Fiat lux!

Photochemistry made the transition from a natural observable to a scientific discipline in the latter half of the 19; th; Century CE. This short article looks at the development of the discipline in its first 100 years with a particular emphasis on the participation of Swiss scientists

Ho Ho Ho! When Water was Diatomic

When he introduced the concept of atomic weights at the beginning of the 19; th; Century CE, John Dalton assumed that water had the formula HO. This assumption resulted in a half century of confusion - partly because on a scale of H = 1, he defined the atomic weights O = 8 and C = 6, and partly because elements that could exhibit variable valency appeared to possess different atomic (or rather equivalent) weights. The correction of the formula of water, together with the recognition of the diatomic nature of the gases hydrogen and oxygen, were formalized following the Karlsruhe congress of 1861 and allowed the establishment of the 'modern' and consistent atomic weights

Packing Motifs in [M(bpy)₂X₂] Coordination Compounds (bpy = 2,2′-bipyridine; X = F, Cl, Br, I)

Packing motifs within structurally characterized cis-[M(bpy)2X2] (M = any metal, bpy = 2,20-bipyridine, X = F, Cl, Br, I) coordination compounds have been investigated using data from the Cambridge Structural Database. Compounds fall into two classes: non-solvated cis-[M(bpy)2X2] moieties and those with additional lattice molecules (solvent or other molecules). A recurring packing motif is a dimeric unit involving intermolecular face-to-face -stacking of bpy ligands and CHbpy...X contacts, although in several cases, slippage of the stacked bpy units reduces the effectiveness of the face-to-face interaction leaving the CHbpy...X contacts as the dominant crystal-packing interaction. The prevalence of the dimeric unit versus the assembly of 1D-chains in the solid state is described

When Stereochemistry Raised Its Ugly Head in Coordination Chemistry-An Appreciation of Howard Flack

Chiral compounds have played an important role in the development of coordination chemistry. Unlike organic chemistry, where mechanistic rules allowed the establishment of absolute configurations for numerous compounds once a single absolute determination had been made, coordination compounds are more complex. This article discusses the development of crystallographic methods and the interplay with coordination chemistry. Most importantly, the development of the Flack parameter is identified as providing a routine method for determining the absolute configuration of coordination compounds

Isomers of Terpyridine as Ligands inCoordination Polymers and Networks Containing Zinc(II) and Cadmium(II)

The use of divergent 4,2′:6′,4″- and 3,2′:6′,3″-terpyridine ligands as linkers and/or nodes in extended coordination assemblies has gained in popularity over the last decade. However, there is also a range of coordination polymers which feature 2,2′:6′,2″-terpyridine metal-binding domains. Of the remaining 45 isomers of terpyridine, few have been utilized in extended coordination arrays. Here, we provide an overview of coordination polymers and networks containing isomers of terpyridine and either zinc(II) and cadmium(II). Although the motivation for investigations of many of these systems is their luminescent behavior, we have chosen to focus mainly on structural details, and we assess to what extent assemblies are reproducible. We also consider cases where there is structural evidence for competitive product formation. A point that emerges is the lack of systematic investigation

"Simple" oligopyridine complexes - sources of unexpected structural diversity

The simple formulae often presented for main-group metal complexes of oligopyridines (typically 2,2-bipyridine, 1,10-phenanthroline and 2,2':6',2"-terpyridine) hide a wide variety of polymeric solid-state structures. We present an overview of these structures and reveal a plethora of 1D chains, including ladder assemblies, and 2D networks. In most assemblies, the polymeric backbone or network is defined by the metal atoms and bridging ligands other than oligopyridines. The heterocyclic ligands typically feature as peripheral decorations, often engaging in face-to-face supramolecular p-stacking interactions which define the assembly of the crystal. In 1D coordination polymers, three types of decoration predominate which we have defined at Type 1 (all the oligopyridines on the same side and p-stacked, Type 2 (alternating arrangement of oligopyridines) and Type 3 (a pairwise alternating structure

Embracing [XY3]m–and [XY4]m– Anions in Salts of [M(bpy)3]q+

[M(bpy)3]q+ cations (bpy = 2,2′-bipyridine) are archetypical coordination entities containing chelating bidentate N,N′-donor ligands. Each propeller-shaped cation is chiral, existing as a Δ or Λ enantiomer. The supramolecular chemistry of [M(bpy)3]q+ cations in the crystal is dominated by cation- anion interactions and, to a lesser extent, weaker non-covalent interactions. Analysis of the data for [M(bpy)3]q+ salts in the Cambridge Structural Database (CSD) reveals a ubiquitous motif in which homochiral sheets of cations generate cavities for the accommodation of anions. A series of related and common motifs in the solid-state structures of [M(bpy)3]q+ salts has been identified. One of the commonest motifs comprises a hexagon of six cations with anions either in the center or lying above and/or below the centroid

Supramolecular Approaches to Advanced Materials

Synthetic strategies based upon metal-directed self-assembly or upon the post-functionalization of dendritic and related systems have been used for the preparation of new nanodimensioned metal-containing species. These and related studies on the design of metallomesogens are reported in this paper

Chemical bonding: the journey from miniature hooks to density functional theory

Our modern understanding of chemistry is predicated upon bonding interactions between atoms and ions resulting in the assembly of all of the forms of matter that we encounter in our daily life. It was not always so. This review article traces the development of our understanding of bonding from prehistory, through the debates in the 19th century C.E. bearing on valence, to modern quantum chemical models and beyon

Before Radicals Were Free-The Radical Particulier of de Morveau

Today, we universally understand radicals to be chemical species with an unpaired electron. It was not always so, and this article traces the evolution of the term radical and in this journey, monitors the development of some of the great theories of organic chemistr