Carboxylate Ligands Research Articles

Two Proton Conductive Coordination Polymers Constructed by an Unprecedented Structural Transformation of a Phosphine-Based Tricarboxylate Ligand

The phosphine-based tricarboxylate 2-(3,3′-dioxo-1λ5-1,1′-(3H,3′H)-spirobi[2,1-benzoxaphosphol]-1-yl)benzoic acid (L) has been intensely studied due to its unique configuration and readily oxidizable phosphorus center. However, the coordination of L with metals have been largely ignored in the field of coordination polymers (CPs). Herein, we report two CPs, [Zn3(L1)2(dib)2(H2O)]·9H2O (1) and [Cu3(L2)2(dib)2]·3H2O (2) (H3L1 = tris(2-carboxyphenyl)phosphine oxide, H3L2 = 2,2′-phosphinico-dibenzoic acid, dib = 1,4-di(1H-imidazol-1-yl)butane), synthesized based on L. Strikingly, despite the initial use of L, the structures of 1 and 2 reveal that L undergoes two unprecedented in situ structural changes after coordination with the metal ion. In 1, L is transformed to the phosphine oxide derivative L1, while in 2, it is transformed to the phosphinic acid derivative L2. With the aid of the flexible ligand dib, the one-dimensional (1D) chain structure of 1 and three-dimensional (3D) supramolecular structure of 2 were constructed. For 1 and 2, especially in 1, there are abundant hydrogen bonds between the framework and the lattice water molecules, which are conducive to the formation of excellent hydrophilic channels and the transport of protons. Electrochemical experimental results show that 1 and 2 exhibit high proton conductivities (σ) of more than 10–4 S cm–1 over a wide temperature range of 303–353 K and low activation energies (Ea) at 98% relative humidity. Compared with the σ value of the initial ligand L (3.12 × 10–5 S cm–1), the best σ values of 1 and 2 are improved by 28 times and 6 times, respectively, and Ea is also reduced from 0.39 to 0.13 eV for 1 and 0.12 eV for 2. This is the first report of proton-conducting polymers based on a phosphine-based carboxylate ligand, involving two in situ structural transitions of the ligand.

Self-Assembled Cobalt–Nickel Bimetallic-Organic Framework Materials with High Supercapacitor Performance

Two new metal–organic frameworks (MOFs), [Co(bcpp)(bbip)]·H2O (Co-MOF) and [Ni(bcpp)(bbip)]·H2O (Ni-MOF), have been generated based on a V-type flexible carboxylic ligand 3,5-bis(4-carboxyl phenoxy) pyridine (H2bcpp) and a rigid N-donor ligand 1,1′-(1,4-phenylene)bis(1H-benzimidazole) (bbip) by a solvothermal method. Co-MOF and Ni-MOF are isostructural with a 2-fold interpenetrated layered structure. Moreover, a series of bimetallic CoxNiy-MOFs (x/y = 1:1, 2.5:1, 2.75:1, 3:1, 3.25:1, and 3.5:1) were obtained by using one-pot synthesis. Owing to their mixed metallic components and internal layered structure, the bimetallic CoxNiy-MOFs possess a remarkable electrochemical storage property. Significantly, the Co2.75Ni1-MOF has high specific capacitance (699 F g–1) at 0.5 A g–1 and good cycling durability (retained 72.7% over 3100 turns). Additionally, an asymmetrical ultra-capacitor based on Co2.75Ni1-MOF and activated carbon (AC) delivers a maximum energy density of 20.44 Wh kg–1 at 387.49 W kg–1 and a high cycle-to-cycle stability with 85.4% of the primary capacitance over 15,000 turns.

