There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies

Nanoparticle-supported and magnetically recoverable nickel catalyst: a robust and economic hydrogenation and transfer hydrogenation protocol

The theory and practice of hyperpolarization in magnetic resonance using parahydrogen

Molecular systems encompassing more than one photochromic entity can be used to build highly functional materials, thanks to their potential multi-addressability and/or multi-response properties. Over the last decade, the synthesis and spectroscopic and kinetic characterisation as well as the modeling of a wide range of multiphotochromes have been achieved in a field that is emerging as a distinct branch of photochemistry. In this review, we provide an overview of the available multiphotochromic compounds which use a variety of photoactive building blocks, e.g., diarylethene, azobenzene, spiropyran, naphthopyran or fulgimide derivatives. Their efficiency in terms of multi-responsiveness is discussed and several strategies to circumvent the most common limitation (i.e., the loss of photochromism of one part) are described.

Multiphotochromic molecular systems

Negatively photochromic organic compounds: Exploring the dark side

A new synthetic route to donor–acceptor porphyrins

The complexes [Pd(bcope)(OTf)2] (1a), where bcope is (C8H14)PCH2−CH2P(C8H14), and [Pd(tbucope)(OTf)2] (1b), where tbucope is (C8H14)PC6H4CH2P(tBu)2, catalyze the conversion of diphenylacetylene to cis- and trans-stilbene and 1,2-diphenylethane. When this reaction was studied with para-hydrogen, the characterization of [Pd(bcope)(CHPhCH2Ph)](OTf) (2a) and [Pd(tbucope)(CHPhCH2Ph)](OTf) (2b) was achieved. Magnetization transfer from the α-H of the CHPhCH2Ph ligands in these species proceeds into trans-stilbene. This process has a rate constant of 0.53 s-1 at 300 K in methanol-d4 for 2a, where ΔH⧧ = 42 ± 9 kJ mol-1 and ΔS⧧ = −107 ± 31 J mol-1 K-1, but in CD2Cl2 the corresponding rate constant is 0.18 s-1, with ΔH⧧ = 79 ± 7 kJ mol-1 and ΔS⧧ = 5 ± 24 J mol-1 K-1. The analogous process for 2b was too fast to monitor in methanol, but in CD2Cl2 the rate constant for trans-stilbene formation is 1.04 s-1 at 300 K, with ΔH⧧ = 94 ± 6 kJ mol-1 and ΔS⧧ = 69 ± 22 J mol-1 K-1. Magnetization transfer from one of the two in...

Stuart Aiken

Papers

Negatively photochromic organic compounds: Exploring the dark side

A new synthetic route to donor–acceptor porphyrins

A para-hydrogen investigation of palladium-catalyzed alkyne hydrogenation.

The CA.M lattice revisited. Gel formation from a linear bis-isocyanuric acid and 2-amino-4,6-bis-(4-tert-butylphenylamino)-1,3,5-triazine

Metallated porphyrins containing lead(II), copper(II) or zinc(II)