Cellular internalisation, bioimaging and dark and photodynamic cytotoxicity of silica nanoparticles doped by {Mo₆I₈}⁴⁺ metal clusters

Silica nanoparticles (SNPs) doped by hexanuclear molybdenum cluster complexes [{Mo₆X₈}L₆]n (X = Cl, Br, or I; L = various inorganic or organic ligands) have been recently suggested as materials with a high potential for biomedical applications due to both the outstanding photoluminescent properties and the ability to efficiently generate singlet oxygen upon photoirradiation. However, no studies were undertaken so far to prove this concept. Therefore, here we examined the potential of photoluminescent SNPs doped by {Mo₆I₈}⁴⁺ for such applications as bioimaging and photodynamic therapy using human epidermoid larynx carcinoma (Hep-2) cell line as a model. Our results demonstrated both: (i) significant luminescence from cells with internalised molybdenum cluster doped SNPs combined with the low cytotoxicity of particles in the darkness and (ii) significant cytotoxicity of the particles upon photoirradiation. Thus, this research provides strong experimental evidence for high potential of molybdenum cluster doped materials in such biomedical applications as optical bioimaging, biolabeling and photodynamic therapy

Electrochemical properties and radical anions of carbocycle-fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline (1) and its derivatives bearing various substituents R (7‐H (2), 7,8‐H2 (3), 6‐CF3 (4), 6‐Cl (5), 5,7‐Cl2 (6), 5‐NH2 (7), 6‐OCH3 (8), 6,7‐(OCH3)2 (9), 6,7,8‐(OCH3)3 (10), 5,6,7,8‐(OCH3)4 (11), 6‐OCH3,7‐N(CH3)2 (12), 6‐N(CH3)2 (13), 6,7‐(N(CH3)2)2 (14), 5,6,7‐(N(CH3)2)3 (15), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) (16)) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1–4 and 7–15, the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4–6 and 15, 16. Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H2 derivative of 1 (17) at the next steps. Electrochemically generated RAs of 1–3, 7–14, and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1–15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1–15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1–5 and 7–14 has been found to be irreversible

Electrochemical properties and radical anions of carbocycle-fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline (1) and its derivatives bearing various substituents R (7‐H (2), 7,8‐H2 (3), 6‐CF3 (4), 6‐Cl (5), 5,7‐Cl2 (6), 5‐NH2 (7), 6‐OCH3 (8), 6,7‐(OCH3)2 (9), 6,7,8‐(OCH3)3 (10), 5,6,7,8‐(OCH3)4 (11), 6‐OCH3,7‐N(CH3)2 (12), 6‐N(CH3)2 (13), 6,7‐(N(CH3)2)2 (14), 5,6,7‐(N(CH3)2)3 (15), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) (16)) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1–4 and 7–15, the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4–6 and 15, 16. Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H2 derivative of 1 (17) at the next steps. Electrochemically generated RAs of 1–3, 7–14, and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1–15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1–15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1–5 and 7–14 has been found to be irreversible