Impact of Uniform Facets on the Thermodynamics of Ligand Exchanges on Colloidal Quantum Dots

Nanocrystal surfaces play a critical role in dictating their physical and chemical properties. Colloidal semiconductor nanocrystals, or quantum dots, are generally synthesized with insulating aliphatic ligands, but these ligands can be post-synthetically exchanged with other molecular species for a variety of applications. While previous work has investigated the thermodynamics of ligand exchanges on quasi-spherical quantum dots through sensitive isothermal titration calorimetry and 1H NMR measurements, the influence of well-defined crystal facets on the propensity of these ligand exchanges is yet to be explored using these techniques. We studied the exchange of native cadmium carboxylate ligands for zinc chloride ligands on (111) faceted cadmium selenide tetrahedrons and (100) faceted cadmium selenide cubes. From these measurements, we find the unexpected result that the thermodynamics of this ligand exchange between these facets is nearly identical. Further, a modified Ising model was used to fit both the calorimetric and 1H NMR data to extract thermodynamic parameters for the exchange. These simulations suggest that the observed enthalpic differences can be mostly attributed to varying inter-ligand interactions on the (111) and (100) facets.

Novel Pillared-Layer-like Metal–Organic Frameworks with Quadrilateral Channels for Efficient Separation of C2H2 from C2H2/CO2 and C2H2/C2H4 Mixtures

The selective separation of C2H2 from C2H2/CO2 and C2H2/C2H4 is crucial but remains incredibly challenging due to their extremely similar physical characteristics and nearly equivalent molecular kinetic diameters. Here, four novel pillared-layer-like metal–organic frameworks (MOFs) with quadrilateral channels, SNNU-283–286, which consist of a unique two-dimensional wave layer and carboxylic acid ligands as columns, are successfully synthesized via a facile solvothermal process. Interestingly, with the decrease of the bent angle between two −COOH groups in ligands, the distortion of the quadrilateral channel increases, and the two-dimensional wave layer becomes more curving. The optimized SNNU-285 with appropriate structural distortion exhibits remarkably high C2H2 adsorption capacity (124.6 cm3 g–1), superior selectivity (20.2), and enhanced breakthrough interval times (21.6 min g–1 at 273 K) for C2H2/CO2 due to the exposed open metal site and the polar furan ring. This work offers novel pillared-layer-like MOFs with quadrilateral channels for efficient C2H2 adsorption and purification.

Matched Ligands for Small, Stable Colloidal Nanoparticles of Copper, Cuprous Oxide and Cuprous Sulfide.

This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2 O or Cu2 S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2 equivalents vs. [CuMes]z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2 CR1 ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2 CR2 ) or di(thio)nonanoic acid, (HS2 CR1 ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2 O is preferentially coordinated by carboxylate ligands and Cu2 S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection.

The regulation of Lewis acid/basic sites in NaFe bimetal MOXs for the controllable photocatalytic degradation of electron-rich/deficient VOCs

The performance of metal-organic xerogels (MOXs) in the photocatalytic oxidative degradation (PCO) of volatile organic compounds (VOCs) relies on their Lewis acid-base interaction and the generation of oxidative radicals. Herein, by engineering the local charge imbalance of carboxyl ligands through synthesizing NaFe bimetal MOXs, the Lewis acidity of MIL-100(Fe) MOX was well tuned for the adsorption-degradation of electron-rich (aromatic hydrocarbons) and electron-deficient (aldehydes) VOCs. Benefiting from the implanted Lewis basic sites, NaFe-MOXs showed increased adsorption-PCO capacity for single acetaldehyde, while Fe-MOX with abundant Lewis acid sites could capture and degrade more o-xylene. The Lewis basic sites promoted the mineralization of single o-xylene and acetaldehyde by altering their interactions with the photocatalysts and improving the generation of oxidative radicals, which extended the lifetime of photocatalysts. By regulating the Lewis acid/basic sites within MOXs, this work provides an effective way for optimizing photocatalysts to enable the photocatalytic degradation of both electron-rich/deficient VOCs.

Front Cover: Paddle‐Wheel Dirhodium Complexes Bearing Bulky Carboxylate Ligands: Synthesis and Catalysis in Carbene Insertion Reactions (Chem. Asian J. 11/2023)

Paddle-Wheel dirhodium complexes bearing bulky carboxylate ligands were synthesized and characterized. The steric bulk of carboxylate ligands could affect the reaction selectivity in Rh-catalyzed intramolecular competitive carbene insertions: Rh catalysts with bulky carboxylates could provide five-membered ring products preferentially via the insertion into a carbon–hydrogen bond while conventional Rh catalysts gave six-membered ring products via the insertion of a carbon-carbon double bond. More information can be found in the Research Article by Tetsuaki Fujihara et al.

