Vivian Wing-Wah Yam

Luminescent polynuclear d10 metal complexes

A number of polynuclear d10 transition metal complexes have been found to exhibit interesting luminescence properties. The photoluminescence properties of polynuclear d10 metal complexes are highly diversified. In the presence of a wide range of bridging and ancillary ligands, the excited states of such complexes have been suggested to range from metal-to-ligand charge-transfer, ligand-to-metal charge-transfer, metal-centred to ligand-centred in nature. Recent work on the photophysical and photochemical properties, as well as the applications of this class of luminescent polynuclear d10 metal complexes will be described in this review article.

Highlights on the recent advances in gold chemistry—a photophysical perspective

The presence of inter- and/or intra-molecular aurophilic interactions among the closed-shell gold(I) centres in various systems has been studied from various aspects, including synthetic, spectroscopic and theoretical approaches. The employment of different ligands can impose a significant influence on these factors and give rise to new complexes with interesting structural and photophysical properties. In this tutorial review, a number of recent examples are selected to illustrate the fascinating properties and chemistry, as well as versatility of gold(I) in these aspects and their potential applications to newcomers in this field. An emerging class of luminescent gold(III) complexes is also described.

Recent advances in utilization of transition metal complexes and lanthanides as diagnostic tools

Abstract Based on the widely diverse coordination environment of transition metal complexes and lanthanides, and variation in the identities of coordinating ligands, synthesis of such complexes with desired molecular geometry can be realized. These compounds often possess remarkable and unique spectroscopic, photophysical and electrochemical properties which may be exploited in sensory and diagnostic applications. In this article, recent advances in the development and utilization of transition metal complexes and lanthanides as ion, molecular and other chemical sensors, nucleic acid probes, and other detection tools in related bioassays will be reviewed.

Design of luminescent polynuclear copper(I) and silver(I) complexes with chalcogenides and acetylides as the bridging ligands

Abstract A number of chalcogenido and alkynyl clusters of copper(I) and silver(I) with various nuclearities have been synthesized and characterized. All these clusters have been found to possess rich photophysical and photochemical properties. The phosphorescent states of the complexes have been shown to undergo facile photo-induced oxidative electron-transfer quenching reactions with a series of pyridinium acceptors, indicative of their highly reducing nature in the excited states. The lowest lying excited states of the clusters have been assigned to be an admixture of ligand-to-metal charge-transfer (LMCT) and metal-centered (d-s) transitions, which have also been supported by Fenske-Hall and ab initio molecular orbital calculations. The excited state properties of these cluster have also been probed by nanosecond laser flash photolysis studies.

Luminescent polynuclear metal acetylides

Abstract The photophysical and photochemical studies of polynuclear copper(I), silver(I), gold(I), rhenium(I) and platinum(II) acetylide complexes are reviewed. Based on the highly flexible bonding modes of the acetylides and the various coordination geometry of these metal centres, a number of polynuclear copper(I), silver(I), gold(I), rhenium(I) and platinum(II) acetylide complexes with very different molecular structures have been synthesized and characterized. These organometallic complexes also exhibit rich and remarkable photophysical and photochemical properties which are unique to the presence of the acetylide ligand. The fundamental understanding on the photophysical and photochemical properties of these luminescent organometallic complexes would lead to the production of novel luminescent materials and represent model systems in the development of light-emitting diodes, new materials with non-linear optical properties and liquid crystalline properties. In this review article, particular attention is focused on the electronic absorption spectroscopy, photoluminescence behaviour, excited-state assignments and photochemical properties of this class of luminescent acetylide complexes.

Impact of marine fish farming on water quality and bottom sediment: A case study in the sub-tropical environment

Abstract Field studies were carried out to determine and compare the impact of marine fish farming activities on the water quality and bottom sediment at four fish culture sites with different hydrographic and culture conditions in a sub-tropical environment where trash fish is used as feed. The major impact identified was on the sea bottom, resulting in the development of reducing and anoxic sediments, high sediment oxygen demand, production of hydrogen sulphide and elimination/decrease in benthos. The impact on water quality was less conspicuous. A decrease in dissolved oxygen was observed at all sites while increases in ammonia, inorganic P, nitrate and nitrite were observed only at sites with poor tidal flushing and high stocking density. However, no significant changes in total suspended solids, light extinction coefficient, chlorophyll a, phaeopigment and E. coli were found near the fish rafts at any sites. Environmental impacts vary considerably between sites, and were significantly reduced at sites with good water circulation and low stocking density. Despite the high organic and nutrient loadings generated by marine fish farming activities, the impacts on water quality and sediments at all sites were localised and did not appear to extend beyond a distance of 1–1.5 km from the fish rafts. Results of the present study also do not support the suggestion that marine fish farming activities have caused eutrophication on a large scale.

Luminescent metallogels of platinum(II) terpyridyl complexes: interplay of metal⋯metal, π–π and hydrophobic–hydrophobic interactions on gel formation

A series of platinum(II) terpyridyl complexes has been demonstrated to show gelation properties driven by Pt...Pt and pi-pi interactions in addition to hydrophobic-hydrophobic interactions; counter-anions have been found to affect strongly the colour of the metallogel.

Supramolecular self-assembly of amphiphilic anionic platinum(II) complexes: A correlation between spectroscopic and morphological properties

A new class of amphiphilic anionic platinum(II) bzimpy complexes has been demonstrated to show aggregation in water through Pt···Pt and π-π stacking interactions. An interesting aggregation-partial deaggregation-aggregation process and a morphological transformation from vesicles to nanofibers have been demonstrated. These changes can be systematically controlled by the variation of solvent composition and could readily be probed by UV-vis absorption, emission, NMR, transmission electron microscopy, and even with our naked eyes.

Transition metal complexes with photochromic ligands - Photosensitization and photoswitchable properties

The development of transition metal complexes with ligands containing different photochromic families has received increasing attention in recent years. Through rational design of the photochromic moieties as ligands, the photochromic properties could be systematically perturbed and varied by relatively simple coordination to different metal centres. In this article, a number of examples, in particular those ligands containing stilbenes, azo compounds, spirooxazines and diarylethenes, are selected to demonstrate the design, perturbation and photosensitization of photochromic moieties with transition metal–ligand chromophores. The photoswitching properties of the transition metal complex functionality are described.

Photochromic Diarylethene-Containing Ionic Liquids and N-Heterocyclic Carbenes

The design and synthesis of a series of photochromic diarylethene-containing Arduengo-type N-heterocyclic carbenes (NHCs) of gold(I), silver(I) and palladium(II) and their imidazolium salt precursors are reported. Reversible photochromic behavior was observed. The open form and the closed form also show different luminescence properties. The electronic and conformational/steric changes associated with the photocyclization and photocycloreversion reactions may open up new opportunities for the discovery of new classes of photochromic ligands and metal-containing materials and catalysts with photoswitchable functions and activities and regio-/enantioselectivities.