A new luminescent Ru(terpy) complex incorporating a 1,2,4-triazole based σ-donor ligand

The mononuclear compound [Ru(terpy)L], where H2L is 2,6-bis(1,2,4-triazol-3-yl)pyridine, shows an emission lifetime of 65 ns, about 300 times longer than that observed for the parent [Ru(terpy)3]2+ complex

Ruthenium (II) complexes with terpyridine derivatives: what is the lifetime of the excited state dependent on?

The synthesis, spectroscopic and electrochemical characterisation of ruthenium (II) polypyridyl mononuclear complexes containing 1,2,4-tnazole and tetrazole moiety are described. Chapter one is an introduction relating to the work described in the thesis. The methods of characterisation, which are described in chapter two, include High Performance Liquid Chromatography, 'H-NMR, UV/Visible spectroscopy, fluorimetry, electrochemistry, spectroelectrochemistry, mass spectrometry, and lifetime emission measurements. Chapter three describes the synthesis of the new set of ligands and their mononuclear Ruthenium (II) complexes. Chapter four contains an extensive characterisation of Ru(II)(bpy)2 moiety complexes containing a 5-(2-pyridyl)-l,2,4-triazole ligand, (Apy), or a 5-(2-pyridyl) tetrazole ligand, ([ ipy), and their comparison with the archetype Ru(bpy)s2+. The examination of the acid-base chemistry of the complexes by UV/Visible spectroscopy revealed important information about the location of the excited state. Chapter five explores the spectroscopic, photophysical and electrochemical properties of the new [Ru(tpy)fApyA)] complexes, where (ApyA)2' is the 2,6 di-(l,2,4- triaz-3-yl)-pyridine ligand. The new species was exhaustively studied especially because it revealed to be one of the few example, available in literature, of emitting Ru(H) terpiridine complexes, with a lifetime of the excited state in the order of 100 nanoseconds. Chapter six describes the synthesis of complexes containing (ApyA)2' and terpyridine derivatives or vice-versa terpyridine and (ApyA)2" derivative ligands. One of them will be used as a photsensitiser in a photovoltaic cell. Attachment of the [Ru(II)(tctpy)(ApyA)] complex to nanocrystalline TiC>2 films indicates incident photonto- current efficiency (IPCE) of greater than 60%. Chapter seven exptores the use of a new 2,6 di-(tetraz-5-yl)-pyndine ligand, (Upyl ]) ", and the spectroscopic, photophysical and electrochemical properties of its Ru(II) complexes. Chapter eight is an attempt to rationalise the collected data of the Ru(tpy) moiety. The change of the energy levels in relation to the different ligands is analysed. The correlations between spectroscopic, photophysical and electrochemical data of the new complexes and the existent ones created an extensive knowledge of the tridentate Ru(H) complexes, that increases their availability as a photosensitive building block for a supramolecular system. Some suggestions for future work are also considered in the final Chapter. Finally two appendices are included in this thesis. The first is a literature survey which synopsises the last ten years scientific papers, on the Ru-tpy moiety, includmg investigations of their properties, use in analytical research or their use as building blocks in supramolecolar systems. The second appendix refers to the publications, poster presentations and oral presentations made during the course of the research

Luminescent anion recognition: Probing the interaction between dihydrogenphosphate anions and Ru(II) polypyridyl complexes in organic and aqueous media.

A photophysical study of the interaction between dihydrogen phosphate anions and a series of ruthenium polypyridyl complexes containing anion receptor 4,4'-bis[(2-methoxyethyl)carbamoyl]-2,2'-bipyridine (L1) is reported. The complexes investigated are of the type [Ru(L)[2](L1)]X[2] and [Ru(L1)[3]]X[2], where L is 2,2'-bipyridyl or 1,10-phenanthroline and X is chloride or PF[6]-. The emission properties of the compounds are studied as a function of the anion concentrations using emission lifetime and steady-state measurements. For the mixed ligand complexes the emission intensity and lifetime increases upon the addition of 2.5 molar equivalents of H[2]PO[4]-, further additions do not result in further increases. For [Ru(L1)[3]]X[2] the emission increases upon addition of the first 2.5 equivalents of dihydrogen phosphate, however, further increases lead to a decrease in both emission intensity and lifetime. The effect of the addition of trace amounts of water is also examined

Synthesis and characterisation of ruthenium complexes containing a pendent catechol ring