Dual-Functional Ln-OFs for Efficient Luminescence Sensing and Photoreduction of Cr(VI) without Additional Photosensitizers and Cocatalysts

Six isostructural stable lanthanide metal–organic Frameworks (Ln-OFs), namely, [Ln(ADBA)(HCOO)(DMF)] (Ln = Sm(1), Tb(2), Dy(3), Ho(4), Er(5), Eu(6), H2ADBA = 4,4′-(anthracene-9,10-diyl)dibenzoate, DMF = N,N-dimethylformamide), have been successfully obtained by the solvothermal method based on an aromatic carboxylic acid ligand H2ADBA. 1–6 have a similar three dimensional (3D) network structure with pts topology based on dinuclear metallic clusters {Ln2}. 1–6 all have excellent chemical and thermal stabilities, which is beneficial to carrying out fluorescence sensing and achieving catalytic reactions. 1–6 show admirable fluorescent properties in aqueous solution and can quickly and efficiently detect Fe3+, Cr2O72–, and nitrofurazone (NZF) with high selectivity and excellent sensitivity. Remarkably, upon completion of detection, the Cr2O72– ion in wastewater can be reduced into Cr3+ by photocatalyst 1, which is ascribed to its broad-range visible-light absorption and recyclable stability. During the reduction process, ethanol is an optimal hole scavenger; 1 shows an excellent convert efficiency (99%), a high rate constant (k) of 0.066 min–1, and a high Cr(VI) reduction rate of 0.158 mgCr(VI)·g–1cata·min–1 at pH = 2. Furthermore, photocatalyst 1 can be reused for three cycles without significant loss of catalytic activity. Until now, it is the first example to report that the photocatalytic reduction of Cr(VI) is achieved only by using 3D rare earth MOFs without additional photosensitizers and cocatalysts. The reasonable mechanisms of luminescence sensing and photocatalytic reaction were also investigated systematically via indispensable testing technologies and theoretical simulated calculation.

Paddle-Wheel Dirhodium Complexes Bearing Bulky Carboxylate Ligands: Synthesis and Catalysis in Carbene Insertion Reactions.

Dirhodium complexes bearing bulky carboxylate ligands are synthesized and characterized. The steric bulk of carboxylate ligands could affect the reaction selectivity in Rh-catalyzed intramolecular reactions: Rh catalysts with bulky carboxylate ligands provided five-membered ring products preferentially via the insertion into a carbon-hydrogen bond. Meanwhile, six-membered ring products were obtained using conventional Rh catalysts via the insertion of a carbon-carbon double bond.

A stable N-containing heterocyclic carboxylic acid ligand Co-MOF for photoelectric performance and anionic dyes adsorption

Metal-organic frameworks (MOFs) are crystalline porous hybrid materials with periodic network structure and abundant active sites, which are promising adsorbents for organic pollutants. Herein, a novel Co(II)-based organic framework (Co-MOF) [Co2(L1)2(L2)] (L1 = 3-(3-carboxylphenyl) isonicotinic acid, L2 = 4, 4′-Azopyridin) was developed for selective dyes adsorption. Experiments suggest that the Co-MOF exhibits high stability, good photoelectricity and high selectivity for dyes adsorption. For dyes adsorption, the Co-MOF shows a strong adsorption to methyl orange achieving a high capacity up to 440.5 mg g−1, but shows a weak adsorption to methylene blue or rhodamine, indicating its better selectivity for anionic dyes. An insight into the selective removal of the methyl orange is being accounted for by acid-base attraction, anion-π and π–π stacking interactions, involving the Co ion, phenyl rings, and ocarboxylate of L, and the phenyl rings, and osulfonate of MO. The current work contributes to the development of future multifunctional MOF materials with the application in environment protection.

