Electronic Control of the Scholl Reaction: Selective Synthesis of Spiro vs Helical Nanographenes.

Scholl oxidation has become an essential reaction in the bottom-up synthesis of molecular nanographenes. Herein, we describe a Scholl reaction controlled by the electronic effects on the starting substrate (1 a, b). Anthracene-based polyphenylenes lead to spironanographenes under Scholl conditions. In contrast, an electron-deficient anthracene substrate affords a helically arranged molecular nanographene formed by two orthogonal dibenzo[fg,ij]phenanthro-[9,10,1,2,3-pqrst]pentaphene (DBPP) moieties linked through an octafluoroanthracene core. Density Functional Theory (DFT) calculations predict that electronic effects control either the first formation of spirocycles and subsequent Scholl reaction to form spironanographene 2, or the expected dehydrogenation reaction leading solely to the helical nanographene 3. The crystal structures of four of the new spiro compounds (syn 2, syn 9, anti 9 and syn 10) were solved by single crystal X-ray diffraction. The photophysical properties of the new molecular nanographene 3 reveal a remarkable dual fluorescent emission.

Antitumoral potential of carbamidocyclophanes and carbamidocylindrofridin A isolated from the cyanobacterium Cylindrospermum stagnale BEA 0605B.

Three carbamidocyclophanes, A, F and V, and carbamidocylindrofridin A were isolated from the cultured freshwater cyanobacterium Cylindrospermum stagnale, collected in the Canary Islands. The chemical structures of these compounds were elucidated through NMR, HRMS and ECD spectroscopy. The absolute configuration of carbamidocyclophane A was confirmed using X-ray-diffraction. All compounds showed apoptotic capacity against the SK-MEL-1, SK-MEL-28 and SK-MEL-31 tumour cells. Carbamidocylindrofridin A had the highest anti-tumour potential, with an IC50 of 1 ± 0.3 µM in the SK-MEL-1 cell line.

Novel structures of platinum complexes bearing N­bisphosphonates and study of their biological properties.

Novel bisphosphonate platinum complexes: [Pt(isopropylamine)2(BP)]NO3 (BP = pamidronate and alendronate) have been synthesized and characterized. Their monomeric structure contains a bisphosphonate acting as chelate ligand through its oxygen atom donors, conferring the compound's cationic structure with a good solubility in water. The study of the compounds in solution showed high stability up to 24 h. The cytotoxicity in cancer cell lines has been assessed. We also present preliminary studies on the evaluation of the affinity towards biological targets such as DNA (both calf thymus DNA and supercoiled plasmid DNA) and hydroxyapatite where the complexes showed a low DNA interaction, but a clear affinity for hydroxyapatite comparing to their precursors.

Coordination capacity of cytosine, adenine and derivatives towards open-paddlewheel diruthenium compounds.

[Ru2Cl2(DPhF)3] (DPhF = diphenylformamidinate) links preferentially to the junctions of RNA (ribonucleic acid) structures, although the bonding mode is not known. In order to clarify this question the reactions between [Ru2Cl2(DPhF)3] and cytosine (Hcyto), cytidine (Hcyti), cytidine 2',3'-cyclic monophosphate sodium salt (NacCMP), adenine (Hade), adenosine (Haden) and adenosine 3',5'-cyclic monophosphate (HcAMP) have been carried out. In the resultant complexes, cyto (cytosinate), cyti (cytidinate), cCMP (cytidine 2',3'-cyclic monophosphate monoanion), ade (adeninate), aden (adenosinate) and cAMP (deprotonated adenosine 3',5'-cyclic monophosphate) are bonded to the diruthenium unit as N,N'-bridging ligands, as confirmed by the solution of the crystal structures of [RuCl(DPhF)3(cyto)] and [RuCl(DPhF)3(ade)] by X-ray diffraction. The axial positions of the diruthenium species are still available for additional interactions with other residues that could explain its preference towards RNA junctions.

