The 2D–3D networks with infinite channels or difform chains of copper(II) complexes via weak non-covalent interactions

Pyridine-2,6-Dicarboxylic Acid Esters (pydicR2) as O,N,O-Pincer Ligands in CuII Complexes

The pyridine-2,6-carboxylic esters pydicR2 with R = Me or Ph form the unprecedented mononuclear CuII complexes [Cu(pydicR2)Cl3]− in one-pot reactions starting from pyridine-2,6-carboxychloride pydicCl2, CuII chloride, and NEt3 in MeOH or PhOH solution under non-aqueous conditions. The triethylammonium salts (HNEt3)[Cu(pydicR2)Cl3] were isolated. The methyl derivative could be crystallized to allow a XRD structure determination. Both structures were optimized using DFT calculations in various surroundings ranging from gas phase and the non-coordinating solvent CH2Cl2 to the weakly coordinating acetone and well-coordinating solvents acetonitrile (MeCN) or dimethylformamide (DMF), while detailed calculation showed the charge distribution, dipole moments, and HOMO–LUMO gap energies changing upon solvation. According to these calculations, the ion pairs and the anionic CuII complexes were stable, which shows only Cu–Cl bond elongation and weakening of the charge transfer between the anionic complex and the cation as solvents become polar. Synthesis attempts in the presence of water yielded the CuII complexes [Cu(pydic)(OH2)2]n and [Cu(OH2)6][{Cu(pydic)}2(µ-Cl)2], which results from pydicCl2 hydrolysis. Alternatively, the new pydic(IPh)2 (IPh = 2-iodo-phenyl) ester ligand was synthesized and reacted with anhydrous CuCl2, which yields the new binuclear complex [{Cu(pydic(IPh)2)Cl}2(µ-Cl)2]. EPR spectroscopy of the solid compounds reveals typical axial spectra in line with the observed and DFT calculated geometries. Cyclic voltammetry and UV–vis absorption spectroscopy in solution are in line with un-dissociated complex species [Cu(pydicR2)Cl3]−.

Anticancer copper(II) phosphorus dendrimers are potent proapoptotic Bax activators

A multivalent phosphorus dendrimer 1G₃ and its corresponding Cu-complex, 1G₃-Cu have been recently identified as agents retaining high antiproliferative potency. This antiproliferative capacity was preserved in cell lines overexpressing the efflux pump ABC B1, whereas cross-resistance was observed in ovarian cancer cell lines resistant to cisplatin. Theoretical 3D models were constructed: the dendrimers appear as irregularly shaped disk-like nano-objects of about 22 Å thickness and 49 Å diameter, which accumulated in cells after penetration by endocytosis. To get insight in their mode of action, cell death pathways have been examined in human cancer cell lines: early apoptosis was followed by secondary necrosis after multivalent phosphorus dendrimers exposure. The multivalent plain phosphorus dendrimer 1G₃ moderately activated caspase-3 activity, in contrast with the multivalent Cu-conjugated phosphorus dendrimer 1G₃-Cu which strikingly reduced the caspase-3 content and activity. This decrease of caspase activity is not related to the presence of copper, since inorganic copper has no or little effect on caspase-3. Conversely the potent apoptosis activation could be related to a noticeable translocation of Bax to the mitochondria, resulting in the release of AIF into the cytosol, its translocation to the nucleus and a severe DNA fragmentation, without alteration of the cell cycle. The multivalent Cu-conjugated phosphorus dendrimer is more efficient than its non-complexed analog to activate this pathway in close relationship with the higher antiproliferative potency. Therefore, this multivalent Cu-conjugated phosphorus dendrimer 1G₃-Cu can be considered as a new and promising first-in-class antiproliferative agent with a distinctive mode of action, inducing apoptosis tumor cell death through Bax activation pathway.

Organometallic Polymers Assembled from Cation–π Interactions: Use of Ferrocene as a Ditopic Linker Within the Homologous Series [{(Me3Si)2NM}2⋅(Cp2Fe)]∞ (M=Na, K, Rb, Cs; Cp=cyclopentadienyl)

Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me(3)Si)(2)NM}(2) (Cp(2)Fe)](infinity) (1-4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1-4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}(2)] aggregates, which are bridged through neutral ferrocene molecules by eta(5)-cation-pi interactions. In addition, compounds 3 and 4 also contain interchain agostic M--C interactions, producing two-dimensional 4(4)-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me(3)Si)(2)NM)(2)}(2) (Cp(2)Fe)(x)(Tol)(y)](infinity) (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 4(4)-sheets 3 and 4, but are now assembled from a combination of cation-pi, agostic, and pi-pi interactions. The charge-separated complex [K{(C(6)H(6))(2)Cr}(1.5)(Mes)][Mg(HMDS)(3)] (15) was also structurally characterized and found to adopt an anionic two-dimensional 6(3)-network through doubly eta(3)-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6-31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation-pi contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation-pi donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.