Alexandre N. Sobolev

Poly(ethyleneglycol)(PEG): a versatile reaction medium in gaining access to 4′-(pyridyl)-terpyridines

A new paradigm for the synthesis of 4′-pyridyl terpyridines using poly(ethyleneglycol) (PEG) as a benign reaction medium is described, with the compounds readily accessible in high purity in ca. 4 hours using a ‘one pot’ procedure. This method requires no product purification and affords the desired compounds in reasonable yield without the formation of unwanted side products.

Engineering nanorafts of calixarene polyphosphonates

The water-soluble calix[4]arene bearing p-substituted phosphonic acid groups is accessible in five steps in overall 62 % yield, with the hydrogen-bonding prowess of the acidic groups dominating its self-assembly processes. These include the formation of 3.0(3) nm and 20(2) nm nanorafts of the calixarene in water using spinning disc processing, stabilized by acetonitrile, and nanorafts in the gas phase (<or=20 molecules). The 20(2) nm particles transform into 3.0(3) nm particles prior to crystallization into a compact bilayer, whereas crystallization in the presence of large organic molecules gives an expanded bilayer interposed by layers of water molecules.

Lanthanide-induced helical arrays of [{Co(III) sepulchrate}∩{p-sulfonatocalix[4]arene}] supermolecules

In the presence of lanthanide ions, a Co(III) sepulchrate cation [Co(diHOsar)]3+ and sodium p-sulfonatocalix[4]arene form a 1:1 host-guest complex which is self-assembled into a zeolite-like lattice network comprised of parallel, single stranded helices.

The Significance of Ionic Bonding in Sulfur Dioxide: Bond Orders from X‐ray Diffraction Data

A novel refinement technique for X‐ray diffraction data has been employed to derive S-O bond orders in sulfur dioxide experimentally. The results show that ionic S-O bonding dominates over hypervalency.

Exploiting phenyl embraces and π-stacking in the assembly of arrays of tetraphenylphosphonium p-sulfonatocalix[4]arene

Phenyl embraces involving tetraphenylphosphonium cations feature in complexes of p-sulfonatocalix[4]arene where a phenyl ring of a cation is included in the cavity of the calixarene. The overall structures are based on pseudo-polymorphic supramolecular arrays and their formation is templated or induced by lanthanide ions.

Self-ordering of metallogrid complexes via directed hydrogen-bonding

Reaction of imidazole aldehydes with dihydrazino derivatives of 2-phenylpyrimidine provides a family of bis(acylhydrazone) ligands which form [2 × 2] metallogrid complexes with transition metal ions including Fe(II), Co(II), Cu(II) and Zn(II). The free ligands show H-bonding interactions, both donor and acceptor, largely involving the imidazole units, while binding of the metal ions occupies all the acceptor sites and leaves only the pyrrolic-NH site as an H-bond donor, although its deprotonation by a strong base can regenerate an acceptor. These H-bonding interactions have been studied by (1)H NMR spectroscopy in solution and in the solid state by means of several crystal structure determinations. The Fe(II) grids appear to be exclusively high-spin species over a wide temperature range in solution. In the solid state various forms of spin-crossover behaviour can be observed between 1.8 and 300 K, which has been rationalised in terms of the varied forms of hydrogen-bonding possible in the crystalline state.

Self-organised nano-arrays of p-phosphonic acid functionalised higher order calixarenes

Water-soluble p-phosphonic acid calix[n]arenes (n = 5, 6 or 8) have been synthesized in five steps in overall 68, 66, 67% yield, respectively, by the recently developed procedure for p-phosphonic acid calix[4]arene. The hydrogen bonding prowess of the phosphonic acids dominates their self assembly into nano-arrays in both solution and the gas phase. In DMSO, nano-arrays of p-phosphonic acid calix[6]arene are stable for over 24 h, with the solvent molecules slowly disrupting the hydrogen bonded network affording solvated monomeric units. In the gas phase, nano-arrays of around 20 calixarene units were observed for the p-phosphonic acid calix[n]arenes using MALDI-TOF-MS, and ESI-MS revealed the presence of heteroleptic nano-arrays for a 1 : 1 mixture of p-phosphonic acid calix[4,5]arenes.

PEG mediated synthesis of amino-functionalised 2,4,6-triarylpyridines

The reaction of p-aminoacetophenone with aryl aldehydes in polyethylene glycol (PEG) in the presence of base, followed by treatment with ammonium acetate, affords 2,4,6-triarylpyridines in good yield as a ‘one pot’ procedure. The intermediate Claisen–Schmidt chalcone condensation products or the Michael addition 1,5-diketone products can be prepared in high yield, depending on the ratio of ketone to aldehyde, prior to treatment with ammonium acetate.

Crystal packing in the 2-R,4-oxo-[1,3-a/b]-naphthodioxanes - Hirshfeld surface analysis and melting point correlation

The crystal structures of an array of 2-R,4-oxo-[1,3-b]-naphthodioxanes (R = H, Me, Et, i-Pr, n-Bu, CCl3, i-propylideneglyceral) have been determined at 100 K, together with a more limited series of the isomeric 2-R,4-oxo-[1,3-a]-naphthodioxanes (R = Et, i-Pr, n-Bu, i-propylideneglyceral), permitting a study of the effects of substituent and ring fusion variation on the crystal packing of neutral molecules that are otherwise essentially planar. We have conducted an analysis of Hirshfeld surfaces (a definition of an outer contact surface of a molecule within a crystal) for all eleven compounds and follow the changes of different properties on these surfaces upon systematic variation of the substituent R. Not only qualitative information by means of fingerprint plots, but also quantitative information by means of melting point correlations are presented. The results show the extent to which C–H⋯O hydrogen bonds and C–H⋯π/π⋯π interactions contribute positively to the lattice energies on the one hand, and H⋯H contacts negatively on the other. The percentage of H⋯H contacts as closest contacts on the Hirshfeld surfaces is a universally applicable measure of the crystal lattice energy and can be used as a reference for the importance of other types of contacts.

Variations on a Cage Theme: Some Complexes of Bicyclic Polyamines as Supramolecular Synthons

Dedication: One of Alan Sargeson’s great abilities was to seek out knowledge on topics of which he was not the master from those people with the expertise. This led occasionally to publications with a ‘cricket team’ of authors but with a rich brew of information, often international. Alan also insisted that all authors were equal since, without any one, the paper would not be what it was. Hence, he endeavoured to pursue the policy, difficult to maintain over a period where an obsession with absurdities such as the order of authors and point-scoring based on meaningless publication indices became so important in the maintenance of research, of listing authors simply in alphabetical order. In describing work begun while he was still with us, we have attempted to adhere to his principles. Analysis of a body of crystallographic information concerning metal(ii) and metal(iii) complexes of macrobicyclic hexamine ligands and some of their derivatives provides evidence for the action of a variety of intermolecular forces within the lattices. Hydrogen bonding is universal and its forms depend strongly upon the oxidation state and the particular nature of the metal ion bound to the macrobicycle. The introduction of both aliphatic and aromatic substituents leads to lattices in which these substituents associate, although, in the case of aromatic substituents, this is not necessarily a consequence of ‘π-stacking’, despite the fact that the aromatic ring planes form parallel arrays. At least in the case of CoIII, stable enantiomers of the complexes can be obtained, and in {Δ-(+)589-[Co{(NH3)(CH3)sar}]}2Cl2(C6(CO2)6)·26H2O (sar = 3,6,10,13,16,19-hexa-azabicyclo[6.6.6]icosane), the benzene hexacarboxylate anion adopts a chiral conformation in the presence of the optically active cation.