Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: Se2B17H17 (1), SeB17H19 (3) and SeB18H20 (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes S2B17H17 (2), n-S2B16H16 (5) and i-S2B16H16 (6) were synthesised and also found to exhibit a range of luminescent properties. These macropolyhedral species are very different from the previously unique fluorescent binary borane B18H22 in terms of their structural architectures, by the presence of borane cluster hetero atoms, and, as in the cases of 5 and 6, that their synthetic origins are not derived simply through the modification of B18H22 itself. They consequently greatly expand the possibilities of finding new luminescent inorganic borane species.

Chemistry of Carbon-Substituted Derivatives of Cobalt Bis(dicarbollide)(1-) Ion and Recent Progress in Boron Substitution.

The cobalt bis(dicarbollide)(1-) anion (1-), [(1,2-C2B9H11)2-3,3'-Co(III)](1-), plays an increasingly important role in material science and medicine due to its high chemical stability, 3D shape, aromaticity, diamagnetic character, ability to penetrate cells, and low cytotoxicity. A key factor enabling the incorporation of this ion into larger organic molecules, biomolecules, and materials, as well as its capacity for "tuning" interactions with therapeutic targets, is the availability of synthetic routes that enable easy modifications with a wide selection of functional groups. Regarding the modification of the dicarbollide cage, syntheses leading to substitutions on boron atoms are better established. These methods primarily involve ring cleavage of the ether rings in species containing an oxonium oxygen atom connected to the B(8) site. These pathways are accessible with a broad range of nucleophiles. In contrast, the chemistry on carbon vertices has remained less elaborated over the previous decades due to a lack of reliable methods that permit direct and straightforward cage modifications. In this review, we present a survey of methods based on metalation reactions on the acidic C-H vertices, followed by reactions with electrophiles, which have gained importance in only the last decade. These methods now represent the primary trends in the modifications of cage carbon atoms. We discuss the scope of currently available approaches, along with the stereochemistry of reactions, chirality of some products, available types of functional groups, and their applications in designing unconventional drugs. This content is complemented with a report of the progress in physicochemical and biological studies on the parent cobalt bis(dicarbollide) ion and also includes an overview of recent syntheses and emerging applications of boron-substituted compounds.

A Window into the Workings of anti-B18H22 Luminescence-Blue-Fluorescent Isomeric Pair 3,3'-Cl2-B18H20 and 3,4'-Cl2-B18H20 (and Others).

The action of AlCl3 on room-temperature tetrachloromethane solutions of anti-B18H22 (1) results in a mixture of fluorescent isomers, 3,3'-Cl2-B18H20 (2) and 3,4'-Cl2-B18H20 (3), together isolated in a 76% yield. Compounds 2 and 3 are capable of the stable emission of blue light under UV-excitation. In addition, small amounts of other dichlorinated isomers, 4,4'-Cl2-B18H20 (4), 3,1'-Cl2-B18H20 (5), and 7,3'-Cl2-B18H20 (6) were isolated, along with blue-fluorescent monochlorinated derivatives, 3-Cl-B18H21 (7) and 4-Cl-B18H21 (8), and trichlorinated species 3,4,3'-Cl3-B18H19 (9) and 3,4,4'-Cl3-B18H19 (10). The molecular structures of these new chlorinated derivatives of octadecaborane are delineated, and the photophysics of some of these species are discussed in the context of the influence that chlorination bears on the luminescence of anti-B18H22. In particular, this study produces important information on the effect that the cluster position of these substitutions has on luminescence quantum yields and excited-state lifetimes.

Bipyridine Ruthenium(II) Complexes with Halogen-Substituted Salicylates: Synthesis, Crystal Structure, and Biological Activity.

Ruthenium complexes currently represent a perspective subject of investigation in terms of potential anticancer therapeutics. Eight novel octahedral ruthenium(II) complexes are the subject of this article. Complexes contain 2,2'-bipyridine molecules and salicylates as ligands, differing in position and type of halogen substituent. The structure of the complexes was determined via X-ray structural analysis and NMR spectroscopy. All complexes were characterized by spectral methods-FTIR, UV-Vis, ESI-MS. Complexes show sufficient stability in solutions. Therefore, their biological properties were studied. Binding ability to BSA, interaction with DNA, as well as in vitro antiproliferative effects against MCF-7 and U-118MG cell lines were investigated. Several complexes showed anticancer effects against these cell lines.

Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B18H22.

