X-ray and DFT-calculated structures of bis[N-(quinolin-8-yl)benzamidato-κ(2)N,N']copper(II).

The application of transition metal chelates as chemotherapeutic agents has the advantage that they can be used as a scaffold around which ligands with DNA recognition elements can be anchored. The facile substitution of these components allows for the DNA recognition and binding properties of the metal chelates to be tuned. Copper is a particularly interesting choice for the development of novel metallodrugs as it is an endogenous metal and is therefore less toxic than other transition metals. The title compound, [Cu(C16H11N2O)2], was synthesized by reacting N-(quinolin-8-yl)benzamide and the metal in a 2:1 ratio. Ligand coordination required deprotonation of the amide N-H group and the isolated complex is therefore neutral. The metal ion adopts a flattened tetrahedral coordination geometry with the ligands in a pseudo-trans configuration. The free rotation afforded by the formal single bond between the amide group and phenyl ring allows the phenyl rings to rotate out-of-plane, thus alleviating nonbonded repulsion between the phenyl rings and the quinolyl groups within the complex. Weak C-H...O interactions stabilize a dimer in the solid state. Density functional theory (DFT) simulations at the PBE/6-311G(dp) level of theory show that the solid-state structure (C1 symmetry) is 79.33 kJ mol(-1) higher in energy than the lowest energy gas-phase structure (C2 symmetry). Natural bond orbital (NBO) analysis offers an explanation for the formation of the C-H...O interactions in electrostatic terms, but the stabilizing effect is insufficient to support the dimer in the gas phase.

Redox behaviour of cymantrene Fischer carbene complexes in designing organometallic multi-tags.

A series of Group 7 Fischer carbene complexes, [Cp(CO)2 Mn(I) =C(OEt)Ar] (Cp=cyclopentadienyl, Ar=Th=thienyl (1 a), Ar=Fu=furyl (2 a), Ar=Fc=ferrocenyl (3 a)) and biscarbene complexes, [Cp(CO)2 MnC(OEt)Ar'(OEt)CMn(CO)2 Cp] (Ar'=Th'=2,5-thienylene (1 b), Ar'=Fu'=2,5-furylene (2 b), Ar'=Fc'=1,1'-ferrocendiyl (3 b)) was synthesized and characterized. Chemical oxidation of [Cp(CO)2 MnC(OEt)Fc] (3 a) and isolation of the oxidised species [3 a][PF6 ] possessing a Mn(II) centre proved possible below -30 °C in dichloromethane solution. The ESR spectrum of the transiently stable radical cation, [3 a][PF6 ], confirmed the presence of a low-spin Mn(II) centre characterized by a rhombic g tensor (gx =1.975, gy =2.007 and gz =2.130) in frozen dichloromethane at 77 K with (55)  Mn hyperfine coupling constants A1 , A2 and A3 of 115, 33 and 43 G, respectively. Electrochemical studies demonstrated the influence of the Ar substituent on the oxidation potential. All complexes showed that the redox potentials of carbene double bond reduction and Mn(I) oxidation were dependent on the type of Ar group, but only 3 b showed resolved oxidations for the two Mn(I) centres. Surprisingly, Mn(I) oxidation occurs at lower potentials than ferrocenyl oxidation. Density functional theory (DFT) calculations were carried out to delineate the nature of the species involved in the oxidation and reduction processes and clearly confirm that oxidation of Mn(I) is favoured over that of ferrocene.