Water-induced structural transformation of zinc supramolecular complex based on a terpyridine carboxylate ligand: Crystal structure and fluorescence sensing

For the past few years, the transformation of single crystal to single crystal in the field of metal-organic supramolecular complexes has aroused researchers’ extensive interest. The structural transformation of metal-organic supramolecular complexes using chemical stimuli provides alternative approaches to realize fascinating optical properties. Herein, a new 3D Zinc based supramolecular complex ZnTCA-1 (hereafter denoted SC1) was synthesized by solvothermal method with terpyridine carboxylic acid (TCA) as a ligand. By soaking SC1 in deionized water for 3 days, SC1 exhibited unique structural transformation properties, transforming from a 3D framework to a discontinuous 0D supramolecular complex ZnTCA-2 (hereafter denoted SC2). SC2 exhibits excellent water stability and acid-base stability (pH = 4–8), which inspired us to utilize SC2 for fluorescence detection, and found that SC2 exhibits a highly selective and sensitive (LOD = 3.97 μM) response to Cr2O72− based on fluorescence quenching, and the corresponding quenching coefficient (Ksv) is calculated to be 2.995 mM−1.

Aromatic additives with designed functions ameliorating chemo-mechanical reliability for zinc-ion batteries

Zn-ion batteries (ZIBs) emerge as potential candidates for scalable energy storage due to their advantages of high safety and excellent performance. However, the implementation of zinc-metal anode faces challenges, such as dendrite growth, hydrogen evolution, and by-product formation. Herein, we explore an archive of aromatic molecules with different ligands, encompassing carboxyl, hydroxyl, aldehyde, and sulfonate groups as electrolyte additives. Testing results provided an insight into the molecular structure, charge state, and chelating groups on the chemo-mechanical stability of ZIBs. The calculation results reveal that carboxyl and hydroxyl ligands allow stronger chemisorption on metallic Zn. Chelating properties of salicylate and catecholate ligands facilitate efficient solvation based on additive-Zn2+ coordination. The aldehyde and sulfonate ligands promote a textural growth of the (002) plane attributed to their lipophilic properties. The sulfonate-based molecules offer collective benefits owing to their large polar surface and designed textural deposits. The deposition of additive-Zn2+ complexes yields a robust layer with concentration gradients, thus hindering the crack propagation induced by oxidative stress. Zn//Zn stability tests show that sulfonate additives improved a lifetime from 50 to 3000 cycles at 2 mA cm−2 and 1 mAh cm−2. The results open a new strategy to develop and optimize advanced electrolytes for aqueous energy storage.

Classical Force Field Parameters for InP and InAs Quantum Dots with Various Surface Passivations.

Classical molecular dynamics (MD) simulations on realistic colloidal quantum dot (QD) systems are often hampered by missing force field (FF) parameters for an accurate description of the QD-ligand interface. However, such calculations are of major interest, specifically for studying the surface chemistry of colloidal nanocrystals. In this work, we have utilized a previously published stochastic optimization algorithm to obtain FF parameters for InP and InAs QDs capped by Cl, amine, carboxylate, and thiolate ligands. Our FF parameters are interfaced with well-established FFs for organic molecules, allowing for the simulation of InP and InAs QDs with a broad range of organic ligands in explicit apolar solvents. The quality of our FF parameters was assessed by comparing properties of the classical MD simulations with ab initio MD simulations and experimental and theoretical values from the literature.

Coinage Metal Complexes Containing Perfluorinated Carboxylates

A variety of coinage-metal complexes containing perfluorinated carboxylate ligands, together with their structures and thermal behavior, are reported. The silver(I) salts were accessible from the direct reaction of Ag2O with the acids in toluene. Their gold(I) phosphine counterparts formed in high yields by transmetallation using the silver(I) salts. Some structurally unique, mixed-metal (Au,Ag) complexes formed upon combining solutions of the silver(I) salts with the gold(I) phosphine carboxylates. The reduction of dinuclear copper(II) compounds containing perfluorinated carboxylates with triphenylphosphine resulted in the formation of the corresponding copper(I) tris(phosphine) complexes. X-ray structures of representative complexes, together with IR- and TGA data, are reported.

A Late-Stage Aryl C-H Olefination Strategy and Its Application Towards Global Proteome Profiling of ∆8-Tetrahydrocannabinol.