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn- and anti-isomers of B18H22 with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeB18H19]- anion 1, 19-vertex [SeB18H21]- anion 2, 20-vertex [Se2B18H19]- anion 3, and 19-vertex [Se2B17H18]- anion 4. Single-cluster [hypho-Se2B6H9]- anion 5 and neutral arachno-Se2B7H9 6 also result. All of the macropolyhedrals 1, 2, 3, and 4 are characterized by NMR spectroscopy and mass spectrometry, and by single-crystal X-ray diffraction analyses. Anions 1 and 2 each consist of an 11-vertex subcluster joined by a common two-boron edge to a 10-vertex subcluster. Anion 3 consists of an 11-vertex subcluster joined by a common boron atom and an interboron link to an arachno-type 10-vertex subcluster. Unusually, anion 3 incorporates a hexagonal pyramidal intracluster structural motif in its 11-vertex subcluster. Anion 4 entails two arachno-type 10-vertex subclusters joined by a common boron atom, and with an additional intercluster boron-boron link. NMR data for syn-B18H22 and its mono- and dianions 7 and 8 and single-crystal X-ray diffraction results for these anions and also the monoanion 9 of anti-B18H22 are also reported. The oxaborane [µ-(8,9)-O-syn-B18H20]2- dianion 10 was serendipitously formed during the work and also characterized by a single-crystal X-ray diffraction study. Experimental NMR and structural findings are supported by DFT calculations throughout.

Low-dimensional compounds containing bioactive ligands. Part XIV: High selective antiproliferative activity of tris(5-chloro-8-quinolinolato)gallium(III) complex against human cancer cell lines.

Four gallium(III) complexes, [Ga(ClQ)3]⋅MeOH (1 - MeOH), [Ga(ClQ)3] (1), [Ga(BrQ)3] (2), [Ga(dIQ)3] (3) and [Ga(CQ)3] (4), were prepared (H-ClQ = 5-chloro-8-quinolinol, H-BrQ = 7-bromo-8-quinolinol, H-dIQ = 5,7-diiodo-8-quinolinol, H-CQ = 5-chloro-7-iodo-8-quinolinol) and characterised by elemental analysis, IR and NMR spectroscopy. Single crystal structure analysis of 1 - MeOH confirmed that the complex has a molecular structure with gallium(III) metal ion coordinated in mer-fashion by N- and O-donor atoms of three ClQ ligands. Stability of all complexes in DMSO was proved by 1H NMR spectroscopy. The in vitro antiproliferative activity of 1 was evaluated against the A2780, MBA-MB-231 and HCT116 cell lines. Complex 1 displays higher antiproliferative activity (IC50 values in the range 2.1-6 µm) compared to the ClQ ligand and cisplatin; and a significant selective antiproliferative potency (IC50 = 136 µm, for normal MRC5pd30 cell line). Radical scavenging experiments revealed that complex 1 exhibits the highest antioxidant activity of the prepared complexes as well as the ligands.

Correction: Synthetic routes to carbon substituted cobalt bis(dicarbollide) alkyl halides and aromatic amines along with closely related irregular pathways.

Correction for 'Synthetic routes to carbon substituted cobalt bis(dicarbollide) alkyl halides and aromatic amines along with closely related irregular pathways' by Jan Nekvinda et al., Dalton Trans., 2024, 53, 5816-5826, https://doi.org/10.1039/D4DT00072B.

Synthetic routes to carbon substituted cobalt bis(dicarbollide) alkyl halides and aromatic amines along with closely related irregular pathways.

Carbon substituted cobalt bis(dicarbollide) alkyl halides [(1-X-(CH2)n-1,2-C2B9H10)(1,2-C2B9H11)-3,3'-Co]Me4N (X = Br, I; n = 1-3) are prepared in high yields (>90%) from their corresponding alcohols without side skeletal substitutions. These species offer access to the synthesis of aromatic cobalt bis(dicarbollide) amines, however only for particular terminal halogen substitution, the propylene pendant arm, and under appropriately controlled reaction conditions. Thus, the compounds substituted at cage carbon atoms with a propylene linker and terminal aromatic amine groups could be prepared. In other cases, numerous irregular reaction pathways occur, undoubtedly as a consequence of the bulky anionic boron cage in close proximity to the reaction site. Among them, an unusual intramolecular hydroboration forming rigidified carbon-to-boron bridged isomeric anions with an asymmetric structure that correspond to formulae [(1,8'-µ-C2H4)-(1,2-C2B9H10)(1',2'-C2B9H10)-3,3'-Co]- and [(1,7'-µ-C2H4)-(1,2-C2B9H10)(1',2'-C2B9H10)-3,3'-Co]- is described herein and the former isomer is structurally characterized. This product with a restrained geometry is widely accessible through nucleophile and/or thermally induced decomposition of (pseudo)halides attached to the cage via an ethylene linker. Surprisingly enough, also doubly bridged isomeric species [(1,8-µ-C2H4-1,2-C2B9H9)2-3,3'-Co]- and [(1,7-µ-C2H4-1,2-C2B9H9)2-3,3'-Co]- are available in good yield using these methods. Furthermore, other more typical side reactions are discussed, i.e. nucleophilic reactions of propyl halides with Me3N formed apparently by disproportionation of Me4N+ at higher temperatures or with pyridine used as a base.

