The ionic metallocene complexes [Cp*(2)M][BPh(4)] (Cp* = C(5)Me(5)) of the trivalent 3d metals Sc, Ti, and V were synthesized and structurally characterized. For M = Sc, the anion interacts weakly with the metal center through one of the phenyl groups, but for M = Ti and V, the cations are naked. They each contain one strongly distorted Cp* ligand, with one (V) or two (Ti) agostic C-H...M interactions involving the Cp*Me groups. For Sc and Ti, these Lewis acidic species react with fluorobenzene and 1,2-difluorobenzene to yield [Cp*(2)M(kappaF-FC(6)H(5))(n)][BPh(4)] (M = Sc, n = 2; M = Ti, n = 1) and [Cp*(2)M(kappa(2)F-1,2-F(2)C(6)H(4))][BPh(4)], the first examples of kappaF-fluorobenzene and kappa(2)F-1,2-difluorobenzene adducts of transition metals. With the perfluorinated anion [B(C(6)F(5))(4)](-), both Sc and Ti form [Cp*(2)M(kappa(2)F-C(6)F(5))B(C(6)F(5))(3)] contact ion pairs. The nature of the metal-fluoroarene interaction was studied by density functional theory (DFT) calculations and by comparison with the corresponding tetrahydrofuran (THF) adducts and was found to be predominantly electrostatic for all metals studied.

A mesoporous silica (SBA-15) has been chemically modified with 2-mercaptopyrimidine using the homogeneous route. This synthetic route involved the reaction of 2-mercaptopyrimidine with 3-chloropropyltriethoxysilane prior to immobilization on the support. The resulting material has been characterized by powder X-ray diffraction, nitrogen gas sorption, FT-IR and MAS NMR spectroscopy, thermogravimetry and elemental analysis. The solid was employed as a Cd(II) adsorbent from aqueous solutions at room temperature. The effects of several variables (stirring time, pH, metal concentration and presence of other ions in the medium) have been studied using the batch technique. Flame atomic absorption spectrometry was used to determine the Cd(II) concentration in the filtrate after the adsorption process. The results indicate that under the optimum conditions, the maximum adsorption value for Cd(II) was 0.99 ¡ 0.03 mmol Cd(II) g 21 , whereas the adsorption capacity of the unmodified mesoporous silica was only 0.04 ¡ 0.02 mmol Cd(II) g 21 . On the basis of these results, it can be concluded that it is possible to modify chemically SBA-15 with 2-mercaptopyrimidine and to use the resulting modified mesoporous silica as an effective adsorbent for Cd(II) in aqueous media.

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Dehydroxylated MCM-41 and SBA-15 surfaces were modified by the grafting of two different titanocene complexes ([Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)]) to give new materials, which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, MAS-NMR spectroscopy, thermogravimetry, SEM, and TEM. The toxicity of the resulting materials toward human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, such as peripheral blood mononuclear cells PBMC has been studied. Estimation of the number of particles per gram of material led to the calculation of Q(50) values for these samples, which is the number of particles required to inhibit normal cell growth by 50%. In addition, M(50) values (quantity of material needed to inhibit normal cell growth by 50%) of the studied surfaces is also reported. Nonfunctionalized MCM-41 and SBA-15 did not show notable antiproliferative activity, whereas functionalization of these materials with different titanocene based anticancer drugs led to very promising antitumoral activity. The best Q(50) values correspond to titanocene functionalized MCM-41 surfaces (MCM-41/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (1) and MCM-41/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (2)) with Q(50) values between 3.8+/-0.6x10(8) and 24.5+/-3.0x10(8) particles. Titanocene functionalized SBA-15 surfaces (SBA-15/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (3) and SBA-15/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (4)) gave higher Q(50) values, showing lower activity from 73.2+/-9.9x10(8) to 362+/-7x10(8) particles. The best response of the studied materials in terms of M(50) values was observed against Fem-x (309+/-42 microg for 4) and K562 (338+/-18 microg for 2), whereas moderate activities were observed in HeLa cells (from 508+/-63 microg of 2 to 912+/-10 microg of 1). In addition, the analyzed surfaces presented only marginal activity against unstimulated and stimulated PBMC, showing a slight selectivity on human cancer cells. Comparison of the in vitro cytotoxicity in solution of the titanocene complexes [Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] and the corresponding titanocene functionalized materials is also described.

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