Drugs and bioactive natural products exert their pharmacological effects by engaging numerous cellular targets in our body. Identification of these protein targets is essential for understanding the mechanism-of-action of these compounds, thus contributing to improved drug design in drug discovery programs. Termed "in situ drug profiling", a common strategy for studying these bioactive compounds centralized on the covalent capture of protein targets along with a reporter tag to facilitate downstream proteomic analyses. Though highly successful, such a strategy required innate electrophilic traps to facilitate covalent capture, and its dependence on classical alkylation/acylation strategies to install reporter tags has restricted its applications on non-covalent compounds. Late-stage C-H functionalization (LSF) may resolve this by substituting biologically inert C-H bonds with desired electrophilic groups. Herein, we demonstrated this concept by arming a diverse range of electron-rich aromatic drugs and natural products with α,β-unsaturated esters, via late-stage C-H olefination with a arylthio-based carboxylic acid ligand developed by Ibanez and co-workers. We also showed that covalent probes generated from this LSF approach could be applied for "in situ drug profiling" of ∆8-THC, as exemplified by the successful target engagement of α-4db, a ∆8-THC-based probe, to its native target hCB2R. In combination with probe 7, a photoaffinity-based derivative of ∆8-THC, we identified several novel putative targets that could account for some of the effects in THC consumption. We anticipate our C-H LSF strategy to be widely adopted for future studies of non-covalent drugs.

Auxiliary Carboxylate-Induced Assembly of Calix[6]arene-Polyoxotitanate Hybrid Systems with Photocatalytic Activity in the Oxidation of Sulfides

This study used the tert-butylcalix[6]arene (TBC[6]) as the ligand and successfully synthesized six TBC[6]-stabilized titanium-oxo clusters (TOCs) by the one-step solvothermal reaction. These six compounds were [Ti4O2(TBC[6])2] (Ti4), {Ti2(TBC[6])(EtO)2(SaH2)2} (Ti2-SA, H2Sa = squaric acid), {Ti2(TBC[6])2(EtO)2(Oa)} (Ti2-OA, H2Oa = oxalic acid), [H2Ti4(TBC[6])(BA)2(EtO)10] (Ti4-BA, HBA = benzoic acid), [Ti6O2(TBC[6])(BA)4(OiPr)10] (Ti6-BA), and [Ti8(TBC[6])2(Sal)4(EtO)16] (Ti8-Sal, H2Sal = salicylic acid). These clusters contain one or two TBC[6] ligands, with the biconical or monoconical configuration, greatly increasing the variety of TOCs it could support. The introduction of auxiliary carboxylic ligands can further stimulate the growth of structures, with the cluster core gradually increased from {Ti-TBC[6]-Ti} to {Ti2-TBC[6]-Ti2}, to {Ti3-TBC[6]-Ti3}, and finally to {Ti3-TBC[6]-Ti2-TBC[6]-Ti3} with 3.1 nm length. Structural regulation may affect their solution stability, absorption spectra, and photocurrent response. The study of catalytic activities shows that these clusters can be used as recyclable heterogeneous photocatalysts for the oxidation of sulfide to sulfoxide. The catalytic efficiency of the TBC[6]-Tix system is closely related to the cluster structure, and the exposure of the Ti site on the catalyst surface can significantly enhance the catalytic activity of the clusters.

Influencing Bonding Interactions of the Neptunyl (V, VI) Cations with Electron-Donating and -Withdrawing Groups.

Neptunium makes up the largest percentage of minor actinides found in spent nuclear fuel, yet separations of this element have proven difficult due to its rich redox chemistry. Developing new reprocessing techniques should rely on understanding how to control the Np oxidation state and its interactions with different ligands. Designing new ligands for separations requires understanding how to properly tune a system toward a desired trait through functionalization. Emerging technologies for minor actinide separations focus on ligands containing carboxylate or pyridine functional groups, which are desirable due to their high degree of functionalization. Here, we use DFT calculations to study the interactions of carboxylate and polypyridine ligands with the neptunyl cation [Np(V/VI)O2]+/2+. A systematic study is performed by varying the electronic properties of the carboxylate and polypyridine ligands through the inclusion of different electron-withdrawing and electron-donating R groups. We focus on how these groups can affect geometric properties, electronic structure, and bonding characterization as a function of the metal oxidation state and ligand character and discuss how these factors can play a role in neptunium ligand design principles.