A series of [Ru(bipy)₂L]⁺ and [Ru(phen)₂L]⁺ complexes where L is 2-[5-(3,4-dimethoxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine (HL1) and 4-(5-pyridin-2-yl-4H-1,2,4-triazol-3-yl)benzene-1,2-diol (HL2) are reported. The compounds obtained have been characterised using X-ray crystallography, NMR, UV/Vis and emission spectroscopies. Partial deuteriation is used to determine the nature of the emitting state and to simplify the NMR spectra. The acid-base properties of the compounds are also investigated. The electronic structures of [Ru(bipy)₂L1]⁺ and Ru(bipy)₂HL1]²⁺ are examined using ZINDO. Electro and spectroelectrochemical studies on [Ru(bipy)₂(L2)]⁺ suggest that proton transfer between the catechol and triazole moieties on L2 takes place upon oxidation of the L2 ligand

A new luminescent Ru(terpy) complex incorporating a 1,2,4-triazole based σ-donor ligand

The mononuclear compound [Ru(terpy)L], where H2L is 2,6-bis(1,2,4-triazol-3-yl)pyridine, shows an emission lifetime of 65 ns, about 300 times longer than that observed for the parent [Ru(terpy)3]2+ complex

Complexed Nitrogen Heterosuperbenzene: The Coordinating Properties of a Remarkable Ligand

Tetra-peri-(tert-butyl-benzo)-di-peri-(pyrimidino)-coronene 1, the parent compound of the nitrogen heterosuperbenzene family N-HSB, is employed as a novel monotopic ligand in the formation of [Pd(η3-C3H5)(1)]PF6 2 and [Ru(bpy)2(1)](PF6)2 (where bpy = 2,2'-bipyridine 3a and d8-2,2'-bipyridine 3b). These N-coordinated complexes are fully characterized by 1H NMR and IR spectroscopy and ESI-MS. Metal coordination has a profound effect on both the absorption and the emission properties of 1. Pd(II) coordination causes a red-shift in the low-energy absorptions, a decrease in the intensity of the n-π* absorptions, and a quenching of the emission. Ru(II) coordination causes absorption throughout the visible region and creates two new complexes that join an elite group of compounds known as “black” absorbers. 3a and 3b possess two discernible 1MLCT bands. The one of exceptionally low energy (λmax = 615 nm) has an associated 3MLCT emission (λmax = 880 nm) due to the unprecedented electron delocalization and acceptor properties of the rigid aromatic N-HSB 1. Both Ru(II) complexes are near-IR emitters with unusually protracted emission lifetimes of 320 ns at 77 K. They are photochemically inert, and their electrochemical properties are consistent with the presence of a low-lying π* orbital on 1. The first two reversible reductions (E1/2 (CH3CN), -0.54 V, -1.01 V vs SCE) are due to the stepwise reduction of 1 and are anodically shifted as compared to [Ru(bpy)3]2+. Temperature- and concentration-dependent NMR studies on 2 and 3a suggest extensive aggregation is occurring in solution.

The Influnce of Defects in the Electrical Characteristics of Mercury Drop-Junctions: A Study of Self Assembled Monolayers (SAMs) of n-Alkanethilate on Rough and Smooth Silver

This paper compares the structural and electrical characteristics of self-assembled monolayers (SAMs) of n-alkanethiolates, SCn (n = 10, 12, 14), on two types of silver substrates: one used as-deposited (AS-DEP) by an electron-beam evaporator, and one prepared using the method of template-stripping. Atomic force microscopy showed that the template-stripped (TS) silver surfaces were smoother and had larger grains than the AS-DEP surfaces, and reflectance-absorbance infrared spectroscopy showed that SAMs formed on TS substrates were more crystalline than SAMs formed on AS-DEP substrates. The range of current densities, J (A/cm2), measured through mercury-drop junctions incorporating a given SAM on AS-DEP silver was, on average, several orders of magnitude larger than the range of J measured through the same SAM on TS silver, and the AS-DEP junctions failed, on average, 3.5 times more often within five current density-voltage (J-V) scans than did TS junctions (depending on the length of the alkyl chains of the molecules in the SAM). The apparent log-normal distribution of J through the TS junctions suggests that, in these cases, it is the variability in the effective thickness of the insulating layer (the distance the electron travels between electrodes) that results in the uncertainty in J. The parameter describing the decay of current density with the thickness of the insulating layer, , was either 0.57 Å-1 at V = +0.5 V (calculated using the log-mean of the distribution of values of J) or 0.64 Å-1 (calculated using the peak of the distribution of values of J) for the TS junctions; the latter is probably the more accurate. The mechanisms of failure of the junctions, and the degree and sources of uncertainty in current density, are discussed with respect to a variety of defects that occur within Hg-drop junctions incorporating SAMs on silver