Synthetic Chameleon Turns into Oximes, Nitrones, and Hydroxylamines when Exposed to Blue Light.

A metal-free, user-friendly photochemical transformation of nitroalkanes to oximes, nitrones, and hydroxylamines has been developed. The visible-light-induced reactions are catalyzed by the readily available photoredox organocatalyst 4CzIPN and use inexpensive amines as reductants. Broad in scope and tolerant of multiple functional groups and heterocycles, the transformation proceeds under mild conditions. Its synthetic potential was demonstrated in the formal total synthesis of amathaspiramide F. A basic insight into the reaction mechanism was gained with the help of an NMR study.

Stabilization of propene molybdenum and tungsten half-sandwich complexes by intramolecular coordination of a thioether function.

This study reports the stabilizing effect of an intramolecularly coordinated thioether function in propene complexes of the general formula [{η5:κS-C5H4(CH2)2SR}M(CO)2(η2-C2H3Me)][BF4] (M = Mo, W; R = Et, Ph). They are formed by protonation of allyl analogues [{η5-C5H4(CH2)2SR}M(CO)2(η3-C3H5)] by tetrafluoroboric acid in non-coordinating solvents. In contrast to analogues with unsubstituted Cp ligands, these propene complexes are isolable in a pure form and characterized by NMR spectroscopy. The molybdenum compounds are stable at low temperature and the propene ligand can easily be exchanged by thioethers or acetonitrile. Several representatives of the reaction products were characterized by X-ray structure analysis. The stabilization effect in tungsten complexes [{η5:κS-C5H4(CH2)2SR}W(CO)2(η2-C2H3Me)][BF4] (R = Et, Ph) was unusually high. The compounds are long-term stable at room temperature and do not undergo ligand exchange reactions even with strong chelators such as 1,10-phenanthroline. The molecular structure of the tungsten propene complex was confirmed by X-ray diffraction analysis on a single crystal.

Antimicrobially Active Zn(II) Complexes of Reduced Schiff Bases Derived from Cyclohexane-1,2-diamine and Fluorinated Benzaldehydes-Synthesis, Crystal Structure and Bioactivity.

A series of Schiff base ligands obtained by the condensation of trans-cyclohexane-1,2-diamine and fluorinated benzaldehydes were prepared, followed by their reduction with NaBH4. The reduced ligands were employed in the synthesis of zinc complexes of the general formula [ZnCl2(L)]. The structures of both the original and the reduced Schiff bases, as well as of the zinc complexes, were characterized by single-crystal X-ray analysis, along with NMR and IR spectroscopy. The antimicrobial activities of the reduced Schiff bases and their zinc complexes were evaluated in vitro against E. coli, S. aureus, and C. albicans. The compounds containing the 4-(trifluoromethylphenyl) moiety showed marked antibacterial activity. Interestingly, the antimicrobial effect of the zinc complex with this moiety was significantly higher than that of the corresponding free reduced ligand, comparable with ciprofloxacin used as standard. Thus, a synergic effect upon the complexation with zinc can be inferred.

Interaction of Adenosine, Modified Using Carborane Clusters, with Ovarian Cancer Cells: A New Anticancer Approach against Chemoresistance.

Platinum compounds remain the first-line drugs for the treatment of most lethal gynecological malignancies and ovarian cancers. Acquired platinum resistance remains a major challenge in gynecological oncology. Considering the unique physicochemical properties of the metallacarboranes modifier and the significant role of nucleoside derivatives as anticancer antimetabolites, we designed and synthesized a set of adenosine conjugates with metallacarboranes containing iron, cobalt, or chromium as semi-abiotic compounds that influence the cisplatin sensitivity of ovarian cancer cells. Adherent cultures of ovarian carcinoma cell lines and multicellular spheroids, ranging from sensitive to highly resistant including experimental cell lines "not responding" to platinum drugs were used. Iron-containing metallacarborane conjugates showed the best anticancer activity, especially against resistant cells. Compound modified at the C2' nucleoside position showed the best activity in resistant cancer cells and highly resistant cancer spheroids exposed to cisplatin, increasing cell cycle arrest, apoptosis or necrosis, and reactive oxygen species production. Moreover, it showed high cellular accumulation and did not induce cross-resistance to cisplatin, carboplatin, doxorubicin, paclitaxel, or gemcitabine in long-term cultures. The reference nido-carborane derivative (no metal ions) and unmodified nucleosides were not as effective. These findings indicate that metallacarborane modification of adenosine may sensitize ovarian cancer cells to cisplatin in combination treatment.