Expanding nonpolar pore surfaces in stable ethane-selective MOF to boost ethane/ethylene separation performance

Ethylene is an important raw material in chemical production. Reducing energy consumption by one-step separation of ethylene from C2H6/C2H4 mixtures is a significant and challenging task. Designing a material with high C2H6 selectivity and adsorption capacity is very demanding. Here, we report a method to improve the performance of C2H6/C2H4 separation. By changing the carboxylic ligand in UiO-67, we synthesized a new material called UiO-67-BN. At room temperature, compared with the base material UiO-67, the optimized material UiO-67-BN has a significant increase in the adsorption capacity of C2H6 and the selectivity of C2H6/C2H4 due to its suitable pore size and numerous non-polar aromatic rings on the pore surface. Theoretical calculation results reveal that the optimized material can provide more C-H∙∙∙π interactions with C2H6. The breakthrough experiments demonstrate that UiO-67-BN can efficiently capture C2H6 from 50/50 and 1/99 C2H6/C2H4 mixtures at various conditions and realize one-step acquisition of C2H4.

Density Functional Theory Guided Investigation of Ligand‐Induced Neptunyl‐Neptunyl Interactions

AbstractActinyl‐actinyl interactions are particularly prevalent for the pentavalent neptunyl cation (Np(V)O2)+where these interactions appear either as aT‐ orD‐shape (diamond‐shape).T‐shaped interactions have been previously identified in high concentration Np(V) solutions containing simple anions (NO3−, ClO4−, Cl−) whereasD‐shaped have only been isolated in the solid‐state in the presence of carboxylate ligands. In this study, Density Functional Theory (DFT) calculations were paired with Raman spectroscopy to evaluate the formation ofD‐shaped interactions in the presence of aliphatic (R=H (formate), CH3(acetate), CH2CH3(propionate)) and aromatic (R=C6H5(benzoate), C6H4OH (4‐hydroxybenzoate), C5H4N (isonicotinate)) carboxylate ligands. DFT studies indicate that the ΔGto form hydratedT‐ andD‐shaped forms are not spontaneous but become so with the addition of the carboxylate ligands. Raman spectra of the Np(V) carboxylate solutions contained vibrational modes associated with theD‐shaped interactions, but spectral changes observed over time indicate a dynamic system. Crystallization experiments from the Np(V) carboxylate systems confirmed the presence ofD‐shaped dimers for the aromatic carboxylates, suggesting that the choice of the anion in solution favors actinyl‐actinyl interactions even at low concentrations (≤20 mM) of Np(V).

Titanium Dioxide Nanoparticle (TiO2 NP) Induces Toxic Effects on LA-9 Mouse Fibroblast Cell Line.

Titanium dioxide nanoparticles (TiO2 NPs) are extensively applied in the industry due to their photocatalytic potential, low cost, and considerably low toxicity. However, new unrelated physicochemical properties and the wide use of nanoparticles brought concern about their toxic effects. Thereby, we evaluated the cytotoxicity of a TiO2 NP composed of anatase and functionalized with sodium carboxylate ligands in a murine fibroblast cell line (LA-9). Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and ATR-FTIR spectroscopy were applied to determine nanoparticle physicochemical properties. The cell viability (MTT assay) and clonogenic survival were analyzed in fibroblasts exposed to TiO2 NP (50, 150, and 250 µg/mL) after 24h. Moreover, oxidative stress, proinflammatory state, and apoptosis were evaluated after 24h. TiO2 NP characterization showed an increased hydrodynamic size (3.57 to 7.62 nm) due to solvent composition and a heterogeneity dispersion in water and cell culture media. Also, we observed a zeta potential increased from -20 to -11 mV in function of protein adsorption. TiO2 NP reduced fibroblast cell viability and induced ROS production at the highest concentrations (150 and 250 µg/mL). Moreover, TiO2 NP reduced the fibroblasts clonogenic survival at the highest concentration (250 µg/mL) on the 7th day after the 24h exposure. Nevertheless, TiO2 NP did not affect the fibroblast proinflammatory cytokines (IL-6 and TNF) secretion at any condition. Early and late apoptotic fibroblast cells were detected only at 150 µg/mL TiO2 NP after 24h. Probably, TiO2 NP photocatalytic activity unbalanced ROS production which induced apoptosis and consequently reduced cell viability and metabolic activity at higher concentrations.