM). The addition of TOCs micro grains into the PCL matrix only slightly changed the thermal and mechanical properties of the composite compared to the pure PCL. Among the investigated PCL + TOCs systems, promising antibacterial properties were confirmed for samples of PCL + n(2) (n = 5, 20 wt.%) composites, which simultaneously revealed the best photocatalytic activity in the visible range.

The emergence of a large number of bacterial strains resistant to many drugs or disinfectants currently used contributed to the search of new, more effective antimicrobial agents. In the presented paper, we assessed the microbiocidal activity of tri- and tetranuclear oxo-titanium(IV) complexes (TOCs), which were dispersed in the poly(methyl methacrylate) (PMMA) matrix. The TOCs were synthesized in reaction to Ti(OR)₄ (R = ⁱPr, ⁱBu) and HO₂CR’ (R’ = 4-PhNH₂ and 4-PhOH) in a 4:1 molar ratio at room temperature and in Ar atmosphere. The structure of isolated oxo-complexes was confirmed by IR and Raman spectroscopy and mass spectrometry. The antimicrobial activity of the produced composites (PMMA + TOCs) was estimated against Gram-positive (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) and Gram-negative (Escherichia coli ATCC 8739 and E. coli ATCC 25922) bacteria and yeasts of Candida albicans ATCC 10231. All produced composites showed biocidal activity against the bacteria. Composites containing {Ti₄O₂} cores and the {Ti₃O} core stabilized by the 4-hydroxybenzoic ligand showed also high activity against yeasts. The results of investigations carried out suggest that produced (PMMA + TOCs) composites, due to their microbiocidal activity, could find an application in the elimination of microbial contaminations in various fields of our lives.

The purpose of this paper is to assess the relationship between the core architecture of titanium(IV)-oxo complexes (TOCs) known as {Ti_aO_b} 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.

Research on titanium-oxo complexes (TOCs) is usually focused on their structure and photocatalytic properties. Findings from these investigations further sparked our interest in exploring their potential biological activities. In this study, we focused on the synthesis and structure of a compound with the general formula [Ti₈O₂(OⁱPr)₂₀(man)₄] (1), which was isolated from the reaction mixture of titanium(IV) isopropoxide with mandelic acid (Hman) in a molar ratio of 4:1. The structure (1) was determined using single-crystal X-ray diffraction, while spectroscopic studies provided insights into its physicochemical properties. To assess the potential practical applications of (1), its microcrystals were incorporated into a polymethyl methacrylate (PMMA) matrix, yielding composite materials of the type PMMA + (1) (2 wt.%, 5 wt.%, 10 wt.%, and 20 wt.%). The next stage of our research involved the evaluation of the antimicrobial activity of the obtained materials. The investigations performed demonstrated the antimicrobial activity of pure (1) and its composites (PMMA + (1)) against both Gram-positive and Gram-negative strains. Furthermore, MTT tests conducted on the L929 murine fibroblast cell line confirmed the lack of cytotoxicity of these composites. Our study identified (1) as a promising antimicrobial agent, which is also may be use for producing composite coatings.

This study explores poly(methyl methacrylate) (PMMA)-based composites as potential alternatives to conventional TiO₂-based photocatalysts. Specifically, it examines PMMA composites enriched with oxo–titanium(IV) complexes, [Ti₈O₂(OⁱPr)₂₀(man)₄] (1), [Ti₄O(OⁱPr)₁₀(O₃C₁₄H₈)₂] (2), and [Ti₆O₄(OⁱPr)₂(O₃C₁₄H₈)₄(O₂CEt)₆] (3), alongside ruthenium(III) complexes, K[Ru(Hedta)Cl]∙2H₂O (4) and [Ru(pic)₃]·H₂O (5). We assessed the physicochemical, adsorption, and photocatalytic properties of these composites with structural analyses (Raman spectroscopy, X-ray absorption (XAS), and SEM-EDX), confirming the stability of complexes within the PMMA matrix. Composites containing titanium(IV) compounds demonstrated notably higher photocatalytic efficiency than those with ruthenium(III) complexes. Based on activity profiles, composites were categorized into three types: (i) UV-light active (complexes (1) and (2)), (ii) visible-light active (complexes (4) and (5)), and (iii) dual-range active (complex (3)). The results highlight the strong potential of titanium(IV)–PMMA composites for UV-driven photocatalysis. Moreover, their activity can be extended to the visible range after structural modifications. Ruthenium(III)–PMMA composites, in turn, showed superior performance under visible light. Overall, PMMA composites with titanium(IV) or ruthenium(III) complexes demonstrate promising photocatalytic properties for applications using both UV and visible light ranges.

This study comprehensively analyses two new ruthenium(III) complexes, RuIIICl4(Nic)2]−[(CH3)2NH2]+DMF, 1, and [RuIIICl2(3-HPA)2]−[3-HH2PA]+(EtOH)2, 2, (where Nic = nicotinic acid (vitamin B3), 3-HPA = anion of a 3-hydroxypicolinic acid), as potential antimicrobial agents, highlighting their physicochemical properties, nanoparticle formation, and bactericidal activity. The complexes were fully characterised by a single crystal X-ray diffraction technique, Fourier-transform infrared, energy-dispersive X-ray, and electron paramagnetic resonance spectroscopies. The synthesis of micro- and nanoparticles (NPs) of these complexes was performed using the liquid anti-solvent crystallisation method. The formation of NPs was confirmed, and their sizes were determined using scanning electron microscopy and dynamic light scattering techniques. The Debye-Scherrer technique, based on powder diffraction X-ray data, indicated the high crystallinity of the nanomaterials. Toxicity and morphological effects on L929 fibroblasts, hepatocellular carcinoma (Hep-G2) and human epithelial colorectal adenocarcinoma (Caco-2) cell lines of the complexes were assessed using the MTT assay and an inverted phase-contrast microscope, respectively. Complex 1 is a promising anti-cancer drug candidate targeting intestinal cancers, showing cytotoxicity against Caco-2 cancer cells and no cytotoxicity against L929 fibroblast cells, while complex 2 is markedly cytotoxic. The antibacterial activity of the complexes was assessed against methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae strains using the minimum inhibitory concentration (MIC) method. Complex 2 demonstrates superior bactericidal properties, achieving MIC values as low as 125 μg/ml for S. aureus, while complex 1 exhibits lower antimicrobial efficacy. The role of ligand composition in modulating bioactivity was examined.