Synthesis, cytotoxicity, DNA interaction and cell cycle studies of trans-diiodophosphine Pt(II) complexes.

Platinum complexes, bearing aliphatic amines and phosphine ligands in trans configuration with iodide as leaving groups, are synthesized and characterized. The crystal structure of trans-PtI2(isopropylamine)(PPh3) is reported. The complex bearing isopropylamine is demonstrated to be the best candidate as its cytotoxic activity is comparable to or better than cisplatin. A remarkably higher interaction of the complexes with DNA is reported as compared to the parent chlorido series. Cell cycle studies of the complexes in six human cell lines are performed and also compared with the previous series.

Crystal structure of poly[[trans-di-aqua-bis-[µ2-trans-4,4'-(diazenedi-yl)dipyridine]-nickel(II)] diiodide ethanol disolvate].

In the title compound, {[Ni(C10H8N4)2(H2O)2]I2·2C2H5OH} n , the complex shows an octa-hedral environment of the Ni(2+) cation in which it is located on a centre of symmetry, linked to two water mol-ecules and the pyridine-N atoms of four 4,4'-(diazenediyl)dipyridine ligands bridging Ni(2+) cations along the b- and c-axis directions, giving rise to a two-dimensional arrangement. The Ni-N bond lengths are in the range 2.109 (4)-2.186 (3) Šand the Ni-O bond length is 2.080 (3) Å. The 4,4'-(diazenedi-yl)dipyridine ligand lies on an inversion centre. An O-H⋯O hydrogen-bond inter-action is observed between water and ethanol mol-ecules. The I(-) ions can be regarded as free anions in the crystal lattice.

Oxidation of anticancer Pt(II) complexes with monodentate phosphane ligands: towards stable but active Pt(IV) prodrugs.

The synthesis, characterization and cytotoxicity studies of two novel platinum(IV) complexes, trans-PtCl4(dma)(PPh3), 1, and trans-PtCl4(ipa)(PPh3), 2, where dma is dimethylamine and ipa is isopropylamine, have been carried out. Both complexes contain aliphatic amines trans to phosphane ligands as a good alternative to take advantage of the phosphane group lipophilicity and the stability of platinum(IV) to obtain more effective drugs. Moreover, the complexes are stable in solution and such stability allowed their antitumoral action and DNA interaction to be checked and proved.

New palladium and platinum complexes with bioactive 3,5-diacetyl-1,2,4-triazol bis(4-cyclohexyl thiosemicarbazone) ligand: chemistry, antiproliferative activity and preliminary toxicity studies.

The preparation and characterization of the new 3,5-diacetyl-1,2,4-triazol bis(4-cyclohexyl thiosemicarbazone) ligand, H(5)L(1), is described. Treatment of H(5)L(1) with K(2)PtCl(4) gave the dinuclear complex [Pt(H(3)L(1))](2), 1, but using MCl(2)(PPh(3))(2) where M = Pd or Pt, mononuclear complexes 2 and 3, of general formula [M(H(3)L(1))PPh(3)], were obtained. Subsequent reaction of the [Pd(H(3)L(1))PPh(3)] complex with PdCl(2)(PPh(3))(2) yielded a new dinuclear complex [(PPh(3))Pd(H(2)L(1))PdCl], 4. All compounds have been characterized by elemental analysis and FAB(+) spectrometry and by IR and NMR spectroscopy. The molecular structures of mononuclear complexes 2 and 3 and dinuclear complex 4 have been determined by X-ray crystallography. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, HepG2, MCF-7, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that the H(5)L(1) ligand and [Pt(H(3)L(1))](2), complex 1, may be endowed with important cytotoxic properties since they are capable of not only circumventing cisplatin resistance in A2780cisR but also exhibit antiproliferative activity in NCI-H460. The interactions of these compounds with calf thymus DNA were investigated by UV-vis absorption and a nephrotoxic study, in LLC-PK1 cells, has also been carried out.