A geometrical analysis has been performed on π–π stacking in metal complexes with aromatic nitrogen-containing ligands based on a Cambridge Structural Database search and on X-ray data of examples in the recent literature. It is evident that a face-to-face π–π alignment where most of the ring-plane area overlaps is a rare phenomenon. The usual π interaction is an offset or slipped stacking, i.e. the rings are parallel displaced. The ring normal and the vector between the ring centroids form an angle of about 20° up to centroid–centroid distances of 3.8 A. Such a parallel-displaced structure also has a contribution from π–σ attraction, the more so with increasing offset. Only a limited number of structures with a near to perfect facial alignment exists. The term π–π stacking is occasionally used even when there is no substantial overlap of the π-ring planes. There is a number of metal–ligand complexes where only the edges of the rings interact in what would be better described a C–H⋯π attraction.

A critical account on π–π stacking in metal complexes with aromatic nitrogen-containing ligands

A fundamental understanding of the luminescence of Au–thiolate nanoclusters (NCs), such as the origin of emission and the size effect in luminescence, is pivotal to the development of efficient synthesis routes for highly luminescent Au NCs. This paper reports an interesting finding of Au(I)–thiolate complexes: strong luminescence emission by the mechanism of aggregation-induced emission (AIE). The AIE property of the complexes was then used to develop a simple one-pot synthesis of highly luminescent Au–thiolate NCs with a quantum yield of ∼15%. Our key strategy was to induce the controlled aggregation of Au(I)–thiolate complexes on in situ generated Au(0) cores to form Au(0)@Au(I)–thiolate core–shell NCs where strong luminescence was generated by the AIE of Au(I)–thiolate complexes on the NC surface. We were able to extend the synthetic strategy to other thiolate ligands with added functionalities (in the form of custom-designed peptides). The discovery (e.g., identifying the source of emission and the s...

From Aggregation-Induced Emission of Au(I)–Thiolate Complexes to Ultrabright Au(0)@Au(I)–Thiolate Core–Shell Nanoclusters

Conversion constants for redox potentials measured versus different reference electrodes in acetonitrile solutions at 25°C

Light-Emitting Self-Assembled Materials Based on d(8) and d(10) Transition Metal Complexes.

Coordination complexes exhibiting room-temperature phosphorescence: Evaluation of their suitability as triplet emitters in organic light emitting diodes

The electronic absorption spectrum of [Au2(dppm)2]2+[dppm = bis(diphenylphosphino)methane] in acetonitrile exhibits an absorption band at 290 nm, attributable to a pσâ†�dσ* transition. A much weaker band in the region 300–370 nm is assigned to a pσâ†�dδ* transition. Excitation of [Au2(dppm)2]2+ in degassed acetonitrile at 310–390 nm at room temperature results in phosphorescence centred at 575 nm, which is most likely to be derived from the 3B1u[(dδ*)1(pσ)1] state. The phosphorescence of [Au2(dppm)2]2+* is found to be quenched by a number of electron acceptors and donors, as well as energy-transfer acceptors. The powerful reducing nature of [Au2(dppm)2]2+* is revealed by its excited-state redox potential E°[Au2(dppm)23+/2+*] of –1.6(1) V vs. a saturated sodium chloride calomel electrode (s.s.c.e.) which was determined through studies of quenching by a series of pyridinium acceptors.

Spectroscopy and redox properties of the luminescent excited state of [Au2(dppm)2]2+ (dppm = Ph2PCH2PPh2)

Solid-state emission of dicyanoplatinum(II) and -palladium(II) complexes of substituted 2,2'-bipyridines and 1,10-phenanthroline and x-ray crystal structures of isomorphous M(bpy)(CN)2 (bpy = 2,2'-bipyridine; M = Pt, Pd)

The cis-[RuII(L)2(OH2)2]2+ complexes (L = substituted 2,2′-bipyridines or 1,10-phenanthrolines) catalyse oxidation of saturated hydrocarbons to alcohols and ketones by t-butylhydroperoxide; the low values of kinetic isotope effect (kH/kD= 35 for cyclohexane) and tertiary of secondary C–H bond relative reactivities (ktert/ksecca 65 for adamantane) are in a range expected for hydrogen atom abstraction by radical species

Ruthenium catalysed oxidation of alkanes with alkylhydroperoxides

Synthese et structure moleculaire de [Cr(bpb)N] avec H 2 bpb=bis(pyridinecarboxamido-2)-1,2 benzene

Synthesis and Molecular Structure of a Nitridochromium(V) Complex Stabilized with Dianionic Organic Amide Ligand

The Pt(5,5′-Me2bpy)(CN)2 complex (5,5′-Me2bpy = 5,5′-dimethyl-2,2′-bipyridine) displays intense photoluminescence in fluid solution (emission maximum, 502 nm; τ0, 6.3 µs) at room temperature; the excited ππ* triplet of Pt(5,5′-Me2bpy)(CN)2 is a powerful one-electron oxidant (E∘, ∼1.0V) and reductant (E∘≤–1.5V vs. AgNO3/Ag) which undergoes oxidative and reductive quenching with inorganic and organic substrates.

Chung-Kwong Poon

Papers

Spectroscopy and redox properties of the luminescent excited state of [Au2(dppm)2]2+ (dppm = Ph2PCH2PPh2)

Solid-state emission of dicyanoplatinum(II) and -palladium(II) complexes of substituted 2,2'-bipyridines and 1,10-phenanthroline and x-ray crystal structures of isomorphous M(bpy)(CN)2 (bpy = 2,2'-bipyridine; M = Pt, Pd)

Ruthenium catalysed oxidation of alkanes with alkylhydroperoxides

Synthesis and Molecular Structure of a Nitridochromium(V) Complex Stabilized with Dianionic Organic Amide Ligand

Novel luminescent platinum(II) complexes. Photophysics and photochemistry of Pt(5,5′-Me2bpy)(CN)2(5,5′-Me2bpy=5,5′-dimethyl-2,2′-bipyridine)