Organometallic ruthenium (η6-p-cymene) complexes interfering with quorum sensing and biofilm formation: an anti-infective approach to combat multidrug-resistance in bacteria

Organometallic ruthenium complexes of flavonoids as antiquorum sensing agents against pathogens likeChromobacterium violaceumATCC 12472,Pseudomonas aeruginosaPAO1 and methicillin-resistantS. aureus(MRSA).

CrIII as an alternative to RuII in metallo-supramolecular chemistry

Semi-labile [Cr(tpy)(CF₃SO₃)₃] precursors can be exploited for building rod-like dinuclear dyads, in which paramagnetic and luminescent trivalent Cr^III replace diamagnetic Ru^II for unravelling intermetallic communication in supramolecular architectures.

mer and fac isomerism in tris chelate diimine metal complexes

In this perspective, we highlight the issue of meridional (mer) and facial (fac) orientation of asymmetrical diimines in tris-chelate transition metal complexes. Diimine ligands have long been the workhorse of coordination chemistry, and whilst there are now good strategies to isolate materials where the inherent metal centered chirality is under almost complete control, and systematic methodologies to isolate heteroleptic complexes, the conceptually simple geometrical isomerism has not been widely investigated. In systems where the two donor atoms are significantly different in terms of the σ-donor and π-accepting ability, the fac isomer is likely to be the thermodynamic product. For the diimine complexes with two trigonal planar nitrogen atoms there is much more subtlety to the system, and external factors such as the solvent, lattice packing and the various steric considerations play a delicate role in determining the observed and isolable product. In this article we discuss the possibilities to control the isomeric ratio in labile systems, consider the opportunities to separate inert complexes and discuss the observed differences in their spectroscopic properties. Finally we report on the ligand orientation in supramolecular systems where facial coordination leads to simple regular structures such as helicates and tetrahedra, but the ability of the ligand system to adopt a mer orientation enables self-assembled structures of considerable beauty and complexity.

Synthesis, characterisation and antibacterial activity of [(p-cym)RuX(L)]+/2+ (X = Cl, H2O; L = bpmo, bpms) complexes

Simple replacement of Cl⁻ by H₂O in {(p-cym)Ru^II(L)X]ⁿ⁺ (X = Cl or H₂O) complexes enhances antibacterial activity significantly.

Thermodynamic N-donor trans influence in labile pseudo-octahedral zinc complexes: a delusion?

While the forces responsible for the chelate effect are well-established in coordination chemistry, the origin and implementation of the related thermodynamic trans influence remains debatable. This work illustrates a simple approach for quantifying this effect in labile pseudo-octahedral [Zn(Lk)3](2+) complexes lacking stereochemical preferences (Lk = L1–L4 are unsymmetrical didentate α,α′-diimine ligands). In line with statistics, the triply degenerated meridional isomers mer-[Zn(Lk)3](2+) are stabilized by 0.8 ≤ ΔGexch(mer→fac) ≤ 4.2 kJ/mol over their nondegenerated facial analogues fac-[Zn(Lk)3](2+) and therefore display no apparent trans influence at room temperature. However, the dissection of the free energy terms into opposite enthalpic (favoring the facial isomers) and entropic (favoring the meridional isomers) contributions reveals a trans influence assigned to solvation processes occurring in polar solvents. Altogether, the thermodynamic trans influence operating in [Zn(α,α′-diimine)3](2+) complexes is 1–2 orders of magnitude smaller than the chelate effect. A weak templating effect provided by a noncovalent lanthanide tripod is thus large enough to produce the wanted facial isomer at room temperature.

Anticancer Activity of Self-Assembled Molecular Rectangles via Arene-Ruthenium Acceptors and a New Unsymmetrical Amide Ligand

Two new and large molecular rectangles 4 and 5 were synthesized from two different arene-ruthenium [Ru(2)(μ-η(4)-C(2)O(4))(MeOH)(2)(η(6)-p-Pr(i)C(6)H(4)Me)(2)][O(3)SCF(3)](2) (2), and [Ru(2) (p-cymene)(2) (donq) (OH(2))(2)] [O(3)SCF(3)](2) (donq = 5,8-dioxydo-1,4-naphthaquinonato) (3) acceptors and a new unsymmetrical N-(4-(pyridin-4-ylethynyl)phenyl) isonicotinamide (1) donor ligand. X-ray crystallography of 4 confirmed a molecular rectangle. The (1)H NMR spectra of both rectangles 4 and 5 showed a mixture of two structural, head-to-tail (HTL) and head-to-head (HTH) type, isomers in a 1:1 ratio. The cytotoxicities of both rectangles have been established against Colo320 (colorectal cancer), A549 (lung cancer), MCF-7(breast cancer) and H1299 (lung cancer) human cancer cell lines. The cytotoxicity of rectangle 5 was found to be considerably stronger against all cancer cell lines than that of the reference drug cisplatin.