Deeb Taher

The role of Fe–X···X–Fe contacts in the crystal structures of [(2-iodopyridinium)2FeX4]X (X = Cl, Br)

The analogy of chloride–chloride contacts in compounds containing Fe–Cl1···Cl2–Fe synthons with well-studied organic C–Cl1···Cl2–C interactions has been investigated. The crystal structures of the two tetrahaloferrate(III) salts, [(2-iodopyridinium)2FeX4]X (Xxa0=xa0Cl, Br) have been determined. Analysis of these two isomorphous structures and related published structures shows that the arrangement of Fe–Cl1···Cl2–Fe synthons is similar to that of C–Cl1···Cl2–C with the Fe–Cl1···Cl2 and Cl1···Cl2–Fe angles being ~150°. While inter-chlorine distances are less than the sum of van der Waals radii in C–Cl1···Cl2–C units, they are equal to, or longer, than the sum of van der Waals radii in the corresponding Fe–Cl1···Cl2–Fe contacts. This might indicate that the arrangement of Fe–Cl1···Cl2–Fe synthons occurs predominately to reduce repulsive forces rather than as a result of attractive forces. However, it is observed that the halide–halide distance in [(2-iodopyridinium)2FeBr4]Br is shorter than in the isostructural chloride species, which can be explained by the fact that bromine is softer than chlorine. Several intermolecular forces unite the cations and anions within the crystalline lattice of [(2-iodopyridinium)2FeX4]X including N–H···X−, C–I···X–Fe, N(π)···X–Fe, N(π)···I–C, and Fe–X1···X2–Fe contacts. The calculated electron density and electrostatic potential of the [FeX4]− anions and the organic iodopyridinium cations was used to describe the arrangement of these synthons and the hierarchy of the strengths of the respective contacts.

Ruthenium(II) complexes of azoimine and α-diimine ligands: synthesis, spectroscopic and electrochemical properties, crystal structures and DFT calculations

Five octahedral ruthenium(II) complexes with azoimine–quinoline (Azo) and α-diimine (L) ligands having the general formula [RuII(L)(Azo)Cl](PF6) (1–5) {Azo:xa0PhN=NC(COMe)=NC9H6N, Lxa0=xa04,4′-dimethoxy-2,2′-bipyridine (dmeb) (1), 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H2Azo) and α-diimine (L) pro-ligands to RuCl3 in refluxing EtOH. The tridentate azoimine–quinoline ligands coordinate to ruthenium via the Azo-N′, N′-imine and N″-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, 1H, 13C and 19F NMR) and electrochemical behavior of complexes 1–5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong π-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63–1.72xa0V versus NHE. The electronic spectra in MeCN and IR spectra in CH2Cl2 for complex 3 in its oxidized 3+ and reduced 3− forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV–Vis absorption bands.

4-(4-Nitro­benz­yl)pyridine

The title compound, C12H10N2O2, has a twisted conformation, with a dihedral angle between the planes of the pyridine and benzene rings of 78.4u2005(2)°. The nitro group is coplanar with the attached benzene ring within experimental error. The molecules form centrosymmetric dimers via Car—H⋯O interactions (H⋯O = 2.49u2005Å) and the dimers are π-stacked along the b axis [the separation between ring centroids is 3.788u2005(2)u2005Å].