A series of binuclear ruthenium and osmium complexes [(bipy) (5) and [(bipy) 2 Os(bpbt)Os(bipy) 2 ] 2+ (6) {bipy = 2,2¢-bipyridyl; qpy = 2,2¢:5¢,5¢¢:2¢¢,2¢¢¢-quaterpyridyl; pytr-bipy = 3-(2,2¢-bipyrid-6-yl)-5-(pyrid-2-yl)-1,2,4-triazolato, and bpbt = 5,5¢-bis-(pyrid-2¢¢-yl)-3,3¢-bis-1,2,4-triazolato} are reported. Analysis of the electrochemical data focuses on structural factors and on determining the extent of electronic communication between the metal centres in the mixed valence oxidation state. Intervalence charge transfer (IT) bands could be identified in the spectra of the complexes 4 and 6 only. Analysis of their spectroelectrochemical data leads to the conclusion that the IT is superexchange mediated through the HOMO of the bridging ligand. IntroductionMetal complexes based on polypyridyl ligands constitute versatile components for the construction of multifunctional supramolecular systems in molecular photonics and molecular electronics, 1 sensors, 2 photocatalysis, 3 solar energy 5 conversion, 4 artificial photosynthesis, 5 non-linear optics, 6 and electrochemoluminescence 7 amongst others. 8, 9 The myriad of applications are founded on the well defined chemistry of these compounds and take advantage of the versatile photophysical, 10 photochemical 11 and electrochemical 12 properties that are associ-10 ated with the metal-to-ligand charge-transfer (MLCT) excitation in these metal complexes. 13 Amongst the many multinuclear polypyridyl complexes reported, 14 an interesting subclass is represented by those binuclear systems that display additional spectroelectrochemical features 15 due to the electronic interaction between the two metal centres in the mixed valence redox state(s). 15,16 "Communication" between metal centres where direct overlap of atomic orbitals is not possible is achieved when the bridging ligand (BL) has a system of polarisable electrons that are capable of mediating 20 the redistribution of the electronic charge between the two metal centres. Sciences, Dublin City University, Dublin 9, Analysis of these absorption bands 25 can provide detailed information as to the nature and extent of the interaction between the metals centres. 30 Recently, we reported the synthesis and characterisation of a series of homo-and hetero-binuclear ruthenium(II) and osmium(II) complexes of the general formula [M 1 (bipy) 2 -BL-M 2 (bipy) 2 ], where M = Ru or Os, bipy is 2,2¢-bipyridyl (bipy), and BL the bridging ligands 2,2¢:5¢,5¢¢:2¢¢,2¢¢¢-quaterpyridyl (qpy), 3-(2,2¢-35 bipyrid-6-yl)-5-(pyrid-2-yl)-1,2,4-triazolato (pytr-bipy), and 5,5¢-bis-(pyrid-2¢¢-yl)-3,3¢-bis-1,2,4-triazolato (bpbt). 26 In the present contribution, we describe in detail the electrochemical and spectroelectrochemical properties of these compounds. The goal of the present study is to evaluate the extent 40 of electronic communication between the two metal centres as a function of the electronic properties of the bridging ligand and the positioning of the two metal centres. In particular, attention is directed towards the hom...

Synthesis of asymmetric supramolecular compounds using a Ni(0) catalysed homo-coupling approach Cassidy, Lynda; Horn, Sabine; Cleary, Laura; Halpin, Yvonne; Browne, Wesley; Vos, Johannes G. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The synthesis and characterisation of a series of dinuclear ruthenium and osmium polypyridyl metal complexes based on the bridging ligands [5-(5¢-bipyridin-2¢,2¢¢-yl)-3-(pyridin-2-yl)]-1,2,4-triazole (Hpytr-bipy), 2,2¢-bis(pyridin-2¢¢yl)-5,5¢-bis(pyridin-3¢¢-yl) (bipy-bipy) and 5,5¢-bis(pyridin-2¢¢-yl)-3,3¢-bis(1,2,4-triazole) (Hpytr-Hpytr) are reported. The dinuclear complexes have been synthesised via a Ni(0) catalysed cross-coupling reaction from brominated precursors. With this approach a mixture of three products is obtained, which are separated by chromatographic methods. The compounds obtained are characterised by elemental analysis, 1 H NMR, absorption and emission spectroscopy. The synthetic approach developed offers a new route to asymmetric multinuclear supramolecular structures that is complimentary to the complexes as ligands/complexes as metal approaches.

We present a density functional theory (DFT) study of an osmium polypyridyl complex adsorbed on Au(111). The osmium polypyridyl complex [Os(bpy)2(P0P)Cl]n+ [bpy is 2,2'-bipyridine, P0P is 4,4'-bipyridine, n = 1 for osmium(II), and n = 2 for osmium(III)] is bound to the surface through the free nitrogen of the P0P ligand. The calculations illuminate electronic properties relevant to recent comprehensive characterization of this class of osmium complexes by electrochemistry and electrochemical scanning tunneling microscopy. The optimized structures for the compounds are in close agreement with crystallographic structures reported in the literature. Oxidation of the complex has little effect on these structural features, but there is a substantial reordering of the electronic energy levels with corresponding changes in the electron density. Significantly, the highest occupied molecular orbital shifts from the metal center to the P0P ligand. The surface is modeled by a cluster of 28 gold atoms and gives a good description of the effect of immobilization on the electronic properties of the complexes. The results show that the coupling between the immobilized complex and the gold surface involves electronic polarization at the adsorbate/substrate interface rather than the formation of a covalent bond. However, the cluster is too small to fully represent bulk gold with the result that, contrary to what is experimentally observed, the DFT calculation predicts that the gold surface is more easily oxidized than the osmium(II) complex.